Method for manufacturing basel material less double-sided adhesive sheet

Abstract

The present invention provides a method for manufacturing a substrate-free double-sided adhesive sheet that can suppress the transfer of the adhesive layer to the light release film when the light release film is peeled off, and the substrate-free double-sided adhesive sheet. The present invention provides a method for manufacturing a substrate-free double-sided adhesive sheet, the substrate-free double-sided adhesive sheet comprising an adhesive layer, a heavy-release film deposited on one side of the aforementioned adhesive layer, and a light-release film deposited on the other side of the aforementioned adhesive layer. The manufacturing method comprises: a coating step of coating an adhesive composition onto the aforementioned light-release film to form a coating layer; a drying step of drying the aforementioned coating layer to obtain the aforementioned adhesive layer; and a lamination step of laminating the heavy-release film onto the aforementioned adhesive layer.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing a substrate-free double-sided adhesive sheet and a laminate using the substrate-free double-sided adhesive sheet. [Previous Technology]

[0002] A polarizing plate, formed by laminating a protective film onto one or both sides of a polarizing film, is an optical component used in image display devices such as liquid crystal display devices and organic electroluminescent (organic EL) display devices. Optical components such as polarizing plates are mostly bonded to other components (e.g., optical components such as liquid crystal cells in liquid crystal display devices) through an adhesive layer. This adhesive layer is sometimes obtained by bonding a substrate-free double-sided thin film.

[0003] Substrate-free double-sided adhesive sheets generally have the following structure: a release film with relatively low peel strength (light release film) on one side of the adhesive layer that does not have a substrate that serves as a core material, and a release film with relatively high peel strength (heavy release film) on the other side of the adhesive layer. Substrate-free double-sided adhesive sheets are manufactured by coating an adhesive composition onto a heavy release film and drying it to form an adhesive layer, and then laminating a light release film onto the adhesive layer.

[0003] When using a substrate-free double-sided adhesive sheet to bond optical components together, the following method is typically employed: a light release film is peeled off from the substrate-free double-sided adhesive sheet, the exposed adhesive layer is bonded to one side of the optical component, and then a heavy release film is peeled off, exposing the adhesive layer on the other side of the optical component to bond the optical components together. However, when the difference in peel force between the light and heavy release films deposited on both sides of the substrate-free double-sided adhesive sheet is small, when peeling off the light release film of the substrate-free double-sided adhesive sheet, a portion of the adhesive layer may follow the light release film and break after being stretched between the heavy and light release films, transferring to the light release film side, resulting in poor peeling (unintended separation). If optical components are bonded together using adhesive layers that have unexpectedly separated, light reflection will occur due to the poor adhesion between the optical components to begin with, and the unevenness of the adhesive layer caused by the unexpected separation. This will lead to a decrease in the optical properties of optical components such as polarizers.

[0004] As a method to suppress poor peeling (unintended separation), Patent Document 1 describes a method to increase the peeling force of a heavy-release film by using a heavy-release film formed on a plastic film by using a composition containing a polysiloxane release agent that is a heavy-release additive, thereby increasing the peeling force difference between the light-release film and the heavy-release film.

[0004] [Previous Technical Documents]

[0004] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 07-041736

[0006] In recent years, with the thinning of liquid crystal display devices and organic EL display devices, there has been a demand for thinner polarizing plates and adhesive layers. However, if the adhesive layer is thinned, the rigidity of the adhesive layer itself is reduced. When the light release film is peeled from the substrate-free double-sided adhesive sheet, it is easier for the adhesive layer to transfer to the light release film (unintended separation). The method described in Patent Document 1 sometimes fails to sufficiently suppress unintended separation.

[0007] The inventors conducted detailed research in order to solve the above-mentioned problems, and as a result, completed the present invention.

[0007] That is, the present invention includes the inventions described in [1] to [9] below.

[0007] [1] A method for manufacturing a substrate-free double-sided adhesive sheet, the substrate-free double-sided adhesive sheet comprising an adhesive layer, a heavy-release film deposited on one side of the aforementioned adhesive layer, and a light-release film deposited on the other side of the aforementioned adhesive layer, the manufacturing method comprising:

[0007] Coating step: The adhesive composition is coated on the aforementioned light release film to form a coating layer;

[0007] Drying step, to dry the aforementioned coating layer to obtain the aforementioned adhesive layer; and

[0007] Lamination step: Lamination of the peeling film onto the aforementioned adhesive layer.

[0007] [2] The method for manufacturing a substrate-free double-sided adhesive sheet as described in [1], wherein the aforementioned heavy-release film is a release treatment layer containing a heavy-release additive formed on a plastic film,

[0007] The aforementioned light-release film is a release treatment layer formed on a plastic film without heavy-release additives.

[0007] [3] An adhesive layer, wherein the water contact angle of one surface differs from the water contact angle of the other surface by more than 3 degrees.

[0007] [4] A substrate-free double-sided adhesive sheet, comprising an adhesive layer, a heavy-duty release film deposited on one side of the adhesive layer, and a light-duty release film deposited on the other side of the adhesive layer, wherein,

[0007] The water contact angle of the light peel film side surface of the aforementioned adhesive layer is smaller than the water contact angle of the heavy peel film side surface of the aforementioned adhesive layer.

[0007] [5] As described in [4], the substrate-free double-sided adhesive sheet, wherein the water contact angle of the light peel film side surface of the aforementioned adhesive layer differs from the water contact angle of the heavy peel film side surface of the aforementioned adhesive layer by more than 3 degrees.

[0007] [6] As described in [4] or [5], a substrate-free double-sided adhesive sheet, wherein the aforementioned heavy-release film is a release treatment layer containing a heavy-release additive formed on a plastic film.

[0007] The aforementioned light-release film is a release treatment layer formed on a plastic film without heavy-release additives.

[0007] [7] A laminate, comprising in sequence an optical component, an adhesive layer, and a release film, wherein,

[0007] The water contact angle of the optical component side surface of the aforementioned adhesive layer is smaller than the water contact angle of the peeling film side surface of the aforementioned adhesive layer.

[0007] [8] As described in [7], the water contact angle of the optical component side surface of the aforementioned adhesive layer differs from the water contact angle of the re-peeling film side surface of the aforementioned adhesive layer by more than 3 degrees.

[0007] [9] The laminate as described in [7] or [8], wherein the aforementioned release film is a release treatment layer containing a release additive formed on a plastic film.

[0007]

[10] A method for manufacturing a laminate, the laminate sequentially comprising an optical component, an adhesive layer and a release film, the manufacturing method comprising:

[0007] The steps of manufacturing a substrate-free double-sided adhesive sheet by means of the method for manufacturing a substrate-free double-sided adhesive sheet as described in [1] or [2]; and

[0007] In the bonding step, the light release film is peeled off from the aforementioned substrate-free double-sided adhesive sheet, and the adhesive layer is bonded to the optical component.

[0008] According to the present invention, a method for manufacturing a substrate-free double-sided adhesive sheet that can suppress the transfer of the adhesive layer to the light release film when the light release film is peeled off, and a substrate-free double-sided adhesive sheet can be provided.

Implementation Method

[0009] The present invention relates to a method for manufacturing a substrate-free double-sided adhesive sheet, the substrate-free double-sided adhesive sheet comprising an adhesive layer, a heavy-release film deposited on one side of the adhesive layer, and a light-release film deposited on the other side of the adhesive layer. The manufacturing method is characterized by comprising: a coating step of coating an adhesive composition onto the light-release film to form a coating layer; a drying step of drying the coating layer to obtain the adhesive layer; and a lamination step of laminating the heavy-release film onto the adhesive layer.

[0010] <Substrate-free double-sided adhesive sheet>

[0010] The substrate-free double-sided adhesive sheet of the present invention has the following configuration: a light release film is laid on one side of the adhesive layer, and a heavy release film is laid on the other side of the adhesive layer. Furthermore, the substrate-free double-sided adhesive sheet of the present invention is characterized in that the water contact angle of the light release film side surface of the adhesive layer is smaller than the water contact angle of the heavy release film side surface of the adhesive layer.

[0011] <Release Film>

[0011] The light and heavy peeling films in the substrate-free double-sided adhesive sheet of the present invention refer to the relatively light or heavy peeling force of each peeling film. Each peeling film is not particularly limited, but preferably is a peeling film composed of a plastic film and a release treatment layer.

[0011] In the substrate-free double-sided adhesive film, the light release film and the heavy release film are respectively deposited on the adhesive layer with their release treatment layers facing the adhesive layer. Preferably, the release treatment layers of the light release film and the heavy release film are respectively in contact with the surface of the adhesive layer.

[0012] Examples of plastic films include: polyethylene terephthalate films, polybutylene terephthalate films, and polyethylene naphthalate films, as well as polyester films or polypropylene films, and other polyolefin films. Among these, from the viewpoint of optical properties and quality, polyethylene terephthalate films are preferred, and from the viewpoint of excellent dimensional stability, biaxially oriented polyethylene terephthalate films are preferred.

[0013] The release treatment layer may be formed from a release treatment layer forming composition. The release treatment composition is a resin composition containing a resin, and may further include additives such as release additives to control peel force. From the viewpoint of easily controlling peel force, a heavy-duty release film with a release treatment layer containing a heavy-duty release additive is preferred as a heavy-duty release film. A light-duty release film without a heavy-duty release additive is preferred as a light-duty release film. The resin constituting the release treatment layer forming composition is not particularly limited, and examples include: polysiloxane resin, alkyd resin, acrylic resin, and long-chain alkyl resin. Polysiloxane resin is preferred.

[0014] Examples of polysiloxane resins include: polysiloxane resins having dimethyl polysiloxane as the basic backbone. The polysiloxane resin can be any of the following types: addition-reaction type, condensation-reaction type, UV-curable type, electron beam-curable type, etc., but addition-reaction type polysiloxane resins are preferred. Addition-reaction type polysiloxane resins have high reactivity and excellent manufacturability, and compared to condensation-reaction type resins, they have advantages such as smaller changes in peel force after manufacturing and no curing shrinkage, thus making them preferred.

[0015] Specific examples of addition-reactive polysiloxanes include organopolysiloxanes having two or more alkenyl groups (such as vinyl, allyl, propenyl, and hexenyl) with 2 to 10 carbon atoms at the end of the molecule and / or on the side chains. Commercially available products can be used for addition-reactive polysiloxanes, such as "LTC759" (manufactured by Dow Toray Co., Ltd.), "LTC750A" (manufactured by Dow Toray Co., Ltd.), "LTC755" (manufactured by Dow Toray Co., Ltd.), and "KS-847" (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0015] When using addition-reaction type polysiloxane resin, it is preferable to use a crosslinking agent and a catalyst together.

[0016] Crosslinking agent, for example, is an organic polysiloxane having at least two hydrogen atoms bonded to silicon atoms in one molecule, specifically including: dimethylsiloxy-terminated dimethylsiloxane-methylsiloxane copolymer, trimethylsiloxy-terminated dimethylsiloxane-methylsiloxane copolymer, trimethylsiloxy-terminated methylhydropolysiloxane, poly(hydrosilsesquioxane), etc.

[0017] Catalysts may include: microparticle platinum, microparticle platinum adsorbed on a carbon powder carrier, chloroplatinic acid, alcohol-modified chloroplatinic acid, olefin complexes of chloroplatinic acid, platinum-based metal compounds such as palladium and rhodium, etc. By using such catalysts, the curing reaction of the composition for forming the release layer can be carried out more efficiently. Commercially available products may also be used as catalysts, such as: "SRX212" (manufactured by Dow Toray Co., Ltd.), "SRX212P" (manufactured by Dow Toray Co., Ltd.), "CAT-PL-50T" (manufactured by Shin-Etsu Chemical Co., Ltd.), etc.

[0018] When manufacturing a release treatment film, the composition for forming the release treatment layer that constitutes the release treatment layer preferably contains a release treatment additive.

[0018] As a heavy-duty peeling additive, it is preferably a polyorganosiloxane having one or more reactive sites in its molecule, and more preferably a polysiloxane having one or more reactive sites in its molecule. Examples of reactive sites include: hydroxyl groups, carboxyl groups, alkoxy groups with 1 to 6 carbon atoms, halogen atoms, acetoxy groups, aliphatic groups, and other hydrolyzable groups; and alkenyl groups such as vinyl groups. Examples of polysiloxane resins include, for example, MQ resins containing M units belonging to monofunctional siloxane units [R3SiO1 / 2] and Q units belonging to tetrafunctional siloxane units [SiO4 / 2]. The three Rs in the M unit independently represent a hydrogen atom, a hydroxyl group, or an organic group, and one or more of these three Rs are preferably the aforementioned reactive sites. As a heavy-duty peeling additive, it is preferably a polyorganosiloxane having an alkenyl group as a reactive site, more preferably a vinyl-modified polyorganosiloxane, and particularly preferably a vinyl-modified polysiloxane.

[0019] The weight-average molecular weight (Mw) of the heavy-release additive, converted from standard polystyrene by gel permeation chromatography (GPC), is preferably 5 million to 500,000, more preferably 8 million to 100,000, and even more preferably 1,000 to 10,000. If the weight-average molecular weight of the heavy-release additive is less than 500, its retention of the resin (preferably polysiloxane) is poor, and it tends to transfer to the surface of the adhesive layer when bonded to it. Conversely, if the weight-average molecular weight exceeds 500,000, the viscosity of the heavy-release additive becomes too high, making it difficult to synthesize industrially.

[0020] When adding a heavy-duty release additive, the amount added relative to 100 parts by weight of the resin is preferably 80 parts by weight or less, more preferably 60 parts by weight or less, and even more preferably 50 parts by weight or less. Furthermore, it is preferably 0.01 parts by weight or more, and more preferably 0.1 parts by weight or more. If the heavy-duty release additive exceeds 80 parts by weight, the peeling force when peeling the heavy-duty release film from the adhesive layer becomes too high, making peeling difficult. When the heavy-duty release additive is less than 0.01 parts by weight, in the case of combining it with a release film (light-duty release film) without the heavy-duty release additive to produce a substrate-free double-sided adhesive sheet, the difference in peeling force between the heavy-duty release film and the light-duty release film becomes smaller, and there is a tendency for poor peeling (unintended separation) to easily occur, where the adhesive layer transfers to the light-duty release film side.

[0021] Furthermore, additives other than those mentioned above may also be appropriately incorporated into the composition for forming the release layer. Examples of additives include: catalysts, dyes, dispersants, etc. In addition, the composition for forming the release layer may also contain a dispersion medium or solvent in order to keep the viscosity within an appropriate range during coating.

[0021] The dispersion medium or solvent may include: aromatic hydrocarbons such as toluene and xylene, fatty acid esters such as ethyl acetate and methyl acetate, ketones such as methyl ethyl ketone (MEK), and organic solvents such as aliphatic hydrocarbons such as hexane and heptane.

[0022] The release film can be manufactured, for example, by coating one side of a plastic film with a solvent-diluted release layer composition using conventional methods, and then drying the resulting coating layer. Examples of coating methods include gravure coating, bar coating, spray coating, spin coating, air knife coating, roller coating, doctor blade coating, gate roll coater coating, and die coating. Among these, gravure coating and bar coating are preferred, with gravure coating being even more preferred.

[0022] Furthermore, the drying method for the coating layer of the composition used to form the release treatment layer can be, for example, by heat drying in a hot air drying oven. The drying temperature is, for example, 50°C to 200°C, preferably 70°C to 150°C. Furthermore, the drying time is preferably, for example, 5 seconds to 5 minutes.

[0023] The thickness of the release film can be controlled by the thickness of the plastic film and the thickness of the release treatment layer. The thickness is primarily determined by the thickness of the plastic film, which can be controlled by selecting a polyester film with the target thickness. The thickness of the plastic film is preferably 15 μm or more, more preferably 19 μm or more, and even more preferably 25 μm or more. There is no particular upper limit to the thickness of the plastic film; it is typically 200 μm or less. From the viewpoint of easy peeling of the release film, it is preferably 150 μm or less, and even more preferably 100 μm or less. The thickness of the release treatment layer is preferably 25 nm or more, more preferably 30 nm or more, and even more preferably 40 nm or more. Furthermore, it is preferably 500 nm or less, even more preferably 300 nm or less, and even more preferably 250 nm or less. By ensuring the thickness of the release treatment layer is 25 nm or more, shrinkage during the coating of the composition for forming the release treatment layer can be suppressed, as can uneven peel force and localized unintended separation. By keeping the thickness of the release layer below 250nm, the agglomeration of the release films can be suppressed.

[0024] <Adhesive layer>

[0024] The adhesive composition forming the adhesive layer is not particularly limited, but is preferably an acrylic adhesive composition. The acrylic adhesive composition includes (meth)acrylic resin and a crosslinking agent. The acrylic adhesive composition may also further include silane compounds and antistatic agents.

[0024] In addition, in this specification, (meth)acrylic resin refers to either acrylic resin or methacrylic resin, and "(meth)" in (meth)acrylate, etc., is also synonymous.

[0025] (Meth)acrylate resins refer to polymers whose main components are structural units derived from (meth)acrylates. (Meth)acrylate resins may also contain one or more structural units derived from monomers other than (meth)acrylates (e.g., structural units derived from monomers having polar functional groups).

[0025] (Meth)acrylates can be listed as: (meth)acrylates shown in formula (I) below.

[0025] [In formula (I), R1 represents a hydrogen atom or a methyl group, and R2 represents an alkyl or aralkyl group having 1 to 14 carbon atoms, preferably an alkyl group, wherein the hydrogen atom of the alkyl or aralkyl group may be replaced by an alkoxy group having 1 to 10 carbon atoms].

[0025] In formula (I), R2 is preferably an alkyl group having 1 to 14 carbon atoms.

[0026] Examples of (meth)acrylates include:

[0026] Linear alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, n-octyl acrylate, and dodecyl acrylate; branched alkyl acrylates such as isobutyl acrylate, 2-ethylhexyl acrylate, and isooctyl acrylate.

[0026] Methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, n-octyl methacrylate, dodecyl methacrylate and other straight-chain alkyl methacrylates;

[0026] Isobutyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate and other branched alkyl methacrylates;

[0026] Alkoxyalkyl esters of (meth)acrylic acid, such as 2-methoxyethyl acrylate, ethoxymethyl acrylate, 2-methoxyethyl methacrylate, and ethoxymethyl methacrylate; and

[0026] Benzyl acrylate, benzyl methacrylate, and other (meth)acrylate aramid esters.

[0027] The (meth)acrylic resin may also contain two or more structural units derived from (meth)acrylates, preferably including structural units derived from (meth)acrylates with a glass transition temperature (Tg) below 0°C and structural units derived from (meth)acrylates with a Tg above 0°C.

[0027] (Meth)acrylates with a Tg below 0°C are preferably n-butyl acrylate. (Meth)acrylates with a Tg above 0°C are preferably methyl acrylate.

[0028] (Meth)acrylic resins may also contain structural units derived from monomers other than those described above. Structural units derived from monomers other than those described above are preferably structural units derived from monomers having polar functional groups, and more preferably structural units derived from (meth)acrylates having polar functional groups. Examples of polar functional groups include: hydroxyl groups, substituted or unsubstituted amino groups, epoxy groups, and other heterocyclic groups.

[0028] Monomers with polar functional groups can be listed as follows:

[0028] 2-Hydroxyethyl methacrylate, 3-Hydroxypropyl methacrylate, 4-Hydroxybutyl methacrylate, 2-(2-hydroxyethoxy)ethyl methacrylate, 2-chloro-2-hydroxypropyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, diethylene glycol mono(meth)acrylate, and other monomers containing hydroxyl groups;

[0028] Monomers containing heterocyclic groups, such as acrylonitrile, vinylcaprolactone, N-vinyl-2-pyrrolidone, vinylpyridine, tetrahydrofurfuryl (meth)acrylate, caprolactone-modified tetrahydrofurfuryl acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, glycidyl (meth)acrylate, and 2,5-dihydrofuran;

[0028] Monomers such as (meth)acrylate aminoethyl ester, (meth)acrylate N,N-dimethylaminoethyl ester, and (meth)acrylate dimethylaminopropyl ester, which have substituted or unsubstituted amino groups. Among them, monomers having hydroxyl groups are preferred, and from the viewpoint of the reactivity of (meth)acrylate resins with crosslinking agents, (meth)acrylates having hydroxyl groups are even more preferred.

[0029] Relative to 100 parts by mass of all structural units of the (meth)acrylic resin, the content of structural units derived from monomers having polar functional groups in the (meth)acrylic resin is preferably 10 parts by mass or less, more preferably 0.5 parts by mass or more than 10 parts by mass, even more preferably 0.5 parts by mass or more than 5 parts by mass, and most preferably 1 part by mass or more than 5 parts by mass.

[0030] As a monomer with a polar functional group, monomers with a carboxyl group as a polar functional group can also be listed (e.g., acrylic acid, methacrylic acid, etc.). The content of structural units derived from monomers with carboxyl groups in (meth)acrylic resins is less than 2 parts by mass relative to 100 parts by mass of all structural units of (meth)acrylic resins, thereby suppressing the corrosion of transparent electrodes under humid and hot conditions.

[0031] (Meth)acrylic resins may also contain structural units derived from monomers having aromatic groups. Monomers having aromatic groups include monomers having one olefinic double bond and one or more aromatic rings (e.g., benzene ring, naphthalene ring, etc.) in the molecule and not having polar functional groups, preferably (meth)acrylates having phenoxyethyl groups.

[0031] Examples of (meth)acrylates containing phenoxyethyl groups include: 2-phenoxyethyl (meth)acrylate, 2-(2-phenoxyethoxy)ethyl (meth)acrylate, ethylene oxide-modified nonylphenol ester of (meth)acrylate, and 2-(o-phenylphenoxy)ethyl (meth)acrylate. Preferred are 2-phenoxyethyl (meth)acrylate and 2-(2-phenoxyethoxy)ethyl (meth)acrylate.

[0032] Relative to 100 parts by mass of all structural units of the (meth)acrylic resin, the content of structural units derived from monomers having aromatic groups in the (meth)acrylic resin is preferably 20 parts by mass or less, more preferably 4 parts by mass or more but less than 20 parts by mass, and even more preferably 4 parts by mass or more but less than 16 parts by mass.

[0033] In addition to the above, (meth)acrylic resins may also include structural units derived from (meth)acrylates having an alicyclic structure, structural units derived from styrene monomers, structural units derived from vinyl monomers, structural units derived from monomers having multiple (meth)acrylic groups within the molecule, structural units derived from (meth)acrylamide monomers, etc.

[0034] Alicyclic structures can be listed as cycloalkanes with 5 or more carbon atoms, preferably 5 to 7. Examples of (meth)acrylates with alicyclic structures include: isocamphene acrylate, cyclohexyl acrylate, dicyclopentyl acrylate, cyclododecyl acrylate, methylcyclohexyl acrylate, trimethylcyclohexyl acrylate, tributylcyclohexyl acrylate, α-ethoxycyclohexyl acrylate, cyclohexylphenyl acrylate, isocamphene methacrylate, cyclohexyl methacrylate, dicyclopentyl methacrylate, cyclododecyl methacrylate, methylcyclohexyl methacrylate, trimethylcyclohexyl methacrylate, tributylcyclohexyl methacrylate, cyclohexylphenyl methacrylate, etc.

[0035] Styrene monomers can be listed as: styrene; alkyl styrene such as methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, diethylstyrene, triethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene, octylstyrene; halogenated styrene such as fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, iodostyrene; nitrostyrene; acetyrene; methoxystyrene; and divinylbenzene.

[0036] Examples of vinyl monomers include: vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, vinyl laurate and other fatty acid vinyl esters; vinyl chloride, vinyl bromide and other halogenated vinylides; vinyl chloride and other halogenated vinylides; nitrogen-containing heteroaromatic vinyls such as vinylpyridine, vinylpyrrolidone, vinylcarbazole and other vinylides; conjugated dienes such as butadiene, isoprene, chloroprene and other conjugated dienes; and unsaturated nitriles such as acrylonitrile, methacrylonitrile and other unsaturated nitriles.

[0037] Monomers having multiple (meth)acrylic groups in their molecules can be listed as follows: 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, etc., which have 2 (meth)acrylic groups in their molecules; and trimethylolpropane tri(meth)acrylate, etc., which have 3 (meth)acrylic groups in their molecules.

[0038] Monomers of (meth)acrylamide can be listed as follows: N-hydroxymethyl (meth)acrylamide, N-(2-hydroxyethyl) (meth)acrylamide, N-(3-hydroxypropyl) (meth)acrylamide, N-(4-hydroxybutyl) (meth)acrylamide, N-(5-hydroxypentyl) (meth)acrylamide, N-(6-hydroxyhexyl) (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide Acrylamide, N-isopropyl(meth)acrylamide, N-(3-dimethylaminopropyl)(meth)acrylamide, N-(1,1-dimethyl-3-epoxybutyl)(meth)acrylamide, N-[2-(2-epoxy-1-imidazolidine)ethyl](meth)acrylamide, 2-acrylamide-2-methyl-1-propanesulfonic acid, N-(methoxymethyl)acrylamide, N-(ethoxymethyl)(meth)acrylamide, N-(propoxy)acrylamide N-(1-methylethoxymethyl)acrylamide, N-(1-methylpropoxymethyl)acrylamide, N-(2-methylpropoxymethyl)acrylamide, N-(butoxymethyl)acrylamide, N-(1,1-dimethylethoxymethyl)acrylamide, N-(2-methoxyethyl)acrylamide, N-(2-ethoxyethyl)acrylamide The formulation includes N-(2-propoxyethyl)acrylamide, N-[2-(1-methylethoxy)ethyl](methyl)acrylamide, N-[2-(1-methylpropoxy)ethyl](methyl)acrylamide, N-[2-(2-methylpropoxy)ethyl](methyl)acrylamide, N-(2-butoxyethyl)(methyl)acrylamide, and N-[2-(1,1-dimethylethoxy)ethyl](methyl)acrylamide. Preferred formulations include N-(methoxymethyl)acrylamide, N-(ethoxymethyl)acrylamide, N-(propoxymethyl)acrylamide, N-(butoxymethyl)acrylamide, and N-(2-methylpropoxymethyl)acrylamide.

[0039] In the (meth)acrylic resin, in addition to the structural unit derived from (meth)acrylate without polar functional groups, it is preferable to further include at least one structural unit selected from the group consisting of structural units derived from monomers having hydroxyl groups (preferably (meth)acrylate with hydroxyl groups) and structural units derived from monomers having aromatic groups (preferably monomers having one olefinic double bond and one or more aromatic rings (e.g., benzene ring, naphthalene ring, etc.) and without polar functional groups).

[0040] The weight-average molecular weight (Mw) of the (meth)acrylic resin is preferably between 500,000 and 2,500,000. If the weight-average molecular weight is above 500,000, the adhesion of the adhesive layer in a high-humidity and high-temperature environment is improved, the possibility of bumping or peeling between the release film or optical component and the adhesive layer is reduced, and reworkability is also improved. If the weight-average molecular weight is below 2,500,000, even if the size of the optical component changes, the adhesive layer is more likely to follow the size change, thus suppressing white spots and color unevenness in the liquid crystal display device containing the laminate of the present invention. The molecular weight distribution (Mw / Mn), expressed as the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn), is typically between 2 and 10. The weight-average molecular weight can be analyzed by gel permeation chromatography, and it is a value converted from standard polystyrene.

[0041] The adhesive composition may also contain two or more (meth)acrylic resins, for example, it may also contain a (meth)acrylic resin with a weight average molecular weight of 500,000 to 2,500,000 as the main component of the (meth)acrylic ester structural unit as shown in Formula (I) and a (meth)acrylic resin with a weight average molecular weight of 50,000 to 300,000 as the main component of the (meth)acrylic ester structural unit as shown in Formula (I).

[0042] When a (meth)acrylic resin is dissolved in ethyl acetate to prepare a polymer solution with a concentration of 20% by mass, it is preferably a (meth)acrylic resin with a viscosity of 20 Pa·s or less at 25°C, more preferably a (meth)acrylic resin with a viscosity of 0.1 to 7 Pa·s. In this case, the adhesive layer formed from the adhesive composition containing a (meth)acrylic resin with a viscosity of 20 Pa·s or less exhibits improved adhesion under high humidity and heat conditions, a lower tendency for bulging or peeling to occur between the release film or optical component and the adhesive layer, and a tendency for improved reworkability. Furthermore, the viscosity can be measured using a Brookfield viscometer.

[0043] From the viewpoint of exhibiting adhesive properties, the glass transition temperature of (meth)acrylic resins is preferably -10°C to -60°C. The glass transition temperature can be measured using a differential scanning calorimeter (DSC).

[0044] (Meth)acrylic resins can generally be manufactured by conventional polymerization methods such as solution polymerization, bulk polymerization, suspension polymerization, and emulsion polymerization. The manufacture of (meth)acrylic resins typically involves polymerization in the presence of a polymerization initiator. The amount of polymerization initiator used is typically 0.001 to 5 parts by mass relative to 100 parts by mass of all monomers constituting the (meth)acrylic resin. (Meth)acrylic resins can also be manufactured by polymerization using active energy lines such as ultraviolet light.

[0045] Polymerization initiators can be listed as: thermal polymerization initiators and photopolymerization initiators. Photopolymerization initiators can be listed as: 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl) ketone. Thermal polymerization initiators can be listed as: azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carboxynitrile), 2,2'-azobis(2,4-dimethylpentanonitrile), 2,2'-azobis(2,4-dimethyl-4-methoxypentanonitrile), dimethyl-2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-hydroxymethylpropionitrile); lauryl peroxide (lauryl... Organic peroxides include peroxide, tert-butyl hydroperoxide, benzoyl peroxide, tert-butyl peroxybenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, dipropyl peroxydicarbonate, tert-butyl peroxyneodecanate, tert-butyl peroxytrimethylacetic acid, and (3,5,5-trimethylhexylidene) peroxide; inorganic peroxides include potassium persulfate, ammonium persulfate, and hydrogen peroxide. Alternatively, redox initiators combining peroxides and reducing agents can be used as polymerization initiators.

[0046] The (meth)acrylic resin is preferably manufactured by solution polymerization. Specifically, the desired monomer is mixed with an organic solvent, and a thermal polymerization initiator is added to the resulting solution under a nitrogen atmosphere. The resulting mixture is stirred at approximately 40°C to 90°C, preferably 60°C to 80°C, for approximately 3 to 10 hours to obtain the (meth)acrylic resin. To control the polymerization reaction, the monomer, thermal polymerization initiator, or both may be added to the reaction system continuously or intermittently during the polymerization reaction, or added in a state dissolved in an organic solvent. Examples of organic solvents include: aromatic hydrocarbon solvents such as toluene and xylene; ester solvents such as ethyl acetate and butyl acetate; aliphatic alcohol solvents such as propanol and isopropanol; and ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone.

[0047] <Crosslinking agent>

[0047] The adhesive composition contains a crosslinking agent. Examples of crosslinking agents include: isocyanate compounds, epoxides, aziridine compounds, metal chelate compounds, etc.

[0048] Isocyanate compounds are compounds having at least two isocyanate groups (-NCO) within their molecules. Examples include: toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, phenyl dimethyl diisocyanate, hydrogenated phenyl dimethyl diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, etc. Also included are: adducts obtained by reacting these isocyanate compounds with polyols such as glycerol or trimethylolpropane, dimers and trimers of these isocyanate compounds. Combinations of two or more isocyanate compounds are also possible.

[0049] Epoxides are compounds with at least two epoxy groups within their molecules. Examples include: bisphenol A type epoxy resins, ethylene glycol diepoxide, polyethylene glycol diepoxide, glycerol diepoxide, glycerol triepoxide, 1,6-hexanediol diepoxide, trimethylolpropane triepoxide, N,N-diepoxide-propylaniline, N,N,N',N'-tetraepoxide-propylm-xylenediamine, 1,3-bis(N,N'-diepoxide-propylaminomethyl)cyclohexane, etc. Combinations of two or more epoxides are also possible.

[0050] Aziridine compounds are compounds with at least two ethyleneimine skeletons in their molecules, that is, a three-membered ring skeleton composed of one nitrogen atom and two carbon atoms. Specific examples include: diphenylmethane-4,4'-bis(1-aziridinemethylamine), toluene-2,4-bis(1-aziridinemethylamine), triethyl melamine, isophthalamide bis-1-(2-methylaziridine), tris(-1-aziridine)phosphine oxide, hexamethylene-1,6-bis(1-aziridinemethylamine), trimethylolpropane-tris(-β-aziridine)propionate, tetramethylolpropane-tris(-β-aziridine)propionate, etc.

[0051] Examples of metal chelate compounds include compounds in which acetoacetone or ethyl acetate is coordinated to polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium.

[0052] Preferably, it is an adduct obtained by reacting an isocyanate compound, toluene diisocyanate, toluene diisocyanate with a polyol, a dimer of toluene diisocyanate, a trimer of toluene diisocyanate, phenyl diisocyanate, phenyl diisocyanate with a polyol, a dimer of phenyl diisocyanate, a trimer of phenyl diisocyanate, hexamethylene diisocyanate, hexamethylene diisocyanate with a polyol, a dimer of hexamethylene diisocyanate, a trimer of hexamethylene diisocyanate, and mixtures thereof.

[0053] The content of crosslinking agent in the adhesive composition is typically 0.05 to 5 parts by weight relative to 100 parts by weight of (meth)acrylic resin (or the sum of two or more (meth)acrylic resins). If the amount of crosslinking agent is 0.05 parts by weight or more, there is a tendency to improve the durability of the adhesive layer; if it is less than 5 parts by weight, white spots become less noticeable when the laminate of the present invention described later is applied to a liquid crystal display device.

[0054] <Silane Compounds>

[0054] The adhesive composition may also contain silane compounds.

[0054] Examples of silane compounds include: vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(2-methoxyethoxy)silane, 3-epoxypropoxypropyltrimethoxysilane, 3-epoxypropoxypropyltriethoxysilane, 3-epoxypropoxypropylmethyldimethoxysilane, 3-epoxypropoxypropylethoxydimethylsilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, etc.

[0055] Silicate compounds can also be polysiloxane oligomers. Specific examples of polysiloxane oligomers are shown below. In addition, in the following specific examples, polysiloxane oligomers are referred to as combinations of monomers.

[0055] 3-Mercaptopropyltrimethoxysilane-tetramethoxysilane oligomers, 3-mercaptopropyltrimethoxysilane-tetraethoxysilane oligomers, 3-mercaptopropyltriethoxysilane-tetramethoxysilane oligomers, 3-mercaptopropyltriethoxysilane-tetraethoxysilane oligomers, and other oligomers containing mercaptopropyl groups;

[0056] Mercaptomethyltrimethoxysilane-tetramethoxysilane oligomers, mercaptomethyltrimethoxysilane-tetraethoxysilane oligomers, mercaptomethyltriethoxysilane-tetramethoxysilane oligomers, mercaptomethyltriethoxysilane-tetraethoxysilane oligomers, and other oligomers containing mercaptomethyl groups;

[0057] 3-Methylpropenyloxypropyltrimethoxysilane-tetramethoxysilane oligomer, 3-methylpropenyloxypropyltrimethoxysilane-tetraethoxysilane oligomer, 3-methylpropenyloxypropyltriethoxysilane-tetramethoxysilane oligomer, 3-methylpropenyloxypropyltriethoxysilane-tetraeth ...methoxysilane-tetramethoxysilane oligomer, 3-methylpropenyloxypropyltriethoxysilane-tetramethoxysilane-tetramethoxysilane oligomer, 3-methylpropenyloxypropyltriethoxysilane-tetramethoxysilane-tetramethoxysilane-tetramethoxysilane oligomer, 3-methylpropenyloxypropyltriethoxysilane-tetramethoxysilane-tetramethoxysilane-tetramethoxysilane-tetramethoxysilane-tetramethoxysilane-tetramethoxysilane-tetramethoxysilane-tetramethoxysilane-tetramethoxysilane-tetramethoxysilane-tetramethoxysilane-tetramethoxysilane-tetramethoxysilane-tetramethoxysilane-tetramethoxysilane-tetramethoxysilane-tetramethoxysilane-tetramethoxysilane-tetramethoxysilane-tetramethoxysilane-tetramethoxysilane-tetra Oligomers containing methacryloxypropyl, 3-methacryloxypropylmethyldimethoxysilane-tetramethoxysilane oligomers, 3-methacryloxypropylmethyldiethoxysilane-tetraethoxysilane oligomers, and 3-methacryloxypropylmethyldiethoxysilane-tetraethoxysilane oligomers;

[0058] 3-Acryloxypropyltrimethoxysilane-tetramethoxysilane oligomer, 3-Acryloxypropyltrimethoxysilane-tetraethoxysilane oligomer, 3-Acryloxypropyltriethoxysilane-tetramethoxysilane oligomer, 3-Acryloxypropyltriethoxysilane-tetraethoxysilane oligomer, 3-Acryloxypropyltriethoxysilane-tetraethoxysilane oligomer, 3-Acryloxy Oligomers containing acryloxypropyl groups, such as propylmethyldimethoxysilane-tetramethoxysilane oligomers, 3-propenyloxypropylmethyldimethoxysilane-tetraethoxysilane oligomers, 3-propenyloxypropylmethyldiethoxysilane-tetramethoxysilane oligomers, and 3-propenyloxypropylmethyldiethoxysilane-tetraethoxysilane oligomers;

[0059] Vinyltrimethoxysilane-tetramethoxysilane oligomers, vinyltrimethoxysilane-tetraethoxysilane oligomers, vinyltriethoxysilane-tetramethoxysilane oligomers, vinyltriethoxysilane-tetraethoxysilane oligomers, vinylmethyldimethoxysilane-tetramethoxysilane oligomers, vinylmethyldimethoxysilane-tetraethoxysilane oligomers, vinylmethyldiethoxysilane-tetramethoxysilane oligomers, vinylmethyldiethoxysilane-tetraethoxysilane oligomers, and other vinyl-containing oligomers.

[0060] The content of silane compounds in the adhesive composition is typically 0.01 to 10 parts by weight, and preferably 0.05 to 5 parts by weight, relative to 100 parts by weight of (meth)acrylate resin (or the sum of two or more (meth)acrylate resins). If the content of silane compounds is 0.01 parts by weight or more relative to 100 parts by weight of (meth)acrylate resin, there is a tendency to improve the adhesion between the adhesive layer and the optical component; if the content is less than 10 parts by weight, there is a tendency to inhibit the seepage of silane compounds from the adhesive layer.

[0061] <Antistatic Agent>

[0061] The adhesive composition may further include an antistatic agent. Antistatic agents can be those already known, and are preferably ionic. Catonic components constituting ionic antistatic agents can include organic and inorganic cations. Organic cations can include pyridinium cations, imidazoline cations, ammonium cations, strontium cations, phosphonium cations, etc. Inorganic cations can include alkali metal cations such as lithium cations, potassium cations, sodium cations, and cesium cations, as well as alkaline earth metal cations such as magnesium cations and calcium cations, etc. Anionic components constituting ionic antistatic agents can be either inorganic or organic anions; from the viewpoint of excellent antistatic properties, anionic components containing fluorine atoms are preferred. Anionic components containing fluorine atoms can be listed as follows: hexafluorophosphate anion (PF6-), bis(trifluoromethanesulfonyl)imidin anion [(CF3SO2)2N-], bis(fluorosulfonyl)imidin anion [(FSO2)2N-] anion, etc.

[0061] From the viewpoint that the adhesive composition has excellent antistatic properties and long-term stability, it is preferable to be an ionic antistatic agent that is solid at room temperature.

[0062] <Method for manufacturing substrate-free double-sided adhesive sheet>

[0062] The method for manufacturing a substrate-free double-sided adhesive sheet of the present invention is characterized by comprising the following steps (A) to (C).

[0062] Step (A): Coating step of applying the adhesive composition onto the light release film to form a coating layer.

[0062] Step (B): Drying the coating layer to obtain the adhesive layer.

[0062] Step (C): Lamination step of laminating the adhesive onto the re-peeling film.

[0063] <Coating Steps>

[0063] The coating step is a step of coating the adhesive composition onto a light release film to obtain a coating layer. The coating method of the adhesive composition is not particularly limited, and for example, slot-die method, reverse gravure coating, micro-gravure method, dip coating, spin coating, brush coating, roller coating, flexographic printing, etc. can be used.

[0063] The coating of the adhesive composition is performed on the release treatment layer of the light release film. Furthermore, before coating the adhesive composition, surface treatments such as corona treatment, plasma treatment, ultraviolet irradiation treatment, flame treatment, saponification treatment, and primer layer formation treatment may be performed on at least one side selected from the release treatment layer of the light release film and the adhesive layer.

[0063] The viscosity of the adhesive composition is generally below 20,000 cPs, preferably below 15,000 cPs, and more preferably above 1 cPs. Furthermore, the concentration of the solid component in the adhesive composition is generally 1 to 20% by mass, preferably 2 to 15% by mass.

[0064] The thickness of the adhesive layer in this invention may not reach 20 μm. The thickness of the adhesive layer is preferably 2 to 18 μm, more preferably 3 to 15 μm, and particularly preferably 3 to 10 μm. If the adhesive layer is thin, there is a tendency for unintended separation of the adhesive layer to occur easily when the light release film is peeled off; however, according to this invention, even in the case of a thin adhesive layer, unintended separation can be suppressed.

[0065] <Drying Steps>

[0065] The drying step is a step of drying the coating layer of the adhesive composition obtained in the above coating step.

[0065] The method for drying the coating layer is not particularly limited, and methods such as hot drying in a hot air drying oven can be cited. Furthermore, reduced pressure can also be applied during drying. The drying temperature is usually 30 to 200°C, preferably 50 to 160°C, and the drying time can be 5 seconds to 10 minutes.

[0066] <Lamination Steps>

[0066] The lamination step is a step of laminating the release film onto the adhesive layer obtained in the drying step described above. The lamination of the release film and the adhesive layer is performed by adhering the release treatment layer of the release film to the adhesive layer. Furthermore, before laminating the release film and the adhesive layer, at least one side selected from the release treatment layer of the release film and the adhesive layer may be subjected to surface treatments such as corona treatment, plasma treatment, ultraviolet irradiation treatment, flame treatment, saponification treatment, or primer coating formation treatment.

[0067] The substrate-free double-sided adhesive sheet obtained in step (C) can also be cured. For example, it can be stored in an environment with a temperature of 5 to 40 degrees Celsius and a relative humidity of 10 to 85% for 12 hours to 14 days, thereby stabilizing the performance of the adhesive.

[0068] By performing the above manufacturing method, the water contact angle of the adhesive layer surface on the light release film side can be made smaller than the water contact angle of the adhesive layer surface on the heavy release film side. In the conventional case where an adhesive composition is coated on the heavy release film, there is almost no difference between the water contact angle of the adhesive layer surface on the heavy release film side and the water contact angle of the adhesive layer surface on the light release film side. This is presumably because the heavy release additive contained in the release treatment layer of the heavy release film transfers and diffuses to the adhesive layer and reaches the surface on the light release film side, thus affecting the water contact angle of the adhesive layer surface on the light release film side. Furthermore, it is presumed that if the heavy release additive reaches the adhesive layer surface on the light release film side, the light release film in contact with the adhesive layer surface will also be affected by the heavy release additive, reducing the difference in peel force between the light and heavy release films, making unintended separation more likely.

[0069] On the other hand, it is speculated that in the manufacturing method of the present invention, since the adhesive composition is coated on the light release film, the transfer of the heavy release additive to the adhesive layer is suppressed, and the change in the water contact angle on the surface of the adhesive layer on the light release film side can be suppressed, thereby maintaining the difference between the peel force of the light release film and the peel force of the heavy release film. Therefore, in the case of using the substrate-free double-sided adhesive sheet of the present invention, even if the difference in peel force between the light release film and the heavy release film deposited on both sides does not reach 98 mN / 25 mm, the occurrence of unintended separation can be suppressed. In the present invention, the difference in peel force between the light release film and the heavy release film is preferably from 1 mN / 25 mm to 80 mN / 25 mm. In addition, the peel force can be measured using a precision universal testing machine.

[0070] In the substrate-free double-sided adhesive sheet of the present invention, the water contact angle of the light release film side surface of the adhesive layer and the water contact angle of the heavy release film side surface of the adhesive layer preferably differ by 3 degrees or more. Furthermore, in the substrate-free double-sided adhesive sheet of the present invention, the difference between the water contact angle of the light release film side surface of the adhesive layer and the water contact angle of the heavy release film side surface of the adhesive layer can be 50 degrees or less, or it can be 30 degrees or less. If the difference between the water contact angle of the light release film side surface of the adhesive layer and the water contact angle of the heavy release film side surface of the adhesive layer is less than 3 degrees, it can be inferred that the transfer of the heavy release additive to the adhesive layer cannot be sufficiently suppressed, resulting in a smaller difference between the peel force of the light release film and the peel force of the heavy release film. Additionally, the water contact angle of the adhesive layer surface can be measured using the method described in the embodiments. Furthermore, in the adhesive layer of the present invention, the difference between the water contact angle of one surface and the water contact angle of the other surface preferably differs by 3 degrees or more. In the adhesive layer of the present invention, the difference between the water contact angle of one surface and the water contact angle of the other surface can be less than 50 degrees or less than 30 degrees.

[0071] <Laminated Body>

[0071] The substrate-free double-sided adhesive sheet of the present invention can suppress unintended separation when the light release film is peeled off, and therefore can be used for bonding optical components to each other.

[0071] The present invention also includes a laminate of an adhesive layer and an optical component obtained from the substrate-free double-sided adhesive sheet of the present invention. The laminate of the present invention can be manufactured by peeling a light release film from the substrate-free double-sided adhesive sheet of the present invention and bonding the exposed adhesive layer to the optical component. Therefore, the laminate of the present invention sequentially includes an optical component, an adhesive layer, and a heavy release film, characterized in that the water contact angle of the optical component side surface of the adhesive layer is smaller than the water contact angle of the heavy release film side surface of the adhesive layer. In the laminate of the present invention, the water contact angle of the optical component side surface of the adhesive layer and the water contact angle of the heavy release film side surface of the adhesive layer preferably differ by 3 degrees or more, but can be 50 degrees or less, or can be 30 degrees or less. The heavy release film in the laminate of the present invention is preferably a film on a plastic film in which the release treatment layer containing the heavy release additive is formed.

[0072] The present invention also includes a method for manufacturing a laminate, the laminate comprising an optical component, an adhesive layer, and a release film, the method comprising:

[0072] The step of manufacturing a substrate-free double-sided adhesive sheet using the above-described method for manufacturing a substrate-free double-sided adhesive sheet; and

[0072] In the bonding step, the light release film is peeled off from the obtained substrate-free double-sided adhesive sheet and the exposed adhesive layer is bonded to the optical component.

[0073] The optical component is not particularly limited to any optical film (film with optical properties) that can be assembled into an image display device such as a liquid crystal display device. The optical film can be a single-layer structure or a multi-layer structure. Examples of optical films include: polarizers, polarizing plates, phase retardation films, brightness enhancement films, anti-glare films, anti-reflection films, diffusion films, and light-concentrating films, with polarizers, polarizing plates, or phase retardation films being more preferred.

[0073] The thickness of the optical component may also be less than 150 μm. The thickness of the optical component is preferably 5 to 120 μm or less, and more preferably 10 to 100 μm.

[0074] <Polarizing Film>

[0074] A polarizer is a layer or film that allows selective transmission of linearly polarized light from a certain direction originating from natural light. Examples of polarizers include films formed by adsorbing and aligning a dichroic dye onto a polyvinyl alcohol-based resin film. Examples of dichroic dyes include iodine and dichroic organic dyes. Furthermore, a polarizer can also be a coating-type polarizing film in which a dichroic dye in a lyotropic liquid crystal state is coated onto a substrate film and then aligned and fixed. Because such polarizers allow selective transmission of linearly polarized light from a certain direction originating from natural light while absorbing linearly polarized light from another direction, they are called absorption-type polarizers.

[0075] The polarizer is not limited to an absorptive polarizer. It can also be a reflective polarizer that selectively transmits linearly polarized light from one direction and reflects linearly polarized light from another direction, or a scattering polarizer that scatters linearly polarized light from another direction. However, from the viewpoint of superior aesthetics, an absorptive polarizer is preferred. Among these, a polyvinyl alcohol-based polarizer composed of a polyvinyl alcohol-based resin film is more preferably a polyvinyl alcohol-based polarizer formed by adsorbing and aligning iodine and dichroic dyes onto the polyvinyl alcohol-based resin film. It is especially preferred to be a polyvinyl alcohol-based polarizer formed by adsorbing and aligning iodine onto the polyvinyl alcohol-based resin film.

[0076] As a polyvinyl alcohol-based resin, a resin obtained by saponifying a polyvinyl acetate-based resin can be used. Besides polyvinyl acetate, which is a standalone polymer of vinyl acetate, examples of polyvinyl acetate-based resins include copolymers with other monomers that can be copolymerized with vinyl acetate. Examples of other monomers that can be copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides containing ammonium groups.

[0077] The saponification degree of polyvinyl alcohol (PVA) resins is typically 85 mol% to 100 mol%, preferably 98 mol% or higher. PVA resins can also be modified, for example, aldehyde-modified polyvinylformaldehyde or polyvinyl acetal can be used. The average degree of polymerization of PVA resins is typically 1000 to 10000, preferably 1500 to 5000. The average degree of polymerization of PVA resins can be determined according to JIS K 6726:1994.

[0078] The polyvinyl alcohol-based resin film produced in this manner is used as a raw material film for a polarizing film composed of a polyvinyl alcohol-based resin film. The method for producing the polyvinyl alcohol-based resin film is not particularly limited, and conventional methods may be used. The thickness of the polyvinyl alcohol-based raw material film is, for example, 150 μm or less, preferably 100 μm or less (e.g., 50 μm or less), and more preferably 5 μm or more.

[0079] The polarizing film made of a polyvinyl alcohol-based resin film can be manufactured by a conventional method. Specifically, it can be manufactured by a method comprising the following steps: a step of uniaxially stretching the polyvinyl alcohol-based resin film; a step of dyeing the polyvinyl alcohol-based resin film with a two-color pigment to adsorb the two-color pigment; a step of treating the polyvinyl alcohol-based resin film with the adsorbed two-color pigment with a boric acid aqueous solution (crosslinking treatment); and a step of washing with water after treatment with a boric acid aqueous solution.

[0080] The thickness of the polarizer can be 40 μm or less, preferably 30 μm or less (e.g., 20 μm or less, further 15 μm or less, even further 10 μm or less, or 8 μm or less). According to the methods described in Japanese Patent Application Publication Nos. 2000-338329 and 2012-159778, thin-film polarizers can be manufactured more easily, and the thickness of the polarizer can be made more easily to be, for example, 20 μm or less, further 15 μm or less, even further 10 μm or less, or 8 μm or less. The thickness of the polarizer is usually 2 μm or more. Reducing the thickness of the polarizer is beneficial for the thinning of the laminate containing the polarizer or polarizing plate and the image display device containing the laminate.

[0081] <Polarizing plate>

[0081] A polarizing plate is a protective film laminated on one or both sides of a polarizing film. Examples of protective films laminated on one or both sides of a polarizing film include: transparent resin films. Examples of transparent resins include: cellulose resins, acrylic resins, polyester resins, polyolefin resins, polycarbonate resins, polyetheretherketone resins, polyurethane resins, etc.

[0082] Cellulose resins include: cellulose acetate, propionate, butyrate, and mixed esters thereof. Preferred are triacetylcellulose, diacetylcellulose, cellulose acetate-propionate, and cellulose acetate-butyrate. Commercially available cellulose resin films include: "Fuji-TAC TD" (trade name, sold by Fuji Film Co., Ltd.) and "Konica Minolta TAC Film KC" (trade name, sold by Konica Minolta Opto Co., Ltd.).

[0083] The acrylic resin film is a film formed by mixing and melt-blending an acrylic resin with a methacrylic resin and additives as required. The methacrylic resin is a polymer mainly composed of methacrylates. The methacrylic resin can be a single polymer of a methacrylate, a copolymer of two or more methacrylates, or a copolymer of methacrylate and acrylate. Examples of methacrylates include methyl methacrylate, ethyl methacrylate, and butyl methacrylate, which are alkyl esters of methacrylic acid with 1 to 4 carbon atoms. The acrylates that can copolymerize with methacrylates are preferably alkyl esters of acrylic acid with 1 to 8 carbon atoms, specifically including methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate. Furthermore, it can also be a copolymer with a compound having at least one polymerizable carbon-carbon double bond (e.g., aromatic vinyl compounds such as styrene or vinyl cyanides such as acrylonitrile).

[0084] In the protective film, on the opposite side of the surface in contact with the polarizer, one or more surface treatment layers may be provided as required. Examples of surface treatment layers include: hard coating, anti-glare layer, anti-reflective layer and antistatic layer.

[0085] The protective film is bonded to the polarizer through an adhesive layer or a bonding agent layer. The bonding of the polarizer and the protective film can use conventional adhesive compositions or conventional bonding agent compositions. In the case where the polarizer is a single-sided protective film with a protective film on only one surface layer of the polarizer, the polarizer is bonded to the bonding agent layer obtained from the substrate-free double-sided adhesive sheet of the present invention. In the case where the polarizer is a double-sided protective film with a protective film on both surface layers of the polarizer, the protective film is bonded to the bonding agent layer obtained from the substrate-free double-sided adhesive sheet of the present invention. Preferably, the protective film in contact with the bonding agent layer is a triacetyl cellulose film, an acrylic resin film, a polyolefin resin film, or a polycarbonate resin film.

[0086] <Phase difference film>

[0086] The retardation film is an optical film exhibiting optical anisotropy. Examples include: an extended film obtained by stretching a resin film composed of polyvinyl alcohol resin, polycarbonate resin, polyester resin, polyaryl ester resin, polyimide resin, olefin resin, cycloolefin resin, styrene resin, polyvinyl chloride and polyether vinyl chloride resins, polyvinylidene fluoride / polymethyl methacrylate, liquid crystal polyester resin, cellulose resin containing triacetyl cellulose, ethylene-vinyl acetate copolymer saponification, polyvinyl chloride resin, acrylic resin, etc., by approximately 1.01 to 6 times. Preferably, it is a resin film that has been uniaxially or biaxially stretched from a cycloolefin resin film, a cellulose resin film, a polyester resin film, or a polycarbonate film. Furthermore, in this specification, the retardation film includes zero-retardation films, as well as films referred to as uniaxial retardation films, low photoelasticity coefficient retardation films, wide-viewing-angle retardation films, etc. Furthermore, the phase retardation film can be a single-layer structure or a multi-layer structure.

[0087] Cyclic olefin resins may include: thermoplastic resins containing cyclic olefin monomer units such as norcamphene, tetracyclododecene or their derivatives; hydrides of ring-opening polymers of cyclic olefins or ring-opening copolymers of two or more cyclic olefins; addition copolymers of cyclic olefins and chain olefins or aromatic compounds containing vinyl groups; and polar groups may also be introduced.

[0088] Commercially available thermoplastic cyclic olefin resins include, for example: "TOPAS" manufactured by TOPAS ADVANCED POLYMERS GmbH of Germany and sold by POLYPLASTICS Co., Ltd. of Japan; "ARTON (registered trademark)" sold by JSR Co., Ltd.; "ZEONEX (registered trademark)" and "ZEONOR (registered trademark)" sold by ZEON Co., Ltd. of Japan; and "APEL (registered trademark)" sold by Mitsui Chemicals Co., Ltd.

[0089] Methods for obtaining membranes by forming cyclic olefin resins include conventional membrane forming methods such as solvent casting or melt extrusion. Cyclic olefin resin membranes and cyclic olefin resin membranes that are further extended to impart phase difference are also commercially available. Specific examples include: "ARTON (registered trademark) membrane" sold by JSR Corporation, "ZEONOR (registered trademark) membrane" sold by ZEON Corporation of Japan, and "Essina (registered trademark)" and "SCA40" (trade name) sold by Sekisui Chemicals Co., Ltd.

[0090] Cellulose-based resin films are films composed of partially or completely esterified cellulose. Examples include films composed of cellulose acetate, propionate, butyrate, and mixed esters thereof. Triacetylcellulose films, diacetylcellulose films, cellulose acetate-propionate films, and cellulose acetate-butyrate films are preferred. Commercially available cellulose-based resin films include "Fuji-TAC TD" sold by Fuji Film Co., Ltd., and "Konica Minolta TAC Film KC" sold by Konica Minolta Opto Co., Ltd.

[0091] Polyester resins are polymers obtained by the condensation polymerization of diacids and diols, such as polyethylene terephthalate. Polycarbonate resins are polymers with carbonate bonds (-O-CO-O-) in the main chain, such as those obtained by the condensation polymerization of bisphenol A and carbonyl dichloride.

[0092] Zero-retardation film refers to a film whose frontal retardation Re and thickness retardation Rth are both -15 to 15 nm and are optically isotropic. Examples of zero-retardation films include resin films composed of cellulose-based resins, polyolefin-based resins (chain polyolefin resins, polycyclic olefin resins, etc.), or polyethylene terephthalate resins. From the viewpoint that retardation values ​​are easy to control and obtain, cellulose-based resins or polyolefin-based resins are preferred. Zero-retardation films can also be used as protective films. Examples of zero-retardation films include "Z-TAC" (trade name) sold by Fujifilm Co., Ltd., "Zero TAC (registered trademark)" sold by Konica Minolta Opto Co., Ltd., and "ZF-14" (trade name) sold by ZEON Co., Ltd. of Japan.

[0093] Methods for obtaining membranes by forming films from cellulose-based resins or polyolefin-based resins include: solvent casting, in which resin dissolved in a solvent is cast onto a metal belt or drum and dried to remove the solvent, and melt extrusion, in which resin is heated to above its melting temperature, kneaded, extruded from a die, and cooled by a cooling drum, to obtain a film. From a production point of view, melt extrusion is preferable for polyolefin-based resins, while solvent casting is preferable for cellulose-based resins.

[0094] Examples of phase retardation films include films that exhibit optical anisotropy through the coating and alignment of liquid crystal compounds, or films that exhibit optical anisotropy through the coating of inorganic layered compounds. Examples of such films include: temperature-compensated phase retardation films, "NH Film" (trade name: tilted-aligned rod-shaped liquid crystal film) sold by JX Nippon Minerals & Energy Co., Ltd., "WV Film" (trade name: tilted-aligned disc-shaped liquid crystal film) sold by Fuji Film Co., Ltd., "VAC Film" (trade name: fully biaxially aligned film) sold by Sumitomo Chemical Co., Ltd., and "new VAC Film" (trade name: biaxially aligned film) sold by Sumitomo Chemical Co., Ltd., etc.

[0095] The laminate of the present invention is a laminate formed by laminating an adhesive layer obtained from the substrate-free double-sided adhesive sheet of the present invention with an optical component, which can suppress unintended separation in the adhesive layer. Therefore, when the laminate of the present invention is bonded to other optical components, it can adhere well and suppress the degradation of the optical properties of the optical components. The laminate of the present invention can be ideally used in image display devices such as organic EL display devices or liquid crystal display devices.

[0095] [Example]

[0096] The following examples and comparative examples illustrate the present invention in more detail, but the present invention is not limited to these examples. Unless otherwise specified, "%" and "parts" in the examples and comparative examples refer to mass percentage and mass parts.

[0097] (1) Preparation of the release film

[0097] (1-1) Preparation of composition a for forming release treatment layer

[0097] 100 parts of a toluene solution of polysiloxane resin (manufactured by Dow Toray Co., Ltd., trade name: "LTC759" (30% solids concentration)) used as the release agent, were mixed with 1 part of a 1,3-vinyl-1,1,3,3-tetramethyldisiloxane platinum complex (obtained from Dow Toray Co., Ltd., trade name: "SRX212") used as a catalyst. The resulting mixture was then prepared by mixing toluene and methyl ethyl ketone in a mixed solvent (mass ratio 1:1) to a solids concentration of 1.5%, resulting in composition a for forming a release layer.

[0098] (1-2) Preparation of composition b for release treatment layer formation

[0098] To 100 parts of a toluene solution of polysiloxane (manufactured by Dow Toray Co., Ltd., trade name: "LTC759" (30% solid content)) as a heavy release additive, 10 parts of a xylene and ethylbenzene solution of vinyl-modified polysiloxane (manufactured by Dow Toray Co., Ltd., trade name: "SD7292" (65% solid content, containing 3% by mass of vinyl in the solid content) as a release treatment layer formation additive were further added, and otherwise, composition b for forming a release treatment layer was obtained in the same manner as composition a for forming a release treatment layer.

[0099] (1-3) Preparation of composition c for forming release treatment layer

[0099] 100 parts of release treatment agent "LTC759" and 1 part of mixed catalyst "SRX212" were mixed with methyl ethyl ketone and prepared to a solid content concentration of 1.13% to obtain composition c for forming release treatment layer.

[0100] (1-4) Preparation of composition d for forming release treatment layer

[0100] 100 parts of release treatment agent "LTC759", 1 part of mixed catalyst "SRX212" and 1 part of heavy peeling additive "SD7292" were mixed with methyl ethyl ketone and prepared to a solid content concentration of 1.13% to obtain composition d for forming release treatment layer.

[0101] (1-5) Preparation of composition e for forming release treatment layer

[0101] 100 parts of release agent "SRX211" (manufactured by Dow Toray Co., Ltd., solid content concentration 30%) and 1 part of mixed catalyst "SRX212" were used. The resulting mixture was mixed with a mixed solvent of toluene and methyl ethyl ketone (mass ratio 1:1) to obtain composition e for forming release layer with a solid content concentration of 1.13%.

[0102] (1-6) Preparation of composition f for release treatment layer formation

[0102] 100 parts of release agent "SRX211", 1 part of mixed catalyst "SRX212", and 1 part of heavy peeling additive "SD7292" were used. The resulting mixture was prepared by mixing toluene and methyl ethyl ketone in a mixed solvent (mass ratio 1:1) to a solids concentration of 1.13% to obtain composition f for forming release layer.

[0103] (1-7) Preparation of composition g for release treatment layer formation

[0103] 100 parts of release treatment agent "SRX211", 1 part of mixed catalyst "SRX212", and 5 parts of heavy peeling additive "SD7292" were used. The resulting mixture was prepared by mixing toluene and methyl ethyl ketone in a mixed solvent (mass ratio 1:1) to a solids concentration of 1.13% to obtain g of composition for release treatment layer formation.

[0104] (1-8) Fabrication of release film 1

[0104] A transparent polyethylene terephthalate (PET) film (Tetoron G2 film, manufactured by Teijin-DuPont) with a thickness of 38 μm was prepared. Next, the release treatment layer forming composition a obtained in (1-1) was coated onto one side of the PET film with a thickness of 190 nm after drying using a thin film coater, and dried at 120°C for 1 minute to form a release treatment layer on the PET film. The resulting film was stored at a temperature of 23°C and a relative humidity of 55% for more than 5 days to obtain a release film 1 (light release film) without a heavy release additive formed on the PET film.

[0105] (1-9) Fabrication of the release film 2

[0105] Use the release treatment layer forming composition b obtained in (1-2) instead of the release treatment layer forming composition a, and otherwise obtain, in the same way as the release film 1, a release film 2 (re-release film) with a release treatment layer containing a heavy release additive formed on a PET film.

[0106] (1-10) Fabrication of the release film 3

[0106] A transparent polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical Corporation, trade name: DIAFOIL T190E38) with a thickness of 38 μm was prepared. Next, the release treatment layer forming composition c was coated onto one side of the PET film with a thickness of 100 nm after drying using a bar coater. The film was dried at 100°C for 3 minutes to form a release treatment layer on the PET film. The resulting film was stored at a temperature of 23°C and a relative humidity of 60% for more than 5 days to obtain release film 3 (light release film).

[0107] (1-11) Fabrication of the release film 4

[0107] Instead of using release treatment layer to form composition c, release treatment layer is formed composition d. Otherwise, release film 4 (re-release film) is obtained by the same method as release film 3.

[0108] (1-12) Fabrication of the release film 5

[0108] Instead of using release treatment layer to form composition c, release treatment layer is formed composition e. Otherwise, release film 5 (light release film) is obtained by the same method as release film 3.

[0109] (1-13) Fabrication of the release film 6

[0109] The release treatment layer is used to form composition c instead of release treatment layer to form composition f. Otherwise, the release film 6 (re-release film) is obtained by the same method as the release film 3.

[0110] (1-14) Fabrication of the release film 7

[0110] Instead of using release treatment layer to form composition c, release treatment layer is formed composition g. Otherwise, release film 7 (re-release film) is obtained by the same method as release film 3.

[0111] (1-15) Fabrication of the release film 8

[0111] The drying temperature was changed from 100°C to 80°C, and otherwise the same method as that used for the peeling film 3 was used to obtain the peeling film 8 (light peeling film).

[0112] (1-16) Fabrication of the release film 9

[0112] The drying temperature was changed from 100°C to 80°C. Otherwise, the same method as that used for the peeling film 4 was used to obtain the peeling film 9 (repeating film).

[0113] (2) Preparation of adhesive composition

[0113] (2-1) Preparation of acrylic resin solution 1

[0113] A mixed solution of 40 parts ethyl acetate, 34 parts butyl acrylate, 10 parts methyl acrylate, 0.5 parts 2-hydroxyethyl acrylate, and 0.5 parts acrylic acid was placed in a reaction vessel equipped with a cooling pipe, a nitrogen inlet pipe, a thermometer, and a stirrer. Nitrogen was used to replace the air in the apparatus to eliminate oxygen, and the internal temperature was raised to 55°C. Then, a solution of 0.14 parts azobisisobutyronitrile dissolved in 9.86 parts ethyl acetate was added as a polymerization initiator. After adding the initiator, the temperature was maintained for 1 hour. Then, the internal temperature was maintained at 54-56°C, and ethyl acetate was continuously added to the reaction vessel at a rate of 17.3 parts / hr. The addition of ethyl acetate was stopped when the concentration of the acrylic resin reached 35%. This temperature was maintained for 12 hours after the start of ethyl acetate addition. Finally, ethyl acetate was added to adjust the concentration of the acrylic resin to 20%, thus preparing acrylic resin solution 1. The resulting acrylic resin had a weight-average molecular weight (Mw) of 1.3 million and a molecular weight distribution (Mw / Mn) of 4.2. Furthermore, Mw and Mn were measured using two tandemly connected "TSKgel GMHHR-H(S)" columns manufactured by Tosoh Corporation in a GPC apparatus, with tetrahydrofuran as the dissolution solution. Measurements were performed based on standard polystyrene conversion under the following conditions: sample concentration of 2 mg / mL, sample introduction volume of 100 μL, temperature of 40°C, and flow rate of 1 mL / min.

[0114] (2-2) Preparation of adhesive composition 1

[0114] Relative to 100 parts of the solid component of the acrylic resin solution 1 obtained in (2-1), 0.5 parts of a crosslinking agent (manufactured by Tosoh Corporation: trade name "Coronate L" (ethyl acetate solution of trimethylolpropane adduct of toluene diisocyanate (solid component concentration 75% by mass)) were added to the effective component, and then ethyl acetate was added to make the solid component concentration 7% to obtain adhesive composition 1.

[0115] (2-3) Preparation of adhesive composition 2

[0115] Relative to 100 parts of solid component of acrylic resin solution 1 obtained in (2-1), 0.5 parts of crosslinking agent (Mitsui Chemicals: trade name "D-103" (ethyl acetate solution of trimethylolpropane adduct of toluene diisocyanate (solid component concentration 75% by mass)) were added to the effective component, and then ethyl acetate was added to make the solid component concentration 7% to obtain adhesive composition 2.

[0116] (2-4) Preparation of adhesive composition 3

[0116] Relative to 100 parts of the solid component of the acrylic resin solution 1 obtained in (2-1), 0.5 parts of crosslinking agent "D-103" and 0.01 parts of silane compound (manufactured by Shin-Etsu Chemical Industry Co., Ltd.: trade name "KBM-403" (3-epoxypropoxypropyltrimethoxysilane)) were added to the effective component, and ethyl acetate was added to make the solid component concentration 7% to obtain adhesive composition 3.

[0117] (2-5) Preparation of adhesive composition 4

[0117] Compared with 100 parts of solid component of acrylic resin solution 1 obtained in (2-1), 0.5 parts of crosslinking agent "D-103" and 0.01 parts of silane compound (manufactured by Shin-Etsu Chemical Industry Co., Ltd.: trade name "KR-519" (thiol-containing polysiloxane oligomer)) were added to the effective component, and ethyl acetate was added to make the solid component concentration 7% to obtain adhesive composition 4.

[0118] (3) Fabrication of substrate-free double-sided adhesive sheet

[0118] [Example 1]

[0118] After applying the adhesive composition 1 prepared in (2-2) above onto the release layer of the release film 1 using a coater, it is dried at 100°C for 1 minute to obtain an adhesive layer with a thickness of 5 μm. The adhesive surface exposed on the opposite side of the release film 1 in the obtained adhesive layer is laminated with the release layer side of the release film 2 to adhere the release film 2. The resulting laminate is left to stand for at least 7 days at a temperature of 23°C and a relative humidity of 55% to produce a substrate-free double-sided adhesive sheet 1.

[0119] [Example 2]

[0119] After applying the adhesive composition 2 prepared in (2-3) above onto the release layer of the release film 3 using a coater, it is dried at 100°C for 1 minute to obtain an adhesive layer with a thickness of 5 μm. The adhesive surface exposed on the opposite side of the release film 3 in the obtained adhesive layer is laminated with the release layer side of the release film 4 to adhere the release film 4. The resulting laminate is left to stand at 23°C and 60% relative humidity for more than 7 days to produce a substrate-free double-sided adhesive sheet 2.

[0120] [Example 3]

[0120] After applying the adhesive composition 2 prepared in (2-3) above onto the release layer of the release film 5 using a coater, it is dried at 100°C for 1 minute to obtain an adhesive layer with a thickness of 5 μm. The adhesive surface exposed on the opposite side of the release film 5 in the obtained adhesive layer is laminated with the release layer side of the release film 6 to adhere the release film 6. The resulting laminate is left to stand at 23°C and 60% relative humidity for more than 7 days to produce a substrate-free double-sided adhesive sheet 3.

[0121] [Example 4]

[0121] After applying the adhesive composition 3 prepared in (2-4) above onto the release treatment layer of the release film 3 using a coater, it is dried at 100°C for 1 minute to obtain an adhesive layer with a thickness of 5 μm. The adhesive surface exposed on the opposite side of the release film 3 in the obtained adhesive layer is laminated with the release treatment layer side of the release film 4 to bond the release film 4. The resulting laminate is placed in an environment with a temperature of 23°C and a relative humidity of 60% for more than 7 days to produce a substrate-free double-sided adhesive sheet 4.

[0122] [Example 5]

[0122] After applying the adhesive composition 3 prepared in (2-4) above onto the release layer of the release film 5 using a coater, it is dried at 100°C for 1 minute to obtain an adhesive layer with a thickness of 5 μm. The adhesive surface exposed on the opposite side of the release film 5 in the obtained adhesive layer is laminated with the release layer side of the release film 6 to adhere the release film 6. The resulting laminate is left to stand at 23°C and 60% relative humidity for more than 7 days to produce a substrate-free double-sided adhesive sheet 5.

[0123] [Example 6]

[0123] After applying the adhesive composition 4 prepared in (2-5) above onto the release layer of the release film 5 using a coater, it is dried at 100°C for 1 minute to obtain an adhesive layer with a thickness of 5 μm. The adhesive surface exposed on the opposite side of the release film 5 in the obtained adhesive layer is laminated with the release layer side of the release film 7 to adhere the release film 7. The resulting laminate is left to stand at 23°C and 60% relative humidity for more than 7 days to produce a substrate-free double-sided adhesive sheet 6.

[0124] [Example 7]

[0124] After applying the adhesive composition 3 prepared in (2-4) above onto the release layer of the release film 8 using a coater, it is dried at 100°C for 1 minute to obtain an adhesive layer with a thickness of 5 μm. The adhesive surface exposed on the opposite side of the release film 8 in the obtained adhesive layer is laminated with the release layer side of the release film 9 to adhere the release film 9. The resulting laminate is left to stand at 23°C and 60% relative humidity for more than 7 days to produce a substrate-free double-sided adhesive sheet 7.

[0125] [Comparative Example 1]

[0125] After applying the adhesive composition 1 prepared in (2-2) above to the release treatment surface of the release film 2 using a coater, it is dried at 100°C for 1 minute to obtain an adhesive layer with a thickness of 5 μm. The adhesive surface exposed on the opposite side of the release film 2 in the obtained adhesive layer is laminated with the release treatment layer side of the release film 1 to adhere the release film 1. The obtained laminate is placed in an environment with a temperature of 23°C and a relative humidity of 55% for more than 7 days to produce a substrate-free double-sided adhesive sheet 8.

[0126] [Comparative Example 2]

[0126] After applying the adhesive composition 3 prepared in (2-4) above onto the release treatment layer of the release film 4 using a coater, it is dried at 100°C for 1 minute to obtain an adhesive layer with a thickness of 5 μm. The adhesive surface exposed on the opposite side of the release film 4 in the obtained adhesive layer is laminated with the release treatment layer side of the release film 3 to adhere the release film 3. The resulting laminate is left to stand in an environment of 23°C and 60% relative humidity for more than 7 days to produce a substrate-free double-sided adhesive sheet 9.

[0127] [Comparative Example 3]

[0127] After applying the adhesive composition 3 prepared in (2-4) above onto the release layer of the release film 6 using a coater, it is dried at 100°C for 1 minute to obtain an adhesive layer with a thickness of 5 μm. The adhesive surface exposed on the opposite side of the release film 6 in the obtained adhesive layer is laminated with the release layer side of the release film 5 to adhere the release film 5. The resulting laminate is left to stand at 23°C and 60% relative humidity for more than 7 days to produce a substrate-free double-sided adhesive sheet 10.

[0128] (Method for measuring the water contact angle of the adhesive layer)

[0128] After peeling off the release film 1 (light release film) from the substrate-free double-sided adhesive sheet 1 prepared in Example 1, the water contact angle was measured immediately after dripping ion-exchanged water onto the exposed adhesive surface using a water contact angle meter (FACE CA-X type (manufactured by Kyowa Interface Chemical Co., Ltd.)) at an environment of 23°C and 55% relative humidity. Then, a 38μm PET film was bonded to the exposed adhesive surface, and the release film 2 (heavy release film) on the opposite side was peeled off. The water contact angle was measured immediately after dripping ion-exchanged water onto the exposed adhesive surface using a water contact angle meter (FACE CA-X type (manufactured by Kyowa Interface Chemical Co., Ltd.)) at an environment of 23°C and 55% relative humidity.

[0129] For the substrate-free double-sided adhesive sheets 2 to 7 prepared in Examples 2 to 7, the water contact angle of the adhesive layer was measured. Similar to Example 1, after measuring the water contact angle of the adhesive layer surface exposed due to the peeling of the light peel film, the water contact angle of the adhesive layer surface exposed due to the peeling of the heavy peel film was measured.

[0130] Furthermore, after peeling off the release film 2 (heavy release film) from the substrate-free double-sided adhesive sheet 8 prepared in Comparative Example 1, the water contact angle was measured immediately after dripping ion-exchanged water onto the exposed adhesive surface using a water contact angle meter (FACE CA-X type (manufactured by Kyowa Interface Chemical Co., Ltd.)) at an environment of 23°C and 55% relative humidity. Then, a 38μm PET film was bonded to the exposed adhesive surface, and the release film 1 (light release film) on the opposite side was peeled off. The water contact angle was measured immediately after dripping ion-exchanged water onto the exposed adhesive surface using a water contact angle meter (FACE CA-X type (manufactured by Kyowa Interface Chemical Co., Ltd.)) at an environment of 23°C and 55% relative humidity.

[0131] The water contact angle of the adhesive layer was also measured for the substrate-free double-sided adhesive sheets 9 and 10 prepared in Comparative Examples 2 and 3. Similar to Comparative Example 1, after measuring the water contact angle of the adhesive layer surface exposed by the peeling of the heavy peel film, the water contact angle of the adhesive layer surface exposed by the peeling of the light peel film was measured.

[0132] In addition, the water contact angle was calculated using the θ / 2 method. The measurement was performed 5 times and the average value was taken as the measured value. The results are shown in [Table 1].

[0133] (Method for measuring peel sensitivity)

[0133] The substrate-free double-sided adhesive sheets 1 and 8 prepared in Example 1 and Comparative Example 1 were cut into 50mm wide × 190mm pieces. The release film 2 (heavy release film) side of the obtained test piece was fixed to the glass plate using double-sided tape. Using Autograph (AGS-X 50N, manufactured by Shimadzu Corporation), the glass plate was clamped into the lower clamp and the release film 1 (light release film) was clamped into the upper clamp. The state of the adhesive layer transferring to the release film 1 (light release film) when peeled at a speed of 300mm / min in the 180° direction was judged.

[0133] ○: No adhesive layer was observed to transfer to the release film 1 (light release film) or only a small amount was observed.

[0133] ×: Confirm that the adhesive layer has been fully transferred to the release film 1 (light release film).

[0134] The peel sensitivity of substrate-free double-sided adhesive sheets 2 to 7, 9, and 10 prepared in Examples 2 to 7 and Comparative Examples 2 to 3 was measured and evaluated. The results are shown in [Table 1]. As with Example 1 and Comparative Example 1, the light release film was clamped to confirm the state of the adhesive layer transferring to the light release film.

[0135] [Table 1]

[0136] In Comparative Examples 1 to 3, where an adhesive composition was coated onto a release film (heavy release film) containing a release treatment layer with a heavy release additive to produce a substrate-free double-sided adhesive sheet, unexpected separation occurred. On the other hand, in Examples 1 to 7, where an adhesive composition was coated onto a release film (light release film) without a release treatment layer with a heavy release additive to produce a substrate-free double-sided adhesive sheet, no unexpected separation occurred and good peel sensitivity was obtained.

Claims

1. A method for manufacturing a substrate-free double-sided adhesive sheet, the substrate-free double-sided adhesive sheet comprising an adhesive layer, a heavy-release film deposited on one side of the adhesive layer, and a light-release film deposited on the other side of the adhesive layer, the manufacturing method comprising: a coating step of coating an adhesive composition onto the light-release film to form a coating layer; a drying step of drying the coating layer to obtain the adhesive layer; and a lamination step of laminating the heavy-release film onto the adhesive layer, wherein... The aforementioned heavy-release film is a film in which a release treatment layer containing a heavy-release additive is formed on a plastic film. The aforementioned light-release film is a film in which a release treatment layer without a heavy-release additive is formed on a plastic film. The aforementioned heavy-release additive is a polysiloxane resin having one or more reactive sites in its molecule.

2. An adhesive layer disposed between a light release film and a heavy release film, wherein, The aforementioned heavy-release film is a film in which a release treatment layer containing a heavy-release additive is formed on a plastic film. The aforementioned light-release film is a film in which a release treatment layer without a heavy-release additive is formed on a plastic film. The aforementioned heavy-release additive is a polysiloxane resin having one or more reactive sites in its molecule. The water contact angle of one surface of the adhesive layer differs from the water contact angle of the other surface by more than 3 degrees and less than 50 degrees.

3. A substrate-free double-sided adhesive sheet, comprising an adhesive layer, a heavy-duty release film deposited on one side of the adhesive layer, and a light-duty release film deposited on the other side of the adhesive layer, wherein, The aforementioned heavy-release film is a release treatment layer containing heavy-release additives formed on a plastic film. The aforementioned light-release film is a release treatment layer without heavy-release additives formed on a plastic film. The aforementioned heavy-release additive is a polysiloxane resin having one or more reactive sites in its molecule. The water contact angle of the light-release film side surface of the aforementioned adhesive layer differs from the water contact angle of the heavy-release film side surface of the aforementioned adhesive layer by more than 3 degrees and less than 50 degrees.

4. A laminate, sequentially comprising an optical component, an adhesive layer, and a release film, wherein, The aforementioned heavy-release film is a release treatment layer containing a heavy-release additive formed on a plastic film. The aforementioned heavy-release additive is a polysiloxane resin having one or more reactive sites in its molecule. The water contact angle of the optical component side surface of the aforementioned adhesive layer differs from the water contact angle of the heavy-release film side surface of the aforementioned adhesive layer by more than 3 degrees and less than 50 degrees.

5. A method for manufacturing a laminate, the laminate sequentially comprising an optical component, an adhesive layer, and a release film, the method comprising: a step of manufacturing a substrate-free double-sided adhesive sheet by means of the substrate-free double-sided adhesive sheet manufacturing method described in claim 1; and a bonding step of peeling the release film from the aforementioned substrate-free double-sided adhesive sheet and bonding the adhesive layer to the optical component.