Optical laminate and method for manufacturing an optical laminate

Abstract

To provide an optical laminate in which the occurrence of interference unevenness is sufficiently suppressed. [Solution] An optical laminate comprising at least a first optical layer and a second optical layer laminated via an adhesive layer, wherein the first optical layer is a liquid crystal phase difference layer, the adhesive layer is a cured layer of an adhesive composition containing at least a cationic polymerizable component, a cationic polymerization initiator, and metal oxide particles, and the surface of the first optical layer opposite to the adhesive layer side has the surface irregularities described below. (Surface unevenness) With respect to the average line obtained from line measurement of the surface irregularities of the surface of the first optical layer opposite to the adhesive layer side, the magnitude of the undulation, expressed as the sum of the height D1 at the apex of the highest convex part and the depth D2 of the lower of the two recesses adjacent to the highest convex part (D1+D2), is 100 nm or less.

Description

[Technical Field]

[0001] This invention relates to an optical laminate and a method for manufacturing an optical laminate. The optical laminate can form an image display device such as a liquid crystal display (LCD), an organic light-emitting diode (EL) display, a CRT, or a PDP. [Background technology]

[0002] To improve poor visibility caused by external light reflection and background glare on the display screen of an image display device, an image display device is known in which a circular polarizing plate is placed on the viewing side of the display panel.

[0003] For example, Patent Document 1 below describes a polarizing plate composite comprising a linear polarizing plate, a half-wavelength layer, a first adhesive layer formed by curing an active energy ray curable adhesive, and a quarter-wavelength layer in this order, wherein the angle between the phase-advancing axis of the half-wavelength layer and the transmission axis of the linear polarizing plate is 10° or more and 20° or less, and the absolute value of the difference between the refractive index of the first adhesive layer at a wavelength of 589 nm and the refractive index of the half-wavelength layer in the direction of the phase-advancing axis at a wavelength of 589 nm is less than 0.05.

[0004] Furthermore, Patent Document 2 below describes a polarizing plate with phase difference layers, comprising a polarizer, a first phase difference layer, and a second phase difference layer in that order, wherein the polarizer and the first phase difference layer are bonded together via a first adhesive layer, the first phase difference layer and the second phase difference layer are bonded together via a second adhesive layer, the thickness of the first phase difference layer and the second phase difference layer is 5 μm or less, the average refractive index of the second adhesive layer is 1.55 or more, and the difference between the average refractive index of the first phase difference layer and the average refractive index of the second phase difference layer is less than 0.08.

[0005] Furthermore, Patent Document 3 describes an optical laminate comprising, in this order, a first optical layer, a first adhesive layer formed by curing an active energy ray curable adhesive, and a second optical layer, wherein the surface of the first optical layer facing the first adhesive layer is a liquid crystal layer made of a liquid crystal compound, the active energy ray curable adhesive contains a curable component and a cationic polymerization initiator, the curable component contains 10 to 90 parts by mass of a polyfunctional aromatic epoxy compound having a viscosity of 30 Pa·s or less at a temperature of 25°C when the total amount is 100 parts by mass, and may also contain an alicyclic epoxy compound or a monofunctional epoxy compound, the content of the alicyclic epoxy compound being less than 25 parts by mass and the content of the monofunctional epoxy compound being less than 20 parts by mass, and the first adhesive layer having a refractive index of 1.53 or more at a wavelength of 589 nm.

[0006] Incidentally, Patent Document 4 below describes an active energy ray curable resin composition and cured product that balances various properties required for optical sheets and the like used in optical applications, and is characterized by containing metal oxide nanoparticles (A), phenoxybenzyl (meth)acrylates (B), and a bifunctional (meth)acrylate (C) having a (poly)alkylene glycol structure. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-52365 [Patent Document 2] Japanese Patent Publication No. 2018-17996 [Patent Document 3] Japanese Patent Publication No. 2020-56988 [Patent Document 4] Japanese Patent Publication No. 2017-128688 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] As a result of diligent research by the present inventors, it was found that the technologies described in Patent Documents 1 and 2 above have room for further improvement when it comes to stably improving the refractive index of the interlayer adhesive of the optical laminate. Furthermore, it was found that the technology described in Patent Document 3 above has room for further improvement when it comes to addressing the interference unevenness problem in the optical laminate.

[0009] Furthermore, the technology described in Patent Document 4 relates to an active energy ray-curable resin composition for manufacturing lens sheets, and is not intended for use in bonding at least two optical films. In addition, since the adhesive composition is coated onto the optical film in a very thin film, it is required to have excellent liquid stability when it contains metal oxide particles. However, the technology described in Patent Document 3 does not address such issues, and there is no description or suggestion of means to solve these issues.

[0010] This invention was developed in view of the above circumstances, and aims to provide an optical laminate in which the occurrence of interference unevenness is sufficiently suppressed. [Means for solving the problem]

[0011] The above problems can be solved by the following configuration. That is, the present invention relates to an optical laminate (1) in which at least a first optical layer and a second optical layer are laminated via an adhesive layer, wherein the first optical layer is a liquid crystal phase difference layer, the adhesive layer is a cured layer of an adhesive composition containing at least a cationic polymerizable component, a cationic polymerization initiator and metal oxide particles, and the surface of the first optical layer opposite to the adhesive layer side has the surface irregularities shown below. (Surface unevenness) With respect to the average line obtained by line measurement of the surface irregularities of the surface of the first optical layer opposite to the surface facing the adhesive layer, the magnitude of the undulation, expressed as the sum of the height D1 at the apex of the highest convex part and the depth D2 of the lower of the two recesses adjacent to the highest convex part (D1+D2), is 100 nm or less.

[0012] In the above optical laminate (1), it is preferable that the optical laminate (2) is such that the adhesive composition further contains a radically polymerizable compound.

[0013] In the above optical laminate (1) or (2), it is preferable that the optical laminate (3) is such that the refractive index of the adhesive layer is 1.54 or more.

[0014] In any one of the above optical laminates (1) to (3), it is preferable that the optical laminate (4) is such that when the total amount in the composition is 100% by mass, the content of the metal oxide particles is 5 to 50% by mass.

[0015] In any one of the above optical laminates (1) to (4), it is preferable that the optical laminate (5) is such that the adhesive composition further contains a (meth)acrylate containing an aromatic ring skeleton.

[0016] In the above optical laminate (5), it is preferable that the optical laminate (6) is such that the (meth)acrylate containing an aromatic ring skeleton contains at least one selected from the group consisting of a (meth)acrylate having a polycyclic aromatic ring skeleton and a (meth)acrylate having two or more aromatic rings.

[0017] In the above optical laminate (5), it is preferable that the optical laminate (7) is such that the (meth)acrylate containing an aromatic ring skeleton is phenoxybenzyl (meth)acrylate.

[0018] In any one of the above optical laminates (1) to (7), it is preferable that the optical laminate (8) is such that the adhesive composition contains at least one selected from the group consisting of an alicyclic epoxy compound, an aromatic epoxy compound, an aromatic oxetane compound, and a bifunctional oxetane compound as the cationic polymerizable component.

[0019] In any of the above optical laminates (1) to (8), an optical laminate (9) is preferred in which the adhesive composition contains at least one selected from the group consisting of zinc oxide, zirconium oxide, and titanium oxide as the metal oxide particles.

[0020] In any of the above optical laminates (1) to (9), an optical laminate (10) in which the average particle size of the metal oxide particles is 100 nm or less is preferred.

[0021] In any of the above optical laminates (1) to (10), an optical laminate (11) in which the thickness of the adhesive layer is 0.3 to 3.0 μm is preferred.

[0022] The present invention also relates to a method for manufacturing an optical laminate in which at least a first optical layer and a second optical layer are laminated via an adhesive layer, comprising: a coating step of applying an adhesive composition to one or both of the bonding surfaces of the first optical layer and the second optical layer; a bonding step of bonding the first optical layer and the second optical layer together; and an adhesion step of bonding the first optical layer and the second optical layer via the adhesive layer formed by irradiating at least the adhesive composition with active energy rays from the surface side of the first optical layer or the surface side of the second optical layer, wherein the first optical layer is a liquid crystal phase difference layer, and the adhesive layer is a cured layer of an adhesive composition containing at least a cationic polymerizable component, a cationic polymerization initiator, and metal oxide particles (11).

[0023] In the above method for manufacturing an optical laminate (11), a method for manufacturing an optical laminate (12) is preferred in which the viscosity of the adhesive composition at 25°C is 100 [mPa·s] or less. [Effects of the Invention]

[0024] In optical laminates, particularly those equipped with a liquid crystal phase difference layer, suppressing interference unevenness is especially important. To suppress interference unevenness in optical laminates, the inventors diligently studied the surface irregularities of the adhesive layer constituting the optical laminate. As a result, it was found that liquid crystal phase difference layers, which are particularly brittle and have poor shape retention, develop similar irregularities on their surface to follow the irregularities that occur on the surface of the adhesive layer, making them prone to interference unevenness in the optical laminate. Further diligent research by the inventors revealed that by forming the adhesive layer constituting the optical laminate with a cured layer of a specific adhesive composition, and by designing the surface irregularities of the surface of the liquid crystal phase difference layer (the surface opposite to the adhesive layer side) within a specific range, interference unevenness in the optical laminate can be sufficiently suppressed.

[0025] Specifically, when laminating a first optical layer, which is a liquid crystal phase difference layer, with a second optical layer, an adhesive layer is formed by a cured layer of an adhesive composition containing at least a cationic polymerizable component, a cationic polymerization initiator, and metal oxide particles. By designing the surface roughness of the surface of the first optical layer opposite to the adhesive layer side as described below, interference unevenness in the optical laminate can be sufficiently suppressed. (Surface unevenness) The optical laminate is designed such that the surface roughness is 100 nm or less, represented by the sum of the height D1 at the apex of the highest convex part and the depth D2 of the lower of the two recesses adjacent to the highest convex part (D1+D2) relative to the average line obtained by line measurement of the surface roughness of the surface opposite to the adhesive layer side of the first optical layer. The method for measuring surface roughness in this invention will be described later.

[0026] In the present invention, the reason why interference unevenness in the optical laminate can be sufficiently suppressed is not clear, but it can be presumed as follows: The metal oxide particles contained in the adhesive composition for forming the adhesive layer expand less due to thermal changes and are less prone to deformation compared to the resin components used in conventional adhesives. Therefore, when the adhesive composition is applied to the first optical layer and / or the second optical layer, coating streaks of the adhesive composition are less likely to occur, and shrinkage of the adhesive composition is less likely to occur after application. As a result, when the adhesive composition applied to a liquid crystal phase difference layer (first optical layer), which is particularly brittle and has poor shape retention, is cured and a cured layer (adhesive layer) is formed, the occurrence of surface irregularities in the adhesive layer is suppressed, which makes it possible to sufficiently reduce changes in surface irregularities on the surface of the liquid crystal phase difference layer (the surface opposite to the adhesive layer side), thereby sufficiently suppressing interference unevenness in the optical laminate.

[0027] In the optical laminate according to the present invention, the adhesive layer is formed using a cationic adhesive composition containing a cationic polymerizable component, a cationic polymerization initiator, and metal oxide particles. However, only a cationic polymerizable component may be used as the polymerizable component, or a "cationic / radical hybrid system" may be used, which combines a cationic polymerizable component and a radical polymerizable compound.

[0028] When manufacturing the optical laminate according to the present invention, lowering the viscosity of the adhesive composition for forming the adhesive layer, specifically designing the viscosity of the adhesive composition at 25°C to 100 [mPa·s] or less, further suppresses the occurrence of coating streaks when coating the first optical layer and / or the second optical layer with the adhesive composition. As a result, when the cured layer (adhesive layer) is formed, the occurrence of surface irregularities in the adhesive layer is suppressed, which further reduces changes in the surface irregularities of the liquid crystal phase difference layer (the surface opposite to the adhesive layer side), thereby sufficiently further suppressing interference unevenness in the optical laminate. [Brief explanation of the drawing]

[0029] [Figure 1] An example of an optical laminate according to the present invention [Figure 2] Enlarged schematic diagram showing the measurement of surface roughness on the surface opposite to the adhesive layer side of the first optical layer. [Modes for carrying out the invention]

[0030] Figure 1 shows an example of an optical laminate according to the present invention. In the optical laminate 10 shown in Figure 1, a first optical layer 1 and a second optical layer 2 are laminated via an adhesive layer 3, which is a cured layer of an adhesive composition. The adhesive composition used in the present invention to form the adhesive layer 3 has a high refractive index in its cured layer due to the stable dispersion of metal oxide particles. Therefore, when, for example, a phase difference layer, preferably a liquid crystal phase difference layer, is used as the first optical layer 1 and the second optical layer 2, the refractive index difference between the first optical layer 1 and the adhesive layer 3 can be reduced, and similarly, the refractive index difference between the second optical layer 2 and the adhesive layer 3 can be reduced, thereby suppressing interference unevenness in the optical laminate and improving visibility. Furthermore, as described above, by forming the adhesive layer 3 constituting the optical laminate 10 with a cured layer of a specific adhesive composition and designing the surface irregularities of the surface of the liquid crystal phase difference layer (first optical layer 1) (the surface opposite to the side facing the adhesive layer 3) within a specific range, interference unevenness in the optical laminate 10 can be sufficiently suppressed.

[0031] The optical laminate according to the present invention is an optical laminate in which at least a first optical layer and a second optical layer are laminated via an adhesive layer which is a cured product layer of an adhesive composition, and may further include any optical film or the like. The optical laminate 10 shown in Figure 1 includes a polarizer 5 on top of the second optical layer 2 (viewing side), and further includes a transparent protective film 4. Normally, an adhesive layer or a tack layer is provided between the second optical layer 2 and the polarizer 5, and between the polarizer 5 and the transparent protective film 4 (omitted in Figure 1), but if it is an adhesive layer, it may be the same as the adhesive layer 3 which is a cured product layer of the adhesive composition used in the present invention, or it may be a cured product layer of an adhesive composition known to those skilled in the art. If it is a tack layer, it may also be a tack layer known to those skilled in the art. Furthermore, the optical laminate 10 shown in Figure 1 includes an organic light-emitting diode layer 7 below the first optical layer 1 (display device side) via a tack layer 6.

[0032] The optical laminate according to the present invention comprises at least a first optical layer and a second optical layer laminated with an adhesive layer in between. The adhesive layer is formed of a cured layer of an adhesive composition containing at least a cationic polymerizable component, a cationic polymerization initiator, and metal oxide particles. The adhesive composition used as the raw material for the adhesive layer will be described below.

[0033] <Metal oxide particles> The adhesive composition used in the present invention contains metal oxide particles. Examples of metal oxide particles include silicon oxide, zirconium oxide, titanium oxide, zinc oxide, antimony pentoxide, tin oxide, aluminum oxide, indium oxide, indium tin oxide, ferric oxide, cerium oxide, yttrium oxide, manganese oxide, holomium oxide, copper oxide, bismuth oxide, cobalt oxide, cobalt trioxide, iron trioxide, magnesium oxide, lanthanum oxide, praseodymium oxide, neodymium oxide, samarium oxide, eurobium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide, scandium oxide, tantalum pentoxide, niobium pentoxide, iridium oxide, rhodium oxide, ruthenium oxide, and composite oxides formed by combining these. Among these, zinc oxide, zirconium oxide, and titanium oxide are preferred, and zirconium oxide is particularly preferred. The metal oxide particles used in this invention may consist solely of the metal oxides listed above, or they may contain other components, but it is preferable that metal oxides constitute the largest weight component in the particles. The shape of the metal oxide particles can be any shape, such as spherical, ellipsoidal, cuboidal, rectangular prism, or pyramidal. In this invention, metal oxide particles that have been surface-treated by methods known to those skilled in the art may be used.

[0034] From the viewpoint of improving the stability of metal oxide particles in the adhesive composition and improving the refractive index of the adhesive layer, the average particle diameter of the metal oxide particles used is preferably 1 to 150 nm, more preferably 1 to 100 nm, and particularly preferably 1 to 50 nm. In the present invention, the average particle diameter of the metal oxide particles can be calculated by observing them under magnification using a transmission electron microscope (TEM), field emission transmission electron microscope (FE-TEM), and field emission scanning electron microscope (FE-SEM), randomly selecting, for example, 1000 particles, measuring their maximum length, and calculating their arithmetic mean.

[0035] The average particle size of metal oxide particles incorporated into an adhesive composition can also be calculated using dynamic light scattering or laser diffraction. When calculated using dynamic light scattering or laser diffraction, the average particle size refers to the particle size at 50% of the integrated value in the particle size distribution obtained by laser diffraction / scattering.

[0036] From the viewpoint of improving the stability of metal oxide particles in the adhesive composition and improving the refractive index of the adhesive layer, the amount of metal oxide particles used is preferably 5 to 50% by mass, and more preferably 8 to 40% by mass, when the total amount in the composition is 100% by mass.

[0037] <Curing component> The adhesive composition used in the present invention contains a curable component. In the present invention, the curable component is preferably an active energy ray curable component. Active energy ray curable components can be classified into cationic polymerization curable components (cationic polymerizable components) and radical polymerization curable components (radical polymerizable compounds). In the present invention, active energy rays with a wavelength range of 10 nm to less than 380 nm are referred to as ultraviolet rays, and active energy rays with a wavelength range of 380 nm to 800 nm are referred to as visible light.

[0038] The adhesive composition used in the present invention contains at least a cationic polymerizable component. Cationic polymerizable components (cationic polymerizable compounds) are classified into monofunctional cationic polymerizable compounds having one cationic polymerizable functional group in the molecule, and polyfunctional cationic polymerizable compounds having two or more cationic polymerizable functional groups in the molecule. Monofunctional cationic polymerizable compounds have relatively low liquid viscosity, so including them in the adhesive composition can reduce the liquid viscosity. Furthermore, monofunctional cationic polymerizable compounds often have functional groups that exhibit various functions, so including them in the adhesive composition can exhibit various functions in the adhesive composition and / or the cured product of the adhesive composition. Polyfunctional cationic polymerizable compounds can cause three-dimensional crosslinking of the cured product of the adhesive composition, so it is preferable to include them in the adhesive composition. The ratio of monofunctional cationic polymerizable compounds to polyfunctional cationic polymerizable compounds is preferably a mixture of 10% to 1000% by mass of the polyfunctional cationic polymerizable compound with 100% by mass of the monofunctional cationic polymerizable compound. Examples of cationic polymerizable functional groups include epoxy groups, oxetanyl groups, and vinyl ether groups.

[0039] Examples of epoxy group-containing compounds include aliphatic epoxy compounds, alicyclic epoxy compounds, and aromatic epoxy compounds. The adhesive composition of the present invention is particularly preferably composed of alicyclic epoxy compounds due to its excellent curability and adhesive properties. Examples of alicyclic epoxy compounds include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, caprolactone-modified, trimethylcaprolactone-modified, and valerolactone-modified 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate. Specifically, examples include Celoxide 2021, Celoxide 2021A, Celoxide 2021P, Celoxide 2081, Celoxide 2083, and Celoxide Examples include 2085 (manufactured by Daicel Chemical Industries, Ltd.), Cyracure UVR-6105, Cyracure UVR-6107, Cyracure 30, and R-6110 (all manufactured by Dow Chemical Japan Ltd.). Compounds having an oxetanyl group (oxetane compounds) are preferable to include because they have the effect of improving the curability of the adhesive composition and reducing the liquid viscosity of the composition, and it is more preferable to include aromatic oxetane compounds or bifunctional oxetane compounds.

[0040] Examples of oxetane compounds include 3-ethyl-3-hydroxymethyl oxetane, 1,4-bis[(3-ethyl-3-oxetanyl)methoxymethyl]benzene, 3-ethyl-3-(phenoxymethyl)oxetane, di[(3-ethyl-3-oxetanyl)methyl]ether, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, and phenol novolac oxetane. Aronoxetane OXT-101, Aronoxetane OXT-121, Aronoxetane OXT-211, Aronoxetane OXT-221, and Aronoxetane OXT-212 (all manufactured by Toagosei Co., Ltd.) are commercially available. Compounds having a vinyl ether group are preferable to include because they have the effect of improving the curability of cationic polymerizable adhesive compositions and reducing the liquid viscosity of the composition.

[0041] Examples of compounds having a vinyl ether group include 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, triethylene glycol divinyl ether, cyclohexanedimethanol divinyl ether, cyclohexanedimethanol monovinyl ether, tricyclodecane vinyl ether, cyclohexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, and pentaerythritol-type tetravinyl ether.

[0042] The adhesive composition used in the present invention contains at least one compound selected from the epoxy group-containing compounds, oxetanyl group-containing compounds (oxetane compounds), and vinyl ether group-containing compounds described above as curable components, all of which cure by cationic polymerization; therefore, a photocationic polymerization initiator is included. This photocationic polymerization initiator generates cationic species or Lewis acids upon irradiation with active energy rays such as visible light, ultraviolet light, X-rays, and electron beams, and initiates the polymerization reaction of epoxy groups and oxetanyl groups. As the photocationic polymerization initiator, a photoacid generator described later is preferably used. Furthermore, when using a cationic polymerizable adhesive composition that is curable with visible light, it is preferable to use a photocationic polymerization initiator that is particularly sensitive to light of 380 nm or higher. However, since photocationic polymerization initiators are generally compounds that exhibit maximum absorption in the wavelength range of around 300 nm or shorter, by incorporating a photosensitizer that exhibits maximum absorption in the wavelength range of longer than that, specifically light with wavelengths longer than 380 nm, it is possible to stimulate light of this wavelength range and promote the generation of cationic species or acids from the photocationic polymerization initiator. Examples of photosensitizers include anthracene compounds, pyrene compounds, carbonyl compounds, organosulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, and photoreducible dyes, and two or more of these may be used in mixture form. Anthracene compounds are particularly preferred because they have an excellent photosensitizing effect, and specific examples include Anthracure UVS-1331 and Anthracure UVS-1221 (manufactured by Kawasaki Chemical Co., Ltd.). The photosensitizer content is preferably 0.1% to 5% by mass, and more preferably 0.5% to 3% by mass.

[0043] In the optical laminate according to the present invention, the adhesive layer is formed using a cationic adhesive composition containing a cationic polymerizable component, a cationic polymerization initiator, and metal oxide particles. However, only a cationic polymerizable component may be used as the polymerizable component, or a "cationic / radical hybrid system" using a cationic polymerizable component and a radical polymerizable compound in combination may be used. However, even in the case of a "cationic / radical hybrid system," from the viewpoint of sufficiently suppressing interference unevenness in the optical laminate, the content of the cationic polymerizable component is preferably 5 to 99% by mass, and more preferably 20 to 95% by mass, when the total amount in the composition is 100% by mass.

[0044] When the adhesive composition used in the present invention is a "cationic / radical hybrid system," it may contain a monofunctional radical polymerizable compound as a curing component. Examples of monofunctional radical polymerizable compounds include various (meth)acrylic acid derivatives having a (meth)acryloyloxy group. Specifically, examples include alkyl esters of (meth)acrylic acid (with 1-20 carbon atoms), such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, 2-methyl-2-nitropropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, t-pentyl (meth)acrylate, 3-pentyl (meth)acrylate, 2,2-dimethylbutyl (meth)acrylate, n-hexyl (meth)acrylate, cetyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 4-methyl-2-propylpentyl (meth)acrylate, and n-octadecyl (meth)acrylate.

[0045] Furthermore, examples of the (meth)acrylic acid derivatives include cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate and cyclopentyl (meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate; 2-isobornyl (meth)acrylate, 2-norbornylmethyl (meth)acrylate, 5-norbornen-2-ylmethyl (meth)acrylate, 3-methyl-2-norbornylmethyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentenyl oxy Examples include polycyclic (meth)acrylates such as ethyl (meth)acrylate and dicyclopentanyl (meth)acrylate; and alkoxy group or phenoxy group-containing (meth)acrylates such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-methoxymethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ethyl carbitol (meth)acrylate, phenoxyethyl (meth)acrylate, and alkylphenoxypolyethylene glycol (meth)acrylate. Among these, dicyclopentenyloxyethyl acrylate and phenoxyethyl acrylate are preferred due to their excellent adhesion to various protective films.

[0046] Furthermore, the (meth)acrylic acid derivatives include hydroxyalkyl( )acrylates such as 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 3-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate, 6-hydroxyhexyl(meth)acrylate, 8-hydroxyoctyl(meth)acrylate, 10-hydroxydecyl(meth)acrylate, and 12-hydroxylauryl(meth)acrylate. Hydroxyl group-containing (meth)acrylates such as meth)acrylate, [4-(hydroxymethyl)cyclohexyl]methyl acrylate, cyclohexanedimethanol mono(meth)acrylate, and 2-hydroxy-3-phenoxypropyl(meth)acrylate; epoxy group-containing (meth)acrylates such as glycidyl(meth)acrylate and 4-hydroxybutyl(meth)acrylate glycidyl ether; 2,2,2-trifluoroethyl(meth)acrylate and 2,2,2-trifluoroethyl(meth)acrylate Halogen-containing (meth)acrylates such as acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropentyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, and 3-chloro-2-hydroxypropyl (meth)acrylate; alkylaminoalkyl (meth)acrylates such as dimethylaminoethyl (meth)acrylate; 3-oxetanylmethyl (meth)acrylate, 3-methyl-oxetanylmethyl (meth)acrylate Examples include oxetane group-containing (meth)acrylates such as rilate, 3-ethyl-oxetanylmethyl (meth)acrylate, 3-butyl-oxetanylmethyl (meth)acrylate, and 3-hexyl-oxetanylmethyl (meth)acrylate; heterocyclic (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate and butyrolactone (meth)acrylate; and neopentyl glycol (meth)acrylic acid adducts of hydroxypivalate and p-phenylphenol (meth)acrylate. Among these, 2-hydroxy-3-phenoxypropyl acrylate is preferred due to its excellent adhesion to various protective films.

[0047] When the adhesive composition used in the present invention is a "cationic / radical hybrid system," it is preferable that the adhesive composition contains hydroxyl group-containing (meth)acrylate in addition to metal oxide particles, as this further improves the adhesive strength of the adhesive layer. From the viewpoint of improving the adhesive strength of the adhesive layer, the amount of hydroxyl group-containing (meth)acrylate blended is preferably 3 to 15% by mass when the total amount in the composition is 100% by mass.

[0048] Furthermore, examples of monofunctional radical polymerizable compounds include carboxyl group-containing monomers such as (meth)acrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

[0049] Examples of monofunctional radical polymerizable compounds include lactam-based vinyl monomers such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam, and methylvinylpyrrolidone; and vinyl monomers having nitrogen-containing heterocyclic rings such as vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, and vinylmorpholine.

[0050] Furthermore, as a monofunctional radical polymerizable compound, a radical polymerizable compound having an active methylene group can be used. A radical polymerizable compound having an active methylene group is a compound that has an active double bond group such as a (meth)acrylic group at its terminal or in the molecule, and also has an active methylene group. Examples of active methylene groups include an acetoacetyl group, an alkoxymalonyl group, or a cyanoacetyl group. It is preferable that the active methylene group is an acetoacetyl group. Specific examples of radical polymerizable compounds having an active methylene group include acetoacetoxyalkyl (meth)acrylates such as 2-acetoacetoxyethyl (meth)acrylate, 2-acetoacetoxypropyl (meth)acrylate, and 2-acetoacetoxy-1-methylethyl (meth)acrylate; 2-ethoxymalonyloxyethyl (meth)acrylate, 2-cyanoacetoxyethyl (meth)acrylate, N-(2-cyanoacetoxyethyl)acrylamide, N-(2-propionylacetoxybutyl)acrylamide, N-(4-acetoacetoxymethylbenzyl)acrylamide, and N-(2-acetoacetylaminoethyl)acrylamide. The radical polymerizable compound having an active methylene group is preferably an acetoacetoxyalkyl (meth)acrylate.

[0051] When the adhesive composition used in the present invention is a "cationic / radical hybrid system," it may contain a polyfunctional radical polymerizable compound as a curing component. Examples of polyfunctional radical polymerizable compounds include polyfunctional (meth)acrylamide derivatives such as N,N'-methylenebis(meth)acrylamide, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol diacrylate, 2-ethyl-2-butylpropanediol di(meth)acrylate, bisphenol A di(meth)acrylate, bisphenol A ethylene oxide adduct di(meth)acrylate, bisphenol A propylene oxide adduct di(meth)acrylate, and bisphenol A diglycidyl ether di(meth)acrylate. Examples include esters of (meth)acrylic acid with polyhydric alcohols such as phosphate, neopentyl glycol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, cyclic trimethylolpropane formal(meth)acrylate, dioxane glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and EO-modified diglycerin tetra(meth)acrylate, as well as 9,9-bis[4-(2-(meth)acryloyloxyethoxy)phenyl]fluorene. Specific examples include Aronics M-220 (manufactured by Toagosei Co., Ltd.), Light Acrylate 1,9ND-A (manufactured by Kyoeisha Chemical Co., Ltd.), Light Acrylate DGE-4A (manufactured by Kyoeisha Chemical Co., Ltd.), Light Acrylate DCP-A (manufactured by Kyoeisha Chemical Co., Ltd.), SR-531 (manufactured by Sartomer), and CD-536 (manufactured by Sartomer). Additionally, various epoxy (meth)acrylates, urethane (meth)acrylates, polyester (meth)acrylates, and various (meth)acrylate monomers may be used as needed.Furthermore, polyfunctional (meth)acrylamide derivatives are preferable to include in adhesive compositions because they have a fast polymerization rate, excellent productivity, and excellent crosslinking properties when the adhesive composition is cured.

[0052] For example, when using a polarizer and a transparent protective film as an optical layer, it is preferable to use a combination of monofunctional and polyfunctional radical polymerizable compounds to achieve both good adhesion to the polarizer and various transparent protective films, and optical durability in harsh environments.

[0053] <(meth)acrylate containing an aromatic ring skeleton> The adhesive composition used in the present invention is preferable if it contains a (meth)acrylate containing an aromatic ring skeleton together with metal oxide particles, as this improves the refractive index of the adhesive layer. From the viewpoint of more stably increasing the refractive index of the adhesive layer, in the present invention, it is preferable to use a (meth)acrylate containing an aromatic ring skeleton that contains at least one selected from the group consisting of (meth)acrylates having a polycyclic aromatic ring skeleton and (meth)acrylates having two or more aromatic rings. Examples of (meth)acrylates containing an aromatic ring skeleton include benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 1-naphthalenemethyl (meth)acrylate, phenoxybenzyl (meth)acrylate, ethylene oxide-modified orthophenylphenol (meth)acrylate, and reaction products of 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene and (meth)acrylic acid. Among these, the use of phenoxybenzyl (meth)acrylate and phenoxyethyl (meth)acrylate is more preferred, and the use of phenoxybenzyl (meth)acrylate is particularly preferred. Phenoxybenzyl (meth)acrylate is given by the following formula (A): [ka] The compound has a structure represented by the formula (A) above. In formula (A) above, X is either a single bond forming part of an adjacent bonding group, or a structure having 1 to 5 repeating ethylene oxide, propylene oxide, butylene oxide, or styrene oxide structures. R represents a hydrogen atom or a methyl group. The adhesive composition used in the present invention is the following formula (A-1): [ka] It is preferable to contain phenoxybenzyl (meth)acrylate, which is an o- or m-substituted derivative represented by .

[0054] From the viewpoint of improving the refractive index of the adhesive layer, the amount of (meth)acrylate containing an aromatic ring skeleton used, particularly phenoxybenzyl (meth)acrylate, is preferably 5 to 50% by mass when the total amount in the composition is 100% by mass.

[0055] The adhesive composition used in the present invention is preferable if it contains at least one compound selected from the group consisting of isocyanurate compounds and polysiloxane compounds, because this allows for stable dispersion of metal oxide particles.

[0056] When applying the adhesive composition to the first optical layer and / or the second optical layer, it is preferable to set the viscosity of the composition at 25°C to 100 [mPa·s] or less, and more preferably to 60 [mPa·s] or less, from the viewpoint of effectively suppressing the occurrence of coating streaks and further from the viewpoint of thinning the adhesive layer and the optical laminate.

[0057] <Leveling agent> The adhesive composition used in the present invention preferably contains a polysiloxane compound as a leveling agent. The inclusion of a polysiloxane compound in the composition results in excellent liquid stability of the adhesive composition due to the stable dispersion of metal oxide particles. Furthermore, the inclusion of both metal oxide particles and a polysiloxane compound in the composition suppresses the generation of repellency and bubbles during coating on optical films.

[0058] <Polysiloxane compounds> Polysiloxane compounds are compounds having a polysiloxane skeleton, such as polydimethylsiloxane. In the present invention, it is particularly preferable to use a modified polysiloxane compound having a reactive group. Examples of reactive groups in modified polysiloxane compounds include polymerizable functional groups, specifically radical polymerizable functional groups having an ethylenically double bond, such as (meth)acryloyl groups, vinyl groups, and allyl groups; epoxy groups such as glycidyl groups; and cationic polymerizable functional groups such as oxetane groups, vinyl ether groups, cyclic ether groups, cyclic thioether groups, and lactone groups. From the viewpoint of reactivity in the adhesive composition, a modified polysiloxane compound having a double bond as the reactive group is preferred, and a modified polysiloxane compound having a (meth)acryloyl group is more preferred. The amount of polysiloxane compound blended in the adhesive composition is preferably 0.05 to 1.0% by mass, when the total amount in the composition is 100% by mass.

[0059] The adhesive composition used in the present invention can be used as an active energy ray curable adhesive composition when the curable component is used as an active energy ray curable component. When an electron beam or the like is used as the active energy ray, it is not necessary for the active energy ray curable adhesive composition to contain a photopolymerization initiator. However, when the adhesive composition used in the present invention is a "cation / radical hybrid system" and ultraviolet light or visible light is used as the active energy ray, it is preferable to include a photopolymerization initiator.

[0060] The photopolymerization initiator is appropriately selected based on the active energy ray. When curing is performed by ultraviolet or visible light, a photopolymerization initiator that undergoes ultraviolet or visible light cleavage is used. Examples of the aforementioned photopolymerization initiators include benzophenone compounds such as benzyl, benzophenone, benzoylbenzoic acid, and 3,3'-dimethyl-4-methoxybenzophenone; aromatic ketone compounds such as 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone, α-hydroxy-α,α'-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, and α-hydroxycyclohexylphenyl ketone; acetophenone compounds such as methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, and 2-methyl-1-[4-(methylthio)-phenyl]-2-morpholinopropane-1; benzioin methyl ether, benzioin ethyl ether, benzoin isopropyl ether, and Examples include benzoin ether compounds such as benzoin butyl ether and anisoin methyl ether; aromatic ketal compounds such as benzyldimethyl ketal; aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; photoactive oxime compounds such as 1-phenone-1,1-propanedione-2-(o-ethoxycarbonyl)oxime; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone; camphorquinone; halogenated ketones; acylphosphinoxides; and acylphosphonates.

[0061] The amount of the photopolymerization initiator is preferably 0.5 to 5% by mass, and more preferably 1 to 4% by mass, when the total amount in the composition is considered as 100% by mass.

[0062] Furthermore, when using an active energy ray-curable adhesive composition in a visible light curing type, it is preferable to use a photopolymerization initiator that is particularly sensitive to light of 380 nm or higher. Photopolymerization initiators that are highly sensitive to light of 380 nm or higher will be described later.

[0063] The aforementioned photopolymerization initiator is a compound represented by the following general formula (3); [ka] (In the formula, R 7 and R 8 R represents -H, -CH2CH3, -iPr, or Cl. 7 and R 8 It is preferable to use the compound represented by general formula (3) alone (which may be the same or different) or to use it in combination with a photopolymerization initiator that is highly sensitive to light of 380 nm or higher, as described later. When the compound represented by general formula (3) is used, the adhesion is superior to when the photopolymerization initiator that is highly sensitive to light of 380 nm or higher is used alone. Among the compounds represented by general formula (3), R 7 and R 8 Diethylthioxanthones, where -CH2CH3, are particularly preferred. The amount of the compound represented by general formula (3) in the active energy ray curable adhesive composition is preferably 0.1 to 5% by mass, and more preferably 0.3 to 3% by mass, when the total amount in the composition is 100% by mass.

[0064] Furthermore, it is preferable to add polymerization initiators as needed. Examples of polymerization initiators include triethylamine, diethylamine, N-methyldiethanolamine, ethanolamine, 4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, and isoamyl 4-dimethylaminobenzoate, with ethyl 4-dimethylaminobenzoate being particularly preferred. When using polymerization initiators, the amount added is preferably 0.1 to 2% by mass, and more preferably 0.3 to 1% by mass, when the total amount in the composition is considered as 100% by mass.

[0065] Furthermore, known photopolymerization initiators can be used in combination as needed. Since the optical functional layer and substrate film having UV absorption ability do not transmit light below 380 nm, it is preferable to use a photopolymerization initiator that is highly sensitive to light above 380 nm. Specifically, examples include 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrole-1-yl)-phenyl)titanium.

[0066] The optical laminate according to the present invention is an optical laminate in which at least a first optical layer and a second optical layer are laminated with an adhesive layer in between, wherein the adhesive layer is a cured product layer of the adhesive composition described above.

[0067] The adhesive composition used in the present invention contains metal oxide particles, but if it further contains at least one selected from the group consisting of isocyanurate compounds and polysiloxane compounds, the viscosity of the composition can be kept low due to the stable dispersion of the metal oxide particles. Therefore, the adhesive composition can be thinly coated onto the optical film, and thus the thickness of the adhesive layer can be reduced.

[0068] The thickness of the adhesive layer in the optical laminate according to the present invention is preferably 0.1 to 5 μm, and more preferably 0.3 to 3.0 μm.

[0069] Examples of the first optical layer and the second optical layer constituting the optical laminate in this invention include a phase difference layer, a polarizer, and a transparent protective film.

[0070] Examples of phase difference layers include birefringent films made by uniaxial or biaxial stretching of polymer materials, orientation films of liquid crystal polymers, and orientation layers of liquid crystal polymers supported by films. The thickness of the phase difference layer is not particularly limited, but it is generally around 1 to 150 μm.

[0071] The phase difference layer is given by the following equations (1) to (3): 0.70 <Re

[0450] / Re

[0550] <0.97···(1) 1.5 × 10 -3 <Δn<6×10 -3 ...(2) 1.13 <NZ<1.50···(3) A reverse wavelength-dispersive phase difference layer that satisfies the following equation may also be used: (In the equation, Re

[0450] and Re

[0550] are the in-plane phase difference values ​​of the phase difference layer measured with light of wavelengths 450 nm and 550 nm at 23°C, respectively; Δn is the in-plane birefringence nx-ny when the refractive indices in the slow phase axis direction and the fast phase axis direction of the phase difference layer are nx and ny, respectively; and NZ is the ratio of the thickness-direction birefringence nx-nz to the in-plane birefringence nx-ny when nz is the refractive index in the thickness direction of the phase difference layer).

[0072] Liquid crystalline compounds are preferably used to form the phase difference layer. A solvent containing the liquid crystalline compound can be applied using, for example, a wire bar, gap coater, comma coater, gravure coater, or slot die. The applied liquid crystalline solution may be air-dried or heat-dried. It is preferable to apply the liquid crystalline solution at a concentration lower than the isotropic phase-liquid crystal phase transition concentration, i.e., in an isotropic phase state. In this case, the solution can be stably oriented by methods such as rubbing or photo-alignment.

[0073] In the present invention, the polarizer is not particularly limited and various types can be used. Examples of polarizers include hydrophilic polymer films such as polyvinyl alcohol-based films, partially formalized polyvinyl alcohol-based films, and partially saponified ethylene-vinyl acetate copolymer films, to which iodine is adsorbed and then uniaxially stretched. Examples of polarizer thickness include 3 to 20 μm.

[0074] However, in this invention, from the viewpoint of improving heat resistance in harsh environments at high temperatures, it is preferable to use a thin polarizer with a thickness of 3 μm or more and 15 μm or less as the polarizer. It is particularly preferable that the thickness be 12 μm or less, even more preferably 10 μm or less, and especially preferably 8 μm or less. Such thin polarizers have less thickness variation, excellent visibility, and excellent resistance to thermal shock due to minimal dimensional change.

[0075] A polarizer made by dyeing a polyvinyl alcohol-based film with iodine and then uniaxially stretching it can be produced, for example, by dyeing the polyvinyl alcohol by immersing it in an aqueous solution of iodine and then stretching it to 3 to 7 times its original length. Boric acid, zinc sulfate, zinc chloride, etc., may be included as needed, or the film may be immersed in an aqueous solution of potassium iodide, etc. Furthermore, if necessary, the polyvinyl alcohol-based film may be immersed in water and washed before dyeing. Washing the polyvinyl alcohol-based film with water removes dirt and anti-blocking agents from the film surface, and also prevents uneven dyeing by swelling the film. Stretching may be performed after dyeing with iodine, while dyeing, or after stretching. Stretching can also be performed in aqueous solutions of boric acid or potassium iodide, or even in a water bath.

[0076] It is preferable for the polarizer to contain boric acid from the viewpoint of stretch stability and humidification reliability. Furthermore, from the viewpoint of suppressing the occurrence of through cracks, the boric acid content in the polarizer is preferably 22% by mass or less, and more preferably 20% by mass or less, relative to the total amount of the polarizer. From the viewpoint of stretch stability and humidification reliability, the boric acid content relative to the total amount of the polarizer is preferably 10% by mass or more, and more preferably 12% by mass or more.

[0077] Typical examples of thin polarizers include, Patent No. 4751486 specification, Patent No. 4751481 specification, Patent No. 4815544 specification, Patent No. 5048120 specification, International Publication No. 2014 / 077599 pamphlet, International Publication No. 2014 / 077636 pamphlet, Examples include thin polarizers described in the text or thin polarizers obtained from the manufacturing methods described therein.

[0078] As for the thin polarizers, among manufacturing methods that include a step of stretching in a laminated state and a step of dyeing, those obtained by a manufacturing method that includes a step of stretching in a boric acid aqueous solution, as described in Japanese Patent No. 4751486, Japanese Patent No. 4751481, and Japanese Patent No. 4815544, are preferred because they can be stretched to a high magnification and their polarization performance can be improved. In particular, those obtained by a manufacturing method that includes a step of auxiliary air stretching before stretching in a boric acid aqueous solution, as described in Japanese Patent No. 4751481 and Japanese Patent No. 4815544, are preferred. These thin polarizers can be obtained by a manufacturing method that includes a step of stretching a polyvinyl alcohol-based resin (hereinafter also referred to as PVA-based resin) layer and a stretching resin substrate in a laminated state and a step of dyeing. With this manufacturing method, even if the PVA-based resin layer is thin, it is possible to stretch it without problems such as breakage due to stretching because it is supported by the stretching resin substrate.

[0079] As the material constituting the transparent protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, etc. is used. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose-based resin films, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic polyolefin resins (norbornene-based resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. One or more arbitrary appropriate additives may be contained in the transparent protective film. Examples of the additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, colorants, etc. The content of the thermoplastic resin in the transparent protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. When the content of the thermoplastic resin in the transparent protective film is 50% by weight or less, there is a possibility that the high transparency inherent to the thermoplastic resin cannot be sufficiently exhibited.

[0080] Also, as the material for forming the transparent protective film, those excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, etc. are preferable, and particularly, the water vapor transmission rate is 150 g / m 2 / 24 h or less is more preferable, 140 g / m 2 / 24 h or less is particularly preferable, and 120 g / m 2 / 24 h or less is even more preferable.

[0081] On the surface of the transparent protective film where the polarizer is not adhered, functional layers such as a hard coat layer, an antireflection layer, an anti-sticking layer, a diffusion layer or an antiglare layer can be provided. Note that the functional layers such as the hard coat layer, the antireflection layer, the anti-sticking layer, the diffusion layer and the antiglare layer can be provided on the transparent protective film itself, or can be provided separately as a separate body from the transparent protective film.

[0082] The thickness of the transparent protective film can be determined as appropriate, but generally it is about 1 to 500 μm, preferably 1 to 300 μm, and more preferably 5 to 200 μm, considering factors such as strength, workability, and thinness. Furthermore, 10 to 200 μm is preferred, and 20 to 80 μm is preferred.

[0083] As the transparent protective film, a phase difference layer having a front phase difference of 40 nm or more and / or a thickness direction phase difference of 80 nm or more can be used. The front phase difference is usually controlled to be in the range of 40 to 200 nm, and the thickness direction phase difference is usually controlled to be in the range of 80 to 300 nm. When a phase difference layer is used as the transparent protective film, the phase difference layer also functions as the transparent protective film, thus enabling a thinner design.

[0084] The optical laminate according to the present invention can be manufactured, for example, by the following manufacturing method. A method for manufacturing an optical laminate in which at least a first optical layer and a second optical layer are laminated with an adhesive layer in between, A coating step of applying an adhesive composition to one or both of the bonding surfaces of the first optical layer and the second optical layer, A bonding step of bonding the first optical layer and the second optical layer, The process includes an bonding step of bonding the first optical layer and the second optical layer via an adhesive layer formed by irradiating the adhesive composition with active energy rays from the first optical layer surface side or the second optical layer surface side, thereby curing at least the adhesive composition. The first optical layer is a phase difference layer of a liquid crystal system, A method for manufacturing an optical laminate, characterized in that the adhesive layer is a cured layer of an adhesive composition containing at least a cationic polymerizable component, a cationic polymerization initiator, and metal oxide particles.

[0085] In the above coating process, the method for applying the adhesive composition to one or both of the bonding surfaces of the first optical layer and the second optical layer is appropriately selected depending on the viscosity of the composition and the desired thickness. Examples include reverse coaters, gravure coaters (direct, reverse, and offset), bar reverse coaters, roll coaters, die coaters, bar coaters, and rod coaters.

[0086] The first optical layer and / or the second optical layer may undergo surface modification treatment before the coating process. In particular, when a polarizer is used as the optical film, it is preferable to surface modify the polarizer. Examples of surface modification treatments include corona treatment, plasma treatment, and Itro treatment, with corona treatment being particularly preferred. Corona treatment generates reactive functional groups such as carbonyl groups and amino groups on the polarizer surface, improving adhesion to the adhesive layer. In addition, the ashing effect removes foreign matter from the surface and reduces surface irregularities, making it possible to create an optical laminate with excellent appearance characteristics.

[0087] The first optical layer and the second optical layer are bonded together using a roll laminator or the like via the adhesive composition applied as described above (bonding process).

[0088] After bonding the first optical layer and the second optical layer, the adhesive composition is cured by irradiation with active energy rays (electron beams, ultraviolet rays, visible light, etc.) to form an adhesive layer. The irradiation direction of the active energy rays (electron beams, ultraviolet rays, visible light, etc.) can be any appropriate direction.

[0089] When irradiating with an electron beam, any suitable irradiation conditions can be adopted as long as they allow the above adhesive composition to cure. For example, the acceleration voltage for electron beam irradiation is preferably 5kV to 300kV, and more preferably 10kV to 250kV. If the acceleration voltage is less than 5kV, the electron beam may not reach the adhesive, resulting in insufficient curing. If the acceleration voltage exceeds 300kV, the penetrating force through the sample may be too strong, potentially damaging the first and second optical layers. The irradiation dose is 5 to 100kGy, more preferably 10 to 75kGy. If the irradiation dose is less than 5kGy, the adhesive will not cure sufficiently. If it exceeds 100kGy, the first and second optical layers will be damaged, resulting in a decrease in mechanical strength and yellowing, making it impossible to obtain the desired optical properties.

[0090] Electron beam irradiation is usually performed in an inert gas environment, but if necessary, it can also be performed in air or under conditions with a small amount of oxygen introduced. Depending on the materials of the first and second optical layers, by appropriately introducing oxygen, oxygen inhibition can be intentionally caused on the surfaces of the first and second optical layers that are initially hit by the electron beam, thereby preventing damage to the first and second optical layers and allowing the electron beam to be efficiently directed only at the adhesive.

[0091] When manufacturing an optical laminate according to the present invention, it is preferable to use an active energy ray that includes visible light in the wavelength range of 380 nm to 450 nm, and more preferably an active energy ray that has the highest irradiation amount of visible light in the wavelength range of 380 nm to 450 nm. When using ultraviolet light and visible light, and when using a transparent protective film with ultraviolet absorption capability (ultraviolet-opaque transparent protective film) as the optical film, it absorbs light with wavelengths shorter than approximately 380 nm, so light with wavelengths shorter than 380 nm does not reach the curable resin composition and does not contribute to its polymerization reaction. Furthermore, light with wavelengths shorter than 380 nm absorbed by the first optical layer and the second optical layer is converted into heat, causing the first optical layer or the second optical layer itself to generate heat, which can cause defects such as curling and wrinkling of the optical laminate. Therefore, when ultraviolet and visible light are used in the present invention, it is preferable to use a device that does not emit light with a wavelength shorter than 380 nm as the active energy ray generator. More specifically, it is preferable that the ratio of the integrated illuminance in the wavelength range of 380 to 440 nm to the integrated illuminance in the wavelength range of 250 to 370 nm is 100:0 to 100:50, and more preferably 100:0 to 100:40. When manufacturing the optical laminate according to the present invention, gallium-filled metal halide lamps and LED light sources that emit light in the wavelength range of 380 to 440 nm are preferred as active energy rays. Alternatively, light sources containing ultraviolet and visible light such as low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, incandescent bulbs, xenon lamps, halogen lamps, carbon arc lamps, metal halide lamps, fluorescent lamps, tungsten lamps, gallium lamps, excimer lasers, or sunlight can be used, and ultraviolet light with a wavelength shorter than 380 nm can also be blocked using a bandpass filter. To improve the adhesion performance of the adhesive layer between the first and second optical layers while preventing curling of the optical laminate, it is preferable to use a gallium-filled metal halide lamp and active energy rays obtained through a bandpass filter capable of blocking light with wavelengths shorter than 380 nm, or to use active energy rays with a wavelength of 405 nm obtained using an LED light source.

[0092] When manufacturing the optical laminate according to the present invention on a continuous line, the line speed depends on the curing time of the adhesive composition, but is preferably 1 to 500 m / min, more preferably 5 to 300 m / min, and even more preferably 10 to 100 m / min. If the line speed is too low, productivity will be poor, or the damage to the first and second optical layers will be too great, making it impossible to produce an optical laminate that can withstand durability tests. If the line speed is too high, the curing of the adhesive composition will be insufficient, and the desired adhesion may not be obtained.

[0093] The optical laminate according to the present invention may also be provided with an adhesive layer for bonding to other components such as liquid crystal cells. The adhesive used to form the adhesive layer is not particularly limited, but for example, an adhesive based on polymers such as acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyethers, fluorine-based or rubber-based polymers can be appropriately selected and used. In particular, adhesives that have excellent optical transparency, exhibit appropriate wettability, cohesiveness and adhesive properties, and have excellent weather resistance and heat resistance, such as acrylic adhesives, are preferably used.

[0094] The adhesive layer can be provided on one or both sides of the optical laminate according to the present invention as a superimposed layer of different compositions or types. Furthermore, when provided on both sides, the adhesive layers on the front and back of the optical laminate according to the present invention may have different compositions, types, or thicknesses. The thickness of the adhesive layer can be appropriately determined according to the intended use and adhesive strength, and is generally 1 to 500 μm, preferably 1 to 200 μm, and particularly preferably 1 to 100 μm.

[0095] For the exposed surface of the adhesive layer, a separator is temporarily attached and covered to prevent contamination until it is put into practical use. This prevents contact with the adhesive layer under normal handling conditions. As for the separator, apart from the thickness conditions mentioned above, suitable thin materials such as plastic film, rubber sheet, paper, cloth, nonwoven fabric, net, foam sheet, metal foil, or laminates thereof can be used, and may be coated with a suitable release agent such as silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide as needed, in accordance with conventional methods.

[0096] The optical laminate according to the present invention can be preferably used in the formation of various devices such as liquid crystal display devices. The formation of liquid crystal display devices can be carried out in accordance with conventional methods. That is, liquid crystal display devices are generally formed by appropriately assembling components such as liquid crystal cells, polarizing films or optical laminates, and, if necessary, lighting systems, and incorporating drive circuits. However, in the present invention, there are no particular limitations except for the use of the polarizing film or optical laminate according to the present invention, and the formation can be carried out in accordance with conventional methods. Any type of liquid crystal cell can be used, such as TN type, STN type, or π type.

[0097] Appropriate liquid crystal display devices can be formed, such as liquid crystal display devices in which optical laminates are arranged on one or both sides of a liquid crystal cell, or in which a backlight or reflector is used in the illumination system. In this case, the optical laminate according to the present invention can be installed on one or both sides of the liquid crystal cell. When optical laminates are provided on both sides, they may be the same or different. Furthermore, when forming a liquid crystal display device, appropriate components such as diffusers, anti-glare layers, anti-reflective films, protective plates, prism arrays, lens array sheets, light diffusers, and backlights can be arranged in appropriate positions in one or more layers. [Examples]

[0098] The following describes some embodiments of the present invention, but the embodiments of the present invention are not limited to these.

[0099] (Adjustment of adhesive composition) According to the formulation table in Table 1, the following components were mixed and stirred at 25°C for 1 hour to obtain the adhesive compositions used in Examples 1-8 and Comparative Examples 1-4. The values ​​in the table represent weight percentages when the total amount of the composition is considered to be 100% by mass.

[0100] The materials that make up the adhesive composition are shown below. (i) Cationic polymerizable components • Alicyclic epoxy compound (3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate): Trade name "CEL-2021P", manufactured by Daicel Corporation • Bifunctional oxetane compound (3-ethyl-3-(phenoxymethyl)oxetane): Trade name "OXT-221", manufactured by Toagosei Co., Ltd. • Aliphatic epoxy compound (1,6-hexanediol diglycidyl ether): Trade name "EX-212L", manufactured by Nagase ChemteX Corporation • Aromatic epoxy compound (1) (Bisphenol A type epoxy resin): Trade name "jER828", manufactured by Mitsubishi Chemical Corporation • Aromatic epoxy compound (2) (biphenyl epoxy resin): Trade name "EX-142-IM", manufactured by Nagase ChemteX Corporation • Aromatic oxetane compound (xylylene bisoxetane): Product name "OXT-121", manufactured by Toagosei Co., Ltd. • Aromatic epoxy compound (3) (p-tert-butylphenylglycidyl ether): Trade name "EX-146", manufactured by Nagase ChemteX Corporation (ii) radical polymerizable compounds • Aromatic acrylate (phenoxybenzyl acrylate): Product name "Light Acrylate POB-A", manufactured by Kyoeisha Chemical Co., Ltd. • Hydroxyl group-containing (meth)acrylate (4-hydroxybutyl acrylate): Product name "4HBA", manufactured by Mitsubishi Chemical Corporation. • Aliphatic difunctional acrylate (1,9-nonanediol diacrylate): Product name "Light Acrylate 1.9ND-A", manufactured by Kyoeisha Chemical Co., Ltd. • Acryloylmorpholin: Brand name "ACMO", manufactured by KJ Chemicals. • Bifunctional acrylate (tripropylene glycol diacrylate): Product name "Arronix M-220", manufactured by Toagosei Co., Ltd. (iii) Metal oxide particles • Zirconia dispersion 1: Phenoxybenzyl acrylate dispersion of zirconium oxide with an average particle size of 20 nm (particle concentration 50% by weight) • Zirconia dispersion 2: Phenylglycidyl ether dispersion of zirconium oxide with an average particle size of 20 nm (particle concentration 30.3% by weight) (iv) Other combination agents • Photoradical initiator (1-hydroxycyclohexylphenyl ketone): Trade name "Omnirad 184", manufactured by IGM Resins BV. • Photoacid generator (75% solution of Iodonium, (4-methylphenyl)[4-(2-methylpropyl)phenyl]-, hexafluorophosphate(1-) in propylene carbonate): Trade name "Omnicat 250", manufactured by IGM Resins BV. • Photosensitizer (diethylthioxanthone): Product name "KAYACURE DETX-S", manufactured by Nippon Kayaku Co., Ltd. The zirconia dispersions 1 and 2 described above were manufactured by the following method.

[0101] (Synthesis of dispersant A) 415 g (1 mol) of tristyrenated phenol and 1 g (0.018 mol) of potassium hydroxide were charged into an autoclave and mixed uniformly. Under conditions of 130°C, 352 g (8 mol) of ethylene oxide (EO) was added dropwise to the reaction system. After the addition of ethylene oxide was complete, the system was aged for 1 hour at 130°C while maintaining a pressure of 0.1 MPa to obtain an 8 mol EO adduct of tristyrenated phenol.

[0102] 767 g (1 mole) of the above tristyrenated phenol EO 8 molar adduct and 152 g (1.3 moles) of sodium monochloroacetate were placed in a reactor and stirred until homogenized. Next, 52 g of sodium hydroxide was added under conditions of the reaction system being 60°C, and the temperature was raised to 80°C and aged for 3 hours. After aging, it was cooled to 50°C, and 117 g (1.2 moles) of 98% sulfuric acid was added dropwise at the same temperature to obtain a white suspension. This white suspension was washed with distilled water, and the solvent was removed by vacuum distillation to obtain dispersant A.

[0103] (Preparation of Zirconia Dispersion 1) To 100 parts of a methyl ethyl ketone dispersion of zirconium oxide (manufactured by Nissan Chemical Industries, grade name "OZ-S40K-AC", average particle size (D50) based on dynamic light scattering method: 20 nm, zirconium oxide solid content concentration: 30%), 1.5 parts of dispersant A and 28.5 parts of m-phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical, trade name "Light Acrylate POB-A"; hereinafter referred to as "POB-A") were added and mixed. Then, the solvent was removed under reduced pressure using a rotary evaporator to obtain zirconia dispersion 1, which is a monomer dispersion of zirconium oxide. This zirconia dispersion 1 contains zirconium oxide / dispersant A / POB-A in a weight ratio of 50 / 2.5 / 47.5.

[0104] (Preparation of Zirconia Dispersion 2) To 100 parts of a methyl ethyl ketone dispersion of zirconium oxide (manufactured by Nissan Chemical Industries, grade name "OZ-S40K-AC", average particle size (D50) based on dynamic light scattering method: 20 nm, zirconium oxide solid content concentration: 30%), 1.5 parts of dispersant A and 67.5 parts of phenyl glycidyl ether (manufactured by Nagase ChemteX, trade name "EX-142-IM") were added and mixed. Then, the solvent was removed under reduced pressure using a rotary evaporator to obtain zirconia dispersion 2, which is a monomer dispersion of zirconium oxide. This zirconia dispersion 2 contains zirconium oxide / dispersant A / EX-142-IM in a weight ratio of 30.3 / 1.5 / 68.2.

[0105] The materials that make up the optical laminate are shown below.

[0106] <Manufacturing of polarizers> A laminate was formed by air-assisted stretching at a stretching temperature of 130°C from an amorphous PET substrate with a 9 μm thick PVA layer. Next, a colored laminate was formed by dyeing the stretched laminate. Furthermore, an optical film laminate containing a 5 μm thick PVA layer was formed by stretching the colored laminate in boric acid water at a stretching temperature of 65°C, integrally with the amorphous PET substrate, to achieve a total stretching ratio of 5.94 times. This two-stage stretching process resulted in an optical film laminate containing a 5 μm thick PVA layer, in which the PVA molecules in the PVA layer formed on the amorphous PET substrate were highly oriented, and the iodine adsorbed by dyeing formed a polyiodide ion complex highly oriented in one direction, constituting a thin polarizer.

[0107] <Transparent protective film> "TAC"; Triacetylcellulose (TAC) film (product name "TJ25UL", thickness 25μm, manufactured by Fujifilm Corporation)

[0108] <Photopolymerizable liquid crystal composition> A photopolymerizable liquid crystal compound exhibiting a nematic liquid crystal phase (BASF's "Paliocolor LC242") was dissolved in cyclopentanone to prepare a solution with a solid content of 30% by weight. A surfactant (Bic Chemie's "BYK-360") and a photopolymerization initiator (IGM Resins' "Omnirad907") were added to this solution to prepare a liquid crystal composition solution. The amounts of the leveling agent and polymerization initiator added were 0.01 parts by weight and 3 parts by weight, respectively, per 100 parts by weight of the photopolymerizable liquid crystal compound.

[0109] <λ / 2 retardation layer> Using a biaxially oriented norbornene-based film (Zeonor Film, manufactured by Zeon Corporation, thickness: 33 μm, frontal retardation: 135 nm) as a substrate, the above liquid crystal composition was coated onto the substrate by a bar coater so that the phase difference was λ / 2, and the liquid crystal was oriented by heating at 100°C for 3 minutes. After cooling to room temperature, the film was subjected to a nitrogen atmosphere with an integrated light intensity of 400 mJ / cm².2 A laminate was obtained in which a homogeneous oriented liquid crystal layer was provided by photocuring using ultraviolet light.

[0110] <λ / 4 retardation layer> Using a biaxially oriented norbornene-based film (Zeonor Film, manufactured by Nippon Zeon Co., Ltd., thickness: 33 μm, frontal retardation: 135 nm) as a substrate, the above liquid crystal composition was applied to the substrate by a bar coater so that the phase difference was λ / 4, and the liquid crystal was oriented by heating at 100°C for 3 minutes. After cooling to room temperature, the film was subjected to a nitrogen atmosphere with an integrated light intensity of 400 mJ / cm². 2 A laminate was obtained in which a homogeneous oriented liquid crystal layer was provided by photocuring using ultraviolet light.

[0111] <Adhesive layer> A monomer mixture containing 99 parts by weight of butyl acrylate (BA) and 1 part by weight of 4-hydroxybutyl acrylate (HBA) was charged into a four-necked flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser. Furthermore, 0.1 parts by weight of 2,2'-azobisisobutyronitrile was added to 100 parts by weight of the monomer mixture (solids) along with ethyl acetate as a polymerization initiator. After introducing nitrogen gas and purging the flask with nitrogen while gently stirring, the polymerization reaction was carried out for 7 hours while maintaining the liquid temperature in the flask at around 55°C. Subsequently, ethyl acetate was added to the resulting reaction solution to prepare a solution of (meth)acrylic polymer A1 with a weight-average molecular weight of 1.6 million, with a solids content concentration of 30%. An acrylic adhesive composition was prepared by blending 0.1 parts by weight of an isocyanate crosslinking agent (product name: Takenate D110N, trimethylolpropane xylylene diisocyanate, manufactured by Mitsui Chemicals, Inc.), 0.3 parts by weight of a peroxide crosslinking agent, benzoyl peroxide (product name: Naiper BMT, manufactured by Nippon Oil & Fats Co., Ltd.), and 0.08 parts by weight of a silane coupling agent (product name: KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.) with 100 parts by weight of the solid content of the obtained (meth)acrylic polymer A1 solution. The acrylic adhesive composition was uniformly coated onto the surface of a 38 μm thick polyethylene terephthalate film (release liner) treated with a silicone release agent using a fountain coater, and dried in an air-circulating constant temperature oven at 155°C for 2 minutes to form an adhesive layer 1 with a thickness of 7 μm on the surface of the substrate.

[0112] <Polarizing film (1)> Using an MCD coater (manufactured by Fuji Machinery Co., Ltd.) (cell shape: honeycomb, gravure roll line count: 700 lines / inch, aperture ratio of cells formed on the gravure roll: 40%, rotation speed 140% / line speed), corona treatment was performed on the surface of the PVA layer of the polarizer described above at a processing density of 50 W·min / m2 using a corona treatment machine. The adhesive composition for laminated optical films according to Comparative Example 3 was then coated onto the corona-treated surface (coating thickness 1.05 μm), and the same corona treatment machine was used at a processing density of 50 W·min / m2. 2The corona-treated surface of the TAC film was bonded to the film using a roll machine (bonding line speed: 15 m / min). The coating thickness was measured using a spectroscopic interferometry film thickness meter (Ocean Optics: spectrometer "USB2000+", light source "HL-2000", fiber "OCF-103995"). Subsequently, a visible light irradiation device (Heraus Light HAMMER10 Mark III, bulb: V-bulb, peak illuminance: 1600 mW / cm²) was used on the TAC film side. 2 Total irradiation dose 1000 / mJ / cm 2 The irradiance and cumulative irradiation dose of the active energy rays were measured using a Power Puck 2 (manufactured by EIT, UVV measurement). By curing the adhesive composition for laminated optical films by irradiating it with active energy rays, a polarizing film (1) was produced in which an amorphous PET substrate, a polarizer, and a TAC film were laminated via the cured layer of the adhesive composition for laminated optical films. The thickness of the cured layer of the adhesive composition for laminated optical films was 1 μm.

[0113] <Polarizing film (2)> Next, the amorphous PET substrate of the polarizing film (1) is peeled off, and the polarizer surface of the peeled surface is treated with a corona treatment machine at a density of 50 W·min / m². 2 Corona treatment was performed. A release liner with adhesive layer 1 formed on it using a roll machine was transferred to the corona-treated polarizer surface to create an adhesive-layered optical laminate (1). A treatment density of 50 W·min / m was used with the same corona treatment machine. 2 The homogeneous oriented liquid crystal layer surface of the corona-treated λ / 2 phase difference film and the release liner of the adhesive-coated optical laminate (1) were separated, and the λ / 2 phase difference film was bonded to the adhesive layer of the separated surface using a roll machine so that the lagging axis of the λ / 2 phase difference film was at a 15° angle with the transmission axis of the polarizer, thereby producing a polarizing film (2) in which the λ / 2 phase difference film, polarizer, and TAC film were laminated. The bonding line speed was 15 m / min.

[0114] (Examples of optical laminate manufacturing) The biaxially oriented norbornene-based film of the polarizing film (2) is peeled off, and the λ / 2 phase difference film surface of the peeled surface is treated with a corona treatment machine at a treatment density of 50 W·min / m². 2 Corona treatment was performed. An MCD coater (manufactured by Fuji Machinery Co., Ltd.) (cell shape: honeycomb, gravure roll line count: as described in Table 1, aperture ratio of cells formed on the gravure roll: 40%, rotation speed 140% / line speed) was used as the gravure coater to coat the corona-treated λ / 2 phase difference film surface with the adhesive compositions for laminated optical films according to Examples 1-8 and Comparative Examples 1-3, which have the formulations described in Table 1. The homogeneous oriented liquid crystal layer surface of the λ / 4 phase difference film, which had been corona-treated at a processing density of 50 W·min / m2 using the same corona treatment machine, was bonded to the λ / 2 phase difference film surface using a roll machine so that the slow layer axis of the λ / 4 phase difference film was at a 75° angle with the transmission axis of the polarizer ((bonding process) line speed was 15 m / min). The coating thickness was measured using a spectroscopic interferometric film thickness meter (Ocean Optics: spectrometer "USB2000+", light source "HL-2000", fiber "OCF-103995"). Subsequently, a visible light irradiation device (Heraus Light HAMMER10 Mark III, bulb: V-bulb, peak illuminance: 1600 mW / cm²) was used from the λ / 4 phase difference film side. 2 Total irradiation dose 1000 / mJ / cm 2 The illuminance and cumulative irradiation dose of the active energy rays were measured by irradiating the adhesive compositions described in Examples 1-8 and Comparative Examples 1-4 with active energy rays using a Power Puck 2 (manufactured by EIT, UVV measurement). By curing the adhesive compositions described in Examples 1-8 and Comparative Examples 1-4, optical laminates of Examples 1-8 and Comparative Examples 1-4 were produced, in which a λ / 4 phase difference film surface, a λ / 2 phase difference film, a polarizer, and a TAC film were laminated via the cured layer of the adhesive composition.

[0115] Details of each evaluation method are as follows:

[0116] <Liquid viscosity of adhesive composition> The viscosity of the adhesive compositions used in Examples 1-8 and Comparative Examples 1-4 was measured using a TVE22LT E-type viscometer manufactured by Toki Sangyo Co., Ltd.

[0117] <Measuring the refractive index of the adhesive layer (cured layer)> The adhesive compositions used in Examples 1-8 and Comparative Examples 1-4 were coated (100 μm thick) onto cycloolefin polymer films (COP films). The same COP films were then bonded to the coated surfaces, and the films were irradiated with the above-mentioned visible light using an active energy ray irradiation device to obtain cured layers (single films) of the adhesive compositions used in Examples 1-8 and Comparative Examples 1-4. The refractive index in the plane and the refractive index in the thickness direction of the obtained cured layers were measured using a prism coupler SPA-4000 (manufactured by Cylon Technology), and the average values ​​of these measurements were taken as the average refractive index of the adhesive layer. The measurement temperature was 23°C, and the measurement wavelength was 594 nm.

[0118] <Curing shrinkage rate of adhesive composition> The curing shrinkage rate was measured using a CUSTRON EU201C resin curing shrinkage measuring device (manufactured by Acroedge Co., Ltd.) with a laser displacement meter, and the curing shrinkage rate was calculated according to the method described in Japanese Patent Application Publication No. 2013-104869.

[0119] <Surface roughness of the surface of the first optical layer (the surface opposite to the adhesive layer side)> The laminated optical film was cut into 10cm x 5cm pieces, and the biaxially oriented norbornene-based film attached to the λ / 4 phase difference film of the laminated optical film was peeled off. The surface from which the biaxially oriented norbornene-based film was peeled off (λ / 4 phase difference film surface) was scanned perpendicular to the film transport direction during adhesive coating on the λ / 2 phase difference film surface during the manufacturing of the laminated optical film, and the surface irregularities of the λ / 4 phase difference film were measured using line measurement. Specifically, as shown in Figure 2, the magnitude of the undulation was measured relative to the average line B obtained from line measurement of the surface irregularities of the surface opposite to the adhesive layer side of the first optical layer 1 (λ / 4 phase difference film surface), and was expressed as the sum of the height D1 at the apex of the highest convex part and the depth D2 of the lower of the two recesses adjacent to the highest convex part (D1 + D2). The surface irregularities were measured under the following conditions. Measuring device: VertScan (registered trademark) (manufactured by Ryoka Systems Co., Ltd., model R5500G)

[0120] <Interference unevenness in optical laminates including polarizing film> The polarizing plate composites of the examples and comparative examples were attached to an aluminum reflector via an acrylic adhesive (film thickness 25 μm), visually observed under a three-wavelength fluorescent lamp, and evaluated based on the following criteria. The evaluation results are shown in Table 3. ◎: No interference unevenness is visible. ○: Slight interference unevenness is visible, but acceptable. ×: Strong interference unevenness is visible.

[0121] [Table 1]

[0122] From the results in Table 1, it can be seen that in the optical laminates of Comparative Examples 1 to 4, the surface irregularities (relief size) of the surface opposite to the adhesive layer side of the first optical layer are large enough to exceed 100 nm, resulting in a deterioration of interference uniformity in the optical laminate. On the other hand, in the optical laminates of Examples 1 to 8, the surface irregularities (relief size) of the surface opposite to the adhesive layer side of the first optical layer are kept below 100 nm, thus sufficiently suppressing interference uniformity in the optical laminate. [Explanation of Symbols]

[0123] 1 First optical layer, 2 Second optical layer, 3 Adhesive layer, 4 Transparent protective film, 5 Polarizer, 6 Adhesive layer, 7 Organic light-emitting diode layer, 10 Optical laminate, B Average line obtained from line measurement of the surface irregularities of the surface opposite to the adhesive layer side of the first optical layer 1, D1 Height at the apex of the highest convex part, D2 Depth of the lower of the two recesses adjacent to each of the highest convex parts

Claims

1. An optical laminate in which at least a first optical layer and a second optical layer are laminated with an adhesive layer in between, The first optical layer is a phase difference layer of a liquid crystal system, The adhesive layer is a cured layer of an adhesive composition containing at least a cationic polymerizable component, a cationic polymerization initiator, and metal oxide particles. An optical laminate characterized in that the surface of the first optical layer opposite to the adhesive layer side has the following surface irregularities. (Surface unevenness) With respect to the average line obtained by line measurement of the surface irregularities of the surface of the first optical layer opposite to the surface facing the adhesive layer, the magnitude of the undulation, expressed as the sum of the height D1 at the apex of the highest convex part and the depth D2 of the lower of the two recesses adjacent to the highest convex part (D1 + D2), is 100 nm or less.

2. The optical laminate according to claim 1, wherein the adhesive composition further contains a radical polymerizable compound.

3. The optical laminate according to claim 1, wherein the refractive index of the adhesive layer is 1.54 or higher.

4. The optical laminate according to claim 1, wherein the adhesive composition contains 5 to 50% by mass of the metal oxide particles when the total amount in the composition is 100% by mass.

5. The optical laminate according to claim 1, wherein the adhesive composition further contains a (meth)acrylate containing an aromatic ring skeleton.

6. The optical laminate according to claim 5, wherein the (meth)acrylate containing the aromatic ring skeleton contains at least one selected from the group consisting of (meth)acrylates having a polycyclic aromatic ring skeleton and (meth)acrylates having two or more aromatic rings.

7. The optical laminate according to claim 5, wherein the (meth)acrylate containing the aromatic ring skeleton is phenoxybenzyl (meth)acrylate.

8. The optical laminate according to claim 1, wherein the adhesive composition contains at least one selected from the group consisting of alicyclic epoxy compounds, aromatic epoxy compounds, aromatic oxetane compounds, and bifunctional oxetane compounds as the cationic polymerizable component.

9. The optical laminate according to claim 1, wherein the adhesive composition contains at least one selected from the group consisting of zinc oxide, zirconium oxide, and titanium oxide as the metal oxide particles.

10. The optical laminate according to claim 1, wherein the average particle diameter of the metal oxide particles is 100 nm or less.

11. The optical laminate according to claim 1, wherein the thickness of the adhesive layer is 0.3 to 3.0 μm.

12. A method for manufacturing an optical laminate in which at least a first optical layer and a second optical layer are laminated with an adhesive layer in between, A coating step of applying an adhesive composition to one or both of the bonding surfaces of the first optical layer and the second optical layer, A bonding step of bonding the first optical layer and the second optical layer, The process includes an bonding step of bonding the first optical layer and the second optical layer via an adhesive layer formed by irradiating the adhesive composition with active energy rays from the first optical layer surface side or the second optical layer surface side, thereby curing at least the adhesive composition. The first optical layer is a phase difference layer of a liquid crystal system, A method for manufacturing an optical laminate, characterized in that the adhesive layer is a cured layer of an adhesive composition containing at least a cationic polymerizable component, a cationic polymerization initiator, and metal oxide particles.

13. The method for producing an optical laminate according to claim 12, wherein the viscosity of the adhesive composition at 25°C is 100 [mPa·s] or less.

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