Adhesive, optical laminate, and image display device

Abstract

Provided is an adhesive which can be used for attaching optical films, and which exhibits excellent adhesiveness when attached to optical films. Provided is an optical laminate in which optical films are bonded together using an adhesive layer formed from such an adhesive. Provided is an image display device including such an optical laminate.　This adhesive can be used to attach optical films, and is a solution containing an amino compound (A) and a solvent (C). The content ratio of the amino compound (A) relative to the total amount of the amino compound (A) and the solvent (C) is at least 0.01 wt% but less than 10 wt%. The solvent (C) includes at least one selected from the group consisting of water and alcohols having two or fewer carbon atoms.

Description

Adhesive, optical laminate, and image display device

[0001] The present invention relates to an adhesive, an optical laminate, and an image display device.

[0002] Image display devices such as liquid crystal display devices and organic EL display devices typically include an optical laminate including a plurality of light-transmitting optical films. In such optical laminates, a pressure-sensitive adhesive is used to bond the plurality of light-transmitting optical films together.

[0003] When a conventional adhesive is used to bond a light-transmitting optical film, there is a problem that the adhesive may not exhibit sufficient adhesion between the light-transmitting optical film and the adhesive.

[0004] Recently, a molecular adhesive technique for bonding by chemical bonding has been reported as a pressure-sensitive adhesive used in optical laminates (Patent Document 1).

[0005] International Publication No. 2022 / 172755

[0006] The object of the present invention is to provide an adhesive used for bonding an optical film, which adhesive has excellent adhesion when bonded to the optical film, to provide an optical laminate in which an optical film is bonded with an adhesive layer formed from such an adhesive, and to provide an image display device including such an optical laminate.

[0007] [1] An adhesive according to an embodiment of the present invention is an adhesive used for bonding optical films, the adhesive being a solution containing an amino compound (A) and a solvent, wherein the content of the amino compound (A) relative to the total of the amino compound (A) and the solvent (C) is 0.01 wt % or more but less than 10 wt %, and the solvent (C) contains at least one selected from the group consisting of water and alcohols having 2 or less carbon atoms. [2] In the adhesive described in [1] above, the content of the solvent (C) in the solution may be 80 wt % to 99.9 wt %. [3] In the adhesive described in [1] or [2] above, the content of the at least one selected from the group consisting of water and alcohols having 2 or less carbon atoms in the solvent (C) may be 50 wt % to 100 wt %. [4] In the adhesive described in any one of [1] to [3] above, the amino compound (A) may be an amino-silane coupling agent. [5] In the adhesive described in any one of [1] to [4] above, the adhesive may contain an epoxy compound (B). [6] In the adhesive according to the above [5], the total content of the amino compound (A) and the epoxy compound (B) relative to the total of the amino compound (A), the epoxy compound (B), and the solvent (C) may be more than 0.01 wt % and less than 20 wt %. [7] In the adhesive according to the above [5] or [6], the content ratio of the amino compound (A) to the epoxy compound (B) may be 6:94 to 90:10 in terms of molar ratio. [8] An optical laminate according to an embodiment of the present invention comprises a first light-transmitting optical film and a second light-transmitting optical film bonded together with an adhesive layer formed from the adhesive according to any one of the above [1] to [7]. [9] In the optical laminate according to the above [8], the adhesive layer may have a thickness of 50 nm or less.

[10] In the optical laminate according to the above [9], the adhesive layer may have a thickness of less than 30 nm.

[11] In the optical laminate according to any one of the above items [8] to

[10] , the difference in in-plane refractive index between the first light-transmitting optical film and the adhesive layer may be 0.05 or more.

[12] In the optical laminate according to any one of [8] to

[11] above, the first light-transmitting optical film may have an in-plane refractive index of 1.50 or more.

[13] In the optical laminate according to any one of [8] to

[12] above, the difference in in-plane refractive index between the second light-transmitting optical film and the adhesive layer may be 0.05 or more.

[14] In the optical laminate according to any one of [8] to

[13] above, the second light-transmitting optical film may have an in-plane refractive index of 1.50 or more.

[15] In the optical laminate according to any one of [8] to

[14] above, at least one of the first light-transmitting optical film and the second light-transmitting optical film may be a retardation film.

[16] In the optical laminate according to any one of [8] to

[15] above, the adhesive layer may contain an organosilicon compound.

[17] An optical laminate according to an embodiment of the present invention includes the optical laminate according to any one of [8] to

[16] above.

[0008] According to an embodiment of the present invention, it is possible to provide an adhesive used for bonding an optical film, which adhesive has excellent adhesion when bonded to the optical film. According to an embodiment of the present invention, it is also possible to provide an optical laminate in which an optical film is bonded with an adhesive layer formed from such an adhesive. According to an embodiment of the present invention, it is also possible to provide an image display device including such an optical laminate.

[0009] 1 is a schematic cross-sectional view of an embodiment of an optical laminate of the present invention, and FIG. 2 is a schematic cross-sectional view of an embodiment of an optical member including an optical laminate according to an embodiment of the present invention.

[0010] When the expression "weight" appears in this specification, it may be read as "mass," which is commonly used as an SI unit indicating weight.

[0011] The definitions of terms and symbols used in this specification are as follows. (1) Refractive Index (nx, ny, nz) "nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the in-plane direction perpendicular to the slow axis (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction. Note that, when the expression "in-plane refractive index" appears in this specification, it refers to "nx". (2) In-Plane Retardation (Re) "Re(λ)" is the in-plane retardation of a film measured at 23°C with light having a wavelength of λ nm. For example, "Re(550)" is the in-plane retardation of a film measured at 23°C with light having a wavelength of 550 nm. Re(λ) is calculated by the formula: Re = (nx - ny) × d, where d (nm) is the thickness of the film. (3) Thickness Direction Retardation (Rth) "Rth(λ)" is the thickness direction retardation of a film measured with light having a wavelength of λ nm at 23°C. For example, "Rth(550)" is the thickness direction retardation of a film measured with light having a wavelength of 550 nm at 23°C. Rth(λ) is calculated by the formula: Rth = (nx - nz) x d, where d (nm) is the thickness of the film.

[0012] <1. Adhesive> The adhesive according to an embodiment of the present invention is an adhesive used for bonding optical films. Any appropriate mode can be adopted as the mode of bonding optical films using the adhesive according to an embodiment of the present invention. Such a mode includes, for example, a mode in which two optical films are bonded together using the adhesive according to an embodiment of the present invention, and a representative mode is a mode in which a first light-transmitting optical film and a second light-transmitting optical film are bonded together using an adhesive layer formed from the adhesive according to an embodiment of the present invention.

[0013] An adhesive according to an embodiment of the present invention is a solution containing an amino compound (A) and a solvent. In the adhesive according to an embodiment of the present invention, the content of the amino compound (A) is typically within a specific range, and a specific solvent is further employed. By adopting such an embodiment, the adhesive of the present invention can exhibit excellent adhesion when attached to an optical film.

[0014] In the adhesive according to an embodiment of the present invention, the content of the amino compound (A) relative to the total of the amino compound (A) and the solvent (C) is typically 0.01% by weight or more and less than 10% by weight, and may be 0.05% by weight to 5% by weight, 0.08% by weight to 4% by weight, 0.10% by weight to 3% by weight, 0.15% by weight to 2% by weight, 0.20% by weight to 1.5% by weight, or 0.20% by weight or more and less than 1.5% by weight. By adjusting the content of the amino compound (A) relative to the total of the amino compound (A) and the solvent (C) within the above range, the effects of the present invention can be more effectively exhibited.

[0015] The content of the solvent in the solution containing the amino compound (A) and the solvent (i.e., the adhesive according to an embodiment of the present invention) is preferably 80 wt % to 99.99 wt %, alternatively 85 wt % to 99.95 wt %, 85 wt % to 99.9 wt %, 90 wt % to 99.8 wt %, 92 wt % to 99.8 wt %, or 94 wt % to 99.8 wt %.

[0016] The solvent typically contains at least one selected from the group consisting of water and an alcohol having 2 or less carbon atoms. That is, the solvent may contain water but not an alcohol having 2 or less carbon atoms, may contain no alcohol having 2 or less carbon atoms, or may contain both water and an alcohol having 2 or less carbon atoms. Specific examples of alcohols having 2 or less carbon atoms include methanol, ethanol, and ethylene glycol. The effects of the present invention can be more effectively achieved when the solvent contains at least one selected from the group consisting of water and an alcohol having 2 or less carbon atoms. Furthermore, when the adhesive contains at least one solvent selected from the group consisting of water and an alcohol having 2 or less carbon atoms, the solvent easily evaporates when applied and dried, making it easier to achieve a thinner pressure-sensitive adhesive layer. Furthermore, water and an alcohol having 2 or less carbon atoms cause less damage to a polarizer and a translucent optical film, and are therefore effective in preventing deterioration in product quality, for example, when an optical laminate including an adhesive layer formed from the adhesive according to an embodiment of the present invention is combined with an optical component including a polarizer.

[0017] When the solvent contains both water and an alcohol having 2 or less carbon atoms, any appropriate content ratio between water and the alcohol having 2 or less carbon atoms can be adopted as long as the effects of the present invention are not impaired. Such a content ratio (water:alcohol having 2 or less carbon atoms) is, for example, 0.0001:99.9999 to 99.9999:0.0001 by weight.

[0018] The total content of water and the alcohol having 2 or less carbon atoms in the solvent can be any appropriate content ratio as long as it does not impair the effects of the present invention. In terms of further exhibiting the effects of the present invention, such a content ratio is preferably 50% by weight to 100% by weight, may be 60% by weight to 100% by weight, may be 70% by weight to 100% by weight, may be 80% by weight to 100% by weight, may be 90% by weight to 100% by weight, may be 95% by weight to 100% by weight, may be 98% by weight to 100% by weight, may be 99% by weight to 100% by weight, or may be substantially 100% by weight. Note that "substantially 100% by weight" means ignoring the presence of trace amounts (e.g., less than 1% by weight) of impurities and additives that may be contained in, for example, commercially available water or alcohol having 2 or less carbon atoms.

[0019] The solvent may contain at least one solvent selected from the group consisting of water and alcohols having 2 or less carbon atoms, as long as the effects of the present invention are not impaired. Examples of such other solvents include organic solvents other than alcohols having 2 or less carbon atoms. Examples of organic solvents other than alcohols having 2 or less carbon atoms include esters such as ethyl acetate, butyl acetate, and 2-hydroxyethyl acetate; ketones such as methyl ethyl ketone, acetone, cyclohexanone, methyl isobutyl ketone, diethyl ketone, methyl-n-propyl ketone, and acetylacetone; cyclic ethers such as tetrahydrofuran (THF) and dioxane; aliphatic or alicyclic hydrocarbons such as n-hexane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; alcohols having 3 or more carbon atoms such as n-propanol, isopropanol, and cyclohexanol; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and diethylene glycol monoethyl ether; and glycol ether acetates such as diethylene glycol monomethyl ether acetate and diethylene glycol monoethyl ether acetate.

[0020] The content ratio of the other solvent in the solvent is preferably 0% by weight to 50% by weight, may be 0% by weight to 40% by weight, may be 0% by weight to 30% by weight, may be 0% by weight to 20% by weight, may be 0% by weight to 10% by weight, may be 0% by weight to 5% by weight, may be 0% by weight to 2% by weight, may be 0% by weight to 1% by weight, or may be 0% by weight, in terms of being able to further exhibit the effects of the present invention.

[0021] The adhesive layer formed from the adhesive, which is a solution containing the amino compound (A) and a solvent, preferably contains an organosilicon compound.

[0022] As the amino compound (A), any appropriate amino compound can be adopted as long as it does not impair the effects of the present invention. The amino compound (A) may be one type only or two or more types. Examples of such amino compounds (A) include amino-based silane coupling agents. As the amino compound (A), for example, it is preferable that it contains a primary amino group.

[0023] As the amino silane coupling agent, any suitable amino silane coupling agent can be used as long as it is an organosilicon compound having an amino group, so long as it does not impair the effects of the present invention. Examples of such amino silane coupling agents include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldiethoxysilane, N-2-(aminoethyl)-3-aminopropyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyldiethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and hydrochlorides thereof. Commercially available amino silane coupling agents include, for example, KBM-602, KBM-603, KBM-903, KBE-603, KBE-903, and X-12-972F (all manufactured by Shin-Etsu Chemical Co., Ltd.), Z-6011, Z-6020, Z-6026, Z-6032, Z-6094, and Z-6610 (all manufactured by Dow Corning Toray Co., Ltd.), and A-1100, A-1110, A-1120, A-2120, and Y-9669 (all manufactured by Momentive Performance Materials).

[0024] As the amino compound (A), in addition to an amino-based silane coupling agent, a compound having an amino group at a terminal is preferred, such as polyethyleneimine, polyetheramine, etc. Commercially available polyethyleneimine products include SP-200, P-1000, and SP-006 (all manufactured by Nippon Shokubai Co., Ltd.), and commercially available polyetheramine products include PEA D230, PEA D400, and PEA D2000 (all manufactured by Mitsui Fine Chemicals, Inc.).

[0025] The adhesive according to an embodiment of the present invention may contain an epoxy compound (B). Any appropriate epoxy compound may be used as the epoxy compound (B) as long as the effects of the present invention are not impaired. The epoxy compound (B) may be one type or two or more types. Examples of such epoxy compounds (B) include epoxy-based silane coupling agents.

[0026] As the epoxy-based silane coupling agent, any appropriate epoxy-based silane coupling agent can be used as long as it is an organosilicon compound having an epoxy group and does not impair the effects of the present invention. Examples of such epoxy-based silane coupling agents include 2-(3,4-epoxycyclohexyl)ethylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropyltriethoxysilane. Commercially available epoxy silane coupling agents include, for example, KBM-303, KBM-402, KBM-403, KBE-402, KBE-403, KR-516, and X-12-981S (all manufactured by Shin-Etsu Chemical Co., Ltd.), SH6040, Z-6040, Z-6042, Z-6043, and Z-6044 (all manufactured by Dow Corning Toray Co., Ltd.), and A-186, A-187, and A-1871 (all manufactured by Momentive Performance Materials, Inc.).

[0027] Examples of the epoxy compound (B) include, in addition to epoxy silane coupling agents, sorbitol polyglycidyl ethers and water-soluble epoxy resins. Commercially available epoxy compounds (B) include Denacol EX-612, EX-614, and EX-622 (all manufactured by Nagase ChemteX Corporation), W2801, W2821R70, and WD11M60 (all manufactured by Mitsubishi Chemical Corporation).

[0028] In the adhesive according to an embodiment of the present invention, the total content of the amino compound (A) and the epoxy compound (B) relative to the total content of the amino compound (A), the epoxy compound (B), and the solvent (C) is preferably more than 0.01% by weight but less than 20% by weight, or may be more than 0.01% by weight but less than 10% by weight, more than 0.05% by weight but less than 5% by weight, more than 0.10% by weight but less than 5% by weight, more than 0.50% by weight but less than 4% by weight, or more than 0.50% by weight but less than 3% by weight. In the adhesive according to an embodiment of the present invention, if the total content of the amino compound (A) and the epoxy compound (B) relative to the total content of the amino compound (A), the epoxy compound (B), and the solvent (C) is adjusted within the above range, the effects of the present invention can be further exhibited.

[0029] When the adhesive according to an embodiment of the present invention contains both an amino compound (A) and an epoxy compound (B), the content ratio of the amino compound (A) to the epoxy compound (B) is preferably 6:94 to 90:10, alternatively 8:92 to 70:30, 8:92 to 60:40, 10:90 to 55:45, 20:80 to 55:45, or 30:70 to 55:45, in terms of molar ratio. When the content ratio of the amino compound (A) to the epoxy compound (B) is within the above range, the effects of the present invention can be more effectively exhibited.

[0030] The adhesive according to an embodiment of the present invention may contain any suitable additive as long as it does not impair the effects of the present invention. Such additives may be used alone or in combination of two or more types. Examples of such additives include binder resins, surfactants, plasticizers, tackifiers, low-molecular-weight polymers, polymerizable monomers, surface lubricants, leveling agents, antioxidants, corrosion inhibitors, light stabilizers, UV absorbers, polymerization inhibitors, silane coupling agents, titanium coupling agents, inorganic or organic fillers, metal powders, particles, and foil-like materials. Examples of binder resins include acrylic resins, styrene resins, polyvinyl alcohol resins, urethane resins, polyester resins, polypropylene resins, polyethylene resins, epoxy resins, and polycarbonate resins.

[0031] The content of the additive in the adhesive according to the embodiment of the present invention is preferably 0% by weight to 10% by weight, may be 0% by weight to 5% by weight, may be 0% by weight to 3% by weight, may be 0% by weight to 2% by weight, may be 0% by weight to 1% by weight, or may be 0% by weight to 0.5% by weight.

[0032] 2. Optical Laminate An optical laminate according to an embodiment of the present invention is an optical laminate in which a first light-transmitting optical film and a second light-transmitting optical film are bonded together with an adhesive layer formed from an adhesive according to an embodiment of the present invention. That is, the optical laminate according to an embodiment of the present invention has, in this order, a first light-transmitting optical film, an adhesive layer, and a second light-transmitting optical film. By employing an adhesive layer formed from an adhesive according to an embodiment of the present invention as the adhesive layer, the optical laminate according to an embodiment of the present invention can achieve excellent adhesion between the first light-transmitting optical film, the adhesive layer, and the second light-transmitting optical film.

[0033] Fig. 1 is a schematic cross-sectional view of one embodiment of the optical laminate of the present invention. In Fig. 1, the optical laminate 100 includes a first light-transmitting optical film 10 and a second light-transmitting optical film 20 bonded together with an adhesive layer 30. The adhesive layer 30 is an adhesive layer formed from an adhesive according to an embodiment of the present invention.

[0034] The thickness of the optical laminate according to the embodiment of the present invention may be any appropriate thickness as long as the effects of the present invention are not impaired. Such a thickness is, for example, 1 μm to 400 μm, or may be 2 μm to 200 μm. From the viewpoint of thinning, the thickness of the light-transmitting optical film is, for example, 1 μm to 100 μm, or may be 2 μm to 80 μm, 2 μm to 60 μm, 2 μm to 40 μm, 2 μm to 20 μm, or 2 μm to 10 μm.

[0035] In the optical laminate according to the embodiment of the present invention, the thickness of the adhesive layer can be very small, preferably 50 nm or less, and may be 40 nm or less, 38 nm or less, 35 nm or less, 30 nm or less, less than 30 nm, 25 nm or less, 20 nm or less, 15 nm or less, or 10 nm or less. The lower limit of the thickness of the adhesive layer is, for example, 1 nm or more, and may be 2 nm or more.

[0036] In the optical laminate according to an embodiment of the present invention, when the thickness of the adhesive layer is set to be thinner than 1 / 10 of the wavelength of external light, for example, set to be very small as described above, the effects of the present invention can be more effectively exhibited and, further, reflection unevenness of external light reflection can be more effectively reduced. In particular, even if there is a large difference in refractive index between the adhesive layer and the translucent optical film attached adjacent to it, the adhesive layer is so thin that the optical path length (product of thickness and refractive index) of the adhesive layer can be made small, which eliminates the optical sensitivity of the adhesive layer and prevents interference of reflected light. The thinner this thickness is, the greater the effect of suppressing reflection unevenness can be.

[0037] In the optical laminate according to an embodiment of the present invention, the thickness of the adhesive layer is preferably 1 / 10 of the wavelength of 500 nm, which has a particularly high visibility, i.e., a thickness of 50 nm or less. Furthermore, even with light having a wavelength shorter than 500 nm, interference is sufficiently suppressed and coloring is lighter than when the adhesive layer is about 1 μm thick, making it fully practical. Furthermore, since visible light is 380 nm to 780 nm, the thickness of the adhesive layer is more preferably 38 nm or less, and even more preferably 30 nm or less. Furthermore, considering that the optical path length is preferably 1 / 10 of the target visible light wavelength and that the refractive index of the adhesive layer is typically around 1.40 to 1.60, the thickness of the adhesive layer is preferably 30 nm or less. Furthermore, when industrially produced, considering the margin of the adhesive layer, it is preferable that the maximum thickness of the adhesive layer does not exceed 30 nm, and the average thickness is preferably 25 nm or less.

[0038] In the optical laminate according to an embodiment of the present invention, when the thickness of the adhesive layer is designed as described above, the effects of the present invention can be more effectively exhibited, and furthermore, reflection unevenness of external light reflection can be more effectively reduced. In particular, even if there is a large difference in refractive index between the adhesive layer and the light-transmitting optical film attached adjacent to it, the optical path length (product of thickness and refractive index) of the adhesive layer can be reduced because the adhesive layer is thin, which eliminates the sensitivity of the adhesive layer to light and prevents interference of reflected light. The reason why the thinner the thickness, the greater the effect of suppressing reflection unevenness can be is presumed to be as follows.

[0039] Image display devices typically include an optical laminate in which many optical films are stacked together, in addition to a display element that forms an image. This optical laminate is an essential component of image display devices, as it enhances the display performance of the image display device and adds anti-reflection functionality. From the perspective of power consumption, image display devices typically display black in a non-illuminated state, known as normally black. When external light (visible light) enters an image display device, reflection occurs at the interfaces of the optical elements that make up the optical laminate. Such light reflection at the interfaces of the optical elements is particularly noticeable in non-illuminated states, particularly in organic electroluminescence (EL) displays. Furthermore, when the thickness between optical elements is in the range of several hundred nanometers to several micrometers, the reflected light appears colored due to the interference of reflected light at adjacent interfaces.

[0040] In image display devices, the occurrence of reflection unevenness, which is visually noticeable due to the reflection of external light when the device is turned off (OFF), has become a problem. Reflection unevenness due to reflection of external light is observed as a change in the reflection spectrum, and is typically seen as a relatively strong pink reflection in a weak green reflection. It is believed that coloring that occurs when reflected light interferes at two thin interfaces between optical elements is the cause of reflection unevenness. After investigating the cause of such reflection unevenness, the researchers focused on the fact that the strong color change is caused by a change in wavelength of constructive interference due to a change in thickness at two thin interfaces between optical elements. The researchers then considered that the influence of optical elements, particularly the interface between an adhesive layer bonding a translucent optical film and the adjacent translucent optical film, is significant, and that unevenness or waviness in the thickness of the adhesive layer causes a change in the wavelength of constructive or destructive interference in the reflected light generated at the two interfaces sandwiching the adhesive layer, resulting in the observed color unevenness. Furthermore, it is believed that if there is a large difference in refractive index between the adhesive layer and the light-transmitting optical film bonded adjacent to it, the presence of an interface between the adhesive layer and the optical element bonded adjacent to it, particularly the light-transmitting optical film, will result in noticeable reflection of external light.

[0041] Therefore, we thought that when thickness unevenness or waviness occurs in the adhesive layer, there will be areas where the optical path length of the reflected light (the product of thickness and refractive index) differs within the surface, causing uneven interference of the reflected light at the interface, and as a result, the uneven reflection will become more noticeable.We investigated whether the problem could be solved using technical means that take the optical path length into consideration, and thought that if the optical path length was sufficiently small for the target visible light wavelength, the adhesive layer would lose its sensitivity to light and interference of the reflected light would no longer occur.

[0042] After extensive investigations based on the above-mentioned concepts, it was found that, using a thickness of 1 / 10 of the wavelength of external light as a standard for the thickness of the adhesive layer, if an adhesive layer thinner than 1 / 10 of the wavelength of external light is used, even if there is a large difference in refractive index between the adhesive layer and the adjacent light-transmitting optical film bonded thereto, the adhesive layer is thin and the optical path length (product of thickness and refractive index) of the adhesive layer can be made small, thereby eliminating the sensitivity of the adhesive layer to light and preventing interference of reflected light. This is because, when the thickness of the adhesive layer is set as described above, the adhesive layer can be treated as if it does not exist to light, and even if there is thickness unevenness in the adhesive layer, the adhesive layer itself is in a state that is imperceptible to light in the first place, so there is no interference of reflected light due to interfacial reflection at the two interfaces between the adhesive layer and the adjacent layer, and therefore the reflection unevenness itself is not observed. In particular, since the wavelength of external light with high luminosity is in the 500 to 610 nm range, centered around 555 nm, where the maximum relative luminosity is achieved, it was discovered that if the thickness of the adhesive layer is 1 / 10 of 500 nm, i.e., 50 nm or less, reflection unevenness at wavelengths longer than 500 nm is further suppressed, and the thinner the thickness, the greater the effect of suppressing reflection unevenness. If the thickness of the adhesive layer is further reduced, for example to 30 nm, even if the adhesive layer has a high refractive index of about 1.60, the optical path length will be 48 nm, which is about 1 / 8 to 1 / 16 of the visible light wavelength (380 nm to 780 nm). For light with wavelengths of 500 nm or longer, which are particularly influential as a cause of reflection unevenness, the optical path length will be less than 1 / 10, resulting in an extremely high effect of suppressing reflection unevenness.

[0043] In addition, when the adhesive layer is sufficiently thick, for example, when it exceeds 20 μm, there are many wavelengths in the visible light range that interfere with each other constructively and destructively due to the interference of reflected light at the interface, and therefore the order of interference is sufficiently large, making it difficult to observe interference colors and the reflected light becomes nearly achromatic. For this reason, even if the thickness of the adhesive layer varies, reflection unevenness as color unevenness is often not observed in practice.

[0044] In an optical laminate according to an embodiment of the present invention, reflection unevenness in external light reflection can be effectively reduced even if there is a large difference in refractive index between the adhesive layer and the translucent optical film bonded adjacent to it. Therefore, in an optical laminate according to an embodiment of the present invention, the in-plane refractive index difference between the first translucent optical film and the adhesive layer may be large, and the in-plane refractive index difference between the second translucent optical film and the adhesive layer may be large. That is, a translucent optical film having a high refractive index can be used as the first translucent optical film or the second translucent optical film. Conventionally, optical laminates in which two translucent optical films having high refractive indexes are bonded together with an adhesive have exhibited noticeable reflection unevenness in external light reflection. However, according to the present invention, reflection unevenness in external light reflection can be effectively reduced even when a translucent optical film having a high refractive index is used as the first translucent optical film or the second translucent optical film.

[0045] The in-plane refractive index difference (absolute value) between the first light-transmitting optical film and the adhesive layer is preferably 0.05 or more, and may be 0.08 or more, 0.10 or more, 0.12 or more, 0.14 or more, or 0.16 or more. The upper limit of the in-plane refractive index difference (absolute value) between the first light-transmitting optical film and the adhesive layer is, for example, 0.26 or less.

[0046] The in-plane refractive index difference (absolute value) between the second light-transmitting optical film and the adhesive layer is preferably 0.05 or more, and may be 0.08 or more, 0.10 or more, 0.12 or more, 0.14 or more, or 0.16 or more. The upper limit of the in-plane refractive index difference (absolute value) between the second light-transmitting optical film and the adhesive layer is, for example, 0.26 or less.

[0047] <2-1. Light-transmitting optical film> The first light-transmitting optical film and the second light-transmitting optical film (for convenience of explanation, these two light-transmitting optical films may be simply referred to as "light-transmitting optical films") may be the same type of light-transmitting optical film or different types of light-transmitting optical films.

[0048] The thickness of each of the first light-transmitting optical film and the second light-transmitting optical film may be any appropriate thickness as long as the effects of the present invention are not impaired. Such a thickness is, for example, 0.5 μm to 200 μm, or may be 1 μm to 100 μm, or may be 1 μm to 50 μm. From the viewpoint of thinning, the thickness of the light-transmitting optical film is, for example, 0.5 μm to 50 μm, or may be 1 μm to 40 μm, or may be 1 μm to 30 μm, or may be 1 μm to 20 μm, or may be 1 μm to 10 μm, or may be 1 μm to 5 μm.

[0049] The in-plane refractive index of the first translucent optical film is preferably 1.50 or more, and may be 1.52 or more, 1.54 or more, 1.56 or more, 1.58 or more, 1.60 or more, 1.61 or more, or 1.62 or more. There is a tendency that the higher the upper limit of the in-plane refractive index of the first translucent optical film, the better, but based on realistic material selection, etc., it is, for example, 1.72 or less. The optical laminate according to the embodiment of the present invention can effectively reduce reflection unevenness of external light reflection even if the in-plane refractive index of the first translucent optical film is as high as described above.

[0050] The second translucent optical film preferably has an in-plane refractive index of 1.50 or more, and may be 1.52 or more, 1.54 or more, 1.56 or more, 1.58 or more, 1.60 or more, 1.61 or more, or 1.62 or more. There is a tendency that the higher the upper limit of the in-plane refractive index of the second translucent optical film, the better, but based on realistic material selection and the like, it is, for example, 1.72 or less. The optical laminate according to the embodiment of the present invention can effectively reduce reflection unevenness of external light reflection even if the in-plane refractive index of the second translucent optical film is as high as described above.

[0051] Any suitable light-transmitting optical film can be used as the light-transmitting optical film as long as the effects of the present invention are not impaired. Examples of such light-transmitting optical films include retardation films (retardation layers), polarizers, polarizing films (laminated films including a polarizer and a polarizer protective film), polarizer protective films, brightness-enhancing films, and resin substrate films.

[0052] Any suitable material can be used as the material for the light-transmitting optical film as long as it does not impair the effects of the present invention. Examples of such materials include polycarbonate resins (including polyester carbonate resins), polyester resins (PET, etc.), polyvinyl acetal resins, polyarylate resins, polyolefin resins, cyclic polyolefin resins (e.g., norbornene resins), cycloolefin resins, cellulose resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, acrylic resins, and polyvinyl alcohol resins. These resins may be used alone or in combination (e.g., blends or copolymers).

[0053] In one preferred embodiment of the present invention, at least one of the first and second light-transmitting optical films may be a retardation film, and both the first and second light-transmitting optical films may be retardation films. When both the first and second light-transmitting optical films are retardation films, they may be a combination of a λ / 2 plate and a λ / 4 plate, or a λ / 3 plate and a λ / 6 plate, a λ / 2 plate and a C plate, or a λ / 4 plate and a C plate. Note that an optical element in which the relationship between the in-plane refractive indexes nx and ny and the refractive index nz in the thickness direction satisfies nx = ny > nz is called a negative C plate, and an optical element in which nx = ny < nz is called a positive C plate. These are collectively called C plates. Here, "nx = ny" includes not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. That is, the in-plane retardation Re(550) of the retardation film can be 20 nm or less, preferably 10 nm or less, and more preferably 5 nm or less.

[0054] The light-transmitting optical film may have any appropriate treatment layer formed on its surface, as long as the effects of the present invention are not impaired. Examples of such treatment layers include a hard coat layer, an easy-adhesion layer, an anti-reflection treatment, an anti-glare treatment, and an anti-sticking treatment layer.

[0055] The surface of the light-transmitting optical film may be subjected to any appropriate activation treatment within the scope of the present invention, for the purpose of improving adhesiveness, etc. Examples of such activation treatments include corona treatment, plasma treatment, saponification treatment, and low-pressure UV treatment.

[0056] The light-transmitting optical film may be a stretched film. Generally, optical anisotropy is imparted to a retardation film or a polarizer by orienting a polymer chain or a dichroic material through stretching. In the present invention, an optical laminate may be produced using a light-transmitting optical film that has been stretched in advance to impart optical anisotropy, or an optical laminate produced using a light-transmitting optical film may be stretched to impart optical anisotropy.

[0057] The light-transmitting optical film may contain any appropriate additive as long as it does not impair the effects of the present invention. Such additives may be contained alone or in combination of two or more. Examples of such additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, color inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and colorants.

[0058] As described above, any appropriate light-transmitting optical film can be used as the light-transmitting optical film as long as the effects of the present invention are not impaired. Hereinafter, as one embodiment of the light-transmitting optical film, a case where the light-transmitting optical film is a retardation film will be described.

[0059] <2-1-a. First Retardation Film> When the first light-transmitting optical film is a retardation film, it is referred to as a first retardation film.

[0060] In one embodiment, the first retardation film has a refractive index characteristic of nx>ny. Here, the relationship between ny and nz may be ny<nz, ny=nz, or ny>nz. In one embodiment, the first retardation film may function as a λ / 2 plate. In one embodiment, the first retardation film may function as a λ / 3 plate.

[0061] In one embodiment, the first retardation film has a refractive index characteristic of nx=ny. Here, the relationship between nx and nz may be nx<nz, nx>nz. In one embodiment, the first retardation film may function as a C-plate.

[0062] Examples of the first retardation film include a retardation film that is a λ / 2 plate having a front retardation of 200 nm or more and a thickness direction retardation of 0 nm or more. The front retardation is usually controlled in the range of 200 nm to 350 nm, and the thickness direction retardation is usually controlled in the range of 0 nm to 450 nm. Another example is a retardation film that is a C plate having a front retardation of 0 nm and a thickness direction retardation of −50 nm or less or 50 nm or more. The front retardation is usually controlled in the range of −10 nm to 10 nm, and the thickness direction retardation is usually controlled in the range of −200 nm to 200 nm.

[0063] The first retardation film may exhibit an inverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, may exhibit a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light, or may exhibit a flat wavelength dispersion characteristic in which the retardation value hardly changes depending on the wavelength of the measurement light.

[0064] The first retardation film may be, for example, a positive wavelength dispersion retardation film that satisfies the following conditions: 1.00<Re(450) / Re(550)<1.20 0.08<Δn<0.15 1.00<NZ<1.20, where Re(450) and Re(550) are in-plane retardations measured with light having wavelengths of 450 nm and 550 nm at 23° C., nx and ny are refractive indices of the retardation film in the slow axis direction and the fast axis direction, respectively, nx-ny is in-plane birefringence, Δn is in-plane birefringence, and Nz is the ratio of nx-nz, which is thickness direction birefringence, to nx-ny, which is in-plane birefringence, where nz is the refractive index in the thickness direction of the retardation film.

[0065] The Re(550) of the first retardation film is, for example, 130 nm to 350 nm, may be 160 nm to 330 nm, or may be 200 nm to 300 nm.

[0066] The first retardation film is formed of any appropriate material that can satisfy the above characteristics. The first retardation film can be composed of, for example, a resin film or an oriented and solidified layer of a liquid crystal compound, and is preferably an oriented and solidified layer of a liquid crystal compound. By using an oriented and solidified layer of a liquid crystal compound as the retardation film, it is possible to achieve a desired in-plane retardation with a thickness that is significantly thinner than that of a resin film. As a result, it is possible to significantly reduce the thickness of the optical laminate.

[0067] Examples of resins contained in the resin film include polycarbonate resins (including polyester carbonate resins), polyester resins, polyvinyl acetal resins, polyarylate resins, polyolefin resins, cyclic polyolefin resins (e.g., norbornene resins), cycloolefin resins, cellulose resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, acrylic resins, and polyvinyl alcohol resins. These resins may be used alone or in combination (e.g., blends or copolymers).

[0068] When the first retardation film exhibits reverse dispersion wavelength characteristics, a resin film containing a polycarbonate-based resin (including a polyester carbonate-based resin) can be suitably used.

[0069] As the polycarbonate-based resin, any suitable polycarbonate-based resin can be used as long as it does not impair the effects of the present invention. The polycarbonate-based resin contains, for example, structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, and structural units derived from at least one dihydroxy compound selected from the group consisting of alicyclic diols, alicyclic dimethanols, di-, tri-, or polyethylene glycols, and alkylene glycols or spiroglycols. The polycarbonate-based resin preferably contains structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, structural units derived from an alicyclic dimethanol and / or structural units derived from di-, tri-, or polyethylene glycol; more preferably, it contains structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, and structural units derived from di-, tri-, or polyethylene glycol. The polycarbonate-based resin may contain structural units derived from other dihydroxy compounds as necessary. Details of polycarbonate-based resins that can be suitably used for the first retardation film are described in, for example, JP 2014-10291 A, JP 2014-26266 A, JP 2015-212816 A, JP 2015-212817 A, and JP 2015-212818 A, and the descriptions of these publications are incorporated herein by reference.

[0070] When the first retardation film exhibits flat wavelength dispersion characteristics, a resin film containing a cycloolefin resin can be suitably used.

[0071] Cycloolefin resin is a general term for resins polymerized using cycloolefins as polymerization units, and examples thereof include resins described in JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, etc. Examples of cycloolefin resins include ring-opening (co)polymers of cycloolefins, addition polymers of cycloolefins, copolymers (typically random copolymers) of cycloolefins with α-olefins such as ethylene and propylene, graft modified products obtained by modifying these with unsaturated carboxylic acids or derivatives thereof, and hydrogenated products thereof. Specific examples of cycloolefins include norbornene monomers.Examples of norbornene-based monomers include norbornene and its alkyl and / or alkylidene substituted derivatives and polar group substituted derivatives such as halogen (for example, 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene), dicyclopentadiene, 2,3-dihydrodicyclopentadiene, dimethanooctadecane, and the like. Hydronaphthalene and its alkyl and / or alkylidene substituted derivatives and polar group substituted derivatives such as halogen (for example, 6-methyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethylidene-1,4:5,8-dimethano-1,4,4a,5,6,7,8, 8a-Octahydronaphthalene, 6-chloro-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-cyano-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-pyridyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4:5,8-dimethano Examples of suitable cycloolefins include 4,9:5,8-dimethano-3a,4,4a,5,8,8a,9,9a-octahydronaphthalene, and trimers and tetramers of cyclopentadiene (e.g., 4,9:5,8-dimethano-3a,4,4a,5,8,8a,9,9a-octahydro-1H-benzoindene and 4,11:5,10:6,9-trimethano-3a,4,4a,5,5a,6,9,9a,10,10a,11,11a-dodecahydro-1H-cyclopentaanthracene). Other cycloolefins capable of ring-opening polymerization may be used in combination. Examples of such other cycloolefins include compounds having one reactive double bond, such as cyclopentene, cyclooctene, and 5,6-dihydrodicyclopentadiene.

[0072] Various cycloolefin resin products are commercially available. Specific examples of commercially available cycloolefin resin products include "ZEONEX" and "ZEONOR" manufactured by Zeon Corporation, "Arton" manufactured by JSR Corporation, "TOPUS" manufactured by TICONA, and "APEL" manufactured by Mitsui Chemicals, Inc.

[0073] The first retardation film composed of a resin film can be obtained, for example, by stretching an unstretched resin film. Any appropriate stretching method and stretching conditions (e.g., stretching temperature, stretching ratio, stretching direction) can be employed for stretching. The stretching temperature is, for example, Tg-30°C to Tg+60°C, and may be Tg-10°C to Tg+50°C, relative to the glass transition temperature (Tg) of the resin film. In one embodiment, the first retardation film can be obtained by uniaxially stretching or fixed-end uniaxially stretching an unstretched resin film. A specific example of fixed-end uniaxial stretching is a method in which a resin film is stretched in the width direction (transverse direction) while traveling in the longitudinal direction. The stretching ratio is preferably 1.1 to 3.5 times. The thickness of the first retardation film made of a resin film is, for example, 10 μm to 100 μm, may be 10 μm to 70 μm, may be 10 μm to 60 μm, or may be 20 μm to 50 μm.

[0074] When the first retardation film is composed of an oriented and solidified layer of a liquid crystal compound, the first retardation film is typically oriented in a state where rod-shaped liquid crystal compounds are aligned in the slow axis direction of the first retardation film (homogeneous orientation). Examples of rod-shaped liquid crystal compounds include liquid crystal polymers and liquid crystal monomers. The liquid crystal compound is preferably polymerizable. If the liquid crystal compound is polymerizable, the orientation state of the liquid crystal compound can be fixed by aligning the liquid crystal compound and then polymerizing it.

[0075] An alignment and solidification layer of a liquid crystal compound (liquid crystal alignment and solidification layer) can be formed by performing an alignment treatment on the surface of a predetermined substrate, applying a coating liquid containing a liquid crystal compound to the surface to align the liquid crystal compound in a direction corresponding to the alignment treatment, and fixing the alignment state. Any appropriate alignment treatment can be used as the alignment treatment. Examples of the alignment treatment include mechanical alignment treatment, physical alignment treatment, and chemical alignment treatment. Specific examples of mechanical alignment treatment include rubbing treatment and stretching treatment. Specific examples of physical alignment treatment include magnetic field alignment treatment and electric field alignment treatment. Specific examples of chemical alignment treatment include oblique vapor deposition and photoalignment treatment. Any appropriate treatment conditions can be used for the alignment treatment depending on the purpose.

[0076] The alignment of liquid crystal compounds can be achieved by treating them at a temperature at which they exhibit a liquid crystal phase depending on the type of liquid crystal compound. By performing such temperature treatment, the liquid crystal compounds assume a liquid crystal state and are aligned in accordance with the alignment treatment direction of the substrate surface.

[0077] In one embodiment, the alignment state is fixed by cooling the aligned liquid crystal compound. When the liquid crystal compound is polymerizable or crosslinkable, the alignment state is fixed by subjecting the aligned liquid crystal compound to a polymerization treatment or a crosslinking treatment.

[0078] Any suitable liquid crystal polymer and / or liquid crystal monomer can be used as the liquid crystal compound. The liquid crystal polymer and liquid crystal monomer may each be one type only, or two or more types. Specific examples of liquid crystal compounds and methods for producing a liquid crystal alignment solidified layer are described in, for example, JP 2006-163343 A, JP 2006-178389 A, and WO 2018 / 123551 A. The descriptions in these publications are incorporated herein by reference.

[0079] When the first retardation film is constituted by a liquid crystal compound alignment solidified layer, the thickness of the first retardation film which is the liquid crystal alignment solidified layer is, for example, 0.5 μm to 10 μm, may be 0.5 μm to 8 μm, may be 0.5 μm to 6 μm, or may be 0.5 μm to 4 μm.

[0080] <2-1-b. Second Retardation Film> When the second light-transmitting optical film is a retardation film, it is referred to as a second retardation film.

[0081] In one embodiment, the second retardation film has a refractive index characteristic of nx>ny. Here, the relationship between ny and nz may be ny<nz, ny=nz, or ny>nz. In one embodiment, the second retardation film may function as a λ / 4 plate. In one embodiment, the second retardation film may function as a λ / 5 plate or a λ / 6 plate.

[0082] In one embodiment, the second retardation film has a refractive index characteristic of nx=ny, where nx and nz may have a relationship of nx<nz or nx>nz. In one embodiment, the second retardation film may function as a C-plate.

[0083] Examples of the second retardation film include a retardation film that is a λ / 4 plate having a front retardation of 90 nm or more and a thickness direction retardation of 0 nm or more. The front retardation is usually controlled in the range of 90 nm to 200 nm, and the thickness direction retardation is usually controlled in the range of 0 nm to 240 nm. Another example is a retardation film that is a C plate having a front retardation of 0 nm and a thickness direction retardation of −50 nm or less or 50 nm or more. The front retardation is usually controlled in the range of −10 nm to 10 nm, and the thickness direction retardation is usually controlled in the range of −200 nm to 200 nm.

[0084] The second retardation film may exhibit an inverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, may exhibit a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light, or may exhibit a flat wavelength dispersion characteristic in which the retardation value hardly changes depending on the wavelength of the measurement light.

[0085] The second retardation film may be, for example, a positive wavelength dispersion retardation film that satisfies the following conditions: 1.00<Re(450) / Re(550)<1.20 0.08<Δn<0.15 1.00<NZ<1.20, where Re(450) and Re(550) are in-plane retardations measured with light having wavelengths of 450 nm and 550 nm at 23° C., nx and ny are refractive indices of the retardation film in the slow axis direction and the fast axis direction, respectively, nx-ny is in-plane birefringence, Δn is in-plane birefringence, and Nz is the ratio of nx-nz, which is thickness direction birefringence, to nx-ny, which is in-plane birefringence, where nz is the refractive index in the thickness direction of the retardation film.

[0086] The Re(550) of the second retardation film is, for example, 70 nm to 200 nm, may be 90 nm to 160 nm, or may be 120 nm to 140 nm.

[0087] The arrangement order of the first retardation film and the second retardation film may be reversed.

[0088] The second retardation film is formed of any appropriate material that can satisfy the above characteristics. The second retardation film can be composed of, for example, a resin film or an oriented and solidified layer of a liquid crystal compound, and is preferably an oriented and solidified layer of a liquid crystal compound. By using an oriented and solidified layer of a liquid crystal compound as the retardation film, it is possible to achieve a desired in-plane retardation with a thickness that is significantly thinner than that of a resin film. As a result, it is possible to significantly reduce the thickness of the optical laminate.

[0089] The second retardation film made of a resin film may be referred to in the above description of the first retardation film made of a resin film. The second retardation film made of a layer of a liquid crystal compound with a fixed orientation may be referred to in the above description of the first retardation film made of a layer of a liquid crystal compound with a fixed orientation.

[0090] <2-2. Adhesive Layer> The adhesive layer is an adhesive layer formed from an adhesive according to an embodiment of the present invention. By employing an adhesive layer formed from an adhesive according to an embodiment of the present invention as the adhesive layer, the optical laminate according to an embodiment of the present invention can have excellent adhesion between the first translucent optical film, the adhesive layer, and the second translucent optical film. Furthermore, by appropriately setting the thickness of the adhesive layer as described above, reflection unevenness of external light reflection can be more effectively reduced. In particular, even if there is a large difference in refractive index between the adhesive layer and the translucent optical film attached adjacent to it, the adhesive layer's thin thickness can reduce the optical path length (product of thickness and refractive index) of the adhesive layer, which can eliminate the optical sensitivity of the adhesive layer and prevent interference of reflected light. The thinner the thickness, the greater the effect of suppressing reflection unevenness.

[0091] 3. Production of Optical Laminate The optical laminate according to the embodiment of the present invention can be produced by any appropriate method as long as the effects of the present invention are not impaired.

[0092] In one embodiment of the method for producing an optical laminate according to an embodiment of the present invention, an adhesive for forming an adhesive layer (the adhesive according to an embodiment of the present invention) is applied to a first light-transmitting optical film to form a coating film, and then the solvent contained in the adhesive is removed by drying as necessary. A second light-transmitting optical film is laminated on the formed coating film, and the coating film between the first light-transmitting optical film and the second light-transmitting optical film is heat-pressed to form an adhesive layer, thereby producing an optical laminate in which the first light-transmitting optical film and the second light-transmitting optical film are bonded together by the adhesive layer.

[0093] In another embodiment of the method for producing an optical laminate according to an embodiment of the present invention, an adhesive for forming an adhesive layer (the adhesive according to an embodiment of the present invention) is applied to a first light-transmitting optical film to form a coating film, and then a second light-transmitting optical film is laminated on the formed coating film, and if necessary, the solvent contained in the adhesive is removed by drying, and the coating film between the first light-transmitting optical film and the second light-transmitting optical film is cured to form an adhesive layer, thereby producing an optical laminate in which the first light-transmitting optical film and the second light-transmitting optical film are bonded together via the adhesive layer.

[0094] In yet another embodiment of the method for producing an optical laminate according to an embodiment of the present invention, an adhesive for forming an adhesive layer (the adhesive according to an embodiment of the present invention) is applied to a first light-transmitting optical film to form a coating film, and an adhesive for forming an adhesive layer (the adhesive according to an embodiment of the present invention) is applied to a second light-transmitting optical film to form a coating film, the first light-transmitting optical film on which the coating film has been formed and the second light-transmitting optical film on which the coating film has been formed are laminated together with the coating film facing inward, and if necessary, the solvent contained in the adhesive is removed by drying, and the coating film between the first light-transmitting optical film and the second light-transmitting optical film is cured to form an adhesive layer, thereby producing an optical laminate in which the first light-transmitting optical film and the second light-transmitting optical film are bonded together via the adhesive layer.

[0095] In yet another embodiment of the method for producing an optical laminate according to an embodiment of the present invention, an adhesive (an adhesive according to an embodiment of the present invention) is poured between a first light-transmitting optical film and a second light-transmitting optical film, and then the films are passed between a pair of laminating rolls, and if necessary, the solvent contained in the adhesive is removed by drying, and the coating film between the first light-transmitting optical film and the second light-transmitting optical film is cured to form an adhesive layer, thereby producing an optical laminate in which the first light-transmitting optical film and the second light-transmitting optical film are bonded together via the adhesive layer.

[0096] The method for producing an optical laminate according to an embodiment of the present invention is not limited to the above-exemplified embodiment, of course.

[0097] As a method for applying the adhesive (adhesive according to an embodiment of the present invention) for forming an adhesive layer on the first light-transmitting optical film, any appropriate method can be adopted as long as the effects of the present invention are not impaired. Examples of such application methods include a method of immersing the first light-transmitting optical film in an aqueous adhesive solution (dip coating method), curtain coating method, spray coating method, bar coating method, rod coating method, roll coating method, die coating method, and gravure coating method.

[0098] Before applying an adhesive (adhesive according to an embodiment of the present invention) for forming an adhesive layer on the first light-transmitting optical film, the surface of the first light-transmitting optical film may be subjected to any appropriate activation treatment within a range that does not impair the effects of the present invention. Examples of such activation treatments include corona treatment, plasma treatment, saponification treatment, and low-pressure UV treatment. In particular, when a first light-transmitting optical film made of a material that does not have polar groups is used, polar groups such as hydroxyl groups may be introduced into the surface of the first light-transmitting optical film by the activation treatment.

[0099] When an adhesive (an adhesive according to an embodiment of the present invention) for forming an adhesive layer is applied to a first light-transmitting optical film to form a coating film, and then the solvent contained in the adhesive is removed by drying, any appropriate drying method may be used as long as the effects of the present invention are not impaired. Examples of such drying methods include heat drying. Conditions such as the temperature and time for heat drying may be any appropriate conditions depending on the composition of the molecular adhesive solution, etc. Examples of such conditions include a heating temperature of 35°C to 120°C and a heating time of 30 seconds to 10 minutes.

[0100] Before laminating the second light-transmitting optical film on the coating film formed on the first light-transmitting optical film, the surface of the second light-transmitting optical film may be subjected to any appropriate activation treatment within a range that does not impair the effects of the present invention. Examples of such activation treatments include corona treatment, plasma treatment, saponification treatment, and low-pressure UV treatment. In particular, when a second light-transmitting optical film made of a material that does not have polar groups is used, polar groups such as hydroxyl groups may be introduced into the surface of the first light-transmitting optical film by the activation treatment.

[0101] As a method for laminating the second light-transmitting optical film on the coating film formed on the first light-transmitting optical film, any appropriate lamination method can be adopted as long as the effects of the present invention are not impaired. Examples of such a lamination method include lamination by pressure using a laminator or the like.

[0102] Before lamination, the first translucent optical film may have another film (for example, a supporting substrate) laminated on the surface opposite to the surface on which the adhesive layer is provided. Before lamination, the second translucent optical film may have another film (for example, a supporting substrate) laminated on the surface opposite to the surface on which the adhesive layer is provided. Such a supporting substrate may be finally peeled off and removed, or may be used as another optical film to be further laminated on the optical laminate according to the embodiment of the present invention.

[0103] As a curing method for curing the coating film between the first and second light-transmitting optical films to form an adhesive layer, any appropriate curing method can be adopted as long as the effects of the present invention are not impaired. Examples of such curing methods include curing by heating. Conditions for the temperature and time for curing by heating can be any appropriate conditions depending on the composition of the molecular adhesive solution, etc. Examples of such conditions include a heating temperature of 40°C to 150°C and a heating time of 1 minute to 20 minutes.

[0104] 4. Uses of the Optical Laminate The optical laminate according to an embodiment of the present invention can be used for any appropriate use. The optical laminate according to an embodiment of the present invention can be used, for example, in an image display device such as a liquid crystal display device or an organic EL display device. That is, the image display device according to an embodiment of the present invention includes the optical laminate according to an embodiment of the present invention.

[0105] The optical laminate according to the embodiment of the present invention can be used by laminating any other appropriate optical film, and can be used by providing any other appropriate layer. Examples of other optical films include a retardation film, a polarizer, a polarizing film (a laminate film including a polarizer and a polarizer protective film), a polarizer protective film, a brightness enhancement film, and a resin substrate film. Examples of other layers include a pressure-sensitive adhesive layer, another adhesive layer, a hard coat layer, an anti-reflection layer, and an anti-glare layer.

[0106] Fig. 2 is a schematic cross-sectional view of one embodiment of an optical member including an optical laminate according to an embodiment of the present invention. The optical member 1000 shown in Fig. 2 includes a polarizing film 40, an adhesive layer 50, an optical laminate 100 according to an embodiment of the present invention (a first light-transmitting optical film 10, an adhesive layer 30, and a second light-transmitting optical film 20), and a panel-side pressure-sensitive adhesive layer 60. The panel-side pressure-sensitive adhesive layer 60 enables the optical member 1000 to be attached to an image display cell, thereby constituting an image display device.

[0107] The image display device according to the embodiment of the present invention can be manufactured, for example, by appropriately assembling the optical laminate according to the embodiment of the present invention with other optical films, an image display cell, a backlight, etc., and incorporating a drive circuit. In the configuration of the image display device according to the embodiment of the present invention, the optical laminate according to the embodiment of the present invention can be used on one or both sides of the image display cell.

[0108] The present invention will be specifically described below using examples, but the present invention is not limited to these examples. The test and evaluation methods used in the examples are as follows. The term "parts" means "parts by weight" unless otherwise specified, and the term "%" means "% by weight" unless otherwise specified.

[0109] <Measurement of adhesive layer thickness> Using an apparatus named "HT7820" manufactured by Hitachi High-Technologies Corporation, cross-sectional TEM observation was performed by a frozen ultrathin section method including heavy metal staining to measure the thickness of the adhesive layer. The accelerating voltage during the measurement was 100 kV.

[0110] <Evaluation of Adhesion> A 15 mm wide strip sample (when the second translucent optical film was a λ / 4 plate retardation film, a sample cut to a width of 15 mm along the slow axis) was prepared from the optical laminate obtained in the Examples and Comparative Examples. The first translucent optical film was fixed to a glass plate with adhesive tape (manufactured by Nitto Denko Corporation, product name "No. 5000NS", thickness: 160 μm). The second translucent optical film was backed with polyimide tape (manufactured by Nitto Denko Corporation, product name "No. 360A", thickness: 25 μm) using a hand roller. Peeling of the polyimide tape-backed second translucent optical film was attempted at a peel angle of 90° and a peel rate of 20,000 mm / min under an environment of a temperature of 23° C. and a humidity of 50% RH. Evaluation was based on the following criteria. ⊚: The peel force was 1.6 N / 15 mm or more, or peeling was not possible. ◯: The peeling force was 1.0 N / 15 mm or more and less than 1.6 N / 15 mm. Δ: The peeling force was 0.5 N / 15 mm or more and less than 1.0 N / 15 mm. ×: The peeling force was less than 0.5 N / 15 mm.

[0111] <Evaluation of Adhesion After Moisture> A 15 mm wide strip sample (when the second translucent optical film was a λ / 4 plate retardation film, a sample cut to a width of 15 mm along the slow axis) was prepared from the optical laminate obtained in each of the Examples and Comparative Examples. The first translucent optical film was fixed to a glass plate with adhesive tape (manufactured by Nitto Denko Corporation, product name "No. 5000NS", thickness: 160 μm). The second translucent optical film was backed with polyimide tape (manufactured by Nitto Denko Corporation, product name "No. 360A", thickness: 25 μm) using a hand roller. The second translucent optical film backed with the polyimide tape was left for 240 hours in an environment of a temperature of 20° C. and a humidity of 98% RH. Thereafter, peeling was attempted at a peel angle of 90° and a peel rate of 20,000 mm / min. Evaluation was based on the following criteria. ⊚: The peel force was 1.6 N / 15 mm or more, or peeling was not possible. ◯: The peeling force was 1.0 N / 15 mm or more and less than 1.6 N / 15 mm. Δ: The peeling force was 0.5 N / 15 mm or more and less than 1.0 N / 15 mm. ×: The peeling force was less than 0.5 N / 15 mm.

[0112] <Measurement of refractive index> The refractive index of the adhesive layer was measured by preparing a thin adhesive layer having a thickness of 200 nm on an acrylic film (manufactured by Mitsubishi Chemical Corporation, trade name "ACRYPLEN", thickness: 20 μm) and using an ellipsometer (manufactured by J.A. Woollam Japan, trade name "RC2").

[0113] <Evaluation of Reflection Unevenness> [Evaluation 1] An adhesive tape was attached to the second light-transmitting optical film surface of the optical laminate obtained in the Examples and Comparative Examples, and this was then attached to a black acrylic plate. When a carrier was laminated on the light-transmitting optical film, the carrier film was peeled off before the film was attached to the acrylic plate. A fluorescent lamp was lit from the first light-transmitting optical film side, and observation was performed. The adhesive tape used was prepared by the following method. [Preparation of Acrylic Polymer] A four-neck flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser was charged with 92 parts by weight of butyl acrylate, 5 parts by weight of N-acryloylmorpholine (ACMO), 2.9 parts by weight of acrylic acid, 0.1 parts by weight of 2-hydroxyethyl acrylate, 0.1 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator, and 200 parts by weight of ethyl acetate. Nitrogen gas was introduced while gently stirring to replace the atmosphere with nitrogen. The liquid temperature in the flask was maintained at around 55°C, and a polymerization reaction was carried out for 8 hours to prepare an acrylic polymer solution. The weight-average molecular weight of the resulting acrylic polymer was 1.78 million. [Preparation of Pressure-Sensitive Adhesive Tape] The acrylic polymer solution obtained above was applied to one side of a silicone-treated polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical, thickness = 38 μm), and the film was dried and crosslinked at 150°C for 3 minutes to form a pressure-sensitive adhesive layer with a thickness of 5 μm after drying. The gel fraction of the pressure-sensitive adhesive layer at this time was 83 wt %, and the amount of decomposed peroxide after drying was 91 wt %. [Evaluation 2] In Evaluation 1, an irradiation-side linear polarizer was attached to the irradiation direction side of the fluorescent lamp used, and the fluorescent lamp was illuminated from the first light-transmitting optical film side through the irradiation-side linear polarizer. On the viewing side, a viewing-side linear polarizer was placed so as to be orthogonal (crossed Nicols) to the irradiation-side linear polarizer, and observation was performed from the first light-transmitting optical film side through the viewing-side linear polarizer. Observation was performed under conditions that suppressed surface reflection of the first light-transmitting optical film using the irradiation-side linear polarizer and the viewing-side linear polarizer. Evaluation was based on the following criteria: ⊚: No reflection unevenness was visible in either Evaluation 1 or Evaluation 2. ◯: Weak reflection unevenness was visible in Evaluation 2, but no reflection unevenness was visible in Evaluation 1. Δ: Reflection unevenness was visible in Evaluation 2, but no reflection unevenness was visible in Evaluation 1.×: Reflection unevenness was visually recognized in evaluation 2, and weak reflection unevenness was visually recognized in evaluation 1. XX: Reflection unevenness was visually recognized in evaluation 2, and reflection unevenness was also visually recognized in evaluation 1. <Evaluation of Appearance> The adhesive layers contained in the optical laminates obtained in the examples and comparative examples were measured over a distance of 100 cm using an apparatus named "DP74" manufactured by Olympus Corporation. 2 The adhesive layer was observed at 50x magnification in the range of 100-150°C, and the number of bubbles of 3 μm or larger that had occurred in the adhesive layer during production was counted. Evaluation was based on the following criteria: ◯: No bubbles were found. Δ: 1 to 3 bubbles were found. ×: 4 or more bubbles were found.

[0114] [Preparation Example 1] Preparation of 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 solids concentration of 30% by weight. A surfactant (BYK-360, BYK-Chemie) and a photopolymerization initiator (IGM Resins B.V.'s "Omnirad 907") were added to this solution to prepare a liquid crystal composition solution. The amounts of the surfactant and photopolymerization initiator added were 0.01 parts by weight and 3 parts by weight, respectively, relative to 100 parts by weight of the photopolymerizable liquid crystal compound.

[0115] [Production Example 2] Production of Retardation Film 1 (λ / 2 Retardation Film) A biaxially stretched norbornene film (manufactured by Zeon Corporation, trade name "ZEONORFILM", thickness = 33 μm, front retardation = 135 nm) was used as a substrate, and the liquid crystal composition solution prepared in Production Example 1 was applied to this substrate using a bar coater so that the phase difference was λ / 2, and the liquid crystal was aligned by heating at 100°C for 3 minutes. After cooling to room temperature, the film was irradiated with an accumulated light amount of 400 mJ / cm under a nitrogen atmosphere. 2 The laminate (1) was obtained by irradiating the film with ultraviolet light of 1000 W for photocuring, thereby obtaining a laminate (1) having a structure of substrate / phase difference film 1 (first liquid crystal alignment solidified layer). The first liquid crystal alignment solidified layer was homogeneously aligned and had a thickness of 2 μm. The refractive index of phase difference film 1 was 1.63.

[0116] [Production Example 3] Production of Retardation Film 2 (λ / 4 Retardation Film) A biaxially stretched norbornene film (manufactured by Zeon Corporation, trade name "ZEONORFILM", thickness = 33 μm, front retardation = 135 nm) was used as a substrate, and the liquid crystal composition solution prepared in Production Example 1 was applied to this substrate using a bar coater so that the phase difference was λ / 4, and the solution was heated at 100°C for 3 minutes to align the liquid crystal. After cooling to room temperature, the film was irradiated with an accumulated light amount of 400 mJ / cm under a nitrogen atmosphere. 2 The laminate (2) was obtained by irradiating the film with ultraviolet light of 1000 W for photocuring, thereby obtaining a laminate (2) having a structure of substrate / retardation film 2 (second liquid crystal alignment solidified layer). The second liquid crystal alignment solidified layer was homogeneously aligned and had a thickness of 1 μm. The refractive index of retardation film 2 was 1.62.

[0117] Example 1 Preparation of Adhesive (1) An amino silane coupling agent (N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-603") and an epoxy silane coupling agent (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") were mixed in a weight ratio of 1:1, and water was used as a solvent to prepare an aqueous solution with a total concentration (total concentration of amino compound (A) and epoxy compound (B)) of 1.0 wt%. 0.2 parts by weight of a surfactant (manufactured by Nissin Chemical Industry Co., Ltd., product name "EXP4200") was added to 100 parts by weight of the resulting aqueous solution to prepare Adhesive (1). The refractive index of the adhesive layer formed from Adhesive (1) was 1.46. <Production of Optical Laminate (1)> The first liquid crystal alignment solidified layer side of the laminate (1) obtained in Production Example 2 and the second liquid crystal alignment solidified layer side of the laminate (2) obtained in Production Example 3 were treated with a corona treatment machine at a treatment density of 50 W·min / m 2The corona treatment was carried out. Using an MCD coater (manufactured by Fuji Machine Co., Ltd.) (cell shape: honeycomb, gravure roll line count: 1000 / inch, rotation speed 130% / relative to line speed), the adhesive (1) was coated to a coating thickness of 1 μm on the corona-irradiated surface of the laminate (1), and then the laminate (2) was laminated using a lamination roll machine so that the corona-irradiated surface of the laminate (2) was the coated surface side. The lamination line speed was 15 m / min. The lamination was carried out so that the slow axis of the retardation film 2 (λ / 4 retardation film) was in a 60° relationship with the slow axis of the retardation film 1 (λ / 2 retardation film). After lamination, the laminate was heated and dried at 60 ° C. for 10 minutes to form an adhesive layer (1) from the adhesive (1), and the biaxially stretched norbornene-based films on both sides were peeled off from the resulting laminate to obtain an optical laminate (1) having a configuration of retardation film 1 / adhesive layer (1) / retardation film 2. The results are shown in Table 1.

[0118] [Example 2] <Preparation of adhesive (2)> An adhesive (2) was prepared in the same manner as in Example 1, except that the total concentration of the amino compound (A) and the epoxy compound (B) was adjusted to a 0.1 wt % aqueous solution. The refractive index of the adhesive layer formed from the adhesive (2) was 1.46. <Production of optical laminate (2)> An optical laminate (2) having a configuration of retardation film 1 / adhesive layer (2) / retardation film 2 was obtained in the same manner as in Example 1, except that instead of applying the adhesive (1) to a coating thickness of 1 μm, the adhesive (2) was applied to a coating thickness of 1 μm. The results are shown in Table 1.

[0119] Example 3 Preparation of Adhesive (3) Adhesive (3) was prepared in the same manner as in Example 1, except that the total concentration of the amino compound (A) and the epoxy compound (B) was adjusted to a 0.5 wt % aqueous solution. The refractive index of the adhesive layer formed from the adhesive (3) was 1.46. Production of Optical Laminate (3) An optical laminate (3) having a configuration of retardation film 1 / adhesive layer (3) / retardation film 2 was obtained in the same manner as in Example 1, except that instead of applying the adhesive (1) to a coating thickness of 1 μm, the adhesive (3) was applied to a coating thickness of 1 μm. The results are shown in Table 1.

[0120] Example 4 Preparation of Adhesive (4) Adhesive (4) was prepared in the same manner as in Example 1, except that the total concentration of the amino compound (A) and the epoxy compound (B) was adjusted to a 2.0 wt % aqueous solution. The refractive index of the adhesive layer formed from the adhesive (4) was 1.46. Production of Optical Laminate (4) An optical laminate (4) having a configuration of retardation film 1 / adhesive layer (4) / retardation film 2 was obtained in the same manner as in Example 1, except that instead of applying the adhesive (1) to a coating thickness of 1 μm, the adhesive (4) was applied to a coating thickness of 1 μm. The results are shown in Table 1.

[0121] [Example 5] <Preparation of adhesive (5)> The same procedure as in Example 1 was carried out, except that the total concentration of the amino compound (A) and the epoxy compound (B) was adjusted to a 3.0 wt % aqueous solution, to prepare adhesive (5). The refractive index of the adhesive layer formed from adhesive (5) was 1.46. <Production of optical laminate (5)> The same procedure as in Example 1 was carried out, except that adhesive (5) was applied to a coating thickness of 1 μm instead of adhesive (1), to obtain an optical laminate (5) having a configuration of retardation film 1 / adhesive layer (5) / retardation film 2. The results are shown in Table 1.

[0122] Example 6 Preparation of Adhesive (6) Adhesive (6) was prepared in the same manner as in Example 1, except that the total concentration of the amino compound (A) and the epoxy compound (B) was adjusted to a 5.0 wt % aqueous solution. The refractive index of the adhesive layer formed from the adhesive (6) was 1.46. Production of Optical Laminate (6) An optical laminate (6) having a configuration of retardation film 1 / adhesive layer (6) / retardation film 2 was obtained in the same manner as in Example 1, except that instead of applying the adhesive (1) to a coating thickness of 1 μm, the adhesive (6) was applied to a coating thickness of 1 μm. The results are shown in Table 1.

[0123] Example 7 Preparation of Adhesive (7) An amino silane coupling agent (N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-603") and an epoxy silane coupling agent (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") were mixed in a weight ratio of 9:1, and water was used as a solvent to prepare an aqueous solution with a total concentration (total concentration of amino compound (A) and epoxy compound (B)) of 1.0 wt%. 0.2 parts by weight of a surfactant (manufactured by Nissin Chemical Industry Co., Ltd., product name "EXP4200") was added to 100 parts by weight of the resulting aqueous solution to prepare Adhesive (7). The refractive index of the adhesive layer formed from Adhesive (7) was 1.46. <Production of Optical Laminate (7)> ​​The same procedure as in Example 1 was carried out, except that instead of applying the adhesive (1) to a coating thickness of 1 μm, the adhesive (7) was applied to a coating thickness of 1 μm, to obtain an optical laminate (7) having a configuration of retardation film 1 / adhesive layer (7) / retardation film 2. The results are shown in Table 1.

[0124] Example 8 Preparation of Adhesive (8) An amino silane coupling agent (N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-603") and an epoxy silane coupling agent (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") were mixed in a weight ratio of 7:3, and water was used as a solvent to prepare an aqueous solution with a total concentration (total concentration of amino compound (A) and epoxy compound (B)) of 1.0 wt%. 0.2 parts by weight of a surfactant (manufactured by Nissin Chemical Industry Co., Ltd., product name "EXP4200") was added to 100 parts by weight of the resulting aqueous solution to prepare an adhesive (8). The refractive index of the adhesive layer formed from the adhesive (8) was 1.46. <Production of optical laminate (8)> The same procedure as in Example 1 was carried out, except that instead of applying the adhesive (1) to a coating thickness of 1 μm, the adhesive (8) was applied to a coating thickness of 1 μm, to obtain an optical laminate (8) having a configuration of retardation film 1 / adhesive layer (8) / retardation film 2. The results are shown in Table 1.

[0125] Example 9 Preparation of Adhesive (9) An amino silane coupling agent (N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-603") and an epoxy silane coupling agent (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") were mixed in a weight ratio of 6:4, and water was used as a solvent to prepare an aqueous solution with a total concentration (total concentration of amino compound (A) and epoxy compound (B)) of 1.0 wt%. 0.2 parts by weight of a surfactant (manufactured by Nissin Chemical Industry Co., Ltd., product name "EXP4200") was added to 100 parts by weight of the resulting aqueous solution to prepare Adhesive (9). The refractive index of the adhesive layer formed from Adhesive (9) was 1.46. <Production of optical laminate (9)> The same procedure as in Example 1 was carried out, except that instead of applying the adhesive (1) to a coating thickness of 1 μm, the adhesive (9) was applied to a coating thickness of 1 μm, to obtain an optical laminate (9) having a configuration of retardation film 1 / adhesive layer (9) / retardation film 2. The results are shown in Table 1.

[0126] Example 10 Preparation of Adhesive (10) An amino silane coupling agent (N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-603") and an epoxy silane coupling agent (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") were mixed in a weight ratio of 8:92, and water was used as a solvent to prepare an aqueous solution with a total concentration (total concentration of amino compound (A) and epoxy compound (B)) of 1.0 wt%. 0.2 parts by weight of a surfactant (manufactured by Nissin Chemical Industry Co., Ltd., product name "EXP4200") was added to 100 parts by weight of the resulting aqueous solution to prepare an adhesive (10). The refractive index of the adhesive layer formed from the adhesive (10) was 1.47. <Production of optical laminate (10)> The same procedure as in Example 1 was carried out, except that instead of applying the adhesive (1) to a coating thickness of 1 μm, the adhesive (10) was applied to a coating thickness of 1 μm, to obtain an optical laminate (10) having a configuration of retardation film 1 / adhesive layer (10) / retardation film 2. The results are shown in Table 1.

[0127] Example 11 Preparation of Adhesive (11) An amino silane coupling agent (N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-603") and an epoxy silane coupling agent (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") were mixed in a weight ratio of 6:94, and water was used as a solvent to prepare an aqueous solution with a total concentration (total concentration of amino compound (A) and epoxy compound (B)) of 1.0 wt%. 0.2 parts by weight of a surfactant (manufactured by Nissin Chemical Industry Co., Ltd., product name "EXP4200") was added to 100 parts by weight of the resulting aqueous solution to prepare an adhesive (11). The refractive index of the adhesive layer formed from the adhesive (11) was 1.47. <Production of optical laminate (11)> The same procedure as in Example 1 was carried out, except that instead of applying the adhesive (1) to a coating thickness of 1 μm, the adhesive (11) was applied to a coating thickness of 1 μm, to obtain an optical laminate (11) having a configuration of retardation film 1 / adhesive layer (11) / retardation film 2. The results are shown in Table 1.

[0128] Example 12 Preparation of Adhesive (12) Polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., product name "SP-200") and an epoxy silane coupling agent (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") were mixed in a weight ratio of 1:1, and water was used as a solvent to prepare an aqueous solution with a total concentration (total concentration of amino compound (A) and epoxy compound (B)) of 2.0 wt%. 0.2 parts by weight of a surfactant (manufactured by Nissin Chemical Industry Co., Ltd., product name "EXP4200") was added to 100 parts by weight of the resulting aqueous solution to prepare an adhesive (12). The refractive index of the adhesive layer formed from the adhesive (12) was 1.51. <Production of optical laminate (12)> The same procedure as in Example 1 was carried out, except that instead of applying the adhesive (1) to a coating thickness of 1 μm, the adhesive (12) was applied to a coating thickness of 1 μm, to obtain an optical laminate (12) having a configuration of retardation film 1 / adhesive layer (12) / retardation film 2. The results are shown in Table 1.

[0129] Example 13 Preparation of Adhesive (13) An amino silane coupling agent (3-aminopropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-903") and an epoxy silane coupling agent (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") were mixed in a weight ratio of 1:1, and water was used as a solvent to prepare an aqueous solution with a total concentration (total concentration of amino compound (A) and epoxy compound (B)) of 2.0 wt%. 0.2 parts by weight of a surfactant (manufactured by Nissin Chemical Industry Co., Ltd., product name "EXP4200") was added to 100 parts by weight of the resulting aqueous solution to prepare an adhesive (13). The refractive index of the adhesive layer formed from the adhesive (13) was 1.47. <Production of optical laminate (13)> The same procedure as in Example 1 was carried out, except that instead of applying the adhesive (1) to a coating thickness of 1 μm, the adhesive (13) was applied to a coating thickness of 1 μm, to obtain an optical laminate (13) having a configuration of retardation film 1 / adhesive layer (13) / retardation film 2. The results are shown in Table 1.

[0130] Example 14 Preparation of Adhesive (14) An amino silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., product name "X-12-972F") and an epoxy silane coupling agent (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") were mixed in a weight ratio of 1:1, and water was used as a solvent to prepare an aqueous solution with a total concentration (total concentration of amino compound (A) and epoxy compound (B)) of 2.0 wt%. 0.2 parts by weight of a surfactant (manufactured by Nissin Chemical Industry Co., Ltd., product name "EXP4200") was added to 100 parts by weight of the resulting aqueous solution to prepare an adhesive (14). The refractive index of the adhesive layer formed from the adhesive (14) was 1.46. <Production of optical laminate (14)> The same procedure as in Example 1 was carried out, except that instead of applying the adhesive (1) to a coating thickness of 1 μm, the adhesive (14) was applied to a coating thickness of 1 μm, to obtain an optical laminate (14) having a configuration of retardation film 1 / adhesive layer (14) / retardation film 2. The results are shown in Table 1.

[0131] Example 15 Preparation of Adhesive (15) An amino-based silane coupling agent (N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-603") was mixed with water as a solvent to give a concentration of 1.0 wt % in an aqueous solution, to prepare an aqueous solution. 0.2 parts by weight of a surfactant (manufactured by Nissin Chemical Industry Co., Ltd., product name "EXP4200") was added to 100 parts by weight of the obtained aqueous solution to prepare an adhesive (15). The refractive index of the adhesive layer formed from the adhesive (15) was 1.46. Production of Optical Laminate (15) The same procedure as in Example 1 was performed, except that instead of applying the adhesive (1) to a coating thickness of 1 μm, the adhesive (15) was applied to a coating thickness of 1 μm, and an optical laminate (15) having a configuration of retardation film 1 / adhesive layer (15) / retardation film 2 was obtained. The results are shown in Table 1.

[0132] Example 16 Preparation of Adhesive (16) An adhesive (16) was prepared in the same manner as in Example 1, except that the total concentration of the amino compound (A) and the epoxy compound (B) was adjusted to a 10.0 wt % aqueous solution. The refractive index of the adhesive layer formed from the adhesive (16) was 1.46. Production of Optical Laminate (16) An optical laminate (16) having a configuration of retardation film 1 / adhesive layer (16) / retardation film 2 was obtained in the same manner as in Example 1, except that instead of applying the adhesive (1) to a coating thickness of 1 μm, the adhesive (16) was applied to a coating thickness of 0.5 μm. The results are shown in Table 1.

[0133] Example 17 Production of Optical Laminate (17) The same procedure as in Example 1 was carried out, except that instead of applying the adhesive (1) to a coating thickness of 1 μm, the adhesive (16) obtained in Example 16 was applied to a coating thickness of 1 μm, to obtain an optical laminate (17) having a configuration of retardation film 1 / adhesive layer (17) / retardation film 2. The results are shown in Table 1.

[0134] Example 18 Preparation of Adhesive (18) An amino silane coupling agent (N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-603") and an epoxy silane coupling agent (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") were mixed in a weight ratio of 1:1, and the total concentration of these (total concentration of amino compound (A) and epoxy compound (B)) was 1.0 wt% in a methanol solution. Methanol was used as a solvent to prepare a methanol solution. 0.2 parts by weight of a surfactant (manufactured by Nissin Chemical Industry Co., Ltd., product name "EXP4200") was added to 100 parts by weight of the resulting methanol solution to prepare an adhesive (18). The refractive index of the adhesive layer formed from the adhesive (18) was 1.46. <Production of optical laminate (18)> The same procedure as in Example 1 was carried out, except that instead of applying the adhesive (1) to a coating thickness of 1 μm, the adhesive (18) was applied to a coating thickness of 1 μm, to obtain an optical laminate (18) having a configuration of retardation film 1 / adhesive layer (18) / retardation film 2. The results are shown in Table 1.

[0135] [Example 19] <Preparation of adhesive (19)> Adhesive (19) was prepared in the same manner as in Example 18, except that ethanol was used as the solvent instead of methanol. The refractive index of the adhesive layer formed from adhesive (19) was 1.46. <Production of optical laminate (19)> An optical laminate (19) having a configuration of retardation film 1 / adhesive layer (19) / retardation film 2 was obtained in the same manner as in Example 1, except that adhesive (19) was applied to a coating thickness of 1 μm instead of applying adhesive (1) to a coating thickness of 1 μm. The results are shown in Table 1.

[0136] Example 20 Preparation of Adhesive (20) An adhesive (20) was prepared in the same manner as in Example 18, except that a mixed solvent of ethanol:water = 97:3 (weight ratio) was used instead of methanol as the solvent. The refractive index of the adhesive layer formed from the adhesive (20) was 1.46. Production of Optical Laminate (20) An optical laminate (20) having a configuration of retardation film 1 / adhesive layer (20) / retardation film 2 was obtained in the same manner as in Example 1, except that instead of applying the adhesive (1) to a coating thickness of 1 μm, the adhesive (20) was applied to a coating thickness of 1 μm. The results are shown in Table 1.

[0137] Example 21 Preparation of Adhesive (21) Adhesive (21) was prepared in the same manner as in Example 18, except that a mixed solvent of ethanol:water = 49.5:50.5 (weight ratio) was used instead of methanol as the solvent. The refractive index of the adhesive layer formed from adhesive (21) was 1.46. Production of Optical Laminate (21) An optical laminate (21) having a configuration of retardation film 1 / adhesive layer (21) / retardation film 2 was obtained in the same manner as in Example 1, except that adhesive (21) was applied to a coating thickness of 1 μm instead of applying adhesive (1) to a coating thickness of 1 μm. The results are shown in Table 1.

[0138] [Example 22] <Preparation of adhesive (22)> The same procedure as in Example 18 was carried out to prepare adhesive (22), except that a mixed solvent of ethanol:water = 19.2:80.8 (weight ratio) was used instead of methanol as the solvent. The refractive index of the adhesive layer formed from adhesive (22) was 1.46. <Production of optical laminate (22)> The same procedure as in Example 1 was carried out, except that instead of applying adhesive (1) to a coating thickness of 1 μm, adhesive (22) was applied to a coating thickness of 1 μm, and an optical laminate (22) having a configuration of retardation film 1 / adhesive layer (22) / retardation film 2 was obtained. The results are shown in Table 1.

[0139] [Example 23] <Preparation of adhesive (23)> An adhesive (23) was prepared in the same manner as in Example 1, except that no surfactant was added. The refractive index of the adhesive layer formed from the adhesive (23) was 1.46. <Production of optical laminate (23)> An optical laminate (23) having a configuration of retardation film 1 / adhesive layer (2) / retardation film 2 was obtained in the same manner as in Example 1, except that instead of applying the adhesive (1) to a coating thickness of 1 μm, the adhesive (23) was applied to a coating thickness of 1 μm. The results are shown in Table 1.

[0140] Comparative Example 1 Preparation of Adhesive (C1) An aqueous solution was prepared by blending an epoxy silane coupling agent (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") with water as a solvent to obtain a 1.0 wt% aqueous solution. 0.2 parts by weight of a surfactant (manufactured by Nissin Chemical Industry Co., Ltd., product name "EXP4200") was added to 100 parts by weight of the resulting aqueous solution to prepare adhesive (C1). The refractive index of the adhesive layer formed from adhesive (C1) was 1.47. Production of Optical Laminate (C1) The same procedure as in Example 1 was carried out, except that instead of applying adhesive (1) to a coating thickness of 1 μm, adhesive (C1) was applied to a coating thickness of 1 μm, and an optical laminate (C1) having a configuration of retardation film 1 / adhesive layer (C1) / retardation film 2 was obtained. The results are shown in Table 1.

[0141] Comparative Example 2 Preparation of Adhesive (C2) Adhesive (C2) was prepared in the same manner as in Example 18, except that isopropanol was used as the solvent instead of methanol. The refractive index of the adhesive layer formed from adhesive (C2) was 1.46. Production of Optical Laminate (C2) An optical laminate (C2) having a configuration of retardation film 1 / adhesive layer (C2) / retardation film 2 was obtained in the same manner as in Example 1, except that adhesive (C2) was applied to a coating thickness of 1 μm instead of adhesive (1) being applied to a coating thickness of 1 μm. The results are shown in Table 1.

[0142] Comparative Example 3 Preparation of Adhesive (C3) An adhesive (C3) was prepared in the same manner as in Example 18, except that butanol was used instead of methanol as the solvent. Production of Optical Laminate (C3) An optical laminate (C3) having a configuration of retardation film 1 / adhesive layer (C3) / retardation film 2 was obtained in the same manner as in Example 1, except that adhesive (C3) was applied to a coating thickness of 1 μm instead of adhesive (1) being applied to a coating thickness of 1 μm. The results are shown in Table 1.

[0143] Comparative Example 4 Preparation of Adhesive (C4) Adhesive (C4) was prepared in the same manner as in Example 18, except that diacetone was used instead of methanol as the solvent. Production of Optical Laminate (C4) An optical laminate (C4) having a configuration of retardation film 1 / adhesive layer (C4) / retardation film 2 was obtained in the same manner as in Example 18, except that adhesive (C4) was applied to a coating thickness of 1 μm instead of applying adhesive (1) to a coating thickness of 1 μm. The results are shown in Table 1.

[0144] Comparative Example 5 Preparation of Adhesive (C5) Adhesive (C5) was prepared in the same manner as in Example 1, except that the total concentration of the amino compound (A) and the epoxy compound (B) was adjusted to a 20.0 wt % aqueous solution. Production of Optical Laminate (C5) The same procedure was followed as in Example 1, except that instead of applying adhesive (1) to a coating thickness of 1 μm, adhesive (C5) was applied to a coating thickness of 0.25 μm. However, when applied to a coating thickness of 0.25 μm, the solution dried during transport, resulting in a laminate containing bubbles over the entire surface. The results are shown in Table 1.

[0145]

[0146] The adhesive and optical laminate according to the embodiment of the present invention can be used in any suitable application, and can be suitably used, for example, in image display devices such as liquid crystal display devices and organic EL display devices.

Claims

1. An adhesive used for attaching optical films, the adhesive being a solution containing an amino compound (A) and a solvent (C), the content of the amino compound (A) relative to the total of the amino compound (A) and the solvent (C) being 0.01% by weight or more but less than 10% by weight, and the solvent (C) containing at least one solvent selected from the group consisting of water and alcohols having 2 or less carbon atoms.

2. The adhesive according to claim 1, wherein the content of said solvent (C) in said solution is 80% by weight to 99.9% by weight.

3. The adhesive according to claim 1, wherein the content of at least one member selected from the group consisting of water and alcohols having 2 or less carbon atoms in the solvent (C) is 50% by weight to 100% by weight.

4. The adhesive according to claim 1, wherein the amino compound (A) is an amino-silane coupling agent.

5. The adhesive of claim 1, wherein the adhesive comprises an epoxy compound (B).

6. The adhesive according to claim 5, wherein the total content of the amino compound (A) and the epoxy compound (B) relative to the total of the amino compound (A), the epoxy compound (B), and the solvent (C) is more than 0.01% by weight and less than 20% by weight.

7. The adhesive according to claim 5, wherein the content ratio of the amino compound (A) to the epoxy compound (B) is 6:94 to 90:10 in terms of molar ratio.

8. An optical laminate in which a first light-transmitting optical film and a second light-transmitting optical film are bonded together with an adhesive layer formed from the adhesive according to any one of claims 1 to 7.

9. The optical laminate according to claim 8, wherein the adhesive layer has a thickness of 50 nm or less.

10. The optical laminate according to claim 9, wherein the adhesive layer has a thickness of less than 30 nm.

11. The optical laminate according to claim 8, wherein the difference in in-plane refractive index between said first light-transmitting optical film and said adhesive layer is 0.05 or more.

12. The optical laminate according to claim 8, wherein the in-plane refractive index of the first light-transmitting optical film is 1.50 or more.

13. The optical laminate according to claim 8, wherein the difference in in-plane refractive index between the second light-transmitting optical film and the adhesive layer is 0.05 or more.

14. The optical laminate according to claim 8, wherein the in-plane refractive index of the second light-transmitting optical film is 1.50 or more.

15. The optical laminate according to claim 8, wherein at least one of the first light-transmitting optical film and the second light-transmitting optical film is a retardation film.

16. The optical laminate according to claim 8, wherein the adhesive layer comprises an organosilicon compound.

17. An image display device comprising the optical laminate according to claim 8.

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