TW202424610A - Optical multilayer body and image display device - Google Patents

Abstract

An object of the present invention is to provide an optical laminate in which a specific resin layer is disposed adjacent to a polarizing member, and in which the cracking of the polarizing member in a high-temperature environment is suppressed. To achieve the object, the optical laminate according to an embodiment of the present invention is provided with: a plate polarizer including a polarizing member and a protection layer disposed on one side of the polarizing member; a resin layer disposed adjacent to the polarizing member; and a first adhesive layer disposed to be the outermost layer of the resin layer side. The shrinkage of the polarizing member in the direction of the absorption axis is less than 2.5%, the thickness of the first adhesive layer is less than 17 [mu]m, and the storage elastic modulus at 23 DEG C is more than 0.10 MPa.

Description

Optical multilayer body and image display device

The present invention relates to an optical multilayer body and an image display device.

In image display devices (such as liquid crystal display devices, organic EL display devices, and quantum dot display devices), due to their image formation methods, a polarizing plate is usually arranged on at least one side of the display panel. Furthermore, for the purpose of thinning and high functionality, a protective layer is sometimes provided only on one side of the polarizer in the polarizing plate, and a specific resin layer is provided on the side without the protective layer. In such a polarizing plate having a protective layer/polarizer/resin layer structure, the polarizer will often crack in a high temperature environment. Furthermore, polarizing plates are often used after being integrated with a phase difference layer (phase difference film), but when a phase difference layer is provided for a polarizing plate such as the above, the cracks of the polarizer will often become more obvious in a high temperature environment. Prior art literature Patent literature

Patent document 1: Japanese Patent Publication No. 2013-072951

Problem to be solved by the invention The present invention is made to solve the above existing problems, and its main purpose is to provide an optical laminate, in which a specific resin layer is arranged adjacent to a polarizer, and the optical laminate has suppressed cracks in the polarizer in a high temperature environment.

Means for solving the problem [1] An optical multilayer body according to an embodiment of the present invention comprises: a polarizing plate including a polarizer and a protective layer disposed on one side of the polarizer; a resin layer disposed adjacent to the polarizer; and a first adhesive layer disposed as the outermost layer on the side of the resin layer. The shrinkage rate of the polarizer in the absorption axis direction is less than 2.5%, the thickness of the first adhesive layer is less than 17 μm, and the storage elastic modulus at 23°C is greater than 0.10 MPa. [2] In the above [1], the optical laminate further includes a phase difference layer, which is laminated on the side of the resin layer opposite to the polarizer through a second adhesive layer. The phase difference layer has a circular polarization function or an elliptical polarization function. The thickness of the second adhesive layer is less than 7 μm, and the storage elastic modulus at 23°C is greater than 0.12 MPa. [3] In the above [1] or [2], when the total thickness of the polarizer and the protective layer is set to A (μm), and the total thickness of the resin layer, the second adhesive layer, the phase difference layer and the first adhesive layer is set to B (μm), the optical laminate satisfies the relationship A＜B. [4] In the above [2] or [3], the phase difference layer is formed by a stretched film of a resin film, and its Re(550) is 100nm~200nm, satisfying the relationship Re(450)＜Re(550), and the angle formed by the slow axis of the phase difference layer and the absorption axis of the polarizer is 40°~50°. [5] In any one of the above [2] to [4], the optical multilayer further has another phase difference layer on the side opposite to the resin layer of the phase difference layer, the refractive index characteristics showing the relationship of nz＞nx=ny. [6] In any one of the above [1] to [5], the resin layer contains a resin having a glass transition temperature of 85°C or higher and a weight average molecular weight Mw of 25,000 or higher. [7] In any one of the above [1] to [6], the indentation elastic modulus of the resin layer is 8 GPa or higher. [8] In any one of the above [1] to [7], the thickness of the resin layer is 1 μm or less. [9] In any of the above [1] to [8], the thickness of the polarizer is less than 8 μm, the indentation elastic modulus is less than 9.5 GPa, and the indentation hardness is greater than 0.65 GPa. [10] In any of the above [1] to [9], the orientation function of the polarizer is greater than 0.30. [11] In any of the above [1] to [10], the shrinkage rate of the polarizer in the absorption axis direction is less than 2.0%. [12] According to another aspect of the present invention, an image display device is provided. The image display device comprises an image display panel and the optical multilayer body of any of the above [1] to [11], wherein the optical multilayer body is attached to the image display panel via the first adhesive layer.

Effect of the invention According to the implementation form of the present invention, an optical laminate can be realized, in which a specific resin layer is arranged adjacent to a polarizer, and the optical laminate has suppressed cracks in the polarizer in a high temperature environment.

Hereinafter, representative embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

(Definition of terms and symbols) The definitions of terms and symbols in this manual are as follows. (1) Refractive index (nx, ny, nz) "nx" is the refractive index in the direction where the in-plane refractive index reaches the maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction orthogonal to the slow axis (i.e., the fast axis direction) in the plane, and "nz" is the refractive index in the thickness direction. (2) In-plane phase difference (Re) "Re(λ)" is the in-plane phase difference of a film measured at 23°C using light of a wavelength of λnm. For example, "Re(550)" is the in-plane phase difference of a film measured at 23°C using light of a wavelength of 550nm. When the thickness of the film is set to d(nm), Re(λ) can be calculated by the formula: Re=(nx-ny)×d. (3) Retardation in the thickness direction (Rth) "Rth(λ)" is the retardation in the thickness direction of the film measured at 23°C using light of wavelength λnm. For example, "Rth(550)" is the retardation in the thickness direction of the film measured at 23°C using light of wavelength 550nm. When the thickness of the film is set to d(nm), Rth(λ) can be calculated by the formula: Rth=(nx-nz)×d. (4) Nz coefficient The Nz coefficient can be calculated by Nz=Rth/Re. (5) Angle When an angle is mentioned in this manual, unless otherwise specified, the angle includes both the clockwise and counterclockwise angles.

A. Optical laminate FIG1 is a schematic cross-sectional view of an optical laminate of an embodiment of the present invention. The optical laminate 100 of the illustrated example has a polarizing plate 10, a resin layer 20, and a first adhesive layer 50 in order from the upper side of the attached figure. The upper side of the attached figure may correspond to the visual side when the optical laminate is applied to an image display device; the lower side of the attached figure may correspond to the image display panel side. The polarizing plate 10 includes a polarizing element 11 and a protective layer 12, and the protective layer 12 is arranged on one side of the polarizing element 11 (visual side). That is, in the embodiment of the present invention, the polarizing plate is a so-called single-sided protected polarizing plate. If necessary, the protective layer 12 may include a hard coating layer (not shown) on the side opposite to the polarizer 11. The resin layer 20 may be arranged adjacent to the polarizer 11. In addition, in this specification, "arranged adjacent to the polarizer" means that the resin layer is directly formed on the polarizer, or the resin layer is laminated on the polarizer through a bonding layer (representatively, a bonding agent layer or an adhesive layer). In other words, it means that there is no optical functional layer between the polarizer and the resin layer. The first adhesive layer 50 is arranged as the outermost layer on the side of the resin layer 20. The optical laminate can be attached to the image display panel by the first adhesive layer 50.

Typically, the resin layer 20 is a solidified or cured product of a coating film of an organic solvent solution of the resin. Typically, the glass transition temperature of the resin contained in the resin layer 20 is above 85°C, and the weight average molecular weight Mw is above 25,000. The resin layer 20 may have a barrier function. The resin layer 20 may inhibit the migration of moisture in a high temperature and high humidity environment, thereby inhibiting discoloration of the end of the polarizer. Furthermore, the resin layer 20 may inhibit the migration of iodine that may be contained in the polarizer, thereby reducing the effect that the polarizer may have on other components. For example, when the optical laminate is mounted on an image display device (such as an organic EL display device), corrosion of the metal components of the image display device may be inhibited. By placing such a resin layer adjacent to the polarizer of the embodiment of the present invention, end discoloration in a high temperature and high humidity environment can be better suppressed. In addition, by placing such a resin layer adjacent to the polarizer, the protective layer can be omitted. The resin layer is much thinner than the protective layer, so it can maintain the function of protecting the polarizer well and can contribute to the thinning of the optical laminate. The details of the resin layer will be described in Item C below. In the optical laminate in which this specific resin layer is adjacent to the polarizer, the effect of the embodiment of the present invention becomes significant.

In the embodiment of the present invention, the shrinkage rate of the polarizer 11 in the absorption axis direction is less than 2.5%, the thickness of the first adhesive layer 50 is less than 17 μm, and the storage elastic modulus at 23°C is greater than 0.10 MPa. With this structure, in an optical laminate in which a specific resin layer and a polarizer are adjacently arranged as described above, cracks in the polarizer under a high temperature environment can be significantly suppressed. The details are as follows. The resin layer as described above is very hard due to its characteristics (as described later, the indentation elastic modulus is, for example, greater than 8 GPa), and as a result, it is very easy to break. In addition, the polarizer is also constructed in a way to improve the optical properties and suppress end discoloration, and as a result, it becomes very hard (as described later, the indentation hardness is, for example, 0.65 GPa or more) and is easy to break. The inventors of the present invention have found that in such an optical laminate, the resin layer will break due to external forces, and the polarizer will follow the breakage of the resin layer and produce cracks, and the cracks will progress in a high temperature environment. The inventors of the present invention have conducted in-depth research on the solution and found that it is useful to first suppress the deformation that causes the resin layer to break, and the thickness of the first adhesive layer adjacent to the resin layer and the storage elastic modulus are combined and optimized, thereby effectively suppressing the deformation of the resin layer. Specifically, it was found that by setting the thickness of the first adhesive layer to 17 μm or less, the resin layer can be suppressed from being deformed by external force, etc. Furthermore, by setting the storage elastic modulus of the first adhesive layer to 0.10 MPa or more (by curing to a certain extent), the resin layer can be suppressed from being deformed. As a countermeasure against external force and the like, it is common knowledge in the art to make the adhesive layer soft to absorb the external force and the like and to mitigate the impact. However, according to the embodiment of the present invention, in the optical laminate having a specific structure as described above, the thickness of the adhesive layer and the storage elastic modulus are combined and optimized, and the storage elastic modulus is hardened to a certain extent, thereby suppressing the deformation of the resin layer, and as a result, the cracks of the polarizer can be suppressed. As described above, the effect of the embodiment of the present invention is achieved by means contrary to common knowledge in the art, which is an unexpected excellent effect. In addition, according to the embodiment of the present invention, by setting the shrinkage rate of the polarizer in the absorption axis direction to less than 2.5%, even if the resin layer is deformed or cracked, it is not easy to follow the deformation or cracking, and the cracks can be suppressed. In addition, the mechanism as described above is only a speculation and does not make a limiting interpretation of the present invention, and the present invention is not limited by the mechanism.

In one embodiment, the optical laminate 101 shown in FIG. 2 may further include a phase difference layer 30, which is laminated on the side of the resin layer 10 opposite to the polarizer 11 through the second adhesive layer 60. Typically, the phase difference layer 30 has a circular polarization function or an elliptical polarization function. With such a structure, an optical laminate having excellent anti-reflection properties may be obtained. At this time, the optical laminate 101 may further include another phase difference layer 40 having a refractive index property showing a relationship of nz＞nx=ny on the side of the phase difference layer 30 opposite to the resin layer 20 (for example, between the phase difference layer 30 and the first adhesive layer 50), as shown in the example diagram. By providing this other phase difference layer, oblique reflection can be well prevented, and the anti-reflection function can be widened in viewing angle. At this time, the thickness of the second adhesive layer is less than 7μm, and the storage modulus at 23°C is more than 0.12MPa. It can be seen that by providing the phase difference layer, the resin layer may be ruptured due to external force, etc. In contrast, by combining and optimizing the thickness and storage modulus of the second adhesive layer adjacent to the resin layer in the same manner as above, the deformation (and rupture as a result) of the resin layer can be well suppressed. Here, the thickness of the second adhesive layer is 7 μm or less, which is thinner than the thickness of the first adhesive layer, and the storage modulus is 0.12 MPa or more, which is greater than the storage modulus of the first adhesive layer. Thus, even if the phase difference layer may cause deformation (and, as a result, rupture) of the resin layer, such deformation and rupture can be well suppressed. Furthermore, by setting the thickness and storage modulus of the first adhesive layer as described above, a synergistic effect can be obtained with the effect of combining and optimizing the thickness and storage modulus of the second adhesive layer.

In one embodiment, when the total thickness of the polarizer and the protective layer is set to A (μm), and the total thickness of the resin layer, the second adhesive layer, the phase difference layer, and the first adhesive layer is set to B (μm), the optical laminate satisfies the relationship of A < B. It can be seen that in the optical laminate, when the thickness of the resin layer on the side opposite to the viewing side is large, the resin layer will be cracked. According to the embodiment of the present invention, even in this case, the deformation (and consequently, cracking) of the resin layer can be suppressed, thereby suppressing cracks in the polarizer. The absolute value of the difference between thickness A and thickness B is preferably 10 μm to 50 μm, more preferably 20 μm to 40 μm. Furthermore, the ratio of thickness A to thickness B (B/A) is preferably 1.1 to 3.0, more preferably 1.2 to 2.5. In addition, when other phase difference layers are provided, the total thickness B includes the thickness of the other phase difference layers.

In practical terms, a peel pad (not shown) is preferably temporarily attached to the surface of the first adhesive layer 50 before the optical laminate is used. By temporarily attaching the peel pad, the roll of the optical laminate can be formed while protecting the first adhesive layer.

The following describes the components of the optical laminate. In addition, the first adhesive layer and the second adhesive layer are described together as adhesive layers. When it is necessary to distinguish between the first adhesive layer and the second adhesive layer, "first" or "second" is clearly stated.

B. Polarizing plate B-1. Polarizer Typically, the polarizer is made of a polyvinyl alcohol (PVA) resin film containing a dichroic substance (such as iodine). Examples of PVA resins include polyvinyl alcohol, partially formalized polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and partially saponified ethylene-vinyl acetate copolymer.

The PVA resin preferably includes an acetyl-modified PVA resin. With such a composition, a polarizer having a desired mechanical strength can be obtained. When the entire PVA resin is set to 100 wt %, the blending amount of the acetyl-modified PVA resin is preferably 5 wt % to 20 wt %, and more preferably 8 wt % to 12 wt %. If the blending amount is within this range, a polarizer having a better mechanical strength can be obtained.

The polarizer preferably contains iodide or sodium chloride (sometimes collectively referred to as halides). As iodides, for example, potassium iodide, sodium iodide, and lithium iodide can be listed. The content of halides in the polarizer is preferably 5 parts by weight to 20 parts by weight, and more preferably 10 parts by weight to 15 parts by weight relative to 100 parts by weight of the PVA-based resin. The halides can be mixed into the coating liquid used to form the PVA-based resin layer that is a precursor of the polarizer in the manufacturing method described later and finally introduced into the polarizer. By introducing halides into the polarizer, the orientation of the PVA molecules in the polarizer can be improved, thereby realizing a polarizer with excellent optical properties (typically, taking into account both high polarization degree and high monomer transmittance).

The thickness of the polarizer is preferably 1 μm to 8 μm, more preferably 2 μm to 7 μm, and even more preferably 3 μm to 6 μm. As described above, by controlling the shrinkage rate in the absorption axis direction of a very thin and highly oriented polarizer, the effect of the embodiment of the present invention can be made significant. Furthermore, if the thickness of the polarizer is within this range, curling during heating can be well suppressed, and good appearance durability during heating can be obtained.

As mentioned above, the shrinkage rate of the polarizer in the absorption axis direction is less than 2.5%, preferably less than 2.2%, more preferably less than 2.0%, and more preferably less than 1.8%. The smaller the shrinkage rate, the better, for example, it can be more than 0.5%, and for example, it can be more than 0.8%. The shrinkage rate can be measured by, for example, thermomechanical analysis (TMA). More specifically, the shrinkage rate refers to the shrinkage rate at 95°C when measured by TMA under the following conditions. Temperature range: -50°C~120°C Heating rate: 2°C/min Adjustment: 300 seconds/cycle is adjusted by ±5°C Tensile load: 0.0196N

The indentation elastic modulus of the polarizer is preferably 7.5 GPa to 9.4 GPa, more preferably 8.0 GPa to 9.3 GPa, more preferably 8.2 GPa to 9.2 GPa, and particularly preferably 8.5 GPa to 9.2 GPa. The indentation hardness of the polarizer is preferably 0.65 GPa to 0.80 GPa, more preferably 0.66 GPa to 0.76 GPa, more preferably 0.67 GPa to 0.74 GPa, and particularly preferably 0.68 GPa to 0.72 GPa. The polarizer used in the embodiment of the present invention has the characteristic that the indentation hardness is still very large despite the low indentation elastic modulus. As a result, the polarizer of the embodiment of the present invention can significantly suppress end discoloration (especially end discoloration in a high temperature and high humidity environment) despite being very thin. Such polarizers tend to crack easily, but according to the embodiment of the present invention, the occurrence of cracks can be suppressed. In addition, the indentation hardness and the indentation elastic modulus can be measured by the nanoindentation method using an indentation tester (typically a nanoindenter). More specifically, the indentation hardness is calculated from the maximum load Pmax and the contact projection area A between the indenter and the polarizer using the following formula. The aforementioned maximum load Pmax is obtained by pressing the probe (indenter) on the surface of the polarizer to be measured and obtaining the displacement-load hysteresis curve. Indentation hardness (GPa) = Pmax/A In addition, the indentation elastic modulus is calculated from the contact projection area A, the slope of the tangent to the unloading curve of the displacement-load hysteresis curve (contact rigidity) S and the circumference π using the following formula. Indentation elastic modulus (GPa) = (√π/2) × (S/√A)

The orientation function of the polarizer is preferably greater than 0.30, more preferably greater than 0.35, more preferably greater than 0.37, and particularly preferably greater than 0.40. If the orientation function of the polarizer is within this range, it is easy to set the indentation elastic modulus and the indentation hardness to the above-mentioned desired range. The upper limit of the orientation function of the polarizer can be, for example, 0.70. The orientation function (y) is obtained, for example, by using a Fourier transform infrared spectrophotometer (FT-IR) with polarized light as the measuring light and by attenuated total reflection spectroscopy (ATR). Specifically, the measurement is carried out in a state where the extension direction of the polarizer is parallel and perpendicular to the polarization direction of the measuring light, and the intensity of 2941 cm ^-1 of the obtained absorbance spectrum is calculated according to the following formula. Here, the intensity I is the value of 2941cm ^-1 /3330cm ^-1 when 3330cm ^-1 is used as the reference peak. In addition, it is completely oriented when y=1, and it is random when y=0. In addition, we believe that the peak of 2941cm ^-1 is due to the absorption caused by the vibration of the main chain (-CH ₂ -) of PVA in the polarizer. y=(3＜cos ² θ＞-1)/2 =(1-D)/[c(2D+1)] =-2×(1-D)/(2D+1) Where, in the case of c=(3cos ² β-1)/2 and the vibration of 2941cm ^-1 , β=90°. θ: Angle of the molecular chain relative to the extension direction β: Angle of the transition dipole moment relative to the molecular chain axis D = (I _⊥ ) / (I _// ) (At this time, the more oriented the PVA molecules are, the larger D is) I _⊥ : The absorption intensity when the polarization direction of the measured light is perpendicular to the extension direction of the polarizer I _// : The absorption intensity when the polarization direction of the measured light is parallel to the extension direction of the polarizer

The polarizer preferably exhibits absorption dichroism at any wavelength between 380nm and 780nm. The single body transmittance of the polarizer is, for example, 41.0% to 45.0%, preferably 41.5% to 43.5%, more preferably 42.0% to 43.0%. The polarization degree of the polarizer is preferably 97.0% or more, preferably 99.0% or more, and more preferably 99.9% or more. According to the embodiment of the present invention, even if the single body transmittance is in the above range, the polarization degree can be maintained within the range.

Typically, a polarizer can be obtained using a laminate of a resin substrate and a PVA-based resin layer. Specific examples of polarizers obtained using a laminate include 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. A polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced in the following manner: for example, a PVA-based resin solution is coated on the resin substrate, and the PVA-based resin layer is formed on the resin substrate by drying the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; the laminate is stretched and dyed to make the PVA-based resin layer into a polarizer. In this embodiment, a polyvinyl alcohol-based resin layer containing a halogenated substance and a polyvinyl alcohol-based resin is preferably formed on one side of the resin substrate. Typically, stretching includes immersing the laminate in a boric acid aqueous solution and stretching it. Furthermore, if necessary, the stretching may further include: stretching the laminate in the air at a high temperature (for example, above 95°C) before stretching in an aqueous boric acid solution. In addition, in this embodiment, the laminate is preferably subjected to a dry shrinking treatment, which is performed by transporting the laminate along the long side while heating it so that it shrinks by more than 2% in the width direction. Typically, the manufacturing method of this embodiment includes: sequentially subjecting the laminate to an air-assisted stretching treatment, a dyeing treatment, an underwater stretching treatment, and a dry shrinking treatment. By introducing auxiliary stretching, even when PVA is coated on a thermoplastic resin, the crystallinity of PVA can be improved, thereby achieving high optical properties. At the same time, by improving the orientation of PVA in advance, when immersed in water in the dyeing step and the stretching step described later, the problems such as the orientation reduction or dissolution of PVA can be prevented, and high optical characteristics can be achieved. Furthermore, when the PVA-based resin layer is immersed in a liquid, the orientation disorder and orientation reduction of the polyvinyl alcohol molecules can be suppressed more than when the PVA-based resin layer does not contain halides. Thereby, the optical characteristics of the polarizer obtained by the treatment steps of immersing the laminate in a liquid such as dyeing treatment and underwater stretching treatment can be improved. Furthermore, by shrinking the laminate in the width direction by using a dry shrinking treatment, the optical characteristics can be improved. The obtained resin substrate/polarizer laminate can be used directly (i.e., the resin substrate can be used as a protective layer of the polarizer), or any appropriate protective layer that meets the purpose can be laminated on the peeling surface obtained by peeling off the resin substrate from the resin substrate/polarizer laminate or on the surface opposite to the peeling surface. The details of the manufacturing method of such a polarizer are described in, for example, Japanese Patent Publication No. 2012-73580 and Japanese Patent No. 6470455. The entire contents of these publications are cited as references in this specification.

In the embodiment of the present invention, the stretching temperature in the air-assisted stretching treatment is above 140°C and the stretching ratio is above 2.5 times. The stretching temperature is preferably above 145°C, more preferably above 150°C, and more preferably above 155°C. The upper limit of the stretching temperature can be, for example, 170°C. The stretching ratio is preferably 2.5 times to 3.2 times, more preferably 2.6 times to 3.1 times, and more preferably 2.7 times to 3.0 times. In the previous method for manufacturing thin polarizers, typically, the air-assisted stretching treatment is carried out at a temperature above the glass transition temperature (Tg) of the thermoplastic resin substrate (typically polyethylene terephthalate (PET)) + 15°C and at a temperature that can inhibit the rapid crystallization of the PVA-based resin. Specifically, this stretching temperature is around 130°C. In addition, the stretching ratio of the air-assisted stretching treatment in the manufacturing method of the previous thin polarizer is usually set to 2.0 times to 2.4 times. This is because: the total stretching ratio of the air-assisted stretching treatment and the underwater stretching treatment should be a fixed value (for example, 5.5 times to 6.0 times), so when stretching is performed near 130°C, the stretching ratio of the underwater stretching treatment needs to be reduced for a stretching ratio exceeding 2.5 times. This is because sometimes the optical properties are reduced due to the reduced orientation of iodine. In addition, at a temperature exceeding 130°C, it is difficult to suppress the rapid crystallization of the PVA-based resin as mentioned above, and it is difficult to control the elongation. The inventors of the present invention have found that by performing an in-air auxiliary stretching treatment at a high temperature and a high stretching ratio that has never been implemented before, it is possible to maintain the desired optical properties (taking into account both high monomer transmittance and high polarization degree) and realize a hard and thin polarizer.

Typically, the drying shrinkage treatment is performed in combination with a heating roller drying method when the zone heating is performed by heating the entire zone and the conveying roller is heated (using a so-called heating roller). In the embodiment of the present invention, the shrinkage rate of the polarizer can be set to less than 2.5% by controlling the temperature of the heating zone, the temperature of the heating roller, the time from the start of the zone heating to the contact with the heating roller, and the conveying tension of the laminate. The temperature of the heating zone is preferably 80°C to 110°C. The temperature of the heating roller is preferably 60°C to 90°C. The conveying tension of the laminate is preferably 4N/cm to 6N/cm. The time from the start of regional heating to contact with the heating roller should be 1 second to 10 seconds.

B-2. Protective layer The protective layer 12 is composed of any appropriate resin film that can be used as a protective film for a polarizer. Representative materials for the resin film include cellulose resins such as triacetate cellulose (TAC); cycloolefin resins such as polynorthene; (meth)acrylic resins, polyester resins such as polyethylene terephthalate (PET), and polyethylene naphthalate (PEN); polyolefin resins such as polyethylene; and polycarbonate resins. As a representative example of a (meth)acrylic resin, a (meth)acrylic resin having a lactone ring structure can be cited. (Meth) acrylic resins having a lactone ring structure are described in, for example, Japanese Patent Publication No. 2000-230016, Japanese Patent Publication No. 2001-151814, Japanese Patent Publication No. 2002-120326, Japanese Patent Publication No. 2002-254544, and Japanese Patent Publication No. 2005-146084. These publications are cited as references in this specification. From the perspective of ease of special-shaped processing, cellulose resins are preferred, and TAC is more preferred. From the perspective of obtaining a polarizing plate with low moisture permeability and excellent durability, cycloolefin resins and (meth) acrylic resins are preferred.

Typically, the optical multilayer body is disposed on the viewing side of the image display device, and typically, the protective layer 12 is disposed on the viewing side thereof. Therefore, the protective layer 12 may be subjected to surface treatment as needed. Examples of surface treatment include hard coating treatment, anti-reflection treatment, anti-sticking treatment, and anti-glare treatment. In the embodiment of the present invention, hard coating treatment (forming a hard coating layer) is preferred. The hard coating layer will be described later. The hard coating treatment may be implemented in combination with other surface treatments. Furthermore, or alternatively, the protective layer 12 may be subjected to treatment to improve visibility when viewed through polarized sunglasses (typically, providing (elliptical) circular polarization function and providing ultra-high phase difference) as needed. By implementing the above processing, even when viewing the display screen through polarized lenses such as polarized sunglasses, excellent visibility can be achieved. Therefore, the optical multilayer body can also be suitably applied to image display devices that can be used outdoors.

The thickness of the protective layer 12 is preferably 10 μm to 80 μm, more preferably 12 μm to 40 μm, and even more preferably 15 μm to 35 μm. In addition, when surface treatment is applied, the thickness of the protective layer is the thickness including the thickness of the surface treatment layer.

Typically, the hard coating layer is a hardened layer of any appropriate active energy ray (e.g., ultraviolet rays, visible light, electron beam) hardening resin. Examples of active energy ray hardening resins include acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, epoxy resins, and the like. The hard coating layer may contain any appropriate additive as required. Representative examples of the additive include inorganic microparticles and/or organic microparticles. The thickness of the hard coating layer may be, for example, 1 μm to 10 μm, or, for example, 3 μm to 7 μm. The hard coating layer has a pencil hardness of preferably H or above, more preferably 2H or above, and more preferably 3H or above. On the other hand, the pencil hardness of the hard coating should be below 6H, preferably below 5H.

C. Resin layer As described above, the resin layer 20 can have a barrier function. Therefore, the resin layer is typically hard. Specifically, the indentation elastic modulus of the resin layer is preferably 8 GPa or more, preferably 10 GPa to 20 GPa, and more preferably 11 GPa to 15 GPa. According to the embodiment of the present invention, although the resin layer is hard and easily cracked as described above, cracks in the polarizer adjacent to the resin layer can still be suppressed.

Typically, the resin layer is a solidified or cured product of a coating film of an organic solvent solution of the resin. Due to this structure, excellent adhesion to the polarizer can be achieved. Specifically, the resin layer can be formed directly on the polarizer without an intermediate layer. In addition, the thickness of the resin layer can be made very thin. The thickness of the resin layer is, for example, less than 10 μm, preferably less than 5 μm, more preferably less than 1 μm, and more preferably less than 0.7 μm. The thickness of the resin layer is preferably greater than 0.05 μm, more preferably greater than 0.08 μm, more preferably greater than 0.1 μm, and particularly preferably greater than 0.2 μm.

In one embodiment, the glass transition temperature (Tg) of the resin constituting the resin layer is above 85°C and the weight average molecular weight (Mw) is above 25,000. The Tg of the resin constituting the resin layer is preferably above 90°C, more preferably above 100°C, more preferably above 110°C, and particularly preferably above 120°C. Tg can be, for example, below 200°C. Furthermore, the Mw of the resin constituting the resin layer is preferably above 30,000, more preferably above 35,000, and more preferably above 40,000. By making the Tg and Mw of the resin constituting the resin layer within such a range, an excellent barrier function can be achieved despite a very thin thickness.

As the resin constituting the resin layer, any appropriate resin that can form a cured product or a hardened product (e.g., a thermosetting product) of a coating film of an organic solvent solution can be used. As the resin constituting the resin layer, a thermoplastic resin or a thermosetting resin having the above-mentioned Tg and Mw is preferably used, and a thermoplastic resin is more preferably used. The resin may be used alone or in combination of two or more.

Examples of the thermoplastic resin include acrylic resins and epoxy resins. Acrylic resins and epoxy resins may be used in combination.

Typically, acrylic resins contain repeating units derived from (meth)acrylate monomers having a linear or branched structure as a main component. Acrylic resins may contain repeating units derived from any appropriate copolymer monomer that meets the purpose. Examples of copolymers include carboxyl-containing monomers, hydroxyl-containing monomers, amide-containing monomers, aromatic ring-containing (meth)acrylates, and heterocyclic vinyl monomers. By appropriately setting the type, amount, combination, and copolymerization ratio of the monomer units, an acrylic resin having the above-mentioned predetermined Mw may be obtained. Specific examples of acrylic resins include boron-containing acrylic resins and lactone ring-containing acrylic resins described in [0034] to [0056] of Japanese Patent Application Laid-Open No. 2021-117484.

As the epoxy resin, an epoxy resin having an aromatic epoxy group is preferably used. By using an epoxy resin having an aromatic epoxy group as the epoxy resin, the adhesion between the resin layer and the polarizer can be improved. Furthermore, when an adhesive layer is arranged adjacent to the resin layer, the anchoring force of the adhesive layer can be improved. Examples of the epoxy resin having an aromatic ring include bisphenol-type epoxy resins such as bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, and bisphenol S-type epoxy resin; novolac-type epoxy resins such as phenol novolac epoxy resin, cresol novolac epoxy resin, and hydroxybenzaldehyde phenol novolac epoxy resin; polyfunctional epoxy resins such as glyoxypropyl ether of tetrahydroxyphenylmethane, glyoxypropyl ether of tetrahydroxydiphenyl ketone, and epoxidized polyethylenephenol; naphthol-type epoxy resins, naphthalene-type epoxy resins, and biphenyl-type epoxy resins; and the like. Preferred examples of the epoxy resin include bisphenol A type epoxy resin, biphenyl type epoxy resin, and bisphenol F type epoxy resin. The epoxy resin may be used alone or in combination of two or more.

Typically, the resin layer can be formed by applying an organic solvent solution of the above-mentioned resin to form a coating film, and curing or heat-hardening the obtained coating film. As an organic solvent, any appropriate organic solvent that can dissolve or evenly disperse the above-mentioned resin can be used. Specific examples of organic solvents include ethyl acetate, toluene, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclopentanone, and cyclohexanone. The resin concentration of the solution is preferably 3 parts by weight to 20 parts by weight relative to 100 parts by weight of the solvent. If it is such a resin concentration, a uniform coating film can be formed.

The solution can be applied to a separately prepared substrate, preferably to a polarizing plate (polarizer). When the solution is applied to the substrate, the solidified or hardened product (resin layer) of the coating film formed on the substrate is transferred to the polarizing plate (polarizer). Typically, the transfer is performed through a bonding layer, so by applying the solution to the polarizing plate (polarizer), the resin layer can be directly formed and the bonding layer can be omitted. As a method for applying the solution, any appropriate method can be adopted. Specific examples include roll coating, spin coating, wire rod coating, dip coating, die coating, curtain coating, spray coating, and scraper coating (cutaway wheel coating, etc.).

The heating temperature for curing or heat curing the coating film is preferably below 100° C., more preferably 50° C. to 70° C. If the heating temperature is within this range, adverse effects on the polarizer can be prevented. The heating time can be, for example, 1 minute to 10 minutes.

The resin layer (substantially a solution of the above resin in an organic solvent) may contain any appropriate additives that suit the purpose. Specific examples of additives include ultraviolet absorbers; levelers; antioxidants such as hindered phenol, phosphorus, and sulfur; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fiber and carbon fiber; near-infrared absorbers; flame retardants such as tri(dibromopropyl) phosphate, triallyl phosphate, and antimony oxide; antistatic agents such as anionic, cationic, and non-ionic surfactants; colorants such as inorganic pigments, organic pigments, and dyes; organic fillers or inorganic fillers; resin modifiers; organic fillers and inorganic fillers; plasticizers; lubricants; flame retardants, etc. The type, quantity, combination, and addition amount of additives can be appropriately set according to the purpose.

D. Phase difference layer As described above, typically, the phase difference layer 40 has a circular polarization function or an elliptical polarization function. The phase difference layer can be a single layer or a laminated structure of two or more layers. When the phase difference layer is composed of a single layer, the phase difference layer can be a λ/4 plate. When the phase difference layer has a laminated structure, the phase difference layer can be a laminate of a λ/2 plate and a λ/4 plate. The phase difference layer can be composed of any appropriate material. Specifically, the phase difference layer can be a directional solidification layer of a liquid crystal compound, a resin film (typically a stretched film), or a combination thereof. In the embodiment of the present invention, typically, the phase difference layer can be composed of a stretched film of a resin film. In this case, the phase difference layer can be a single layer (λ/4 plate) on the surface. Below, a simple explanation is given of the stretched film as a single layer of resin film.

As mentioned above, the phase difference layer can function as a λ/4 plate. At this time, the in-plane phase difference Re(550) of the phase difference layer is, for example, 100nm~190nm, preferably 110nm~170nm, and more preferably 130nm~160nm. At this time, the refractive index characteristics of the phase difference layer preferably show the relationship of nx＞ny≥nz. In addition, "ny=nz" here includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, within the scope of not impairing the effect of the embodiment of the present invention, it may sometimes be ny＜nz.

The Nz coefficient of the phase difference layer is preferably 0.9 to 3, more preferably 0.9 to 2.5, more preferably 0.9 to 1.5, and particularly preferably 0.9 to 1.3. By satisfying this relationship, when the obtained optical multilayer body is used in an image display device, a very excellent reflection hue can be achieved.

Typically, as described above, the phase difference layer shows a relationship of nx>ny, and therefore has a slow axis. In one embodiment, the angle θ formed by the slow axis of the phase difference layer and the absorption axis of the polarizer is, for example, 40°~50°, preferably 42°~48°, and more preferably about 45°. If the angle θ is within this range, by setting the phase difference layer to a λ/4 plate, an optical laminate having very excellent circular polarization characteristics (and, as a result, very excellent anti-reflection characteristics) can be obtained.

Typically, the thickness of the phase difference layer can be set to a thickness that can properly function as a λ/4 plate. The thickness of the phase difference layer can be, for example, 10μm to 60μm. If the thickness of the phase difference layer is within this range, the total thickness B of the resin layer, the second adhesive layer, the phase difference layer, and the first adhesive layer will increase. That is, in the optical laminate, the thickness of the resin layer on the side opposite to the viewing side will increase, which will promote the rupture of the resin layer due to external forces, etc. According to the implementation form of the present invention, even when a phase difference layer having such a thickness is provided, the deformation (and, as a result, rupture) of the resin layer can be suppressed, thereby suppressing cracks in the polarizer.

The phase difference layer can show an inverse dispersion wavelength characteristic in which the phase difference value increases with the wavelength of the measured light, can show a positive wavelength dispersion characteristic in which the phase difference value decreases with the wavelength of the measured light, and can also show a flat wavelength dispersion characteristic in which the phase difference value hardly changes with the wavelength of the measured light. In one embodiment, the phase difference layer shows an inverse dispersion wavelength characteristic. In this case, Re(450)/Re(550) of the phase difference layer is, for example, greater than 0.8 and less than 1, preferably greater than 0.8 and less than 0.95. With this configuration, very excellent anti-reflection characteristics can be achieved.

Representative examples of the resin constituting the phase difference layer (resin film) include polycarbonate resins, polyester carbonate resins, polyester resins, polyvinyl acetal resins, polyarylate resins, cyclic olefin resins, cellulose resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, and acrylic resins. These resins may be used alone or in combination (e.g., blended or copolymerized). When the phase difference layer is composed of a resin film showing reverse dispersion wavelength characteristics, a polycarbonate resin or a polyester carbonate resin (hereinafter sometimes simply referred to as a polycarbonate resin) can be suitably used.

The polycarbonate resin comprises at least one structural unit selected from the group consisting of structural units represented by the following general formula (1) and/or structural units represented by the following general formula (2). These structural units are divalent structural units derived from oligofluorene, and are sometimes referred to as oligofluorene structural units hereinafter. Such a polycarbonate resin has positive refractive index anisotropy. [Chemical Formula 1] [Chemical formula 2]

Typically, the phase difference layer further contains an acrylic resin, and the content of the acrylic resin is 0.5 mass % to 1.5 mass %.

The details of the polycarbonate resin that can be suitably used for the phase difference layer and the method for forming the phase difference layer are described in, for example, Japanese Patent Publication No. 2014-10291, Japanese Patent Publication No. 2014-26266, Japanese Patent Publication No. 2015-212816, Japanese Patent Publication No. 2015-212817, Japanese Patent Publication No. 2015-212818, International Publication No. 2015/159928, and Japanese Patent Publication No. 2021-67762, and the descriptions of these publications are cited in this specification as references.

E. Other phase difference layers As mentioned above, the other phase difference layer 40 can be a so-called positive C plate whose refractive index characteristics show the relationship of nz＞nx=ny. By using a positive C plate as the other phase difference layer, oblique reflection can be well prevented, and the anti-reflection function can be widened. At this time, the phase difference Rth(550) in the thickness direction of the other phase difference layer is preferably -50nm~-300nm, preferably -70nm~-250nm, more preferably -90nm~-200nm, and particularly preferably -100nm~-180nm. Here, "nx=ny" includes not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. That is, the in-plane phase difference Re(550) of the other phase difference layer can be less than 10nm.

Other phase difference layers can be formed of any appropriate material. Other phase difference layers are preferably composed of a film containing a liquid crystal material fixed in a homeotropic orientation. The homeotropically oriented liquid crystal material (liquid crystal compound) can be a liquid crystal monomer or a liquid crystal polymer. As a specific example of the liquid crystal compound and the method for forming the phase difference layer, the liquid crystal compound and the method for forming the phase difference layer described in [0020] to [0028] of Japanese Patent Gazette No. 2002-333642 can be cited. At this time, the thickness of the other phase difference layer is preferably 0.5μm~10μm, more preferably 0.5μm~8μm, and more preferably 0.5μm~5μm.

F. Adhesive layer As mentioned above, the storage elastic modulus of the first adhesive layer 50 at 23°C is 0.10MPa or more, preferably 0.10MPa~0.20MPa, more preferably 0.11MPa~0.17MPa, and more preferably 0.11MPa~0.15MPa. As mentioned above, the storage elastic modulus of the second adhesive layer 60 at 23°C is 0.12MPa or more, preferably 0.12MPa~0.25MPa, more preferably 0.13MPa~0.20MPa, and more preferably 0.13MPa~0.18MPa. If the storage elastic modulus of the first adhesive layer and the second adhesive layer is within this range, the effect of the above-mentioned embodiment of the present invention will become more significant. In addition, the storage elastic modulus can be obtained by dynamic viscoelastic measurement.

As mentioned above, the thickness of the first adhesive layer 50 is 17 μm or less, preferably 5 μm to 17 μm, more preferably 8 μm to 16 μm, and more preferably 10 μm to 15 μm. As mentioned above, the thickness of the second adhesive layer 60 is 7 μm or less, preferably 2 μm to 7 μm, more preferably 3 μm to 6 μm, and more preferably 4 μm to 5 μm. If the thickness of the first adhesive layer and the second adhesive layer is within this range, the effect of the above-mentioned embodiment of the present invention will become more significant.

Any suitable structure can be adopted as the adhesive constituting the adhesive layer. Specific examples of the adhesive constituting the adhesive layer include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives and polyether adhesives. By adjusting the type, amount, combination and blending ratio of the monomers forming the base resin of the adhesive, the blending amount of the crosslinking agent, the reaction temperature, the reaction time, etc., an adhesive having the desired properties that meet the purpose can be prepared. The base resin of the adhesive can be used alone or in combination of two or more. From the viewpoints of transparency, processability and durability, an acrylic adhesive (acrylic adhesive composition) is preferred. Typically, the acrylic adhesive composition contains a (meth)acrylic polymer as a main component. The (meth)acrylic polymer can be contained in the adhesive composition at 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 components of the adhesive composition. The (meth)acrylic polymer contains an alkyl (meth)acrylate as a main component as a monomer unit. In addition, (meth)acrylate refers to acrylate and/or methacrylate. The alkyl (meth)acrylate can be contained in the monomer components forming the (meth)acrylic polymer at a ratio of preferably 80% by weight or more, and more preferably 90% by weight or more. As the alkyl group of the (meth)acrylic acid alkyl ester, for example, a straight chain or branched chain alkyl group having 1 to 18 carbon atoms can be cited. The average carbon number of the alkyl group is preferably 3 to 9, more preferably 3 to 6. The ideal (meth)acrylic acid alkyl ester is butyl acrylate. As monomers (comonomers) constituting the (meth)acrylic acid polymer, in addition to the (meth)acrylic acid alkyl ester, carboxyl-containing monomers, hydroxyl-containing monomers, amide-containing monomers, aromatic ring-containing (meth)acrylic acid esters, heterocyclic vinyl monomers, etc. can also be listed. As representative examples of copolymers, acrylic acid, 4-hydroxybutyl acrylate, phenoxyethyl acrylate, and N-vinyl-2-pyrrolidone can be listed. The acrylic adhesive composition can preferably contain a silane coupling agent and/or a crosslinking agent. Examples of the silane coupling agent include epoxy-containing silane coupling agents, and examples of the crosslinking agent include isocyanate crosslinking agents and peroxide crosslinking agents. Furthermore, the acrylic adhesive composition may contain an antioxidant and/or a conductive agent. The details of the adhesive layer or the acrylic adhesive composition are described in, for example, Japanese Patent Publication No. 2006-183022, Japanese Patent Publication No. 2015-199942, Japanese Patent Publication No. 2018-053114, Japanese Patent Publication No. 2016-190996, and International Publication No. 2018/008712, and the descriptions of these publications are cited in this specification as references.

G. Image display device The optical multilayer body described in the above items A to F can be applied to an image display device. Therefore, the embodiment of the present invention also includes an image display device using such an optical multilayer body. As representative examples of image display devices, liquid crystal display devices and organic EL display devices can be cited. The image display device of the embodiment of the present invention has an image display panel and the optical multilayer body described in the above items A to F, and the optical multilayer body is attached to the image display panel through a first adhesive layer. Typically, the optical multilayer body is arranged on the viewing side of the image display panel in such a way that the polarizing plate is on the viewing side.

Examples The present invention is specifically described below by examples, but the present invention is not limited to these examples. The measurement method and evaluation method of each characteristic in the examples are as follows.

(1) Shrinkage rate of polarizer A laminate of the polarizer and triacetate cellulose (TAC) film used in the examples and comparative examples was prepared. The laminate was cut into a size of 4 mm × 16 mm as a test sample. The long side direction of the test sample was made to be the absorption axis direction of the polarizer. The test sample was mounted on a TMA device (manufactured by TA Instruments, product name "Discovery TMA450EM"), and the shrinkage rate at 95°C when measured under the following conditions was taken as the shrinkage rate of the polarizer. Temperature range: -50°C to 120°C Heating rate: 2°C/min Adjustment: 300 seconds/cycle to adjust ±5°C Tensile load: 0.0196N

(2) Indentation elastic modulus and indentation hardness The nanoindenter (manufactured by Hysitron Inc., "Triboindenter") was used to perform the measurement under the following measurement conditions using the nanoindenter method. Specifically, the probe (indenter head) of the nanoindenter was pressed against the surface of the polarizer of the polarizing plate, and the calculation was performed from the displacement-load hysteresis curve using the following formula. Indentation hardness (GPa) = Pmax/A Indentation elastic modulus (GPa) = (√π/2) × (S/√A) Here, Pmax is the maximum load obtained from the displacement-load hysteresis curve, A is the contact projection area between the indenter and the polarizer, S is the slope of the tangent to the unloading curve of the displacement-load hysteresis curve (contact rigidity), and π is the circumference. (Measurement conditions) ・Measurement method: Single indentation method ・Measurement temperature: 25℃ ・Indentation speed: Approximately 2nm/sec ・Indentation depth: Approximately 300nm ・Indenter used: Diamond, Berkovich type (triangular pyramid type) In addition, the indentation elastic modulus of the resin layer was also measured in the same manner.

(3) Cracks The optical laminate obtained in the embodiment and the comparative example was cut into 80 mm × 150 mm. At this time, the cutting was performed in such a way that the absorption axis direction of the polarizer became the short side direction. The cut sheet was attached to the glass plate through the first adhesive layer, and cuts (length 2 mm) were made at 10 locations along the long side and at equal intervals, extending along the short side direction (absorption axis direction of the polarizer) and penetrating to the glass plate. This was used as a test sample. After the test sample was placed in an oven at 95°C for 8 hours, the length of the crack extending from the cut was measured. The average length of the 10 cracks was taken as the crack progression, and the evaluation was performed according to the following criteria. A (excellent): crack progression less than 20mm B (good): crack progression of 20mm or more and less than 40mm C (moderate): crack progression of 40mm or more and less than 60mm D (poor): crack progression of 60mm or more In addition, the above "A" to "D" are relative evaluation standards. In practical terms, crack progression of less than 30mm is evaluated as good, and crack progression of less than 45mm is acceptable.

[Production Example 1: Preparation of polarizer] As a thermoplastic resin substrate, a long amorphous isophthalic acid copolymer polyethylene terephthalate film (thickness: 100 μm) with a Tg of about 75°C was used, and one side of the resin substrate was subjected to a corona treatment. 13 parts by weight of potassium iodide was added to 100 parts by weight of a PVA-based resin obtained by mixing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER") in a ratio of 9:1, and the obtained product was dissolved in water to prepare a PVA aqueous solution (coating liquid). The above-mentioned PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60°C to form a PVA-based resin layer with a thickness of 13 μm to produce a laminate. The obtained laminate was uniaxially stretched to 3.0 times in the longitudinal direction (long side direction) in an oven at 140°C (air-assisted stretching treatment). Then, the laminate was immersed in an insolubilizing bath (aqueous solution of boric acid 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). Next, the laminate was immersed in a dyeing bath (an 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) at a liquid temperature of 30°C for 60 seconds while adjusting the concentration so that the single transmittance (Ts) of the final polarizer would become the desired value (dyeing treatment). Next, it was immersed in a crosslinking bath (an aqueous boric acid 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) at a liquid temperature of 40°C for 30 seconds (crosslinking treatment). Thereafter, the laminate was immersed in a boric acid aqueous solution (boric acid concentration of 4 wt%, potassium iodide concentration of 5 wt%) at a liquid temperature of 64°C, and uniaxially stretched in the longitudinal direction (long side direction) between rollers of different circumferential speeds to achieve a total stretching ratio of 5.5 times (in-water stretching treatment). Thereafter, the laminate was immersed in a cleaning bath (aqueous solution obtained by mixing 3 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20°C (cleaning treatment). Thereafter, it was dried in an oven maintained at approximately 90°C while being brought into contact with a SUS heating roller maintained at a surface temperature of approximately 75°C (drying shrinkage treatment). Here, the conveying tension of the laminate is set to 6N/cm, and the time from the oven entrance to the laminate contacting the heating roller is set to 5 seconds. According to the above operation, a polarizer P1 with a thickness of 5.5μm is formed on the resin substrate to obtain a polarizing plate having a structure of resin substrate/polarizer P1. The shrinkage rate of the polarizer P1 in the absorption axis direction is 2.5%. In addition, the single body transmittance Ts of the polarizer P1 is 43.0%, the indentation elastic modulus is 8.77GPa, and the indentation hardness is 0.688GPa.

[Manufacturing Example 2: Preparation of polarizer] During the heat shrinking treatment, the conveying tension of the laminate was set to 5 N/cm, and the time from the oven entrance to the laminate contacting the heating roller was set to 3.5 seconds. Otherwise, the same operation as in Manufacturing Example 1 was performed to obtain a polarizing plate having a resin substrate/polarizer P2 structure. The shrinkage rate of the polarizer P2 in the absorption axis direction was 1.5%. The single body transmittance, indentation elastic modulus and indentation hardness of the polarizer P2 were the same as those of the polarizer P1 in Manufacturing Example 1.

[Manufacturing Example 3: Preparation of polarizer] Except that the transport tension of the laminate was set to 7N/cm during the heat shrinking treatment, a polarizing plate having a resin substrate/polarizer P3 structure was obtained in the same manner as in Manufacturing Example 1. The shrinkage rate of the polarizer P3 in the absorption axis direction was 3.0%. The single body transmittance, indentation elastic modulus and indentation hardness of the polarizer P3 were the same as those of the polarizer P1 in Manufacturing Example 1.

[Production Example 4: Preparation of a coating liquid for forming a resin layer] 97.0 parts of methyl methacrylate (MMA, manufactured by FUJIFILM Wako Pure Chemical Corporation, trade name "Methyl Methacrylate Polymer"), 3.0 parts of a copolymer represented by the following formula (1e), and 0.2 parts of a polymerization initiator (manufactured by FUJIFILM Wako Pure Chemical Corporation, trade name "2,2'-Azobis (isobutyronitrile)") were dissolved in 200 parts of toluene. Then, a polymerization reaction was carried out for 5.5 hours while heating to 70°C in a nitrogen atmosphere to obtain a boron-containing acrylic resin solution (solid content concentration: 33%). The obtained boron-containing acrylic polymer (resin) had a Tg of 110°C and a Mw of 80,000. 20 parts of the obtained boron-containing acrylic resin was dissolved in 80 parts of methyl ethyl ketone to obtain a coating liquid for forming a resin layer (20% resin solution). [Chemical Formula 3]

[Production Example 5: Preparation of a laminate of phase difference layer/other phase difference layers] 1. Preparation of a phase difference film constituting a phase difference layer In a batch polymerization apparatus consisting of two vertical reactors equipped with stirring blades and a reflux cooler controlled at 100°C, 29.60 parts by weight (0.046 mol) of bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane, 29.21 parts by weight (0.200 mol) of isosorbide (ISB), 42.28 parts by weight (0.139 mol) of spiroglycerol (SPG), 63.77 parts by weight (0.298 mol) of diphenyl carbonate (DPC) and 1.19×10 ^-2 parts by weight (6.78×10 ^-5 mol) of calcium acetate monohydrate as a catalyst were fed. After the reactor was depressurized and replaced with nitrogen, it was heated with a heat medium and agitation was started when the internal temperature reached 100°C. 40 minutes after the start of the temperature rise, the internal temperature reached 220°C, and the pressure was reduced while controlling to maintain the temperature. After reaching 220°C, it was reduced to 13.3 kPa over 90 minutes. The phenol vapor produced as a by-product with the polymerization reaction was introduced into a 100°C reflux cooler, and a certain amount of monomer components contained in the phenol vapor was returned to the reactor. The uncondensed phenol vapor was introduced into a 45°C condenser for recovery. After nitrogen was introduced into the first reactor and the pressure was temporarily restored to atmospheric pressure, the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Next, the temperature and pressure in the second reactor were raised and reduced, and the internal temperature was set to 240°C and the pressure was set to 0.2 kPa in 50 minutes. Thereafter, polymerization was carried out until the predetermined stirring power was reached. When the predetermined power was reached, nitrogen was introduced into the reactor and the pressure was restored. After 0.7 parts by weight of PMMA was melt-kneaded with respect to 100 parts by weight of the generated polyester carbonate resin, the mixture was extruded into water, and the bundle was cut to obtain pellets. The obtained polyester carbonate resin (pellets) was vacuum dried at 80°C for 5 hours, and then a 105μm thick long strip resin film was prepared using a film forming device equipped with a uniaxial extruder (manufactured by Toshiba Machine Co., Ltd., cylinder setting temperature: 250°C), a T-die (width: 200mm, setting temperature: 250°C), a cooling roll (setting temperature: 120~130°C) and a winder. The obtained long strip resin film was stretched 2.8 times in the width direction at 138°C while being adjusted to obtain a predetermined phase difference, thereby obtaining a retardation film (λ/4 plate) with a thickness of 38μm. The Re(550) of the obtained retardation film was 144nm, and the Re(450)/Re(550) was 0.86.

2. Preparation of the laminate of phase difference layer/other phase difference layer 20 parts by weight of the side-chain liquid crystal polymer represented by the following chemical formula (3) (the numbers 65 and 35 in the formula represent the molar percentage of the monomer unit, and for convenience, it is represented as a block polymer: weight average molecular weight 5000), 80 parts by weight of a polymerizable liquid crystal showing a nematic liquid crystal phase (manufactured by BASF: trade name Paliocolor LC242) and 5 parts by weight of a photopolymerization initiator (manufactured by Ciba Specialty Chemicals: trade name Irgacure 907) were dissolved in 200 parts by weight of cyclopentanone to prepare a liquid crystal coating liquid. Then, the coating liquid was applied to a PET substrate subjected to a homeotropic orientation treatment using a rod coater, and then heated and dried at 80°C for 4 minutes to orient the liquid crystal. The liquid crystal layer is irradiated with ultraviolet light to cure the liquid crystal layer, thereby forming a positive C plate (3 μm thick) showing a refractive index characteristic of nz>nx=ny on the substrate. The obtained positive C plate is transferred to the above-mentioned phase difference film through an adhesive layer to obtain a laminate of a λ/4 plate and a positive C plate. [Chemical formula 4]

[Production Example 6: Preparation of the first adhesive layer] (Preparation of acrylic polymer A1) A monomer mixture containing 94.9 parts of butyl acrylate, 0.1 parts of hydroxyethyl acrylate and 5 parts of acrylic acid was added to 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 of ethyl acetate were added to 100 parts of the monomer mixture, and nitrogen was introduced while slowly stirring. After nitrogen substitution, the liquid temperature in the flask was maintained at about 55°C, and a polymerization reaction was carried out for 8 hours to prepare a solution of acrylic polymer A1 with a weight average molecular weight (Mw) of 2.2 million and Mw/Mn=3.9.

(Preparation of adhesive PSA1) 0.6 parts of trihydroxymethylpropane/toluene diisocyanate adduct (manufactured by Tosoh Corporation, trade name "CORONATE L"), 0.3 parts of peroxide crosslinking agent (manufactured by NOF Corporation, trade name "NYPER BMT"), and 0.2 parts of epoxy-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") were mixed with 100 parts of the solid content of the acrylic polymer A1 solution to obtain adhesive PSA1.

[Production Example 7: Preparation of the first adhesive layer] (Preparation of acrylic polymer A2) A monomer mixture containing 87.9 parts of butyl acrylate, 10 parts of 2-ethylhexyl acrylate, 0.1 parts of hydroxyethyl acrylate and 2 parts of acrylic acid was added to a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube and a cooler. Furthermore, 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator and 90 parts of ethyl acetate were added to 100 parts of the monomer mixture, and nitrogen was introduced while slowly stirring. After nitrogen substitution, the liquid temperature in the flask was maintained at around 55°C, and the polymerization reaction was carried out for 8 hours to prepare a solution of acrylic polymer A2 with a weight average molecular weight (Mw) of 2.2 million and Mw/Mn=4.0.

(Preparation of adhesive PSA2) 0.6 parts of trihydroxymethylpropane/toluene diisocyanate adduct (manufactured by Tosoh Corporation, trade name "CORONATE L"), 0.3 parts of peroxide crosslinking agent (manufactured by NOF Corporation, trade name "NYPER BMT") and 0.2 parts of epoxy-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") were mixed with 100 parts of the solid content of the acrylic polymer A2 solution to obtain adhesive PSA2.

[Production Example 8: Preparation of the Second Adhesive Layer] (Preparation of Acrylic Polymer A3) A monomer mixture containing 91 parts of butyl acrylate, 6 parts of acrylamide, 2.7 parts of acrylic acid and 0.3 parts of 4-hydroxybutyl acrylate was added to a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube and a cooler. Furthermore, 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator and 100 parts of ethyl acetate were added to 100 parts of the monomer mixture, and nitrogen was introduced while slowly stirring. After nitrogen substitution, the liquid temperature in the flask was maintained at around 55°C, and the polymerization reaction was carried out for 8 hours to prepare a solution of acrylic polymer A3 with a weight average molecular weight (Mw) of 2.7 million and Mw/Mn=3.8.

(Preparation of adhesive PSA3) With respect to 100 parts of the solid content of the acrylic polymer A3 solution, 0.1 parts of trihydroxymethylpropane/toluene diisocyanate adduct (manufactured by Tosoh Corporation, trade name "CORONATE L"), 0.3 parts of a peroxide crosslinking agent (manufactured by NOF Corporation, trade name "NYPER BMT"), and 0.2 parts of an epoxy-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") were mixed to obtain adhesive PSA3.

[Production Example 9: Preparation of the Second Adhesive Layer] (Preparation of Acrylic Polymer A4) A monomer mixture containing 82.7 parts of butyl acrylate, 10 parts of 2-ethylhexyl acrylate, 6 parts of acrylamide, 1 part of acrylic acid and 0.3 parts of 4-hydroxybutyl acrylate was added to a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube and a cooler. Furthermore, 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator and 90 parts of ethyl acetate were added to 100 parts of the monomer mixture, and nitrogen was introduced while slowly stirring. After nitrogen substitution, the liquid temperature in the flask was maintained at around 55°C, and the polymerization reaction was carried out for 8 hours to prepare a solution of acrylic polymer A4 with a weight average molecular weight (Mw) of 2.6 million and Mw/Mn=3.9.

(Preparation of adhesive PSA4) 0.1 part of trihydroxymethylpropane/toluene diisocyanate adduct (manufactured by Tosoh Corporation, trade name "CORONATE L"), 0.3 part of peroxide crosslinking agent (manufactured by NOF Corporation, trade name "NYPER BMT") and 0.2 part of epoxy-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") were mixed with 100 parts of the solid content of the acrylic polymer A4 solution to obtain adhesive PSA4.

[Example 1] An HC-TAC film is bonded to the surface of the polarizer P1 (the surface opposite to the resin substrate) of the polarizing plate obtained in Manufacturing Example 1 using a UV-curable adhesive. The HC-TAC film is a film having an HC layer (7 μm thick) formed on a cellulose triacetate (TAC) film (25 μm thick), and the film is bonded so that the TAC film is on the polarizer side. Then, the resin substrate is peeled off to obtain a polarizing plate having a structure of HC layer/TAC film (protective layer)/polarizer P1. Next, the coating liquid for forming the resin layer of Manufacturing Example 4 was applied to the surface of the polarizer P1 using a wire rod, and the coating film was dried at 60°C for 5 minutes to form a resin layer (thickness 400nm) in the form of a cured product of the coating film of the resin organic solvent solution. Next, the first adhesive layer PSA1 (thickness 15μm) obtained in Manufacturing Example 6 was arranged on the surface of the resin layer to obtain an optical laminate having a structure of HC layer/TAC film (protective layer)/polarizer P1/resin layer/first adhesive layer PSA1. The obtained optical laminate was provided for the evaluation of the above-mentioned "(3) Cracks". The results are listed in Table 1.

[Examples 2 to 7, Comparative Examples 1 to 7 and Reference Examples 1 to 2] Except that the polarizer, resin layer, phase difference layer, first adhesive layer and second adhesive layer are combined as shown in Table 1, an optical laminate is obtained in the same manner as in Example 1. The obtained optical laminate is subjected to the same evaluation as in Example 1. The results are shown in Table 1. In addition, the "protective layer" of Reference Examples 1 and 2 in the "resin layer" column in the table indicates that a TAC film is used instead of a resin layer.

[Table 1]

[Evaluation] As shown in Table 1, according to the embodiment of the present invention, in an optical laminate in which a specific resin layer is adjacent to a polarizer, if the same structure (structures without a phase difference layer or structures including a phase difference layer) is compared, the cracks of the polarizer in a high temperature environment can be suppressed. It can be further known that by setting a phase difference layer, the cracks will become significant. Moreover, it can be clearly seen from Reference Examples 1 and 2 that in an optical laminate in which a specific resin layer is adjacent to a polarizer, the cracks will become significant.

Industrial Applicability The optical multilayer body of the present invention can be suitably used in image display devices (typically liquid crystal display devices and organic EL display devices).

10: Polarizing plate 11: Polarizer 12: Protective layer 20: Resin layer 30: Phase difference layer 40: Other phase difference layers 50: First adhesive layer 60: Second adhesive layer 100: Optical laminate 101: Optical laminate

FIG1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. FIG2 is a schematic cross-sectional view of an optical laminate according to another embodiment of the present invention.

10: Polarizing plate

11: Polarizer

12: Protective layer

20: Resin layer

50: 1st adhesive layer

100: Optical multilayers

Claims (12)

An optical laminate having: a polarizing plate including a polarizer and a protective layer disposed on one side of the polarizer; a resin layer disposed adjacent to the polarizer; and a first adhesive layer disposed as the outermost layer on the side of the resin layer; The shrinkage rate of the polarizer in the absorption axis direction is less than 2.5%; The thickness of the first adhesive layer is less than 17 μm, and the storage elastic modulus at 23°C is greater than 0.10 MPa. The optical multilayer as claimed in claim 1 further comprises a phase difference layer, which is laminated on the side of the resin layer opposite to the polarizer through a second adhesive layer; The phase difference layer has a circular polarization function or an elliptical polarization function; The thickness of the second adhesive layer is less than 7 μm, and the storage elastic modulus at 23°C is greater than 0.12 MPa. In the optical laminate of claim 2, when the total thickness of the polarizer and the protective layer is set to A (μm), and the total thickness of the resin layer, the second adhesive layer, the phase difference layer and the first adhesive layer is set to B (μm), the optical laminate satisfies the relationship A＜B. The optical multilayer of claim 3, wherein the phase difference layer is formed by a stretched film of a resin film, and its Re(550) is 100nm~200nm, satisfying the relationship of Re(450)＜Re(550), and the angle formed by the slow axis of the phase difference layer and the absorption axis of the polarizer is 40°~50°; Here, Re(450) and Re(550) are the in-plane phase differences measured at 23°C using light of wavelengths of 450nm and 550nm, respectively. The optical layered body of claim 4, wherein the phase difference layer further has another phase difference layer on the side opposite to the resin layer, the refractive index characteristic showing the relationship of nz＞nx=ny. The optical laminate of claim 1, wherein the resin layer comprises a resin having a glass transition temperature of 85°C or higher and a weight average molecular weight Mw of 25,000 or higher. The optical laminate of claim 6, wherein the indentation elastic modulus of the resin layer is greater than 8 GPa. The optical laminate of claim 7, wherein the thickness of the resin layer is less than 1 μm. An optical laminate as claimed in claim 8, wherein the thickness of the polarizer is less than 8 μm, the indentation elastic modulus is less than 9.5 GPa, and the indentation hardness is greater than 0.65 GPa. An optical multilayer as claimed in claim 9, wherein the orientation function of the polarizer is greater than 0.30. An optical laminate as claimed in claim 1, wherein the shrinkage rate of the polarizer in the absorption axis direction is less than 2.0%. An image display device comprises an image display panel and an optical laminate as claimed in any one of claims 1 to 11, wherein the optical laminate is attached to the image display panel via the first adhesive layer.

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