Laminate

Abstract

Provided is a laminate that has excellent adhesion to an object to be adhered in a high humidity environment. A laminate according to an embodiment of the present invention comprises a resin substrate, a low refractive index layer, and a pressure-sensitive adhesive agent layer. The low refractive index layer is disposed on one side of the resin substrate. The refractive index of the low refractive index layer is 1.30 or less. The pressure-sensitive adhesive agent layer is disposed on the reverse side of the resin substrate from the low refractive index layer. The laminate satisfies formula (1), where G' represents the shear storage modulus of the pressure-sensitive adhesive agent layer at 60°C and t represents the thickness of the pressure-sensitive adhesive agent layer.　Formula (1): 2,000 [Pa / μm] ≤ G' / t ≤ 15,000 [Pa / μm]

Description

Laminate

[0001] The present invention relates to a laminate.

[0002] It is known to attach a laminate including a low-refractive index layer having a refractive index lower than that of the light guide plate to a light-propagating light guide plate to arbitrarily control the propagation of light in the light guide plate. For example, a laminate including a substrate and a variable refractive index extraction layer provided on the substrate, the variable refractive index extraction layer including a first region selectively printed with a first material having a relatively low refractive index, and a second region formed by overcoating the first material with a second material having a relatively high refractive index, has been proposed (see, for example, Patent Document 1). The laminate described in Patent Document 1 has an adhesive layer formed on the surface of the substrate opposite the variable refractive index extraction layer, and is attached to the light guide plate by the adhesive layer.

[0003] International Publication No. 2014 / 031726

[0004] In recent years, the applications of optical products equipped with light guide plates have become more diverse, and the optical products may be exposed to high-humidity environments. In such cases, if the laminate described in Patent Document 1 is applied to an optical product that may be exposed to a high-humidity environment, there is a risk that the laminate will peel off from the light guide plate. The present invention has been made to solve the above-mentioned conventional problems, and its main object is to provide a laminate that has excellent adhesion to an object to which it is attached even in a high-humidity environment.

[0005] [1] A laminate according to an embodiment of the present invention includes a resin substrate, a low-refractive index layer, and a pressure-sensitive adhesive layer. The low-refractive index layer is disposed on one side of the resin substrate. The refractive index of the low-refractive index layer is 1.30 or less. The pressure-sensitive adhesive layer is disposed on the opposite side of the resin substrate from the low-refractive index layer. The laminate satisfies the following formula (1), where G' is the shear storage modulus of the pressure-sensitive adhesive layer at 60°C and t is the thickness of the pressure-sensitive adhesive layer: 2000 [Pa / μm]≦G' / t≦15000 [Pa / μm] (1). [2] In the laminate described in [1] above, the thickness t of the pressure-sensitive adhesive layer may be greater than 5 μm and less than 50 μm. [3] In the laminate described in [1] or [2] above, the shear storage modulus G' of the pressure-sensitive adhesive layer at 60°C may be 80,000 Pa or more.

[0006] According to an embodiment of the present invention, a laminate having excellent adhesion to an object to be stuck in a high humidity environment can be provided.

[0007] 1 is a schematic cross-sectional view of a laminate according to one embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of an optical product including the laminate of FIG.

[0008] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments. Note that the drawings are drawn schematically or conceptually to facilitate visibility and understanding, and the length, width, shape, size, ratio, direction, number, etc. may differ from the actual ones, and there may be no correspondence between the drawings.

[0009] A. Overall Configuration of the Laminate FIG. 1 is a schematic cross-sectional view of a laminate according to one embodiment of the present invention. The illustrated laminate 100 includes a resin substrate 1, a low-refractive index layer 2, and a pressure-sensitive adhesive layer 3. The low-refractive index layer 2 is disposed on one side of the resin substrate 1. The refractive index of the low-refractive index layer 2 is 1.30 or less. The pressure-sensitive adhesive layer 3 is disposed on the opposite side of the resin substrate 1 from the low-refractive index layer 2. The laminate 100 satisfies the following formula (1), where G' is the shear storage modulus of the pressure-sensitive adhesive layer 3 at 60°C and t is the thickness of the pressure-sensitive adhesive layer 3: 2000 [Pa / μm]≦G' / t≦15000 [Pa / μm] (1) With this configuration, the laminate satisfies formula (1), thereby improving adhesion to an object to be stuck in a high-humidity environment (typically, 80% RH (relative humidity) or higher). Therefore, even when the laminate including the low refractive index layer is attached to an object by the pressure-sensitive adhesive layer and exposed to a high temperature environment, peeling of the laminate from the object can be suppressed, and waviness of the laminate due to the pressure-sensitive adhesive layer (hereinafter referred to as adhesive waviness) can be suppressed. In other words, the moisture resistance of the laminate can be significantly improved.

[0010] The shear storage modulus G' (hereinafter referred to as G' / t) of the pressure-sensitive adhesive layer 3 at 60°C relative to the thickness t of the pressure-sensitive adhesive layer 3 is preferably 2500 Pa / μm or more, more preferably 3000 Pa / μm or more, and even more preferably 5000 Pa / μm or more. Meanwhile, G' / t is, for example, 14000 Pa / μm or less, preferably 13000 Pa / μm or less, more preferably 12000 Pa / μm or less, and even more preferably 8000 Pa / μm or less. When G' / t is in this range, the moisture resistance of the laminate can be stably improved.

[0011] The thickness t of the pressure-sensitive adhesive layer 3 is, for example, more than 5 μm, preferably 8 μm or more, more preferably 10 μm or more, and even more preferably 12 μm or more. On the other hand, the thickness t of the pressure-sensitive adhesive layer 3 is, for example, less than 50 μm, preferably 45 μm or less, more preferably 30 μm or less, and even more preferably 23 μm or less. When the thickness of the pressure-sensitive adhesive layer is in this range, the laminate can stably satisfy the above formula (1).

[0012] The shear storage modulus G' of the pressure-sensitive adhesive layer 3 at 60°C is, for example, 70,000 Pa or more, preferably 80,000 Pa or more, more preferably 85,000 Pa or more, and even more preferably 95,000 Pa or more. On the other hand, the shear storage modulus G' of the pressure-sensitive adhesive layer at 60°C is, for example, 130,000 Pa or less, preferably 120,000 Pa or less. The shear storage modulus G' of the pressure-sensitive adhesive layer at 60°C can be determined, for example, in accordance with the method described in JIS K7244-1 "Plastics - Test methods for dynamic mechanical properties," by reading the value at 60°C when measured at a frequency of 1 Hz, in the range of -50°C to 150°C, and at a heating rate of 5°C / min. When the shear storage modulus of the pressure-sensitive adhesive layer is in this range, the laminate can more stably satisfy the above formula (1).

[0013] The shear storage modulus G' of the pressure-sensitive adhesive layer 3 at 23°C is, for example, 90,000 Pa to 200,000 Pa, and preferably 100,000 Pa to 190,000 Pa. The shear storage modulus G' of the pressure-sensitive adhesive layer at 23°C can be determined, for example, in accordance with the method described in JIS K 7244-1 "Plastics - Test methods for dynamic mechanical properties," by reading the value at 23°C when measured at a frequency of 1 Hz in the range of -50°C to 150°C at a heating rate of 5°C / min.

[0014] The resin substrate, the low refractive index layer, and the pressure-sensitive adhesive layer will be specifically described below.

[0015] B. Resin Substrate The resin substrate 1 is typically capable of transmitting light. The total light transmittance of the resin substrate 1 is, for example, 70% to 100%, and preferably 80% to 99%. If the total light transmittance of the resin substrate is within this range, the laminate as a whole can achieve excellent transparency. Therefore, adverse effects in the use of the laminate can be suppressed. The total light transmittance is measured, for example, using any appropriate haze meter.

[0016] Any appropriate configuration may be adopted for the resin substrate 1. Examples of materials for the resin substrate 1 include thermoplastic resin materials and curable resin materials, and preferably thermoplastic resin materials.

[0017] Examples of thermoplastic resin materials include (meth)acrylic resins such as polymethyl methacrylate (PMMA); cycloolefin (COP) resins; polyester resins such as polyethylene terephthalate (PET); polyvinyl acetal resins; polycarbonate resins; polyarylate resins; and polyurethane resins. Note that "(meth)acrylic" refers to acrylic and / or methacrylic resins. The materials for the resin substrate 1 can be used alone or in combination. Among these materials for the resin substrate 1, (meth)acrylic resins are preferred.

[0018] The thickness of the resin substrate 1 is, for example, 10 μm to 80 μm, and preferably 20 μm to 40 μm.

[0019] C. Low Refractive Index Layer The low refractive index layer 2 is typically provided directly on the surface of the resin substrate 1. As described above, the refractive index of the low refractive index layer 2 is 1.30 or less, with the lower limit being greater than 1.00. The refractive index of the low refractive index layer 2 is preferably 1.13 to 1.28, more preferably 1.14 to 1.27, even more preferably 1.15 to 1.26, and particularly preferably 1.16 to 1.25. Unless otherwise specified, the refractive index refers to a refractive index measured at a wavelength of 550 nm. The refractive index is a value measured, for example, by the method described in the Examples below.

[0020] The total light transmittance of the low refractive index layer 2 is, for example, 85% to 99%, preferably 87% to 98%, and more preferably 89% to 97%. If the total light transmittance of the low refractive index layer is in this range, excellent transparency can be achieved for the entire laminate.

[0021] The haze of the low refractive index layer 2 is, for example, less than 5%, and preferably less than 3%. On the other hand, the haze is, for example, 0.1% or more, and for example, 0.2% or more. If the haze of the low refractive index layer is in this range, excellent transparency can be achieved for the entire laminate. The haze can be calculated from the following formula using values ​​measured with a haze meter (for example, "HM-150" manufactured by Murakami Color Research Laboratory Co., Ltd.): Haze (%) = [Diffuse transmittance (%) / Total light transmittance (%)] × 100 (%)

[0022] The thickness of the low refractive index layer 2 is, for example, 0.3 μm to 10 μm, preferably 0.5 μm to 5.0 μm, and more preferably 0.8 μm to 1.2 μm. If the thickness of the low refractive index layer is in this range, it is possible to achieve a thin laminate having excellent moisture resistance.

[0023] Any appropriate configuration that can achieve the above-described desired properties can be adopted for the low refractive index layer 2. The low refractive index layer 2 may have any appropriate pattern shape depending on the application of the laminate 100.

[0024] Materials constituting the low refractive index layer 2 may include, for example, materials 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 of materials constituting the low refractive index layer 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 silicate with acid or ion exchange resin. Materials constituting the low refractive index layer also 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.

[0025] In one embodiment, the low refractive index layer 2 may contain spaces such as pores and gaps therein. In this case, the porosity of the low refractive index layer 2 is, for example, 20 vol% to 60 vol%, preferably 25 vol% to 55 vol%, more preferably 30 vol% to 50 vol%, and even more preferably 35 vol% to 45 vol%. Such a porosity allows the refractive index of the low refractive index layer to be within an appropriate range and ensures strength. Here, the porosity is a value calculated, for example, from the refractive index measured with an ellipsometer using the Lorentz-Lorenz formula.

[0026] The size of the voids that can be contained in the low refractive index layer 2 can be adjusted to a desired size depending on the purpose, application, etc. The size of the voids that can be contained in the low refractive index layer 2 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 that can be contained in the low refractive index layer is, for example, 500 nm or less, preferably 200 nm or less, and more preferably 100 nm or less. Note that the size of the voids refers to the diameter of the major axis of the voids, out of the diameter of the major axis and the diameter of the minor axis.

[0027] The pore size can be quantified by the BET test method. In one embodiment, 0.1 g of a measurement sample (e.g., a formed low refractive index layer) is placed in the capillary of a specific surface area measurement device (e.g., "ASAP2020" manufactured by Micromeritics), and then the sample is dried under reduced pressure at room temperature for 24 hours to remove gases contained in the measurement sample. Then, an adsorption isotherm is drawn by adsorbing nitrogen gas onto the measurement sample, and the pore size distribution is determined. This allows the pore size to be evaluated.

[0028] Examples of the low refractive index layer having a space therein include a low refractive index layer made of a porous material and / or a layer containing an air layer at least in part. The low refractive index layer typically contains aerogel and / or particles (which may be, for example, 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 pores 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.

[0029] Any appropriate particles may be used as the particles. The particles are typically composed 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 shape. The particle shape can be confirmed, for example, by observation with a transmission electron microscope.

[0030] An example of the low refractive index layer 2 is a structure composed of one or more types of structural units that form a fine void structure, and in which these structural units are bonded to each other (for example, chemically bonded 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 two or more shapes in combination.

[0031] A specific example of the low-refractive-index layer 2 is a low-refractive-index layer composed of a porous material in which particles having micropores (hereinafter referred to as microporous particles) are chemically bonded to one another. Such a low-refractive-index layer can be obtained, for example, by chemically bonding the microporous particles to one another. The shape of the microporous particles is not particularly limited and may be, for example, spherical or other shapes. Furthermore, the microporous particles may be, for example, sol-gel beaded particles, nanoparticles (e.g., 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. In one embodiment, the microporous particles are, for example, microporous particles of a silicon compound, and the porous material is, for example, a silicone porous material. The microporous particles of the silicon compound include, for example, a pulverized gel silica compound.

[0032] Another example of the low refractive index layer 2 is a layer containing a fibrous material such as nanofibers, in which spaces are formed by the entanglement of the fibrous material. Further examples of the low refractive index layer include a layer formed using hollow nanoparticles or nanoclay, and a layer formed using hollow nanoballoons or magnesium fluoride. The low refractive index layer may be composed of a single constituent material, or may be composed of multiple constituent materials. The low refractive index layer may be composed of a single form of the above examples, or may be composed of multiple forms of the above examples.

[0033] The low refractive index layer 2 may have, for example, an open-cell structure in which the pores are interconnected. An open-cell structure refers to a porous body (e.g., a porous silicone body) in which the pores are interconnected three-dimensionally, and can also be described as a state in which the pore spaces are interconnected. The open-cell structure of the low refractive index layer can increase the porosity. It is difficult to form an open-cell structure using closed-cell particles with individual pore structures, such as hollow particles (e.g., hollow silica). However, when using silica sol particles (a pulverized product of a gel-like silicon compound that forms a sol), the silica sol particles can have a three-dimensional dendritic structure. The dendritic particles can settle and deposit in a coating film (a coating film of a sol containing a pulverized product of a gel-like silicon compound) to easily form an open-cell structure. The low refractive index layer preferably has a monolithic structure in which the open-cell structure includes a plurality of pore distributions. The monolithic structure refers to, for example, a hierarchical structure including a structure in which nano-sized pores exist and an open-cell structure in which nano-sized pores are aggregated. The monolithic structure, for example, can provide membrane strength through fine pores while providing high porosity through a coarse open-cell structure, thereby achieving both membrane strength and high porosity.

[0034] For example, the monolith structure can be formed by controlling the pore distribution of the void structure generated in the gel (gel silicon compound) before being crushed into silica sol particles.Also, for example, when crushing the gel silicon compound, the monolith structure can be formed by controlling the particle size distribution of the crushed silica sol particles to a predetermined size.In addition, the particle size distribution can be measured by, for example, a particle size distribution evaluation device such as dynamic light scattering method or laser diffraction method, or an electron microscope such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0035] As described above, the low refractive index layer 2 may contain pulverized gel compounds such as gel silicon compounds, and the pulverized particles are chemically bonded to each other. The chemical bond is not particularly limited, and examples thereof include cross-linking, covalent bonding, and hydrogen bonding. The volume average particle diameter of the pulverized particles in the low refractive index layer 2 is, for example, 0.10 μm or more, preferably 0.20 μm or more, and more preferably 0.40 μm or more. Meanwhile, the volume average particle diameter of the pulverized particles in the low refractive index layer 2 is, for example, 2.00 μm or less, preferably 1.50 μm or less, and more preferably 1.00 μm or less. The volume average particle diameter is an index of the particle size variation of the pulverized particles, and can be determined, for example, by particle size distribution measurement.

[0036] The low refractive index layer 2 may contain silicon atoms. For example, the silicon atoms contained in the low refractive index layer 2 are preferably siloxane-bonded. Of all silicon atoms contained in the low refractive index layer 2, the proportion of unbonded silicon atoms (specifically, residual silanols) is, for example, less than 50%, preferably 30% or less, and more preferably 15% or less.

[0037] The low refractive index layer 2 can be formed, for example, by coating or printing a low refractive index layer-forming liquid (sometimes also referred to as a coating liquid) on the surface of the resin substrate 1. More specifically, the low refractive index layer 2 can be formed by heating a coated film or printed layer of the low refractive index layer-forming liquid formed on the resin substrate 1.

[0038] In one embodiment, the coating film can be formed using a coating liquid containing microporous particles, and the microporous particles can be chemically bonded to each other by heating (including drying) the coating liquid. The coating liquid containing microporous particles is, for example, a suspension. For example, a catalyst (crosslinking reaction accelerator) that promotes crosslinking between the microporous particles (e.g., a dehydration condensation reaction of residual silanol groups that may be contained in the microporous particles) and / or a substance that generates a catalyst (crosslinking reaction accelerator) (catalyst generator) may be added to the coating liquid. Examples of catalysts include photoactivated catalysts and thermally activated catalysts. Examples of catalyst-generating substances (catalyst generators) include photocatalyst generators and thermal catalyst generators. Examples of photocatalyst generators include photobase generators (catalysts that generate a basic catalyst upon light irradiation) and photoacid generators (substances that generate an acidic catalyst upon light irradiation). For example, the microporous particles are pulverized gel-like compounds (preferably gel-like silicon compounds), and the low refractive index layer is a low refractive index layer composed of a porous body (preferably a silicone porous body) containing the pulverized gel-like compounds. Such microporous particles may have a state in which the three-dimensional structure of the gel-like compound before pulverization is dispersed in the three-dimensional basic structure, and by using such microporous particles, a structure based on the three-dimensional basic structure can be formed. Specifically, a new structure different from the three-dimensional structure of the gel-like compound can be formed. In this way, the finally obtained low refractive index layer (low refractive index layer) can have a low refractive index similar to that of an air layer, for example. Furthermore, by chemically bonding the microporous particles to each other, the three-dimensional basic structure can be fixed, and sufficient strength can be ensured in the finally obtained low refractive index layer (low refractive index layer). Details of the specific configuration and formation method of the low refractive index layer (low refractive index layer) are described, for example, in International Publication No. 2019 / 151073. The description of this publication is incorporated herein by reference.

[0039] The coating thickness of the coating liquid can be set according to the desired thickness of the low refractive index layer 2. The heating temperature of the coating film (coating liquid) is, for example, 20°C or higher, and preferably 50°C or higher. On the other hand, the heating temperature of the coating film (coating liquid) is, for example, 200°C or lower, and preferably 150°C or lower. The heating time of the coating film (coating liquid) is, for example, 10 seconds or longer. On the other hand, the heating time of the coating film (coating liquid) is, for example, 24 hours or shorter, preferably 1 hour or shorter, more preferably 30 minutes or shorter, and even more preferably 10 minutes or shorter.

[0040] D. Pressure-sensitive adhesive layer The pressure-sensitive adhesive layer 3 is typically provided directly on the surface of the resin substrate 1 opposite the low refractive index layer 2. The pressure-sensitive adhesive layer 3 is provided to attach the laminate 100 to an attachment target (typically an optical member), as will be described in detail later. Any appropriate pressure-sensitive adhesive can be used as the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 3, as long as it has the above-mentioned properties. A typical example of the pressure-sensitive adhesive is an acrylic pressure-sensitive adhesive (acrylic pressure-sensitive adhesive composition).

[0041] Acrylic pressure-sensitive adhesive compositions typically contain a (meth)acrylic polymer as a major component. The (meth)acrylic polymer may be contained in the pressure-sensitive adhesive composition in an amount of, for example, 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more, based on the solid content of the pressure-sensitive adhesive composition. The (meth)acrylic polymer contains structural units derived from alkyl(meth)acrylate. The (meth)acrylate includes acrylate and / or methacrylate. The content of structural units derived from alkyl(meth)acrylate in the (meth)acrylic polymer is, for example, 80% by mass or more, preferably 90% by mass or more. 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, more preferably 3 to 6. The alkyl(meth)acrylate is particularly preferably butyl acrylate.

[0042] The (meth)acrylic polymer may contain, in addition to a structural unit derived from an alkyl (meth)acrylate, a structural unit derived from a copolymerizable monomer copolymerizable with the alkyl (meth)acrylate. When the (meth)acrylic polymer contains a structural unit derived from a copolymerizable monomer, the shear storage modulus G' of the PSA layer at 60°C can be stably adjusted to within the above range. Examples of the copolymerizable monomer include a carboxyl group-containing monomer, a hydroxyl group-containing monomer, an amide group-containing monomer, an aromatic ring-containing (meth)acrylate, and a heterocycle-containing vinyl monomer. The copolymerizable monomers may be used alone or in combination. Among the copolymerizable monomers, preferred are carboxyl group-containing monomers such as (meth)acrylic acid; hydroxyl group-containing monomers such as 4-hydroxybutyl acrylate; and heterocycle-containing vinyl monomers such as N-acryloylmorpholine. The content of the structural units derived from copolymerization monomers in the (meth)acrylic polymer is, for example, 0% by mass to 20% by mass, preferably 0.5% by mass to 15% by mass, more preferably 0.8% by mass to 13% by mass, and particularly preferably 5% by mass to 12% by mass.

[0043] The acrylic pressure-sensitive adhesive composition preferably contains a silane coupling agent and / or a crosslinking agent. Examples of the silane coupling agent include an epoxy group-containing silane coupling agent. Examples of the crosslinking agent include an isocyanate-based crosslinking agent and a peroxide-based crosslinking agent. Furthermore, the acrylic pressure-sensitive adhesive composition may contain an antioxidant and / or a conductive agent. Details of the pressure-sensitive adhesive layer or the acrylic pressure-sensitive adhesive composition are described in, for example, JP 2006-183022 A, JP 2015-199942 A, JP 2018-053114 A, JP 2016-190996 A, and WO 2018 / 008712 A, the disclosures of which are incorporated herein by reference.

[0044] E. Usage of the Laminate As shown in FIG. 2 , the laminate 100 described above is typically applicable to an optical product 200 including a light guide plate 10. In one embodiment, the laminate 100 is attached to the light guide plate 10, which is an example of an attachment target, by the pressure-sensitive adhesive layer 3. The light guide plate 10 is typically capable of propagating light incident from a light source (typically an LED), not shown, in a predetermined direction (the left-right direction in FIG. 2 ). In the illustrated example, the laminate 100 is attached to the entire light guide plate 10. This allows the light propagating through the light guide plate to be controlled as desired.

[0045] The present invention will be specifically described below using 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 based on mass.

[0046] (1) Refractive Index The laminates obtained in the Examples and Comparative Examples were cut into a size of 100 mm x 100 mm to prepare samples. The samples were attached to the surface of a glass plate with an adhesive layer. The thickness of the glass plate was 0.7 mm. The center of the back surface of the glass plate (approximately 20 mm in diameter) was filled in with black marker to prepare a sample that did not reflect light from the back surface of the glass plate. The samples were set in an ellipsometer (VASE, manufactured by J.A. Woollam Japan), and the refractive index was measured at a wavelength of 550 nm and an incident angle of 50 to 80 degrees.

[0047] (2) Reliability Test in a High-Humidity Environment The laminates obtained in the Examples and Comparative Examples were cut into samples measuring 100 mm x 100 mm. The samples were then attached to the surface of a glass plate using an adhesive layer. The glass plate had a size of 100 mm x 100 mm and a thickness of 0.7 mm. The attached sample was then left standing at 60°C and 95% RH for 6 hours, then cooled to 30°C and 95% RH at a cooling rate of 3.75°C / h, and then left standing at 30°C and 95% RH for 8 hours. The temperature was then increased to 60°C and 95% RH at a cooling rate of 15°C / h. This cycle was repeated 10 times. The sample was then visually observed for peeling from the glass plate. This reliability test was performed twice for each sample, and the evaluation was based on the following criteria. ◯: In both of the two reliability tests, the sample did not peel off from the glass plate and no waviness of the adhesive was observed (0 / 2). ×: In at least one of the two reliability tests, the sample peeled off from the glass plate or waviness of the adhesive was observed (1 / 2 or 2 / 2).

[0048] [Preparation Example 1] Preparation of coating liquid for forming low refractive index layer (1) Gelling of silicon compound 0.95 g of methyltrimethoxysilane (MTMS), a precursor of the silicon compound, was dissolved in 2.2 g of dimethyl sulfoxide (DMSO) to prepare a mixed solution A. 0.5 g of 0.01 mol / L oxalic acid aqueous solution was added to this mixed solution A, and the MTMS was hydrolyzed by stirring at room temperature (23 ° C.) for 30 minutes to produce a mixed solution B containing tris (hydroxy) methyl silane. 0.38 g of 28 mass% ammonia water and 0.2 g of pure water were added to 5.5 g of DMSO, and then the mixed solution B was further added and stirred at room temperature (23 ° C.) for 15 minutes to gel the tris (hydroxy) methyl silane, thereby obtaining a mixed solution C containing a gel-like silicon compound. (2) Aging Treatment The mixed solution C containing the gel-like silicon compound prepared as described above was incubated at 40°C for 20 hours to carry out an aging treatment. (3) Pulverization Treatment 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 isobutyl alcohol (IBA) was added to the mixed solution C, and after light stirring, the mixture was left to stand at room temperature for 6 hours to decant the solvent and catalyst in the gel. The same decantation treatment was carried out three times to replace the solvent, and mixed solution D was obtained. Next, the gel-like silicon compound in mixed solution D was pulverized (high-pressure media-less pulverization). The pulverization treatment (high-pressure media-less pulverization) was carried out using a homogenizer (manufactured by SMT Corporation, trade name "UH-50"), in which 1.85 g of the gel-like compound in mixed solution D and 1.15 g of IBA were weighed into a 5 cc screw bottle, and then pulverized for 2 minutes under conditions of 50 W and 20 kHz. This pulverization treatment pulverized the gel-like silicon compound in mixed solution D, and mixed solution D became pulverized sol solution E. The volume average particle size, which indicates the particle size variation of the pulverized material contained in sol solution E, was confirmed using a dynamic light scattering Nanotrac particle size analyzer (manufactured by Nikkiso Co., Ltd., UPA-EX150 model), and was found to be 0.10 μm to 0.30 μm.Furthermore, 0.062 g of a 1.5 mass % MEK (methyl ethyl ketone) solution of a photobase generator (Wako Pure Chemical Industries, Ltd.: product name WPBG266) and 0.036 g of a 5 mass % MEK solution of bis(trimethoxysilyl)hexane were added to 0.75 g of sol solution E to obtain a coating liquid for forming a low refractive index layer.

[0049] [Preparation Example 2] Preparation of Pressure-Sensitive Adhesive Layer Into a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser, 92 parts by mass of butyl acrylate, 5 parts by mass of N-acryloylmorpholine, 2.9 parts by mass of acrylic acid, 0.1 parts by mass of 2-hydroxybutyl acrylate, and 0.1 parts by mass of 2,2'-azobisisobutyronitrile as a polymerization initiator were charged together with 100 parts by mass of ethyl acetate, and nitrogen gas was introduced while gently stirring to replace the atmosphere with nitrogen. Thereafter, 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 by mass of an isocyanate crosslinker (Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd., an adduct of trimethylolpropane and tolylene diisocyanate), 0.3 parts by mass of benzoyl peroxide (Niper BMT, manufactured by NOF Corporation), and 0.2 parts by mass of γ-glycidoxypropyl methoxysilane (KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) per 100 parts of the solids content of the resulting acrylic polymer solution. The acrylic adhesive solution was then applied to one side of a silicone-treated polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical Polyester Film Corporation, thickness: 38 μm) and dried at 150°C for 3 minutes to form an adhesive layer with a thickness of 10 μm. The shear storage modulus G' of the adhesive layer at 60°C is shown in Table 1.

[0050] Preparation Example 3 Preparation of Pressure-Sensitive Adhesive Layer A pressure-sensitive adhesive layer was obtained in the same manner as in Preparation Example 2, except that the thickness of the pressure-sensitive adhesive layer was changed to 20 μm.

[0051] Preparation Example 4 Preparation of Pressure-Sensitive Adhesive Layer A pressure-sensitive adhesive layer was obtained in the same manner as in Preparation Example 2, except that the thickness of the pressure-sensitive adhesive layer was changed to 5 μm.

[0052] Preparation Example 5 Preparation of Pressure-Sensitive Adhesive Layer Into a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser, 100 parts by mass of butyl acrylate, 5 parts by mass of acrylic acid, 0.1 parts by mass of 4-hydroxybutyl acrylate, and 0.1 parts by mass of 2,2′-azobisisobutyronitrile as a polymerization initiator were charged together with 100 parts by mass of ethyl acetate, and nitrogen gas was introduced while gently stirring to replace the atmosphere with nitrogen. Thereafter, a polymerization reaction was carried out for 8 hours while maintaining the liquid temperature in the flask at around 55° C., to prepare a solution of an acrylic polymer. A solution of an acrylic pressure-sensitive adhesive composition was prepared by blending 0.6 parts by mass of an isocyanate crosslinking agent (Takenate D101E, trimethylolpropane tolylene diisocyanate, manufactured by Mitsui Chemicals, Inc.), 0.2 parts by mass of benzoyl peroxide (Niper BMT, manufactured by NOF Corporation), and 0.2 parts by mass of γ-glycidoxypropyl methoxysilane (KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) per 100 parts by mass of the solids content of the obtained acrylic polymer solution. Next, the solution of the acrylic pressure-sensitive adhesive composition was applied to one side of a polyethylene terephthalate film (Mitsubishi Chemical Polyester Film Corporation, MRF38) that had been treated with a silicone release agent, and the resulting film was dried at 150°C for 3 minutes to form a 15 μm-thick pressure-sensitive adhesive layer.

[0053] Preparation Example 6 Preparation of Adhesive Layer A transparent adhesive sheet (manufactured by Nitto Denko Corporation, LUCIAS (registered trademark), CS986) having a thickness of 25 μm was prepared as an adhesive layer.

[0054] Preparation Example 7 Preparation of Adhesive Layer A 50 μm thick transparent adhesive sheet (manufactured by Nitto Denko Corporation, LUCIAS (registered trademark), CS986) was prepared as an adhesive layer.

[0055] [Examples 1 to 4 and Comparative Examples 1 and 2] The coating liquid for forming a low refractive index layer of Preparation Example 1 was applied to a 30 μm thick acrylic resin substrate (resin substrate, manufactured by Toyo Kohan Co., Ltd.), and the coating film was then dried. In this way, a low refractive index layer was formed on the acrylic resin substrate. The refractive index of the low refractive index layer was 1.19. The thickness of the low refractive index layer was 1.0 μm. Next, the pressure-sensitive adhesive layer obtained in each Preparation Example shown in Table 1 was transferred to the surface of the acrylic resin substrate opposite the low refractive index layer. In this way, a laminate having a configuration of low refractive index layer / resin substrate / pressure-sensitive adhesive layer was obtained.

[0056]

[0057] As is clear from Table 1, if the laminate satisfies the above formula (1), it will have excellent adhesion to the object to be attached in a high humidity environment, and will have an excellent appearance with no visible waviness of the adhesive.

[0058] The laminate according to the embodiment of the present invention can be used in various optical products, and can be particularly suitably used in optical products including a light guide plate.

[0059] REFERENCE SIGNS LIST 1 resin substrate 2 low refractive index layer 3 pressure-sensitive adhesive layer 100 laminate

Claims

1. A laminate comprising: a resin substrate; a low refractive index layer having a refractive index of 1.30 or less, disposed on one side of the resin substrate; and an adhesive layer disposed on the opposite side of the resin substrate from the low refractive index layer, wherein the laminate satisfies the following formula (1): 2000 [Pa / μm]≦G' / t≦15000 [Pa / μm] (1), where G' is the shear storage modulus of the adhesive layer at 60°C and t is the thickness of the adhesive layer.

2. The laminate according to claim 1, wherein the thickness t of the pressure-sensitive adhesive layer is greater than 5 μm and less than 50 μm.

3. The laminate described in claim 1 or 2, wherein the shear storage modulus G' of the pressure-sensitive adhesive layer at 60°C is 80,000 Pa or more.

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