TWI903029B - Optical adhesive tape - Google Patents

Abstract

The purpose of this invention is to provide an optical adhesive tape for use in spliced displays that arrange multiple image display devices in a tiled manner, ensuring that the gaps between the multiple image display devices remain inconspicuous even under the use environment, and maintaining transparency and a good appearance. The optical adhesive tape 10A of this invention has a laminated structure comprising a substrate 1 and an adhesive layer 2. The substrate 1 has a first surface 1a and a second surface 1b, and the adhesive layer 2 is located on the first surface 1a of the substrate 1. After heating the optical adhesive tape 10A at 60°C and 90% relative humidity for 500 hours, the average dimensional change rate in its width and mechanical directions is within ±0.15%. The adhesive layer 2 with an adhesive area of 1 ^cm² is bonded to the resin board, and the shear force when stretched in the shear direction at a tensile speed of 0.06 mm/min at 23°C is less than 20 N/ ^cm² .

Description

Optical adhesive tape

This invention relates to an optical adhesive tape. More specifically, it relates to an optical adhesive tape suitable for manufacturing a splicing display of multiple image display devices arranged in a splicing pattern.

With the advancement of high-definition technologies such as 4K and 8K, the demand for larger-screen image display devices is increasing daily. Furthermore, the use of large-screen image display devices for billboards and signs in outdoor and public facilities is also growing. However, manufacturing large-screen image display devices leads to decreased yield rates and increased manufacturing costs. To manufacture large-screen image display devices at a lower cost, a splicing display device arranging multiple image display devices in a tiled configuration has been discussed (e.g., Patent 1). Prior Art Documents Patent Documents

Patent Document 1: Japanese Patent Application Publication No. 2017-161634

Problems to be Solved by the Invention In the case of video wall displays, to make multiple display devices indistinct, the gaps between them must be narrowed (e.g., below 100µm). However, display devices shrink or expand under the influence of the environment, creating gaps or causing slight overlap, which makes the gaps more noticeable, reducing transparency and deteriorating the appearance. Furthermore, the adhesive layer used to bond the optical components that make up the display devices may not adapt to the shrinkage and expansion of the display devices, leading to protrusion or peeling at the ends, also causing a deterioration in appearance.

The present invention was created in view of the above circumstances. The purpose of the present invention is to provide an optical adhesive tape for splicing displays that arrange multiple image display devices in a splicing pattern, so that even in the use environment, the gaps between the multiple image display devices are not obvious, and transparency is maintained to maintain a good appearance.

The means for solving the problem namely, the first aspect of this invention provides an optical adhesive tape having a laminated structure comprising a substrate and an adhesive layer, the substrate having a first surface and a second surface, and the adhesive layer being located on the first surface of the substrate.

The optical adhesive tape of the first aspect of this invention, after being heated for 500 hours at 60°C and 90% relative humidity, exhibits an average dimensional change rate within ±0.15% in both the width and mechanical directions. This average dimensional change rate of within ±0.15% is ideal in the following ways: in a splicing display composed of multiple image display devices with the optical adhesive tape of the first aspect of this invention arranged in layers, it can suppress the shrinkage or expansion of the image display devices under the use environment, thereby reducing the noticeable gaps between the image display devices and maintaining a good appearance; and, with minimal shrinkage or expansion, transparency remains unchanged. In terms of suppressing the noticeable gaps between image display devices, minimizing shrinkage or expansion, and maintaining transparency, the aforementioned average dimensional change rate should preferably be within ±0.1%, or within ±0.05%.

Regarding the optical adhesive tape of the first aspect of this invention, when the aforementioned adhesive layer with an adhesive area of 1 ^cm² is bonded to a resin board and stretched in the shear direction at a tensile speed of 0.06 mm/min at 23°C, the shear force is 20 N/ ^cm² or less. In this specification, unless otherwise specified, "shear force" refers to "the shear force when the adhesive layer with an adhesive area of 1 ^cm² is bonded to a resin board and stretched in the shear direction at a tensile speed of 0.06 mm/min at 23°C".

The aforementioned adhesive layer having a shear force of 20 N/cm² or ^less is ideal in the following respects: the adhesive layer fully follows the contraction or expansion of the image display device with the optical adhesive tape of the first aspect of this invention in the usage environment, thereby suppressing bulging or peeling. Furthermore, it is also ideal in the following respects: when there are height differences in the shape of the adhered body, such as wiring, on the image display panel, the adhesive layer fully follows these height differences, thereby filling them without leaving air bubbles or other residues. In terms of suppressing the bulging or peeling of the optical adhesive tape of the first aspect of the present invention and being able to follow height differences, the shear force of the aforementioned adhesive layer should preferably be less than 15 N/cm ² , or less than 13 N/cm ² .

Let the optical adhesive tape of the first aspect of this invention be heated at 60°C and 90% relative humidity for 500 hours, and its average dimensional change rate in the width and mechanical directions be C [%]. Let the aforementioned adhesive layer of the optical adhesive tape be bonded to a 50µm thick PET film and then cut into 10cm squares to obtain a laminate. Let the maximum curling amount of the laminate after being heated at 60°C and 90% relative humidity for 500 hours be D [mm]. This should satisfy the following formula. |C×D|≦3 • Maximum Curl: With the curled protrusions of the aforementioned laminate placed on a horizontal plane with the curled surfaces facing down, the highest of the four corner curls is taken as the maximum curl D [mm]. The maximum curl measured with the aforementioned laminate placed on a horizontal plane with the PET film side facing down is +, and the maximum curl measured with the aforementioned laminate placed on a horizontal plane with the substrate side facing down is -.

The absolute value of the product of the aforementioned average dimensional change rate C [%] and the aforementioned maximum curling amount D [mm], |C×D|, being 3 or less, is ideal in the following respect: in a splicing display consisting of image display devices with optical adhesive tape of the first aspect of the present invention arranged in multiple laminated layers, it is not easy to visually perceive changes in the gaps between image display devices, and the image display devices can be precisely bonded to the thin film substrate. In terms of not easily visually perceiving changes in the gaps between image display devices and being able to precisely bond the image display devices to the thin film substrate, the aforementioned |C×D| is preferably 2.5 or less, more preferably 2.4 or less, and may also be 2.3 or less or 2.2 or less.

In the optical adhesive tape of the first aspect of this invention, the glass transition point (Tg) of the aforementioned substrate is preferably 60°C or higher. The aforementioned substrate having a glass transition point of 60°C or higher is ideal in that, in a video wall display consisting of multiple laminated layers of the optical adhesive tape of the first aspect of this invention, the mechanical properties of the video wall display are stable under operating conditions. From the viewpoint of the stability of the mechanical properties of the aforementioned video wall display, the glass transition point of the aforementioned substrate may also be 63°C or higher, or 65°C or higher.

In the optical adhesive tape of the first aspect of the present invention, the glass transition point (Tg) of the aforementioned adhesive layer is preferably below -10°C. The aforementioned adhesive layer having a Tg below -10°C is ideal in the following respects: it can maintain the stress relaxation of the aforementioned adhesive layer even in low-temperature environments, and the aforementioned adhesive layer fully follows the shrinkage or expansion of the image display device on which the optical adhesive tape of the first aspect of the present invention is applied in the usage environment, thereby suppressing bulging or peeling, and thus sufficiently ensuring adhesion to the substrate. In terms of suppressing the protrusion or peeling of the aforementioned image display device and ensuring good adhesion to the adhered object, the glass transition point of the aforementioned adhesive layer should preferably be below -15°C, or below -20°C.

After the optical adhesive tape of the first aspect of the present invention is humidified from 60°C and 30% relative humidity to 60°C and 60% relative humidity, its humidity expansion rate should preferably be 0.1% or less. The aforementioned humidity expansion rate of 0.1% or less is ideal in the following aspects: in a splicing display formed by an image display device with multiple layers of the optical adhesive tape of the first aspect of the present invention, the expansion of the image display device due to moisture absorption can be suppressed, and the gaps between the image display devices can be suppressed; and, the shrinkage or expansion is small, and the transparency can be maintained unchanged. From the perspective of suppressing the expansion of the aforementioned image display device due to moisture absorption, and considering that the contraction or expansion is minimal and the transparency can be maintained, the aforementioned humidity expansion rate should preferably be below 0.08%, or below 0.06%.

In the optical adhesive tape of the first aspect of this invention, the humidity expansion coefficient of the aforementioned substrate is preferably below 5× ^10⁻⁵ /%RH. The aforementioned substrate having a humidity expansion coefficient of below 5× ^10⁻⁵ /%RH is ideal in the following respects: the dimensional stability of the aforementioned substrate under humidity changes is improved; and in a splicing display formed by an image display device with multiple layers of the optical adhesive tape of the first aspect of this invention, shrinkage or expansion of the image display device under the usage environment can be suppressed, thus reducing noticeable gaps between image display devices and maintaining a good appearance; and, shrinkage or expansion is minimal, and transparency remains unchanged. Considering the dimensional stability of the aforementioned substrate, the minimal shrinkage or expansion, and the ability to maintain transparency, the humidity expansion coefficient of the aforementioned substrate should preferably be below 3× ^10⁻⁵ /%RH, or it can be below 2× ^10⁻⁵ /%RH.

In the optical adhesive tape of the first aspect of this invention, the second surface of the aforementioned substrate is preferably treated with anti-reflective and/or anti-glare treatment. This anti-reflective and/or anti-glare treatment of the second surface of the aforementioned substrate is ideal in preventing reflections caused by metal wirings or ITO wirings disposed on the substrate of the aforementioned image display device. Furthermore, in a video wall display consisting of multiple image display devices with the optical adhesive tape of the first aspect of this invention arranged in layers, it is also ideal in that it makes it difficult to discern the gaps between the image display devices.

In the optical adhesive tape of the first aspect of the present invention, the aforementioned adhesive layer is preferably an acrylic adhesive layer containing an acrylic polymer. This configuration is ideal for adjusting the aforementioned properties (especially shear force) of the adhesive layer.

Furthermore, a second aspect of the present invention provides an image display device, which laminates the optical adhesive tape of the first aspect of the present invention with an image display panel. A third aspect of the present invention provides a video wall display, which is composed of a plurality of image display devices of the second aspect of the present invention arranged together. The image display device of the second aspect of the present invention has the optical adhesive tape of the first aspect of the present invention in its laminated structure, thus suppressing shrinkage or expansion under the use environment. Furthermore, even if the image display device of the second aspect of the present invention shrinks or expands to a certain extent, the aforementioned adhesive layer can still adequately follow the shrinkage or expansion of the image display device, and is less prone to bulging or peeling. Therefore, for the splicing display of the third aspect of the invention, manufactured by arranging multiple image display devices representing the second aspect of the invention, the gaps between the image display devices are not noticeable in the usage environment, thus maintaining a good appearance. Furthermore, transparency remains unchanged.

Invention Effects By using the optical adhesive tape of this invention in the manufacture of a video wall display comprising multiple image display devices, the shrinkage or expansion of the image display devices under environmental conditions can be suppressed. Therefore, the gaps between the image display devices are not noticeable, maintaining a good appearance. Furthermore, transparency remains unchanged. Even when the image display devices expand or shrink to a certain extent, the adhesive layer is less prone to blistering or peeling, thus enabling the efficient manufacture of high-performance video wall displays.

The first aspect of this invention provides an optical adhesive tape having a laminated structure comprising a substrate and an adhesive layer. The substrate has a first side and a second side, and the adhesive layer is located on the first side of the substrate. In this specification, the optical adhesive tape of the first aspect of this invention is sometimes referred to as "the optical adhesive tape of the present invention." Furthermore, in this specification, the aforementioned substrate and adhesive layer constituting the optical adhesive tape of the present invention are sometimes referred to as "the substrate of the present invention" and "the adhesive layer of the present invention," respectively. Also, "adhesive tape" includes the meaning of "adhesive sheet." That is, the optical adhesive tape of the present invention can also be an adhesive sheet with a sheet-like form.

A second aspect of the present invention provides an image display device, which comprises the optical adhesive tape of the first aspect of the present invention and an image display panel. In this specification, the image display device of the second aspect of the present invention is sometimes referred to as the "image display device of the present invention". Furthermore, a third aspect of the present invention provides a video wall display, which comprises a plurality of image display devices of the present invention arranged together. In this specification, the video wall display of the third aspect of the present invention is sometimes referred to as the "video wall display of the present invention".

The following describes an embodiment of the optical adhesive tape of the present invention with the accompanying drawings, but the present invention is not limited thereto and is merely an example.

Figure 1 is a schematic diagram showing one embodiment of the optical adhesive tape of the present invention. (a) is a cross-sectional view, and (b) is a top view. In Figure 1(a), the optical adhesive tape 10A has a laminated structure comprising a substrate 1 and an adhesive layer 2. The substrate 1 has a first surface 1a and a second surface 1b, and the adhesive layer 2 is laminated on the first surface 1a of the substrate 1. In Figure 1(b), the width direction (TD) and mechanical direction (MD) of the optical adhesive tape 10A are determined corresponding to the width direction (TD) and mechanical direction (MD) of the substrate 1.

In Figure 2, the optical adhesive tape 10B has a laminated structure comprising a substrate 1 and an adhesive layer 2. The substrate 1 has a first surface 1a and a second surface 1b, and the adhesive layer 2 is laminated on the first surface 1a of the substrate 1. The second surface 1b of the substrate 1 is treated with an anti-reflective treatment and/or an anti-glare treatment 3.

Figure 3 is a schematic diagram (cross-sectional view) showing one embodiment of the image display device of the present invention. In Figure 3, the image display device 20 has an image display panel 4 laminated on the adhesive layer 2 of the optical adhesive tape 10B.

Figure 4 is a schematic diagram (stereoscopic view) showing one embodiment of the splicing display of the present invention. In Figure 4, the splicing display 30 is formed by arranging nine image display devices 20 (layer structure omitted) in a 3×3 configuration on a support substrate 31 in a spliced arrangement, with the image display devices 20 connected to each other by gaps 32. The components are described below.

<Optical Adhesive Tape> The term "optical" in this invention refers to its applicability for optical purposes, and more specifically, to its applicability in the manufacture of products incorporating optical components (optical products). Examples of optical products include input devices such as image display devices and touch panels, and it is suitable for manufacturing liquid crystal image display devices and self-emissive image display devices (e.g., organic EL (electroluminescent) image display devices, LED image display devices). In particular, this invention's optical adhesive tape is suitable for manufacturing spliced displays consisting of multiple image display devices arranged in a tiled configuration.

The optical adhesive tape of the present invention is not particularly limited in form as long as the first area layer of the substrate of the present invention has the adhesive layer of the present invention. For example, it can be a single-sided adhesive tape with only one side as the adhesive surface, or it can be a double-sided adhesive tape with both sides as the adhesive surface. Furthermore, when the optical adhesive tape of the present invention is a double-sided adhesive tape, it can have a form in which both adhesive surfaces are provided by the adhesive layer of the present invention, or it can have a form in which one adhesive surface is provided by the adhesive layer of the present invention, and the other adhesive surface is provided by an adhesive layer other than the adhesive layer of the present invention (other adhesive layers). When the optical adhesive tape of the present invention is used on the outermost surface of an optical product, it is preferably a single-sided adhesive tape, while when it is used to bond the adhered objects (optical components) to each other, it is preferably a double-sided adhesive tape.

In addition to the substrate and adhesive layer of this invention, the optical adhesive tape of this invention may also have other layers on the surface or between any layers without compromising the effect of this invention, such as a substrate other than the substrate of this invention, an adhesive layer other than the adhesive layer of this invention, an intermediate layer, a primer layer, an antistatic layer, a release element, a surface protective film, etc.

The optical adhesive tape of this invention exhibits an average dimensional change rate in both the width and mechanical directions within ±0.15% after being heated for 500 hours at 60°C and 90% relative humidity. The dimensional change rate in both the width and mechanical directions is the percentage (%) of dimensional change after heating for 500 hours at 60°C and 90% relative humidity, with the initial dimensions in each direction set at 100%. It is calculated using the following formula: Dimensional Change Rate (%) = [(Dimension after 500 hours of heating at 60°C and 90% relative humidity) - (Initial Dimension)] / (Initial Dimension) × 100

In the dimensional change rate (%), "+" indicates expansion and "-" indicates contraction. The average dimensional change rate in both the width and mechanical directions is the average of the dimensional change rates in the width and mechanical directions, calculated by the following formula: Average dimensional change rate (%) = [(Dimensional change rate in the width direction (%)) + (Dimensional change rate in the mechanical direction (%))] / 2

Furthermore, the dimensions of the optical adhesive tape of this invention are not particularly limited. Generally, they can be calculated by measuring the length of the ends in the width direction and the mechanical direction of the optical adhesive tape.

The aforementioned average dimensional change rate being within ±0.15% is ideal in the following respects: In the splicing display of the present invention, it can suppress the shrinkage or expansion of the image display devices under the use environment, thereby suppressing the noticeable gaps between image display devices and maintaining a good appearance; and, with minimal shrinkage or expansion, transparency can be maintained unchanged. In terms of suppressing the noticeable gaps between image display devices, minimizing shrinkage or expansion, and maintaining transparency unchanged, the aforementioned average dimensional change rate is preferably within ±0.1%, or may be within ±0.05%.

The aforementioned average dimensional change rate of the optical adhesive tape of the present invention can be specifically measured by the method described in the following embodiments. The aforementioned average dimensional change rate of the optical adhesive tape of the present invention can be adjusted by adjusting the type or thickness of the resin constituting the substrate of the present invention, the coefficient of hygroscopic expansion or glass transition point of the substrate, the type of resin constituting the adhesive layer of the present invention, monomer composition, crosslinking degree, elastic coefficient or glass transition point, etc.

Let the average dimensional change rate in the width and mechanical directions of the optical adhesive tape of this invention be C[%] after being heated at 60°C and 90% relative humidity for 500 hours. Let the adhesive layer of the aforementioned optical adhesive tape be bonded to a 50µm thick PET film and then cut into 10cm squares to obtain a laminate. Let the maximum curling amount of this laminate after being heated at 60°C and 90% relative humidity for 500 hours be D[mm]. This should satisfy the following formula. |C×D|≦3 • Maximum Curl: With the curled protrusions of the aforementioned laminate placed on a horizontal plane with the curled surfaces facing down, the highest of the four corner curls is taken as the maximum curl D [mm]. The maximum curl measured with the aforementioned laminate placed on a horizontal plane with the PET film side facing down is +, and the maximum curl measured with the aforementioned laminate placed on a horizontal plane with the substrate side facing down is -.

The absolute value of the product of the aforementioned average dimensional change rate C [%] and the aforementioned maximum curling amount D [mm], |C×D|, being 3 or less, is ideal in the following respects: in a splicing display composed of image display devices with multiple laminated layers covered by the optical adhesive tape of this invention, it is difficult to visually detect changes in the gaps between the image display devices, allowing for precise bonding of the image display devices to the thin-film substrate. Regarding the aspect of not easily visualizing changes in the gaps between the image display devices and achieving precise bonding of the image display devices to the thin-film substrate, the aforementioned |C×D| is preferably 2.5 or less, more preferably 2.4 or less, and can also be 2.3 or less, or 2.2 or less. The lower limit of the aforementioned |C×D| is not particularly limited, but lower is better, and can also be 0.001 or more.

The absolute value of the aforementioned maximum curl amount |D| [mm] is not particularly limited. However, for a video wall display consisting of multiple laminated image display devices with the optical adhesive tape of this invention, it is preferable to be 60 mm or less, more preferably 55 mm or less, and even more preferably 50 mm or less, in terms of accurately bonding the image display devices to the thin-film substrate. The lower limit of the aforementioned |D| is not particularly limited; the lower the better, but it can also be 0.1 mm or more.

The aforementioned |C×D| and |D| of the optical adhesive tape of this invention can be specifically measured by the method described in the following embodiments. The aforementioned |C×D| and |D| of the optical adhesive tape of this invention can be adjusted by adjusting the type or thickness of the resin constituting the substrate of this invention, the humidity expansion coefficient or glass transition point of the substrate, the type of resin constituting the adhesive layer of this invention, monomer composition, crosslinking degree, elastic coefficient or glass transition point, etc.

After humidifying the optical adhesive tape of this invention from 60°C and 30% relative humidity to 60°C and 60% relative humidity, its humidity expansion rate should preferably be 0.1% or less. This humidity expansion rate of 0.1% or less is ideal in the following ways: in the splicing display of this invention, it can suppress the expansion of the image display devices due to moisture absorption, thereby suppressing noticeable gaps between image display devices; and it minimizes shrinkage or expansion while maintaining transparency. From the perspective of suppressing the expansion of the image display devices due to moisture absorption, minimizing shrinkage or expansion, and maintaining transparency, the aforementioned humidity expansion rate should preferably be 0.08% or less, and may also be 0.06% or less. There is no particular limitation on the lower limit of the aforementioned humidity expansion rate; the lower the better, but it can also be above 0.0001%.

The aforementioned humidity expansion rate of the optical adhesive tape of the present invention can be specifically measured by the method described in the following embodiments. The aforementioned humidity expansion rate of the optical adhesive tape of the present invention can be adjusted by adjusting the type or thickness of the resin constituting the substrate of the present invention, the humidity expansion coefficient or glass transition point of the substrate, the type of resin constituting the adhesive layer of the present invention, monomer composition, crosslinking degree, elastic coefficient or glass transition point, etc.

After the optical adhesive tape of the present invention is heated at 60°C and 90% relative humidity for 500 hours, the ratio of its dimensional change rate in the mechanical direction to its dimensional change rate in the width direction (dimensional change rate in the mechanical direction / dimensional change rate in the width direction) is not particularly limited, but is preferably 0.5 or more and 2.0 or less. Within this range, such a ratio is ideal in the following ways: in the splicing display of the present invention, the difference between the dimensional change rates in the width direction and the mechanical direction of the image display device in the usage environment will be reduced, thereby suppressing noticeable gaps between image display devices and maintaining a good appearance; and, shrinkage or expansion is minimal, and transparency remains unchanged. In terms of minimizing the noticeable gaps between image display devices, minimizing shrinkage or expansion, and maintaining transparency, the aforementioned ratio should preferably be 0.6 or higher and 1.8 or lower, or 0.7 or higher and 1.5 or lower.

The aforementioned ratio (dimensional change rate in the mechanical direction / dimensional change rate in the width direction) of the optical adhesive tape of this invention can be adjusted by adjusting the type or thickness of the resin constituting the substrate of this invention, the coefficient of hygroscopic expansion or glass transition point of the substrate, the manufacturing conditions of the substrate (e.g., the temperature or speed of extrusion molding), the type of resin constituting the adhesive layer of this invention, monomer composition, crosslinking degree, elastic coefficient or glass transition point, etc.

The fog level of the optical adhesive tape of the present invention is not particularly limited, but it is preferably 5% or more. A fog level of 5% or more in the optical adhesive tape of the present invention is ideal in the following respects: it can prevent reflections caused by metal wiring or ITO wiring on the substrate of the image display panel disposed in the image display device of the present invention; and, in the splicing display of the present invention, it makes it difficult to see the gaps between image display devices; the fog level is preferably 6% or more, and may also be 7% or more. The upper limit of the fog level of the optical adhesive tape of the present invention is not particularly limited, but from the viewpoint of the visibility of the splicing display of the present invention, it is preferably 50% or less, and may also be 40% or less, or 30% or less.

The fog level of the optical adhesive tape of this invention can be measured according to JIS K 7136, specifically by the method described in the embodiments below. The fog level of the optical adhesive tape of this invention can be adjusted by the type or thickness of the resin constituting the substrate of this invention, the type or thickness of the resin constituting the adhesive layer of this invention, and by applying anti-reflective treatment and/or anti-glare treatment to the surface of the substrate.

The reflectivity of the optical adhesive tape of the present invention is not particularly limited, but preferably is 5% or less. The reflectivity of the optical adhesive tape of the present invention being 5% or less is ideal in the following respects: it can prevent reflections caused by metal wiring or ITO wiring on the substrate of the image display panel disposed in the image display device of the present invention; and in the splicing display of the present invention, it makes it difficult to see the gaps between image display devices; the reflectivity is preferably 3% or less, and may also be 1.5% or less. The lower limit of the reflectivity of the optical adhesive tape of the present invention is not particularly limited, and may also be 0.1% or more, or 0.3% or more.

The reflectivity of the optical adhesive tape of this invention can be measured according to JIS K7361-1, specifically by the method described in the embodiments below. The reflectivity of the optical adhesive tape of this invention can be adjusted by the type or thickness of the resin constituting the substrate of this invention, the type or thickness of the resin constituting the adhesive layer of this invention, and by applying anti-reflective treatment and/or anti-glare treatment to the surface of the substrate.

The total light transmittance of the optical adhesive tape of the present invention is not particularly limited, but it is preferably 85% or higher. A total light transmittance of 85% or higher in the optical adhesive tape of the present invention is ideal for achieving excellent transparency or excellent appearance in the image display device of the present invention; it is preferably 88% or higher, and can also be 90% or higher. The upper limit of the total light transmittance of the optical adhesive tape of the present invention is not particularly limited, and it can also be 95% or lower.

The total light transmittance of the optical adhesive tape of this invention can be measured according to JIS K7361-1. The total light transmittance of the optical adhesive tape of this invention can be adjusted by the type or thickness of the resin constituting the substrate of this invention, the type or thickness of the resin constituting the adhesive layer of this invention, and by applying anti-reflective treatment and/or anti-glare treatment to the surface of the substrate.

The thickness of the optical adhesive tape of this invention is not particularly limited. However, considering factors such as dimensional stability, strength, workability, and thinness, the thickness should be in the range of 10 to 500 µm, preferably 20 to 300 µm, and ideally 30 to 200 µm.

<Substrate> Materials constituting the substrate of this invention may include glass or plastic film. Examples of plastic films include: polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); cyclic olefin polymers (COP) (e.g., trade names "ARTON" (manufactured by JSR Corporation), "ZEONOR" (manufactured by ZEON Corporation)); acrylic resins such as polymethyl methacrylate (PMMA); polycarbonate (PC); cellulose triacetate (TAC); polyurethane; polyarylate; and poly... Plastic materials such as polyetheretherketone (PEEK), polyimide (PI), transparent polyimide (CPI), polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, and ethylene-propylene copolymer are preferred. These materials should be polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), cyclic olefin polymers (COP), polycarbonate (PC), polyetheretherketone (PEEK), and transparent polyimide (CPI) that exhibit excellent dimensional stability and are not easily shrunk. Furthermore, these plastic materials can be used alone or in combination of two or more. When the optical adhesive tape of this invention is attached to a substrate (such as an image display panel), the substrate is the portion that can be attached to the substrate together with the adhesive layer. The release liner that is peeled off during use (application) of this optical adhesive tape is not included in the "substrate".

The substrate of this invention has a thin film (substrate) shape with a first side and a second side. The width direction (TD) and mechanical direction (MD) of the substrate of this invention are specified in the manufacturing process of the substrate. For example, after the raw material resin is extruded, the direction in which the thin film extruded body travels is the mechanical direction (MD), and the width direction (TD) is the direction orthogonal to the mechanical direction.

If the substrate of this invention is an optical component constituting the aforementioned optical product, there are no particular limitations. It can be a covering component, a polarizing plate, a phase retardation plate, or various other optical thin films, and can preferably be used as a covering component. When the substrate of this invention is a covering component, the second surface may, for example, become the outermost surface of the aforementioned optical product.

The glass transition point (Tg) of the substrate of this invention is not particularly limited, but it is preferably above 60°C. A glass transition point of 60°C or higher in the substrate of this invention is ideal from the perspective of mechanical property stability in the operating environment of the image display device of this invention in the splicing display. From the viewpoint of the mechanical property stability of the image display device of this invention, the glass transition point of the aforementioned substrate may also be above 63°C or above 65°C. Furthermore, there is no particular upper limit to the glass transition point of the aforementioned substrate. From the perspective of simplifying the substrate forming process, the glass transition point of the aforementioned substrate is preferably below 350°C, but may also be below 250°C, below 200°C, below 140°C, below 130°C, or below 125°C.

The glass transition point (Tg) of the substrate of this invention can be measured according to JIS K 7121. The glass transition point (Tg) of the substrate of this invention can be adjusted by the type of resin constituting the substrate of this invention.

The coefficient of humidity expansion of the substrate of this invention is not particularly limited, but it is preferably below 5× ^10⁻⁵ /%RH. A substrate with a coefficient of humidity expansion of 5×10⁻⁵/%RH or below is ideal in the following respects: the dimensional stability of the substrate under humidity changes is improved; in the splicing display of this invention, it can suppress the shrinkage or expansion of the image display device under the operating environment, thereby reducing the noticeable gaps between image display devices and maintaining a good appearance; and, with minimal shrinkage or expansion, transparency remains unchanged. From the perspectives of dimensional stability, minimal shrinkage or expansion, and maintained transparency of the substrate of this invention, the humidity expansion coefficient of the substrate of this invention should preferably be below 3× ^10⁻⁵ /%RH, or below 2× ^10⁻⁵ /%RH. There is no particular limitation on the lower limit of the humidity expansion coefficient of the substrate of this invention; the lower the better, but it can also be above 0.001× ^10⁻⁵ /%RH.

The humidity expansion coefficient of the substrate of this invention can be specifically measured by the method described in the embodiments below. The humidity expansion coefficient of the substrate of this invention can be adjusted by the type of resin constituting the substrate of this invention or the conditions during substrate manufacturing (temperature, extrusion speed, etc.).

The haze of the substrate of this invention is not particularly limited, but it is preferably 5% or more. A haze of 5% or more in the substrate of this invention is ideal in the following ways: it prevents reflections caused by metal wiring or ITO wiring on the substrate of the image display panel disposed in the image display device of this invention; and it makes it difficult to see the gaps between image display devices in the splicing display of this invention. The haze is preferably 6% or more, and may also be 7% or more. The upper limit of the haze of the substrate of this invention is not particularly limited, but from the viewpoint of the visibility of the splicing display of this invention, it is preferably 50% or less, and may also be 40% or less, or 30% or less.

The fog level of the substrate of this invention can be measured in accordance with JIS K 7136. The fog level of the substrate of this invention can be adjusted by the type or thickness of the resin constituting the substrate of this invention, by applying anti-reflective treatment and/or anti-glare treatment to the surface of the substrate.

The reflectivity of the substrate of this invention is not particularly limited, but it is preferably 5% or less. A reflectivity of 5% or less in the substrate of this invention is ideal in the following ways: it prevents reflections caused by metal wiring or ITO wiring on the substrate of the image display panel disposed in the image display device of this invention; and in the splicing display of this invention, it makes it difficult to see the gaps between image display devices; the reflectivity is preferably 3% or less, and may also be 1.5% or less. The lower limit of the reflectivity of the substrate of this invention is not particularly limited, and may also be 0.1% or more, or 0.3% or more.

The reflectivity of the substrate of this invention can be measured in accordance with JIS K7361-1. The reflectivity of the substrate of this invention can be adjusted by the type or thickness of the resin constituting the substrate, the application of anti-reflective treatment and/or anti-glare treatment to the surface of the substrate, etc.

There are no particular limitations on the thickness of the substrate of this invention. However, considering factors such as dimensional stability, strength, workability, and thinness, a thickness of 10–500 µm is preferable, 20–300 µm is more suitable, and 30–200 µm is most suitable. There are no particular limitations on the refractive index of the substrate of this invention. For example, a range of 1.30–1.80 is preferable, with a range of 1.40–1.70 being more suitable.

The second surface of the substrate of this invention is preferably treated with a reflective surface and/or an anti-glare treatment. This configuration, where the second surface of the substrate of this invention is treated with a reflective surface and/or an anti-glare treatment, is ideal in preventing reflections caused by metal wiring or ITO wiring on the substrate of the image display device of this invention. Furthermore, it is also ideal in making it difficult to discern the gaps between image display devices in the splicing display of this invention.

The aforementioned anti-reflective treatment can use any known anti-reflective treatment without particular limitation, such as anti-reflective (AR) treatment.

The aforementioned anti-reflective (AR) treatment can be applied without particular limitation using known AR treatments. Specifically, it can be implemented by forming an optical thin film with strictly controlled thickness and refractive index, or by stacking two or more of the aforementioned optical thin films, on the second surface of the substrate of this invention. The aforementioned AR layer can utilize the interference effect of light to cancel out the opposite phases of the incident and reflected light, thereby exhibiting anti-reflective function. The wavelength region of visible light that can exhibit anti-reflective function is, for example, 380~780nm, and especially the wavelength region with high visual sensitivity is in the range of 450~650nm. It is advisable to design the AR layer in a way that minimizes the reflectivity of its center wavelength of 550nm.

The aforementioned AR layer is typically a multilayer antireflective layer with a structure consisting of two or five optical thin layers (thickness and refractive index of which are strictly controlled). By forming multiple layers of different refractive indices of predetermined thickness, the optical design freedom of the AR layer can be increased, the antireflective effect can be further improved, and the spectral reflectance characteristics can be made uniform (flat) in the visible light region. Since the aforementioned optical thin films require a high degree of thickness precision, the formation of each layer is generally carried out using dry methods such as vacuum evaporation, sputtering, and CVD.

Furthermore, the aforementioned AR layer can also be formed using an anti-reflective layer forming coating liquid. The aforementioned anti-reflective layer forming coating liquid may also contain, for example, resins, fluorine-containing additives, hollow particles, solid particles, and diluents, and these can be mixed together to manufacture the coating.

Examples of the aforementioned resins include thermosetting resins and free radiation-curing resins that can be cured by ultraviolet light or light. Commercially available thermosetting or ultraviolet-curing resins can also be used.

The aforementioned thermosetting or UV-curing resins can be, for example, curable compounds having at least one group selected from acrylate and methacrylate groups that can be cured by heat, light (ultraviolet light, etc.) or electron beams. Examples include: polysiloxane resins, polyester resins, polyether resins, epoxy resins, carbamate resins, alkyd resins, spiroaldehyde resins, polybutadiene resins, polythiol polyene resins, polyols, and other multifunctional compounds such as acrylate or methacrylate oligomers or prepolymers. One type can be used alone, or two or more can be used in combination.

The aforementioned resin may also use a reactive thinner having at least one group selected from acrylate and methacrylate groups. For example, the reactive thinner disclosed in Japanese Patent Application Publication No. 2008-88309 may be used, including monofunctional acrylates, monofunctional methacrylates, polyfunctional acrylates, and polyfunctional methacrylates. The aforementioned reactive thinner is preferably a trifunctional or higher acrylate or a trifunctional or higher methacrylate. This is because it can result in excellent hardness of the second surface of the substrate of the present invention. Other examples of the aforementioned reactive thinner include butylene glycol glycerol ether diacrylate, acrylates of isocyanuric acid, and methacrylates of isocyanuric acid. One or more of these may be used alone or in combination. The weight-average molecular weight of the aforementioned resin before curing can be, for example, 100 or more, 300 or more, 500 or more, 1,000 or more, or 2,000 or more, or it can be less than 100,000, 70,000 or less, 50,000 or less, 30,000 or less, or 10,000 or less. If the weight-average molecular weight before curing is high, although the hardness will decrease, it tends to be less prone to cracking after being bent. On the other hand, if the weight-average molecular weight before curing is low, the intermolecular crosslinking density will increase, and there is a tendency for the hardness to increase.

The aforementioned resins should preferably contain polyfunctional acrylates (e.g., neopentyl tert-acrylate).

To harden the aforementioned hardening resin, a hardener may be added, for example. The hardener is not particularly limited; for example, a known polymerization initiator (e.g., a thermal polymerization initiator, a photopolymerization initiator, etc.) may be used. The amount of the hardener added is not particularly limited; relative to 100 parts by weight of the aforementioned resin in the coating solution for forming the antireflective layer, it may be, for example, 0.5 parts by weight or more, 1.0 parts by weight or more, 1.5 parts by weight or more, 2.0 parts by weight or more, or 2.5 parts by weight or more, or it may be less than 15 parts by weight, less than 13 parts by weight, less than 10 parts by weight, less than 7 parts by weight, or less than 5 parts by weight.

The aforementioned fluorine-containing additives are not particularly limited; for example, they can be organic or inorganic compounds containing fluorine in their molecules. The aforementioned organic compounds are not particularly limited and can include, for example, fluorine-containing antifouling coatings, fluorine-containing acrylic compounds, and fluorine- and silicone-containing acrylic compounds. Specific examples of the aforementioned organic compounds include the trade name "KY-1203" manufactured by Shin-Etsu Chemical Industry Co., Ltd., and the trade name "MEGAFACE" manufactured by DIC Corporation. The aforementioned inorganic compounds are also not particularly limited. The amount of the aforementioned fluorine-containing additive is not particularly limited. For example, relative to the total weight of the solid components in the aforementioned antireflective layer forming coating liquid, the weight of the fluorine element in the aforementioned solid components may be 0.05% by weight or more, 0.1% by weight or more, 0.15% by weight or more, 0.20% by weight or more, or 0.25% by weight or more, or it may be less than 20% by weight, less than 15% by weight, less than 10% by weight, less than 5% by weight, or less than 3% by weight. Furthermore, for example, relative to 100 parts by weight of the aforementioned resin in the aforementioned antireflective layer forming coating liquid, the weight of the aforementioned fluorine-containing additive may be 0.05% by weight or more, 0.1% by weight or more, 0.15% by weight or more, 0.20% by weight or more, or 0.25% by weight or more, or it may be less than 20% by weight, less than 15% by weight, less than 10% by weight, less than 5% by weight, or less than 3% by weight.

The aforementioned hollow particles are not particularly limited, and can be, for example, silicon oxide particles, acrylic acid particles, acrylic-styrene copolymer particles, etc. Examples of silicon oxide particles include "THRULYA 5320" and "THRULYA 4320" manufactured by Nichih Catalyst Chemical Industry Co., Ltd. The weight-average particle size of the aforementioned hollow particles is not particularly limited, and can be, for example, 30nm or more, 40nm or more, 50nm or more, 60nm or more, or 70nm or more, or less than 150nm, 140nm or less, 130nm or less, 120nm or less, or 110nm or less. The shape of the aforementioned hollow particles is not particularly limited, and can be, for example, roughly spherical in shape like beads, or irregular in shape such as powder, but roughly spherical is preferable, especially roughly spherical particles with an aspect ratio of 1.5 or less, and spherical particles are most preferred. By adding the aforementioned hollow particles, the low refractive index and good anti-reflective properties of the anti-reflective layer can be achieved. The amount of the hollow particles added is not particularly limited, but relative to 100 parts by weight of the aforementioned resin in the coating solution for forming the anti-reflective layer, it can be, for example, 30 parts by weight or more, 50 parts by weight or more, 70 parts by weight or more, 90 parts by weight or more, or 100 parts by weight or more, or it can be less than 300 parts by weight, less than 270 parts by weight, less than 250 parts by weight, less than 200 parts by weight, or less than 180 parts by weight. From the perspective of reducing the refractive index of the anti-reflective layer, the amount of the hollow particles added should not be too small, while from the perspective of ensuring the mechanical properties of the anti-reflective layer, the amount of the hollow particles added should not be too large.

The aforementioned solid particles are not particularly limited, and may be, for example, silicon oxide particles, zirconium oxide particles, titanium-containing particles (e.g., titanium oxide particles). Examples of silicon oxide particles include those manufactured by Nissan Chemical Industries, Ltd. under the trade names "MEK-2140Z-AC," "MIBK-ST," and "IPA-ST." The weight-average particle size of the aforementioned solid particles is not particularly limited, and may be, for example, 5nm or more, 10nm or more, 15nm or more, 20nm or more, or 25nm or more, or less than 300nm, 250nm or less, 200nm or less, 150nm or less, or less than 100nm. The shape of the aforementioned solid particles is not particularly limited, and may be, for example, roughly spherical in shape like beads, or irregular in shape such as powder, but roughly spherical is preferable, especially roughly spherical particles with an aspect ratio of 1.5 or less, and most preferably spherical particles. By adding the aforementioned solid particles, such as the aforementioned fluorine-containing additive, they can easily and locally exist on the surface of the coating liquid for forming the aforementioned antireflective layer, thereby achieving excellent scratch resistance of the antireflective layer and realizing low refractive index and good antireflective properties. The amount of the aforementioned solid particles added is not particularly limited. Relative to 100 parts by weight of the aforementioned resin in the coating liquid for forming the aforementioned antireflective layer, it can be, for example, 5 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, 20 parts by weight or more, or 25 parts by weight or more, or it can be less than 150 parts by weight, less than 120 parts by weight, less than 100 parts by weight, or less than 80 parts by weight.

The aforementioned diluting solvent may also be, for example, a mixed solvent containing MIBK (methyl isobutyl ketone) and PMA (propylene glycol monomethyl ether acetate). The mixing ratio is not particularly limited; when the weight of MIBK is 100% by weight, the weight of PMA may be, for example, 20% or more by weight, 50% or more by weight, 100% or more by weight, 150% or more by weight, or 200% or more by weight, or it may be less than 400% by weight, less than 350% by weight, less than 300% by weight, or less than 250% by weight.

The aforementioned diluting solvent can also be, for example, a mixed solvent that further includes TBA (tertiary butanol) in addition to MIBK and PMA. The mixing ratio is not particularly limited in this case. When the weight of MIBK is 100% by weight, the weight of PMA can be, for example, 10% or more by weight, 30% or more by weight, 50% or more by weight, 80% or more by weight, or 100% or more by weight, or it can be less than 200% by weight, less than 180% by weight, less than 150% by weight, less than 130% by weight, or less than 110% by weight. Similarly, when the weight of MIBK is 100% by weight, the weight of TBA can be, for example, 10% or more by weight, 30% or more by weight, 50% or more by weight, 80% or more by weight, or 100% or more by weight, or it can be less than 200% by weight, less than 180% by weight, less than 150% by weight, less than 130% by weight, or less than 110% by weight.

The amount of the aforementioned diluent added is not particularly limited. For example, relative to the total weight of the coating liquid for forming the antireflective layer, the weight of its solid component can be set to be, for example, 0.1% by weight or more, 0.3% by weight or more, 0.5% by weight or more, 1.0% by weight or more, or 1.5% by weight or more. Alternatively, the weight of its solid component can be set to be 20% by weight or less, 15% by weight or less, 10% by weight or less, 5% by weight or less, or 3% by weight or less. From the perspective of ensuring coatability (wetting, leveling), the content of the aforementioned solid component should not be too high. From the perspective of preventing uneven drying, whitening, and other undesirable appearance caused by drying, the content of the aforementioned solid component should not be too low.

Next, the aforementioned antireflective layer forming coating liquid is applied to the second surface of the substrate of the present invention (the aforementioned coating step). There are no particular limitations on the coating method, and known coating methods such as spray coating, mold coating, spin coating, spray coating, gravure coating, roller coating, and stick coating can be used appropriately. The amount of the coating liquid used to form the antireflective layer is not particularly limited. It can be set such that the thickness of the formed antireflective layer is, for example, 0.1 μm or more, 0.3 μm or more, 0.5 μm or more, 1.0 μm or more, or 2.0 μm or more. Alternatively, it can be set such that the thickness of the formed antireflective layer is 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less.

Next, the previously applied anti-reflective layer is dried to form a coating film (the aforementioned coating film formation step). The drying temperature is not particularly limited, and can be, for example, in the range of 30 to 200°C. The aforementioned drying temperature can be, for example, above 40°C, above 50°C, above 60°C, above 70°C, above 80°C, above 90°C, or above 100°C, or below 190°C, below 180°C, below 170°C, below 160°C, below 150°C, below 140°C, below 135°C, below 130°C, below 120°C, or below 110°C. The drying time is not particularly limited, and can be, for example, above 30 seconds, above 40 seconds, above 50 seconds, or above 60 seconds, or below 150 seconds, below 130 seconds, below 110 seconds, or below 90 seconds.

Furthermore, the aforementioned coating can also be hardened (hardening step). This hardening can be carried out by, for example, heating or light irradiation. The light source is not particularly limited; for example, ultraviolet light can be used. The light source for the aforementioned light irradiation is also not particularly limited; for example, a high-pressure mercury lamp can be used. The irradiation dose of the energy source for the aforementioned ultraviolet curing should be 50~500 mJ/ ^cm² , calculated as the cumulative exposure dose at an ultraviolet wavelength of 365 nm. If the irradiation dose is 50 mJ/ ^cm² or higher, hardening will be easier and more thorough, and the hardness of the formed antireflective layer will be higher. Conversely, if it is below 500 mJ/ ^cm² , coloring of the formed antireflective layer can be prevented.

The aforementioned anti-glare (AG) treatment can be applied without particular limitation using known AG treatments, for example, it can be implemented by forming an anti-glare layer on the second surface of the substrate of the present invention. The aforementioned anti-glare layer can be made of known materials without limitation, and generally is formed as a layer in which inorganic or organic particles acting as anti-glare agents are dispersed in the resin.

The aforementioned anti-glare layer is not particularly limited. For example, it can be formed using an anti-glare layer forming material containing resin, particles, and a thixotropic agent, and the aforementioned particles and the aforementioned thixotropic agent are aggregated to form protrusions on the surface of the aforementioned anti-glare layer. With this structure, the anti-glare layer has excellent display properties that take into account both anti-glare and prevention of glare, and even though the anti-glare layer is formed by the aggregation of particles, it can still prevent the formation of protrusions on the surface of the anti-glare layer that would become appearance defects, thereby improving the yield of the product.

Examples of the aforementioned resins include thermosetting resins and free radiation-curing resins that can be cured by ultraviolet light or light. Commercially available thermosetting or ultraviolet-curing resins can also be used.

The aforementioned thermosetting or UV-curing resins can be, for example, curable compounds having at least one group selected from acrylate and methacrylate groups that can be cured by heat, light (ultraviolet light, etc.) or electron beams. Examples include: polysiloxane resins, polyester resins, polyether resins, epoxy resins, carbamate resins, alkyd resins, spiroaldehyde resins, polybutadiene resins, polythiol polyene resins, polyols, and other multifunctional compounds such as acrylate or methacrylate oligomers or prepolymers. One type can be used alone, or two or more can be used in combination.

The aforementioned resin may also use a reactive thinner having at least one group selected from acrylate and methacrylate groups. For example, the reactive thinner disclosed in Japanese Patent Application Publication No. 2008-88309 may be used, including monofunctional acrylates, monofunctional methacrylates, polyfunctional acrylates, and polyfunctional methacrylates. The aforementioned reactive thinner is preferably a trifunctional or higher acrylate or a trifunctional or higher methacrylate. This is because it can result in excellent hardness of the aforementioned anti-glare layer. Other examples of the aforementioned reactive thinner include butylene glycol glycerol ether diacrylate, acrylates of isocyanuric acid, and methacrylates of isocyanuric acid. One or more of these can be used alone or in combination.

The aforementioned resins preferably include carbamate acrylate resins, and more preferably copolymers of curing carbamate acrylate resins and polyfunctional acrylates (such as neopentyl terephthalol triacrylate).

The primary function of the particles used to form the aforementioned anti-glare layer is to create an uneven surface on the anti-glare layer to impart anti-glare properties and to control the fog value of the anti-glare layer. The fog value of the anti-glare layer can be designed by controlling the difference in refractive index between the aforementioned particles and the aforementioned resin. The aforementioned particles include, for example, inorganic particles and organic particles. There are no particular limitations on the aforementioned inorganic particles, and examples include: silicon oxide particles, titanium oxide particles, aluminum oxide particles, zinc oxide particles, tin oxide particles, zirconium oxide particles, calcium carbonate particles, barium sulfate particles, talc particles, kaolin particles, calcium sulfate particles, etc. Furthermore, there are no particular limitations on the aforementioned organic particles, and examples include: polymethyl methacrylate resin powder (PMMA particles), polysiloxane resin powder, polystyrene resin powder, polycarbonate resin powder, styrene acrylic resin powder, benzoguanamine resin powder, melamine resin powder, polyolefin resin powder, polyester resin powder, polyamide resin powder, polyimide resin powder, polyvinyl fluoride resin powder, etc. One type of these inorganic and organic particles may be used alone, or two or more may be used in combination.

The weight-average particle size (D) of the aforementioned particles is preferably in the range of 2.5 to 10 µm. By setting the weight-average particle size of the aforementioned particles within the aforementioned range, for example, the anti-glare performance is better and white fog can be prevented. The weight-average particle size of the aforementioned particles is preferably in the range of 3 to 7 µm. In addition, the weight-average particle size of the aforementioned particles can be determined by, for example, the Coulter count method. For example, using a particle size distribution measuring device utilizing the pore resistance method (trade name: Coulter Multisizer, manufactured by Beckman Coulter, Inc.), the resistance of the electrolyte equivalent to the particle volume when the particle passes through the aforementioned pore is measured, thereby determining the number and volume of the aforementioned particles and calculating the weight-average particle size.

The shape of the aforementioned particles is not particularly limited. For example, they can be roughly spherical like beads or irregular shapes such as powder, but they should be roughly spherical. Particles with an aspect ratio of less than 1.5 are more suitable, and spherical particles are the most suitable.

The ratio of the aforementioned particles in the anti-glare layer to 100 parts by weight of the aforementioned resin is preferably in the range of 0.2 to 12 parts by weight, more preferably in the range of 0.5 to 12 parts by weight, and even more preferably in the range of 1 to 7 parts by weight. By setting it to the aforementioned range, for example, the anti-glare performance is better and glare can be prevented.

The aforementioned anti-glare layer may also contain a thixotropic preform. By including the aforementioned thixotropic preform, the aggregation state of the aforementioned particles can be easily controlled. Examples of thixotropic preforms used to form the aforementioned anti-glare layer include organic clay, oxidized polyolefins, and modified urea.

To improve compatibility with the aforementioned resins, the organic clay should preferably be organically treated. Examples of organic clay include layered organic clay. The aforementioned organic clay can be homemade or commercially available products can be used. Examples of the aforementioned commercially available products include: LOOSENTIGHT SAN, LOOSENTIGHT STN, LOOSENTIGHT SEN, LOOSENTIGHT SPN, SOMASIF ME-100, SOMASIF MAE, SOMASIF MTE, SOMASIF MEE, SOMASIF MPE (trade names, all manufactured by Co-op Chemical Co., Ltd.); ESBEN, ESBEN C, ESBEN E, ESBEN W, ESBEN P, ESBEN WX, ESBEN N-400, ESBEN NX, ESBEN NX80, ESBEN NO12S, ESBEN NEZ, ESBEN NO12, ESBEN NE, ESBEN NZ, ESBEN NZ70, ORGANITE, ORGANITE D, ORGANITE T (trade names, all manufactured by HOJUN Co., Ltd.); KUNIPIA F, KUNIPIA G.KUNIPIA G4 (product name, all manufactured by KUNIMINE INDUSTRIES CO., LTD.); TIXOGEL VZ, CLAYTONE HT, CLAYTONE 40 (product name, all manufactured by Rockwood Additives Ltd.), etc.

The aforementioned oxidized polyolefins can be prepared at home or commercially available products can be used. Examples of such commercially available products include DISPARLON 4200-20 (trade name, manufactured by Kusumoto Chemical Co., Ltd.) and FLOWNON SA300 (trade name, manufactured by Kyoei Chemical Co., Ltd.).

The aforementioned modified urea is a reaction product of isocyanate monomers or their adducts with organic amines. The modified urea can be homemade or commercially available products can be used. Examples of commercially available products include BYK410 (manufactured by BYK-CHEMIE).

The aforementioned thixotropic accelerants may be used alone or in combination of two or more.

The height of the aforementioned convex portion from the average line of the thickness of the aforementioned anti-glare layer should preferably be less than 0.4 times the thickness of the anti-glare layer. It is more preferably in the range of 0.01 times or more and less than 0.4 times, and even more preferably in the range of 0.01 times or more and less than 0.3 times. Within this range, it is appropriate to prevent the formation of protrusions that would constitute appearance defects on the aforementioned convex portion. With the aforementioned anti-glare layer having a convex portion of the stated height, appearance defects are less likely to occur. Here, the aforementioned height from the average line can be measured by, for example, the method described in Japanese Patent Application Publication No. 2017-138620.

The ratio of the aforementioned thixotropic agent in the anti-glare layer to 100 parts by weight of the aforementioned resin should preferably be in the range of 0.1 to 5 parts by weight, and more preferably in the range of 0.2 to 4 parts by weight.

The thickness (d) of the aforementioned anti-glare layer is not particularly limited, but is preferably in the range of 3 to 12 µm. By setting the thickness (d) of the anti-glare layer within the aforementioned range, for example, curling of the optical adhesive tape of this invention can be prevented, thus avoiding problems such as poor conveyability and reduced productivity. Furthermore, when the aforementioned thickness (d) is within the aforementioned range, the weight average particle size (D) of the aforementioned particles is preferably in the range of 2.5 to 10 µm, as mentioned above. By combining the aforementioned thickness (d) of the anti-glare layer with the aforementioned weight average particle size (D), the anti-glare performance can be further improved. The thickness (d) of the aforementioned anti-glare layer is preferably in the range of 3 to 8 µm.

The relationship between the thickness (d) of the aforementioned anti-glare layer and the weight-average particle size (D) of the aforementioned particles should preferably be within the range of 0.3 ≤ D/d ≤ 0.9. By making it such a relationship, the anti-glare performance is better and can prevent glare, and an anti-glare layer without appearance defects can be made.

As described above, the optical adhesive tape of this invention forms a raised portion on the surface of the anti-glare layer by agglomerating the aforementioned particles and the aforementioned thixotropic excipient. In the agglomerated portion forming the raised portion, the aforementioned particles exist in a plurality of aggregated forms along the surface direction of the anti-glare layer. Thus, the raised portion has a gentle shape. By having the raised portion of the aforementioned shape, the anti-glare property can be maintained, while preventing glare and reducing the likelihood of appearance defects.

The surface shape of the aforementioned anti-glare layer can be arbitrarily designed by controlling the aggregation state of the particles contained in the anti-glare layer forming material. The aggregation state of the particles can be controlled, for example, by the material of the particles (e.g., the chemical modification state of the particle surface, affinity for solvents or resins, etc.), the type of resin (binder), or the combination of solvents. Here, the aggregation state of the particles can be controlled by the thixotropic agent contained in the aforementioned anti-glare layer forming material. As a result, the aggregation state of the particles can be as described above, and the aforementioned convex portion can be made into a smooth shape.

In the optical adhesive tape of the present invention, when the substrate of the present invention is formed of resin or the like, it is preferable to have a penetrating layer at the interface between the substrate of the present invention and the aforementioned anti-glare layer. The aforementioned penetrating layer is formed by the resin component contained in the forming material of the aforementioned anti-glare layer penetrating into the substrate of the present invention. The formation of a penetrating layer improves the adhesion between the substrate of the present invention and the aforementioned anti-glare layer, which is ideal. The thickness of the aforementioned penetrating layer is preferably in the range of 0.2 to 3 µm, and more preferably in the range of 0.5 to 2 µm. For example, when the substrate of the present invention is a polyester resin, and the resin contained in the aforementioned anti-glare layer is an acrylic resin, the aforementioned penetrating layer can be formed. The aforementioned penetrating layer can be confirmed, for example, by observing the cross-section of the optical adhesive tape of the present invention with a transmission electron microscope (TEM), and the thickness can be measured.

Even when applied to the optical adhesive tape of the present invention having the aforementioned penetrating layer, a smooth surface texture that balances anti-glare and prevention of glare can be easily formed. The more the penetrating layer adheres poorly to the substrate compared to the aforementioned anti-glare layer, the better the adhesion; therefore, it is advisable to form a thicker layer.

In the aforementioned anti-glare layer, it is preferable that there be no more than one appearance defect with a maximum diameter of 200µm or more per ^1m² . Ideally, there should be no such appearance defects.

The average tilt angle θa (°) of the uneven surface of the aforementioned anti-glare layer is preferably in the range of 0.1 to 5.0, more preferably in the range of 0.3 to 4.5, even more preferably in the range of 1.0 to 4.0, and especially preferably in the range of 1.6 to 4.0. Here, the aforementioned average tilt angle θa is defined by the following mathematical formula (1). The aforementioned average tilt angle θa is a value measured, for example, by the method described in Japanese Patent Application Publication No. 2017-138620. Average tilt angle θa = tan⁻¹Δa (1)

In the aforementioned mathematical formula (1), Δa, as shown in the following mathematical formula (2), is the sum of the differences (height h) between the apex of adjacent peaks and the lowest point of valleys in the reference length L of the roughness curve specified in JIS B 0601 (1994 edition), divided by the aforementioned reference length L. The aforementioned roughness curve is obtained by removing surface undulation components longer than a predetermined wavelength from the cross-sectional curve using a phase difference-compensated high-pass filter. Furthermore, the aforementioned cross-sectional curve refers to the outline revealed by the cut after the object surface is cut by a plane perpendicular to the object surface. Δa=(h1+h2+h3...+hn)/L (2)

If θa is within the above range, the anti-glare performance is even better and it can prevent glare.

When forming the aforementioned anti-glare layer, the prepared anti-glare layer forming material (coating liquid) should exhibit thixotropic properties, and the Ti value specified below should preferably be in the range of 1.3 to 3.5, more preferably in the range of 1.3 to 2.8. Ti value = β1/β2 Here, β1 is the viscosity measured using RheoStress 6000 manufactured by HAAKE Corporation at a shear rate of 20 (1/s), and β2 is the viscosity measured using RheoStress 6000 manufactured by HAAKE Corporation at a shear rate of 200 (1/s).

If the Ti value is less than 1.3, appearance defects are more likely to occur, and the anti-glare and white fog properties will deteriorate. Furthermore, if the Ti value is greater than 3.5, the aforementioned particles are less likely to aggregate and are more likely to be dispersed.

The manufacturing method of the aforementioned anti-glare layer is not particularly limited and can be manufactured by any method. For example, it can be manufactured by preparing an anti-glare layer forming material (coating liquid) comprising the aforementioned resin, the aforementioned particles, the aforementioned thixotropic agent, and solvent; applying the aforementioned anti-glare layer forming material (coating liquid) to the second surface of the substrate of the present invention to form a coating film; and allowing the aforementioned coating film to harden to form an anti-glare layer. Alternatively, a transfer method using a mold, or a method for imparting an uneven shape using appropriate methods such as sandblasting or embossing can also be used simultaneously.

There are no particular restrictions on the solvents used; various solvents can be used, either alone or in combination. An optimal solvent type or ratio exists depending on the composition of the resin, the type and content of the particles and the thixotropic agent. Examples of solvents include: alcohols such as methanol, ethanol, isopropanol, butanol, and 2-methoxyethanol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclopentanone; esters such as methyl acetate, ethyl acetate, and butyl acetate; ethers such as diisopropyl ether and propylene glycol monomethyl ether; glycols such as ethylene glycol and propylene glycol; cellulose compounds such as ethyl cellulose and butyl cellulose; aliphatic hydrocarbons such as hexane, heptane, and octane; and aromatic hydrocarbons such as benzene, toluene, and xylene.

When the substrate of this invention uses a polyester resin to form the penetrating layer, a solvent that is good for the polyester resin can be used. Examples of such solvents include ethyl acetate, methyl ethyl ketone, and cyclopentanone.

By appropriately selecting the aforementioned solvents, the thixotropic properties of the anti-glare layer forming material (coating liquid) can be well demonstrated using thixotropic excipients. For example, when using organic clay, toluene and xylene can be used alone or in combination; when using oxidized polyolefins, methyl ethyl ketone, ethyl acetate, and propylene glycol monomethyl ether can be used alone or in combination; when using modified urea, butyl acetate and methyl isobutyl ketone can be used alone or in combination.

Various leveling agents can be added to the aforementioned anti-glare layer forming material. These leveling agents, such as fluorinated or polysiloxane-based agents, can be used to prevent uneven application (uniform coating surface). The leveling agent can be appropriately selected depending on whether the surface of the anti-glare layer requires antifouling properties, or whether an anti-reflective layer (low refractive index layer) or a layer containing interlayer fillers is formed on the anti-glare layer. For example, by including the aforementioned thixotropic imparting agent, the coating liquid can exhibit thixotropy, thus reducing the likelihood of uneven application. Therefore, it has the advantage of expanding the selection of the aforementioned leveling agents.

For 100 parts by weight of the aforementioned resin, the amount of the aforementioned leveling agent mixed in is, for example, less than 5 parts by weight, preferably in the range of 0.01 to 5 parts by weight.

The aforementioned anti-glare layer forming material may also contain pigments, fillers, dispersants, plasticizers, UV absorbers, surfactants, antifouling agents, antioxidants, etc., as needed, without compromising performance. These additives may be used individually or in combination of two or more.

The aforementioned anti-glare layer forming material may also use, for example, a previously known photopolymerization initiator as disclosed in Japanese Patent Application Publication No. 2008-88309.

The method of applying the aforementioned anti-glare layer forming material to the second surface of the substrate of the present invention can be, for example, spray coating, molding, spin coating, spraying, gravure coating, roller coating, stick coating, etc.

The aforementioned anti-glare layer forming material is applied to form a coating film on the substrate of the present invention, and the aforementioned coating film is then hardened. It is preferable to dry the aforementioned coating film before the aforementioned hardening. The aforementioned drying may be, for example, natural drying, air drying by blowing air, heat drying, or a combination of these methods.

There are no particular restrictions on the curing method of the aforementioned anti-glare layer forming material coating, but ultraviolet curing is preferable. The irradiation dose from the energy source should preferably be 50~500 mJ/ ^cm² , calculated as the cumulative exposure dose at an ultraviolet wavelength of 365 nm. If the irradiation dose is 50 mJ/cm² or ^higher , the curing will be more thorough, and the hardness of the formed anti-glare layer will also be more sufficient. Furthermore, if it is below 500 mJ/ ^cm² , the coloring of the formed anti-glare layer can be prevented.

The aforementioned anti-glare layer can be formed on the second surface of the substrate of this invention using the above method. Alternatively, the anti-glare layer can also be formed using manufacturing methods other than those described above. The hardness of the aforementioned anti-glare layer, in terms of pencil hardness, will also affect the thickness of the layer, and it is preferable to have a hardness of 2H or higher.

The aforementioned anti-glare layer can also be a multilayer structure with two or more layers.

The aforementioned AR layer (low refractive index layer) can also be disposed on the anti-glare layer. For example, when optical adhesive tape is installed on an image display device, one of the main reasons for reduced image visibility is light reflection at the interface between the air and the anti-glare layer. The AR layer reduces surface reflection. In addition, the aforementioned anti-glare layer and anti-reflection layer can each be a multilayer structure with two or more layers.

Furthermore, in order to prevent contaminant adhesion and improve the removability of already adhered contaminants, it is advisable to deposit an anti-fouling layer formed of fluorine-containing silane compounds or fluorine-containing organic compounds on the aforementioned anti-reflective layer and/or anti-glare layer.

It is advisable to perform surface treatment on at least one of the present invention substrate and the aforementioned anti-glare layer. Surface treatment of the surface of the present invention substrate can further improve its adhesion to the aforementioned anti-glare layer. Furthermore, surface treatment of the surface of the aforementioned anti-glare layer can further improve its adhesion to the aforementioned AR layer.

To prevent the substrate of this invention from curling, the other side of the aforementioned anti-glare layer can also be treated with a solvent. Furthermore, to prevent curling, a transparent resin layer can also be formed on the other side of the aforementioned anti-glare layer.

<Adhesive Layer> The adhesive layer of this invention can be an adhesive layer without a substrate (substrate layer) or an adhesive layer with a substrate. Furthermore, in this specification, an adhesive layer without a substrate (substrate layer) is sometimes referred to as a "substrate-free adhesive layer," and an adhesive layer with a substrate is sometimes referred to as a "substrate-attached adhesive layer." As the aforementioned substrate-free adhesive layer, examples include a single-layer adhesive layer consisting solely of the adhesive layer of the present invention, or an adhesive layer consisting of the adhesive layer of the present invention and other adhesive layers (adhesive layers other than the adhesive layer of the present invention). Furthermore, the aforementioned substrate-attached adhesive layer may be an adhesive layer having the adhesive layer of the present invention on both sides of the substrate, or an adhesive layer having the adhesive layer of the present invention on one side of the substrate and other adhesive layers on the other side. The "substrate (substrate layer)" constituting the "adhesive layer with substrate" can be a plastic film identical to the substrate of this invention.

The shear force of the adhesive layer of this invention (the shear force when a 1 ^cm² adhesive area is bonded to a resin board and stretched in the shear direction at a tensile speed of 0.06 mm/min at 23°C) is 20 N/ ^cm² or less. The shear force of the adhesive layer of this invention being 20 N/ ^cm² or less is ideal in the following aspects: the adhesive layer of this invention fully follows the contraction or expansion of the image display device under the operating environment, thereby suppressing bulging or peeling. Furthermore, it is also ideal in the following aspects: when there are height differences in the shape of the adhered body, such as wiring, on the image display panel, the adhesive layer fully follows these height differences, thereby filling them without leaving air bubbles or other residues. In terms of suppressing bulging or peeling of the optical adhesive tape of the present invention and making it suitable for tracking height differences, the shear force of the adhesive layer of the present invention should preferably be 15 N/ ^cm² or less, or 13 N/ ^cm² or less. There is no particular limitation on the lower limit of the shear force of the adhesive layer of the present invention, but from the viewpoint of processability, such as preventing the adhesive layer from protruding from the ends when storing the optical adhesive tape of the present invention, it should preferably be 5 N/ ^cm² or more, or 7 N/ ^cm² or more.

The shear force of the adhesive layer of the present invention was measured by the shear force measurement of the embodiments described later. The shear force of the adhesive layer of the present invention can be adjusted by the composition of the adhesive composition used to form the adhesive layer of the present invention (e.g., the type or molecular weight of the base polymer, the amount used, the monomer composition, the type and amount of functional groups, the type and amount of crosslinking agents) or the curing conditions (heating conditions, radiation irradiation conditions), etc.

The glass transition point (Tg) of the adhesive layer of the present invention is preferably below -10°C. The Tg of the adhesive layer of the present invention being below -10°C is ideal in the following respects: it maintains the stress relaxation properties of the adhesive layer even in low-temperature environments, and the adhesive layer fully follows the contraction or expansion of the image display device under the usage environment of the present invention, thereby suppressing bulging or peeling, and thus ensuring sufficient adhesion to the substrate. Regarding the suppression of bulging or peeling of the image display device and the good adhesion to the substrate, the glass transition point of the adhesive layer of the present invention is below -15°C, or even below -20°C. The lower limit of the Tg of the adhesive layer of the present invention is not particularly limited. From the viewpoint of processability, such as to prevent the adhesive layer from protruding from the end when storing the optical adhesive tape of the present invention, it is preferable to be above -50°C, or above -40°C.

The glass transition point (Tg) of the adhesive layer of the present invention was determined by the dynamic viscoelasticity test of the embodiments described later. The glass transition point (Tg) of the adhesive layer of the present invention can be adjusted by the composition of the adhesive composition used to form the adhesive layer of the present invention (e.g., the type or molecular weight of the base polymer, the amount used, the monomer composition, the type and amount of functional groups, the type and amount of crosslinking agents) or the curing conditions (heating conditions, radiation irradiation conditions), etc.

The adhesive layer of this invention has no particular limitation on its storage modulus of elasticity at 70°C and 1Hz, but it is preferably below 80 kPa. The structure of the adhesive layer of this invention having a storage modulus of elasticity of 80 kPa or below at 70°C and 1Hz is ideal in the following aspects: the adhesive layer of this invention fully follows the contraction or expansion of the image display device under the operating environment, thereby suppressing bulging or peeling. Furthermore, it is also ideal in the following aspects: when there are height differences in the shape of the adhered body such as the image display panel due to wiring, the adhesive layer fully follows these height differences, thereby filling them without leaving air bubbles or other residues. In terms of suppressing bulging or peeling of the optical adhesive tape of the present invention and making it suitable for tracking height differences, the storage elastic modulus of the adhesive layer of the present invention at 70°C and 1Hz is preferably below 70 kPa, but can also be below 60 kPa or 50 kPa. There is no particular limitation on the lower limit of the storage elastic modulus of the adhesive layer of the present invention at 70°C and 1Hz. However, from the viewpoint of processability, such as preventing the adhesive layer from protruding from the ends when storing the optical adhesive tape of the present invention, it is preferable to have a value of 1 kPa or higher, and can also be 5 kPa or higher.

The adhesive layer of the present invention has no particular limitation on the loss tangent at 70°C and 1Hz, but preferably is 0.15 or higher. The adhesive layer of the present invention having a loss tangent of 0.15 or higher at 70°C and 1Hz is ideal in the following respects: the adhesive layer of the present invention fully follows the contraction or expansion of the image display device under the operating environment, thereby suppressing bulging or peeling. Furthermore, it is also ideal in the following respects: when there are height differences in the shape of the adhered body such as the image display panel due to wiring, the adhesive layer fully follows these height differences, thereby filling them without leaving air bubbles or other residues. In terms of suppressing bulging or peeling of the optical adhesive tape of the present invention and making it suitable for tracking height differences, the wear tangent of the adhesive layer of the present invention at 70°C and 1Hz should preferably be 0.2 or higher, or 0.25 or higher, or 0.3 or higher. There is no particular upper limit to the wear tangent of the adhesive layer of the present invention at 70°C and 1Hz. From the viewpoint of processability, such as preventing the adhesive layer from protruding from the ends when storing the optical adhesive tape of the present invention, it should preferably be 1 or less, or 0.8 or less.

The storage elastic modulus and loss tangent of the adhesive layer of the present invention at 70°C and 1Hz were determined by dynamic viscoelasticity measurement in the embodiments described later. The storage elastic modulus and loss tangent of the adhesive layer of the present invention at 70°C and 1Hz can be adjusted by the composition of the adhesive composition used to form the adhesive layer of the present invention (e.g., the type or molecular weight of the base polymer, the amount used, the monomer composition, the type and amount of functional groups, the type and amount of crosslinking agents) or the curing conditions (heating conditions, radiation irradiation conditions), etc.

The 300% tensile residual stress value of the adhesive layer of the present invention is not particularly limited, but it is preferably 10 N/ ^cm² or ^less . The composition of the adhesive layer of the present invention having a 300% tensile residual stress value of 10 N/cm² or less is ideal in the following respects: the adhesive layer of the present invention fully follows the contraction or expansion of the image display device under the usage environment, thereby suppressing bulging or peeling. Furthermore, it is also ideal in the following respects: when there are height differences in the shape of the adhered body such as the image display panel due to wiring, the adhesive layer fully follows these height differences, thereby filling them without leaving air bubbles or other residues. In terms of suppressing bulging or peeling of the optical adhesive tape of the present invention and making it suitable for tracking height differences, the 300% tensile residual stress value of the adhesive layer of the present invention is preferably 7 N/ ^cm² or less, and may also be 5 N/ ^cm² or less. There is no particular limitation on the lower limit of the 300% tensile residual stress value of the adhesive layer of the present invention. However, from the viewpoint of processability, such as preventing the adhesive layer from protruding from the ends when storing the optical adhesive tape of the present invention, it is preferably 1 N/ ^cm² or more, and may also be 1.5 N/ ^cm² or more.

The 300% tensile residual stress value of the adhesive layer of the present invention was determined by the 300% tensile residual stress value test of the embodiments described later. The 300% tensile residual stress value of the adhesive layer of the present invention can be adjusted by the composition of the adhesive composition used to form the adhesive layer of the present invention (e.g., the type or molecular weight of the base polymer, the amount used, the monomer composition, the type and amount of functional groups, the type and amount of crosslinking agents) or the curing conditions (heating conditions, radiation irradiation conditions), etc.

The recovery rate of the adhesive layer of this invention, calculated in the following shear test, is not particularly limited, but should preferably be 95% or less. <Shear Test> Measure the strain A (%) and strain B (%), and calculate the recovery rate (%) using the following formula. Strain A (%) is the strain after applying a torsional shear force of 500 Pa for 600 seconds at 60°C from the top and bottom of a 2 mm thick, 7.9 mm diameter disc-shaped adhesive layer. Strain B (%) is the strain after maintaining a shear force of 0 Pa for 1800 seconds. Recovery Rate (%) = (Strain A - Strain B) / Strain A × 100

In this manual, when "strain A", "strain B" and "recovery rate" are mentioned, unless otherwise specified, they refer to "strain A", "strain B" and "recovery rate" calculated in the above shear test.

The above-described "shear test" is explained with reference to the diagram. Figure 5 is a schematic diagram illustrating the shear test, where 40 represents the adhesive layer, and 41 and 42 represent the parallel plates. The adhesive layer 40 is a disc-shaped adhesive layer with a thickness of 2 mm and a diameter of 7.9 mm, and it is composed of the adhesive layer of this invention. The parallel plates 41 and 42 each have an upper surface and a bottom surface with a diameter of 7.9 mm, respectively, and are made of, for example, stainless steel (Figure 5(a)). The upper surface of the parallel plate 41 and the bottom surface of the parallel plate 42 are aligned with the bottom surface and upper surface of the adhesive layer 40 and brought into contact (Figure 5(b)). Next, the ambient temperature was set to 60°C, and a shear force F of 500 Pa in the torsional direction was applied to the adhesive layer 40 for 600 seconds (Fig. 5(c)). Then, the shear force of the parallel plates 41 and 42 was released, and the layer was placed under a shear force of 0 Pa for 1800 seconds (Fig. 5(d)). "Strain A" is the percentage change in the torsional direction at the time point (Fig. 5(c)) after applying a shear force F of 600 Pa to the outer periphery (100%) of the adhesive layer 40 initially (Fig. 5(b)). "Strain B" is the percentage change in the torsional direction at the time point (Fig. 5(d)) after applying a shear force F of 600 Pa to the outer periphery (100%) of the adhesive layer 40 initially (Fig. 5(b)) and then placing the layer under a shear force of 0 Pa for 1800 seconds. The recovery rate (%) can be calculated using the following formula: Recovery rate (%) = (Strain A - Strain B) / Strain A × 100

The adhesive layer of this invention has a recovery rate of 95% or less, which is ideal in the following aspects: the adhesive layer fully follows the shrinkage or expansion of the image display device under the usage environment, thereby suppressing bulging or peeling; and the transparency remains unchanged. Furthermore, it is also ideal in the following aspects: when there are height differences in the shape of the adhered body, such as wiring, on the image display panel, the adhesive layer fully follows these height differences, thereby filling them without leaving air bubbles or other residues. In terms of suppressing bulging or peeling of the optical adhesive tape of this invention, maintaining transparency, and following height differences, the recovery rate of the adhesive layer of this invention is preferably 94% or less, and can also be 93.5% or less. There is no particular limitation on the lower limit of the recovery rate of the adhesive layer of the present invention. From the viewpoint of processability, such as making it less likely for the adhesive layer to protrude from the end when storing the optical adhesive tape of the present invention, it is preferable to be 70% or more, or 80% or more, or 85% or more.

The strain A of the adhesive layer of the present invention is not particularly limited, but it is preferably 3% or more. A strain A of 3% or more in the adhesive layer of the present invention is ideal in the following respects: the adhesive layer fully follows the shrinkage or expansion of the image display device under the operating environment, thereby suppressing bulging or peeling. Furthermore, it is also ideal in the following respects: when there are height differences in the shape of the adhered body, such as wiring, on the image display panel, the adhesive layer fully follows these height differences, thereby filling them without leaving air bubbles or other residues. In terms of suppressing the protrusion or peeling of the optical adhesive tape of the present invention and making it able to follow height differences, the strain A of the adhesive layer of the present invention is preferably 4% or more, and may also be 5% or more. There is no particular upper limit to the strain A of the present invention. From the viewpoint of processability, such as making it less likely for the adhesive layer to protrude from the end when storing the optical adhesive tape of the present invention, and from the viewpoint that transparency can be maintained, it is preferably 25% or less, and may also be 20% or less or 15% or less.

The strain B of the adhesive layer of the present invention is not particularly limited, but it is preferably 0.1% or more. A strain B of 0.1% or more in the adhesive layer of the present invention is ideal in the following respects: the adhesive layer fully follows the shrinkage or expansion of the image display device under the operating environment of the present invention, thereby suppressing bulging or peeling. Furthermore, it is also ideal in the following respects: when there are height differences in the shape of the adhered body such as the image display panel due to wiring, the adhesive layer fully follows these height differences, thereby filling them without leaving air bubbles or other residues. In terms of suppressing the protrusion or peeling of the optical adhesive tape of the present invention and making it able to follow height differences, the strain B of the adhesive layer of the present invention should preferably be 0.2% or more, or 0.3% or more. There is no particular upper limit to the strain B of the present invention. From the viewpoint of processability, such as preventing the adhesive layer from protruding from the end when storing the optical adhesive tape of the present invention, and from the viewpoint of maintaining transparency, it should preferably be 10% or less, or 8% or less, or 5% or less.

The strain A, strain B, and recovery rate of the adhesive layer of the present invention are specifically determined by measuring the strain A, strain B, and recovery rate in the embodiments described later. The strain A, strain B, and recovery rate of the adhesive layer of the present invention can be adjusted by the composition of the adhesive composition used to form the adhesive layer of the present invention (e.g., the type or molecular weight of the base polymer, the amount used, the monomer composition, the type and amount of functional groups, the type and amount of crosslinking agents) or the curing conditions (heating conditions, radiation irradiation conditions), etc.

The adhesive used to form the adhesive layer of this invention is not particularly limited, and examples include: acrylic adhesives, rubber adhesives, vinyl alkyl ether adhesives, polysiloxane adhesives, polyester adhesives, polyamide adhesives, carbamate adhesives, fluorinated adhesives, and epoxy adhesives. However, considering transparency, adhesion, weather resistance, cost, and ease of design, the adhesive forming the adhesive layer is preferably an acrylic adhesive. That is, the adhesive layer of this invention is preferably an acrylic adhesive layer composed of an acrylic adhesive. The above-mentioned adhesives can be used alone or in combination of two or more.

The aforementioned acrylic adhesive layer contains an acrylic polymer as a base polymer. This acrylic polymer is a polymer that includes acrylic monomers (monomers having a (meth)acrylic group in the molecule) as monomeric components of the polymer. Preferably, the acrylic polymer is a polymer that includes alkyl (meth)acrylates as monomeric components of the polymer. Furthermore, the acrylic polymer can be used alone or in combination of two or more types.

The adhesive composition forming the adhesive layer of this invention can be in any form. For example, the adhesive composition can also be emulsion type, solvent type (solution type), active energy line curing type, thermal fusion type (thermal fusion type), etc. Among these, solvent type and active energy line curing type adhesive compositions are preferable from the perspective of manufacturability and ease of obtaining adhesive layers with excellent optical properties or appearance. In particular, active energy line curing type adhesive compositions are preferable from the viewpoint that the above-mentioned properties of the adhesive layer (especially shear force, glass transfer point, etc.) can be easily controlled within a predetermined range.

That is, the adhesive layer of the present invention is an acrylic adhesive layer containing an acrylic polymer as the base polymer, which is preferably formed by an active energy line curing type acrylic adhesive composition.

The aforementioned active energy lines can be categorized as, for example, alpha rays, beta rays, gamma rays, neutron rays, electron beams and other ionizing radiation, or ultraviolet rays, with ultraviolet rays being particularly preferred. That is, the aforementioned active energy line-cured adhesive composition is preferably an ultraviolet-cured adhesive composition.

The adhesive composition (acrylic adhesive composition) forming the aforementioned acrylic adhesive layer can be, for example, an acrylic adhesive composition in which an acrylic polymer is an essential component, or a mixture of monomers constituting the acrylic polymer (sometimes called a "monomer mixture"), or an acrylic adhesive composition in which a portion of the polymer is an essential component. Examples of the former include solvent-based acrylic adhesive compositions. Examples of the latter include active energy line curing type acrylic adhesive compositions. The term "monomer mixture" refers to a mixture containing monomer components constituting the polymer. Furthermore, the term "partial polymer" is sometimes also called a "prepolymer," meaning a composition in which one or more monomer components in the aforementioned monomer mixture have been partially polymerized.

The aforementioned acrylic polymers are polymers formed by using acrylic monomers as essential monomer components. Preferably, the aforementioned acrylic polymers are polymers formed by using alkyl (meth)acrylates as essential monomer components. That is, the aforementioned acrylic polymers preferably contain alkyl (meth)acrylates as constituent units. In this specification, "(meth)acrylate" means "acrylic acid" and/or "methacrylic acid" (either or both of "acrylic acid" and "methacrylic acid"), and so on. Furthermore, the aforementioned acrylic polymers are formed by using one or more monomer components.

The aforementioned alkyl methacrylates, which are essential monomeric components, are preferably alkyl methacrylates having linear or branched alkyl groups. Furthermore, alkyl methacrylates can be used alone or in combination of two or more.

Alkyl methacrylates having straight-chain or branched alkyl groups include, for example: methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, dibutyl methacrylate, tributyl methacrylate, pentyl methacrylate, isoamyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, and methacrylate. Nonyl acrylate, isononyl acrylate, decyl acrylate, isodecyl acrylate, undecyl acrylate, dodecyl acrylate, tridecyl acrylate, tetradecyl acrylate, decadecyl acrylate, hexadecyl acrylate, heptadecanyl acrylate, octadecyl acrylate (stearyl acrylate), isostearyl acrylate, nonadecanyl acrylate, eicosate acrylate, etc., which are alkyl methacrylates having a straight-chain or branched alkyl group with 1 to 20 carbon atoms. Among these, the aforementioned alkyl methacrylates having a straight-chain or branched alkyl group are preferably alkyl methacrylates having a straight-chain or branched alkyl group with 4 to 18 carbon atoms, and more preferably 2-ethylhexyl acrylate (2EHA), isostearyl acrylate (ISTA), lauryl acrylate (LA), and butyl acrylate (BA). Furthermore, the aforementioned alkyl (meth)acrylates having linear or branched alkyl groups can be used alone or in combination of two or more.

In the total monomer composition (100% by weight) of the above-mentioned acrylic polymer, the ratio of the above-mentioned alkyl methacrylate is not particularly limited, but it is preferably 50% by weight or more (e.g., 50 to 100% by weight), more preferably 53 to 90% by weight, and even more preferably 55 to 85% by weight.

Furthermore, in addition to the aforementioned acrylic polymer, the acrylic adhesive composition may also contain the aforementioned alkyl (meth)acrylate. When the acrylic adhesive composition contains alkyl (meth)acrylate in addition to the acrylic polymer, the content (admixture amount) of the alkyl (meth)acrylate relative to 100 parts by weight of the acrylic polymer is preferably 10 parts by weight or more (e.g., 10 to 100 parts by weight), more preferably 20 to 90 parts by weight, and even more preferably 30 to 80 parts by weight.

The aforementioned acrylic polymers may also contain the aforementioned (meth)acrylate alkyl esters and copolymeric monomers as monomeric components of the polymer. That is, the aforementioned acrylic polymers may also contain copolymeric monomers as constituent units. Furthermore, copolymeric monomers may be used alone or in combination of two or more types.

The aforementioned copolymer monomers are not particularly limited. However, from the perspective of easily controlling the various properties of the adhesive layer (especially shear force, glass transition point, etc.) within a predetermined range, suppressing bleaching in high-humidity environments, improving durability and bonding reliability, and considering compatibility with various additives such as UV absorbers and transparency, monomers with intramolecular nitrogen atoms and monomers with intramolecular hydroxyl groups are suitable. That is, the aforementioned acrylic polymers preferably include monomers with intramolecular nitrogen atoms as constituent units. Furthermore, the aforementioned acrylic polymers preferably include monomers with intramolecular hydroxyl groups as constituent units.

The monomers containing nitrogen atoms within the molecule described above are monomers (monomers) that have at least one nitrogen atom within one molecule. In this specification, the term "monomers containing nitrogen atoms within the molecule" is sometimes used as "monomers containing nitrogen atoms." There are no particular limitations on the aforementioned monomers containing nitrogen atoms; suitable examples include cyclic nitrogen monomers, (meth)acrylamides, etc. Furthermore, monomers containing nitrogen atoms can be used alone or in combination of two or more.

There are no particular limitations on the aforementioned cyclic nitrogen monomers that have polymerizable functional groups with unsaturated double bonds such as (meth)acrylic or vinyl groups and have a cyclic nitrogen structure. The aforementioned cyclic nitrogen structure preferably contains nitrogen atoms within the cyclic structure.

Examples of the aforementioned cyclic nitrogen monomers include N-vinylcyclic amides (endoamide-based vinyl monomers) and vinyl monomers with nitrogen-containing heterocycles.

Examples of the aforementioned N-vinylcyclic amides include those represented by formula (1) below. [Formula 1] (In equation (1), ^R1 represents a divalent organic group)

In the above formula (1), ^R1 is a divalent organic group, preferably a divalent saturated hydrocarbon or an unsaturated hydrocarbon, and more preferably a divalent saturated hydrocarbon (e.g., an alkyl group with 3 to 5 carbon atoms).

Examples of N-vinylcyclic amides represented by formula (1) above include: N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, N-vinyl-3-methylfolin, N-vinyl-2-caprolactone, N-vinyl-1,3-vinyl-2-one, N-vinyl-3,5-methylfolindione, etc.

Examples of vinyl monomers containing nitrogen-containing heterocycles include morphine rings, piperidine rings, pyrrolidine rings, and piperidine rings, as well as acrylic monomers containing nitrogen-containing heterocycles.

The aforementioned vinyl monomers containing nitrogen-containing heterocycles are not particularly limited, and examples include: (meth)acrylamide methyl methacrylate, N-vinylpiperidine, N-vinylpyrrole, N-vinylimidazolium, N-vinylpyridine, N-vinylamide methyl methacrylate, N-vinylpyrazole, vinylpyridine, vinylpyrimidine, vinylpyrazole, vinylisopyrazole, vinylthiazole, vinylisothiazole, vinylpyridine, (meth)acrylamide pyrrolidone, (meth)acrylamide pyrrolidone, (meth)acrylamide piperidine, etc.

Among the aforementioned vinyl monomers having nitrogen-containing heterocycles, acrylic monomers having nitrogen-containing heterocycles are preferred, particularly (meth)acrylamide molfolin, (meth)acrylamide pyrrolidine, and (meth)acrylamide piperidine.

Examples of the aforementioned (meth)acrylamides include (meth)acrylamide, N-alkyl (meth)acrylamide, and N,N-dialkyl (meth)acrylamide. Examples of the aforementioned N-alkyl (meth)acrylamides include N-ethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-n-butyl (meth)acrylamide, and N-octyl (meth)acrylamide. Furthermore, the aforementioned N-alkyl (meth)acrylamides also include (meth)acrylamides containing an amino group, such as dimethylaminoethyl (meth)acrylamide, diethylaminoethyl (meth)acrylamide, and dimethylaminopropyl (meth)acrylamide. Examples of the aforementioned N,N-dialkyl(meth)acrylamides include: N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, and N,N-di(tributyl)(meth)acrylamide.

Furthermore, the aforementioned (meth)acrylamides also include, for example, various N-hydroxyalkyl (meth)acrylamides. Examples of the aforementioned N-hydroxyalkyl (meth)acrylamides include: N-hydroxymethyl (meth)acrylamide, N-(2-hydroxyethyl) (meth)acrylamide, N-(2-hydroxypropyl) (meth)acrylamide, N-(1-hydroxypropyl) (meth)acrylamide, N-(3-hydroxypropyl) (meth)acrylamide, N-(2-hydroxybutyl) (meth)acrylamide, N-(3-hydroxybutyl) (meth)acrylamide, N-(4-hydroxybutyl) (meth)acrylamide, N-methyl-N-2-hydroxyethyl (meth)acrylamide, etc.

Furthermore, the aforementioned (meth)acrylamides also include, for example, various N-alkoxyalkyl (meth)acrylamides. Examples of the aforementioned N-alkoxyalkyl (meth)acrylamides include, for example, N-methoxymethyl (meth)acrylamide and N-butoxymethyl (meth)acrylamide.

Furthermore, nitrogen-containing monomers other than those containing cyclic nitrogen groups and (meth)acrylamides mentioned above can include, for example, amino-containing monomers, cyano-containing monomers, amide-containing monomers, and isocyanate-containing monomers. Examples of amino-containing monomers include ethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, and tributylaminoethyl (meth)acrylate. Examples of cyano-containing monomers include acrylonitrile and methacrylonitrile. The aforementioned imine-containing monomers include: maleimide monomers (e.g., N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide, etc.), and ikonimide monomers (e.g., N-methylikonimide, N-ethylikonimide, N-butylikonimide, N-octylikonimide, N...). -2-Ethylhexyl isocyanate, N-lauryl isocyanate, N-cyclohexyl isocyanate, etc.), succinimide monomers (e.g., N-(meth)acryloxymethylenesuccinimide, N-(meth)acryl-6-oxyhexamethylenesuccinimide, N-(meth)acryl-8-oxyoctamethylenesuccinimide, etc.). Examples of the above isocyanate-containing monomers include 2-(meth)acryloxyethyl isocyanate.

Among these, the nitrogen-containing monomers mentioned above are preferably cyclic nitrogen monomers, and more preferably N-vinylcyclic amides. More specifically, N-vinyl-2-pyrrolidone (NVP) is particularly preferred.

When the aforementioned acrylic polymer contains the aforementioned nitrogen-containing monomers as monomer components of the polymer, the proportion of the aforementioned nitrogen-containing monomers in the total monomer composition (100% by weight) of the aforementioned acrylic polymer is not particularly limited, but is preferably 1% by weight or more, more preferably 3% by weight or more, and even more preferably 5% by weight or more. If the above proportion is 1% by weight or more, it can suppress bleaching in high humidity environments and further improve durability, thereby obtaining high bonding reliability, which is ideal. Furthermore, from the perspectives of obtaining an adhesive layer with moderate softness, obtaining an adhesive layer with excellent transparency, and easily controlling the aforementioned properties of the adhesive layer (especially shear force, glass transition point, etc.) within a predetermined range, the upper limit of the ratio of the aforementioned nitrogen-containing monomers should preferably be 30% by weight or less, more preferably 25% by weight or less, and even more preferably 20% by weight or less.

The aforementioned monomers containing hydroxyl groups are monomers that have at least one hydroxyl group within one molecule. Suitable examples include monomers with polymerizable functional groups such as (meth)acrylic or vinyl unsaturated double bonds and also containing hydroxyl groups. However, the aforementioned monomers containing hydroxyl groups are assumed to exclude the aforementioned nitrogen-containing monomers. That is, in this specification, monomers that simultaneously possess both nitrogen atoms and hydroxyl groups within a molecule are included in the aforementioned "nitrogen-containing monomers." In this specification, the aforementioned "monomers containing hydroxyl groups within a molecule" are sometimes referred to as "hydroxyl-containing monomers." Furthermore, hydroxyl-containing monomers can be used alone or in combination of two or more.

Examples of hydroxyl-containing monomers include: 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, hydroxyoctyl methacrylate, hydroxydecyl methacrylate, hydroxylauryl methacrylate, and (4-hydroxymethylcyclohexyl) methacrylate, as well as other hydroxyl-containing methacrylates; vinyl alcohol; allyl alcohol, etc.

Among them, the hydroxyl-containing monomers mentioned above are preferably hydroxyl-containing (meth)acrylates, and more preferably 2-hydroxyethyl acrylate (HEA) or 4-hydroxybutyl acrylate (4HBA).

When the aforementioned acrylic polymer contains the aforementioned hydroxyl-containing monomers as monomeric components of the polymer, the proportion of the aforementioned hydroxyl-containing monomers in the total monomeric component (100% by weight) of the aforementioned acrylic polymer is not particularly limited. However, from the perspective of suppressing bleaching in high-humidity environments and improving durability and obtaining high adhesion reliability, it is preferable to be 0.5% by weight or more, more preferably 0.8% by weight or more, and even more preferably 1% by weight or more. Furthermore, from the viewpoint of easily controlling the aforementioned properties of the adhesive layer (especially shear force, glass transfer point, etc.) within a predetermined range, the upper limit of the proportion of the aforementioned hydroxyl-containing monomers is preferably 30% by weight or less, more preferably 25% by weight or less, and even more preferably 20% by weight or less.

Furthermore, to further enhance the aforementioned effects of hydroxyl-containing monomers, acrylic adhesive compositions may contain hydroxyl-containing monomers in addition to the aforementioned acrylic polymers. When acrylic adhesive compositions contain hydroxyl-containing monomers in addition to acrylic polymers, the content (admixture amount) of the hydroxyl-containing monomer relative to 100 parts by weight of the acrylic polymer is preferably 1 part by weight or more, more preferably 3 parts by weight or more, and even more preferably 5 parts by weight or more. If the above content is 5 parts by weight or more, whitening under high humidity environments can be suppressed and durability can be further improved, thereby obtaining higher bonding reliability, which is ideal. Furthermore, considering the ease of obtaining cohesive, adhesive, and adhesive reliability properties, and the ease of controlling the aforementioned characteristics of the adhesive layer (especially shear force, glass transition point, etc.) within a predetermined range, the upper limit of the content (admixture amount) of the aforementioned hydroxyl monomer is preferably 30 parts by weight or less, preferably 25 parts by weight or less, more preferably 20 parts by weight or less, and especially preferably 17 parts by weight or less.

In the total monomer composition (100 wt%) of the above-mentioned acrylic polymer, there is no particular limitation on the total ratio of the nitrogen-containing monomers and the hydroxyl-containing monomers. However, from the perspective of suppressing bleaching in high-humidity environments, improving durability, and obtaining high adhesion reliability, it is preferable to be 5 wt% or more, more preferably 10 wt% or more, and even more preferably 15 wt% or more. Furthermore, from the perspective of obtaining an adhesive layer with moderate flexibility, obtaining an adhesive layer with excellent transparency, and easily controlling the above-mentioned properties of the adhesive layer (especially shear strength, glass transfer point, etc.) within a predetermined range, the upper limit of the total ratio is preferably 50 wt% or less, more preferably 40 wt% or less, and even more preferably 35 wt% or less.

Copolymers other than nitrogen-containing and hydroxyl-containing monomers may include alicyclic monomers. There is no particular limitation on the alicyclic monomers described above, provided they have polymerizable functional groups with unsaturated double bonds such as (meth)acrylic or vinyl groups and possess an alicyclic structure. For example, alkyl (meth)acrylates containing cycloalkyl groups are included among the alicyclic monomers described above. Furthermore, alicyclic monomers may be used alone or in combination of two or more.

The alicyclic structure in the above-mentioned alicyclic monomers is a cyclic hydrocarbon structure, preferably with 5 or more carbon atoms, more preferably with 6 to 24 carbon atoms, more preferably with 6 to 15 carbon atoms, and especially preferably with 6 to 10 carbon atoms.

Examples of the aforementioned alicyclic monomers include: cyclopropyl methacrylate, cyclobutyl methacrylate, cyclopentyl methacrylate, cyclohexyl methacrylate, cycloheptyl methacrylate, cyclooctyl methacrylate, isocamphenyl methacrylate, dicyclopentyl methacrylate, HPMPA as shown in formula (2), TMA-2 as shown in formula (3), and HCPA as shown in formula (4), etc., which are all methacrylic monomers. Furthermore, in formula (4), the bond position between the cyclohexyl ring connected by the line and the structure within the parentheses is not particularly limited. Among these, cyclohexyl methacrylate and isocamphenyl methacrylate are particularly suitable.

[Chemical Formula 2] [Chemical Formula 3] [Chemical Formula 4]

When the aforementioned acrylic polymer contains the aforementioned alicyclic monomers as monomeric components of the polymer, the proportion of the alicyclic monomers in the total monomeric components (100% by weight) of the aforementioned acrylic polymer is not particularly limited. However, from the perspective of improving durability and obtaining high bonding reliability, it is preferable to be 10% by weight or more. Furthermore, from the perspective of obtaining an adhesive layer with moderate flexibility and easily controlling the aforementioned properties of the adhesive layer (especially shear force, glass transition point, etc.) within a predetermined range, the upper limit of the proportion of the alicyclic monomers is preferably 50% by weight or less, more preferably 40% by weight or less, and even more preferably 30% by weight or less.

Furthermore, copolymerizable monomers can be, for example, multifunctional monomers. Examples of such multifunctional monomers include: hexanediol di(meth)acrylate, butanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, neopentyl tetraethylene di(meth)acrylate, neopentyl tetraethylene tri(meth)acrylate, dinepentyl tetraethylene hexa(meth)acrylate, trihydroxymethylpropane tri(meth)acrylate, tetrahydroxymethylmethane tri(meth)acrylate, allyl methacrylate, ethylene methacrylate, divinylbenzene, epoxy acrylates, polyester acrylates, carbamate acrylates, etc. In addition, multifunctional monomers can be used alone or in combination of two or more.

When the aforementioned acrylic polymer contains the aforementioned multifunctional monomers as monomer components constituting the polymer, the proportion of the aforementioned multifunctional monomers in the total monomer component (100 wt%) constituting the aforementioned acrylic polymer is not particularly limited. From the viewpoint that it is easy to control the aforementioned properties of the adhesive layer (especially shear force, glass transition point, etc.) within a predetermined range, it is preferable to be 0.5 wt% or less (e.g., greater than 0 wt% and less than 0.5 wt%), and more preferably 0.2 wt% or less (e.g., greater than 0 wt% and less than 0.2 wt%).

Furthermore, in addition to the aforementioned acrylic polymers, the aforementioned multifunctional monomers can also be blended into acrylic adhesive compositions. When an acrylic adhesive composition contains multifunctional monomers in addition to acrylic polymers, from the viewpoint that it is easy to control the aforementioned properties of the adhesive layer (especially shear force, glass transition point, etc.) within a predetermined range, the content (blending amount) of the multifunctional monomer relative to 100 parts by weight of the acrylic polymer should preferably be 0.5 parts by weight or less (e.g., greater than 0 parts by weight but less than 0.5 parts by weight), and more preferably 0.2 parts by weight or less (e.g., greater than 0 parts by weight but less than 0.2 parts by weight).

Furthermore, the aforementioned copolymer monomers may include (meth)acrylate alkoxyalkyl esters. There are no particular limitations on the aforementioned (meth)acrylate alkoxyalkyl esters, and examples include: 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, 4-ethoxybutyl (meth)acrylate, etc. Among these, the aforementioned (meth)acrylate alkoxyalkyl esters are preferably alkoxyalkyl acrylates, and more preferably 2-methoxyethyl acrylate (MEA). In addition, the aforementioned (meth)acrylate alkoxyalkyl esters may be used alone or in combination of two or more.

When the above-mentioned acrylic polymer contains the above-mentioned (meth)acrylate alkoxyalkyl ester as a monomer component of the polymer, there is no particular limitation on the ratio of the above-mentioned (meth)acrylate alkoxyalkyl ester to the above-mentioned (meth)acrylate alkoxyalkyl ester, but the ratio of [the former:the latter] (by weight) should preferably be greater than 100:0 and less than 25:75, and more preferably greater than 100:0 and less than 50:50.

Other copolymerizable monomers mentioned above may include, for example, carboxyl-containing monomers, epoxy-containing monomers, sulfonic acid-containing monomers, phosphate-containing monomers, (meth)acrylates with aromatic hydrocarbon groups, vinyl esters, aromatic vinyl compounds, alkenes or dienes, vinyl ethers, vinyl chloride, etc. Examples of carboxyl-containing monomers include (meth)acrylate, itconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid, etc. Furthermore, the aforementioned carboxyl-containing monomers also include anhydride-containing monomers such as maleic anhydride and itconic anhydride. Examples of epoxy-containing monomers include glycidyl (meth)acrylate and methacrylic acid glycidyl (meth)acrylate. Examples of sulfonic acid-containing monomers include sodium vinylsulfonate, etc. Examples of phosphate-containing monomers include 2-hydroxyethyl acryl phosphate, etc. Examples of (meth)acrylates containing aromatic hydrocarbon groups include phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, and benzyl (meth)acrylate. Examples of vinyl esters include vinyl acetate and vinyl propionate. Examples of aromatic vinyl compounds include styrene and vinyltoluene. Examples of alkenes or dienes include ethylene, propylene, butadiene, isoprene, and isobutylene. Examples of vinyl ethers include vinyl alkyl ethers.

From the perspective of obtaining an acrylic adhesive layer with excellent corrosion resistance, the aforementioned acrylic polymers should preferably be free of acidic monomers or substantially free of acidic monomers as monomeric components of the polymer, and especially free of carboxyl monomers or substantially free of carboxyl monomers as monomeric components of the polymer. Examples of acidic monomers include carboxyl monomers, sulfonic acid monomers, and phosphate monomers. Specifically, those containing acidic monomers in the total monomer composition (100% by weight) of the aforementioned acrylic polymers may be substantially free of acidic monomers if the proportion is 0.05% by weight or less (preferably 0.01% by weight or less).

The content of the base polymer (especially acrylic polymer) in the adhesive layer of the present invention is not particularly limited, but it is preferably 50% or more (e.g., 50 to 100% by weight) relative to the total weight of the adhesive layer of the present invention, more preferably 80% or more (e.g., 80 to 100% by weight), and even more preferably 90% or more (e.g., 90 to 100% by weight).

The weight-average molecular weight (Mw) of the aforementioned acrylic polymers is 100,000 to 5,000,000, preferably 500,000 to 4,000,000, and more preferably 750,000 to 3,000,000. Acrylic polymers with a weight-average molecular weight of 100,000 or higher are preferred in terms of improving adhesion and resistance to foaming and peeling. Conversely, acrylic polymers with a weight-average molecular weight of 5,000,000 or lower are preferred in terms of easily improving adhesion and resistance to foaming and peeling.

The weight-average molecular weight (Mw) of the aforementioned acrylic polymers can be calculated by converting it to polystyrene using GPC. For example, a high-speed GPC apparatus, HPLC-8120GPC, manufactured by Tosoh Corporation, can be used for determination under the following conditions: Column: TSKgel SuperHZM-H/HZ4000/HZ3000/HZ2000 Soluble: Tetrahydrofuran Flow rate: 0.6 ml/min

The glass transition temperature (Tg) of the aforementioned acrylic polymers is not particularly limited, but is preferably -70 to -10°C, more preferably -65 to -15°C, and even more preferably -60 to -20°C. A glass transition temperature above -70°C for the acrylic polymers enhances cohesiveness and easily improves resistance to foaming and peeling, thus being ideal. Furthermore, an acrylic polymer composition with a glass transition temperature below -10°C is ideal in the following aspects: it maintains the stress relaxation properties of the aforementioned adhesive layer even in low-temperature environments, and the adhesive layer fully follows the shrinkage or expansion of the image display device under the operating environment of this invention, thereby suppressing bulging or peeling, and thus ensuring sufficient adhesion to the substrate.

The glass transition temperature (Tg) of the aforementioned acrylic polymer is expressed as the theoretical glass transition temperature using the following FOX formula: 1/Tg = W_₁/Tg_₁ + W_₂/Tg_₂ + ... + W _{_n}/Tg_{_n} In the above formula, Tg represents the glass transition temperature of the acrylic polymer (unit: K), Tg_{_i} represents the glass transition temperature after monomer i forms a homopolymer (unit: K), and Wi represents the weight fraction of monomer i in the total monomer content (i = 1, 2, ..., n). The Tg of the homopolymer constituting the aforementioned acrylic polymer monomers can be expressed using the following values. 2-Ethylhexyl acrylate -70℃; n-Hexyl acrylate -65℃; n-Octyl acrylate -65℃; Isononyl acrylate -60℃; n-Nonyl acrylate -58℃; n-Butyl acrylate -55℃; Ethyl acrylate -20℃; Lauryl acrylate 0℃; 2-Ethylhexyl methacrylate -10℃; Methyl acrylate 8℃; n-Butyl methacrylate 20℃; Methyl methacrylate 105℃; Acrylic acid 106℃; Methacryl methacrylate 228℃; Vinyl acetate 32℃; Styrene 100℃

Furthermore, for the Tg of homopolymers of monomers not described above, the values recorded in the "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) can be used. Moreover, for the Tg of homopolymers of monomers not described in the aforementioned literature, the values obtained by the above-described determination method (the peak temperature of tanδ obtained from the viscoelasticity test) can be used.

The adhesive layer of this invention contains the aforementioned acrylic polymer or other base polymer, which can be obtained by polymerizing the monomer components. The polymerization method is not particularly limited and can include, for example, solution polymerization, emulsion polymerization, block polymerization, and polymerization using active energy line irradiation (active energy line polymerization). Among these, considering the transparency and cost of the adhesive layer, solution polymerization and active energy line polymerization are preferable, with active energy line polymerization being more suitable.

Furthermore, various common solvents can be used during the polymerization of the aforementioned monomer components. Examples of such solvents include: esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; and ketones such as methyl ethyl ketone and methyl isobutyl ketone. In addition, solvents can be used alone or in combination of two or more.

When polymerizing the aforementioned monomer components, polymerization initiators such as thermal polymerization initiators or photopolymerization initiators (photoinitiators) can be used depending on the type of polymerization reaction. Furthermore, polymerization initiators can be used alone or in combination of two or more.

The aforementioned thermal polymerization initiators are not particularly limited and may include, for example, azo polymerization initiators, peroxide polymerization initiators (such as dibenzoyl peroxide, tributyl maleate peroxide, etc.), and redox polymerization initiators. Among these, the azo polymerization initiator disclosed in Japanese Patent Application Publication No. 2002-69411 is preferred. Examples of the aforementioned azo polymerization initiators include 2,2'-azobisisobutyronitrile (hereinafter sometimes referred to as AIBN), 2,2'-azobis-2-methylbutyronitrile (hereinafter sometimes referred to as AMBN), 2,2'-azobis(2-methylpropionic acid) dimethyl ester, and 4,4'-azobis-4-cyanovaleric acid. Furthermore, thermal polymerization initiators may be used alone or in combination of two or more.

When using the azo polymerization initiator in the polymerization of the acrylic polymer, there is no particular limitation on the amount of the azo polymerization initiator used. For example, relative to 100 parts by weight of the total monomer components constituting the acrylic polymer, it is preferably 0.05 parts by weight or more, more preferably 0.1 parts by weight or more, more preferably 0.5 parts by weight or less, and more preferably 0.3 parts by weight or less.

The aforementioned photopolymerization initiators are not particularly limited, and examples include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-keto alcohol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, diphenyl ketone-based photopolymerization initiators, acetal-based photopolymerization initiators, and 9-oxosulfuron-methyl-2-ethylhexylene ... These are examples of photopolymerization initiators. Other examples include acetophosphine oxide-based photopolymerization initiators and titanium thiocenene-based photopolymerization initiators. Examples of benzoin ether-based photopolymerization initiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethyl-1-one, and anisole methyl ether. Examples of acetophenone-based photopolymerization initiators include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, and 4-(tributyl)dichloroacetophenone. Examples of α-ketool-based photopolymerization initiators include 2-methyl-2-hydroxyphenylacetone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylprop-1-one. Examples of aromatic sulfonyl chloride-based photopolymerization initiators include 2-naphthalenesulfonyl chloride. Examples of photoactive oxime-based photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(O-ethoxycarbonyl)-oxime. Examples of benzoin-based photopolymerization initiators include benzoin. Examples of benzyl-based photopolymerization initiators include benzyl. Examples of the aforementioned diphenyl ketone-based photopolymerization initiators include diphenyl ketone, benzoic acid, 3,3'-dimethyl-4-methoxydiphenyl ketone, polyvinyl diphenyl ketone, and α-hydroxycyclohexylphenyl ketone. Examples of the aforementioned ketyl ketone-based photopolymerization initiators include benzyl dimethyl ketone. The aforementioned 9-oxosulfur... Examples of photopolymerization initiators include 9-oxosulfuron. 2-Chloro-9-oxysulfur 2-Methyl-9-oxosulfur 2,4-Dimethyl-9-oxosulfur Isopropyl 9-oxosulfur 2,4-Diisopropyl-9-oxosulfuron Dodecyl 9-oxosulfur Examples of acetylated phosphine oxide-based photopolymerization initiators include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide. Examples of titanium cyclopentadiene-based photopolymerization initiators include bis(n- ^5-2,4 -cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrolo-1-yl)-phenyl)titanium. Furthermore, photopolymerization initiators can be used alone or in combination of two or more.

When using the above-mentioned photopolymerization initiator during the polymerization of the above-mentioned acrylic polymer, there is no particular limitation on the amount of the photopolymerization initiator used. For example, relative to 100 parts by weight of the total monomer components constituting the above-mentioned acrylic polymer, it is preferably 0.01 parts by weight or more, more preferably 0.1 parts by weight or more, more preferably 3 parts by weight or less, and more preferably 1.5 parts by weight or less.

The aforementioned acrylic adhesive composition preferably contains both the aforementioned acrylic polymer and an acrylic oligomer with a weight average molecular weight of 1000-30000. The presence of an acrylic oligomer enhances the adhesion between the interface of the optical adhesive tape of this invention and the substrate, thus easily achieving strong adhesion and excellent resistance to foaming and peeling. Furthermore, in this specification, "acrylic oligomer with a weight average molecular weight of 1000-30000" is sometimes referred to simply as "acrylic oligomer."

The aforementioned acrylic oligomers may be suitable examples of acrylic polymers composed of (meth)acrylates with an intramolecular cyclic structure as essential monomer components, and more preferably, acrylic polymers composed of (meth)acrylates with an intramolecular cyclic structure and (meth)alkyl acrylates with straight-chain or branched alkyl groups as essential monomer components. That is, the aforementioned acrylic oligomers may be suitable examples of acrylic polymers containing (meth)acrylates with an intramolecular cyclic structure as monomer units, and more preferably, acrylic polymers containing (meth)acrylates with an intramolecular cyclic structure and (meth)alkyl acrylates with straight-chain or branched alkyl groups as monomer units.

The cyclic structure (ring) of the (meth)acrylate (hereinafter sometimes referred to as "cyclic (meth)acrylate") having a cyclic structure within the molecule (one molecule) can be either an aromatic ring or a non-aromatic ring, without particular limitation. Examples of the aromatic rings mentioned above include aromatic carbon rings [such as monocyclic carbon rings of benzene rings or condensed carbon rings of naphthalene rings] and various aromatic heterocycles. Examples of non-aromatic rings include: non-aromatic aliphatic rings (non-aromatic alicyclic rings) [e.g., cyclopentane rings, cyclohexane rings, cycloheptane rings, cyclooctane rings, etc.; cyclohexene rings, etc.], non-aromatic bridged rings [e.g., pinane, pinene, camphene, northoalkyl, northoalkylene, etc., dicyclic hydrocarbons; aliphatic hydrocarbons with three or more rings (bridged hydrocarbons), etc.], and non-aromatic heterocyclic rings [e.g., epoxane rings, cyclopentane rings, oxo-butane rings, etc.], etc.

Examples of the aforementioned tricyclic or multicyclic aliphatic hydrocarbons (bridged tricyclic or multicyclic hydrocarbons) include, for example, dicyclopentyl as shown in formula (5a), dicyclopentenyl as shown in formula (5b), adamantyl as shown in formula (5c), tricyclopentyl as shown in formula (5d), and tricyclopentenyl as shown in formula (5e). [Chemical Formula 5]

That is, the aforementioned cyclic (meth)acrylates can include, for example: cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, heptyl (meth)acrylate, cyclooctyl (meth)acrylate, and other cycloalkyl (meth)acrylates; isopentenyl (meth)acrylate and other (meth)acrylates having a dicyclic aliphatic hydrocarbon ring; dicyclopentyl (meth)acrylate, dicyclopentyloxyethyl (meth)acrylate, tricyclopentyl (meth)acrylate, 1-dacrylic (meth)acrylate Alkyl esters, 2-methyl-2-dalcenic esters of (meth)acrylate, 2-ethyl-2-dalcenic (meth)acrylate, and other (meth)acrylates containing tricyclic or more aliphatic hydrocarbon rings; aryl esters of (meth)acrylate such as phenyl methacrylate, aryloxyalkyl esters of (meth)acrylate such as phenoxyethyl methacrylate, and arylalkyl esters of (meth)acrylate such as benzyl methacrylate, and other (meth)acrylates containing aromatic rings, etc. Among these, the aforementioned cyclic (meth)acrylates are particularly preferably (meth)acrylates containing non-aromatic rings, more preferably cyclohexyl acrylate (CHA), cyclohexyl methacrylate (CHMA), dicyclopentyl acrylate (DCPA), and dicyclopentyl methacrylate (DCPMA), and even more preferably dicyclopentyl acrylate (DCPA) and dicyclopentyl methacrylate (DCPMA). In addition, cyclic (meth)acrylates can be used alone or in combination of two or more.

Among the aforementioned (meth)acrylates containing non-aromatic rings, those with three or more aliphatic hydrocarbon rings (especially bridged hydrocarbon rings) are particularly advantageous in terms of reducing the likelihood of inducing polymerization inhibition. Furthermore, using (meth)acrylates with unsaturated bonds, such as dicyclopentyl acrylates as shown in formula (5a), adamantyl acrylates as shown in formula (5c), or tricyclopentyl acrylates as shown in formula (5d), can further improve foaming resistance and significantly enhance adhesion to low-polarity substrates such as polyethylene or polypropylene.

In the total monomer units (the total amount of monomer components constituting the acrylic oligomer), the content (ratio) of the aforementioned cyclic (meth)acrylate is not particularly limited. However, relative to the total amount of monomer components constituting the acrylic oligomer (100 parts by weight), it is preferably 10-90 parts by weight, and more preferably 20-80 parts by weight. If the content of the aforementioned cyclic (meth)acrylate is 10 parts by weight or more, it easily improves the foaming and peeling resistance, which is ideal. Furthermore, if the content is 90 parts by weight or less, the adhesive layer will have appropriate softness, and adhesion or absorption capacity at different heights will be easily improved, which is also ideal.

Furthermore, examples of alkyl methacrylates having linear or branched alkyl groups as monomer units of acrylic oligomers include: methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, dibutyl methacrylate, terbutyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, and 2-methyl methacrylate. Alkyl methacrylates, including ethylhexyl acrylate, isooctyl methacrylate, nonyl methacrylate, isononyl methacrylate, decyl methacrylate, isodecyl methacrylate, undecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, decadecyl methacrylate, hexadecyl methacrylate, heptadecanyl methacrylate, octadecyl methacrylate, nonadecanyl methacrylate, and eicosyl methacrylate, have alkyl alkyl groups having 1 to 20 carbon atoms. Among these, methyl methacrylate (MMA) is preferred in terms of good compatibility with acrylic polymers. Furthermore, the above-mentioned alkyl methacrylates can be used alone or in combination of two or more.

In the total monomer units (the total amount of monomer components constituting the acrylic oligomer), the content of the aforementioned (meth)acrylate alkyl esters with linear or branched alkyl groups is not particularly limited. Regarding foaming and peeling resistance, the content relative to the total amount of monomer components constituting the acrylic oligomer (100 parts by weight) is preferably 10-90 parts by weight, more preferably 20-80 parts by weight, and even more preferably 20-60 parts by weight. A content of 10 parts by weight or more is particularly beneficial for easily improving adhesion to acrylic resins or polycarbonate substrates, which is ideal.

In addition to the aforementioned cyclic (meth)acrylates and alkyl (meth)acrylates having linear or branched alkyl groups, the monomer units of acrylic oligomers may also include monomers that can copolymerize with these monomers (copolymeric monomers). Furthermore, the content (ratio) of the aforementioned copolymeric monomers in the total monomer units (the total amount of monomer components constituting the acrylic oligomer) is not particularly limited, but it is preferable to be 49.9 parts by weight or less (e.g., 0 to 49.9 parts by weight) relative to the total amount of monomer components constituting the acrylic oligomer (100 parts by weight), and more preferably 30 parts by weight or less. Moreover, the copolymeric monomers may be used alone or in combination of two or more types.

Examples of copolymerizable monomers constituting acrylic oligomers include: alkoxyalkyl esters of (meth)acrylate [e.g., 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate, methoxytriethylene glycol methacrylate, 3-methoxypropyl methacrylate, 3-ethoxypropyl methacrylate, 4-methoxybutyl methacrylate, 4-ethoxybutyl methacrylate, etc.]; hydroxyl-containing monomers... (group) monomers [e.g., hydroxyalkyl methacrylates such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, vinyl alcohol, allyl alcohol, etc.]; amide-containing monomers [e.g., (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide] Amines, N-hydroxyethyl (meth)acrylamide, etc.; amine-containing monomers [e.g., ethyl (meth)acrylate, dimethyl methacrylate, tributyl methacrylate, etc.]; cyano-containing monomers [e.g., acrylonitrile, methacrylonitrile, etc.]; sulfonic acid-containing monomers [e.g., sodium vinylsulfonate, etc.]; phosphate-containing monomers [e.g., 2-hydroxyethyl acrylamide phosphate, etc.]; isocyanate-containing monomers [e.g., 2-methacryloyloxyethyl isocyanate, etc.]; amide-containing monomers [cyclohexylmaleimide, isopropylmaleimide, etc.], etc.

As described above, acrylic oligomers are preferably acrylic polymers comprising (meth)acrylates having an intramolecular cyclic structure and (meth)alkyl acrylates having linear or branched alkyl groups as monomer units. Preferably, they are acrylic polymers comprising cyclic (meth)acrylates and the aforementioned (meth)alkyl acrylates having linear or branched alkyl groups as monomer units. In the aforementioned acrylic polymers comprising cyclic (meth)acrylates and (meth)alkyl acrylates having linear or branched alkyl groups as monomer units, the amount of cyclic (meth)acrylates is not particularly limited relative to the total amount (100 parts by weight) of monomer components constituting the acrylic oligomer, but is preferably 10 to 90 parts by weight, more preferably 20 to 80 parts by weight. Furthermore, there is no particular limitation on the content of (meth)acrylate alkyl esters having straight-chain or branched alkyl groups, but it is preferably 10 to 90 parts by weight, more preferably 20 to 80 parts by weight, and even more preferably 20 to 60 parts by weight.

Furthermore, a particularly desirable specific composition of an acrylic oligomer may be exemplified by the following acrylic polymer, comprising at least one monomer selected from the group consisting of (1) dicyclopentyl acrylate, dicyclopentyl methacrylate, cyclohexyl acrylate and cyclohexyl methacrylate, and (2) methyl methacrylate as a monomer unit. In the aforementioned particularly desirable acrylic oligomer, the content of (1) dicyclopentyl acrylate, dicyclopentyl methacrylate, cyclohexyl acrylate and cyclohexyl methacrylate (when containing two or more, the total amount of these) in the total monomer units constituting the acrylic oligomer is preferably 30 to 70 parts by weight relative to the total amount of monomer components constituting the acrylic oligomer (100 parts by weight), and the content of (2) methyl methacrylate is preferably 30 to 70 parts by weight. However, the above-mentioned acrylic oligomers are not limited to the specific composition described above.

Acrylic oligomers can be obtained by polymerizing the aforementioned monomer components using well-known and conventional polymerization methods. Examples of polymerization methods for acrylic oligomers include solution polymerization, emulsion polymerization, bulk polymerization, and polymerization using active energy beam irradiation (active energy beam polymerization). Among these, bulk polymerization and solution polymerization are preferred, with solution polymerization being more suitable.

Various common solvents can also be used in the polymerization of acrylic oligomers. Examples of such solvents include: esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; and ketones such as methyl ethyl ketone and methyl isobutyl ketone. Furthermore, these solvents can be used alone or in combination of two or more.

Furthermore, known and commonly used polymerization initiators (such as thermal polymerization initiators or photopolymerization initiators) can be used during the polymerization of acrylic oligomers. In addition, polymerization initiators can be used alone or in combination of two or more.

Examples of thermal polymerization initiators include: 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile (AMBN), dimethyl 2,2'-azobis(2-methylpropionic acid), 4,4'-azobis-4-cyanopentanoic acid, 2,2'-azobis(4-methoxy-2,4-dimethylpentanonitrile), 2,2'-azobis(2,4-dimethylpentanonitrile), and 1,1'-azobis(2,4-dimethylpentanonitrile). Azo initiators such as cyclohexane-1-formonitrile and 2,2'-azobis(2,4,4-trimethylpentane); peroxide initiators such as benzoyl peroxide, tributyl peroxide, di-tributyl peroxide, tributyl peroxybenzoate, diisopropylphenyl peroxide, 1,1-bis(tributylperoxy)-3,3,5-trimethylcyclohexane, and 1,1-bis(tributylperoxy)cyclododecane. Furthermore, oil-soluble polymerization initiators are preferred for solution polymerization. Thermal polymerization initiators can be used alone or in combination of two or more.

There is no particular limitation on the amount of the above-mentioned thermal polymerization initiator used. For example, it is 0.1 to 15 parts by weight relative to 100 parts by weight of total monomer units of acrylic oligomer (the total amount of monomer components constituting acrylic oligomer).

Furthermore, there are no particular limitations on the aforementioned photopolymerization initiator; for example, it may be the same photopolymerization initiator used in the polymerization of the acrylic polymers listed above. There are no particular limitations on the amount of the aforementioned photopolymerization initiator used; it can be selected appropriately.

In the polymerization of the above-mentioned acrylic oligomers, chain transfer agents can also be used to adjust the molecular weight (specifically, to adjust the weight average molecular weight to 1,000 to 30,000). Examples of the aforementioned chain transfer agents include: 2-thioethanol, α-thioglycerol, 2,3-dithio-1-propanol, octylthiol, tri-nonylthiol, dodecylthiol (laurylthiol), tri-dodecylthiol, epioxypropylthiol, hydrothioacetic acid, methyl hydrothioacetate, ethyl hydrothioacetate, propyl hydrothioacetate, butyl hydrothioacetate, tri-butyl hydrothioacetate, 2-ethylhexyl hydrothioacetate, octyl hydrothioacetate, isooctyl hydrothioacetate, decyl hydrothioacetate, dodecyl hydrothioacetate, hydrothioacetate of ethylene glycol, hydrothioacetate of neopentyl glycol, hydrothioacetate of neopentyl tetraethanolol, α-methylstyrene dimer, etc. From the perspective of suppressing the whitening of the optical adhesive tape of this invention due to humidification, α-thioglycerol and methyl hydrothioacetate are preferred, with α-thioglycerol being particularly preferred. In addition, the chain transfer agent can be used alone or in combination of two or more.

The content (amount) of the chain transfer agent is not particularly limited. However, relative to 100 parts by weight of the total monomer units (the total amount of monomer components constituting the acrylic oligomer), it is preferably 0.1 to 20 parts by weight, more preferably 0.2 to 15 parts by weight, and even more preferably 0.3 to 10 parts by weight. By setting the content (amount) of the chain transfer agent within the above range, acrylic polymers with a weight average molecular weight controlled to 1000 to 30000 can be easily obtained.

The weight-average molecular weight (Mw) of the aforementioned acrylic oligomers is 1000~30000, preferably 1000~20000, more preferably 1500~10000, and even more preferably 2000~8000. Acrylic oligomers with a weight-average molecular weight of 1000 or higher can improve adhesion or maintain properties, thus improving foaming and peeling resistance. On the other hand, acrylic oligomers with a weight-average molecular weight of 30000 or lower tend to have better adhesion, thus improving foaming and peeling resistance.

The weight-average molecular weight (Mw) of the above-mentioned acrylic oligomers can be calculated by converting them to polystyrene using GPC. For example, a high-speed GPC apparatus, HPLC-8120GPC, manufactured by Tosoh Corporation, can be used for determination under the following conditions: Column: TSKgel SuperHZM-H/HZ4000/HZ3000/HZ2000 Soluble: Tetrahydrofuran Flow rate: 0.6 ml/min

The glass transition temperature (Tg) of the aforementioned acrylic oligomers is not particularly limited, but is preferably 20~300℃, more preferably 30~300℃, and even more preferably 40~300℃. Ideally, the glass transition temperature of the acrylic oligomers should be above 20℃ to easily improve foaming and peeling resistance. Conversely, ideally, if the glass transition temperature of the acrylic oligomers is below 300℃, the adhesive layer will possess suitable flexibility, easily achieving good adhesion or good gradient absorption, thus easily obtaining excellent bonding reliability.

The glass transition temperatures (Tg) of the aforementioned acrylic oligomers are theoretical values expressed in the FOX formula described above. The Tg of the homopolymers of the monomers constituting the aforementioned acrylic oligomers can be taken from the values recorded in Table 1 below. Furthermore, for the Tg of homopolymers of monomers not recorded in Table 1, the values recorded in the "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) can be used. Moreover, for the Tg of homopolymers of monomers not recorded in the aforementioned literature, the values obtained by the above-described determination method can be used (the peak temperature of tanδ obtained from the viscoelasticity test).

[Table 1] Furthermore, the copolymer of "DCPMA/MMA=60/40" in Table 1 refers to a copolymer of 60 parts by weight of DCPMA and 40 parts by weight of MMA.

When the aforementioned acrylic adhesive composition contains both acrylic polymers and acrylic oligomers, the content of the acrylic oligomers is not particularly limited, but is preferably 1 to 30 parts by weight, more preferably 2 to 20 parts by weight, and even more preferably 2 to 10 parts by weight, relative to 100 parts by weight of the aforementioned acrylic polymer. That is, the content of the acrylic oligomers in the aforementioned adhesive composition is not particularly limited, but is preferably 1 to 30 parts by weight, more preferably 2 to 20 parts by weight, and even more preferably 2 to 10 parts by weight, relative to 100 parts by weight of the total monomer units of the aforementioned acrylic polymer. The content of the acrylic oligomers in the aforementioned acrylic adhesive composition is not particularly limited; for example, it is preferably 1 to 30 parts by weight, more preferably 2 to 20 parts by weight, and even more preferably 2 to 10 parts by weight, relative to 100 parts by weight of the aforementioned monomer mixture. Ideally, an acrylic oligomer content of 1 part by weight or more readily yields excellent adhesion and resistance to foaming and peeling. Conversely, an acrylic oligomer content of 30 parts by weight or less readily yields excellent transparency and reliable adhesion. Furthermore, from the perspective of easily controlling the aforementioned properties of the adhesive layer (especially shear strength, glass transfer point, etc.) within a predetermined range, an acrylic oligomer content of 10 parts by weight or less, preferably 8 parts by weight or less, is preferable.

There are no particular limitations on the method for producing the above-mentioned adhesive composition containing acrylic polymers and acrylic oligomers. For example, acrylic oligomers, additives, etc., may be added to a mixture of monomer components constituting acrylic polymers or a portion of a mixture of monomer components constituting acrylic polymers (forming a mixture of monomers of acrylic polymers or a portion of the polymer), as needed, and then produced by mixing.

The adhesive layer of this invention is not particularly limited, but it is preferable to contain an ultraviolet (UVA) absorber. The presence of a UV absorber in the adhesive layer of this invention is ideal in terms of suppressing damage to the image display panel caused by ultraviolet radiation. Furthermore, the UV absorber can be used alone or in combination of two or more types.

The above-mentioned ultraviolet absorbers are not particularly limited, and examples include benzotriazole ultraviolet absorbers, hydroxyphenyltriazine ultraviolet absorbers, diphenyl ketone ultraviolet absorbers, salicylate ultraviolet absorbers, cyanoacrylate ultraviolet absorbers, and oxydiphenyl ketone ultraviolet absorbers.

Benzotriazole UV absorbers (benzotriazole compounds) include, for example: 2-(2-hydroxy-5-trimethylbutylphenyl)-2H-benzotriazole (trade name "TINUVIN PS", manufactured by BASF), phenylpropionic acid, and ester compounds of 3-(2H-benzotriazole-2-yl)-5-(1,1-dimethylethyl)-4-hydroxyl (C7-9 side-chain and straight-chain alkyl) (trade name "TINUVIN PS"). 384-2 (manufactured by BASF), a mixture of octyl 3-[3-triterpenoid-4-hydroxy-5-(5-chloro-2H-benzotriazol-2-yl)phenyl]propionate and 2-ethylhexyl-3-[3-triterpenoid-4-hydroxy-5-(5-chloro-2H-benzotriazol-2-yl)phenyl]propionate (trade name "TINUVIN 109", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (trade name "TINUVIN 900", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (trade name "TINUVIN"). 928 (manufactured by BASF), reaction product of methyl 3-(3-(2H-benzotriazol-2-yl)-5-tertiary butyl-4-hydroxyphenyl)propionate/polyethylene glycol 300 (trade name "TINUVIN 1130", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-p-cresol (trade name "TINUVIN P", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (trade name "TINUVIN 234", manufactured by BASF), 2-[5-chloro-2H-benzotriazol-2-yl]-4-methyl-6-(tertiary butyl)phenol (trade name "TINUVIN 1130"). 326 (manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (trade name "TINUVIN 328", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol (trade name "TINUVIN 329", manufactured by BASF), 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol] (trade name "TINUVIN 360", manufactured by BASF), the reaction product of methyl 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionate and polyethylene glycol 300 (trade name "TINUVIN") 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (trade name "TINUVIN 571", manufactured by BASF), 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimide-methyl)-5-methylphenyl]benzotriazole (trade name "Sumisorb 250", manufactured by Sumitomo Chemical Co., Ltd.), 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-tertiary octylphenol] (trade name "ADK STAB LA-31", manufactured by ADEKA Co., Ltd.), etc.

Hydroxyphenyl triterpenoid UV absorbers (hydroxyphenyl triterpenoid compounds) include, for example, the reaction product of 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triterpenoid-2-yl)-5-hydroxyphenyl with [(C10-C16 (mainly C12-C13)alkyloxy)methyl]ethylene oxide (trade name "TINUVIN"). 400 (manufactured by BASF), 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-tris(2-ethylhexyl)-5-[3-(dodecyloxy)-2-hydroxypropoxy]phenol), the reaction product of 2-(2,4-dihydroxyphenyl)-4,6-bis-(2,4-dimethylphenyl)-1,3,5-tris(2-ethylhexyl)-dehydroglyceric acid ester (trade name "TINUVIN 405", manufactured by BASF), 2,4-bis(2-hydroxy-4-butoxyphenyl)-6-(2,4-dibutoxyphenyl)-1,3,5-tris(2-ethylhexyl)-dehydroglyceric acid ester (trade name "TINUVIN 405"). 460”, manufactured by BASF, 2-(4,6-diphenyl-1,3,5-tris(2,6-diphenyl-1,3,5-tris(2,6-diphenyl-1,3,5-tris(2,6-diphenyl-1,3,5-tris(2,6-diphenyl-1,3,5-tris(2,6-diphenyl-1,3,5-tris(2,6-diphenyl-1,6-diphenyl-1,6-[(2,6-diphenyl-1 ... [Chemical Formula 6]

Examples of diphenyl ketone-based UV absorbers (diphenyl ketone compounds) and oxydiphenyl ketone-based UV absorbers (oxydiphenyl ketone compounds) include: 2,4-dihydroxydiphenyl ketone, 2-hydroxy-4-methoxydiphenyl ketone, 2-hydroxy-4-methoxydiphenyl ketone-5-sulfonic acid (anhydrous and trihydrate), 2-hydroxy-4-octyloxydiphenyl ketone, 4-dodecyloxy-2-hydroxydiphenyl ketone, 4-benzylmethyloxy-2-hydroxydiphenyl ketone, 2,2'-dihydroxy-4-methoxydiphenyl ketone (trade name "KEMISORB 111", manufactured by CHEMIPRO KASEI), and 2,2',4,4'-tetrahydroxydiphenyl ketone (trade name "SEESORB 106", manufactured by SHIPRO KASEI KAISHA). LTD. (manufactured), 2,2'-dihydroxy-4,4'-dimethoxydiphenyl ketone, etc.

Examples of salicylate-based ultraviolet absorbers (salicylate compounds) include: phenyl 2-acryloxybenzoate, phenyl 2-acryloxy-3-methylbenzoate, phenyl 2-acryloxy-4-methylbenzoate, phenyl 2-acryloxy-5-methylbenzoate, phenyl 2-acryloxy-3-methoxybenzoate, phenyl 2-hydroxybenzoate, phenyl 2-hydroxy-3-methylbenzoate, phenyl 2-hydroxy-4-methylbenzoate, phenyl 2-hydroxy-5-methylbenzoate, phenyl 2-hydroxy-3-methoxybenzoate, and 2,4-di-tertiary butylphenyl 3,5-di-tertiary butyl-4-hydroxybenzoate (trade name "TINUVIN 120", manufactured by BASF), etc.

Cyanoacrylate-based ultraviolet absorbers (cyanoacrylate compounds) include, for example, alkyl 2-cyanoacrylate, cycloalkyl 2-cyanoacrylate, alkoxyalkyl 2-cyanoacrylate, alkenyl 2-cyanoacrylate, alkynyl 2-cyanoacrylate, etc.

Considering its high UV absorption and enhanced corrosion resistance (especially UV resistance), excellent optical properties, ease of obtaining a highly transparent adhesive layer, and excellent light stability, the aforementioned UV absorber is preferably selected from at least one UV absorber formed from the group consisting of benzotriazole UV absorbers, diphenyl ketone UV absorbers, and hydroxyphenyltriazole UV absorbers, with benzotriazole UV absorbers and diphenyl ketone UV absorbers being more preferred. In particular, it is preferable to use a benzotriazole UV absorber with the following structure: a phenyl group having six or more carbon atoms and a hydroxyl group as a substituent is bonded to the nitrogen atom constituting the benzotriazole ring.

Furthermore, considering the need for higher UV absorption and improved corrosion resistance (especially UV resistance), the absorbance A of the aforementioned UV absorber should ideally be 0.5 or less, calculated as follows: Absorbance A: The absorbance measured by irradiating a 0.08% toluene solution of the aforementioned UV absorber with light at a wavelength of 400 nm.

When the adhesive layer of the present invention contains a UV absorber, the content of the aforementioned UV absorber in the adhesive layer (especially acrylic adhesive layers) is not particularly limited. However, from the perspective of further improving corrosion resistance (especially UV resistance), the content is preferably 0.01 parts by weight or more, more preferably 0.05 parts by weight or more, and more preferably 0.1 parts by weight or more, relative to 100 parts by weight of the base polymer. Furthermore, from the perspective of inhibiting yellowing caused by the addition of UV absorbers to the adhesive, obtaining excellent optical properties, high transparency, and excellent appearance properties, the upper limit of the content of the aforementioned UV absorber is preferably 10 parts by weight or less, more preferably 9 parts by weight or less, and more preferably 8 parts by weight or less, relative to 100 parts by weight of the base polymer.

The adhesive layer of this invention may also contain a light stabilizer. When the adhesive layer of this invention contains a light stabilizer, it is particularly advisable to contain the aforementioned ultraviolet absorber and light stabilizer together. The light stabilizer can capture free radicals generated by photo-oxidation, thus improving the adhesive layer's resistance to light (especially ultraviolet light). Furthermore, the light stabilizer can be used alone or in combination of two or more.

The aforementioned light stabilizers are not particularly limited and may include, for example, phenolic light stabilizers (phenolic compounds), phosphorus-based light stabilizers (phosphorus compounds), thioether-based light stabilizers (thioether compounds), and amine-based light stabilizers (amine compounds) (especially hindered amine stabilizers (hindered amine compounds)).

Examples of the aforementioned phenolic light stabilizers (phenolic compounds) include: 2,6-di-tertiary butyl-4-methylphenol, 4-hydroxymethyl-2,6-di-tertiary butylphenol, 2,6-di-tertiary butyl-4-ethylphenol, butylated hydroxyanisole, n-octadecyl 3-(4-hydroxy-3,5-di-tertiary butylphenyl)propionate, distearate (4-hydroxy-3-methyl-5-tertiary butyl)benzylmalonate, tocopherol, 2,2'-methylenebis(4-methyl-6-tertiary butylphenol), 2,2'-methylenebis(4-ethyl-6-tertiary butylphenol), and 4,4'-methylenebis(2,6-di-tertiary butylphenol). ), 4,4'-Butylidene bis(6-tertiary butyl-m-cresol), 4,4'-Thiobis(6-tertiary butyl-m-cresol), Styrified phenol, N,N'-Hexamethylene bis(3,5-di-tertiary butyl-4-hydroxyhydrocinnamoylamine), bis(3,5-di-tertiary butyl-4-hydroxybenzylphosphonate ethyl ester)calcium, 1,1,3-tris(2-methyl-4-hydroxy-5-tertiary butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tertiary butyl-4-hydroxybenzyl)benzene, tetrakis[3-(3,5-di-tertiary butyl-4-hydroxyphenyl)propoxymethyl]methane, 1,6-hexanediol-bis[3- (3,5-Di-tertiary butyl-4-hydroxyphenyl)propionate], 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol], 1,3,5-tris(4-tertiary butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanate, 1,3,5-tris(3,5-di-tertiary butyl-4-hydroxybenzyl)isocyanate, triethylene glycol-bis[3-(3-tertiary butyl-4-hydroxy-5-methylphenyl)propionate], 2,2'-ethylenediaminebis[ethyl 3-(3,5-di-tertiary butyl-4-hydroxyphenyl)propionate], 6-(4 -Hydroxyl-3,5-di-tert-butylaniline)-2,4-dioctylthio-1,3,5-tris(hydroxyl), bis[2-tert-butyl-4-methyl-6-(2-hydroxyl-3-tert-butyl-5-methylbenzyl)phenyl]terephthalate, 3,9-bis{2-[3-(3-tert-butyl-4-hydroxyl-5-methylphenyl)propoxy]-1,1-dimethylethyl}-2,4,8,10-tetraspiro[5.5]undecane, 3,9-bis{2-[3-(3,5-di-tert-butyl-4-hydroxyl)propoxy]-1,1-dimethylethyl}-2,4,8,10-tetraspiro[5.5]undecane, etc.

Phosphorus-based light stabilizers (phosphorus compounds) include, for example: trisodium nonylphenyl phosphite, trisodium (2,4-di-tertiary butylphenyl) phosphite, trisodium [2-tertiary butyl-4-(3-tertiary butyl-4-hydroxy-5-methylphenylthio)-5-methylphenyl] phosphite, tridecyl phosphite, octyl diphenyl phosphite, di(decyl)monophenyl phosphite, di(decayl)neopentyl tetraethylene diphosphite, distearate-based neopentyl tetraethylene diphosphite, di(nonylphenyl)neopentyl tetraethylene diphosphite, bis(2,4-di-tertiary butylphenyl)neopentyl tetraethylene diphosphite, bis(2,6-di-tertiary butyl-4-methylphenyl)neopentyl tetraethylene diphosphite, bis(2,4,6-tri-tertiary butylphenyl)monophenyl phosphite, etc. Neopentyl phosphite (tridecyl)-1,1,3-tris(2-methyl-4-hydroxy-5-tridecyl)butane-1,4'-butyrylbis(2-trimethyl-5-methylphenol)-1,1,3-tridecyl-1,1,3-tris(2-methyl-4-hydroxy-5-tridecyl-1,3-phenyl)butane-1,3-tris(2-methyl-4-hydroxy-5-tridecyl-1,3-phenyl)butane-1,3-tris(2,4-di-tridecyl-1,3-phenyl)-1,3-phenylene(2,4-di-tridecyl-1,3-phenylene(2,4,8,10-tridecyl-1,3-phenylene(2,4,8,10-tridecyl-1,3,2-dioxaphosphepin-6-yl)oxy-1,3-phenylene(2,4,8,10-tridecyl-1,3,2 ...

Thioether-based light stabilizers (thioether compounds) include, for example, dialkyl thiodipropionate compounds such as dilauryl thiodipropionate, dimyristyl, and distearate; and β-alkyl propionate compounds of polyols such as tetra[methylene(3-dodecylthio)propionate]methane.

Examples of amine-based light stabilizers (amine compounds) include: a polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (trade name "TINUVIN 622", manufactured by BASF); and the product of a 1:1 reaction of a polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol with N,N',N'',N'''-tetra-(4,6-bis-(butyl-(N-methyl-2,2,6,6-tetramethylpiperidine-4-yl)amino)-tris(2-yl)-4,7-diazadecane-1,10-diamine (trade name "TINUVIN"). 119” (manufactured by BASF), dibutylamine, 1,3-tris(N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl-1,6-hexamethylenediamine) and N-(2,2,6,6-tetramethyl-4-piperidinyl)butylamine condensate (trade name "TINUVIN 2020", manufactured by BASF), poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-tris(N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)imino]hexamethylene{(2,2,6,6-tetramethyl-4-piperidinyl)imino} (trade name "TINUVIN") 944 (manufactured by BASF), a mixture of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and methyl 1,2,2,6,6-pentamethyl-4-piperidinyl sebacate (trade name "TINUVIN 765", manufactured by BASF), bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (trade name "TINUVIN 770", manufactured by BASF), undecanoic acid bis(2,2,6,6-tetramethyl-1-(octoxy)-4-piperidinyl) ester, and the reaction product of 1,1-dimethylethyl hydrogen peroxide with octane (trade name "TINUVIN"). 123 (manufactured by BASF), bis(1,2,2,6,6-pentamethyl-4-piperidinyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butyl malonate (trade name "TINUVIN 144", manufactured by BASF), the reaction product of cyclohexane and N-butyl peroxide-2,2,6,6-tetramethyl-4-piperidinamine-2,4,6-trichloro-1,3,5-tris(2,2,6,6-tert-methyl-4-piperidinyl) sebacate and methyl 1,2,2,6,6-pentamethyl-4-piperidinyl sebacate (trade name "TINUVIN 152", manufactured by BASF), a mixture of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and methyl 1,2,2,6,6-pentamethyl-4-piperidinyl sebacate (trade name "TINUVIN 152"). 292” (manufactured by BASF), a mixed ester of 1,2,3,4-butanetetracarboxylic acid, 1,2,2,6,6-pentamethyl-4-piperidinol, and 3,9-bis(2-hydroxy-1,1-dimethylethyl)-2,4,8,10-tetraspiro[5.5]undecane (trade name "ADK STAB LA-63P", manufactured by ADEKA). Amine stabilizers are particularly suitable as hindered amine stabilizers.

When the adhesive layer of the present invention contains a light stabilizer, the content of the light stabilizer in the adhesive layer (especially acrylic adhesive layers) is not particularly limited. However, from the perspective of easily exhibiting light resistance, it is preferable to be 0.1 parts by weight or more, and more preferably 0.2 parts by weight or more, relative to 100 parts by weight of the base polymer. Furthermore, from the perspective of minimizing coloration caused by the light stabilizer itself and easily obtaining high transparency, as well as optical properties, the upper limit of the above content is preferably 5 parts by weight or less, and more preferably 3 parts by weight or less, relative to 100 parts by weight of the base polymer.

The formation of the adhesive layer in this invention is not particularly limited, and crosslinking agents can also be used. For example, acrylic polymers in an acrylic adhesive layer can be crosslinked to control the gel content. In addition, crosslinking agents can be used alone or in combination of two or more.

The aforementioned crosslinking agents are not particularly limited, and examples include: isocyanate-based crosslinking agents, epoxy-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, carbodiimide-based crosslinking agents, aziroxazoline-based crosslinking agents, azuril-based crosslinking agents, and amine-based crosslinking agents. Among these, isocyanate-based crosslinking agents and epoxy-based crosslinking agents are preferred, with isocyanate-based crosslinking agents being more suitable.

The aforementioned isocyanate crosslinkers (polyfunctional isocyanate compounds) include, for example: lower aliphatic polyisocyanates such as 1,2-epoxyethyl diisocyanate, 1,4-epoxybutyl diisocyanate, and 1,6-hexamethylene diisocyanate; alicyclic polyisocyanates such as cyclopentyl diisocyanate, cyclohexyl diisocyanate, isoflavone diisocyanate, hydrogenated toluene diisocyanate, and hydrogenated xylene diisocyanate; and aromatic polyisocyanates such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and epoxybutyl diisocyanate. Furthermore, examples of the aforementioned isocyanate crosslinking agents include: trihydroxypropane/toluene diisocyanate adduct (trade name "Coronate L", manufactured by Nippon Polyurethane Industry Co., Ltd.), trihydroxypropane/hexamethylene diisocyanate adduct (trade name "Coronate HL", manufactured by Nippon Polyurethane Industry Co., Ltd.), and trihydroxypropane/indomethacin diisocyanate adduct (trade name "TAKENATE D-110N", manufactured by Mitsui Chemicals Co., Ltd.), etc.

Examples of the aforementioned epoxy crosslinking agents (polyfunctional epoxy compounds) include: N,N,N',N'-tetracyclooxypropyl-monodiamine, dicyclooxypropylaniline, 1,3-bis(N,N-dicyclooxypropylaminomethyl)cyclohexane, 1,6-hexanediol dicyclooxypropyl ether, neopentyl glycol dicyclooxypropyl ether, ethylene glycol dicyclooxypropyl ether, propylene glycol dicyclooxypropyl ether, polyethylene glycol dicyclooxypropyl ether, polypropylene glycol dicyclooxypropyl ether, sorbitol. Polyepoxypropyl ether, glycerol polyepoxypropyl ether, neopentyl terephthalate polyepoxypropyl ether, polyglycerol polyepoxypropyl ether, sorbitan polyepoxypropyl ether, trihydroxymethylpropane polyepoxypropyl ether, diepoxypropyl adipate, diepoxypropyl phthalate, triepoxypropyl-tris(2-hydroxyethyl)triisocyanate, resorcinol diepoxypropyl ether, bisphenol-S-diepoxypropyl ether, and epoxy resins having two or more epoxy groups within their molecules are also examples. Furthermore, examples of the aforementioned epoxy crosslinking agents include commercially available products such as "TETRAD C" (manufactured by MITSUBISHI GAS CHEMICAL).

When a crosslinking agent is used to form the adhesive layer of the present invention, there is no particular limitation on the amount of the crosslinking agent used. From the perspective of obtaining sufficient adhesion reliability, it is preferable to be 0.001 parts by weight or more, and more preferably 0.01 parts by weight or more, relative to 100 parts by weight of the base polymer. Furthermore, from the perspective of obtaining appropriate softness in the adhesive layer to improve adhesion, and from the viewpoint that it is easy to control the above-mentioned properties of the adhesive layer (especially shear force, glass transition point, etc.) within a predetermined range, the upper limit of the above-mentioned amount used is preferably 10 parts by weight or less, and more preferably 5 parts by weight or less, relative to 100 parts by weight of the base polymer.

The adhesive layer of this invention (especially an acrylic adhesive layer) may contain a silane coupling agent to improve adhesion reliability under humid conditions, particularly to glass. Furthermore, the silane coupling agent can be used alone or in combination of two or more types. When the adhesive layer contains a silane coupling agent, adhesion under humid conditions is improved, especially to glass.

The aforementioned silane coupling agent is not particularly limited and may include, for example, γ-epoxypropoxypropyltrimethoxysilane, γ-epoxypropoxypropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-phenyl-aminopropyltrimethoxysilane, etc. Furthermore, commercially available products such as "KBM-403" (manufactured by Shin-Etsu Chemical Industry Co., Ltd.) may also be included. Among these, γ-epoxypropoxypropyltrimethoxysilane is preferred.

When the adhesive layer of the present invention contains a silane coupling agent, the content of the silane coupling agent in the adhesive layer (especially the acrylic adhesive layer) is not particularly limited, but it is preferably 0.01 parts by weight or more, and more preferably 0.02 parts by weight or more, relative to 100 parts by weight of the base polymer. Furthermore, the upper limit of the content of the silane coupling agent relative to 100 parts by weight of the base polymer is preferably 1 part by weight or less, and more preferably 0.5 parts by weight or less.

The adhesive layer of this invention may also contain an antistatic agent. Furthermore, the antistatic agent may be used alone or in combination of two or more types. If the adhesive layer contains an antistatic agent, it can prevent damage to the adhered substrate, such as the image display panel.

The aforementioned antistatic layers can be categorized as follows: quaternary ammonium salts, pyridinium salts, cationic antistatic agents with cationic functional groups such as primary, secondary, and tertiary amine groups, anionic antistatic agents with anionic functional groups such as sulfonates or sulfates, phosphonates, and phosphates, amphoteric antistatic agents such as alkyl betaine and its derivatives, imidazoline and its derivatives, and alanine and its derivatives, nonionic antistatic agents such as amino alcohols and their derivatives, glycerol and its derivatives, and polyethylene glycol and its derivatives, as well as ionic conductive polymers obtained by monomer polymerization or copolymerization of the aforementioned cationic, anionic, and amphoteric ionic conductive groups.

When the adhesive layer of the present invention contains an antistatic agent, the content of the antistatic agent in the adhesive layer of the present invention is not particularly limited, but it is preferably 0.01 parts by weight or more, and more preferably 0.02 parts by weight or more, relative to 100 parts by weight of the base polymer. Furthermore, the upper limit of the content of the antistatic agent relative to 100 parts by weight of the base polymer is preferably 1 part by weight or less, and more preferably 0.5 parts by weight or less.

The adhesive layer of this invention may also contain a colorant. Furthermore, the colorant may be used alone or in combination of two or more types. If the adhesive layer contains a colorant, it is ideal in preventing reflections caused by metal wirings or ITO wirings disposed on the substrate of the image display device of this invention.

If the aforementioned colorant is soluble or dispersible in the adhesive layer of this invention, it can be either a dye or a pigment. Dyes are ideal because they can achieve low fog even with small amounts added, and like pigments, they distribute evenly without settling. Pigments are also ideal because they maintain high color rendering even with small amounts added. When using pigments as colorants, they should preferably be low or non-conductive. Furthermore, when using dyes, they should preferably be used in conjunction with the aforementioned light stabilizers.

The aforementioned colorants can be used without limitation as long as they can absorb visible light (wavelength 400-700nm). They can also be used if they exhibit transmittance of ultraviolet light (wavelength 330-400nm) or absorb ultraviolet light, but they should ideally absorb visible light and have high ultraviolet transmittance. That is, the aforementioned colorants should ideally have a maximum transmittance at wavelengths of 330-400nm greater than the maximum transmittance at wavelengths of 400-700nm. Furthermore, the aforementioned colorants should also ideally have an average transmittance at wavelengths of 330-400nm greater than the average transmittance at wavelengths of 400-700nm. The transmittance of the colorant is determined by diluting it with a suitable solvent or dispersion medium such as tetrahydrofuran (THF) (an organic solvent with low absorption in the wavelength range of 330~700nm) to a solution or dispersion with a transmittance of about 50~60% at a wavelength of 400nm.

Carbon black or titanium black, commonly used as black colorants, absorb more ultraviolet light than visible light (ultraviolet transmittance is less than visible light transmittance). Therefore, when carbon black or other colorants are added to active energy line-curing acrylic adhesives, most of the ultraviolet light irradiated for photocuring is absorbed by the colorant, resulting in less light absorption by the photopolymerization initiator and thus longer photocuring time (due to increased cumulative irradiation). Furthermore, when the adhesive layer is thick, less ultraviolet light reaches the opposite side of the irradiated surface, so even with prolonged irradiation, there is a tendency for insufficient photocuring. In contrast, using colorants with ultraviolet transmittance greater than visible light can suppress the curing resistance caused by the colorant.

Examples of ultraviolet-transmitting black pigments include "9050BLACK" and "UVBK-0001" manufactured by TOKUSHIKI CO.,Ltd. Examples of ultraviolet-absorbing black dyes include "VALIFAST BLACK 3810" and "NUBIAN Black PA-2802" manufactured by ORIENT CHEMICAL INDUSTRIES CO.,LTD. Examples of ultraviolet-absorbing black pigments include carbon black and titanium black.

The content of the colorant in the adhesive layer of this invention is, for example, about 0.01 to 20 parts by weight relative to 100 parts by weight of the base polymer, which can be appropriately set according to the type of colorant or the color tone and light transmittance of the adhesive layer. The colorant can also be added to the composition in the form of a solution or dispersion dissolved or dispersed in a suitable solvent.

The adhesive layer of this invention may also, as needed and without compromising the effectiveness of the invention, further contain additives such as crosslinking promoters, tackifying resins (rosin derivatives, polyterpene resins, petroleum resins, oil-soluble phenols, etc.), anti-aging agents, fillers, antioxidants, chain transfer agents, plasticizers, softeners, and surfactants. Furthermore, the additives may be used alone or in combination of two or more.

The fog level of the adhesive layer of this invention is not particularly limited, but from the perspective of appearance, transparency, and optical properties, it is preferable to be below 5%, more preferably below 3%, and even more preferably below 1%. Furthermore, in this specification, the fog level of the adhesive layer can be measured using a fog meter, following JIS K 7136.

The total light transmittance of the adhesive layer in this invention is not particularly limited, but considering its appearance, transparency, and optical properties, it is preferable to be 85% or higher, more preferably 90% or higher, and even more preferably 92% or higher. Furthermore, in this specification, the total light transmittance of the adhesive layer can be measured, for example, using a haze meter according to JIS K 7361-1. Moreover, the aforementioned total light transmittance refers to the transmittance of light with a wavelength of 400~780nm (visible light).

The thickness of the adhesive layer in this invention is not particularly limited, but from the perspective of obtaining sufficient adhesion reliability, it is preferable to be 12µm or more, more preferably 15µm or more, even more preferably 20µm or more, and especially preferably 70µm or more. A thickness of 12µm or more is ideal in that the adhesive layer fully follows the shrinkage or expansion of the image display device under the operating environment, thereby suppressing bulging or peeling. Furthermore, from the perspective of optical properties, the thickness is preferable to be 500µm or less, preferably 300µm or less, and even more preferably 200µm or less.

<Manufacturing of Optical Adhesive Tape> The optical adhesive tape of this invention can be manufactured by depositing an adhesive layer of this invention onto the first surface of a substrate of this invention.

The method for depositing the adhesive layer of the present invention onto the first surface of the substrate of the present invention is not particularly limited. For example, it can be carried out by: applying the adhesive composition to a release element and allowing the resulting adhesive composition layer to dry and harden; or, applying the adhesive composition to a release element and irradiating the resulting adhesive composition layer with active energy lines to harden it, thereby forming a sheet-like adhesive layer on the release element, and then adhering the aforementioned adhesive layer to the first surface of the substrate of the present invention. Alternatively, further heating and drying may be performed as needed. When curing by irradiation with active energy lines, it is advisable to further attach separation elements to the coating surface, sandwich the adhesive composition between two separation elements, and then irradiate with active energy lines in this state to prevent oxygen from causing polymerization inhibition.

Other methods for depositing the adhesive layer of the present invention onto the first surface of the substrate of the present invention may also be carried out, for example, by applying the adhesive composition to the first surface of the substrate of the present invention and allowing the resulting adhesive composition layer to dry and harden; or, by applying the adhesive composition to the first surface of the substrate of the present invention and irradiating the resulting adhesive composition layer with active energy lines to harden it. Alternatively, further heating and drying may be performed as needed. When hardening by irradiation with active energy lines, it is advisable to attach a separating element to the surface of the coating, sandwich the adhesive composition between the substrate of the present invention and the separating element, and irradiate with active energy lines in this state to prevent oxygen from causing polymerization inhibition.

Before irradiation with active energy lines, the sheet-like coating can be heated to remove solvents, etc. When using heating to remove solvents, etc., it is advisable to do so before installing a separation device.

The aforementioned active energy lines can include, for example, ionizing radiation such as alpha rays, beta rays, gamma rays, neutron rays, electron beams, or ultraviolet rays, with ultraviolet rays being particularly preferred. Furthermore, there are no particular restrictions on the irradiation energy, irradiation time, or irradiation method of the active energy lines.

The aforementioned adhesive compositions can be manufactured using known and conventional methods. For example, solvent-based acrylic adhesive compositions can be manufactured by adding additives (such as UV absorbers) as needed to a solution containing the aforementioned acrylic polymer. For example, active energy line curing acrylic adhesive compositions can be manufactured by adding additives (such as UV absorbers) as needed to a mixture of the aforementioned acrylic monomers or a portion thereof.

Furthermore, the coating of the aforementioned adhesive composition can also be performed using known coating methods. For example, coating machines such as gravure roller coating machines, reverse roller coating machines, contact roller coating machines, dip roller coating machines, rod coating machines, scraper coating machines, spray coating machines, corner wheel coating machines, and direct coating machines can be used.

Especially when forming an adhesive layer using an active energy line curing adhesive composition, the active energy line curing adhesive composition should preferably include a photopolymerization initiator. Furthermore, when the active energy line curing adhesive composition contains an ultraviolet absorber, the photopolymerization initiator should preferably include at least a photopolymerization initiator with light absorption properties over a broad wavelength range. For example, it should preferably include at least a photopolymerization initiator with light absorption properties under visible light in addition to ultraviolet light. This is because the action of ultraviolet absorbers may hinder the curing process of the active energy lines, but if a photopolymerization initiator with light absorption properties over a broad wavelength range is included, high photocurability can be easily obtained in the adhesive composition.

<Antistatic Layer> Antistatic layers can also be present on the surface or between any layers in the optical adhesive tape of this invention. By having an antistatic layer, damage to the adhered object, such as an image display panel, can be prevented. The aforementioned antistatic layer is preferably formed between the substrate and the adhesive layer of this invention.

The aforementioned antistatic layer is not particularly limited, and may be, for example, an antistatic layer formed by coating a conductive coating liquid containing a conductive polymer onto a separating element. Specifically, for example, an antistatic layer formed by coating a conductive coating liquid containing a conductive polymer onto the first surface of the substrate of this invention. Specific coating methods may include roller coating, rod coating, gravure coating, etc.

Examples of the aforementioned conductive polymers include conductive polymers doped with polyvalent anions in π-concentric conductive polymers. Examples of π-concentric conductive polymers include chain-like conductive polymers such as polythiophene, polypyrrole, polyaniline, and polyacetylene. Examples of polyvalent anions include polystyrene sulfonic acid, polyisoprene sulfonic acid, polyethylene sulfonic acid, polyallyl sulfonic acid, polyethyl sulfonic acid, and polymethacrylic acid.

The thickness of the aforementioned antistatic layer should preferably be 1nm~1000nm, and more preferably 5nm~900nm. The aforementioned antistatic layer may be a single layer or two or more layers.

<Separator> In this invention's optical adhesive tape, the surface of the adhesive layer (the adhesive surface of the adhesive layer) can also be protected by a separator until use. The separator acts as a protective material for the adhesive layer and is removed when the optical adhesive tape is applied to the substrate.

The aforementioned separation element can utilize conventional release paper, etc. Specifically, in addition to a substrate having a release treatment layer formed by a release treatment agent on at least one surface, a low-adhesion substrate composed of fluoropolymers (such as polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, chlorofluoroethylene-vinylidene fluoride copolymer, etc.) or a low-adhesion substrate composed of nonpolar polymers (such as polyethylene, polypropylene and other olefinic resins, etc.) can also be used.

The aforementioned separation element may, for example, be a separation element for which at least one side of a substrate for the separation element has a peeling treatment layer. Examples of substrates for the separation element include: polyester film (polyethylene terephthalate film, etc.), olefinic resin film (polyethylene film, polypropylene film, etc.), polyvinyl chloride film, polyimide film, polyamide film (nylon film), rayon film, and other plastic-based substrate films (synthetic resin films) or paper (wood paper, Japanese paper, kraft paper, glassine paper, synthetic paper, coated paper, etc.). In addition, there are composites obtained by lamination or co-extrusion (2-3 layer composites), etc.

The release agent constituting the above-mentioned release treatment layer is not particularly limited. For example, polysiloxane-based release agents, fluorine-based release agents, long-chain alkyl-based release agents, etc., can be used. The release agent can be used alone or in combination of two or more.

The thickness of the aforementioned separator is not particularly limited; it can be appropriately selected from the range of 5 to 100 µm.

In order to prevent damage to the image display panel and other objects adhered to by the aforementioned separator, an antistatic layer may be formed on at least one side of the substrate of the separator. The antistatic layer may be formed on one side of the separator (the peeled side or the untreated side), or it may be formed on both sides of the separator (the peeled side and the untreated side).

The aforementioned antistatic layer is not particularly limited, and can be, for example, an antistatic layer formed by applying a conductive coating liquid containing a conductive polymer onto the separation element. Specifically, for example, it can be an antistatic layer formed by applying a conductive coating liquid containing a conductive polymer onto the separation element (peel-treated surface and/or untreated surface). Specific coating methods may include roller coating, rod coating, gravure coating, etc.

The aforementioned conductive polymer may be the same as the conductive polymer constituting the antistatic layer of the optical adhesive tape of the present invention.

The thickness of the aforementioned antistatic layer should preferably be 1nm~1000nm, and more preferably 5nm~900nm. The aforementioned antistatic layer may be a single layer or two or more layers.

<Surface Protective Film> In the optical adhesive tape of this invention, the second side of the substrate can also be protected by a surface protective film. This surface protective film can be used as a protective material for the second side of the substrate during the manufacture or transportation of the optical adhesive tape, the image display device, or the video wall display of this invention.

The aforementioned surface protective film forming materials may include ester resins such as polyethylene terephthalate resins, cycloalkenyl resins such as norethene resins, olefinic resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymers thereof. Ester resins (especially polyethylene terephthalate resins) are preferred.

The thickness of the aforementioned surface protective film is typically 20µm to 250µm, but preferably 30µm to 150µm.

The aforementioned surface protective film can be peeled off onto the second surface of the substrate of the present invention using any suitable adhesive. It is preferable to form a surface protective film with an adhesive layer and then adhere it to the second surface of the substrate of the present invention for the optical adhesive tape of the present invention. Adhesives suitable for laminating the aforementioned surface protective film may include compositions of adhesives such as acrylic resins, styrene resins, polysiloxane resins, etc., as base resins, and crosslinking agents selected from isocyanate compounds, epoxide compounds, acrylamide compounds, etc., and silane coupling agents, etc., are mixed into the base resin. The thickness of the adhesive layer is typically 1µm to 60µm, preferably 3µm to 30µm. If the adhesive layer is too thin, there is a risk of reduced adhesion and easy inclusion of air bubbles, while if it is too thick, there is a risk of adhesive seepage. From the perspective of chemical resistance and adhesion, acrylic adhesives are suitable.

<Image Display Device> This invention provides an image display device having a laminated structure in which the optical adhesive tape of this invention and an image display panel are laminated. In Figure 3, the image display device 20 has the image display panel 4 laminated on the adhesive layer 1 of the optical adhesive tape 10B.

The image display device of this invention incorporates the optical adhesive tape of this invention within its laminated structure, thereby suppressing shrinkage or expansion under operating conditions while maintaining transparency. Furthermore, the adhesive layer of this invention fully follows the shrinkage or expansion of the image display device, preventing unevenness or peeling. Moreover, when there are height differences in the image display panel caused by wiring or other irregularities, the adhesive layer of this invention fully follows these differences, thus filling them without leaving air bubbles or other residues.

The aforementioned image display panel is not particularly limited and can include, for example, liquid crystal image display panels, self-emissive image display panels (such as organic EL (electroluminescent) image display panels, LED image display panels, etc.).

The aforementioned image display panel is formed by alternating RGB elements, and in order to improve contrast, the spaces between the RGB elements should be filled with a black matrix (BM).

The image display device of this invention may also have optical components other than the optical adhesive tape of this invention and the aforementioned image display panel on its surface or between any layers. The aforementioned optical components are not particularly limited and may include polarizing plates, retardation plates, anti-reflective films, viewing angle adjustment films, optical compensation films, etc. Furthermore, the aforementioned optical components may also include components that maintain the visibility of the image display device or input device while simultaneously providing decorative or protective functions (design films, decorative films, or surface protective films, etc.).

The image display device of the present invention can be manufactured by bonding the aforementioned image display panel with the adhesive layer of the optical adhesive tape of the present invention.

Specifically, the image display panel can be attached to the optical adhesive tape of this invention by lamination under heat and/or pressure. Alternatively, after lamination under heat and/or pressure, it can be cured by irradiation with active energy lines. The irradiation of the active energy lines can be carried out in the same manner as the formation of the adhesive layer of this invention.

<Video Wall Display> This invention relates to a video wall display formed by arranging a plurality of image display devices of this invention. In Figure 4, the video wall display 30 is formed by arranging nine image display devices 20 (layer structure omitted) in a 3×3 configuration on a support substrate 31 in a video wall shape, with the image display devices 20 connected to each other by gaps 32. The aforementioned support substrate can be a glass plate or a plastic film of the same type as the substrate of this invention.

The image display device of this invention suppresses shrinkage or expansion under the operating environment. Therefore, gaps or overlaps are less likely to occur between multiple image display devices in the splicing display of this invention, and the gaps are not obvious, thus maintaining a good appearance. Furthermore, with minimal shrinkage or expansion, transparency remains unchanged. In addition, the adhesive layer of this invention fully follows the shrinkage or expansion of the image display device, thus preventing defects caused by bulging or peeling.

Furthermore, in the splicing display of the present invention, when an anti-reflective treatment and/or anti-glare treatment is applied to the second surface of the substrate of the present invention, it is ideal in terms of preventing reflections caused by metal wiring or ITO wiring on the substrate of the image display device of the present invention. It is also ideal in terms of making it difficult to discern the gaps between the image display devices of the present invention in the splicing display.

The splicing display of this invention may also include components other than the image display device of this invention and the aforementioned support substrate. The components are not particularly limited and may include backlight components, touch sensors, etc.

The splicing display of the present invention can be manufactured by arranging a plurality of the present invention image display devices without gaps on the aforementioned support substrate and fixing them with glass sealing on the outermost surface.

Examples of Embodiments The invention will now be described in more detail with reference to examples, but the invention is not limited to these examples.

Manufacturing Example 1 (Preparation of Anti-glare Film 1) [Preparation of Coating Solution for Forming Anti-glare Layer 1] The resin contained in the anti-glare layer forming material is mixed with 40 parts by weight of UV-curable carbamate acrylate resin (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name "NK Oligo UA-53H-80BK"), 57.5 parts by weight of a multifunctional acrylate with neopentyl terephthalate triacrylate as the main component (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name "Viscoat #300"), 2.5 parts by weight of a diluent for an optical conditioning layer composition containing zirconium oxide particles and UV-curable resin ("OPSTAR Z7540", manufactured by JSR Co., Ltd.), and polysiloxane particles (manufactured by Momentive Performance Materials Japan LLC., trade name "Tospearl"). The composition includes 2.8 parts by weight of 130ND, 2.5 parts by weight of synthetic bentonite (manufactured by KUNIMINE INDUSTRIES CO., LTD., trade name "SUMECTON SAN") as a thixotropic agent, 3 parts by weight of photopolymerization initiator (manufactured by BASF, trade name "OMNIRAD907"), 6.5 parts by weight of crosslinked acrylic styrene copolymer microparticles (manufactured by Sekisui Chemicals Co., Ltd., trade name "SSX-103DXE"), and 0.1 parts by weight of leveling agent (manufactured by Kyoei Chemical Co., Ltd., trade name "LE-303"). Furthermore, the aforementioned organic clay was diluted with toluene to a solid content of 6% by weight before use. The mixture was diluted with a toluene/cyclopentanone (CPN) solvent (64/36 by weight) to a solid concentration of 38% by weight, and then prepared into an anti-glare coating material (coating solution) using an ultrasonic disperser.

[Formation of Anti-glare Layer 1] A transparent plastic film substrate (PET film, manufactured by TORAY Corporation, trade name "38U413", thickness: 38µm) was prepared as the substrate. The aforementioned anti-glare layer forming material (coating liquid) was applied to one side of the aforementioned transparent plastic film substrate using a wire rod to form a coating film (coating step). Next, the aforementioned coating film was dried by heating at 95°C for 1 minute (drying step). Afterward, the aforementioned coating film was cured by irradiating it with ultraviolet light with a cumulative light intensity of 300mJ/ ^cm2 using a high-pressure mercury lamp to form an anti-glare layer with a thickness of 6.5µm. The aforementioned light-transmitting substrate and the aforementioned anti-glare layer 1 were obtained in the above manner.

[Preparation of the coating solution for forming antireflective layer 1] Mix 100 parts by weight of a multifunctional acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name "Viscoat #300") with neopentyl tert-acrylate as the main component, and hollow silica nanoparticles (manufactured by Nichih Catalyst Chemical Industry Co., Ltd., trade name "THRULYA") 100 parts by weight of 5320", 40 parts by weight of solid nano silica particles (manufactured by Nissan Chemical Industries, Ltd., trade name "MIBK-ST", solid content 30% by weight, weight average particle size 10nm), 12 parts by weight of fluorine-containing additive (manufactured by Shin-Etsu Chemical Industries, Ltd., trade name "KY-1203"), 5 parts by weight of photopolymerization initiator (manufactured by BASF, trade name "OMNIRAD907") and 5 parts by weight of photopolymerization initiator (manufactured by BASF, trade name "OMNIRAD2959"). In this mixture, a mixed solvent consisting of MIBK (methyl isobutyl ketone) and PMA (propylene glycol monomethyl ether acetate) in a weight ratio of 70:30 is added as a diluent to bring the total solid content to 1.5% by weight. The mixture is then stirred to prepare an anti-reflective layer forming coating solution. [Formation of Anti-reflective Layer 1] The aforementioned anti-reflective layer forming coating solution is applied using a wire rod to the anti-glare layer surface of the laminate between the aforementioned light-transmitting substrate and the aforementioned anti-glare layer 1 (coating step). The coated solution is then heated at 80°C for 1 minute to dry and form a coating film (drying step). The dried coating was irradiated with ultraviolet light at a cumulative intensity of 300 mJ/ ^cm² using a high-pressure mercury lamp to perform a curing treatment (curing step). This cured the coating, forming an anti-reflective layer 1 with a thickness of 0.1 µm (anti-reflective layer formation step). The anti-glare film 1 of this manufacturing example 1 was produced in the above manner.

Manufacturing Example 2 (Preparation of Anti-glare Film 2) [Formation of Anti-glare Layer 2] When preparing the coating liquid for forming the anti-glare layer, the amount of the aforementioned polyfunctional acrylate with neopentyl terephthalate triacrylate as the main component was changed to 60 parts by weight, the amount of polysiloxane particles was changed to 0.9 parts by weight, the amount of synthetic bentonite organic clay as a thixotropic excipient was changed to 1.5 parts by weight, and the diluent of the optical conditioning layer composition containing zirconium oxide particles and UV-curing resin, and the microparticles of crosslinked acrylic styrene copolymer resin were not used. Otherwise, the aforementioned laminate of light-transmitting substrate and anti-glare layer 2 was produced using the same method as in Manufacturing Example 1. [Formation of Anti-reflective Layer 2] When preparing the coating solution for forming the anti-reflective layer, the amount of hollow nano-silica particles was changed to 240 parts by weight. Otherwise, the anti-reflective layer 2 was formed using the same method as in Manufacturing Example 1. The anti-glare film 2 of Manufacturing Example 2 was thus produced in the above manner.

Manufacturing Example 3 (Preparation of Anti-glare Film 3) In forming the anti-glare layer, a transparent plastic film substrate (COP film, manufactured by ZEON Corporation, Japan, trade name "ZF14", thickness: 50µm) was used as the substrate. Otherwise, the anti-glare film 3 of this Manufacturing Example 3 was manufactured using the same method as in Manufacturing Example 1.

Manufacturing Example 4 (Preparation of Anti-glare Film 4) In forming the anti-glare layer, a transparent plastic film substrate (PEN film, manufactured by Toyoshoku, trade name "Q51", thickness: 25µm) was used as the substrate. Otherwise, the anti-glare film 4 of this Manufacturing Example 4 was manufactured using the same method as in Manufacturing Example 1.

Manufacturing Example 5 (Preparation of Anti-glare Film 5) In forming the anti-glare layer, a transparent plastic film substrate (PEEK film, manufactured by KURABO, trade name "EXPEEK", thickness: 50µm) was used as the substrate. Otherwise, the anti-glare film 5 of this Manufacturing Example 5 was manufactured using the same method as in Manufacturing Example 1.

Manufacturing Example 6 (Manufacturing of Transparent Plastic Film Substrate) Replacing 81.98 parts by weight of isosorbide (hereinafter referred to as "ISB"), 47.19 parts by weight of tricyclodecanediethanol (hereinafter referred to as "TCDDM"), 175.1 parts by weight of diphenyl carbonate (hereinafter referred to as "DPC"), and 0.979 parts by weight of a 0.2% aqueous solution of cesium carbonate as a catalyst are added to a reaction vessel. Under a nitrogen atmosphere, as the first step of the reaction, the temperature of the heating tank is raised to 150°C, and the raw materials are stirred as needed to dissolve (approximately 15 minutes). Next, the pressure was changed from atmospheric pressure to 13.3 kPa, and the heating tank temperature was raised to 190°C over 1 hour while the generated phenol was discharged from the reaction vessel. After maintaining the entire reaction vessel at 190°C for 15 minutes, as the second step, the pressure inside the reaction vessel was set to 6.67 kPa, and the heating tank temperature was raised to 230°C over 15 minutes, while the generated phenol was discharged from the reaction vessel. Since the stirring torque of the agitator increases over time, in order to raise the temperature to 250°C in 8 minutes and further remove the generated phenol, the pressure inside the reaction vessel was brought down to below 0.200 kPa. After reaching the predetermined stirring torque, the reaction is terminated, and the resulting reactants are extruded into water to obtain polycarbonate resin pellets. The obtained polycarbonate resin is then vacuum-dried at 80°C for 5 hours. A film-forming apparatus equipped with a single-shaft extruder (manufactured by Shibaura Machinery Co., Ltd., cylinder temperature setting: 250°C), a T-die (300mm wide, temperature setting: 250°C), a cooling roller (temperature setting: 120~130°C), and a winding machine is used to produce a 40µm thick transparent plastic film substrate made of polycarbonate resin. (Preparation of Anti-glare Film 6) In forming the anti-glare layer, the transparent plastic film substrate made of polycarbonate resin obtained above was used as the substrate. Otherwise, the anti-glare film 6 of this Manufacturing Example 6 was manufactured using the same method as in Manufacturing Example 1.

Manufacturing Example 7 (Preparation of Anti-glare Film 7) In forming the anti-glare layer, a transparent plastic film substrate (CPI film, manufactured by KOLON Corporation, trade name "C_50_D", thickness: 50µm) was used as the substrate. Otherwise, the anti-glare film 7 of this Manufacturing Example 7 was manufactured using the same method as in Manufacturing Example 1.

Manufacturing Example 8 (Preparation of Anti-glare Film 8) In forming the anti-glare layer, a transparent plastic film substrate (TAC film, manufactured by FUJIFILM, trade name "TD80UL", thickness: 80µm) was used as the substrate. Otherwise, the anti-glare film 8 of this Manufacturing Example 8 was manufactured using the same method as in Manufacturing Example 1.

Manufacturing Example 9 (Preparation of Acrylic Adhesive Composition 1) [Preparation of Acrylic Oligomer] 60 parts by weight of dicyclopentyl methacrylate (DCPMA) and 40 parts by weight of methyl methacrylate (MMA) as monomer components, 3.5 parts by weight of α-thioglycerol as a chain transfer agent, and 100 parts by weight of toluene as a polymerization solvent were mixed and stirred at 70°C for 1 hour under a nitrogen atmosphere. Next, 0.2 parts by weight of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator were added, and the mixture was reacted at 70°C for 2 hours. Then, the temperature was raised to 80°C, and the mixture was reacted for another 2 hours. The reaction solution was then heated to 130°C, and toluene, chain transfer agent, and unreacted monomers were dried to obtain a solid acrylic oligomer (acrylic oligomer A). Acrylic oligomer A has a weight-average molecular weight of 5100 and a glass transition temperature (Tg) of 130°C.

[Preparation of Prepolymer and Acrylic Adhesive Composition 1] The monomer component for prepolymer formation is a mixture of 60 parts by weight of lauryl acrylate (LA), 22 parts by weight of 2-ethylhexyl acrylate (2EHA), 8 parts by weight of 4-hydroxybutyl acrylate (4HBA), and 10 parts by weight of N-vinyl-2-pyrrolidone (NVP), and 0.1 parts by weight of BASF's "Omnirad 184" and 0.1 parts by weight of BASF's "Omnirad 651" as photopolymerization initiators. The mixture is then polymerized under ultraviolet light to obtain the prepolymer composition. To 100 parts by weight of the above prepolymer composition, 37 parts by weight of 2-ethylhexyl acrylate (2EHA), 0.08 parts by weight of 1,6-hexanediol diacrylate (trade name "A-HD-N", manufactured by Shin-Nakamura Chemical Co., Ltd.), 6 parts by weight of the above-mentioned acrylic oligomer A, and 0.3 parts by weight of silane coupling agent (Shin-Etsu Chemical Co., Ltd. "KBM403") were added as post-additional components. These components were then uniformly mixed to prepare acrylic adhesive composition 1.

Manufacturing Example 10 (Preparation of Prepolymer and Acrylic Adhesive Composition 2) The monomer component for prepolymer formation was a mixture of 67 parts by weight of butyl acrylate (BA), 14 parts by weight of cyclohexyl acrylate ("Viscoat #155" manufactured by Osaka Organic Chemicals Co., Ltd.), 19 parts by weight of 4-hydroxybutyl acrylate (4HBA), and 0.09 parts by weight of BASF's "Omnirad 184" and BASF's "Omnirad 651" as photopolymerization initiators. The mixture was then polymerized under ultraviolet light to obtain the prepolymer composition. To 100 parts by weight of the above prepolymer composition, 9 parts by weight of hydroxyethyl acrylate (HEA), 8 parts by weight of 4-hydroxybutyl acrylate (4HBA), 0.02 parts by weight of dipentylenetetramethylol hexaacrylate (DPHA), 0.3 parts by weight of photopolymerization initiator (BASF's "Omnirad 651"), and 0.35 parts by weight of silane coupling agent (Shin-Etsu Chemical's "KBM403") were added as post-additional components. These components were then uniformly mixed to prepare acrylic adhesive composition 2.

Manufacturing Example 11 (Preparation of Prepolymer and Acrylic Adhesive Composition 3) The monomer component for prepolymer formation is a mixture of 78 parts by weight of 2-ethylhexyl acrylate (2EHA), 4 parts by weight of hydroxyethyl acrylate (HEA), and 18 parts by weight of N-vinyl-2-pyrrolidone (NVP), and 0.035 parts by weight of BASF's "Omnirad184" and 0.035 parts by weight of BASF's "Omnirad651" as photopolymerization initiators. The mixture is then polymerized under ultraviolet light to obtain the prepolymer composition. To 100 parts by weight of the above prepolymer composition, 17.6 parts by weight of hydroxyethyl acrylate (HEA), 0.294 parts by weight of 1,6-hexanediol diacrylate (trade name "A-HD-N", manufactured by Shin-Nakamura Chemical Co., Ltd.), 11.8 parts by weight of the above-mentioned acrylic oligomer A, and 0.35 parts by weight of silane coupling agent (Shin-Etsu Chemical Co., Ltd. "KBM403") were added as post-additional components. These components were then uniformly mixed to prepare acrylic adhesive composition 3.

Example 1 (Preparation of Adhesive Layer 1 without Substrate) A polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical Co., "DIAFOIL MRF75") with a thickness of 75µm and a polysiloxane-based release layer on its surface is used as a substrate (also a heavy-duty peel film). The aforementioned acrylic adhesive composition 1 is applied to the release layer of the substrate to a thickness of 25µm to form a coating layer. A release layer of a 75µm thick PET film (manufactured by Mitsubishi Chemical Co., "DIAFOIL MRE75") with a polysiloxane release treatment on one side is bonded onto this coating layer as a cover sheet (also a light-duty peel film). The laminate is photocured by irradiating it with ultraviolet light from the cover sheet side with an intensity of 5 mW/ ^cm² under direct illumination, forming a substrate-free adhesive layer 1 with a thickness of 25 µm. (Preparation of adhesive tape 1) The adhesive surface exposed by peeling off one of the release films from the substrate-free adhesive layer 1 obtained above is attached to the non-anti-glare layer of the anti-glare film 1 shown in Manufacturing Example 1, thereby obtaining an adhesive tape 1 composed of anti-glare film 1, adhesive layer 1, and release film.

Example 2 (Preparation of Adhesive Tape 2) In addition to using the anti-glare film 2 described above, an adhesive tape 2 consisting of an anti-glare film 2, an adhesive layer 1, and a peel-off film is obtained in the same manner as in Example 1.

Example 3 (Preparation of Substrate-Free Adhesive Layer 2) In addition to using the acrylic adhesive composition 2 described above, a substrate-free adhesive layer 2 with a thickness of 25µm was obtained in the same manner as in Example 1. (Preparation of Adhesive Tape 3) In addition to using the substrate-free adhesive layer 2 obtained above, an adhesive tape 3 consisting of an anti-glare film 1, an adhesive layer 2, and a release film was obtained in the same manner as in Example 1.

Example 4 (Preparation of Adhesive Tape 4) In addition to using the anti-glare film 3 described above, an adhesive tape 4 consisting of the anti-glare film 3, adhesive layer 1, and peel-off film is obtained in the same manner as in Example 1.

Example 5 (Preparation of Adhesive Tape 5) In addition to using the anti-glare film 4 described above, an adhesive tape 5 consisting of the anti-glare film 4, adhesive layer 1, and peel-off film is obtained in the same manner as in Example 1.

Example 6 (Preparation of Adhesive Tape 6) In addition to using the anti-glare film 5 described above, an adhesive tape 6 consisting of an anti-glare film 5, an adhesive layer 1, and a peel-off film is obtained in the same manner as in Example 1.

Example 7 (Preparation of Adhesive Tape 7) In addition to using the anti-glare film 6 described above, an adhesive tape 7 consisting of the anti-glare film 6, adhesive layer 1, and peel-off film is obtained in the same manner as in Example 1.

Example 8 (Preparation of Adhesive Tape 8) In addition to using the anti-glare film 7 described above, an adhesive tape 8 consisting of the anti-glare film 7, adhesive layer 1, and peel-off film is obtained in the same manner as in Example 1.

Comparative Example 1 (Preparation of Adhesive Tape 9) In addition to using the anti-glare film 8 described above, an adhesive tape 9 consisting of an anti-glare film 8, an adhesive layer 1, and a peel-off film was obtained in the same manner as in Example 1.

Comparative Example 2 (Preparation of Substrate-Free Adhesive Layer 3) In addition to using the acrylic adhesive composition 3 described above, a substrate-free adhesive layer 3 with a thickness of 25µm was obtained in the same manner as in Example 1. (Preparation of Adhesive Tape 10) In addition to using the anti-glare film 8 and the substrate-free adhesive layer 3 described above, an adhesive tape 10 composed of the anti-glare film 8/adhesive layer 3/release film was obtained in the same manner as in Example 1.

(Evaluation) The adhesive tapes obtained in the above embodiments and comparative examples were evaluated as follows. The evaluation method is shown below. The results are listed in Table 2.

(1) Average Dimensional Change Rate The adhesive tape prepared in each embodiment and comparative example was cut into approximately square shapes (100mm in the MD direction × 100mm in the TD direction) as viewed from above. Cross-shaped scratches were then applied to the four corners of each square to create test pieces. For the test pieces before heating (25°C), the distances (lengths) between the scratches (centers of the cross-shaped scratches) in the MD direction and the distances (lengths) between the scratches in the TD direction were measured at room temperature (25°C) using a CNC 3D measuring machine (Mitutoyo Co., "LEGEX774"). This obtained the lengths before heating in both the MD and TD directions. Next, the test piece was heated for 500 hours at 60°C and 90% relative humidity, and then cooled at room temperature (25°C) for 1 hour. Then, the distances between the MD and TD directions of the scratches were measured using a CNC 3D measuring machine. This allowed for the acquisition of the length after heating in both the MD and TD directions. Next, the dimensional change rates A1 and A2 were calculated in both the MD and TD directions using the following formulas, and their average value was taken as the average dimensional change rate (%). The ratio of the dimensional change rate in the MD direction to the dimensional change rate in the TD direction (A1/A2) was also calculated. Dimensional change rate (%) = [Length after heating (mm) - Length before heating (mm) / Length before heating (mm) × 100 Average dimensional change rate (%) = [Dimensional change rate in MD direction + Dimensional change rate in TD direction] / 2

(2) Maximum Curvature The release film of the adhesive tape prepared in each embodiment and comparative example was peeled off, and a PET film (manufactured by Mitsubishi Chemical Co., trade name "DIAFOIL T100E50", thickness: 50µm) was attached. The resulting laminate was cut into approximately square pieces of 100mm × 100mm from top view to prepare test pieces. The test pieces were then heated at 60°C and 90% relative humidity for 500 hours, and then cooled at room temperature (25°C) for 1 hour. Afterwards, the test pieces were placed on a horizontal plane with the curled protrusions facing down, and the distances between four points at the corners and the horizontal plane were measured. The distance from the point with the longest distance from the horizontal plane was taken as the maximum curvature (mm). Furthermore, the aforementioned laminate is placed on a horizontal surface with the PET film side below, and the maximum curl measured in this manner is positive (+). Conversely, the aforementioned laminate is placed on a horizontal surface with the substrate side (opposite to the PET film) below, and the maximum curl measured in this manner is negative (-).

(3) Reflectivity The adhesive surfaces of the adhesive tapes obtained in each embodiment and comparative example were attached to a black acrylic sheet to prepare test pieces. The adhesive tape side of the test piece was placed on the light source side of a U4100 spectrophotometer (manufactured by Hitachi High-Tech Co.), and the reflectivity (%) of the visible light region at 5° orthogonal reflection was measured.

(4) Fog Level The adhesive tapes obtained in each embodiment and comparative example were measured using a fog level measuring device (HR-100 manufactured by Murakami Color Research Institute) at room temperature (23°C). Measurements were performed three times, and the average value was taken as the measured value.

(5) Shear force of adhesive layer: The adhesive tape obtained in each embodiment and comparative example is cut into a size of 10 mm wide and 100 mm long and the separate parts are peeled off. The adhesive tape is then attached to an acrylic resin board (Acrylite, made by Mitsubishi Chemical Co.) with an adhesive (adhesive) area of 1 cm ^2. The tape is stretched in the shear direction at a peeling speed of 0.06 mm/min at 23°C, and the maximum load (N/cm ² ) at this time is taken as the shear force.

(6) Storage elastic modulus, loss tangent, and glass transition temperature of the adhesive layer Multiple adhesive layers were stacked using adhesive layer peeling separators obtained from the embodiments and comparative examples to produce test samples with a thickness of approximately 2 mm. The test samples were punched into discs with a diameter of 7.9 mm and clamped between parallel plates. Dynamic viscoelasticity was measured using the "Advanced Rheometric Expansion System (ARES)" manufactured by Rheometric Scientific under the following conditions. The storage elastic modulus G' and loss tangent tanδ at each temperature were read from the measurement results. Furthermore, the temperature at which tanδ reaches its maximum is used as the glass transition temperature of the adhesive layer. (Measurement Conditions) Deformation Mode: Torsion Measurement Frequency: 1Hz Measurement Temperature: -70℃~150℃

(7) 300% Tensile Residual Stress Value of Adhesive Layer The adhesive layers obtained in each embodiment and comparative example were cut into 40mm×40mm sizes. After removing one side of the separator, the layers were folded once to make the adhesive surfaces adhere to each other. After removing the single side separator again, the adhesive surfaces were adhered to each other again to produce an adhesive layer sample with a size of approximately 10mm×40mm and a thickness of approximately 400µm. The adhesive layer sample was installed in a tensile testing machine with a fixture spacing set to 20mm and stretched at a tensile speed of 200mm/min for 60mm (300%) (the fixture spacing after stretching is 80mm). The tension was held at a 60mm position for 300 seconds, and the stress value was measured afterward. The "300% tensile residual stress value" was calculated using the following formula: 300% tensile residual stress value (N/ ^cm2 ) = Stress value after holding for 300 seconds (N) / (4 × adhesive sheet thickness (mm) / 10)

(8) Strain A, Strain B, and Recovery Rate The adhesive layer peeling and separation parts obtained from the various embodiments and comparative examples were used to build up multiple layers of adhesive to produce test specimens with a thickness of approximately 2 mm. The test specimens were then punched into discs with a diameter of 7.9 mm to form sample materials. The shear test used to calculate "Strain A", "Strain B", and "Recovery Rate" was performed under the conditions shown in Figure 5. Specifically, an "Advanced Rheometric Expansion System (ARES)" manufactured by Rheometric Scientific, consisting of parallel plates 41 and 42 with a diameter of 7.9 mm, was used. The upper surface of parallel plate 41 and the bottom surface of parallel plate 42 were aligned with the bottom and upper surfaces of the adhesive layer of the sample and brought into contact (Fig. 5(b)). Next, dynamic viscoelasticity was measured under the following conditions. The strain A at 600 seconds (Fig. 5(c)) at 500 Pa and the strain B at 1800 seconds (Fig. 5(d)) after being maintained at 0 Pa were recorded. The recovery rate was calculated using the following formula. (Test Conditions) Deformation Mode: Torsion Test Process: Maintained at 500 Pa for 600 seconds, then maintained at 0 Pa for 1800 seconds. Measurement temperature: 60℃ Axial force: 0.2N Recovery rate: (Strain A - Strain B) / Strain A × 100

(9) Humidity Expansion Rate The adhesive tapes obtained in each embodiment and comparative example were cut into pieces with a width of 2mm in the TD direction and a length of 20mm in the MD direction. The expansion rate was measured using a Bruker AXS HC-TMA4000SA model under the following conditions: (Test Conditions) Deformation Mode: Tension Load: 2g Holding Time: 5 hours Heating Rate: 5%RH/min Test Gas Environment: Maintained at 60°C and 30% relative humidity until saturation, and then controlled at 60°C and 60% relative humidity.

(10) Humidity Swelling Coefficient of Substrate The humidity swelling coefficient was determined using a Bruker AXS HC-TMA4000SA film, measuring the elongation of each film at 60°C as the humidity changed from 30%RH to 60%RH. (Unit: /RH%) The humidity swelling coefficient (α) was calculated using the following formula. α = ΔL / {(T2 - T1) × L} T1: Humidity on the low-humidity side (%RH) for calculating the coefficient of humidity expansion T2: Humidity on the high-humidity side (%)RH for calculating the coefficient of humidity expansion ΔL: Difference between the length of the test piece at T1 and the length at T2 (µm) L: Length of the test piece at room temperature (60℃) (µm)

(11) Glass transition point (Tg) of the substrate: Approximately 8 mg of sample was placed in an aluminum container for DSC measurement. Apparatus: TA Instruments Q-2000; Container: Aluminum container; Temperature process: -30℃→300℃; Heating rate: 10℃/min; Ambient gas: _N2 (50 ml/min)

(12) Confirmation of Gaps Between Adhesive Tapes The adhesive tapes obtained in the embodiments and comparative examples were cut into 5cm × 5cm pieces, and four pieces were seamlessly adhered to the glass. After heating at 60°C and 90% relative humidity for 500 hours, the pieces were cooled at room temperature (25°C) for 1 hour. Then, the glass was placed on a backlight and illuminated by the backlight. The gaps between the adhesive tapes were visually evaluated according to the following criteria: ○: No gaps between adhesive tapes confirmed. ×: Gap between adhesive tapes confirmed.

(13) Confirmation of Adhesive Peeling The adhesive tape ends of the samples used for confirming the gaps between the adhesive tapes were heated at 60°C and 90% relative humidity for 500 hours using an optical microscope and evaluated according to the following criteria: ○: No adhesive peeling was confirmed. ×: Adhesive peeling was confirmed.

[Table 2]

The following are examples of variations of the present invention. [Note 1] An optical adhesive tape has a laminated structure having a substrate and an adhesive layer, the substrate having a first side and a second side, and the adhesive layer being located on the first side of the substrate; The optical adhesive tape is characterized in that: after the optical adhesive tape is heated in an environment of 60°C and 90% relative humidity for 500 hours, the average dimensional change rate in the width direction and the mechanical direction is within ±0.15%; when the adhesive area of the adhesive layer is 1 ^cm² and it is adhered to a resin board, the shear force when stretched in the shear direction at a tensile speed of 0.06 mm/min at 23°C is less than 20 N/ ^cm² . [Appendix 2] As in Appendix 1, the optical adhesive tape is heated at 60°C and 90% relative humidity for 500 hours, and the average dimensional change rate in the width and mechanical directions is C[%]. The adhesive layer of the optical adhesive tape is bonded to a 50µm thick PET film and then cut into 10cm squares to obtain a laminate. The maximum curling amount of the laminate after being heated at 60°C and 90% relative humidity for 500 hours is D[mm]. This satisfies the following formula. |C×D|≦3 • Maximum Curl: With the curled protrusion of the aforementioned laminate placed on a horizontal plane with the curled protrusion facing down, the highest of the four corner curls is taken as the maximum curl D [mm]. With the aforementioned laminate placed on a horizontal plane with the aforementioned PET film side facing down, the maximum curl measured in this way is +, and with the aforementioned laminate placed on a horizontal plane with the aforementioned substrate side facing down, the maximum curl measured in this way is -. [Note 3] As in Note 1 or 2, the optical adhesive tape wherein the glass transition point (Tg) of the aforementioned substrate is 60°C or higher. [Note 4] For any of the optical adhesive tapes described in Notes 1 to 3, the glass transition point (Tg) of the aforementioned adhesive layer is below -10°C. [Note 5] For any of the optical adhesive tapes described in Notes 1 to 4, after humidifying the aforementioned optical adhesive tape from 60°C and 30% relative humidity to 60°C and 60% relative humidity, its humidity expansion rate is below 0.1%. [Note 6] For any of the optical adhesive tapes described in Notes 1 to 5, the humidity expansion coefficient of the aforementioned substrate is below 5 × ^10⁻⁵ /%RH. [Note 7] For any of the optical adhesive tapes described in Notes 1 to 6, the second side of the aforementioned substrate has been treated with anti-reflective coating and/or anti-glare coating. [Note 8] An optical adhesive tape as described in any of Notes 1 to 7, wherein the aforementioned adhesive layer is an acrylic adhesive layer comprising an acrylic polymer. [Note 9] An image display device comprising an optical adhesive tape as described in any of Notes 1 to 8 and an image display panel. [Note 10] A video wall display comprising a plurality of image display devices as described in Note 9 arranged together.

10A, 10B: Optical adhesive tape 1: Substrate 1a: First side of the substrate 1b: Second side of the substrate 2: Adhesive layer 3: Anti-reflective treatment and/or anti-glare treatment 20: Image display device 4: Image display panel 30: Video wall display 31: Support substrate 32: Gap 40: Adhesive layer 41, 42: Parallel plates F: Shear force MD: Mechanical direction TD: Width direction

Figure 1 is a schematic diagram showing one embodiment of the optical adhesive tape of the present invention; (a) is a cross-sectional view, and (b) is a top view. Figure 2 is a schematic diagram (cross-sectional view) showing another embodiment of the optical adhesive tape of the present invention. Figure 3 is a schematic diagram (cross-sectional view) showing one embodiment of the image display device of the present invention, wherein the optical adhesive tape of Figure 2 is laminated. Figure 4 is a schematic diagram (stereoscopic view) showing one embodiment of the splicing display of the present invention. Figure 5 is a schematic diagram (stereoscopic view) used to illustrate a shear test.

10A: Optical Adhesive Tape 1: Substrate 1a: First side of the substrate 1b: Second side of the substrate 2: Adhesive Layer MD: Mechanical Direction TD: Width Direction

Claims (10)

An optical adhesive tape has a laminated structure comprising a substrate and an adhesive layer, the substrate having a first side and a second side, and the adhesive layer being located on the first side of the substrate; the optical adhesive tape is characterized in that: after the optical adhesive tape is heated in an environment of 60°C and 90% relative humidity for 500 hours, the average dimensional change rate in its width direction and mechanical direction is within ±0.15%; when the adhesive area of the adhesive layer is 1 ^cm² bonded to an acrylic resin board, the shear force when stretched in the shear direction at a tensile speed of 0.06 mm/min at 23°C is less than 20 N/ ^cm² . For the optical adhesive tape of claim 1, after heating the aforementioned optical adhesive tape at 60°C and 90% relative humidity for 500 hours, the average dimensional change rate in its width and mechanical directions is C [%]. Furthermore, after laminating the aforementioned adhesive layer of the optical adhesive tape onto a 50µm thick PET film and cutting it into 10cm squares to obtain a laminate, the maximum curling amount of the laminate after heating it at 60°C and 90% relative humidity for 500 hours is D [mm]. This satisfies the following formula: |C×D|≦3 • Maximum curl: With the curled protrusion of the aforementioned laminate placed on a horizontal plane with the curled protrusion facing down, the highest of the four corner curls is taken as the maximum curl D [mm]; with the aforementioned laminate placed on a horizontal plane with the aforementioned PET film side facing down, the maximum curl measured in this way is +, and with the aforementioned laminate placed on a horizontal plane with the aforementioned substrate side facing down, the maximum curl measured in this way is -. For example, the optical adhesive tape of claim 1 or 2, wherein the glass transition point (Tg) of the aforementioned substrate is above 60°C. For example, the optical adhesive tape of claim 1 or 2, wherein the glass transition point (Tg) of the aforementioned adhesive layer is below -10°C. For example, the optical adhesive tape of claim 1 or 2, after being humidified from 60°C and 30% relative humidity to 60°C and 60% relative humidity, has a humidity expansion rate of less than 0.1%. For example, the optical adhesive tape of request item 1 or 2, wherein the humidity expansion coefficient of the aforementioned substrate is less than 5× ^10⁻⁵ /%RH. For example, the optical adhesive tape of claim 1 or 2, wherein the second side of the aforementioned substrate has been treated with anti-reflective and/or anti-glare treatment. For example, the optical adhesive tape of claim 1 or 2, wherein the aforementioned adhesive layer is an acrylic adhesive layer comprising an acrylic polymer. An image display device comprising an optical adhesive tape as described in any of claims 1 to 8 and an image display panel. A video wall display is an image display device having a plurality of panels arranged as described in Request 9.