Optical laminate, method for manufacturing same, and method for manufacturing optical member using said optical laminate

Abstract

Provided is an optical laminate which includes a low refractive index layer, exhibits sufficient strength to inhibit exfoliation between a light guiding plate and the low refractive index layer, is capable of realizing an optical member having excellent light guiding performance, and is capable of inhibiting cracks, contamination, deformation, and damage in the low refractive index layer even when being wound around in a rolled state. The optical laminate according to an embodiment of the present invention comprises: a first base material which has a tensile elastic modulus of 20 MPa or more; a low refractive index layer which is provided on one main surface of the first base material; a stress relaxation layer which is provided on the low refractive index layer on the side opposite to the first base material and has a storage elastic modulus of 0.01-10 MPa; and a second base material which is provided on the stress relaxation layer on the side opposite to the low refractive index layer and has a tensile elastic modulus of 20 MPa or more. The exfoliation strength between the low refractive index layer and the first base material is 0.5 N / 25 mm or less.

Description

Optical laminate, manufacturing method thereof, and manufacturing method of optical member using said optical laminate

[0001] The present invention relates to an optical laminate, a method for producing the same, and a method for producing an optical member using the optical laminate.

[0002] A technology is known in which a low-refractive index layer is formed on a light guide plate to optically isolate the light guided through the light guide plate and minimize the influence of external factors (e.g., scratches and dirt on the light guide plate). For example, an optical sheet is known in which a low-refractive index layer is laminated on a light guide plate via an adhesive layer. This technology can cause color shift and / or scattering due to the adhesive layer, resulting in light guide loss. To solve this problem, a technology has been developed in which a low-refractive index layer is directly laminated on a light guide plate. However, when a low-refractive index layer is directly laminated on a light guide plate, the low strength of the low-refractive index layer results in a problem in that the strength of the laminate is also low.

[0003] Furthermore, in the production of optical components including a low refractive index layer, problems may arise such as scratches or contamination of the low refractive index layer when an intermediate including the low refractive index layer is wound into a roll, and deformation and / or damage of the low refractive index layer due to tight winding.

[0004] Japanese Patent No. 6606518 JP 2023-048451 A

[0005] The present invention has been made to solve the above-mentioned conventional problems, and its main object is to provide an optical laminate including a low refractive index layer, which has sufficient strength as a laminate and can realize an optical component with excellent light-guiding performance, and further, can suppress scratches, contamination, deformation, and breakage of the low refractive index layer even when wound into a roll.

[0006] [1] An optical laminate according to an embodiment of the present invention comprises: a first substrate having a tensile modulus of elasticity of 20 MPa or more; a low refractive index layer provided on one main surface of the first substrate; a stress relief layer having a storage modulus of elasticity of 0.01 MPa to 10 MPa provided on the side of the low refractive index layer opposite the first substrate; and a second substrate having a tensile modulus of elasticity of 20 MPa or more provided on the side of the stress relief layer opposite the low refractive index layer; wherein the peel force between the low refractive index layer and the first substrate is 0.5 N / 25 mm or less. [2] In the above [1], the surface roughness Rz of the low refractive index layer on the first substrate side is 50 nm or less. [3] In the above [1] or [2], the first substrate has, in order from the low refractive index layer side, a first resin layer and a second resin layer. [4] In the above [3], the first resin layer contains a cycloolefin-based resin, and the second resin layer contains a polyester-based resin. [5] In any of [1] to [4] above, the refractive index of the low refractive index layer is 1.25 or less. [6] In any of [1] to [5] above, the thickness of the low refractive index layer is 5 μm or less. [7] In any of [1] to [6] above, the haze of the low refractive index layer is less than 5%. [8] In any of [1] to [7] above, the storage modulus of the stress relaxation layer is 0.08 MPa to 0.20 MPa and the thickness is 5 μm to 20 μm. [9] In any of [1] to [8] above, the optical laminate is long and can be wound into a roll.

[10] According to another aspect of the present invention, there is provided a method for producing the optical laminate of any of [1] to [9] above. The production method includes the steps of forming a low refractive index layer on a first substrate to produce a first laminate; and providing a pressure-sensitive adhesive layer and a second substrate in this order on the low refractive index layer of the first laminate.

[11] In the above

[10] , the manufacturing method further includes winding the obtained optical laminate into a roll.

[12] According to yet another aspect of the present invention, there is provided a method for manufacturing an optical member. The manufacturing method includes the steps of: unwinding the roll-shaped optical laminate obtained by the manufacturing method of above

[11] ; peeling the first substrate from the optical laminate; and laminating the optical laminate from which the first substrate has been peeled and a light guide plate so that the low refractive index layer and the light guide plate are adjacent to each other.

[0007] According to an embodiment of the present invention, an optical laminate including a low refractive index layer can be realized, which has sufficient strength as a laminate and has excellent light-guiding performance, and further, an optical laminate can be realized in which scratches, contamination, deformation, and breakage of the low refractive index layer can be suppressed even when wound into a roll.

[0008] FIG. 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention; FIG. 2 is a schematic cross-sectional view illustrating one step in a method for manufacturing an optical laminate according to an embodiment of the present invention; FIG. 3 is a schematic cross-sectional view illustrating another step in a method for manufacturing an optical laminate according to an embodiment of the present invention; FIG. 4 is a schematic cross-sectional view illustrating yet another step in a method for manufacturing an optical laminate according to an embodiment of the present invention; FIG. 5 is a schematic cross-sectional view illustrating one step in a method for manufacturing an optical member using the optical laminate according to an embodiment of the present invention; FIG. 6 is a schematic cross-sectional view illustrating another step in a method for manufacturing an optical member using the optical laminate according to an embodiment of the present invention.

[0009] The present invention will be described below with reference to exemplary embodiments, but is not limited to these. For clarity, the drawings are schematic, and the thicknesses and sizes of the components of the optical member and the ratios of the thicknesses of the components to each other may differ from the actual figures.

[0010] A. Overall Configuration of the Optical Laminate Figure 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. The illustrated optical element 100 includes a first substrate 60, a low-refractive index layer 20 provided on one major surface of the first substrate 60 (the upper major surface in the illustrated example), a stress relief layer 30 provided on the side of the low-refractive index layer 20 opposite the first substrate 60, and a second substrate 40 provided on the side of the stress relief layer 30 opposite the low-refractive index layer 20. In an embodiment of the present invention, the storage modulus of the stress relief layer is 0.01 MPa to 10 MPa, the tensile moduli of the first substrate and the second substrate are each 20 MPa or more, and the peel force between the low-refractive index layer and the first substrate is 0.5 N / 25 mm or less. With this configuration, an optical element in which a low-refractive index layer is laminated on a light guide plate without the use of an adhesive or pressure-sensitive adhesive can be realized. The optical element has sufficient strength to suppress peeling between the light guide plate and the low-refractive index layer and has excellent light-guiding performance. That is, the optical laminate according to an embodiment of the present invention can be an intermediate for such an optical element. More specifically, the optical element can be obtained by peeling off the first substrate from the optical laminate and then laminating the low-refractive-index layer side of the optical laminate from which the first substrate has been peeled off onto a light guide plate without using any adhesive or pressure-sensitive adhesive. By including a stress relief layer having the above-described storage modulus adjacent to the low-refractive-index layer (on the side opposite the light guide plate in the resulting optical element), the strength of the resulting optical element as a laminate can be ensured. This configuration can further suppress scratches, contamination, deformation, and breakage of the low-refractive-index layer even when the optical laminate is wound into a roll, and can achieve excellent light-guiding performance in the resulting optical element. Furthermore, by including a stress relief layer on one side of the low-refractive-index layer and a first substrate on the other side of the optical laminate, exposure of the low-refractive-index layer is prevented, thereby suppressing scratches, contamination, deformation, and breakage of the low-refractive-index layer during transportation. Additionally, by having the peel strength between the low-refractive-index layer and the first substrate within the above-described range, peel failures during peeling of the first substrate can be suppressed. Due to the above synergistic effect, the optical laminate (the low refractive index layer side) from which the first substrate has been peeled off can be laminated to a light guide plate without the use of an adhesive or pressure-sensitive adhesive.An optical member in which a low refractive index layer is laminated on a light guide plate without the use of an adhesive or pressure-sensitive adhesive can suppress color shift and / or scattering caused by pressure-sensitive adhesives, etc., thereby suppressing light guide loss and achieving excellent light guide performance. Therefore, an optical member obtained using the optical laminate according to an embodiment of the present invention can have sufficient strength as a laminate and excellent light guide performance.

[0011] The total light transmittance of the optical laminate is preferably 60% or more and 99% or less, more preferably 70% or more and 98% or less, and even more preferably 80% or more and 97% or less. The haze of the optical laminate is preferably 0.05% or more and 3% or less, more preferably 0.1% or more and 2.5% or less, and even more preferably 0.2% or more and 2% or less. According to an embodiment of the present invention, excellent transparency can be achieved for the entire optical laminate. As a result, optical elements obtained using such optical laminates can be suitably used for AR glasses, MR glasses, and VR glasses (hereinafter, these may be collectively referred to as "AR glasses, etc."). "AR" is an abbreviation for "Augmented Reality," "MR" is an abbreviation for "Mixed Reality," and "VR" is an abbreviation for "Virtual Reality."

[0012] The thickness of the optical laminate is preferably 30 μm to 450 μm, more preferably 35 μm to 400 μm, and even more preferably 40 μm to 350 μm. In this specification, the "thickness of the optical laminate" means the total thickness from one outermost layer to the other outermost layer of the optical laminate. For example, in the embodiment of FIG. 1, the thickness of the optical laminate is the thickness from the outer (upper) surface of the second substrate to the outer (lower) surface of the second substrate.

[0013] The optical laminate may be in a long shape or in a sheet shape. A long optical laminate can typically be wound into a roll. According to an embodiment of the present invention, even when the optical laminate is wound into a roll, scratches, contamination, deformation, and breakage of the low refractive index layer can be suppressed.

[0014] The components of the optical member will be described in detail below.

[0015] B. First Substrate As described above, the tensile modulus of the first substrate 60 is 20 MPa or more, preferably 30 MPa or more, more preferably 50 MPa or more, even more preferably 100 MPa or more, and particularly preferably 300 MPa or more. On the other hand, the tensile modulus of the first substrate is preferably 10 GPa or less, more preferably 8 GPa or less, and even more preferably 6 GPa or less. If the tensile modulus of the first substrate is within this range, damage to the low refractive index layer can be suppressed.

[0016] As described above, the peel strength between the first substrate and the low refractive index layer is 0.5 N / 25 mm or less, preferably 0.4 N / 25 mm or less, more preferably 0.3 N / 25 mm or less, even more preferably 0.2 N / 25 mm or less, and particularly preferably 0.15 N / 25 mm or less. Meanwhile, the peel strength may be, for example, 0.01 N / 25 mm or more, or, for example, 0.02 N / 25 mm or more. When the peel strength between the first substrate and the low refractive index layer is within this range, the resulting optical laminate (intermediate) may have a strength suitable for producing an optical component as a final product. Furthermore, peeling defects during peeling of the first substrate are suppressed, and the exposed low refractive index layer is suppressed from scratches, contamination, deformation, and breakage.

[0017] The glass transition temperature (Tg) of the first substrate is preferably 20° C. or higher, more preferably 40° C. or higher, even more preferably 60° C. or higher, and particularly preferably 70° C. or higher. On the other hand, the Tg of the first substrate may be, for example, 250° C. or lower. If the Tg of the first substrate is in this range, damage to the low refractive index layer can be suppressed, similar to the effect achieved by setting the tensile modulus within the above range.

[0018] The first substrate may have any suitable structure as long as it has the above-described properties. For example, the first substrate may be a single resin film or a laminated film including two or more resin layers.

[0019] When the first substrate is a single resin film, the first substrate can be composed of any appropriate resin film. Examples of materials for forming the resin film include (meth)acrylic resins, cellulose resins such as diacetyl cellulose and triacetyl cellulose, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyester resins such as polyethylene terephthalate resins, polyamide resins, polycarbonate resins, and copolymer resins thereof. (Meth)acrylic resins or polyester resins are preferred. The term "(meth)acrylic resin" refers to acrylic resins and / or methacrylic resins.

[0020] The thickness of the first substrate may be, for example, 10 μm to 200 μm. If the thickness of the first substrate is in this range, damage to the low refractive index layer can be suppressed. Furthermore, the optical laminate can be given a strength appropriate for producing an optical component as a final product.

[0021] When the first substrate is a laminate film containing two or more resin layers, the first substrate typically has a first resin layer and a second resin layer in this order from the low refractive index layer side. The first resin layer is typically a solidified layer of a coating film of a resin solution; the second resin layer typically has the same structure as when the first substrate is a single resin film. In one embodiment, the first resin layer contains a cycloolefin-based resin, and the second resin layer contains a polyester-based resin. With this structure, the strength of the optical laminate and the peelability of the first substrate can be further improved.

[0022] C. Low Refractive Index Layer The low refractive index layer 20 typically has voids therein. The porosity of the low refractive index layer is preferably 35 vol% or more, more preferably 38 vol% or more, and particularly preferably 40 vol% or more. If the porosity is within this range, a low refractive index layer with a particularly low refractive index can be formed. The upper limit of the porosity of the low refractive index layer is, for example, 90 vol% or less, preferably 75 vol% or less. If the porosity is within this range, a low refractive index layer with excellent strength can be formed. The porosity is a value calculated from the refractive index measured with an ellipsometer using the Lorentz-Lorenz formula.

[0023] The refractive index of the low-refractive index layer is, for example, 1.25 or less, preferably 1.23 or less, more preferably 1.22 or less, even more preferably 1.20 or less, and particularly preferably 1.19 or less. On the other hand, the refractive index of the low-refractive index layer is preferably 1.05 or more, more preferably 1.08 or more, and even more preferably 1.10 or more. By providing a low-refractive index layer having such a refractive index on the main surface of the light guide plate, light guide loss can be suppressed without substantially affecting the optical properties of the light guide plate, thereby achieving excellent light guide performance. Furthermore, as described below, the low-refractive index layer can be made very thin, which can contribute to reducing the thickness and weight of optical components (e.g., AR glass). Furthermore, if the refractive index of the low-refractive index layer is within the above range, a predetermined mechanical strength can be ensured and breakage can be suppressed. Unless otherwise specified, the refractive index refers to the refractive index measured at a wavelength of 550 nm or the refractive index converted to a 550 nm value from measurements at other wavelengths and the refractive index wavelength dispersion. The refractive index is a value measured by the method described in "(1) Refractive Index of the Low-Refractive Index Layer" in the Examples section below.

[0024] The total light transmittance of the low refractive index layer is preferably 85% to 99%, more preferably 87% to 98%, and even more preferably 89% to 97%. By providing a low refractive index layer having such a refractive index on the main surface of the light guide plate, it is possible to ensure excellent transparency while achieving the effects of the refractive index. As a result, the optical member can be suitably used in AR glasses and the like.

[0025] The haze of the low refractive index layer is, for example, less than 5%, preferably less than 3%. On the other hand, the haze is, for example, 0.05% or more, preferably 0.1% or more. By providing a low refractive index layer having such a haze on the main surface of a light guide plate, it is possible to ensure excellent transparency while achieving the effects of the refractive index described above. As a result, the optical element can be suitably used in AR glass, etc. Haze can be measured, for example, by the following method. A low refractive index layer is formed on a 50 mm x 50 mm piece of glass, and the haze is measured by setting it in a haze meter (HM-150, manufactured by Murakami Color Research Laboratory Co., Ltd.). The haze value is calculated using the following formula: Haze (%) = [Diffuse transmittance (%) / Total light transmittance (%)] x 100 (%)

[0026] The thickness of the low refractive index layer is preferably 5 μm or less, more preferably 4 μm or less, even more preferably 3 μm or less, particularly preferably 2 μm or less, and particularly preferably 1.5 μm or less. On the other hand, the thickness of the low refractive index layer is preferably 300 nm or more, more preferably 400 nm or more, and even more preferably 500 nm or more. If the thickness of the low refractive index layer is in this range, it is possible to effectively suppress light leakage while ensuring excellent transparency.

[0027] The surface roughness Rz of the low refractive index layer on the first substrate side is preferably 200 nm or less, more preferably 100 nm or less, and even more preferably 50 nm or less. Since the surface roughness of the first substrate that comes into contact with the low refractive index layer is transferred almost directly, the surface roughness can be determined when the low refractive index layer-forming material is applied to the first substrate. If the surface roughness Rz of the low refractive index layer is within this range, sufficient adhesion between the low refractive index layer and the light guide plate can be ensured in the method for manufacturing an optical element described below. As a result, the first substrate can be properly peeled off without damaging the low refractive index layer. Rz refers to the maximum height based on JIS B 0601.

[0028] The low refractive index layer may have any suitable configuration as long as it has the desired properties. The low refractive index layer may be preferably formed by coating, printing, or the like. Materials for the low refractive index layer include those described in International Publication No. 2004 / 113966, Japanese Patent Application Laid-Open No. 2013-254183, and Japanese Patent Application Laid-Open No. 2012-189802. Representative examples include silicon compounds. Examples of silicon compounds include silica-based compounds; hydrolyzable silanes and their partial hydrolyzates and dehydration condensates; silicon compounds containing silanol groups; and activated silica obtained by contacting silicates with acids or ion exchange resins. Other examples include organic polymers; polymerizable monomers (e.g., (meth)acrylic monomers and styrene-based monomers); and curable resins (e.g., (meth)acrylic resins, fluorine-containing resins, and urethane resins). These materials may be used alone or in combination. The low refractive index layer can be formed by coating or printing a solution or dispersion of such a material.

[0029] The size of the voids (holes) in the low refractive index layer refers to the diameter of the major axis of the voids (holes). The size of the voids (holes) is, for example, 2 nm to 500 nm. The size of the voids (holes) is, for example, 2 nm or more, preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more. On the other hand, the size of the voids (holes) is, for example, 500 nm or less, preferably 200 nm or less, and more preferably 100 nm or less. The size of the voids (holes) ranges, for example, from 2 nm to 500 nm, preferably from 5 nm to 500 nm, more preferably from 10 nm to 200 nm, and even more preferably from 20 nm to 100 nm. The size of the voids (holes) can be adjusted to a desired size depending on the purpose and application. The size of the voids (holes) can be quantified using the BET test method.

[0030] The size of the voids (pores) can be quantified by the BET test method. Specifically, 0.1 g of the sample (the formed void layer) is placed in the capillary of a high-precision gas adsorption measurement device (Microtrac's BELLSORP MINI), and then dried under reduced pressure at room temperature for 24 hours to degas the gas in the void structure. Then, nitrogen gas is adsorbed onto the sample, and an adsorption isotherm is drawn to determine the pore distribution. This allows the void size to be evaluated.

[0031] Examples of the low refractive index layer having voids therein include a low refractive index layer and / or a low refractive index layer having an air layer at least in a part thereof. The low refractive index layer typically contains aerogel and / or particles (e.g., hollow fine particles and / or porous particles). The low refractive index layer is preferably a nanoporous layer (specifically, a layer in which 90% or more of the micropores have a diameter of 10 －１ nm to 10 ３ The layer may be a low refractive index layer in the range of 100 nm.

[0032] Any appropriate particles may be used as the particles. The particles are typically made of a silica-based compound. Examples of particle shapes include spherical, plate-like, needle-like, string-like, and bunch-of-grapes shapes. Examples of string-like particles include particles in which a plurality of spherical, plate-like, or needle-like particles are strung together like beads, short fiber-like particles (e.g., the short fiber-like particles described in JP 2001-188104 A), and combinations thereof. The string-like particles may be linear or branched. Examples of bunch-of-grapes-like particles include particles in which a plurality of spherical, plate-like, and needle-like particles are aggregated to form a bunch of grapes. The particle shape can be confirmed, for example, by observation with a transmission electron microscope.

[0033] An example of a specific configuration of the low refractive index layer will be described below. The low refractive index layer of this embodiment is composed of one or more types of structural units that form a fine void structure, and the structural units are chemically bonded to each other via catalytic action. Examples of the shape of the structural units include particulate, fibrous, rod-like, and flat-plate-like. The structural units may have only one shape, or may have a combination of two or more shapes. Below, we will mainly describe the case where the low refractive index layer is a porous layer in which the above-mentioned fine-pore particles are chemically bonded to each other.

[0034] Such a void layer can be formed, for example, by chemically bonding microporous particles together in the void layer forming step. In an embodiment of the present invention, the shape of the "particles" (e.g., the microporous particles) is not particularly limited and may be, for example, spherical or another shape. In an embodiment of the present invention, the microporous particles may be, for example, sol-gel beaded particles, nanoparticles (hollow nanosilica / nanoballoon particles), nanofibers, etc. The microporous particles typically include inorganic substances. Specific examples of inorganic substances include silicon (Si), magnesium (Mg), aluminum (Al), titanium (Ti), zinc (Zn), and zirconium (Zr). These may be used alone or in combination of two or more. In one embodiment, the microporous particles are, for example, microporous particles of a silicon compound, and the porous body is, for example, a silicone porous body. The microporous particles of the silicon compound include, for example, a pulverized gel silica compound. Another example of a low-refractive-index layer and / or a low-refractive-index layer having at least a partial air layer is a void layer made of a fibrous material such as nanofibers, which are entangled to form voids. The method for producing such a void layer is not particularly limited, and can be the same as that for the void layer of a porous body in which microporous particles are chemically bonded to each other. Further examples include void layers made of hollow nanoparticles or nanoclay, and void layers made of hollow nanoballoons or magnesium fluoride. The void layer may be made of a single constituent material or a plurality of constituent materials. The void layer may be made of a single constituent material or a plurality of constituent materials.

[0035] In this embodiment, the porous structure of the porous body may be, for example, an open-cell structure in which the pores are interconnected. An open-cell structure refers to, for example, the three-dimensionally interconnected pore structure of the silicone porous body, and can also be described as a state in which the internal voids of the pore structure are interconnected. Having an open-cell structure in a porous body can increase the porosity. However, when closed-cell particles (particles with individual pore structures) such as hollow silica are used, an open-cell structure cannot be formed. On the other hand, when silica sol particles (pulverized gel-like silicon compound that forms a sol) are used, the particles have a three-dimensional dendritic structure, and the dendritic particles settle and deposit in the coating film (coated film of a sol containing the pulverized gel-like silicon compound), thereby easily forming an open-cell structure. The low refractive index layer more preferably has a monolithic structure in which the open-cell structure includes a distribution of multiple pores. The monolithic structure refers, for example, to a hierarchical structure including a structure in which nano-sized voids exist and an open-cell structure in which the nano-voids are aggregated. When forming a monolithic structure, for example, by providing film strength with fine pores, and providing high porosity with coarse open-cell pores, it is possible to achieve both film strength and high porosity.Such a monolithic structure can be preferably formed by controlling the pore distribution of the pore structure produced in the gel (gel silicon compound) before being crushed into silica sol particles.In addition, for example, when crushing the gel silicon compound, by controlling the particle size distribution of the crushed silica sol particles to a desired size, it is possible to form a monolithic structure.

[0036] The low refractive index layer contains, for example, pulverized gel compounds as described above, and the pulverized compounds are chemically bonded together. The form of the chemical bond between the pulverized compounds in the low refractive index layer is not particularly limited, and examples thereof include cross-linking, covalent bonding, and hydrogen bonding.

[0037] The volume average particle diameter of the pulverized material in the low refractive index layer is, for example, 10 nm or more, preferably 20 nm or more, and more preferably 30 nm or more. On the other hand, the volume average particle diameter is, for example, 500 nm or less, preferably 400 nm or less, and more preferably 300 nm or less. The volume average particle diameter ranges, for example, from 10 nm to 500 nm, preferably from 20 nm to 400 nm, and more preferably from 30 nm to 300 nm. The particle size distribution can be measured, for example, using a particle size distribution evaluation device such as a dynamic light scattering method or a laser diffraction method, or an electron microscope such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The volume average particle diameter is an index of the particle size variation of the pulverized material; specifically, the D10, D50, and D90 indices can be used, and the D50 indices can be used as the particle size value.

[0038] The type of gel compound is not particularly limited, and examples of the gel compound include gel silicon compounds.

[0039] In the low refractive index layer (void layer), for example, it is preferable that the silicon atoms contained therein are siloxane-bonded. Specifically, the proportion of unbonded silicon atoms (i.e., residual silanols) among all silicon atoms contained in the void layer is, for example, less than 50%, preferably 30% or less, and more preferably 15% or less.

[0040] An example of a method for forming such a low refractive index layer will be described below.

[0041] This method typically includes a precursor formation step of forming a void structure on a light guide plate, which is a precursor of a low-refractive index layer (void layer), and a crosslinking reaction step of inducing a crosslinking reaction within the precursor after the precursor formation step. This method further includes a liquid-containing step of preparing a liquid containing microporous particles (hereinafter sometimes referred to as a "microporous particle-containing liquid" or simply "containing liquid") and a drying step of drying the liquid containing the microporous particles. In the precursor formation step, the microporous particles in the dried body are chemically bonded to form a precursor. The liquid containing the microporous particles is not particularly limited and may be, for example, a suspension containing microporous particles. The following description mainly focuses on the case where the microporous particles are a pulverized gel compound and the void layer is a porous body (preferably a silicone porous body) containing the pulverized gel compound. However, the low-refractive index layer can also be formed in a similar manner when the microporous particles are not a pulverized gel compound.

[0042] According to the above method, for example, a low refractive index layer (void layer) having a very low refractive index is formed. The reason for this is presumed to be as follows. However, this presumption does not limit the method for forming the low refractive index layer.

[0043] Since the above-mentioned pulverized material is obtained by pulverizing a gel silicon compound, the three-dimensional structure of the gel silicon compound before pulverization is dispersed in the three-dimensional basic structure. Furthermore, in the above-mentioned method, by applying the crushed material of the gel silicon compound to a resin film, a precursor of a porous structure based on the three-dimensional basic structure is formed. In other words, according to the above-mentioned method, a new porous structure (three-dimensional basic structure) is formed by applying the crushed material, which is different from the three-dimensional structure of the gel silicon compound. Therefore, in the finally obtained void layer, for example, a low refractive index that functions to the same extent as an air layer can be achieved. Furthermore, in the above-mentioned method, the crushed material is chemically bonded to each other, so the three-dimensional basic structure is fixed. Therefore, the finally obtained void layer can maintain sufficient strength and flexibility despite having a void structure.

[0044] The specific configuration and details of the method for forming the low refractive index layer are described in, for example, WO 2019 / 151073, the disclosure of which is incorporated herein by reference.

[0045] D. Stress Relaxation Layer As described above, by including a stress relaxation layer on the side of the low refractive index layer opposite the first substrate (ultimately, on the side opposite the light guide plate in the optical member), scratches, contamination, deformation, and breakage of the low refractive index layer can be suppressed even when the optical laminate is wound into a roll, and excellent light guide performance can be achieved in the obtained optical member.

[0046] The stress relaxation layer 30 can be typically made of an adhesive. The adhesive that makes up the stress relaxation layer typically has a hardness that does not penetrate into the voids in the low refractive index layer under normal conditions. Therefore, the storage modulus of the stress relaxation layer at 23°C is, for example, 0.01 MPa (0.1 × 10 ４ The storage modulus of the stress relaxation layer at 23°C may be 0.02 MPa or more, more preferably 0.04 MPa or more, even more preferably 0.06 MPa or more, particularly preferably 0.08 MPa or more, and especially preferably 0.10 MPa or more. When the lower limit of the storage modulus is within this range, the adverse effect of the pressure-sensitive adhesive constituting the stress relaxation layer on the low refractive index layer is suppressed, and the effect of the low refractive index layer (excellent light-guiding performance) can be well maintained. On the other hand, the storage modulus of the stress relaxation layer at 23°C is preferably 5 MPa or less, more preferably 3 MPa or less, even more preferably 1 MPa or less, particularly preferably 0.70 MPa or less, especially preferably 0.50 MPa or less, and most preferably 0.20 MPa or less. When the upper limit of the storage modulus is within this range, the stress relaxation layer has excellent durability, a buffering function (cushioning function) against external forces, and softness that can suppress peeling and / or damage of the low refractive index layer. The storage modulus is determined by reading the value at 23°C when measured at a temperature rise rate of 5°C / min in the range of -50°C to 150°C under a frequency of 1 Hz in accordance with the method described in JIS K 7244-1 "Plastics - Testing methods for dynamic mechanical properties."

[0047] The glass transition temperature (Tg) of the stress relaxation layer is preferably 0° C. or lower, more preferably −100° C. to −5° C., and even more preferably −90° C. to −10° C. If the Tg of the stress relaxation layer is within this range, a stress relaxation layer that can achieve both excellent buffering function and excellent light-guiding performance can be achieved, similar to the effect achieved by setting the storage modulus within the above range.

[0048] Any appropriate adhesive may be used as the adhesive constituting the stress relief layer as long as it has the above-described properties. A typical example of an adhesive is an acrylic adhesive (acrylic adhesive composition). An acrylic adhesive composition typically contains a (meth)acrylic polymer as the main component (base polymer). The (meth)acrylic polymer may be contained in the adhesive composition in an amount of, for example, 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more of the solid content of the adhesive composition. The (meth)acrylic polymer contains alkyl(meth)acrylate as a monomer unit as the main component. (Meth)acrylate refers to acrylate and / or methacrylate. Examples of the alkyl group of the alkyl(meth)acrylate include linear or branched alkyl groups having 1 to 18 carbon atoms. The average carbon number of the alkyl group is preferably 3 to 9. In addition to alkyl (meth)acrylates, examples of monomers constituting the (meth)acrylic polymer include comonomers such as carboxyl group-containing monomers, hydroxyl group-containing monomers, amide group-containing monomers, aromatic ring-containing (meth)acrylates, and heterocyclic ring-containing (meth)acrylates. The comonomers are preferably hydroxyl group-containing monomers and / or heterocyclic ring-containing (meth)acrylates, more preferably N-acryloylmorpholine. The acrylic pressure-sensitive adhesive composition may preferably contain a silane coupling agent and / or a crosslinking agent. Examples of silane coupling agents include epoxy group-containing silane coupling agents. Examples of crosslinking agents include isocyanate-based crosslinking agents and peroxide-based crosslinking agents. Details of such stress relaxation layers or acrylic pressure-sensitive adhesive compositions are described, for example, in Japanese Patent No. 4,140,736, the disclosure of which is incorporated herein by reference.

[0049] The thickness of the stress relaxation layer can vary depending on the storage modulus. That is, in consideration of the buffer function (cushion function) against external forces, a larger thickness is preferable; in consideration of light guiding performance, a smaller thickness is preferable; and if the stress relaxation layer has a small storage modulus (is softer), the thickness can be relatively small. Taking these factors into consideration comprehensively, the thickness of the stress relaxation layer is, for example, 1 μm to 50 μm, preferably 2 μm to 40 μm, more preferably 3 μm to 30 μm, even more preferably 4 μm to 20 μm, particularly preferably 5 μm to 15 μm, and especially preferably 6 μm to 12 μm. If the thickness is within this range, a stress relaxation layer that can achieve both excellent buffer function and excellent light guiding performance can be realized. In this case, the storage modulus of the stress relaxation layer at 23°C may be, for example, 0.08 MPa to 0.20 MPa, or may be, for example, 0.09 MPa to 0.18 MPa, or may be, for example, 0.10 MPa to 0.15 MPa, or may be, for example, 0.12 MPa to 0.14 MPa.

[0050] E. Second Substrate The tensile modulus and Tg of the second substrate 40 are as described for the first substrate in Section B. The constituent material of the second substrate is as described for the first substrate in Section B when the first substrate is a single resin film.

[0051] The thickness of the second substrate may be, for example, 3 μm to 200 μm. If the thickness of the second substrate is within this range, damage to the low refractive index layer can be suppressed. Furthermore, the optical laminate can be imparted with strength appropriate for producing an optical component as a final product. The thickness of the second substrate may vary depending on the purpose, constituent materials, etc. The thickness of the second substrate may be, for example, 5 μm to 190 μm, or, for example, 10 μm to 150 μm, or, for example, 15 μm to 130 μm, or, for example, 20 μm to 100 μm.

[0052] A hard coat layer and / or an anti-reflection layer may be provided on the side of the second substrate opposite the stress relaxation layer. By providing a hard coat layer, damage to the low refractive index layer can be further suppressed. The hard coat layer preferably has a pencil hardness of H or higher, more preferably 2H or higher, and even more preferably 3H or higher. Meanwhile, the pencil hardness of the hard coat layer is preferably 6H or lower, more preferably 5H or lower. The pencil hardness can be measured based on the "Pencil Hardness Test" of JIS K 5400. The thickness of the hard coat layer may be, for example, 0.5 μm to 30 μm, or may be, for example, 1 μm to 20 μm, or may be, for example, 2 μm to 15 μm. Details of the hard coat layer are described, for example, in JP 2011-237789 A and JP 2016-224443 A. The disclosures of these publications are incorporated herein by reference.

[0053] Any appropriate configuration can be adopted for the antireflection layer. Representative configurations of the antireflection layer include: (1) a single layer of a low-refractive index layer having an optical film thickness of 120 nm to 140 nm and a refractive index of approximately 1.35 to 1.55; (2) a laminate having, from the light guide plate side, a medium-refractive index layer, a high-refractive index layer, and a low-refractive index layer; and (3) an alternating multilayer laminate of high-refractive index layers and low-refractive index layers. The thickness of such an antireflection layer is, for example, approximately 5 nm to 300 nm. The antireflection layer may be a cured layer of a non-ionizing radiation-curable resin composition. The thickness of such an antireflection layer may be, for example, 1.0 μm to 20 μm, or, for example, 2.0 μm to 10 μm, or, for example, 3.0 μm to 7.0 μm. Since the constituent materials and formation methods of the antireflection layer are well known in the art, detailed description thereof will be omitted.

[0054] F. Method for Producing an Optical Laminate According to an embodiment of the present invention, a method for producing the above-mentioned optical laminate is provided. The production method includes the steps of forming a low refractive index layer on a first substrate to produce a first laminate; and providing a pressure-sensitive adhesive layer and a second substrate, in this order, on the low refractive index layer of the first laminate. Each step will be described in detail below with reference to Figures 2A to 2C (Figure 2B is the same as Figure 1). Note that the lamination in each step may be performed by roll-to-roll, or may be performed in a batch format such as roll-to-sheet or sheet-to-sheet.

[0055] F-1. First laminate fabrication step First, as shown in Fig. 2A, a low refractive index layer 20 is formed on a first substrate 60 to fabricate a first laminate. The low refractive index layer can be formed by coating or printing a solution or dispersion of the material for forming the low refractive index layer described in Section C above, and drying the coated or printed film.

[0056] F-2. Optical Laminate Fabrication Step Next, as shown in FIG. 2B, a stress relief layer 30 and a second substrate 40 are sequentially laminated on the low refractive index layer 20 of the first laminate to fabricate an optical laminate. The stress relief layer 30 is typically formed on any suitable substrate and then transferred to the first laminate (substantially the low refractive index layer). The second substrate 40 is bonded to the first laminate via the stress relief layer 30. Alternatively, as shown in FIG. 2C, a stress relief layer 30 may be formed on the second substrate 40 to fabricate a second laminate, and the first and second laminates may be laminated via the stress relief layer 30 to fabricate an optical laminate as shown in FIG. 2B.

[0057] In any of the above embodiments, the lamination of the stress relief layer or the second laminate onto the first laminate can preferably be performed continuously from the production of the first laminate. In other words, the production of the optical laminate can be performed without first winding up the first laminate into a roll. This configuration can prevent scratches or contamination of the low refractive index layer when winding up the first laminate into a roll, and deformation and / or damage to the low refractive index layer due to tight winding.

[0058] The obtained optical laminate can be wound into a roll as needed. The rolled optical laminate can be used for producing an optical member as described below, can be stored, or can be shipped to a manufacturer of optical members.

[0059] F-3. Fabrication of Optical Member As described above, the optical laminate according to the embodiment of the present invention can be an intermediate for an optical member including a low refractive index layer and a light guide plate. Therefore, the optical member can be fabricated using the optical laminate obtained above. Fabrication of the optical member will be described below with reference to FIGS. 2D and 2E. In fabricating the optical member, lamination in each step can also be typically performed by roll-to-roll.

[0060] 2D , the first substrate 60 is peeled from the optical laminate. The peeling of the first substrate can be performed by any appropriate means. As described above, the first substrate and the low refractive index layer are configured to have an appropriate peel strength, so that peeling failure can be significantly suppressed.

[0061] Furthermore, the optical laminate from which the first substrate 60 has been peeled is laminated on the light guide plate 10 to produce an optical member. The optical laminate and the light guide plate are typically laminated directly. In this specification, "direct lamination" means that two components (here, the optical laminate and the light guide plate) are laminated without an adhesive or pressure-sensitive adhesive layer. Here, "direct lamination" also includes a case in which the optical laminate (substantially the low refractive index layer 20) is laminated on the light guide plate 10 via an adhesion auxiliary layer 50, as in the illustrated example. In either case, lamination can be performed under pressure. The pressure during lamination can be, for example, 0.008 MPa to 5 MPa. When an adhesion auxiliary layer is used, a solution in which a silane coupling agent is dissolved in an appropriate solvent (e.g., isopropyl alcohol, water, or a mixture thereof) is applied to the surface of the light guide plate, and the low refractive index layer is laminated and then dried, thereby forming the adhesion auxiliary layer and adhering the light guide plate and the low refractive index layer to each other. The drying temperature may be, for example, 35°C to 150°C; the drying time may be, for example, 0.5 minutes to 24 hours. The adhesion aid layer itself after drying (formation) has no adhesive or pressure-sensitive adhesive function, but it can assist and / or promote adhesion between the light guide plate and the low refractive index layer when the applied film of the solution dries. Since the adhesion aid layer itself has no adhesive or pressure-sensitive adhesive function, lamination via the adhesion aid layer can also be included in "direct lamination." In addition, in the obtained optical component, the second substrate 40 can function as a protective layer.

[0062] F-4. Light Guide Plate and Adhesion Aid Layer Used in Optical Components F-4-1. Light Guide Plate A light guide plate 10 is typically configured so that light incident on the light guide plate propagates through the light guide plate using total reflection and exits at a predetermined position in a predetermined direction. The light guide plate may be made of glass or resin. Examples of resins include thermoplastic resins and reactive resins (e.g., non-ionizing radiation-curable resins such as ultraviolet light, visible light, and infrared light). Examples of thermoplastic resins include COC resins and COP resins such as cyclic olefin copolymers and cycloolefin resins, acrylic resins such as polymethyl methacrylate (PMMA), styrene resins, polycarbonate (PC) resins, polyethylene terephthalate (PET) resins, resins containing one or more of the following as their main components, and transparent polyimide resins. Examples of reactive resins include non-ionizing radiation-curable resins such as acrylic, epoxy, urethane, silicone, and enethiol.

[0063] The refractive index of the light guide plate is preferably 1.4 to 2.5, more preferably 1.5 to 2.4, and even more preferably 1.6 to 2.3. If the refractive index is within this range, good light incidence from the outside, good light emission to the outside, and good total reflection inside the light guide plate can be achieved.

[0064] F-4-2. Adhesion Auxiliary Layer The adhesion auxiliary layer 50 typically contains a silane coupling agent. Examples of silane coupling agents include acrylic silane coupling agents, amino silane coupling agents, epoxy silane coupling agents, and mercapto silane coupling agents. The silane coupling agents may be used alone or in combination of two or more. In one embodiment, the silane coupling agent includes an acrylic silane coupling agent, and may include, for example, a combination of an acrylic silane coupling agent with an amino silane coupling agent, an epoxy silane coupling agent, a mercapto silane coupling agent, or a combination thereof (another silane coupling agent). The acrylic silane coupling agent and the other silane coupling agent may each be used alone or in combination of two or more. By providing an adhesion auxiliary layer containing a silane coupling agent, even greater strength can be achieved without impairing the light-guiding performance of the optical component.

[0065] The acrylic silane coupling agent is typically a silane coupling agent having a (meth)acrylic group in its skeleton. Examples of the acrylic silane coupling agent include 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, methacryloxymethyltrimethoxysilane, methacryloxymethyltriethoxysilane, acryloxymethyltrimethoxysilane, acryloxymethyltriethoxysilane, and 3-methacryloxypropylmethyldimethoxysilane. Furthermore, many acrylic silane coupling agent products are commercially available. Specific examples of commercially available products include KBM-502 and KBM-5103 manufactured by Shin-Etsu Chemical Co., Ltd. Preferably, 3-acryloxypropyltrimethoxysilane or 3-methacryloxypropylmethyldimethoxysilane is used.

[0066] Examples of amino-based silane coupling agents include γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, γ-phenylaminopropyltrimethoxysilane, and 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine. Furthermore, many amino-based silane coupling agents are commercially available. Specific examples of commercially available products include KBM-903, KBE-9103, KBM-575, and KBM-6123 manufactured by Shin-Etsu Chemical Co., Ltd., and A-1102, A-1122, and A-1170 manufactured by Momentive Performance Materials Japan, Inc. Preferably, it is 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine.

[0067] Examples of epoxy-based silane coupling agents include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltriethoxysilane, and γ-glycidoxypropylmethyldimethoxysilane. Furthermore, many epoxy-based silane coupling agent products are commercially available. Specific examples of commercially available products include KBM-402 and KBM-403 manufactured by Shin-Etsu Chemical Co., Ltd. Preferably, γ-glycidoxypropylmethyldimethoxysilane is used.

[0068] Examples of mercapto-based silane coupling agents include γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropylmethyldimethoxysilane, and γ-mercaptopropylmethyldiethoxysilane. Furthermore, many mercapto-based silane coupling agents are commercially available. A specific example of a commercially available product is X-12-1056ES manufactured by Shin-Etsu Chemical Co., Ltd.

[0069] When an acrylic silane coupling agent and another silane coupling agent are used in combination, the content ratio of the acrylic silane coupling agent to the other silane coupling agent, relative to the total amount of the silane coupling agents taken as 100, is preferably 40 / 60 to 60 / 40, more preferably 45 / 55 to 55 / 45, even more preferably 47 / 53 to 53 / 47, and particularly preferably about 50 / 50.

[0070] The thinner the thickness of the adhesion aid layer, the better, as long as it has the function of assisting adhesion between the light guide plate and the low refractive index layer. This is because adverse effects on light guide performance are minimized. Specifically, the thickness of the adhesion aid layer is preferably 500 nm or less, more preferably 100 nm or less, even more preferably 50 nm or less, particularly preferably 10 nm or less, particularly preferably 5 nm or less, and most preferably 4 nm or less. The thickness of the adhesion aid layer may be, for example, 0.5 nm or more, or may be, for example, 0.7 nm or more. The thickness of the adhesion aid layer may be, for example, 0.8 nm to 3.5 nm, or may be, for example, 0.9 nm to 3 nm. If the thickness of the adhesion aid layer is very small (for example, 3 nm or less), it may not be clearly recognized as a layer.

[0071] As described above, the adhesion aid layer can be formed by applying a solution of a silane coupling agent (silane compound) dissolved in an appropriate solvent (e.g., water or isopropyl alcohol) to the surface of a light guide plate, laminating a low refractive index layer, and then drying the applied solution. As described above, the adhesion aid layer after drying (formation) does not have an adhesive or pressure-sensitive adhesive function, but can assist and / or promote adhesion between the light guide plate and the low refractive index layer when the applied film of the solution dries.

[0072] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring each property are as follows. Unless otherwise specified, "%" and "parts" in the examples are by weight.

[0073] (1) Refractive Index of Low Refractive Index Layer After laminating a low refractive index layer with a protective layer onto a glass light guide plate, a laser (λ=407 nm) was incident from the glass light guide plate side using a prism coupler (manufactured by Metricon), and the refractive index at 407 nm was calculated from the measured value of the total reflection angle. This was then converted into a refractive index at 550 nm from the wavelength dispersion of the low refractive index film alone, which was calculated separately using an ellipsometer (manufactured by J.A. Woollam).

[0074] (2) Strength (2-1) Strength of Optical Laminate The optical laminates obtained in the examples and comparative examples were sampled in the shape of a 50 mm x 140 mm strip, and the second substrate side was fixed to a stainless steel plate with double-sided tape. An acrylic adhesive layer (thickness 20 μm) was attached to a PET film (T100: manufactured by Mitsubishi Plastics Film Co., Ltd.), and a piece of adhesive tape cut to 25 mm x 100 mm was attached to the first substrate of the optical laminate to form a test sample. Next, this test sample was chucked in an autograph tensile tester (manufactured by Shimadzu Corporation: AG-Xplus) so that the chuck distance was 100 mm, and then a tensile test was performed at a tensile speed of 0.3 m / min. The average test force (N / 25 mm) obtained after a 50 mm peel test was taken as the strength of the optical laminate.

[0075] (2-2) Strength of Optical Members The optical members obtained in the examples and comparative examples were sampled into 50 mm x 140 mm strips, and the light guide plate side was fixed to a stainless steel plate with double-sided tape. An acrylic adhesive layer (20 μm thick) was attached to a PET film (T100: manufactured by Mitsubishi Plastics Film Co., Ltd.), and a piece of adhesive tape cut to 25 mm x 100 mm was attached to the protective layer of the optical member to form a test sample. Next, this test sample was chucked in an autograph tensile tester (manufactured by Shimadzu Corporation: AG-Xplus) so that the chuck distance was 100 mm, and then a tensile test was performed at a tensile speed of 0.3 m / min. The average test force (N / 25 mm) obtained after a 50 mm peel test was used as the strength of the optical member. Furthermore, the sample was subjected to 24 hours in an environment of 60°C / 90% RH, and then remeasured.

[0076] (3) Scratches on the Optical Laminate during Winding The optical laminates obtained in the Examples and Comparative Examples were wound into a roll and then unwound again. The presence or absence of scratches on the unwound optical laminate was confirmed using a microscope. ２ The number of scratches per unit area was checked and evaluated according to the following criteria: ◯ (good): fewer than 5 scratches × (poor): 5 or more scratches

[0077] (4) Light Guiding Performance A prism was attached to the light guide plate of the optical member obtained in the Examples and Comparative Examples, and light from an image was incident on the light guide plate through the prism and guided into the light guide plate. A prism was also attached to the end of the light guide plate opposite to the light incident portion for the purpose of emitting light, and the image from which the light was emitted was visually inspected and evaluated according to the following criteria: ○ (Good): No change was observed from the image when light was incident × (Bad): Image distortion and / or a decrease in brightness was observed compared to the image when light was incident

[0078] [Manufacturing Example 1] Preparation of Coating Solution for Forming Low Refractive Index Layer (1) Gelling of Silicon Compound Mixture A was prepared by dissolving 0.95 g of methyltrimethoxysilane (MTMS), a precursor of the silicon compound, in 2.2 g of dimethyl sulfoxide (DMSO). 0.5 g of 0.01 mol / L oxalic acid solution was added to this mixture A, and the mixture was stirred at room temperature for 30 minutes to hydrolyze MTMS, producing a mixture B containing tris(hydroxy)methylsilane. 0.38 g of 28 wt% aqueous ammonia and 0.2 g of pure water were added to 5.5 g of DMSO, and then the mixture B was further added and stirred at room temperature for 15 minutes to gel the tris(hydroxy)methylsilane, thereby obtaining a mixture C containing a gel-like silicon compound. (2) Aging Treatment The mixture C containing the gel-like silicon compound prepared as above was incubated at 40 ° C. for 20 hours to undergo an aging treatment. (3) Pulverization Next, the gel-like silicon compound aged as described above was crushed into granules of several mm to several cm in size using a spatula. Next, 40 g of isopropyl alcohol (IPA) was added to the mixed solution C, and after light stirring, the mixture was left to stand at room temperature for 6 hours, and the solvent and catalyst in the gel were decanted. The same decantation process was performed three times to replace the solvent, yielding mixed solution D. The gel-like silicon compound in mixed solution D was then crushed (high-pressure media-less crushing). The crushing process (high-pressure media-less crushing) was performed using a homogenizer (manufactured by SMT Corporation, trade name "UH-50"), by weighing 1.85 g of the gel-like compound in mixed solution D and 1.15 g of IPA into a 5 cc screw bottle, and then crushing for 2 minutes under conditions of 50 W and 20 kHz. This crushing process crushed the gel-like silicon compound in mixed solution D, and mixed solution D became a crushed sol solution E. To 0.75 g of sol solution E, 0.062 g of a 1.5 wt % MEK (methyl ethyl ketone) solution of a photobase generator (Wako Pure Chemical Industries, Ltd.: product name WPBG266) and 0.036 g of a 5% MEK solution of bis(trimethoxysilyl)hexane were added in a ratio of 0.062 g to obtain a coating liquid for forming a low refractive index layer.

[0079] [Production Example 2] Preparation of adhesive constituting stress relaxation layer Into a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser, 90.7 parts of butyl acrylate, 6 parts of N-acryloylmorpholine, 3 parts of acrylic acid, 0.3 parts of 2-hydroxybutyl acrylate, and 0.1 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator were charged together with 100 g of ethyl acetate, and nitrogen gas was introduced while gently stirring to replace the atmosphere with nitrogen. After that, 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. An acrylic adhesive solution was prepared by blending 0.2 parts of an isocyanate crosslinker (Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd., an adduct of trimethylolpropane and tolylene diisocyanate), 0.3 parts of benzoyl peroxide (Niper BMT, manufactured by NOF Corporation), and 0.2 parts of γ-glycidoxypropyl methoxysilane (KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) per 100 parts of the solids content of the obtained acrylic polymer solution. Next, the acrylic adhesive solution was applied to one side of a silicone-treated polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical Polyester Film Corporation, thickness: 38 μm) so that the adhesive layer would have a thickness of 10 μm after drying, and the film was dried at 150°C for 3 minutes to form an adhesive layer. The storage modulus of the obtained adhesive was 1.3 × 10 ５ The adhesive layer had a viscosity of 0.13 MPa and a Tg of −60° C. This adhesive layer was used as a stress relaxation layer.

[0080] Example 1 A commercially available cycloolefin resin (COP) (Zeonex F52R, manufactured by Zeon Corporation) was dissolved in a mixed solvent of ethylcyclohexane and limonene (mixing ratio: 80 / 20) to prepare a resin solution (solids concentration: 5%). The resin solution was applied to the surface of a commercially available polyethylene terephthalate (PET) film (thickness: 50 μm) and dried to form a 2 μm-thick COP layer, resulting in a laminate film having a first resin layer (COP layer) / second resin layer (PET layer) configuration. The resulting laminate film was used as a first substrate. The low-refractive-index layer-forming coating liquid obtained in Production Example 1 was applied to the COP layer surface of the first substrate and dried to form a 2 μm-thick low-refractive-index layer. The porosity of the low-refractive-index layer was 56% by volume, and the refractive index was 1.18. Next, the stress relaxation layer (thickness: 10 μm) formed in Production Example 2 was transferred to the surface of the low-refractive-index layer. Furthermore, an acrylic film (thickness 30 μm, tensile modulus 3650 MPa, Tg: 100° C.) was laminated on the surface of the stress relaxation layer as a second substrate (protective layer) to obtain an optical laminate. The lamination was performed by roll-to-roll. The obtained optical laminate was wound into a roll. The obtained optical laminate was subjected to the above-mentioned evaluation of "strength" and "scratches." The results are shown in Table 1.

[0081] While unwinding the obtained roll-shaped optical laminate again, the first substrate was peeled off from the optical laminate. Meanwhile, the low refractive index layer side of the optical laminate from which the first substrate had been peeled off was bonded to the corona-treated surface of a glass plate for a light guide plate, the surface of which had been corona-treated, via an aqueous solution (0.5%) of an amino-based silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., "KBM-903") that would serve as an adhesion aid layer. The bonding was performed under a pressure of 0.01 MPa. After bonding, the optical member was dried at 40°C for 10 hours to obtain an optical member. The thickness of the adhesion aid layer in the obtained optical member was 3 nm. The obtained optical member was subjected to the evaluation of the "strength" and "light guiding performance" described above. The results are shown in Table 1.

[0082] [Example 2] An optical laminate was produced in the same manner as in Example 1. Furthermore, an optical member was produced in the same manner as in Example 1, except that the silane coupling agent was changed to an epoxy-based silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., "KBM-403"). The obtained optical laminate and optical member were subjected to the same evaluations as in Example 1. The results are shown in Table 1.

[0083] [Example 3] An optical laminate was produced in the same manner as in Example 1, except that a PET film (thickness 75 μm, tensile modulus 4000 MPa, Tg: 78°C) was used instead of the acrylic film as the second substrate (protective layer). An optical member was produced in the same manner as in Example 1, except that this optical laminate was used. The obtained optical laminate and optical member were subjected to the same evaluations as in Example 1. The results are shown in Table 1.

[0084] Comparative Example 1 An acrylic film (the second substrate of Example 1) was used as the first substrate instead of the COP layer / PET layer laminate film. A low refractive index layer was formed on the surface of the acrylic film in the same manner as in Example 1. The resulting laminate of the first substrate / low refractive index layer was used as an optical laminate. The resulting optical laminate was wound into a roll. The wound roll was unwound, and the low refractive index layer side was attached to a glass plate for a light guide plate to obtain an optical member. In the optical member, the first substrate (acrylic film) was used as a protective layer. The resulting optical laminate and optical member were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0085] [Comparative Example 2] A low refractive index layer was formed on the surface of the COP layer of the first substrate in the same manner as in Example 1. The resulting laminate of the first substrate / low refractive index layer was used as an optical laminate. The resulting optical laminate was wound into a roll. The wound roll was unwound, and the low refractive index layer side was attached to a glass plate for a light guide plate to obtain an optical element. The first substrate was peeled from the resulting optical element, and a second substrate with a stress relaxation layer laminated thereon was attached onto the low refractive index layer. The resulting optical laminate and optical element were subjected to the same evaluations as in Example 1. The results are shown in Table 1.

[0086] Comparative Example 3 A low refractive index layer was formed on the surface of a second substrate (protective layer) similar to that of Example 1 in the same manner as in Example 1. Furthermore, a pressure-sensitive adhesive layer similar to that of the stress relaxation layer of Example 1 was transferred to the surface of the low refractive index layer. A release liner was temporarily attached to the surface of the pressure-sensitive adhesive layer to form an optical laminate. The obtained optical laminate was wound into a roll. Next, the release liner was removed while the rolled optical laminate was again unwound, and then the optical laminate was bonded to a glass plate for a light guide plate similar to that of Example 1 via the pressure-sensitive adhesive layer to obtain an optical element. The obtained optical laminate and optical element were subjected to the same evaluations as in Example 1. The results are shown in Table 1.

[0087]

[0088] As is clear from Table 1, according to the examples of the present invention, an optical laminate having sufficient strength as a laminate and suppressing scratches (essentially scratches on the low refractive index layer) during roll winding can be obtained, and an optical laminate capable of realizing an optical component having excellent light-guiding performance can be obtained.

[0089] The optical laminate according to the embodiment of the present invention can be suitably used as an intermediate for an optical element having a low refractive index layer and a light guide plate. Such an optical element can be suitably used for optical devices such as devices for AR glasses, MR glasses, VR glasses, lighting devices, and backlight units for image display devices.

[0090] REFERENCE SIGNS LIST 10 Light guide plate 20 Low refractive index layer 30 Stress relaxation layer 40 Protective layer (second substrate) 50 Adhesion auxiliary layer 60 First substrate 100 Optical laminate

Claims

1. An optical laminate comprising: a first substrate having a tensile modulus of elasticity of 20 MPa or more; a low refractive index layer provided on one main surface of the first substrate; a stress relief layer having a storage modulus of elasticity of 0.01 MPa to 10 MPa provided on the side of the low refractive index layer opposite the first substrate; and a second substrate having a tensile modulus of elasticity of 20 MPa or more provided on the side of the stress relief layer opposite the low refractive index layer; wherein the peel force between the low refractive index layer and the first substrate is 0.5 N / 25 mm or less.

2. The optical laminate according to claim 1, wherein the surface roughness Rz of the low refractive index layer on the first substrate side is 50 nm or less.

3. The optical laminate according to claim 1, wherein the first substrate has, in order from the low refractive index layer side, a first resin layer and a second resin layer.

4. The optical laminate according to claim 3, wherein the first resin layer contains a cycloolefin resin, and the second resin layer contains a polyester resin.

5. The optical laminate according to claim 1, wherein the refractive index of the low refractive index layer is 1.25 or less.

6. The optical laminate according to claim 5, wherein the low refractive index layer has a thickness of 5 μm or less.

7. The optical laminate according to claim 6, wherein the low refractive index layer has a haze of less than 5%.

8. The optical laminate according to claim 1, wherein the stress relaxation layer has a storage modulus of 0.08 MPa to 0.20 MPa and a thickness of 5 μm to 20 μm.

9. The optical laminate according to any one of claims 1 to 8, which is long and can be wound into a roll.

10. A method for producing an optical laminate according to any one of claims 1 to 8, comprising the steps of: forming a low refractive index layer on a first substrate to produce a first laminate; and providing an adhesive layer and a second substrate, in this order, on the low refractive index layer of the first laminate.

11. The method of manufacturing according to claim 10, further comprising winding the obtained optical laminate into a roll.

12. A method for manufacturing an optical member, comprising the steps of: unwinding a roll of optical laminate obtained by the manufacturing method of claim 11; peeling the first substrate from the optical laminate; and laminating the optical laminate from which the first substrate has been peeled and a light guide plate so that the low refractive index layer and the light guide plate are adjacent to each other.

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