Optical laminate, optical device, and method for producing optical laminate

Abstract

An optical laminate (100) comprises: a first optical sheet (10) that has a first main surface (12s) with a relief structure thereon and a second main surface (18s) on the reverse side from the first main surface; and a second optical sheet (30) that has a third main surface (32s) disposed on the first main surface side of the first optical sheet. The relief structure of the first main surface includes a plurality of recessed portions (14) and flat portions (10s) that are each between two recessed portions (14) adjacent to one another among the plurality of recessed portions. The third main surface and the flat portions of the first main surface are bonded by covalent bonding with a molecular adhesive (20) therebetween.

Description

Optical laminate, optical device, and method for manufacturing optical laminate

[0001] The present invention relates to optical stacks and optical devices comprising such optical stacks.

[0002] Optical sheets (e.g., microlens sheets, prism sheets, and brightness enhancement films (e.g., Brightness Enhancement Film: BEF (registered trademark) manufactured by 3M)) are used in various optical devices (e.g., display devices and lighting devices). In this specification, the term "optical sheet" is not limited to the above-mentioned examples but broadly includes sheet-like optical members, further including, for example, diffuser plates and light guide plates. The term "sheet-like" is used to mean a plate-like or film-like member, regardless of the rigidity (flexibility) and thickness of the sheet. An optical sheet is attached to another optical sheet or an optical device, for example, using an adhesive layer. In this specification, the term "optical laminate" refers to a configuration including an optical sheet and an adhesive layer or a configuration including multiple optical sheets. In this specification, the term "adhesive" is used to mean a pressure-sensitive adhesive (also called a "pressure-sensitive adhesive").

[0003] The present applicant has disclosed in Patent Document 1 an optical laminate (referred to as an "optical laminate sheet" in Patent Document 1) that can be used in display devices and lighting devices. The optical laminate of Patent Document 1 includes an optical sheet (e.g., a microlens sheet) having a concave-convex structure on its surface, and an adhesive layer provided on the surface having the concave-convex structure. 5% to 90% of the height of the convex portions of the concave-convex structure is filled with the adhesive layer. The adhesive layer is formed from an adhesive composition containing a graft polymer obtained by graft polymerizing a chain containing a cyclic ether group-containing monomer onto a (meth)acrylic polymer, and a photocationic polymerization initiator or a thermosetting catalyst.

[0004] Furthermore, Patent Documents 2 and 3 disclose light distribution structures that utilize total reflection at the interfaces of multiple air cavities (internal spaces), which can be used in display devices and lighting devices. The use of the light distribution structures disclosed in Patent Documents 2 and 3 can improve the degree of freedom and accuracy of light distribution control. The entire disclosures of Patent Documents 2 and 3 are incorporated herein by reference.

[0005] Patent Document 1: JP 2012-007046 A, International Publication No. 2011 / 124765, International Publication No. 2019 / 087118

[0006] The present inventors have investigated forming the light distribution structure described in Patent Documents 2 and 3 by disposing an adhesive layer on the uneven surface of an optical sheet having an uneven surface. In this case, the shape and volume of the multiple air cavities that make up the light distribution structure change depending on the extent to which the adhesive layer penetrates into the recesses of the uneven structure, which ultimately affects the characteristics of the light distribution structure. Therefore, it is necessary to prevent the adhesive layer from penetrating into the recesses of the uneven structure.

[0007] Here, we have explained the issues with optical laminates formed by laminating other optical sheets onto a surface having a concave-convex structure of an optical sheet using a conventional adhesive, using the light distribution structures described in Patent Documents 2 and 3 as examples, but this issue is not limited to the light distribution structures described in Patent Documents 2 and 3, and is common to optical laminates formed by laminating other optical sheets onto a surface having a concave-convex structure.

[0008] The present invention has been made to solve the above-mentioned problems, and aims to provide an optical laminate laminated with another optical sheet without substantially affecting the shape and volume of the recesses on the surface having a textured structure of the optical sheet, and an optical device having such an optical laminate, and / or to provide a method for manufacturing such an optical laminate.

[0009] According to an embodiment of the present invention, the following solutions are provided:

[0010] [Item 1] An optical laminate comprising: a first optical sheet having a first main surface with a concave-convex structure and a second main surface opposite the first main surface; and a second optical sheet having a third main surface arranged on the first main surface side of the first optical sheet, wherein the concave-convex structure of the first main surface includes a plurality of recesses and a flat portion between two adjacent recesses of the plurality of recesses, and the flat portion of the first main surface and the third main surface are covalently bonded via a molecular adhesive.

[0011] [Item 2] The optical laminate according to Item 1, wherein, for each of the plurality of recesses, a distance from an opening surface defined by the opening of the recess to a deepest portion of the recess is defined as A, and a point at which a distance from the opening surface to the third main surface of the second optical sheet that has penetrated into the recess is a maximum value B is defined as a deepest penetration point, and B / A is 0.2 or less.

[0012] [Item 3] The optical laminate according to Item 2, wherein the deepest penetration point is located closer to the deepest portion than the side surface of the recess.

[0013] [Item 4] The optical laminate according to any one of Items 1 to 3, wherein the distance from the flat portion to the third main surface does not exceed 500 nm.

[0014] [Item 5] An optical laminate comprising: a first optical sheet having a first main surface with a concave-convex structure and a second main surface opposite the first main surface; and a second optical sheet having a third main surface arranged on the first main surface side of the first optical sheet, wherein the concave-convex structure of the first main surface includes a plurality of recesses and a flat portion between two adjacent recesses of the plurality of recesses, wherein, for each of the plurality of recesses, a distance from an opening surface defined by an opening of the recess to a deepest portion of the recess is defined as A, and a point at which a distance from the opening surface to the third main surface of the second optical sheet that has penetrated into the recess takes a maximum value B is defined as a deepest penetration point, where B / A is 0.2 or less, and the distance from the flat portion to the third main surface does not exceed 500 nm.

[0015] [Item 6] The optical laminate according to Item 5, wherein the flat portion of the first main surface and the third main surface are covalently bonded via a molecular adhesive.

[0016] [Item 7] The molecular adhesive has at least one reactive group selected from the group consisting of an azide group, an amino group, a mercapto group, an isocyanate group, a ureido group, an epoxy group, a silanol group, and an alkoxysilyl group. The optical laminate according to any one of Items 1 to 4 and 6.

[0017] [Item 8] The optical laminate according to any one of Items 1 to 4 and 6, wherein the molecular adhesive has an azide group and a silanol group or an alkoxysilyl group.

[0018] [Item 9] The optical laminate according to item 8, wherein the molecular adhesive further has a triazine ring, and the azide group is bonded to the triazine ring.

[0019] [Item 10] The optical laminate according to item 9, wherein the flat portion and the third main surface have at least one reactive group selected from the group consisting of a hydrocarbon group, a carbonyl group, and a hydroxyl group, and form a covalent bond with the molecular adhesive.

[0020] [Item 11] The optical laminate according to any one of Items 1 to 10, wherein the first optical sheet is formed from a cured product of a curable resin.

[0021] [Item 12] The optical laminate according to any one of Items 1 to 11, having a haze value of 5.0% or less.

[0022] [Item 13] An optical device comprising a light guide plate having the optical laminate according to any one of items 1 to 12.

[0023] [Item 14] A method for producing the optical laminate according to any one of Items 1 to 12, comprising: Step A of applying a molecular adhesive represented by the following general formula [I] to at least one of the flat portion of the first optical sheet and the third main surface of the second optical sheet; Step B of irradiating the molecular adhesive with light after Step A; and Step C of heating while applying pressure to the flat portion and the third main surface in a state where the flat portion and the third main surface are opposed to each other. [wherein E is any group; F is an OH group or an OH-yielding group; -Q is -N ３ or -NR １ (R ２ ) -NR １ (R ２ ) R １、 R ２is H, a hydrocarbon group having 1 to 24 carbon atoms, or -RSi(R')n(OA)3-n (R is a chain hydrocarbon group having 1 to 12 carbon atoms. R' is a chain hydrocarbon group having 1 to 4 carbon atoms. A is H or a chain hydrocarbon group having 1 to 4 carbon atoms. n is an integer from 0 to 2.) R １ and R ２ may be the same or different.]

[0024] [Item 15] The method according to Item 14, wherein in step C, heating is performed at a temperature of 60°C or higher and 150°C or lower.

[0025] [Item 16] The method according to Item 14, wherein in step C, heating is performed at a temperature of 80°C or higher and 110°C or lower.

[0026] According to an embodiment of the present invention, there is provided an optical laminate laminated with another optical sheet without substantially affecting the shape and volume of the recesses on the surface having a textured structure of the optical sheet, and an optical device having such an optical laminate. Also, according to an embodiment of the present invention, there is provided a method for manufacturing such an optical laminate.

[0027] 4B is a schematic cross-sectional view of an optical laminate 100 according to an embodiment of the present invention. FIG. 4C is a schematic partial cross-sectional view of the optical laminate 100. FIG. 4D is a schematic partial cross-sectional view of an optical laminate 200 of a comparative example. FIG. 4E is a schematic plan view of a first optical sheet 10a included in an optical laminate according to an embodiment of the present invention. FIG. 4F is a schematic cross-sectional view of the first optical sheet 10a taken along line 4B-4B' shown in FIG.

[0028] An optical laminate, an optical device having the optical laminate, and a method for manufacturing the optical laminate according to an embodiment of the present invention will be described below. The embodiments of the present invention are not limited to the following examples.

[0029] FIG. 1 shows a schematic cross-sectional view of an optical laminate 100 according to an embodiment of the present invention. The optical laminate 100 includes a first optical sheet 10 having a first major surface 12s with a relief structure and a second major surface 18s opposite the first major surface 12s, and a second optical sheet 30 having a third major surface 32s disposed on the first major surface 12s side of the first optical sheet 10. The second optical sheet 30 has a fourth major surface 38s opposite the third major surface 32s. The relief structure of the first major surface 12s includes a plurality of recesses 14 and flat portions 10s between adjacent recesses 14 among the plurality of recesses 14. The third major surface 32s is flat, and the flat portions 10s of the first major surface 12s and the third major surface 32s are covalently bonded via a molecular adhesive 20.

[0030] A plurality of internal spaces 14a are defined by each of the plurality of recesses 14 in the first major surface 12s of the first optical sheet 10a and the third major surface 32s of the second optical sheet. The internal spaces 14a are typically voids filled with air. However, the internal spaces 14a may be filled with a material having a lower refractive index than the first optical sheet 10a and the second optical sheet 30 instead of air. The interfaces formed by the internal spaces 14a can cause total internal reflection (TIR) ​​of light propagating within the optical laminate 100.

[0031] Here, the flat portion 10s of the first major surface 12s and the second major surface 18s of the first optical sheet 10, and the third major surface 32s and the fourth major surface 38s of the second optical sheet 30 are parallel to the XY plane. For example, light propagating in the −Y direction within the second optical sheet 30 is totally internally reflected by the multiple internal spaces 14a and directed in the Z direction perpendicular to the XY plane.

[0032] The first optical sheet 10 and the second optical sheet 30 are preferably formed of a light-transmitting resin. Here, the term "resin" is used in a broad sense to include thermoplastic resins, curable resins, elastomers, and rubbers. Curable resins include, for example, thermosetting resins, photocurable resins, and electron beam curable resins. Resins have, for example, C-H bonds or Si-O bonds. Examples of transparent thermoplastic resins include cellulose-based resins such as triacetyl cellulose (TAC), and transparent resins such as polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, polysulfones, polystyrenes, polynorbornenes, polyolefins, (meth)acrylics, and acetates. Examples of thermosetting resins include epoxy resins, phenolic resins, and polyester resins. Examples of photocurable resins include monomers (including oligomers) having a vinyl group, an acrylate group (including a methacrylate group), an epoxy group, an isocyanate group, or an oxetane group. Specific examples of the monomer include urethane acrylate, epoxy acrylate, ester acrylate, epoxy, and vinyl ether monomers.

[0033] The first optical sheet 10 and the second optical sheet 30 are selected taking into consideration their reactivity with the molecular adhesive 20. That is, the materials of the first optical sheet 10 and the second optical sheet 30 are selected so that at least the flat portion 10s of the first main surface 12s and the third main surface 32s can form covalent bonds via the molecular adhesive 20. If necessary, at least the flat portion 10s of the first main surface 12s and / or the third main surface 32s may be surface-modified (e.g., by introducing hydroxyl groups by corona treatment). Furthermore, the flatness of the flat portion 10s of the first main surface 12s and the third main surface 32s is preferably 20 nm or less, more preferably 10 nm or less, and even more preferably 5 nm or less, as measured by atomic force microscopy. For example, the surface roughness Ra of the flat portion of the shaped film used in the examples was approximately 3.9 nm, and the surface roughness Ra of the flat resin film was approximately 1.5 nm. As an example of the second optical sheet 30, a resin film having a flat third main surface 32s is given, but at least the portion of the third main surface 32s that faces the flat portion 10s of the first main surface and forms a covalent bond via the molecular adhesive 20 must have the above-mentioned flatness.

[0034] The molecular adhesive 20 has a first reactive group RG1 capable of forming a covalent bond with the flat portion 10s of the first major surface 12s of the first optical sheet 10, and a second reactive group RG2 capable of forming a covalent bond with the third major surface 32s of the second optical sheet 30. The first reactive group RG1 and the second reactive group are different from each other. Individual molecules constituting the molecular adhesive 20 may be referred to as adhesive molecules 20. Furthermore, the molecular adhesive 20 or adhesive molecules 20 may be referred to as the molecular adhesive 20 or adhesive molecules 20 regardless of whether they are in a state before or after forming covalent bonds with the first optical sheet 10 and the second optical sheet 30. However, the molecular adhesive 20 may contain components other than adhesive molecules (e.g., a polymerization initiator).

[0035] As described above, when an adhesive molecule 20 has a first reactive group RG1 capable of forming a covalent bond with the flat portion 10s of the first main surface 12s of the first optical sheet 10 and a second reactive group RG2 capable of forming a covalent bond with the third main surface 32s of the second optical sheet 30, the flat portion 10s of the first main surface 12s of the first optical sheet 10 and the third main surface 32s of the second optical sheet 30 are bonded by a covalent bond formed between one adhesive molecule 20, the first reactive group RG1 possessed by this adhesive molecule 20, and the flat portion 10s, and a covalent bond formed between the second reactive group RG2 possessed by this adhesive molecule 20 and the third main surface 32s.

[0036] When the first reactive group RG1 or the second reactive group RG2 can react with itself to form a covalent bond (e.g., when second reactive groups RG2 can react with each other to form a covalent bond), multiple adhesive molecules 20 can be present in the covalent bond between the flat portion 10s of the first main surface 12s of the first optical sheet 10 and the third main surface 32s of the second optical sheet 30. For example, when the adhesive molecules 20 have multiple silanol groups and / or alkoxysilyl groups, the adhesive molecules 20 can form covalent bonds by reaction between the silanol groups and / or alkoxysilyl groups. In this case, for example, several tens to several hundreds of molecular layers of the adhesive molecules 20 can be present in the covalent bond between the flat portion 10s of the first main surface 12s and the third main surface 32s of the second optical sheet 30. Of course, the minimum number of adhesive molecules 20 intervening in the covalent bond between the flat portion 10s of the first major surface 12s and the third major surface 32s of the second optical sheet 30 may be a monolayer (thickness of about 1 nm).

[0037] That is, the distance between the flat portion 10s of the first major surface 12s of the first optical sheet 10 and the third major surface 32 of the second optical sheet 30 is approximately 1 nm or more, preferably approximately 500 nm or less, and more preferably approximately 100 nm or less. The molecular adhesive 20 contains a large number of adhesive molecules 20 that form such covalent bonds, but does not necessarily form a dense layer of adhesive molecules 20. If there are few reaction sites that form covalent bonds on the flat portion 10s of the first major surface 12s and the third major surface 32, the adhesive molecules 20 may be present sparsely.

[0038] Furthermore, the first reactive group RG1 of the adhesive molecule 20 may form a covalent bond with both the flat portion 10s of the first main surface 12s of the first optical sheet 10 and the third main surface 32s of the second optical sheet 30. In this case, the adhesive molecule (hereinafter referred to as the first adhesive molecule) 20 that forms a covalent bond with the flat portion 10s of the first main surface 12s of the first optical sheet 10 via the first reactive group RG1, and the adhesive molecule (hereinafter referred to as the second adhesive molecule) 20 that forms a covalent bond with the third main surface 32s of the second optical sheet 30 via the first reactive group RG1, form a covalent bond between the second reactive group RG2 of the first adhesive molecule and the second reactive group RG2 of the second adhesive molecule, thereby bonding the flat portion 10s of the first main surface 12s of the first optical sheet 10 and the third main surface 32s of the second optical sheet 30 by a covalent bond. In this case, two adhesive molecules 20 are present between the flat portion 10s of the first major surface 12s of the first optical sheet 10 and the third major surface 32s of the second optical sheet 30. Furthermore, as described above, when the first reactive group RG1 or the second reactive group RG2 can react with itself to form a covalent bond, one or more third adhesive molecules that are neither the first adhesive molecule nor the second adhesive molecule can be present in the covalent bond between the flat portion 10s of the first major surface 12s of the first optical sheet 10 and the third major surface 32s of the second optical sheet 30. Therefore, the distance between the flat portion 10s of the first major surface 12s of the first optical sheet 10 and the third major surface 32s of the second optical sheet 30 is approximately 2 nm or more, preferably approximately 500 nm or less, and more preferably 100 nm or less.

[0039] The adhesive molecule 20 has at least one reactive group selected from the group consisting of, for example, an azide group, an amino group, a mercapto group, an isocyanate group, a ureido group, an epoxy group, a silanol group, and an alkoxysilyl group. The alkoxysilyl group generates a silanol group by hydrolysis. The molecular adhesive 20 has, for example, an azide group as the first reactive group RG1 (or the second reactive group RG2) and a silanol group or an alkoxysilyl group as the second reactive group RG2 (or the first reactive group RG1). The adhesive molecule 20 further has, for example, a triazine ring, and the azide group is bonded to the triazine ring. When the first reactive group RG1 is an azide group or an amino group and the second reactive group RG2 is a silanol group or an alkoxysilyl group, the first reactive group may form a covalent bond with the surfaces of the first and second optical sheets, and the second reactive groups may form a covalent bond with each other.

[0040] For example, compounds (molecular adhesives, adhesive molecules) described in Japanese Patent No. 5083926, Japanese Patent No. 6452919, or Japanese Patent No. 6674594 can be suitably used. The entire disclosures of Japanese Patent No. 5083926, Japanese Patent No. 6452919, or Japanese Patent No. 6674594 are incorporated herein by reference.

[0041] The adhesive molecule 20 described in Japanese Patent No. 5,083,926 is represented by, for example, the following general formula [I]. [wherein E is any group; F is an OH group or an OH-yielding group; -Q is -N ３ or -NR １ (R ２ ) -NR １ (R ２ ) R １、 R ２ is H, a hydrocarbon group having 1 to 24 carbon atoms, or -RSi(R')n(OA)3-n (R is a chain hydrocarbon group having 1 to 12 carbon atoms. R' is a chain hydrocarbon group having 1 to 4 carbon atoms. A is H or a chain hydrocarbon group having 1 to 4 carbon atoms. n is an integer from 0 to 2.) R １ and R ２ may be the same or different.]

[0042] Among the adhesive molecules 20 having the triazine ring represented by the general formula [I], adhesive molecules 20 having an azide group and a silanol group or an alkoxysilyl group are preferred. The azide group of this adhesive molecule 20 is bonded to the triazine ring.

[0043] The adhesive molecule has an alkoxysilyl group and an azide group, and further has a triazine ring. The azide group is preferably directly bonded to the triazine ring (C atom). The number of azide groups bonded to the triazine ring is, for example, one or two. The OH group or OH-yielding group (e.g., alkoxysilyl group) is preferably indirectly bonded to the triazine ring (C atom) via a spacer (e.g., amino group, oxy group, and / or hydrocarbon group). The number of indirectly bonded alkoxysilyl groups is one or more.

[0044] Azide groups bonded to triazine rings (electron-localized conjugated skeletons) have high decomposition energy to form nitrenes. Therefore, they are less susceptible to near-ultraviolet and visible light. This improves the workability of UV exposure. Nitrenes bonded to triazine rings are more stable than nitrenes that are not. Bonding between nitrenes is suppressed. Hydrogen abstraction activity for C-H bonds and addition activity for unsaturated bonds are enhanced. In other words, effective reactions are possible with a small amount of exposure.

[0045] The alkoxysilyl group is bonded to the triazine ring (electron-localized conjugated skeleton) via a spacer (e.g., an amino group, an oxy group, and / or a hydrocarbon group). Therefore, when the adhesive molecule bonds to the resin surface, the entropy effect for forming a chemical bond is enhanced upon contact with another resin surface. The enhanced entropy effect increases the frequency factor term in the interfacial reaction after contact between the resin surfaces (the surface of the first optical sheet and the surface of the second optical sheet). As a result, the opportunity for the interfacial reaction increases. The length of the spacer is reflected in the increase in the frequency factor in the interfacial reaction. However, if the spacer length is too long, costs increase. Furthermore, the amount of adhesive molecule adsorption decreases. Therefore, a spacer of an appropriate length is preferred. From this perspective, adhesive molecules represented by the following general formulas [Io], [Ia], and [Ib] are preferred.

[0046] From the viewpoint of increasing the frequency factor in the interfacial reaction, the number of alkoxysilyl groups and azide groups present in one molecule is preferable. However, from the viewpoint of cost, there are limitations on the number. In other words, adhesive molecules represented by the above general formulas [Io], [Ia], and [Ib] are preferred.

[0047] The alkoxysilyl groups in the general formulas [Io], [Ia], and [Ib] are, in most cases, OH-yielding groups (OH precursors). To convert the OH-yielding groups to OH groups, they are treated with, for example, water (neutral water, acidic water, or alkaline water). Corona discharge treatment and plasma treatment are also possible. However, water treatment is preferred.

[0048] The adhesion treatment (surface treatment: modification treatment) of the optical sheets (first optical sheet and / or second optical sheet) can be carried out, for example, as follows.

[0049] First, a treatment liquid (solution or dispersion) containing adhesive molecules is prepared. Examples of solvents that can be used include water, alcohols (e.g., methanol, ethanol, isopropanol, ethylene glycol, propylene glycol, cellosolve, and carbitol), ketones (e.g., acetone, methyl ethyl ketone, and cyclohexanone), aromatic hydrocarbons (e.g., benzene, toluene, and xylene), aliphatic hydrocarbons (e.g., hexane, octane, decane, dodecane, and octadecane), esters (e.g., ethyl acetate, methyl propionate, and methyl phthalate), and ethers (e.g., tetrahydrofuran, ethyl butyl ether, and anisole). A mixture of different types of adhesive molecules may also be used. The adhesive molecule content is 0.0001 to 10% by mass. A content of 0.001 to 2% by mass is particularly preferred. This is because too little adhesive molecule content results in poor effectiveness. Conversely, the amount of adhesive molecule that can react with the optical sheet is limited, and too much adhesive molecule content is of little use. From this perspective, the above ratios are preferred.

[0050] A surfactant may be added to the treatment liquid as needed to adjust the surface tension, such as a nonionic surfactant (e.g., a nonionic surfactant composed of a long alkyl chain and polyethylene glycol), a cationic surfactant (e.g., a quaternary ammonium salt), or an anionic surfactant (e.g., an organic carboxylate or sulfonate).

[0051] The optical sheet is immersed in the treatment liquid, or the treatment liquid is sprayed onto the optical sheet, causing adhesive molecules (molecular adhesive) to adhere to the surface of the optical sheet.

[0052] After this, light (ultraviolet rays) is irradiated. In particular, light is irradiated only at the locations where the adhesive molecules are to be bonded to the optical sheet. For this purpose, a mask with an appropriate pattern is used. The azide groups of the adhesive molecules are decomposed by the ultraviolet irradiation. The decomposition of the azide groups produces nitrenes. These nitrenes react with functional groups (e.g., -CH) on the surface of the optical sheet. ３ , -CH ２The irradiated areas attack the -, -CH<, -CH=CH-). This causes a hydrogen abstraction radical addition or radical addition reaction, resulting in chemical bonding between the adhesive molecules and the optical sheet surface. No chemical bonding occurs in unirradiated areas.

[0053] For ultraviolet irradiation, a UV irradiation device (for example, a high-pressure mercury UV lamp, a low-pressure mercury UV lamp, a fluorescent UV lamp (short ARC xenon lamp, chemical lamp), or a metal halide lamp) is used. Ultraviolet light of 200 to 450 nm is irradiated. If the amount of irradiation light is too small, the reaction does not proceed easily. Conversely, if the amount of irradiation light is too large, there is a risk of deterioration of the optical sheet. Therefore, the preferred amount of irradiation light (light source wavelength: 254 nm) is 1 mJ / cm. ２ ~5 J / cm ２ More preferably, 5 mJ / cm ２ ~1 J / cm ２ is.

[0054] When the optical sheet has a complex shape, the use of a reflector is effective in uniformly irradiating the optical sheet with UV light. Examples of the reflector include a mirror, a surface-polished metal foil, an Al mirror foil, a SUS mirror foil, and a silver-plated mirror plate. The shape, dimensions, material, etc. of the reflector are appropriately selected from the viewpoint of reflection efficiency.

[0055] The optical laminate 100 can be manufactured, for example, by the following manufacturing method. The manufacturing method according to an embodiment of the present invention includes: Step A: applying adhesive molecules 20, for example, represented by the above general formula [I], to at least one of the flat portion 10s of the first optical sheet 10 and the third major surface 32s of the second optical sheet 30; Step B: irradiating the adhesive molecules 20 with light after Step A; and Step C: heating while applying pressure with the flat portion 10s and the third major surface 32s facing each other. In Step C, the laminate is heated, for example, to a temperature of 60°C or higher and 150°C or lower, more preferably 80°C or higher and 110°C or lower. The pressure applied is, for example, 0.01 MPa or higher and 50 MPa or lower, preferably 0.1 MPa or higher and 5 MPa or lower. The pressure application time is, for example, 0.1 minute or higher and 200 minutes or lower. The heating temperature and / or heating time are set taking into consideration the heat resistance of the first optical sheet 10 and the second optical sheet 30.

[0056] As the adhesive molecules, the adhesive molecules (molecular adhesive M) described in Japanese Patent No. 6674594 can also be used.

[0057] The adhesive molecule (molecular adhesive M) has an amino group (-NH ２ ), at least one reactive group (Zα) selected from the group consisting of an azide group, a mercapto group, an isocyanate group, a ureido group, and an epoxy group, and at least one reactive group (Zβ) selected from the group consisting of a silanol group and a group that generates a silanol group by hydrolysis. The reactive group (Zα) is an amino group (-NH ２ ) or an azide group is preferred. Adhesive molecules containing an azide group are similar to the adhesive molecules described in Japanese Patent No. 5,083,926, and therefore, the following description will be focused on an embodiment in which adhesive molecules having an amino group are used.

[0058] The reactive group (Zα) in the adhesive molecule is a thermoplastic resin (P １ ) can form a chemical bond with the reactive partial structure (Zγ) of the thermoplastic resin (P). It is believed that this chemical bond chemically fixes the adhesive molecules to the surface of the optical sheet. The chemical bond is preferably a covalent bond. １ ) is, for example, at least one selected from the group consisting of olefin resins, cycloolefin resins, acrylic resins, olefin-vinyl acetate resins, olefin ionomer resins, and polyester resins.

[0059] The reactive group (Zβ) in the adhesive molecule forms a chemical bond with the surface of the other optical sheet (the second or first optical sheet). The surface of the other optical sheet preferably has a hydroxyl group (hydroxy group) or a carboxyl group (—COOH). Hydroxyl groups or carboxyl groups can be introduced by subjecting the other optical sheet, which is made of a thermoplastic resin or a thermosetting resin, to a surface treatment. Examples of surface treatments include corona treatment, plasma treatment, ultraviolet irradiation treatment, electron beam irradiation treatment, ozone treatment, excimer ultraviolet treatment, acid treatment, and base treatment.

[0060] Examples of groups that generate silanol groups through hydrolysis include Si—X １ Examples of the group include a group having a partial structure represented by the following formula: X １ Examples of the hydrolyzable group include alkoxy groups having 1 to 10 carbon atoms, such as a methoxy group, an ethoxy group, an n-propoxy group, and an isopropoxy group; and halogen atoms, such as a fluorine atom, a chlorine atom, and a bromine atom.

[0061] The thickness of the molecular adhesive applied to the optical sheet is preferably 200 nm or less, more preferably 150 nm or less, even more preferably 100 nm or less, and particularly preferably 50 nm or less. The thickness of the molecular adhesive is preferably 0.5 nm or more, more preferably 1 nm or more.

[0062] On the other hand, the flat portion 10s of the first main surface 12s and the third main surface 32s have, for example, a hydrocarbon group (C—H group), a carbonyl group (—(C(═O)— group), a carboxyl group, and / or a hydroxyl group (OH group), which form covalent bonds with the adhesive molecules 20. For example, after ultraviolet irradiation, the azide group of the adhesive molecule 20 forms a covalent bond with the hydrocarbon group of the flat portion 10s of the first main surface 12s or the third main surface 32s, the amino group forms a covalent bond with the carbonyl carbon, and the alkoxysilyl group forms a covalent bond with the hydroxyl group. The amino group forms a covalent bond with a hydroxyl group or a carboxyl group.

[0063] The molecular adhesive can be applied to the optical sheet, for example, as follows: For example, a molecular adhesive solution containing the molecular adhesive (M) is prepared, the solution is applied to the optical sheet, and then the resulting coating film is dried and the molecular adhesive is fixed to the optical sheet.

[0064] The solvent used in preparing the molecular adhesive solution is not particularly limited. Examples of the solvent include alcohol-based solvents such as methanol, ethanol, isopropanol, ethylene glycol, and diethylene glycol; ketone-based solvents such as acetone and methyl ethyl ketone; ester-based solvents such as ethyl acetate and butyl acetate; halogen-containing compound-based solvents such as methylene chloride; aliphatic hydrocarbon-based solvents such as butane and hexane; ether-based solvents such as tetrahydrofuran and butyl ether; aromatic compound-based solvents such as benzene and toluene; amide-based solvents such as N,N-dimethylformamide and N-methylpyrrolidone; and water. These may be used alone or in combination of two or more.

[0065] The concentration of the molecular adhesive (adhesive molecules) in the molecular adhesive solution is not particularly limited. The concentration is preferably 0.005 to 1.000 mol / L, more preferably 0.050 to 0.500 mol / L. By setting the concentration of adhesive molecules to 0.005 mol / L or more, the molecular adhesive can be efficiently applied to the optical sheet. Furthermore, by setting the concentration to 1.000 mol / L or less, unintended reactions of the molecular adhesive solution can be suppressed, resulting in excellent solution stability.

[0066] The method for applying the molecular adhesive solution is not particularly limited, and any known application method can be used, such as spin coating, spray coating, bar coating, knife coating, roll knife coating, roll coating, blade coating, dip coating, curtain coating, die coating, and gravure coating, with bar coating and gravure coating being preferred.

[0067] After applying the molecular adhesive solution, the resulting coating is typically dried by natural drying or by being placed in a drying mechanism. Among these, drying by being placed in a drying mechanism is preferred from the viewpoint of improving productivity. Examples of drying mechanisms include batch-type drying mechanisms such as air ovens, as well as continuous drying mechanisms such as heat rolls and hot air-through mechanisms (equipment in which the object to be dried moves through an open-type drying oven while being heated and dried while being exposed to blown air). Devices that can be used as part of these drying mechanisms, such as high-frequency heaters, heat medium circulating heaters such as oil heaters, and heaters themselves such as far-infrared heaters, can also be used as drying mechanisms. Among these, hot air-through mechanisms are preferred from the viewpoint of improving productivity. The drying temperature adjusted by the drying mechanism is typically 20 to 250°C, preferably 25 to 200°C, more preferably 30 to 150°C, and particularly preferably 35 to 120°C. The drying time is typically 1 second to 120 minutes, preferably 10 seconds to 10 minutes, more preferably 20 seconds to 5 minutes, and particularly preferably 30 seconds to 3 minutes.

[0068] Next, a process for fixing the molecular adhesive to the optical sheet (hereinafter sometimes referred to as a fixing process) is performed. The fixing process can be appropriately selected depending on the characteristics of the reactive group (Zα) of the molecular adhesive. Typically, chemical bonds are formed by applying the molecular adhesive to the optical sheet, and heating promotes the formation of chemical bonds. Therefore, a heat treatment is preferable from the viewpoint of improving productivity. The heating temperature is typically 40 to 250°C, preferably 60 to 200°C, and more preferably 80 to 120°C. The heating time is typically 1 second to 120 minutes, preferably 1 to 60 minutes, and more preferably 1 to 30 minutes. The heating method is not particularly limited, and mechanisms and devices similar to those used for the drying mechanism described above can be used.

[0069] The application of the molecular adhesive solution, the drying treatment, and the fixing treatment may be repeated multiple times.

[0070] 1, for simplicity, the molecular adhesive 20 is illustrated only between the flat portion 10s of the first major surface 12s and the third major surface 32s, but this is not limited thereto. For example, when the first optical sheet 10 is immersed in a treatment liquid (solution or dispersion) containing the molecular adhesive 20, the molecular adhesive 20 may adhere and remain over the entire first major surface 12s, i.e., not only on the flat portion 10s but also on the first inclined surface 16s and the second inclined surface 17s that form the recess 14. Furthermore, when the second optical sheet 30 is immersed in a treatment liquid containing the molecular adhesive 20, the molecular adhesive 20 may adhere and remain over the entire third major surface 32s.

[0071] Even if the molecular adhesive 20 remains, it is at most a monolayer of adhesive molecules 20, which is smaller than the wavelength of visible light (400 nm or more and less than 760 nm), and therefore has almost no effect on the optical properties. Furthermore, since the thickness (depth of the recesses) of the first optical sheet 10 is several μm or more, the molecular adhesive 20 is illustrated in FIG. 1 , but the physical length (thickness) of the molecular adhesive 20 is negligibly small. It is also possible to selectively apply a treatment liquid containing the molecular adhesive 20 only to the flat portion 10s by a method such as printing.

[0072] The molecular adhesive 20 present between the first optical sheet 10 and the second optical sheet 30 is at most two molecular layers thick, which is thinner than the wavelength of visible light and can therefore be considered optically non-existent. Therefore, by matching the refractive indices of the first optical sheet 10 and the second optical sheet 30, the first optical sheet 10 and the second optical sheet 30 can be bonded together without an optically non-existent interface. The difference (absolute value) in the refractive index between the first optical sheet 10 and the second optical sheet 30 is preferably 0.20 or less, more preferably 0.15 or less, and even more preferably 0.10 or less.

[0073] Next, the shape of the internal space 14a of the optical laminate 100 will be described with reference to FIG.

[0074] The optical laminate 100 has multiple internal spaces 14a. The multiple internal spaces 14a are defined by each of the multiple recesses 14 in the first major surface 12s of the first optical sheet 10a and the third major surface 32s of the second optical sheet. Although the molecular adhesive 20 is also shown in FIG. 2, the physical length (thickness) of the molecular adhesive 20 is negligibly small. Therefore, in the optical laminate 100, the adhesive does not penetrate into the recesses 14, as in the optical laminate 200 that uses a conventional adhesive layer (adhesive layer 20C in FIG. 3).

[0075] However, the second optical sheet 30 may deform due to the application of heat and pressure when adhering to the first optical sheet 10, and as shown in FIG. 2 , the second optical sheet 30 may intrude into the recess 14. In this case, if a second optical sheet 30 having sufficiently high rigidity under the adhering conditions is selected, the second optical sheet 30 can be prevented from intruding into the recess 14. Here, if the distance from the opening surface defined by the opening 14op of the recess 14 (the dashed line within the opening 14op of the recess 14 in FIG. 2 ) to the deepest part of the recess 14 is defined as A, and the point at which the distance from the opening surface to the third main surface 32 of the second optical sheet 30 that has intruded into the recess 14 reaches a maximum value B is defined as the deepest penetration point, B / A can be made 0.2 or less, as will be shown later in the examples. B / A is preferably 0.15 or less, more preferably 0.10 or less, and even more preferably 0.05 or less.

[0076] Furthermore, since the second optical sheet 30 enters the recess 14 due to bending of the second optical sheet 30, the third major surface 32s has a shape that is convex toward the bottom of the recess 14, as shown in the figure. Therefore, if the point at which the distance from the opening surface to the third major surface 32 of the second optical sheet 30 that has entered the recess 14 reaches a maximum value B is defined as the deepest point, the deepest point will be located on the deepest side of the first inclined surface 16s and the second inclined surface 17s of the recess 14. In other words, even if the second optical sheet 30 enters the recess 14, the second optical sheet 30 hardly comes into contact with the first inclined surface 16s and / or the second inclined surface 17s of the recess 14, and the area of ​​the first inclined surface 16s and / or the second inclined surface 17s that form the interface causing total internal reflection in the internal space 14a is not reduced.

[0077] As described above, according to an embodiment of the present invention, the degree to which the second optical sheet 30 penetrates into the recess 14 can be sufficiently suppressed, and the shape of the internal space 14a can be made substantially equal to the shape of the recess 14, thereby achieving the optical characteristics (e.g., light distribution characteristics) as designed.

[0078] It is preferable to select a second optical sheet 30 with a rigidity that prevents the second optical sheet 30 from penetrating the recesses 14, given the type of molecular adhesive and the bonding conditions. Even if the second optical sheet 30 does not penetrate the recesses 14, the recesses 14 may deform if the heat resistance of the first optical sheet 10 is insufficient. Deformation of the recesses 14 prevents the desired optical properties from being obtained. Therefore, it is preferable to select a first optical sheet 10 with a rigidity (heat resistance) that prevents deformation of the recesses 14, given the type of molecular adhesive and the bonding conditions. The first optical sheet 10 is preferably formed from a cured product of a curable resin. A cured product of a curable resin has a crosslinked structure and is therefore less susceptible to thermal deformation. Therefore, deformation of the recesses 14 of the first optical sheet 10 can be suppressed when heated and pressurized during bonding to the second optical sheet 30 via the molecular adhesive. The recesses 14 may be formed by conducting preliminary experiments to predict deformation during bonding.

[0079] Fig. 3 shows a schematic cross-sectional view of an optical laminate 200 produced using the adhesive layer 20C. Note that the second optical sheet 30 on the adhesive layer 20C is not shown in Fig. 3. The thickness of the adhesive layer 20C is generally 1 µm or more, typically 4 µm or more, which is 10 times or more thicker than the thickness of the molecular adhesive 20.

[0080] 3, when adhesive layer 20C is used, surface 28Cs of adhesive layer 20C on the first optical sheet 10 side penetrates into recesses 14. For example, when a general thermosetting adhesive is used, the adhesive is heated and pressurized during lamination, and the adhesive softens, causing the adhesive to penetrate into recesses 14. Also, when a pressure-sensitive adhesive (pressure-sensitive adhesive) is used, the pressure applied during lamination causes the pressure to penetrate into recesses 14 because the pressure-sensitive adhesive has low rigidity.

[0081] The lower surface 28Cs of the adhesive layer 20C that has penetrated into the recess 14 has a concave shape toward the bottom of the recess 14. This is due to the cohesive force (surface tension) of the softened adhesive (or pressure-sensitive adhesive), and is in contrast to the third main surface 32s of the second optical sheet 30 shown in FIG. 2 , which has a convex shape toward the bottom of the recess 14. Therefore, when the adhesive layer 20C is bonded together, if the distance A from the opening surface defined by the opening 14op of the recess 14 to the deepest part of the recess 14 is defined as a distance A, and the point at which the distance B from the opening surface to the lower surface 28Cs of the adhesive layer 20C that has penetrated into the recess 14 is the maximum distance B is defined as the deepest penetration point, the deepest penetration point is the point at which the adhesive layer comes into contact with the first inclined surface 16s or the second inclined surface 17s of the recess 14, and the maximum distance B to the lower surface 28Cs is either the distance B1 to the first inclined surface 16s or the distance B2 to the second inclined surface 17s in FIG. 3 .

[0082] When adhesive layer 20C is used in this manner, the maximum distance B to lower surface 28Cs is the distance B1 to first inclined surface 16s or the distance B2 to second inclined surface 17s, so unlike the optical laminate 100 of the embodiment described with reference to Figure 2, the area of ​​the first inclined surface 16s and / or the second inclined surface 17s that form the interface causing total internal reflection in internal space 14Ca is reduced.

[0083] Furthermore, the degree of penetration into the recess 14 depends on the type of adhesive and the bonding conditions (temperature, pressure, and time), but it is difficult to keep the degree of penetration low. The concave shape of the lower surface 28Cs of the adhesive layer 20C depends on the shape of the recess 14 and the method of applying pressure during bonding (the direction of stress acting on the adhesive). However, it is generally asymmetric, with greater penetration occurring at smaller inclination angles (the angle of the first major surface 12s of the first optical sheet 10 relative to the flat portion 10s). Therefore, if the point at which the distance from the opening to the lower surface 28Cs of the adhesive layer 20C that has penetrated into the recess 14 reaches its maximum value B is defined as the deepest penetration point, the deepest penetration point is the point at which the adhesive layer makes contact with the first inclined surface 16s of the recess 14, and the maximum value B is B1 in FIG. 3 . Of course, B2 may be greater than B1, and B2 may become the maximum value B, or B1 may equal B2. In either case, it is difficult to achieve a ratio B / A of 0.1 or less. FIG. 3 shows an example where B / A=approximately 0.4 (see Comparative Example 1 described later).

[0084] Therefore, as shown in Figure 3, the size and shape of the internal space 14Ca defined by the recess 14 and the adhesive layer 20C will deviate significantly from the recess 14, and the optical characteristics (e.g., light distribution characteristics) will deviate significantly from the design.

[0085] The first optical sheet 10 may be, for example, the optical sheet 10a shown in FIGS. 4A and 4B. An optical sheet 10a having a concave-convex structure (plurality of recesses 14) on its surface is sometimes referred to as a shaped film 10a. An optical laminate 100 including the shaped film 10a functions as the light distribution structure described in Patent Document 2 or Patent Document 3. For example, when a light source (e.g., an LED device) is disposed on the side surface (e.g., the left side in FIG. 1 ) of the second optical sheet 30 and the second optical sheet 30 is used as a light guide layer, light propagating in the −Y direction within the second optical sheet 30 is totally internally reflected by the multiple internal spaces 14a and directed toward the Z direction perpendicular to the XY plane. An additional light guide layer may be provided on the fourth major surface 38s of the second optical sheet 30, or the first optical sheet 10 or the optical laminate 100 may be used as the light guide layer. A light guide plate including the optical laminate 100 may have various forms. Thus, a light guide including the optical laminate 100 may be used in various lighting devices.

[0086] As shown in FIG. 4A, when the shaped film 10a is viewed from the normal direction of the first main surface 12s, the plurality of recesses 14 are arranged in a discrete island-like pattern in both the X and Y directions. In the shaped film 10a, the size of the recesses 14 (length L, width W: see FIGS. 4A and 4B) is, for example, preferably 10 μm or more and 500 μm or less, and preferably 1 μm or more and 100 μm or less. From the viewpoint of light extraction efficiency, the depth A is preferably 1 μm or more and 100 μm or less. The depth A of the recesses 14 is preferably 20 μm or less, more preferably 12 μm or less. The depth A of the recesses 14 is preferably 4 μm or more, more preferably 6 μm or more, and more preferably 8 μm or more. When the plurality of recesses 14 are distributed discretely and uniformly, they may be arranged periodically, for example, as shown in FIG. 4A. The pitch Px is, for example, not less than 10 μm and not more than 500 μm, and the pitch Py is, for example, not less than 10 μm and not more than 500 μm.

[0087] The density of the plurality of recesses 14 is preferably 0.3% or more when the shaped film 10a is viewed from the normal direction of the main surface. The ratio of the area of ​​the plurality of recesses 14 to the area of ​​the shaped film 10a (occupancy rate) is preferably 0.3% or more from the viewpoint of obtaining good brightness. The occupation rate of the plurality of recesses 14 is appropriately selected depending on the application. For example, in applications requiring transparency, it is preferably 30% or less to obtain good visible light transmittance and haze value, and it is preferably 1% or more from the viewpoint of obtaining good brightness. The upper limit is more preferably 25% or less, and to obtain high visible light transmittance, it is preferably 10% or less, and more preferably 5% or less. For example, it is preferably 0.3% or more and 10% or less, and more preferably 0.5% or more and 4% or less. In applications requiring higher brightness, it is preferably 30% or more and 80% or less. The occupation rate of the plurality of recesses 14 may be uniform, or the occupation rate may increase as the distance from the light source increases so that the brightness does not decrease even with increasing distance.

[0088] The inclination angle θa of the first inclined surface 16s is, for example, 10° or more and 70° or less. The lower limit is preferably 30° or more, more preferably 45° or more. If the inclination angle θa is smaller than 10°, the controllability of the light distribution may decrease, and the light extraction efficiency may also decrease. On the other hand, if the inclination angle θa exceeds 70°, for example, processing of the shaped film may become difficult. Furthermore, the inclination angle θb of the second inclined surface 17s is, for example, 50° or more and 100° or less. The lower limit is preferably 70° or more. If the inclination angle θb is smaller than 50°, stray light may be generated in an unintended direction. On the other hand, if the inclination angle θb exceeds 100°, for example, processing of the shaped film may become difficult. The inclination angle θa of the first inclined surface 16s and the inclination angle θb of the second inclined surface 17s are angles relative to a direction parallel to the Y direction in the cross section of the recess 14 (a cross section perpendicular to the X direction and parallel to the YZ plane). In this example, the inclination angle θa of the first inclined surface 16s is smaller than the inclination angle θb of the second inclined surface 17s. In a lighting device including the optical laminate 100, the first inclined surface 16s is positioned closer to the light source than the second inclined surface 17s. The cross-sectional shape of the internal space 14a (a cross-section perpendicular to the X direction and parallel to the YZ plane) is determined by the inclination angle θa of the first inclined surface 16s and the inclination angle θb of the second inclined surface 17s, the width W, and the depth A. The shape of the internal space 14a (recess 14) is not limited to the illustrated example and can be modified in various ways. The distribution (light distribution) of light rays emitted from the optical laminate 100 can be adjusted by adjusting the shape, size, arrangement density, etc. of the internal space 14a (recess 14) (see, for example, Patent Documents 2 and 3).

[0089] Although an example in which the cross-sectional shape of the recess 14 is triangular has been shown, the cross-sectional shape of the recess 14 is not limited to this and may be, for example, a quadrangle (e.g., trapezoid) as long as it has a surface that can form an interface that directs light in the Z direction by total internal reflection. Furthermore, the cross-sectional shape is not limited to a polygon and may be a shape that includes a curve.

[0090] The optical laminate 100 may further include other optical sheets. When forming the shaped film 10a using a curable resin, for example, the curable resin is applied to a substrate layer (e.g., a transparent resin film such as a PMMA film), a concavo-convex structure is formed in the curable resin layer, and then the cured resin is cured to obtain the shaped film 10a formed from the cured product. In this case, the shaped film 10a is integrally formed on the substrate layer. In addition, the optical laminate 100 may further include, for example, a light-guiding layer, a light-diffusing layer, an anti-reflection layer, a low refractive index layer, a reflective layer, a hard coat layer, etc. The optical laminate 100 may also include an adhesive layer. The optical laminate 100 can be manufactured using, for example, a roll-to-roll method.

[0091] Examples and comparative examples are given below.

[0092] As the first optical sheet 10, a shaped film 10a having a concave-convex structure on its surface, as described with reference to Figures 4A and 4B, was produced according to the method described in JP-A-2013-524288. Specifically, the surface of a polymethyl methacrylate (PMMA) film was coated with lacquer (Finecure RM-64, manufactured by Sanyo Chemical Industries, Ltd., an acrylate-based photocurable resin), an optical pattern was embossed on the film surface containing the lacquer, and then the lacquer was cured (ultraviolet light irradiation conditions: D bulb, 1000 mJ / cm ２ 、 320 mW / cm ２ ) to produce a shaped film 10a having the desired uneven structure on its surface. The thickness of the shaped film 10a was 20 μm. The total thickness including the shaped film 10a and the PMMA film (base layer) was 60 μm, and the haze value was 3.2%. The shaped film 10a and the PMMA film (base layer) will be collectively referred to as resin film A.

[0093] This shaped film 10a has a plurality of recesses 14 with a triangular cross section, a length L of 80 μm, a width W of 17.3 μm, and a depth A of 10 μm, which are arranged at intervals of width E (260 μm) in the X-axis direction. Furthermore, a pattern of such recesses 14 is arranged at intervals of width D (160 μm) in the Y-axis direction. Px in FIG. 4A is 340 μm, and Py is 174 μm. The density of recesses 74 on the surface of the uneven shaped film is 2426 / cm. ２ 4B, the inclination angle θa was approximately 60°, and the inclination angle θb was 85°. The occupied area ratio of the recesses 14 was 3.4%.

[0094] A polymethyl methacrylate (PMMA) film (thickness: 30 μm) was used as the second optical sheet 30. This PMMA film will be referred to as resin film B.

[0095] A treatment liquid (solution) obtained by diluting 6-(3-triethoxysilylpropyl)amino-1,3,5-triazine-2,4-diazide (included in general formula Ia) purchased from Io Chemical Research Institute Co., Ltd. to 0.5% by mass with ethanol was used as the molecular adhesive 20. Io Chemical Research Institute Co., Ltd. is the patent holder of Patent No. 5083926.

[0096] An adhesive sheet for producing an optical laminate of a comparative example was produced as follows.

[0097] First, an acrylic polymer was prepared. Into a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser, 90.7 parts by mass of n-butyl acrylate (BA), 6.3 parts by mass of 4-acryloylmorpholine (ACMO), 2.7 parts by mass of acrylic acid (AA), 0.3 parts by mass of 4-hydroxybutyl acrylate (4HBA), and 0.1 parts by mass of 2,2'-azobisisobutyronitrile as a polymerization initiator were charged together with ethyl acetate so that the total monomer content was 50% by mass. Nitrogen gas was introduced while gently stirring to replace the atmosphere with nitrogen for 1 hour, and then the liquid temperature in the flask was maintained at around 58°C while the polymerization reaction was carried out for 8 hours, thereby obtaining an acrylic polymer. Here, after 2 hours had elapsed from the start of the polymerization reaction, ethyl acetate was added dropwise over 3 hours so that the solids content was 35% by mass. That is, the acrylic polymer was obtained as an acrylic polymer solution having a solids content of 35% by mass.

[0098] Subsequently, 0.15 parts by mass of a trimethylolpropane / tolylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, product name: Coronate L) as a crosslinking agent and 0.075 parts by mass of dibenzoyl peroxide (manufactured by Nippon Oil & Fats Corporation: Niper BMT40 (SV)) were blended with the obtained acrylic polymer solution per 100 parts by mass of the polymer to prepare an adhesive composition solution.

[0099] An adhesive composition solution was applied to one side of a silicone release-treated, 38 μm-thick polyethylene terephthalate (PET) film (trade name "MRF38", manufactured by Mitsubishi Chemical Corporation) to form an adhesive composition solution layer. The adhesive composition solution layer was applied so that the thickness after drying (i.e., the thickness of the adhesive composition layer) would be 5 μm. The adhesive composition solution layer was dried at 150°C for 3 minutes to remove the solvent from the adhesive composition solution layer and crosslink the acrylic polymer with the crosslinking agent, thereby obtaining an adhesive composition layer. The adhesive composition layer was then bonded to the release-treated surface of a silicone release-treated, 38 μm-thick polyethylene terephthalate (PET) film (trade name "MRE38", manufactured by Mitsubishi Chemical Corporation) to produce an adhesive sheet having a laminated structure of PET film / adhesive composition layer / PET film.

[0100] Example 1 Resin film A and resin film B were bonded together using the molecular adhesive described above.

[0101] A treatment solution containing a molecular adhesive was applied to the recessed surface of the shaping film 10a of the resin film A to a thickness of 16 μm. The surface was then dried at 80°C for 1 minute, and ultraviolet light was applied from the side where the molecular adhesive was applied. The ultraviolet light irradiation converted the azide group of the molecular adhesive to nitrene, which reacted with hydrocarbons (e.g., alkyl groups) on the surface of the resin film A to form covalent bonds. An LED lamp (manufactured by Quark Technology Co., Ltd., peak irradiance: 200 mW / cm) was used for ultraviolet light irradiation. ２ ) was used, and the cumulative light intensity was 100 mJ / cm ２ The film was irradiated with ultraviolet light so that the wavelength was 245 nm. The illuminance of the ultraviolet light was measured using a UV Power Puck (manufactured by Fusion UV Systems Japan Co., Ltd.). The thickness of the molecular adhesive was approximately 40 nm. The film thickness of the surface of the acrylic film coated with the molecular adhesive was measured by ellipsometry. The measurement wavelength range was 210 nm to 1690 nm using a light source, and measurements were made at angles of incidence of 60°, 70°, and 80°.

[0102] Resin film B was also prepared in the same manner as resin film A, except that a molecular adhesive was applied to the surface of resin film B to a thickness of about 40 nm, and the adhesive was allowed to react.

[0103] Resin film A and resin film B were placed with the molecular adhesive bonded surfaces facing each other, and then heated and pressurized for 5 minutes at 100°C and 0.5 MPa using a precision press. This heating and pressurization caused the alkoxysilyl groups in the molecular adhesive to hydrolyze, generating silanol groups that reacted with each other to form covalent bonds.

[0104] Example 2 An optical laminate was produced in the same manner as in Example 1, except that the temperature during heating and pressing was 110°C.

[0105] [Comparative Example 1] One of the release-treated PET films was peeled off from the above adhesive sheet, and the exposed adhesive composition layer was bonded to resin film B (thickness: 20 μm).The other separator (PET film) was then peeled off and the layer was bonded to the uneven surface of the shaped film 10a of resin film A at a pressure of 0.05 MPa, thereby obtaining an optical laminate having a laminated structure of resin film B / adhesive composition layer / resin film A.

[0106] The optical laminate thus obtained was subjected to the following evaluations. The results are shown in Table 1.

[0107]

[0108] <Shape of Internal Space> The depth A and maximum penetration B of the recess 14 were determined from cross-sectional SEM images of the optical laminate. For each optical laminate, A and B were determined from cross-sectional images of multiple arbitrarily selected locations, and the averages are shown in Table 1.

[0109] The shape of the internal space in the optical laminate of Example 1 was similar to that of internal space 14a shown in FIG. 1 , with the second optical sheet 30 not invading the recess 14 and maintaining the shape of the recess 14 as it was. On the other hand, the shape of the internal space in the optical laminate of Example 2, which was pressurized at a higher temperature than that of the optical laminate of Example 1, was the same as that of internal space 14a shown in FIG. 2 , with the second optical sheet 30 slightly invading the recess 14. B / A was approximately 0.1, a sufficiently small value of 0.2 or less. The internal space in the optical laminate of Comparative Example 1 had the same shape as internal space 14Ca shown in FIG. 3 , with the maximum intrusion value B being B1 and a large value of approximately 0.4.

[0110] <Bending Adhesion> Curved surface conformability was evaluated by attaching the laminate to the curved surface (width 30 mm × length 80 mm) of a cylindrical polymethyl methacrylate test piece with an outer diameter of 90 mm, leaving it at room temperature for 5 days, and evaluating lifting and peeling. Furthermore, after leaving it in an environment of 23°C and 65% RH for 7 days, it was also left in an environment of 85°C and 85% RH for 1000 hours, and evaluating lifting and peeling. It was found that all of the optical laminates of Examples 1 and 2 and Comparative Example 1 had sufficient bending adhesion.

[0111] <Haze Value> The haze value of each optical laminate was measured under D65 light using a haze meter (device name "HZ-1", manufactured by Suga Test Instruments Co., Ltd.) The haze value of each optical laminate showed a slight increase from the haze value of 3.2% of the shaped film.

[0112] The optical laminate according to the embodiment of the present invention is widely used in optical devices such as display devices and lighting devices.

[0113] 10, 10a: first optical sheet, 12s: first main surface, 18s: second main surface, 20: molecular adhesive (adhesive molecules), 30: second optical sheet, 32s: third main surface, 38s: fourth main surface, 100, 200: optical laminate

Claims

1. a first optical sheet having a first main surface having a concave-convex structure and a second main surface opposite to the first main surface; a second optical sheet having a third main surface disposed on the first main surface side of the first optical sheet, the concave-convex structure of the first main surface includes a plurality of concave portions and a flat portion between two adjacent concave portions of the plurality of concave portions, An optical laminate, wherein the flat portion of the first main surface and the third main surface are covalently bonded via a molecular adhesive.

2. 2. The optical laminate of claim 1, wherein, for each of the plurality of recesses, the distance from the opening surface defined by the opening of the recess to the deepest part of the recess is defined as A, and the point at which the distance from the opening surface to the third main surface of the second optical sheet that has penetrated into the recess is at its maximum value B is defined as the deepest penetration point, and B / A is 0.2 or less.

3. The optical laminate according to claim 2 , wherein the deepest penetration point is located closer to the deepest portion than the side surface of the recess.

4. The optical laminate according to claim 1 , wherein the distance from the flat portion to the third main surface does not exceed 500 nm.

5. a first optical sheet having a first main surface having a concave-convex structure and a second main surface opposite to the first main surface; a second optical sheet having a third main surface disposed on the first main surface side of the first optical sheet, the concave-convex structure of the first main surface includes a plurality of concave portions and a flat portion between two adjacent concave portions of the plurality of concave portions, for each of the plurality of recesses, a distance from an opening surface defined by the opening of the recess to a deepest portion of the recess is defined as A, and a point at which a distance from the opening surface to the third main surface of the second optical sheet that has penetrated into the recess takes a maximum value of B is defined as a deepest penetration point, and B / A is 0.2 or less; An optical laminate, wherein the distance from the flat portion to the third main surface does not exceed 500 nm.

6. The optical laminate according to claim 5 , wherein the flat portion of the first main surface and the third main surface are covalently bonded via a molecular adhesive.

7. The molecular adhesive has at least one reactive group selected from the group consisting of an azide group, an amino group, a mercapto group, an isocyanate group, a ureido group, an epoxy group, a silanol group, and an alkoxysilyl group. The optical laminate according to any one of claims 1 to 3.

8. The optical laminate according to claim 1 , wherein the molecular adhesive has an azide group and a silanol group or an alkoxysilyl group.

9. The optical laminate of claim 8 , wherein the molecular adhesive further comprises a triazine ring, and the azide group is bonded to the triazine ring.

10. The optical laminate according to claim 9, wherein the flat portion and the third main surface have at least one reactive group selected from the group consisting of a hydrocarbon group, a carbonyl group, and a hydroxyl group, and form a covalent bond with the molecular adhesive.

11. The optical laminate according to claim 1 , wherein the first optical sheet is formed from a cured product of a curable resin.

12. The optical laminate according to claim 1 , which has a haze value of 5.0% or less.

13. An optical device comprising a light guide plate having the optical laminate according to claim 1 .

14. A method for producing the optical laminate according to any one of claims 1 to 3, A step A of applying a molecular adhesive represented by the following general formula [I] to at least one of the flat portion of the first optical sheet and the third main surface of the second optical sheet; After the step A, a step B of irradiating the molecular adhesive with light; a step C of heating the flat portion while applying pressure to the flat portion and the third main surface in a state where the flat portion and the third main surface are opposed to each other; The manufacturing method includes the steps of: 【Chemistry 1】 [wherein E is any group; F is an OH group or an OH-yielding group; -Q is -N ３ or -NR １ (R ２ ) -NR １ (R ２ ) R １、 R ２ is H, a hydrocarbon group having 1 to 24 carbon atoms, or -RSi(R')n(OA)3-n (R is a chain hydrocarbon group having 1 to 12 carbon atoms. R' is a chain hydrocarbon group having 1 to 4 carbon atoms. A is H or a chain hydrocarbon group having 1 to 4 carbon atoms. n is an integer from 0 to 2.) R １ and R ２ may be the same or different.]

15. The method according to claim 14, wherein the heating in step C is performed at a temperature of 60°C or higher and 150°C or lower.

16. The method according to claim 14, wherein the heating in step C is performed at a temperature of 80°C or higher and 110°C or lower.

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