TWI856195B - Image display device and optical component set - Google Patents

Abstract

The present invention provides an image display device in which an irregularly shaped processed portion is filled with an adhesive and air bubbles are significantly suppressed. The image display device of the present invention comprises: an image display unit; a first polarizing plate, which includes a first polarizing element and a first adhesive layer, and is laminated on the visual side of the image display unit via the first adhesive layer; a second polarizing plate, which includes a second polarizing element and a second adhesive layer, and is laminated on the back side of the image display unit via the second adhesive layer; and a third adhesive layer, which is arranged on the visual side of the first polarizing plate. The first polarizing plate and the second polarizing plate have a special-shaped processed portion at positions corresponding to each other, and the special-shaped processed portion of the first polarizing plate is filled with an adhesive constituting the third adhesive layer. The thickness of the first polarizing plate is less than 90 μm, the thickness of the third adhesive layer is more than 170 μm, and the storage modulus of the third adhesive layer at 60°C is less than 8.0×10 ⁴ Pa.

Description

Image display device and optical component set

The present invention relates to a set of image display device and optical components.

Optical laminates (e.g., polarizing plates) are widely used in image display devices such as mobile phones and notebook personal computers to realize image display and/or improve the performance of the image display. In recent years, optical laminates are also used in image display devices equipped with cameras, smart watches, and dashboards of cars. Optical laminates are sometimes processed into shapes other than rectangular (special processing: for example, the formation of notches or through holes). On the other hand, sometimes a cover glass is applied to the outermost surface of the image display device to give the image display device surface hardness and impact resistance. When a cover glass is laminated on an image display device including an optical laminate having been processed in a special shape, the special-shaped processed portion is typically filled with an adhesive used to laminate the cover glass. However, an image display device in which the special-shaped processed portion is filled with an adhesive may sometimes generate bubbles due to heat treatment during the manufacturing process. Prior Art Literature Patent Literature

Patent document 1: Japanese Patent Publication No. 2016-094569

[The problem the invention is trying to solve]

The present invention is completed to solve the above-mentioned previous problems. Its main purpose is to provide an image display device in which the irregularly shaped processed part is filled with adhesive and the bubbles are obviously suppressed. [Technical means for solving the problem]

The image display device of the present invention comprises: an image display unit; a first polarizing plate, which comprises a first polarizing element and a first adhesive layer, and is laminated on the visual side of the image display unit via the first adhesive layer; a second polarizing plate, which comprises a second polarizing element and a second adhesive layer, and is laminated on the back side of the image display unit via the second adhesive layer; and a third adhesive layer, which is arranged on the visual side of the first polarizing plate. The first polarizing plate and the second polarizing plate have a special-shaped processing portion at positions corresponding to each other, and the special-shaped processing portion of the first polarizing plate is filled with the adhesive constituting the third adhesive layer. The thickness of the first polarizing plate is less than 90 μm, the thickness of the third adhesive layer is more than 170 μm, and the storage modulus of the third adhesive layer at 60° C. is less than 8.0×10 ⁴ Pa. In another embodiment of the present invention, the image display device comprises: an image display unit; a first polarizing plate, which comprises a first polarizing element and a first adhesive layer, and is laminated on the visual side of the image display unit via the first adhesive layer; and a third adhesive layer, which is arranged on the visual side of the first polarizing plate; the first polarizing plate has a special-shaped processed portion, and the special-shaped processed portion of the first polarizing plate is filled with an adhesive constituting the third adhesive layer, the thickness of the first polarizing plate is less than 90 μm, the thickness of the third adhesive layer is more than 170 μm, and the storage modulus of the third adhesive layer at 60°C is less than 8.0×10 ⁴ Pa. In one embodiment, the irregularly shaped processed portion of the first polarizing plate has an adhesive gap portion, which is formed by the end face of the first adhesive layer being located at a position closer to the inside in the surface direction than the end face of the first polarizing plate, and the size of the adhesive gap portion is less than 300 μm. In one embodiment, the thickness of the first adhesive layer is less than 50 μm. In one embodiment, the bonding force between the first adhesive layer and the third adhesive layer is greater than 2 N/25 mm. In one embodiment, the gel fraction of the third adhesive layer is less than 80%. In one embodiment, the irregularly shaped processed portion includes a through hole or a cutting processed portion that is a recessed portion when viewed from above. In one embodiment, the recess is a V-shaped recess or a U-shaped recess. In one embodiment, the image display device has a cover glass on the visual side of the third adhesive layer. In one embodiment, the image display device has a camera at a position corresponding to the irregularly processed portion of the first polarizing plate and the second polarizing plate. In one embodiment, the image display device is a liquid crystal display device. In another embodiment, the image display device is an organic EL (Electroluminescence) display device. In one embodiment, the organic EL display device has a camera at a position corresponding to the irregularly processed portion of the first polarizing plate. According to another aspect of the present invention, a set of optical components is provided. The optical component set includes: a first polarizing plate, which includes a first polarizing element and a first adhesive layer, has a thickness of 90 μm or less, has a special-shaped processing portion, and is arranged on the visual side of the image display unit; and an adhesive sheet, which is composed of an adhesive having a storage modulus of 8.0×10 ⁴ Pa or less at 60°C, has a thickness of 200 μm or more, and fills the special-shaped processing portion of the first polarizing plate. In one embodiment, the special-shaped processing portion of the first polarizing plate has an adhesive gap portion, which is formed by the end face of the first adhesive layer being located at a position closer to the inner side of the end face of the first polarizing plate in the surface direction, and the size of the adhesive gap portion is 300 μm or less. In one embodiment, the optical component set further includes a second polarizing plate, the second polarizing plate includes a second polarizing element, has a special-shaped processing portion, and is arranged on the back side of the image display unit, and the first polarizing plate and the second polarizing plate have special-shaped processing portions at positions corresponding to each other. [Effects of the Invention]

According to the implementation method of the present invention, in an image display device in which an irregularly shaped processed portion is filled with an adhesive, by setting the thickness of the polarizing plate on the viewing side and the thickness and storage modulus of the adhesive layer on the viewing side within a specific range, an image display device in which bubbles are significantly suppressed can be realized.

The following describes the specific implementation of the present invention with reference to the drawings, but the present invention is not limited to the implementation. Furthermore, the drawings are schematically drawn for the convenience of observation, and the ratios of length, width, thickness, etc., and angles in the drawings are different from the actual ones.

A. Overall Structure of Image Display Device FIG1 is a schematic exploded perspective view of an image display device of one embodiment of the present invention; FIG2 is a schematic cross-sectional view of a through hole portion of the image display device of FIG1 . The image display device 200 shown in the figure has: an image display unit 100; a first polarizing plate 10, which is laminated on the visual side of the image display unit 100; a second polarizing plate 20, which is laminated on the back side of the image display unit 100; and a third adhesive layer 30, which is disposed on the visual side of the first polarizing plate 10. In one embodiment, the image display device 200 may have a cover glass 40 on the visual side of the third adhesive layer 30. That is, the cover glass 40 can be bonded to the first polarizing plate 10 via the third adhesive layer 30. The first polarizing plate 10 has: a first polarizing element 11; a protective layer (outer protective layer) 12, which is arranged on the viewing side of the first polarizing element 11; a protective layer (inner protective layer) 13, which is arranged on the image display unit 100 side of the first polarizing element 11; and a first adhesive layer 14, which is arranged as the outermost layer on the image display unit side. The first polarizing plate 10 is laminated on the image display unit 100 via the first adhesive layer 14. Depending on the purpose, one of the protective layers 12 and 13 can be omitted. The second polarizing plate 20 has: a second polarizing element 21; a protective layer (external protective layer) 22, which is arranged on the back side of the second polarizing element 21; a protective layer (internal protective layer) 23, which is arranged on the image display unit 100 side of the second polarizing element 21; and a second adhesive layer 24, which is arranged as the outermost layer on the image display unit side. The second polarizing plate 20 is laminated on the image display unit 100 via the second adhesive layer 24. Depending on the purpose, one of the protective layers 22 and 23 can be omitted. Typically, the first polarizing plate 10 and the second polarizing plate 20 are arranged so that the absorption axis _A1 of the first polarizing element 11 and the absorption axis _A2 of the second polarizing element 21 are substantially orthogonal. In the illustrated example, _A1 is the long side direction and _A2 is the short side direction, but these may also be reversed. Furthermore, the so-called "substantially orthogonal" in this specification includes the case where the angle formed by the two directions is 90°±7°, preferably 90°±5°, and more preferably 90°±3°. The so-called "substantially parallel" includes the case where the angle formed by the two directions is 0°±7°, preferably 0°±5°, and more preferably 0°±3°. Furthermore, when simply referred to as "orthogonal" or "parallel" in this specification, it includes the case of "substantially orthogonal" or "substantially parallel". Furthermore, when angles are mentioned in this specification, they include both clockwise rotation and counterclockwise rotation relative to a reference direction.

The first polarizing plate 10 has a special-shaped processed portion 15, and the second polarizing plate 20 has a special-shaped processed portion 25. The first polarizing plate 10 and the second polarizing plate 20 have the special-shaped processed portions 15 and 25 at positions corresponding to each other. Typically, the special-shaped processed portion 15 of the first polarizing plate 10 is filled with an adhesive constituting the third adhesive layer 30. "Disposed at positions corresponding to each other" in this specification means that the special-shaped processed portions overlap when the two polarizing plates are overlapped. In addition, the "special-shaped processed portion" in this specification refers to a portion processed into a special shape different from a normal shape (e.g., a rectangle, a chamfered corner). As shown in FIG3 and FIG4, as representative examples of the irregularly shaped processed portion, there can be cited a through hole and a cutting processed portion that is a recessed portion when viewed from above. As representative examples of the recessed portion, there can be cited a shape similar to a boat shape, a V-shaped notch, and a U-shaped notch. Furthermore, the first polarizing plate and the second polarizing plate can also be irregularly processed as a whole. As such an example, as shown in FIG5 and FIG6, there can be cited a shape corresponding to a car dashboard. In this shape, the outer edge is formed into an arc shape along the rotation direction of the instrument needle, and the outer edge includes a portion formed into a V-shape (including an arc shape) that bulges inwardly in the surface direction. The irregularly shaped processed portion can be set at any appropriate position according to purpose. Typically, the irregularly shaped processed portion is disposed at or near the end of each polarizing plate. With this configuration, the effect on the image display can be minimized. For example, as shown in FIG4 , the irregularly shaped processed portion may be disposed at the approximate center of the end of the long side direction of the rectangular polarizing plate, or may be disposed at a specific position of the end of the long side direction, or may be disposed at a corner of the polarizing plate. In the example shown in the figure, the irregularly shaped processed portion is disposed at the end in the long side direction, but the irregularly shaped processed portion may also be disposed at the end in the short side direction. Furthermore, as shown in the lower right corner of FIG4 , a plurality of irregularly shaped processed portions may also be disposed. For example, more than two through holes and/or notches may be disposed, or a through hole and a notch may be disposed in combination as shown in FIG4 .

The image display device includes an image display panel. The image display panel includes an image display unit. The image display device is sometimes called an optical display device. The image display panel is sometimes called an optical display panel. The image display unit is sometimes called an optical display unit.

As representative examples of the image display unit 100, a liquid crystal unit, an organic electroluminescent (EL) unit, and a quantum dot unit can be cited. Therefore, as representative examples of the image display device 200, a liquid crystal display device, an organic EL display device, and a quantum dot display device can be cited. The illustrated example representatively shows the structure of a liquid crystal display device. In a liquid crystal display device, the effect produced by the combination of the first polarizing plate and the second polarizing plate is more significant. In an organic EL display device, the second polarizing plate 20 can be omitted. In one embodiment, the image display device 200 has a camera unit (not shown) at a position corresponding to the irregularly shaped processing parts 15 and 25.

In the embodiment of the present invention, the thickness of the first polarizing plate 10 is less than 90 μm, preferably less than 60 μm, more preferably less than 50 μm, and further preferably less than 40 μm. The lower limit of the thickness of the first polarizing plate may be, for example, 20 μm. Furthermore, the thickness of the third adhesive layer 30 is greater than 170 μm, preferably greater than 200 μm, more preferably greater than 220 μm, and further preferably greater than 240 μm. The upper limit of the thickness of the third adhesive layer may be, for example, 500 μm. In addition, the storage modulus of the third adhesive layer 30 at 60°C is less than 8.0×10 ⁴ Pa, preferably less than 5.0×10 ⁴ Pa, more preferably less than 3.0×10 ⁴ Pa, and further preferably less than 2.0×10 ⁴ Pa. The lower limit of the storage modulus can be, for example, 1.0×10 ³ Pa. By setting such a structure, bubbles can be significantly suppressed in an image display device in which a special-shaped processed part is filled with an adhesive. In particular, the generation of bubbles of so-called delayed bubbles can be significantly suppressed. The details are as follows. With regard to filling the special-shaped processed part with the adhesive constituting the third adhesive layer, it is typically performed by laminating a laminate of a cover glass and an adhesive sheet constituting the third adhesive layer to the first polarizing plate using vacuum lamination. In most cases, there are no identifiable bubbles in the filled portion immediately after vacuum lamination. On the other hand, bubbles may be generated during the subsequent heat durability test of the image display device. A typical cause of such bubbles may be that the contraction stress of the polarizing plate is applied to the filled portion. Such bubbles are called delayed bubbles. Delayed bubbles are large bubbles that occupy a certain percentage or more of the top view area of the irregularly processed portion, and are not fine bubbles. Bubbles are not allowed to exist from the perspective of appearance or from the perspective of the camera performance of the imaging portion located at a position corresponding to the irregularly processed portion. It is speculated that by setting the structure as described above, the residual stress of the filling part can be alleviated, and the deformation of the adhesive caused by heating, etc. can be suppressed, and as a result, delayed bubbles can be suppressed. Furthermore, by thinning the polarizing plate as described above and using the visual side adhesive layer having the thickness and storage modulus as described above, the following secondary effects can be achieved in the manufacturing steps of image display devices (such as smart phones): by setting the storage modulus of the visual side adhesive layer within the above range, it is possible to prevent the generation of dents, the overflow of the adhesive from the end of the punched product, and poor operation. In addition, when using thick polarizing plates, it is sometimes necessary to heat and shrink the polarizing plates before attaching them to the image display unit to reduce shrinkage during the heat durability test. This shrinkage reduction process not only reduces productivity, but sometimes also causes dimensional changes and curling. By making the polarizing plates thinner, these problems can be avoided.

As shown in FIG. 7 , in one embodiment, the irregularly shaped processed portion 15 of the first polarizing plate 10 has an adhesive gap portion 16, which is formed by the end face of the first adhesive layer 14 being located at a position closer to the inside of the surface direction than the end face of the first polarizing plate (substantially the polarizing element 11 or the inner protective layer 13 that may exist). The size L of the adhesive gap portion is preferably 300 μm or less, more preferably 200 μm or less, further preferably 150 μm or less, particularly preferably 100 μm or less, and extremely preferably 80 μm or less. The lower limit of the size L of the adhesive gap portion may be, for example, 10 μm. In this specification, the "size L of the adhesive gap" refers to the maximum length from the end surface of the first polarizing plate (actually the polarizing element 11 or the inner protective layer 13 that may exist) to the end surface of the adhesive layer 14.

According to the structure of the image display unit 100, the image display device 200 may also have a backlight unit (not shown). The backlight unit may adopt a structure known in the industry, so a detailed description is omitted.

A phase difference layer (not shown) may be provided in the image display device 200 as needed. The type, quantity, combination, configuration position, and characteristics of the phase difference layer may be set as appropriate according to the purpose. For example, the phase difference layer may be a λ/2 plate, a λ/4 plate, or a laminate thereof. The λ/2 plate and the λ/4 plate typically have a refractive index characteristic of nx＞ny≧nz. The in-plane phase difference Re(550) of the λ/2 plate is preferably 180 nm to 320 nm, and the in-plane phase difference Re(550) of the λ/4 plate is preferably 100 nm to 200 nm. In addition, for example, the phase difference layer may be a laminate of a negative B plate (nx＞ny＞nz) and a positive C plate (nz＞nx＝ny) or a positive B plate (nz＞nx＞ny). Furthermore, in this specification, "Re(λ)" is the in-plane phase difference measured at 23°C using light of a wavelength of λ nm. For example, "Re(550)" is the in-plane phase difference measured at 23°C using light of a wavelength of 550 nm. When the thickness of the layer (film) is set to d(nm), Re(λ) is calculated by the formula: Re(λ)＝(nx－ny)×d. "Rth(λ)" is the phase difference in the thickness direction measured at 23°C using light of a wavelength of λ nm. For example, "Rth(550)" is the phase difference in the thickness direction measured at 23°C using light of a wavelength of 550 nm. When the thickness of the layer (film) is set to d(nm), Rth(λ) is calculated by the formula: Rth(λ)＝(nx－nz)×d. "nx" is the refractive index in the direction where the refractive index in the plane is maximum (i.e., the direction of the latent axis), "ny" is the refractive index in the direction orthogonal to the latent axis in the plane (i.e., the direction of the advanced axis), and "nz" is the refractive index in the thickness direction.

Optical components (not shown) may also be provided in the image display device 200 as needed. The type, quantity, combination, configuration position, and characteristics of the optical components may be set as appropriate according to the purpose. For example, a reflective polarizing element, a prism sheet, and/or a diffusion plate may be provided on the back side of the second polarizing plate. The reflective polarizing element may also serve as an outer protective layer of the second polarizing plate.

The components of the image display device are described in detail below. Furthermore, the first polarizing plate and the second polarizing plate are collectively referred to as polarizing plates, the first polarizing element and the second polarizing element are collectively referred to as polarizing elements, the protective layers in the first polarizing plate and the second polarizing plate are collectively referred to as protective layers, and the first adhesive layer and the second adhesive layer are collectively referred to as adhesive layers for description. Therefore, for example, when it is recorded as "polarizing plate...", it may mean "the first polarizing plate and the second polarizing plate, respectively...". On the other hand, for example, when it is necessary to describe the first polarizing plate and the second polarizing plate separately, it is clearly recorded as "the first" or "the second". Furthermore, the cover glass can adopt a structure well known in the industry, so the detailed description is omitted.

B. Polarizing plate B-1. Polarizing element The polarizing element is typically composed of a resin film containing a dichroic substance. As the resin film, any suitable resin film that can be used as a polarizing element can be used. The resin film is typically a polyvinyl alcohol resin (hereinafter referred to as "PVA (Poly Vinyl Alcohol, polyvinyl alcohol) resin") film. The resin film may be a single-layer resin film or a laminate of two or more layers.

As a specific example of a polarizing element composed of a single-layer resin film, there can be cited a PVA-based resin film that has been subjected to a dyeing treatment using iodine and a stretching treatment (typically uniaxial stretching). The above-mentioned dyeing using iodine is performed, for example, by immersing the PVA-based film in an iodine aqueous solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. Stretching can be performed after the dyeing treatment, or it can be performed while dyeing. In addition, dyeing can also be performed after stretching. If necessary, the PVA-based resin film is subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, etc. For example, by immersing the PVA-based resin film in water and washing it before dyeing, not only can the dirt and anti-adhesive agent on the surface of the PVA-based resin film be washed away, but the PVA-based resin film can also be swollen to prevent uneven dyeing.

As specific examples of polarizing elements obtained using a laminate, there can be cited a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. The polarizing element obtained by using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced, for example, by the following steps: coating a PVA-based resin solution on the resin substrate, drying the PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer; and stretching and dyeing the laminate to make the PVA-based resin layer into a polarizing element. In this embodiment, the stretching typically includes a step of immersing the laminate in a boric acid aqueous solution for stretching. Furthermore, stretching may include, if necessary, a step of stretching the laminate in the air at a high temperature (e.g., above 95° C.) before stretching in a boric acid aqueous solution. The obtained laminate of the resin substrate/polarizing element may be used directly (i.e., the resin substrate may be used as a protective layer of the polarizing element), or the resin substrate may be peeled off from the laminate of the resin substrate/polarizing element, and any suitable protective layer corresponding to the purpose may be laminated on the peeled surface for use. The details of the method for manufacturing such a polarizing element are described, for example, in Japanese Patent Publication No. 2012-73580 and Japanese Patent No. 6470455. The entire contents of the publication are cited in this specification as a reference.

The thickness of the polarizing element is preferably 25 μm or less, more preferably 12 μm or less, and further preferably 8 μm or less. On the other hand, the thickness of the polarizing element is 1 μm or more in one embodiment, 2 μm or more in another embodiment, and 3 μm or more in another embodiment. If the thickness of the polarizing element is within this range, curling during heating can be well suppressed, and good appearance durability during heating can be obtained. In particular, if the thickness of the first polarizing element is within this range, it is easy to set the thickness of the first polarizing plate within the above-mentioned desired range.

The polarizing element preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizing element is, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, and more preferably 44.5% to 46.0%. The polarization degree of the polarizing element is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more.

B-2. Protective layer The protective layer is formed of any suitable film that can be used as a protective layer for a polarizing element. Specific examples of the material that is the main component of the film include cellulose resins such as triacetylcellulose (TAC), or transparent resins such as polyester, polyvinyl alcohol, polycarbonate, polyamide, polyimide, polyether sulfone, polysulfone, polystyrene, polybutylene, polyolefin, (meth)acrylic, and acetate. In addition, thermosetting resins or ultraviolet curing resins such as (meth)acrylic, urethane, (meth)acrylic urethane, epoxy, and silicone can also be cited. In addition, for example, glassy polymers such as siloxane polymers can also be cited. In addition, the polymer film described in Japanese Patent Publication No. 2001-343529 (WO01/37007) can also be used. As the material of the film, for example, a resin composition containing two thermoplastic resins can be used, one of which has a substituted or unsubstituted imine group in the side chain, and the other thermoplastic resin has a substituted or unsubstituted phenyl and nitrile group in the side chain, for example, a resin composition having an alternating copolymer containing isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer can be cited. The polymer film can be, for example, an extruded product of the above resin composition.

If necessary, the outer protective layer (especially the outer protective layer 12 of the first polarizing plate) may be subjected to surface treatments such as hard coating, anti-reflection, anti-sticking, and anti-glare.

The inner protective layer is preferably optically isotropic. The term "optically isotropic" in this specification means that the in-plane phase difference Re(550) is 0 nm to 10 nm and the phase difference Rth(550) in the thickness direction is -10 nm to +10 nm.

The thickness of the protective layer can be any appropriate thickness. The thickness of the protective layer is, for example, 15 μm to 45 μm, preferably 20 μm to 40 μm. Furthermore, when surface treatment is performed, the thickness of the protective layer includes the thickness of the surface treatment layer.

C. Adhesive layer The adhesive layer is typically used to attach each polarizing plate to the image display unit. The adhesive layer is typically composed of an acrylic adhesive (acrylic adhesive composition). The acrylic adhesive composition typically contains a (meth)acrylic polymer as a base polymer. The (meth)acrylic polymer can be contained in the adhesive composition in a ratio of, for example, 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more in the solid content of the adhesive composition. The (meth)acrylic polymer contains an alkyl (meth)acrylate as a main component in the form of a monomer unit. Furthermore, (meth)acrylate refers to acrylate and/or methacrylate. The alkyl (meth)acrylate may be contained in the (meth)acrylate polymer in a ratio of preferably 70% by weight or more, more preferably 80% by weight or more, in the monomer components forming the (meth)acrylate polymer. As the alkyl group of the alkyl (meth)acrylate, for example, a linear or branched alkyl group having 1 to 18 carbon atoms may be cited. The average carbon number of the alkyl group is preferably 3 to 9, more preferably 3 to 6. Specific examples of the alkyl (meth)acrylate include methyl acrylate, methyl methacrylate, butyl acrylate, and 2-ethylhexyl acrylate. As monomers (comonomers) constituting (meth)acrylic polymers, in addition to (meth)acrylic acid alkyl esters, carboxyl-containing monomers, hydroxyl-containing monomers, amide-containing monomers, multifunctional (meth)acrylates, aromatic ring-containing (meth)acrylates, heterocyclic vinyl monomers, etc. can be cited. As representative examples of comonomers, acrylic acid, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, phenoxyethyl acrylate, N-vinyl-2-pyrrolidone, and N-acryloyl phenoxyphenol can be cited. The acrylic adhesive composition preferably contains a silane coupling agent and/or a crosslinking agent. As a silane coupling agent, for example, an epoxy-containing silane coupling agent can be cited. As crosslinking agents, for example, isocyanate crosslinking agents and peroxide crosslinking agents can be cited. The acrylic adhesive composition can also contain additives. As specific examples of additives, colorants, pigment powders, dyes, surfactants, plasticizers, adhesion-imparting agents, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, conductive agents, inorganic or organic fillers, metal powders, and granular or foil-shaped objects can be cited. In addition, redox additives with reducing agents added can also be used within a controllable range. The type, amount, combination, and blending amount of the additives can be set as appropriate according to the purpose. By appropriately adjusting the type, combination, and blending amount of the monomer components, as well as the type, amount, combination, and blending amount of the crosslinking agent, silane coupling agent, and additives, an acrylic adhesive composition (resulting in an adhesive layer) having the desired properties corresponding to the purpose can be obtained. The details of the adhesive layer or the acrylic adhesive composition are described, for example, in Japanese Patent Laid-Open No. 2006-183022, Japanese Patent Laid-Open No. 2015-199942, Japanese Patent Laid-Open No. 2018-053114, Japanese Patent Laid-Open No. 2016-190996, and International Publication No. 2018/008712, and the descriptions of these publications are cited in this specification as references.

The thickness of the adhesive layer is preferably 50 μm or less, more preferably 40 μm or less, further preferably 30 μm or less, and particularly preferably 25 μm or less. The lower limit of the thickness of the adhesive layer may be, for example, 2 μm. If the thickness of the adhesive layer is within this range, it can contribute to the thinning of the image display device. In particular, if the thickness of the first adhesive layer is within this range, it is easy to fill the irregularly shaped processed portion with the adhesive constituting the third adhesive layer. More specifically, since the depth of the irregularly shaped processed portion becomes smaller, it is easy to fill it with the adhesive. As a result, since the gap in the irregularly shaped processed portion becomes smaller, it is not easy to generate bubbles due to deformation of the adhesive. As a result, if the thickness of the first adhesive layer is within this range, it can help delay the suppression of bubbles.

The adhesive force between the adhesive constituting the adhesive layer (especially the first adhesive layer) and the adhesive constituting the third adhesive layer is preferably 2 N/25 mm or more, more preferably 5 N/25 mm or more, and further preferably 10 N/25 mm or more. The upper limit of the adhesive force may be, for example, 50 N/25 mm. As shown in FIG. 2 , the first adhesive layer and the third adhesive layer can be in contact, and if the adhesive force is large, the first adhesive layer and the third adhesive layer are not easy to peel off even if the adhesive is deformed. As a result, it is difficult to form a gap in the irregularly processed portion, thereby suppressing delayed bubbles. Furthermore, the adhesion force can be measured according to the "90 degree peel strength test" of JIS Z 0237.

D. Third Adhesive Layer D-1. Characteristics of the Third Adhesive Layer The third adhesive layer 30 is typically used to fill the irregularly shaped portion 15 of the first polarizing plate 10 as described in item A above. In addition to the thickness and storage modulus described in item A above, the third adhesive layer may also have the following characteristics.

The gel fraction of the third adhesive layer is preferably 80% or less, more preferably 70% or less, further preferably 60% or less, and particularly preferably 50% or less. The lower limit of the gel fraction may be, for example, 20%. Thus, the gel fraction of the third adhesive layer is significantly smaller than the gel fraction of a common adhesive. As a result, the gel elasticity of the third adhesive is reduced and the residual stress is reduced. As a result, delayed bubbles can be suppressed. The gel fraction can be obtained in the form of an insoluble fraction relative to a solvent such as ethyl acetate. Specifically, the gel fraction is obtained as the weight fraction (unit: weight %) of the insoluble components of the adhesive constituting the adhesive layer after immersion in ethyl acetate at 23°C for 7 days relative to the sample before immersion. The gel fraction can be adjusted by appropriately setting the type, combination and blending amount of the monomer components of the base polymer constituting the adhesive, and the type and blending amount of the crosslinking agent.

The weight average molecular weight of the sol component of the third adhesive layer is preferably 150,000 to 450,000, more preferably 180,000 to 420,000. The sol component is a soluble fraction obtained by extracting the base polymer using tetrahydrofuran (THF). If the weight average molecular weight of the sol component is within this range, an adhesive layer with excellent balance between impact resistance and adhesion retention can be obtained.

The loss tangent tanδ _{70 ℃} of the third adhesive layer at 70 ℃ is preferably 0.25 or more, more preferably 0.30 or more, and further preferably 0.35 or more. On the other hand, tanδ _{70 ℃} is preferably 1.0 or less, more preferably 0.9 or less, and further preferably 0.85 or less. The peak value of tanδ of the third adhesive layer is preferably 1.5 or more, more preferably 1.6 or more, and further preferably 1.7 or more. The upper limit of the peak value may be 3.0, for example. If tanδ _{70 ℃} and the peak value are within this range, the third adhesive layer exhibits appropriate deformation behavior (viscoelastic behavior), so that gaps are not easily formed in the irregularly processed portion, thereby suppressing delayed bubbles.

The glass transition temperature of the third adhesive layer is preferably -3°C or lower, more preferably -4°C or lower. On the other hand, the glass transition temperature is preferably -20°C or higher, more preferably -15°C or higher, and further preferably -13°C or higher.

D-2. Constituent materials of the third adhesive The third adhesive layer can be composed of any appropriate adhesive composition as long as it has the properties as described above. As the base polymer of the adhesive composition, for example, there can be cited (meth)acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyvinyl ethers, vinyl acetate/vinyl chloride copolymers, modified polyolefins, epoxy polymers, fluorine polymers, natural rubbers, synthetic rubbers and other rubber polymers. Preferably, the acrylic adhesive composition includes a (meth)acrylic polymer as the base polymer. The reason is that (meth)acrylic polymers have excellent optical transparency, exhibit appropriate adhesive properties such as wettability, cohesion and adhesion, and are also excellent in weather resistance and heat resistance.

The (meth)acrylic polymer preferably has a cross-linked structure. More specifically, the (meth)acrylic polymer comprises a (meth)acrylic polymer chain having a cross-linked structure.

D-2-1. (Meth)acrylic acid polymer chain The (meth)acrylic acid polymer contains an alkyl (meth)acrylate as a main monomer component. As the alkyl (meth)acrylate, an alkyl (meth)acrylate having an alkyl group with a carbon number of 1 to 20 is preferably used. The alkyl (meth)acrylate may have a branched alkyl group or a cyclic alkyl group. The amount of the alkyl (meth)acrylate relative to the total amount of the monomer components constituting the (meth)acrylic acid polymer chain is preferably 50% by weight or more, more preferably 55% by weight or more, and further preferably 60% by weight or more. In order to set the glass transition temperature (Tg) of the polymer chain within an appropriate range, the amount of the (meth)acrylic acid alkyl ester having a chain alkyl group with 4 to 10 carbon atoms is preferably 40% by weight or more, more preferably 50% by weight or more, and further preferably 55% by weight or more relative to the total amount of monomer components constituting the (meth)acrylic polymer chain. Furthermore, the monomer components constituting the (meth)acrylic polymer chain refer to the monomer components other than the monomers for forming the crosslinking structure (the following multifunctional (meth)acrylate, (meth)acrylic urethane, etc.) and the crosslinking agent among all the monomer components constituting the polymer.

The (meth)acrylic polymer may contain a hydroxyl group-containing monomer and/or a carboxyl group-containing monomer as a monomer component. When the crosslinking structure is introduced by an isocyanate crosslinking agent, the hydroxyl group becomes a reaction point with the isocyanate group, and when the crosslinking structure is introduced by an epoxy crosslinking agent, the carboxyl group becomes a reaction point with the epoxy group. When the crosslinking structure composed of a urethane chain segment is introduced into the acrylic polymer chain, in order to make the compatibility with the urethane chain segment higher and improve the transparency of the third adhesive layer, the (meth)acrylic polymer preferably contains a (meth)acrylate having a hydroxyl group with a carbon number of 4 to 8 as a monomer component.

The amount of the hydroxyl-containing monomer is preferably 5% to 30% by weight, more preferably 8% to 25% by weight, and even more preferably 10% to 20% by weight relative to the total amount of monomer components constituting the (meth)acrylic polymer chain.

In the case where the third adhesive layer may be in contact with a touch panel sensor, for example, the acid content in the third adhesive layer is preferably small in order to prevent electrode corrosion caused by acid components. In this case, the amount of carboxyl-containing monomers relative to the total amount of monomer components constituting the (meth)acrylic acid polymer chain is preferably 0.5 wt % or less, more preferably 0.1 wt % or less, further preferably 0.05 wt % or less, and ideally 0 (zero).

(Meth)acrylic polymers may also contain nitrogen-containing monomers as monomer components. By appropriately containing highly polar monomers such as hydroxyl-containing monomers, carboxyl-containing monomers, and nitrogen-containing monomers as monomer components, an adhesive layer having an excellent balance of storage modulus, adhesion retention, and impact resistance can be formed in the (meth)acrylic polymer. The amount of highly polar monomers (the sum of hydroxyl-containing monomers, carboxyl-containing monomers, and nitrogen-containing monomers) relative to the total amount of monomer components constituting the (meth)acrylic polymer chain is preferably 15% to 45% by weight, more preferably 20% to 40% by weight, and further preferably 25% to 37% by weight. It is particularly preferred that the sum of hydroxyl-containing monomers and nitrogen-containing monomers is within the above range. The amount of the nitrogen-containing monomer is preferably 7 wt % to 30 wt %, more preferably 10 wt % to 25 wt %, and even more preferably 12 wt % to 22 wt % relative to the total amount of monomer components constituting the (meth)acrylic acid polymer chain.

The (meth)acrylic polymer may further contain any appropriate monomer component according to the purpose. Specific examples of such monomer components include: monomers containing anhydride groups, caprolactone adducts of (meth)acrylic acid, monomers containing sulfonic acid groups, monomers containing phosphoric acid groups, vinyl monomers such as vinyl acetate, vinyl propionate, styrene, and α-methylstyrene; acrylic monomers containing cyano groups such as acrylonitrile and methacrylonitrile; monomers containing epoxy groups such as glycidyl (meth)acrylate; glycol acrylate monomers such as polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate; and acrylate monomers such as tetrahydrofuran methyl (meth)acrylate, fluoro (meth)acrylate, silicone (meth)acrylate, and 2-methoxyethyl (meth)acrylate.

The (meth)acrylic polymer preferably contains the most alkyl (meth)acrylate as a monomer component, and more preferably contains the most alkyl (meth)acrylate having a chain alkyl group with a carbon number of 6 or less. The amount of the alkyl (meth)acrylate having a chain alkyl group with a carbon number of 6 or less is preferably 40% to 85% by weight, more preferably 45% to 80% by weight, and further preferably 50% to 75% by weight relative to the total amount of monomer components constituting the (meth)acrylic polymer chain. It is particularly preferred that the content of butyl acrylate as a monomer component is within the above range.

D-2-2. Crosslinking structure The polymer having a crosslinking structure introduced into the (meth)acrylic polymer chain is obtained, for example, by the following methods: (1) after polymerizing a (meth)acrylic polymer having a functional group that can react with a crosslinking agent, a crosslinking agent is added to react the (meth)acrylic polymer with the crosslinking agent; and (2) by including a multifunctional compound in the polymerization components of the polymer, a branched structure (crosslinking structure) is introduced into the polymer chain. These methods may also be used in combination.

Specific examples of the crosslinking agent in the method of reacting the base polymer with the crosslinking agent in (1) above include isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, carbodiimide crosslinking agents, metal chelate crosslinking agents, etc. Among them, isocyanate crosslinking agents and epoxy crosslinking agents are preferred in order to make the base polymer more reactive with hydroxyl or carboxyl groups so as to easily introduce a crosslinking structure. These crosslinking agents react with functional groups such as hydroxyl or carboxyl groups introduced into the base polymer to form a crosslinking structure.

In the method of (2) above, in which a polyfunctional compound is included in the polymerization component of the base polymer, all monomer components constituting the (meth)acrylic polymer and the polyfunctional compound used to introduce the cross-linking structure may be reacted at once, or the polymerization may be carried out in multiple stages. As a method of carrying out the polymerization in multiple stages, the following method is preferred: a monofunctional monomer constituting the (meth)acrylic polymer is polymerized (prepolymerization) to prepare a partial polymer (prepolymer composition), and a polyfunctional compound such as a polyfunctional (meth)acrylate is added to the prepolymer composition, and the prepolymer composition and the polyfunctional monomer are polymerized (formal polymerization). The prepolymer composition includes a polymer with a low degree of polymerization and a partial polymer of unreacted monomers.

By prepolymerizing the constituents of the (meth)acrylic polymer, branching points (crosslinking points) based on the multifunctional compound can be uniformly introduced into the (meth)acrylic polymer. In addition, after coating a low molecular weight polymer or a mixture of a partial polymer and unpolymerized monomer components (adhesive composition) on a substrate, a formal polymerization can be performed on the substrate to form an adhesive layer. Since low polymer compositions such as prepolymer compositions have low viscosity and excellent coating properties, the productivity of the adhesive layer can be improved and the thickness of the adhesive layer can be made uniform by coating an adhesive composition that is a mixture of a prepolymer composition and a multifunctional compound and then performing a formal polymerization on a substrate.

As a polyfunctional compound for introducing a crosslinked structure, a compound having two or more polymerizable functional groups (ethylenic unsaturated groups) having unsaturated double bonds in one molecule can be cited. As a polyfunctional compound, a polyfunctional (meth)acrylate is preferred in order to facilitate copolymerization with the monomer component of the (meth)acrylic polymer. In the case of introducing a branched (crosslinked) structure by active energy line polymerization (photopolymerization), a polyfunctional (meth)acrylate is preferred. In addition, by using a (meth)acrylic urethane having a (meth)acrylic group at the end of the urethane chain as a polyfunctional (meth)acrylate, a crosslinked structure consisting of a urethane tether segment can be introduced.

D-2-3. Introduction of cross-linked structures formed by urethane tethers By cross-linking (meth)acrylic polymer chains by using urethane tethers, an adhesive having both low glass transition temperature and high adhesive retention can be easily obtained. Urethane tethers are molecular chains having urethane bonds. The cross-linked structures formed by urethane tethers are introduced into (meth)acrylic polymer chains by covalently bonding the two ends of the urethane tethers to the (meth)acrylic polymer chains. The urethane tethers are typically polyurethane chains obtained by reacting diols with diisocyanates.

The molecular weight of the polyurethane chain in the urethane tether segment is preferably 5000-30000, more preferably 6000-23000, and further preferably 7000-20000. The greater the molecular weight of the polyurethane chain in the urethane tether segment, the longer the distance between the crosslinking points of the (meth)acrylic polymer chain. If the molecular weight of the polyurethane chain is within the above range, the polymer introduced with the crosslinking structure has appropriate cohesion and fluidity, so it can have both adhesion and step absorption and impact resistance.

The amount of the urethane tether segment in the (meth)acrylic polymer is preferably 10 parts by weight or less, more preferably 7 parts by weight or less, and further preferably 5 parts by weight or less, relative to 100 parts by weight of the acrylic polymer chain. On the other hand, the amount of the urethane tether segment is preferably 0.3 parts by weight or more, more preferably 0.4 parts by weight or more, and further preferably 0.5 parts by weight or more, relative to 100 parts by weight of the acrylic polymer chain. If the amount of the urethane tether segment is within this range, an adhesive layer having an excellent balance of impact resistance, transparency, and adhesion retention can be obtained.

Examples of the diol used to form the polyurethane chain include low molecular weight diols such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, and hexanediol; and high molecular weight polyols such as polyester polyols, polyether polyols, polycarbonate polyols, acrylic polyols, epoxy polyols, and caprolactone polyols.

The diisocyanate used to form the polyurethane chain may be any of aromatic diisocyanate and aliphatic diisocyanate. Examples of the aromatic diisocyanate include 1,5-naphthalene diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 4,4'-diphenyldimethylmethane diisocyanate, tetramethyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2-chloro-1,4-phenyl diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, xylylene diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl sulfone diisocyanate, 4,4'-diphenyl sulfone diisocyanate, and 4,4'-biphenyl diisocyanate. Examples of the aliphatic diisocyanate include butane-1,4-diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, methylcyclohexane diisocyanate, etc. As the diisocyanate, derivatives of isocyanate compounds may also be used. Examples of derivatives of isocyanate compounds include dimers of polyisocyanate, trimers of isocyanate (isocyanurates), polymeric MDI (polymeric-MDI, polymethylene polyphenyl isocyanate), adducts with trihydroxymethylpropane, biuret modified products, allophanate modified products, urea modified products, etc. As a diisocyanate component, it can be used in urethane prepolymers having an isocyanate group at the end.

Among the exemplified polyurethane chains, in order to increase compatibility with the (meth)acrylic polymer chain, preferably, a polyether urethane containing a polyether polyol as a diol component and/or a polyester urethane containing a polyester polyol as a diol component is included.

By using a compound having a functional group capable of copolymerizing with a monomer component constituting a (meth)acrylic polymer chain at the end of a polyurethane chain, or by using a compound having a functional group capable of reacting with a carboxyl group, a hydroxyl group, etc. contained in a (meth)acrylic polymer chain at the end of a polyurethane chain, a cross-linked structure composed of a urethane tether segment can be introduced into a (meth)acrylic polymer chain. In order to easily and evenly introduce crosslinking points into the (meth)acrylic polymer chain and to make the (meth)acrylic polymer chain and the urethane tether segment have excellent compatibility, it is preferred to use di(meth)acrylic urethane having (meth)acrylic groups at both ends of the polyurethane chain to introduce the crosslinking structure formed by the urethane tether segment. For example, by copolymerizing the monomer component constituting the (meth)acrylic polymer chain with di(meth)acrylic urethane, the crosslinking structure formed by the urethane tether segment can be introduced into the (meth)acrylic polymer chain.

In one embodiment, the adhesive (adhesive composition) constituting the third adhesive layer has a thickness corresponding to the thickness of the third adhesive layer, and can be provided in the form of an adhesive sheet with release films temporarily adhered to both sides.

D-3. Other constituent materials Another example of an adhesive composition constituting the third adhesive layer is the adhesive composition described in Japanese Patent Publication No. 2016-94569. The description in the publication is incorporated into this specification as a reference.

E. Optical component kit As described in the above item D, the adhesive (adhesive composition) constituting the third adhesive layer can be provided in the form of an adhesive sheet. In the manufacture of the image display device, the adhesive sheet can be provided together with the first polarizing plate (viewing side polarizing plate) in the form of an optical component kit. Therefore, such an optical component kit is also included in the embodiment of the present invention. In one embodiment, the optical component kit can further include a second polarizing plate (back side polarizing plate). That is, in the manufacture of the image display device, the adhesive sheet, the first polarizing plate (viewing side polarizing plate) and the second polarizing plate (back side polarizing plate) can be provided in the form of an optical component kit. [Example]

The present invention is specifically described below by way of examples, but the present invention is not limited to these examples. The measuring methods of various characteristics in the examples are as follows.

(1) Thickness The thickness below 10 μm was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000"). The thickness exceeding 10 μm was measured using a digital micrometer (manufactured by Amway Corporation, product name "KC-351C"). (2) Gel fraction The adhesive constituting the third adhesive layer used in the examples and comparative examples was crosslinked and immersed in ethyl acetate at 23°C for 7 days, and the insoluble component was determined as the weight fraction (unit: weight %) of the sample before immersion. (3) Storage modulus For the adhesive constituting the third adhesive layer used in the embodiment and the comparative example, the storage modulus at 60°C was measured using the dynamic viscoelasticity measuring device "ARES" manufactured by Rheometrics based on JIS K 7244. (4) Size of adhesive gap The state of the cross section of the first adhesive layer in the irregularly processed portion of the first polarizing plate (viewing side polarizing plate) used in the embodiment and the comparative example was observed using an optical microscope, and the length of the largest missing portion of the adhesive layer from the outer edge to the inner side in the surface direction was measured and set as the size L (μm) of the adhesive gap. (5) Bubbles For the image display device counterparts obtained in the embodiment and the comparative example, the state of bubbles was observed by visual inspection or optical microscope at two time points: just after vacuum lamination and after the heating test (85°C, 24 h) after vacuum lamination, and evaluated according to the following criteria. In addition, bubbles were observed in any image display device counterpart in the stage before vacuum lamination (only the adhesive sheet was attached). 4: No bubbles were present immediately after vacuum lamination and after the heating test 3: Some bubbles were present immediately after vacuum lamination and after the heating test 2: Some bubbles were present immediately after vacuum lamination, and multiple bubbles were present after the heating test 1: Multiple bubbles were present immediately after vacuum lamination and after the heating test

<Production Example 1: Preparation of the adhesive constituting the first adhesive layer> A monomer mixture containing 80.3 parts of butyl acrylate (BA), 16 parts of phenoxyethyl acrylate (PEA), 3 parts of N-vinyl-2-pyrrolidone (NVP), 0.3 parts of acrylic acid (AA) and 0.4 parts of 4-hydroxybutyl acrylate (4HBA) was placed in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube and a cooler. Furthermore, 0.1 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator and 100 parts by weight of ethyl acetate were added to 100 parts of the monomer mixture (solid content), and nitrogen was introduced while slowly stirring to replace the nitrogen atmosphere. The polymerization reaction was then carried out for 8 hours while the liquid temperature in the flask was maintained at approximately 55°C, thereby preparing a solution of an acrylic polymer having a weight average molecular weight (Mw) of 1.56 million. To 100 parts of the solid content of the obtained acrylic polymer solution, 0.1 parts of an isocyanate crosslinking agent (trade name: Takenate D160N, trihydroxymethylpropane hexamethylene diisocyanate, manufactured by Mitsui Chemicals Co., Ltd.), 0.3 parts of benzoyl peroxide (trade name: Nyper BMT 40SV, manufactured by NOF Corporation), 0.3 parts of a thiol-containing silane coupling agent (trade name: X-41-1810, manufactured by Shin-Etsu Chemical Co., Ltd., alkoxy content: 30%, thiol equivalent: 450 g/mol), and 0.2 parts of an antioxidant (trade name: Irganox 1010, hindered phenol type, manufactured by BASF Japan) were prepared to obtain an adhesive composition a.

<Production Example 2: Preparation of an adhesive sheet constituting the third adhesive layer> After adding 0.05 parts by weight of a photopolymerization initiator (trade name "Irgacure 651", manufactured by BASF) and 0.5 parts by weight of a photopolymerization initiator (trade name "Irgacure 184", manufactured by BASF) to a monomer mixture containing 40.5 parts by weight of 2-ethylhexyl acrylate (2EHA), 40.5 parts by weight of isostearyl acrylate (ISTA), 18 parts by weight of N-vinyl-2-pyrrolidone (NVP), and 1 part by weight of 4-hydroxybutyl acrylate (4HBA), the mixture was irradiated with ultraviolet light until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30°C) reached about 20. Pa·s, thereby obtaining a prepolymer composition in which one part of the above monomer components is polymerized. 0.02 parts by weight of trihydroxymethylpropane triacrylate (TMPTA) and 0.3 parts by weight of a silane coupling agent (trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.) are mixed into the above prepolymer composition to obtain an acrylic adhesive composition. The above acrylic adhesive composition is coated on a polyethylene terephthalate (PET) release pad (manufactured by Nitto Denko Co., Ltd., thickness: 125 μm) to form an adhesive composition layer. Then, a PET-based peeling pad (manufactured by Nitto Denko Co., Ltd., thickness: 125 μm) was placed on the above-mentioned adhesive composition layer to cover the above-mentioned adhesive composition layer to block oxygen. In this way, a laminate having a structure of [peeling pad/adhesive composition layer/peeling pad] was obtained. Using a black light (manufactured by Toshiba Co., Ltd.), the upper surface (peeling pad side) of the laminate obtained in the above was irradiated with ultraviolet light with an illumination of 3 mW/ ^cm2 for 300 seconds. The adhesive sheet I with a thickness of 250 μm was obtained by drying in a 90°C dryer for 2 minutes to volatilize the residual monomer. The adhesive constituting the adhesive sheet I had a storage modulus of 1.9×10 ⁴ Pa at 60°C and a gel fraction of 40%.

<Production Example 3: Preparation of an adhesive sheet constituting the third adhesive layer> After adding 0.05 parts by weight of a photopolymerization initiator (trade name "Irgacure 651", manufactured by BASF) and 0.05 parts by weight of a photopolymerization initiator (trade name "Irgacure 184", manufactured by BASF) to a monomer mixture containing 78 parts by weight of 2-ethylhexyl acrylate (2EHA), 18 parts by weight of N-vinyl-2-pyrrolidone (NVP), and 4 parts by weight of 2-hydroxyethyl acrylate (HEA), the mixture was irradiated with ultraviolet light until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measuring temperature 30°C) reached about 20 Pa·s, thereby obtaining a prepolymer composition in which part of the above monomer components was polymerized. 18 parts by weight of 2-hydroxyethyl acrylate (HEA) and 0.3 parts by weight of a silane coupling agent (trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed into the above prepolymer composition to obtain an acrylic adhesive composition. The following sequence was the same as in Preparation Example 2 to obtain an adhesive sheet II with a thickness of 250 μm. The adhesive constituting the adhesive sheet II had a storage modulus of 8.6×10 ⁴ Pa at 60°C and a gel fraction of 85%.

<Production Example 4: Preparation of an adhesive sheet constituting the third adhesive layer> After adding 0.05 parts by weight of a photopolymerization initiator (trade name "Irgacure 651", manufactured by BASF) and 0.05 parts by weight of a photopolymerization initiator (trade name "Irgacure 184", manufactured by BASF) to a monomer mixture containing 57 parts by weight of n-butyl acrylate (BA), 12 parts by weight of cyclohexyl acrylate (CHA), 23 parts by weight of 4-hydroxybutyl acrylate (4HBA), and 8 parts by weight of 2-hydroxyethyl acrylate (HEA), the mixture was irradiated with ultraviolet light until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measuring temperature 30°C) reached about 20 Pa·s, thereby obtaining a prepolymer composition in which part of the above monomer components was polymerized. Dipentaerythritol hexaacrylate (DPHA): 0.1 parts by weight, and silane coupling agent (trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.): 0.3 parts by weight were mixed into the above prepolymer composition to obtain an acrylic adhesive composition. Using the above acrylic adhesive composition, an adhesive sheet III with a thickness of 250 μm was obtained in the same manner as in Production Example 2 except that a PET film (thickness: 100 μm, in-plane phase difference Re: 10000 nm) was used as the PET film. The adhesive constituting the adhesive sheet III had a storage modulus of 10.6×10 ⁴ Pa at 60°C and a gel fraction of 85%.

<Example 1> 1. Preparation of the first polarizing element As a thermoplastic resin substrate, a long strip of amorphous isophthalic acid-polyethylene terephthalate copolymer film (thickness: 100 μm) with a Tg of about 75°C was used. One side of the resin substrate was subjected to a corona treatment. Polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (Polyvinyl Alcohol, polyvinyl alcohol) (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z410") were mixed in a ratio of 9:1 to obtain a PVA resin. 13 parts by weight of potassium iodide was added to 100 parts by weight of the PVA resin to prepare a PVA aqueous solution (coating liquid). The PVA aqueous solution was applied to the corona treated surface of the resin substrate and dried at 60°C to form a PVA resin layer with a thickness of 13 μm, thereby producing a laminate. The laminate was stretched uniaxially to 2.4 times at the free end in the longitudinal direction (long side direction) between rollers of different peripheral speeds in an oven at 130°C (air-assisted stretching treatment). Thereafter, the laminate was immersed in an insolubilizing bath (a boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (insolubilizing treatment). Then, the dyeing bath (iodine aqueous solution obtained by mixing iodine and potassium iodide at a weight ratio of 1:7 relative to 100 parts by weight of water) with a liquid temperature of 30°C was immersed for 60 seconds (dyeing treatment) while adjusting the concentration so that the monomer transmittance (Ts) of the polarizing element finally obtained would be 43%. Then, it was immersed in a crosslinking bath (boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid relative to 100 parts by weight of water) with a liquid temperature of 40°C for 30 seconds (crosslinking treatment). Then, the laminate was immersed in a boric acid aqueous solution (boric acid concentration 4.0 wt%, potassium iodide 5.0 wt%) at a liquid temperature of 70°C, and uniaxially stretched in the longitudinal direction (long side direction) between rollers of different circumferential speeds at a total stretching ratio of 5.5 times (underwater stretching treatment). Then, the laminate was immersed in a cleaning bath (aqueous solution obtained by mixing 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 20°C (cleaning treatment). Then, it was dried in an oven maintained at 90°C while contacting a SUS heating roller maintained at a surface temperature of 75°C for about 2 seconds (drying shrinkage treatment). The shrinkage rate of the laminate in the width direction after drying and shrinkage treatment is 2%. In this way, the first polarizing element with a thickness of 5.0 μm is formed on the resin substrate.

2. Preparation of the first polarizing plate The HC-TAC film is bonded to the surface of the polarizing element of the laminate of the resin substrate/first polarizing element obtained above by a UV curing adhesive. The HC-TAC film is a film having a hard coating (HC) layer (7 μm thick) formed on a triacetyl cellulose (TAC) film (25 μm thick), and the TAC film is bonded to the polarizing element side. Subsequently, the resin substrate is peeled off, and the adhesive composition a obtained in Manufacturing Example 1 is used to form the first adhesive layer (thickness 20 μm) on the peeled surface, thereby obtaining a polarizing plate having a structure of an outer protective layer (HC-TAC film)/a first polarizing element/a first adhesive layer. The polarizing plate is punched into a size of 148 mm in length and 70 mm in width, and further, a through hole with a diameter of 3.9 mm is formed at the corner. At this time, the punching is performed in such a way that the absorption axis direction of the polarizing element becomes the short side direction. In this way, the first polarizing plate (visual side polarizing plate) A is obtained. The thickness of the first polarizing plate A is 37 μm, and the size L of the adhesive gap portion is 50 μm.

3. Preparation of the corresponding product of the image display device The first polarizing plate (viewing side polarizing plate) A obtained in 2. above is bonded to one side of the glass plate (corresponding to the image display unit) through the first adhesive layer. Then, the light peeling separation piece of the adhesive sheet I obtained in the manufacturing example 2 is peeled off and bonded to the cover glass (manufactured by Matsunami Glass Co., Ltd., thickness 0.8 mm) using a roller bonding machine. The other separation piece of the adhesive I of the laminate is peeled off and a vacuum bonding machine is used to make it close to the surface of the first polarizing plate A, and the through hole is filled with the adhesive sheet. The conditions of vacuum lamination are as follows: heat pressing at 0.2 MPa, 60°C (standby time 90 seconds), followed by vacuum lamination at 100 Pa for 10 seconds. Furthermore, according to convention, a commercially available polarizing plate with an adhesive layer as the second polarizing plate (back side polarizing plate) is attached to the other side of the glass plate. In this way, an image display device counterpart is produced. The obtained image display device counterpart is provided for the evaluation of (5) above. The results are shown in Table 1.

<Example 2> An image display device counterpart was produced in the same manner as Example 1 except that the size L of the adhesive gap portion of the first polarizing plate was set to 100 μm. The obtained image display device counterpart was subjected to the same evaluation as Example 1. The results are shown in Table 1.

<Example 3> An image display device counterpart was produced in the same manner as in Example 1 except that the thickness of the first adhesive layer was set to 15 μm. The obtained image display device counterpart was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Example 4> An image display device counterpart was produced in the same manner as Example 3 except that the size L of the adhesive gap portion of the first polarizing plate was set to 100 μm. The obtained image display device counterpart was subjected to the same evaluation as Example 1. The results are shown in Table 1.

<Example 5> An image display device counterpart was produced in the same manner as in Example 1 except that the thickness of the first adhesive layer was set to 5 μm. The obtained image display device counterpart was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Example 6> An image display device counterpart was produced in the same manner as Example 5 except that the size L of the adhesive gap portion of the first polarizing plate was set to 100 μm. The obtained image display device counterpart was subjected to the same evaluation as Example 1. The results are shown in Table 1.

<Comparative Examples 1 to 6> Except that the thickness of the third adhesive layer was set to 150 μm, image display device counterparts were produced in the same manner as in Examples 1 to 6. The obtained image display device counterparts were subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative Example 7> As the first polarizing element, a long strip of polyvinyl alcohol (PVA) resin film containing iodine and uniaxially stretched in the longitudinal direction (MD direction) was used (thickness 12 μm). An acrylic resin film (thickness 20 μm) serving as an outer protective layer and a triacetyl cellulose (TAC) film (thickness 25 μm) serving as an inner protective layer were respectively attached to both sides of the polarizing element, and a first adhesive layer (thickness 20 μm) was formed on the surface of the inner protective layer using the adhesive composition a obtained in Preparation Example 1, thereby obtaining a polarizing plate having a structure of outer protective layer (acrylic resin film)/first polarizing element/inner protective layer (TAC film)/first adhesive layer. The polarizing plate was punched and through holes were formed in the same manner as in Example 1. Thus, the first polarizing plate (viewing side polarizing plate) B was obtained. The thickness of the first polarizing plate B was 57 μm, and the size L of the adhesive gap was 50 μm. Using the first polarizing plate B obtained above, an image display device corresponding product was produced in the same manner as in Example 1 except for this. The obtained image display device corresponding product was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative Example 8> An image display device counterpart was produced in the same manner as in Comparative Example 7 except that the size L of the adhesive gap portion of the first polarizing plate was set to 100 μm. The obtained image display device counterpart was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative Example 9> As the first polarizing element, a long polyvinyl alcohol (PVA) resin film containing iodine and uniaxially stretched in the longitudinal direction (MD direction) was used (thickness 18 μm). An acrylic resin film (thickness 40 μm) serving as an outer protective layer and a TAC film (thickness 40 μm) serving as an inner protective layer were respectively attached to both sides of the polarizing element, and the adhesive composition a obtained in Preparation Example 1 was used to form a first adhesive layer (thickness 15 μm) on the surface of the inner protective layer, thereby obtaining a polarizing plate having a structure of outer protective layer (acrylic resin film)/first polarizing element/inner protective layer (TAC film)/first adhesive layer. The polarizing plate was punched and through holes were formed in the same manner as in Example 1. In this way, a first polarizing plate (viewing side polarizing plate) C was obtained. The thickness of the first polarizing plate C is 98 μm, and the size L of the adhesive gap is 50 μm. Using the first polarizing plate C obtained above, an image display device corresponding product is produced in the same manner as in Example 1 except for the above. The obtained image display device corresponding product is subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative Example 10> An image display device counterpart was produced in the same manner as in Comparative Example 9 except that the size L of the adhesive gap of the first polarizing plate was set to 100 μm. The obtained image display device counterpart was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative Examples 11 to 16> As the third adhesive layer, adhesive sheet II obtained in Production Example 3 was used instead of adhesive sheet I. Image display device counterparts were produced in the same manner as in Examples 1 to 6. The obtained image display device counterparts were subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative Examples 17 to 22> As the third adhesive layer, adhesive sheet III obtained in Production Example 4 was used instead of adhesive sheet I. Image display device counterparts were produced in the same manner as in Examples 1 to 6. The obtained image display device counterparts were subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Table 1] 1st polarizing plate 3rd Adhesive Layer 1st adhesive layer Adhesive gap size L Bubble Assessment Type(Thickness) Type(Thickness) Storage modulus (×10 ⁴ Pa) Gel fraction (%) thickness Embodiment 1 A(37) I(250) 1.9 40 20 50 4 Embodiment 2 ↓ ↓ ↓ ↓ ↓ 100 3 Embodiment 3 ↓ ↓ ↓ ↓ 15 50 4 Embodiment 4 ↓ ↓ ↓ ↓ ↓ 100 3 Embodiment 5 ↓ ↓ ↓ ↓ 5 50 4 Embodiment 6 ↓ ↓ ↓ ↓ ↓ 100 3 Comparison Example 1 ↓ I(150) ↓ ↓ 20 50 1 Comparison Example 2 ↓ ↓ ↓ ↓ ↓ 100 1 Comparison Example 3 ↓ ↓ ↓ ↓ 15 50 1 Comparison Example 4 ↓ ↓ ↓ ↓ ↓ 100 1 Comparison Example 5 ↓ ↓ ↓ ↓ 5 50 1 Comparative Example 6 ↓ ↓ ↓ ↓ ↓ 100 1 Comparison Example 7 B(57) I(250) ↓ ↓ 20 50 2 Comparative Example 8 ↓ ↓ ↓ ↓ ↓ 100 2 Comparative Example 9 C(98) ↓ ↓ ↓ 15 50 1 Comparative Example 10 ↓ ↓ ↓ ↓ ↓ 100 1 Comparative Example 11 A(37) II(250) 8.6 85 20 50 1 Comparative Example 12 ↓ ↓ ↓ ↓ ↓ 100 1 Comparative Example 13 ↓ ↓ ↓ ↓ 15 50 1 Comparative Example 14 ↓ ↓ ↓ ↓ ↓ 100 1 Comparative Example 15 ↓ ↓ ↓ ↓ 5 50 1 Comparative Example 16 ↓ ↓ ↓ ↓ ↓ 100 1 Comparative Example 17 ↓ III(250) 10.6 85 20 50 1 Comparative Example 18 ↓ ↓ ↓ ↓ ↓ 100 1 Comparative Example 19 ↓ ↓ ↓ ↓ 15 50 1 Comparative Example 20 ↓ ↓ ↓ ↓ ↓ 100 1 Comparative Example 21 ↓ ↓ ↓ ↓ 5 50 1 Comparative Example 22 ↓ ↓ ↓ ↓ ↓ 100 1 *The unit of thickness and gap size L is μm

<Evaluation> As can be seen from Table 1, according to the embodiment of the present invention, in an image display device in which an irregularly shaped processed part is filled with an adhesive, by setting the thickness of the polarizing plate on the viewing side and the thickness and storage modulus of the adhesive layer on the viewing side within a specific range, bubbles can be significantly suppressed. Furthermore, by making the adhesive void in the irregularly shaped processed part smaller, bubbles can be further suppressed. [Industrial Applicability]

The image display device of the present invention is suitable for use as an image display device having a special-shaped processing portion, represented by a car dashboard, a smart phone, a tablet PC (Personal Computer) or a smart watch.

10: 1st polarizing plate 11: 1st polarizing element 12: outer protective layer 13: inner protective layer 14: 1st adhesive layer 15: irregular processing part 16: adhesive gap part 20: 2nd polarizing plate 21: 2nd polarizing element 22: outer protective layer 23: inner protective layer 24: 2nd adhesive layer 25: irregular processing part 30: 3rd adhesive layer 40: cover glass 100: image display unit 200: image display device

FIG. 1 is a schematic exploded perspective view of an image display device of one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a through hole portion of the image display device of FIG. 1. FIG. 3 is a schematic top view illustrating an example of an irregular shape or an irregularly processed portion in the first polarizing plate and the second polarizing plate of the image display device of the embodiment of the present invention. FIG. 4 is a schematic top view illustrating a variation example of an irregular shape or an irregularly processed portion in the first polarizing plate and the second polarizing plate of the image display device of the embodiment of the present invention. FIG. 5 is a schematic top view illustrating another variation example of an irregular shape or an irregularly processed portion in the first polarizing plate and the second polarizing plate of the image display device of the embodiment of the present invention. FIG6 is a schematic top view illustrating another variation of the irregular shape or irregularly processed portion in the first polarizing plate and the second polarizing plate of the image display device of the embodiment of the present invention. FIG7 is a partial schematic cross-sectional view illustrating the adhesive gap portion in the first polarizing plate of the image display device of the embodiment of the present invention.

10: 1st polarizing plate

11: 1st polarizing element

12: External protective layer

13: Inner protective layer

14: 1st adhesive layer

15: Special shape processing department

20: Second polarizing plate

21: Second polarizing element

22: Outer protective layer

23: Inner protective layer

24: Second adhesive layer

25: Special shape processing department

30: Third adhesive layer

40: Covering glass

100: Image display unit

200: Image display device

Claims (14)

An image display device comprises: an image display unit; a first polarizing plate comprising a first polarizing element and a first adhesive layer, and laminated on the viewing side of the image display unit via the first adhesive layer; a second polarizing plate comprising a second polarizing element and a second adhesive layer, and laminated on the back side of the image display unit via the second adhesive layer; and a third adhesive layer disposed on The visual side of the first polarizing plate; the first polarizing plate and the second polarizing plate have irregularly processed parts at positions corresponding to each other, the irregularly processed part of the first polarizing plate is filled with an adhesive constituting a third adhesive layer, the thickness of the first polarizing plate is less than 90 μm, the thickness of the third adhesive layer is more than 170 μm, the storage modulus of the third adhesive layer at 60°C is less than 8.0×10 ⁴ Pa, the irregularly processed part of the first polarizing plate has an adhesive gap part, the adhesive gap part is formed by the end face of the first adhesive layer being located at a position closer to the inner side in the surface direction than the end face of the first polarizing plate, and the size of the adhesive gap part is less than 300 μm. An image display device comprises: an image display unit; a first polarizing plate comprising a first polarizing element and a first adhesive layer, and laminated on the visual side of the image display unit via the first adhesive layer; and a third adhesive layer, disposed on the visual side of the first polarizing plate; the first polarizing plate has a special-shaped processed portion, the special-shaped processed portion of the first polarizing plate is filled with an adhesive constituting the third adhesive layer, the thickness of the first polarizing plate is 90 μm or less, the thickness of the third adhesive layer is 170 μm or more, the storage modulus of the third adhesive layer at 60° C. is 8.0×10 ⁴ Pa or less, The irregularly processed portion of the first polarizing plate has an adhesive gap portion, which is formed by the end surface of the first adhesive layer being located further inward in the surface direction than the end surface of the first polarizing plate, and the size of the adhesive gap portion is less than 300 μm. An image display device as claimed in claim 1 or 2, wherein the thickness of the first adhesive layer is less than 50 μm. For example, in the image display device of claim 1 or 2, the bonding force between the first adhesive layer and the third adhesive layer is greater than 2N/25mm. As in claim 1 or 2, the image display device, wherein the gel fraction of the third adhesive layer is less than 80%. An image display device as claimed in claim 1 or 2, wherein the above-mentioned irregularly shaped processed portion includes a through hole or a cutting processed portion that is a concave portion when viewed from above. As in claim 6, the image display device, wherein the above-mentioned recess is a V-shaped recess or a U-shaped recess. The image display device of claim 1 or 2 has a cover glass on the visible side of the third adhesive layer. The image display device of claim 1 has a camera unit at a position corresponding to the irregularly processed portion of the first polarizing plate and the second polarizing plate. The image display device of claim 2 has a camera unit at a position corresponding to the irregularly processed portion of the first polarizing plate. The image display device of claim 1 is a liquid crystal display device. The image display device of claim 2 is an organic EL display device. A set of optical components includes: a first polarizing plate, which includes a first polarizing element and a first adhesive layer, has a thickness of 90 μm or less, has a special-shaped processing portion, and is arranged on the viewing side of an image display unit; and an adhesive sheet, which is composed of an adhesive having a storage modulus of 8.0×10 ⁴ Pa or less at 60°C, has a thickness of 200 μm or more, and fills the special-shaped processing portion of the first polarizing plate, the special-shaped processing portion of the first polarizing plate has an adhesive gap portion, the adhesive gap portion is formed by the end face of the first adhesive layer being located at a position closer to the inside of the end face of the first polarizing plate in the surface direction, and the size of the adhesive gap portion is less than 300 μm. The optical component set of claim 13 further includes a second polarizing plate, which includes a second polarizing element, has an irregularly processed portion, and is arranged on the back side of the image display unit. The first polarizing plate and the second polarizing plate have irregularly processed portions at positions corresponding to each other.