Method for manufacturing a substrate-free double-sided adhesive sheet

Abstract

To provide a method of manufacturing a substrate-less double-sided adhesive sheet capable of suppressing transfer of an adhesive layer to a light release film when the light release film is peeled off, and to provide a substrate-less double-sided adhesive sheet.SOLUTION: A method of manufacturing a substrate-less double-sided adhesive sheet including an adhesive layer, a light release film laminated on one side of the adhesive layer, and a heavy release film laminated on the other side of the adhesive layer, comprises: a coating step of applying an adhesive composition to a light release film to form a coating layer; a drying step of drying the coating layer to obtain an adhesive layer; and a lamination step of laminating a heavy release film onto the adhesive layer.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a substrate-free double-sided adhesive sheet and a laminate using the same.

Background Art

[0002] A polarizing plate formed by laminating and bonding a protective film on one or both sides of a polarizer is an optical member used in image display devices such as liquid crystal display devices and organic electroluminescence (organic EL) display devices. Optical members such as polarizing plates are often used by bonding them to other members (for example, optical members such as liquid crystal cells in liquid crystal display devices) through an adhesive layer. This adhesive layer may be obtained from a substrate-free double-sided adhesive sheet.

[0003] A substrate-free double-sided adhesive sheet generally has a configuration in which a release film (light release film) with a relatively low release force is laminated on one surface of an adhesive layer that does not have a substrate as a core material, and a release film (heavy release film) with a relatively high release force is laminated on the other surface of the adhesive layer. The substrate-free double-sided adhesive sheet is manufactured by applying and drying an adhesive composition on the heavy release film to form an adhesive layer and laminating the light release film on the adhesive layer. When bonding optical components together using a substrate-less double-sided adhesive sheet, the usual method involves peeling off the light release film from the substrate-less double-sided adhesive sheet, bonding the exposed adhesive layer to one optical component, then peeling off the heavy release film and laminating the exposed adhesive layer to the other optical component to bond the components together. However, if the difference in peeling force between the light release film and the heavy release film laminated on both sides of the substrate-less double-sided adhesive sheet is small, when peeling off the light release film from the substrate-less double-sided adhesive sheet, a defect in the adhesive layer (separation) may occur, where a portion of the adhesive layer follows the light release film, is stretched between the heavy and light release films, breaks, and transfers to the light release film side. Attempting to bond optical components together using an adhesive layer that has experienced separation can result in problems such as the optical components not adhering to each other at all, or the unevenness of the adhesive layer caused by the separation causing light reflection and degrading the optical properties of optical components such as polarizers.

[0004] As a method to suppress peeling defects (separation), Patent Document 1 describes using a heavy-release film in which a release treatment layer is formed on a plastic film from a composition containing a silicone release agent, which is a heavy-release additive, thereby increasing the peeling force of the heavy-release film and increasing the difference in peeling force between the light-release film and the heavy-release film. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 07-041736 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In recent years, with the thinning of liquid crystal displays and organic EL displays, there has been a demand for thinning of polarizing plates and adhesive layers as well. However, thinning the adhesive layer reduces the rigidity of the adhesive layer itself, making it more likely for the adhesive layer to transfer (separate) to the release film when peeling the release film from the substrate-less double-sided adhesive sheet. In some cases, the method described in Patent Document 1 was insufficient in suppressing this separation. [Means for solving the problem]

[0007] The inventors of this invention have diligently studied and conducted research to solve the above problems, and as a result, have completed this invention. In other words, the present invention includes the following inventions [1] to [9]. [1] A method for manufacturing a substrate-less double-sided adhesive sheet, comprising an adhesive layer, a heavy release film laminated on one side of the adhesive layer, and a light release film laminated on the other side of the adhesive layer, A coating step in which an adhesive composition is applied to the aforementioned light release film to form a coating layer, A drying step of drying the coating layer to obtain the adhesive layer, A method for manufacturing a substrate-less double-sided adhesive sheet, comprising a lamination step of laminating a heavy-release film onto the adhesive layer. [2] The double-release film is a film in which a release treatment layer containing a double-release additive is formed on a plastic film, The method for manufacturing a substrate-less double-sided adhesive sheet according to [1], wherein the light-release film is a film in which a release treatment layer that does not contain a heavy-release additive is formed on a plastic film. [3] An adhesive layer in which the difference between the water contact angle of one surface and the water contact angle of the other surface is 3 degrees or more. [4] A substrate-less double-sided adhesive sheet comprising an adhesive layer, a heavy release film laminated on one side of the adhesive layer, and a light release film laminated on the other side of the adhesive layer, A substrate-less double-sided adhesive sheet in which the water contact angle on the surface of the adhesive layer on the light release film side is smaller than the water contact angle on the surface of the adhesive layer on the heavy release film side. [5] The substrate-less double-sided adhesive sheet according to [4], wherein the difference between the water contact angle on the surface of the adhesive layer on the light release film side and the water contact angle on the surface of the adhesive layer on the heavy release film side is 3 degrees or more. [6] The double-release film is a film in which a release treatment layer containing a double-release additive is formed on a plastic film, The substrate-less double-sided adhesive sheet according to [4] or [5], wherein the light release film is a film in which a release treatment layer that does not contain a heavy release additive is formed on a plastic film. [7] A laminate comprising an optical component, an adhesive layer, and a double-release film in this order, A laminate in which the water contact angle of the surface of the adhesive layer on the optical member side is smaller than the water contact angle of the surface of the adhesive layer on the release film side. [8] The laminate according to [7], wherein the difference between the water contact angle of the optical member side surface of the adhesive layer and the water contact angle of the double-peel film side surface of the adhesive layer is 3 degrees or more. [9] The laminate according to [7] or [8], wherein the double-release film is a film in which a release treatment layer containing a double-release additive is formed on a plastic film.

[10] A method for manufacturing a laminate comprising an optical component, an adhesive layer, and a double-release film in this order, A step of manufacturing a substrate-less double-sided adhesive sheet by the manufacturing method described in [1] or [2], A method for manufacturing a laminate, comprising a lamination step of peeling off a light release film from the substrate-less double-sided adhesive sheet and bonding the adhesive layer and an optical member. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a method for manufacturing a substrate-less double-sided adhesive sheet and a substrate-less double-sided adhesive sheet that can suppress the transfer of the adhesive layer to the light-release film when peeling off the light-release film. [Modes for carrying out the invention]

[0009] The present invention relates to a method for manufacturing a substrate-less double-sided adhesive sheet comprising an adhesive layer, a heavy release film laminated on one side of the adhesive layer, and a light release film laminated on the other side of the adhesive layer, characterized in that it includes a coating step of applying an adhesive composition to 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] <Base material-free double-sided adhesive sheet> The substrate-less double-sided adhesive sheet of the present invention has a configuration in which a light release film is laminated on one side of the adhesive layer and a heavy release film is laminated on the other side of the adhesive layer. Furthermore, the substrate-less double-sided adhesive sheet of the present invention is characterized in that the water contact angle on the surface of the adhesive layer on the light release film side is smaller than the water contact angle on the surface of the adhesive layer on the heavy release film side.

[0011] <Release film> In the substrate-less double-sided adhesive sheet of the present invention, the terms "light release film" and "heavy release film" refer to the relative release force of each release film, and while the release films are not particularly limited, it is preferable that they are release films composed of a plastic film and a release treatment layer. In a substrate-less double-sided adhesive sheet, the light release film and the heavy release film are each laminated 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 in contact with the surface of the adhesive layer.

[0012] Examples of plastic films include polyester films such as polyethylene terephthalate film, polybutylene terephthalate film, and polyethylene naphthalate film, as well as polyolefin films such as polypropylene film. Among these, polyethylene terephthalate film is preferred from the viewpoint of optical properties and quality, and biaxially oriented polyethylene terephthalate film is preferred because of its excellent dimensional stability.

[0013] The release treatment layer can be formed from a composition for forming a release treatment layer. The release treatment composition is a resin composition containing a resin, and may further contain additives such as a release additive to control the release force. From the viewpoint of ease of controlling the release force, as the double-release film, it is preferable to use a double-release film having a release treatment layer containing a double-release additive. As the easy-release film, it is preferable to use an easy-release film having a release treatment layer that does not contain a double-release additive. The resin constituting the composition for forming the release treatment layer is not particularly limited, and examples thereof include silicone resins, alkyd resins, acrylic resins, and long-chain alkyl resins. Among them, silicone resins are preferred.

[0014] Examples of the silicone resin include silicone resins having dimethylpolysiloxane as a basic skeleton. The silicone resin may be any of addition reaction type, condensation reaction type, ultraviolet curing type, electron beam curing type, etc., but an addition reaction type silicone resin is preferable. The addition reaction type silicone resin has high reactivity and excellent productivity, and has merits such as small change in release force after production and no curing shrinkage compared with the condensation reaction type, and is preferable.

[0015] Specific examples of the addition reaction type silicone resin include, for example, organopolysiloxanes having two or more alkenyl groups having 2 to 10 carbon atoms such as vinyl group, allyl group, propenyl group, and hexenyl group at the terminal and / or side chain of the molecule. As the addition type reactive silicone resin, commercially available products may be used, and examples thereof include "LTC759" (manufactured by Dow Corning Toray Co., Ltd.), "LTC750A" (manufactured by Dow Corning Toray Co., Ltd.), "LTC755" (manufactured by Dow Corning Toray Co., Ltd.), "KS-847" (manufactured by Shin-Etsu Chemical Co., Ltd.), etc. When using an addition reaction type silicone resin, it is preferable to use a crosslinking agent and a catalyst in combination.

[0016] Examples of crosslinking agents include organopolysiloxanes having hydrogen atoms bonded to at least two silicon atoms in one molecule, specifically dimethylhydrogensiloxy group-ended dimethylsiloxane-methylhydrogensiloxane copolymers, trimethylsiloxy group-ended dimethylsiloxane-methylhydrogensiloxane copolymers, trimethylsiloxy group-ended methylhydrogenpolysiloxanes, and poly(hydrogensilsesquioxanes).

[0017] Examples of catalysts include particulate platinum, particulate platinum adsorbed on a carbon powder support, chloroplatinic acid, alcohol-modified chloroplatinic acid, olefin complexes of chloroplatinic acid, and platinum metal compounds such as palladium and rhodium. By using such catalysts, the curing reaction of the release layer forming composition can be made more efficient. Commercially available catalysts may also be used, such as "SRX212" (manufactured by Dow-Toray Industries, Inc.), "SRX212P" (manufactured by Dow-Toray Industries, Inc.), and "CAT-PL-50T" (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0018] When manufacturing a double-release film, it is preferable that the release layer forming composition constituting the release layer contains a double-release additive. The heavy-release additive is preferably a polyorganosiloxane having one or more reactive sites in its molecule, and more preferably a silicone resin having one or more reactive sites in its molecule. Examples of reactive sites include hydrolyzable groups such as hydroxyl groups, carboxyl groups, alkoxy groups having 1 to 6 carbon atoms, halogen atoms, acyloxy groups, and oxime groups; and alkenyl groups such as vinyl groups. Examples of silicone resins include monofunctional siloxane units [R3SiO 1 / 2 The M unit is [SiO], and the tetrafunctional siloxane unit is [SiO]. 4 / 2An example is an MQ resin containing a Q unit which is ]. The three Rs in the M unit each independently represent a hydrogen atom, a hydroxyl group, or an organic group, and it is preferable that one or more of these three Rs are the reactive sites described above. The heavy peeling additive is preferably a polyorganosiloxane having an alkenyl group as the reactive site, more preferably a vinyl-modified polyorganosiloxane, and particularly preferably a vinyl-modified silicone resin.

[0019] The heavy release additive preferably has a weight-average molecular weight (Mw) of 500 to 500,000 in terms of standard polystyrene, determined by gel permeation chromatography (GPC), more preferably 800 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 to the resin (preferably silicone resin) is poor, and migration to the surface of the adhesive layer tends to occur when it is bonded to the adhesive layer. If the weight-average molecular weight exceeds 500,000, the viscosity of the heavy release additive becomes too high, making industrial synthesis difficult.

[0020] When a heavy release additive is added, the amount added is preferably 80 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less, per 100 parts by mass of resin. It is also preferably 0.01 parts by mass or more, and more preferably 0.1 parts by mass or more. If the amount of heavy release additive exceeds 80 parts by mass, the peeling force when peeling the heavy release film from the adhesive layer becomes too high, making peeling difficult. If the amount of heavy release additive is less than 0.01 parts by mass, when a substrate-less double-sided adhesive sheet is made by combining it with a release film that does not contain a heavy release additive (light release film), the difference in peeling force between the heavy release film and the light release film becomes small, and there is a tendency for peeling defects (separation) to occur where the adhesive layer transfers to the light release film side.

[0021] Furthermore, the release layer forming composition may contain additives other than those mentioned above as appropriate. Examples of additives include catalysts, dyes, and dispersants. In addition, the release layer forming composition may contain a dispersion medium or solvent as appropriate to adjust the viscosity during application to an appropriate range. Examples of dispersion media or solvents 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] A release film can be produced, for example, by applying a release treatment layer-forming composition diluted in a solvent to one surface of a plastic film using a known method, and then drying the resulting coating layer. Examples of coating methods include gravure coating, bar coating, spray coating, spin coating, air knife coating, roll coating, blade coating, gate roll coating, and die coating. Among these, gravure coating and bar coating are preferred, with gravure coating being more preferred. Furthermore, a drying method for the coating layer of the release treatment layer-forming composition can be, for example, 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. The drying time is preferably, for example, 5 seconds to 5 minutes.

[0023] The film 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 of the plastic film is the dominant factor and 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 film thickness of the plastic film, but it is usually 200 μm or less, and is preferably 150 μm or less, and more preferably 100 μm or less, as this facilitates the release of the release film. 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. It is also preferably 500 nm or less, more preferably 300 nm or less, and even more preferably 250 nm or less. By setting the thickness of the release treatment layer to 25 nm or more, it is possible to suppress repulsion when applying the release treatment layer forming composition, and to suppress variations in peeling force and the occurrence of partial separation. By making the thickness of the release layer 250 nm or less, blocking between release films can be suppressed.

[0024] <Adhesive layer> The adhesive composition forming the adhesive layer is not particularly limited, but is preferably an acrylic adhesive composition. The acrylic adhesive composition contains a (meth)acrylic resin and a crosslinking agent. The acrylic adhesive composition may further contain a silane compound and an antistatic agent. In this specification, (meth)acrylic resin means either acrylic resin or methacrylic resin, and the "(meth)" in (meth)acrylate, etc., has the same meaning.

[0025] (Meth)acrylic resins refer to polymers whose main component is structural units derived from (meth)acrylic acid esters. (Meth)acrylic resins may also contain structural units derived from one or more monomers other than (meth)acrylic acid esters (for example, structural units derived from monomers having polar functional groups). Examples of (meth)acrylic acid esters include those represented by the following formula (I). [ka] [In formula (I), R1 represents a hydrogen atom or a methyl group, and R2 represents an alkyl group or aralkyl group having 1 to 14 carbon atoms, preferably an alkyl group, and the hydrogen atoms of the alkyl group or aralkyl group may be replaced by an alkoxy group having 1 to 10 carbon atoms.] In formula (I), R2 is preferably an alkyl group having 1 to 14 carbon atoms.

[0026] As for (meth)acrylic acid esters, Linear alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, n-octyl acrylate, and lauryl acrylate; Branched alkyl acrylates such as isobutyl acrylate, 2-ethylhexyl acrylate, and isooctyl acrylate; Linear alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, n-octyl methacrylate, and lauryl methacrylate; Branched alkyl methacrylates such as isobutyl methacrylate, 2-ethylhexyl methacrylate, and isooctyl methacrylate; Alkoxyalkyl esters of (meth)acrylic acid such as 2-methoxyethyl acrylate, ethoxymethyl acrylate, 2-methoxyethyl methacrylate, and ethoxymethyl methacrylate; and Examples include (meth)acrylic acid aralkyl esters such as benzyl acrylate and benzyl methacrylate.

[0027] The (meth)acrylic resin may contain structural units derived from two or more (meth)acrylic acid esters, and it is preferable that it contains structural units derived from (meth)acrylic acid esters whose homopolymer glass transition temperature (Tg) is 0°C or lower, and structural units derived from (meth)acrylic acid esters whose homopolymer Tg is 0°C or higher. As a (meth)acrylic acid ester with a Tg of 0°C or less, n-butyl acrylate is preferred. As a (meth)acrylic acid ester with a Tg of 0°C or more, methyl acrylate is preferred.

[0028] (Meth)acrylic resins may contain structural units derived from monomers other than those mentioned above. Preferably, structural units derived from monomers having polar functional groups are those derived from monomers having polar functional groups, and more preferably, structural units derived from (meth)acrylic acid esters having polar functional groups. Examples of polar functional groups include hydroxyl groups, substituted or unsubstituted amino groups, and heterocyclic groups such as epoxy groups. Monomers having polar functional groups include: Monomers having hydroxyl groups such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-(2-hydroxyethoxy)ethyl (meth)acrylate, 2-chloro-2-hydroxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, and diethylene glycol mono(meth)acrylate; Monomers having heterocyclic groups such as acryloylmorpholine, vinylcaprolactam, N-vinyl-2-pyrrolidone, vinylpyridine, tetrahydrofurfuryl (meth)acrylate, caprolactone-modified tetrahydrofurfuryl acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, glycidyl (meth)acrylate, and 2,5-dihydrofuran; Examples include monomers having substituted or unsubstituted amino groups, such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and dimethylaminopropyl (meth)acrylate. Among these, monomers having a hydroxyl group are preferred, and (meth)acrylic acid esters having a hydroxyl group are more preferred in terms of reactivity between the (meth)acrylic resin and the crosslinking agent.

[0029] 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 and 10 parts by mass or less, even more preferably 0.5 parts by mass or more and 5 parts by mass or less, and particularly preferably 1 part by mass or more and 5 parts by mass or less, per 100 parts by mass of the total structural units of the (meth)acrylic resin.

[0030] Examples of monomers having polar functional groups include monomers having carboxyl groups as polar functional groups (e.g., acrylic acid, methacrylic acid, etc.). However, the content of structural units derived from monomers having carboxyl groups in (meth)acrylic resins is less than 2 parts by mass per 100 parts by mass of the total structural units of the (meth)acrylic resin, which suppresses corrosion of transparent electrodes under humid heat conditions.

[0031] (Meth)acrylic resins may contain structural units derived from monomers having aromatic groups. Preferably, the monomer having aromatic groups is a monomer having one olefinic double bond and one or more aromatic rings (e.g., a benzene ring, a naphthalene ring, etc.) in the molecule and not having polar functional groups, and more preferably a (meth)acrylic acid ester having a phenoxyethyl group. Examples of (meth)acrylic acid esters having a phenoxyethyl group include 2-phenoxyethyl (meth)acrylate, 2-(2-phenoxyethoxy)ethyl (meth)acrylate, ethylene oxide-modified nonylphenol ester of (meth)acrylic acid, and 2-(o-phenylphenoxy)ethyl (meth)acrylate. Among these, 2-phenoxyethyl (meth)acrylate and 2-(2-phenoxyethoxy)ethyl (meth)acrylate are preferred.

[0032] 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 and 20 parts by mass or less, and even more preferably 4 parts by mass or more and 16 parts by mass or less, per 100 parts by mass of the total structural units of the (meth)acrylic resin.

[0033] In addition to the above, (meth)acrylic resins may also contain structural units derived from (meth)acrylic acid esters having an alicyclic structure, structural units derived from styrene monomers, structural units derived from vinyl monomers, structural units derived from monomers having multiple (meth)acryloyl groups in the molecule, structural units derived from (meth)acrylamide monomers, and the like.

[0034] Examples of alicyclic structures include cycloparaffin structures having 5 or more carbon atoms, preferably 5 to 7. Examples of (meth)acrylic acid esters having an alicyclic structure include isobornyl acrylate, cyclohexyl acrylate, dicyclopentanyl acrylate, cyclododecyl acrylate, methylcyclohexyl acrylate, trimethylcyclohexyl acrylate, tert-butylcyclohexyl acrylate, α-ethoxyacrylate cyclohexyl, cyclohexylphenyl acrylate, isobornyl methacrylate, cyclohexyl methacrylate, dicyclopentanyl methacrylate, cyclododecyl methacrylate, methylcyclohexyl methacrylate, trimethylcyclohexyl methacrylate, tert-butylcyclohexyl methacrylate, and cyclohexylphenyl methacrylate.

[0035] Examples of styrene monomers include styrene; alkylstyrenes such as methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, diethylstyrene, triethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene, and octylstyrene; halogenated styrenes such as fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, and iodostyrene; nitrostyrene; acetylstyrene; methoxystyrene; and divinylbenzene.

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

[0037] Examples of monomers having multiple (meth)acryloyl groups in their molecule include monomers having two (meth)acryloyl groups in their molecule, such as 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, and tripropylene glycol di(meth)acrylate; and monomers having three (meth)acryloyl groups in their molecule, such as trimethylolpropane tri(meth)acrylate.

[0038] Examples of (meth)acrylamide monomers include N-methylol(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, N-isopropyl(meth)acrylamide, N-(3-dimethylaminopropyl)(meth)acrylamide, N-(1,1-dimethyl-3-oxobutyl)(meth)acrylamide, N-[2-(2-oxo-1-imidazolidinyl)ethyl](meth)acrylamide, 2-acryloylamino-2-methyl-1-propanesulfonic acid, N-(methoxymethyl)acrylamide, N-(ethoxymethyl)(meth)acrylamide, N-(propoxymethyl)(meth)acrylamide, N-(1-methylethoxymethyl)(meth)acrylamide, N-(1-methylpropoxymethyl)(meth)acrylamide, N-(2-methylpropoxymethyl)(meth)acrylamide, N-(butoxymethyl)(meth)acrylamide, N-(1,1-dimethylethoxymethyl)(meth)acrylamide, N-(2-methoxyethyl)(meth)acrylamide, N-(2-ethoxyethyl)( Examples include meth)acrylamide, N-(2-propoxyethyl)(meth)acrylamide, N-[2-(1-methylethoxy)ethyl](meth)acrylamide, N-[2-(1-methylpropoxy)ethyl](meth)acrylamide, N-[2-(2-methylpropoxy)ethyl](meth)acrylamide, N-(2-butoxyethyl)(meth)acrylamide, and N-[2-(1,1-dimethylethoxy)ethyl](meth)acrylamide. Among these, N-(methoxymethyl)acrylamide, N-(ethoxymethyl)acrylamide, N-(propoxymethyl)acrylamide, N-(butoxymethyl)acrylamide, and N-(2-methylpropoxymethyl)acrylamide are preferred.

[0039] The (meth)acrylic resin preferably contains, in addition to structural units derived from (meth)acrylic acid esters that do not have polar functional groups, at least one structural unit selected from the group consisting of structural units derived from monomers having hydroxyl groups (preferably (meth)acrylic acid esters that have hydroxyl groups) and structural units derived from monomers having aromatic groups (preferably monomers that have one olefinic double bond and one or more aromatic rings (e.g., a benzene ring, a naphthalene ring, etc.) in the molecule and do not have polar functional groups).

[0040] The weight-average molecular weight (Mw) of the (meth)acrylic resin is preferably 500,000 to 2,500,000. When the weight-average molecular weight is 500,000 or more, the adhesion of the adhesive layer in a high-humidity, high-temperature environment is improved, the possibility of lifting or peeling between the release film or optical component and the adhesive layer tends to decrease, and reworkability also tends to improve. When the weight-average molecular weight is 2,500,000 or less, even if the dimensions of the optical component change, the adhesive layer tends to follow and fluctuate with the dimensional changes, so white spots and color unevenness tend to be suppressed in liquid crystal display devices 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 usually 2 to 10. The weight-average molecular weight can be analyzed by gel permeation chromatography and is a value on a standard polystyrene basis.

[0041] The adhesive composition may contain two or more (meth)acrylic resins, for example, a (meth)acrylic resin whose main component is a structural unit derived from a (meth)acrylic acid ester represented by formula (I) and whose weight-average molecular weight is 500,000 to 2,500,000, and a (meth)acrylic resin whose main component is a structural unit derived from a (meth)acrylic acid ester represented by formula (I) and whose weight-average molecular weight is 50,000 to 300,000.

[0042] The (meth)acrylic resin is preferably such that, when dissolved in ethyl acetate to prepare a polymer solution with a concentration of 20% by mass, the viscosity of the polymer solution at 25°C is 20 Pa·s or less, and more preferably such that the viscosity is 0.1 to 7 Pa·s. The adhesive layer formed from the adhesive composition containing the (meth)acrylic resin with a viscosity of 20 Pa·s or less tends to have improved adhesion in high-humidity and high-temperature environments, a reduced possibility of lifting or peeling between the release film or optical component and the adhesive layer, and improved reworkability. The viscosity can be measured using a Brookfield viscometer.

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

[0044] (Meth)acrylic resins can usually be produced by known polymerization methods such as solution polymerization, bulk polymerization, suspension polymerization, and emulsion polymerization. In the production of (meth)acrylic resins, polymerization is usually carried out in the presence of a polymerization initiator. The amount of polymerization initiator used is usually 0.001 to 5 parts by mass per 100 parts by mass of the total amount of all monomers constituting the (meth)acrylic resin. (Meth)acrylic resins can also be produced by polymerization using active energy rays such as ultraviolet light.

[0045] Examples of polymerization initiators include thermal polymerization initiators and photopolymerization initiators. An example of a photopolymerization initiator is 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone. Examples of thermal polymerization initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonnitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), and dimethyl Examples include azo compounds such as 2,2'-azobis(2-methylpropionate) and 2,2'-azobis(2-hydroxymethylpropionitrile); organic peroxides such as lauryl peroxide, tert-butyl hydroperoxide, benzoyl peroxide, tert-butyl peroxybenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, dipropyl peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-butyl peroxypivalate, and (3,5,5-trimethylhexanoyl) peroxide; and inorganic peroxides such as potassium persulfate, ammonium persulfate, and hydrogen peroxide. In addition, redox initiators using peroxides and reducing agents can also be used as polymerization initiators.

[0046] (Meth)acrylic resins are preferably produced by solution polymerization. Specifically, a 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 a (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 dissolved state in the 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 propyl alcohol and isopropyl alcohol; and ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone.

[0047] <Crosslinking agent> The adhesive composition contains a crosslinking agent. Examples of crosslinking agents include isocyanate compounds, epoxy compounds, aziridine compounds, and metal chelate compounds.

[0048] Isocyanate compounds are compounds having at least two isocyanate groups (-NCO) in their molecule. Specifically, examples include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, naphthalene diisocyanate, and triphenylmethane triisocyanate. Adduct compounds obtained by reacting these isocyanate compounds with polyols such as glycerol and trimethylolprone, as well as dimers and trimers of these isocyanate compounds, are also examples. Two or more isocyanate compounds may be combined.

[0049] Epoxy compounds are compounds having at least two epoxy groups in their molecule. Specifically, examples include bisphenol A type epoxy resins, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, N,N-diglycidylaniline, N,N,N',N'-tetraglycidyl-m-xylenediamine, and 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane. Two or more epoxy compounds may be combined.

[0050] Aziridine compounds are compounds that have at least two ethyleneimine skeletons, that is, three-membered ring skeletons consisting of one nitrogen atom and two carbon atoms, within their molecule. Specifically, examples include diphenylmethane-4,4'-bis(1-aziridinecarboxamide), toluene-2,4-bis(1-aziridinecarboxamide), triethylenemelamine, isophthaloylbis-1-(2-methylaziridine), tris-1-aziridinylphosphine oxide, hexamethylene-1,6-bis(1-aziridinecarboxamide), trimethylolpropane-tris-β-aziridinylpropionate, and tetramethylolmethane-tris-β-aziridinylpropionate.

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

[0052] Among these, isocyanate compounds are preferred, with tolylene diisocyanate, adducts obtained by reacting tolylene diisocyanate with a polyol, dimers of tolylene diisocyanate, trimers of tolylene diisocyanate, xylylene diisocyanate, adducts obtained by reacting xylylene diisocyanate with a polyol, dimers of xylylene diisocyanate, trimers of xylylene diisocyanate, hexamethylene diisocyanate, adducts obtained by reacting hexamethylene diisocyanate with a polyol, dimers of hexamethylene diisocyanate, trimers of hexamethylene diisocyanate, and mixtures thereof being more preferred.

[0053] The crosslinking agent content in the adhesive composition is typically 0.05 to 5 parts by mass per 100 parts by mass of (meth)acrylic resin (total amount if two or more types of (meth)acrylic resins are included). When the amount of crosslinking agent is 0.05 parts by mass or more, the durability of the adhesive layer tends to improve, and when it is 5 parts by mass or less, the white gaps that occur when the laminate of the present invention, as described later, is applied to a liquid crystal display device become less noticeable.

[0054] <Silane compounds> The adhesive composition may further contain a silane compound. Examples of silane compounds include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylethoxydimethylsilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane.

[0055] The silane compound may also be a silicone oligomer. Specific examples of silicone oligomers are shown below. In the following examples, the silicone oligomer is expressed as a combination of monomers. 3-mercaptopropyltrimethoxysilane-tetramethoxysilane oligomer, 3-mercaptopropyltrimethoxysilane-tetraethoxysilane oligomer, 3-mercaptopropyltriethoxysilane-tetramethoxysilane oligomer, 3-mercaptopropyltriethoxysilane-tetraethoxysilane oligomer, 3-mercaptopropyltriethoxysilane-tetraethoxysilane oligomer, and other mercaptopropyl group-containing oligomers;

[0056] Mercaptomethyl group-containing oligomers such as mercaptomethyltrimethoxysilane-tetramethoxysilane oligomer, mercaptomethyltrimethoxysilane-tetraethoxysilane oligomer, mercaptomethyltriethoxysilane-tetramethoxysilane oligomer, and mercaptomethyltriethoxysilane-tetraethoxysilane oligomer;

[0057] 3-methacryloyloxypropyltrimethoxysilane-tetramethoxysilane oligomer, 3-methacryloyloxypropyltrimethoxysilane-tetraethoxysilane oligomer, 3-methacryloyloxypropyltriethoxysilane-tetramethoxysilane oligomer, 3-methacryloyloxypropyltriethoxysilane-tetraethoxysilane oligomer, 3-methacryloyloxypropylmethyldimethoxysilane-tetramethoxysilane oligomer, 3-methacryloyloxypropylmethyldimethoxysilane-tetraethoxysilane oligomer, 3-methacryloyloxypropylmethyldiethoxysilane-tetramethoxysilane oligomer, 3-methacryloyloxypropylmethyldiethoxysilane-tetraethoxysilane oligomer, 3-methacryloyloxypropylmethyldiethoxysilane-tetraethoxysilane oligomer, etc., containing a methacryloyloxypropyl group;

[0058] Acryloyloxypropyl group-containing oligomers such as 3-acryloyloxypropyltrimethoxysilane-tetramethoxysilane oligomer, 3-acryloyloxypropyltrimethoxysilane-tetraethoxysilane oligomer, 3-acryloyloxypropyltriethoxysilane-tetramethoxysilane oligomer, 3-acryloyloxypropyltriethoxysilane-tetraethoxysilane oligomer, 3-acryloyloxypropylmethyldimethoxysilane-tetramethoxysilane oligomer, 3-acryloyloxypropylmethyldimethoxysilane-tetraethoxysilane oligomer, 3-acryloyloxypropylmethyldiethoxysilane-tetramethoxysilane oligomer, and 3-acryloyloxypropylmethyldiethoxysilane-tetraethoxysilane oligomer;

[0059] Vinyl group-containing oligomers such as vinyltrimethoxysilane-tetramethoxysilane oligomer, vinyltrimethoxysilane-tetraethoxysilane oligomer, vinyltriethoxysilane-tetramethoxysilane oligomer, vinyltriethoxysilane-tetraethoxysilane oligomer, vinylmethyldimethoxysilane-tetramethoxysilane oligomer, vinylmethyldimethoxysilane-tetraethoxysilane oligomer, vinylmethyldiethoxysilane-tetramethoxysilane oligomer, and vinylmethyldiethoxysilane-tetraethoxysilane oligomer.

[0060] The silane compound content in the adhesive composition is usually 0.01 to 10 parts by mass, preferably 0.05 to 5 parts by mass, per 100 parts by mass of (meth)acrylic resin (total amount if two or more types of (meth)acrylic resins are included). When the silane compound content is 0.01 parts by mass or more per 100 parts by mass of (meth)acrylic resin, the adhesion between the adhesive layer and the optical component tends to improve, and when the content is 10 parts by mass or less, the silane compound tends to bleed out from the adhesive layer.

[0061] <Antistatic agent> The adhesive composition may further contain an antistatic agent. Known antistatic agents are examples, with ionic antistatic agents being preferred. Examples of cationic components constituting the ionic antistatic agent include organic cations and inorganic cations. Examples of organic cations include pyridinium cations, imidazolium cations, ammonium cations, sulfonium cations, and phosphonium cations. Examples of inorganic cations include alkali metal cations such as lithium cations, potassium cations, sodium cations, and cesium cations, and alkaline earth metal cations such as magnesium cations and calcium cations. The anionic component constituting the ionic antistatic agent may be either an inorganic anion or an organic anion, but an anionic component containing a fluorine atom is preferred due to its superior antistatic performance. An anionic component containing a fluorine atom is the hexafluorophosphate anion (PF6).- ), bis(trifluoromethanesulfonyl)imide anion [(CF3SO2)2N - ], bis(fluorosulfonyl)imide anion [(FSO2)2N - Examples include anions. Ionic antistatic agents that are solid at room temperature are preferred because they offer excellent long-term stability of the antistatic performance of the adhesive composition.

[0062] <Method for manufacturing a substrate-free double-sided adhesive sheet> The present invention relates to a method for manufacturing a substrate-less double-sided adhesive sheet, characterized by comprising the following steps (A) to (C). Process (A): Coating process in which an adhesive composition is applied to a light-release film to form a coating layer. Step (B): Drying step to dry the coating layer and obtain an adhesive layer. Step (C): Lamination step of laminating a heavy release film onto the adhesive layer.

[0063] <Coating Process> The coating process involves applying an adhesive composition to a lightly release film to obtain a coated layer. The method for applying the adhesive composition is not particularly limited, and methods such as slot die coating, reverse gravure coating, microgravure coating, dip coating, spin coating, brush coating, roll coating, and flexographic printing can be used. The adhesive composition is applied to the release layer surface of the release film. Alternatively, before applying the adhesive composition, at least one of the release layer surface and the adhesive layer of the release film may be subjected to surface treatments such as corona treatment, plasma treatment, ultraviolet irradiation, flame treatment, saponification, or primer layer formation. The viscosity of the adhesive composition is usually 20,000 cPs or less, preferably 15,000 cPs or less, and 1 cPs or more. The solid content concentration in the adhesive composition is usually 1 to 20% by mass, preferably 2 to 15% by mass.

[0064] The thickness of the adhesive layer in the present invention may be less than 20 μm. Preferably, the thickness of the adhesive layer is 2 to 18 μm, more preferably 3 to 15 μm, and particularly preferably 3 to 10 μm. When the thickness of the adhesive layer is thin, separation of the adhesive layer tends to occur when peeling off the light release film, but according to the present invention, separation can be suppressed even when the adhesive layer is thin.

[0065] <Drying process> The drying process is a process of drying the coating layer of the adhesive composition obtained in the coating process described above. The drying method for the coating layer is not particularly limited, and methods such as heat drying in a hot air drying oven are possible. Reduced pressure may also be applied during drying. The drying temperature is usually 30-200°C, preferably 50-160°C, and the drying time can be 5 seconds to 10 minutes.

[0066] <Lamination process> The lamination process involves laminating a heavy release film onto the adhesive layer obtained in the drying process described above. The heavy release film and the adhesive layer are laminated so that the release treatment layer of the heavy release film and the adhesive layer are in contact. In addition, before laminating the heavy release film and the adhesive layer, surface treatments such as corona treatment, plasma treatment, ultraviolet irradiation treatment, flame treatment, saponification treatment, and primer layer formation treatment may be applied to at least one of the release treatment layer surface of the heavy release film and the adhesive layer.

[0067] The substrate-free double-sided adhesive sheet obtained by process (C) may be subjected to curing treatment. For example, the performance of the adhesive can be stabilized by storing it for 12 hours to 14 days in an environment with a temperature of 5 to 40 degrees Celsius and a relative humidity of 10 to 85%.

[0068] By using the above manufacturing method, the water contact angle on the surface of the adhesive layer on the light release film side can be made smaller than the water contact angle on the surface of the adhesive layer on the heavy release film side. When an adhesive composition is applied to a heavy release film as in the conventional method, the difference between the water contact angle on the surface of the adhesive layer on the heavy release film side and the water contact angle on the surface of the adhesive layer on the light release film side becomes almost zero. This is presumed to be because the heavy release additive contained in the release treatment layer of the heavy release film migrates and diffuses into the adhesive layer, reaching the surface of the light release film side, and the heavy release additive affects the water contact angle on the surface of the adhesive layer on the light release film side. Furthermore, if the heavy release additive reaches the surface of the adhesive layer on the light release film side, the light release film in contact with the adhesive layer surface is also affected by the heavy release additive, and it is presumed that the difference between the peeling force of the light release film and the peeling force of the heavy release film becomes smaller, making separation more likely.

[0069] On the other hand, in the manufacturing method of the present invention, since the adhesive composition is coated onto the light release film, the migration of the heavy release additive to the adhesive layer is suppressed, and it is presumed that the change in the water contact angle on the surface of the adhesive layer on the light release film side can be suppressed, and the difference between the peeling force of the light release film and the peeling force of the heavy release film can be maintained. Therefore, when using the substrate-less double-sided adhesive sheet of the present invention, even if the difference in peeling force between the peeling force of the light release film laminated on both sides and the peeling force of the heavy release film is less than 98 mN / 25 mm, the occurrence of separation can be suppressed. In the present invention, the difference in peeling force between the peeling force of the light release film and the peeling force of the heavy release film is preferably 1 mN / 25 mm to 80 mN / 25 mm. The peeling force can be measured using a precision universal tester.

[0070] In the substrate-less double-sided adhesive sheet of the present invention, it is preferable that the difference between the water contact angle on the surface of the adhesive layer on the light release film side and the water contact angle on the surface of the adhesive layer on the heavy release film side is 3 degrees or more. Furthermore, in the substrate-less double-sided adhesive sheet of the present invention, the difference between the water contact angle on the surface of the adhesive layer on the light release film side and the water contact angle on the surface of the adhesive layer on the heavy release film side may be 50 degrees or less, or 30 degrees or less. If the difference between the water contact angle on the surface of the adhesive layer on the light release film side and the water contact angle on the surface of the adhesive layer on the heavy release film side is less than 3 degrees, it can be inferred that the suppression of the migration of the heavy release additive to the adhesive layer is insufficient, and the difference between the peeling force of the light release film and the peeling force of the heavy release film becomes small. The water contact angle of the adhesive layer surface can be measured by the method described in the examples. Furthermore, in the adhesive layer of the present invention, it is preferable that the difference between the water contact angle of one surface and the water contact angle of the other surface is 3 degrees or more. The adhesive layer of the present invention may have a difference of 50 degrees or less between the water contact angle of one surface and the water contact angle of the other surface, or it may have a difference of 30 degrees or less.

[0071] <Laminate> The substrate-less double-sided adhesive sheet of the present invention is useful for bonding optical components together because it can suppress the occurrence of separation when peeling off a light release film. The present invention also includes a laminate of an adhesive layer obtained from the substrate-less double-sided adhesive sheet of the present invention and an optical member. The laminate of the present invention can be manufactured by peeling off a light release film from the substrate-less double-sided adhesive sheet of the present invention and bonding the exposed adhesive layer to the optical member. Therefore, the laminate of the present invention is a laminate comprising an optical member, an adhesive layer, and a heavy release film in this order, characterized in that the water contact angle on the surface of the adhesive layer on the optical member side is smaller than the water contact angle on the surface of the adhesive layer on the heavy release film side. In the laminate of the present invention, it is preferable that the water contact angle on the surface of the adhesive layer on the optical member side and the water contact angle on the surface of the adhesive layer on the heavy release film side are 3 degrees or more, but may be 50 degrees or less, or 30 degrees or less. The heavy release film in the laminate of the present invention is preferably a film in which a release treatment layer containing the above-mentioned heavy release additive is formed on a plastic film.

[0072] The present invention relates to a laminate comprising an optical member, an adhesive layer, and a double-release film in this order, The process for manufacturing a substrate-less double-sided adhesive sheet using the manufacturing method described above, A bonding step is performed in which a light release film is peeled off from the obtained substrate-less double-sided adhesive sheet, and the exposed adhesive layer is bonded to the optical component. This also includes a method for manufacturing a laminate containing the above.

[0073] The optical component is not particularly limited as long as it is one of various optical films (films having optical properties) that can be incorporated into an image display device such as a liquid crystal display device. The optical film may have a single-layer structure or a multi-layer structure. Examples of optical films include polarizers, polarizing plates, phase difference films, brightness-enhancing films, anti-glare films, anti-reflective films, diffusion films, and light-gathering films, with polarizers, polarizing plates, or phase difference films being preferred. The thickness of the optical component may be less than 150 μm. Preferably, the thickness of the optical component is 5 to 120 μm or less, and more preferably 10 to 100 μm.

[0074] <Polarizer> A polarizer is a layer or film that selectively transmits linearly polarized light in one direction from natural light. Examples of polarizers include films in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film. Examples of dichroic dyes include iodine and dichroic organic dyes. Alternatively, a polarizer may be a coated polarizing film in which a dichroic dye in a lyotropic liquid crystal state is coated onto a base film, oriented, and fixed. These polarizers are called absorbing polarizers because they selectively transmit linearly polarized light in one direction from natural light and absorb linearly polarized light in the other direction.

[0075] The polarizer is not limited to an absorpting polarizer; it may also be a reflective polarizer that selectively transmits linearly polarized light in one direction from natural light and reflects linearly polarized light in the other direction, or a scattering polarizer that scatters linearly polarized light in the other direction. However, absorpting polarizers are preferred because they offer superior visibility. Among these, polyvinyl alcohol-based polarizing films composed of polyvinyl alcohol-based resin films are more preferred, polyvinyl alcohol-based polarizing films in which dichroic dyes such as iodine or dichroic dyes are adsorbed and oriented on a polyvinyl alcohol-based resin film are even more preferred, and polyvinyl alcohol-based polarizing films in which iodine is adsorbed and oriented on a polyvinyl alcohol-based resin film are particularly preferred.

[0076] As the polyvinyl alcohol-based resin, a saponified polyvinyl acetate-based resin can be used. Examples of polyvinyl acetate-based resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as copolymers of vinyl acetate with other monomers copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides having an ammonium group.

[0077] The degree of saponification of the polyvinyl alcohol resin is usually between 85 mol% and 100 mol%, with 98 mol% or higher being preferred. The polyvinyl alcohol resin may be modified; for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can be used. The average degree of polymerization of the polyvinyl alcohol resin is usually between 1000 and 10000, with 1500 and 5000 being preferred. The average degree of polymerization of the polyvinyl alcohol resin can be determined in accordance with JIS K 6726:1994.

[0078] A film made from such a polyvinyl alcohol-based resin is used as the base film for a polarizing film composed of polyvinyl alcohol-based resin films. The method for producing the polyvinyl alcohol-based resin film is not particularly limited, and known methods can be used. The thickness of the polyvinyl alcohol-based base film is, for example, 150 μm or less, preferably 100 μm or less (for example, 50 μm or less), and 5 μm or more.

[0079] Polarizing films composed of polyvinyl alcohol-based resin films can be manufactured by known methods. Specifically, they can be manufactured by a method including the steps of: uniaxial stretching of a polyvinyl alcohol-based resin film; adsorption of a dichroic dye by dyeing the polyvinyl alcohol-based resin film with a dichroic dye; treatment (crosslinking) of the polyvinyl alcohol-based resin film on which the dichroic dye has been adsorbed with an aqueous boric acid solution; and washing with water after treatment with the aqueous boric acid solution.

[0080] The thickness of the polarizer can be 40 μm or less, preferably 30 μm or less (for example, 20 μm or less, more preferably 15 μm or less, even more preferably 10 μm or less or 8 μm or less). According to the methods described in Japanese Patent Publication No. 2000-338329 and Japanese Patent Publication No. 2012-159778, thin-film polarizers can be manufactured more easily, and it becomes easier to make the thickness of the polarizer 20 μm or less, more preferably 15 μm or less, even more preferably 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 advantageous for thinning laminates containing polarizers or polarizing plates, and image display devices containing them.

[0081] <Polarizing plate> A polarizing plate has a protective film laminated on one or both sides of the polarizer. Examples of protective films laminated on one or both sides of the polarizer include transparent resin films. Examples of transparent resins include cellulose resins, acrylic resins, polyester resins, polyolefin resins, polycarbonate resins, polyetheretherketone resins, and polysulfone resins.

[0082] Examples of cellulose-based resins include cellulose acetate esters, propionic acid esters, butyric acid esters, and mixed esters thereof. Among these, triacetylcellulose, diacetylcellulose, cellulose acetate propionate, and cellulose acetate butyrate are preferred. Examples of commercially available cellulose-based resin films include "Fujitac TD" (product name, sold by Fujifilm Corporation) and "Konica Minolta TAC Film KC" (product name, sold by Konica Minolta Opto, Inc.).

[0083] Acrylic resin films are films formed from acrylic resin obtained by mixing and melt-kneading a methacrylic resin and additives as needed. A methacrylic resin is a polymer mainly composed of methacrylic acid esters. A methacrylic resin may be a homopolymer of one type of methacrylic acid ester, a copolymer of two or more types of methacrylic acid esters, or a copolymer of a methacrylic acid ester and an acrylic acid ester. Examples of methacrylic acid esters include alkyl esters of methacrylic acid having 1 to 4 carbon atoms, such as methyl methacrylate, ethyl methacrylate, and butyl methacrylate. As acrylic acid esters that can copolymerize with methacrylic acid esters, alkyl esters of acrylic acid having 1 to 8 carbon atoms are preferred, specifically including methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate. Furthermore, it may be a copolymer with a compound having at least one polymerizable carbon-carbon double bond in the molecule (for example, aromatic vinyl compounds such as styrene or vinyl cyanide compounds such as acrylonitrile).

[0084] The protective film may have one or more surface treatment layers on the side opposite to the surface in contact with the polarizer, if necessary. Examples of surface treatment layers include a hard coat layer, an anti-glare layer, an anti-reflective layer, and an anti-static layer.

[0085] The protective film is bonded to the polarizer via an adhesive layer or a known adhesive layer. A known adhesive composition or known adhesive composition may be used to bond the polarizer and the protective film. If the polarizer is a single-sided protective film in which the protective film is laminated on only one side of the polarizer, the polarizer is bonded to the adhesive layer obtained from the substrate-less double-sided adhesive sheet of the present invention. If the polarizer is a double-sided protective film in which the protective film is laminated on both sides of the polarizer, the protective film is bonded to the adhesive layer obtained from the substrate-less double-sided adhesive sheet of the present invention, and the protective film in contact with the adhesive layer is preferably a triacetylcellulose film, an acrylic resin film, a polyolefin resin film, or a polycarbonate resin film.

[0086] <Phase difference film> A phase difference film is an optical film exhibiting optical anisotropy, and examples include stretched films obtained by stretching a resin film made of polyvinyl alcohol resin, polycarbonate resin, polyester resin, polyarylate resin, polyimide resin, olefin resin, cycloolefin resin, styrene resin, sulfone resins such as polysulfone and polyethersulfone, polyvinylidene fluoride / polymethyl methacrylate, liquid crystal polyester resin, cellulose resin containing triacetylcellulose, ethylene-vinyl acetate copolymer saponified, polyvinyl chloride resin, acrylic resin, etc., to about 1.01 to 6 times its original size. Among these, resin films obtained by uniaxially or biaxially stretching cycloolefin resin films, cellulose resin films, polyester resin films, and polycarbonate films are preferred. In this specification, a phase difference film includes zero retardation films and also includes films referred to as uniaxial phase difference films, low photomodulus phase difference films, wide viewing angle phase difference films, etc. Furthermore, a phase difference film may have a single-layer structure or a multi-layer structure.

[0087] Examples of cycloolefin resins include thermoplastic resins having monomer units of cycloolefins such as norbornene, tetracyclododecene, or derivatives thereof. These may be ring-opened polymers of cycloolefins or hydrogenated ring-opened copolymers of two or more cycloolefins, or addition copolymers of cycloolefins with chain-like olefins or aromatic compounds having vinyl groups, or polar groups may be introduced.

[0088] Examples of commercially available thermoplastic cycloolefin resins include "TOPAS," produced by TOPAS ADVANCED POLYMERS GmbH in Germany and sold in Japan by Polyplastics Co., Ltd.; "ARTON®," sold by JSR Corporation; "ZEONEX®" and "ZEONOR®," sold by Zeon Corporation; and "APPEL®," sold by Mitsui Chemicals, Inc.

[0089] Methods for producing films from cycloolefin resins include known film-forming techniques such as solvent casting and melt extrusion. Cycloolefin resin films, as well as cycloolefin resin films that have been further stretched to impart a phase difference, are commercially available. Specifically, these include "ARTON® film" sold by JSR Corporation, "ZEONOR® film" sold by Nippon Zeon Co., Ltd., and "SCina®" and "SCA40" (product names) sold by Sekisui Chemical Co., Ltd.

[0090] Cellulose resin films are films made of partial or complete esterified cellulose. Examples include films made of cellulose acetate ester, propionic acid ester, butyrate ester, and mixed esters thereof. Among these, triacetylcellulose films, diacetylcellulose films, cellulose acetate propionate films, and cellulose acetate butyrate films are preferred. Examples of commercially available cellulose resin films include "Fujitac TD" sold by Fujifilm Corporation and "Konica Minolta TAC Film KC" sold by Konica Minolta Opto, Inc.

[0091] Polyester resins are polymers obtained by condensation polymerization of a dibasic acid and a dihydric alcohol, and examples include polyethylene terephthalate. Polycarbonate resins are polymers having carbonate bonds (-O-CO-O-) in their main chain, and examples include those obtained by condensation polymerization of bisphenol A and phosgene.

[0092] Zero retardation film refers to front retardation R e and retardation R in the thickness direction th Zero retardation films are optically isotropic films with wavelengths of -15 to 15 nm. Examples of zero retardation films include resin films made of cellulose resin, polyolefin resin (such as chain polyolefin resin or polycycloolefin resin), or polyethylene terephthalate resin. Cellulose resin or polyolefin resin is preferred because the retardation value is easy to control and readily available. Zero retardation films can also be used as protective films. Examples of zero retardation films include "Z-TAC" (product name) sold by Fujifilm Corporation, "ZeroTac®" (registered trademark) sold by Konica Minolta Opto Inc., and "ZF-14" (product name) sold by Nippon Zeon Co., Ltd.

[0093] Methods for producing films from cellulose-based resins or polyolefin-based resins include the solvent casting method, in which the resin dissolved in a solvent is cast onto a metal band or drum, and the solvent is dried off to obtain the film; and the melt extrusion method, in which the resin is heated above its melting point, kneaded, extruded from a die, and cooled in a cooling drum to obtain the film. Among these, the melt extrusion method is preferred for polyolefin-based resins from the viewpoint of productivity, while the solvent casting method is preferred for cellulose-based resins.

[0094] Examples of phase difference films include films that exhibit optical anisotropy through the coating and orientation of liquid crystalline compounds, and films that exhibit optical anisotropy through the coating of inorganic layered compounds. Examples of such films include films called temperature-compensated phase difference films, "NH Film" (product name; film with obliquely aligned rod-shaped liquid crystals) sold by JX Nippon Oil & Energy Corporation, "WV Film" (product name; film with obliquely aligned disc-shaped liquid crystals) sold by Fujifilm Corporation, "VAC Film" (product name; fully biaxially oriented film) sold by Sumitomo Chemical Co., Ltd., and "new VAC Film" (product name; biaxially oriented film) sold by Sumitomo Chemical Co., Ltd.

[0095] The laminate of the present invention is a laminate in which an adhesive layer obtained from the substrate-less double-sided adhesive sheet of the present invention and an optical member are laminated together, and the occurrence of separation in the adhesive layer can be suppressed.Therefore, when the laminate of the present invention is bonded to another optical member, good adhesion can be achieved, and the deterioration of the optical properties of the optical member can also be suppressed, and the laminate of the present invention can be suitably used in image display devices such as organic EL displays and liquid crystal displays. [Examples]

[0096] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. Unless otherwise specified, "%" and "parts" in the examples and comparative examples refer to mass percent and parts by mass.

[0097] (1) Preparation of release film (1-1) Preparation of composition a for forming a release layer To 100 parts of a toluene solution of silicone resin (manufactured by Dow-Toray Industries, Ltd., trade name: "LTC759" (solids content concentration 30%)) as the main release agent, 1 part of a 1,3-diethenyl-1,1,3,3-tetramethyldisiloxane platinum complex (obtained from Dow-Toray Industries, Ltd., trade name: "SRX212") was mixed as a catalyst. The resulting mixture was then mixed with a mixed solvent of toluene and methyl ethyl ketone (mass ratio 1:1) to prepare a solids content concentration of 1.5%, thereby obtaining release layer forming composition a.

[0098] (1-2) Preparation of composition b for forming a release layer Composition b was obtained in the same manner as composition a for forming a mold release layer, except that 10 parts of a xylene and ethylbenzene solution of vinyl-modified silicone resin (manufactured by Dow-Toray Industries, Ltd., product name: "SD7292" (solid content concentration 65%, containing 3% by mass of vinyl groups in the solid content) was added as a heavy release additive to 100 parts of a toluene solution of silicone resin (manufactured by Dow-Toray Industries, Ltd., product name: "SD7292" (solid content concentration 65%, containing 3% by mass of vinyl groups in the solid content)).

[0099] (1-3) Preparation of composition c for forming a release layer One part of the catalyst "SRX212" was mixed with 100 parts of the release agent main agent "LTC759". Methyl ethyl ketone was added to the resulting mixture to adjust the solid content concentration to 1.13%, thereby obtaining composition c for forming the release layer.

[0100] (1-4) Preparation of composition d for forming a release layer 100 parts of the release agent "LTC759" were mixed with 1 part of the catalyst "SRX212" and 1 part of the heavy release additive "SD7292". Methyl ethyl ketone was added to the resulting mixture to adjust the solid content to 1.13%, thereby obtaining release layer forming composition d.

[0101] (1-5) Preparation of composition e for forming a release layer 100 parts of the release agent "SRX211" (manufactured by Dow Toray Industries, Ltd., solid content concentration 30%) were mixed with 1 part of the catalyst "SRX212". A mixed solvent of toluene and methyl ethyl ketone (mass ratio 1:1) was added to the resulting mixture to adjust the solid content concentration to 1.13%, thereby obtaining release layer forming composition e.

[0102] (1-6) Preparation of composition f for forming a release layer 100 parts of the release agent "SRX211" were mixed with 1 part of the catalyst "SRX212" and 1 part of the heavy release additive "SD7292". A mixed solvent of toluene and methyl ethyl ketone (mass ratio 1:1) was added to the resulting mixture to prepare a solid content concentration of 1.13%, thereby obtaining the release layer forming composition f.

[0103] (1-7) Preparation of composition g for forming a release layer 100 parts of the release agent "SRX211" were mixed with 1 part of the catalyst "SRX212" and 5 parts of the heavy release additive "SD7292". A mixed solvent of toluene and methyl ethyl ketone (mass ratio 1:1) was added to the resulting mixture to adjust the solid content concentration to 1.13%, thereby obtaining the release layer forming composition g.

[0104] (1-8) Preparation of release film 1 A transparent polyethylene terephthalate (PET) film with a thickness of 38 μm ("Tetron" G2 film, manufactured by Teijin DuPont Limited) was prepared. Next, the release layer forming composition a obtained in (1-1) was applied to one side of the PET film using a film applicator so that the thickness after drying was 190 nm, and the film was dried at 120°C for 1 minute to form a release layer on the PET film. The obtained film was stored in an environment of 23°C and 55% relative humidity for 5 days or more to obtain a release film 1 (light release film) on which a release layer without heavy release additives was formed on the PET film.

[0105] (1-9) Preparation of release film 2 A release film 2 (heavy-release film) was obtained in which a release layer containing a heavy-release additive was formed on a PET film by the same method as for release film 1, except that release layer forming composition b obtained in (1-2) was used instead of release layer forming composition a.

[0106] (1-10) Preparation of release film 3 A transparent polyethylene terephthalate (PET) film with a thickness of 38 μm (manufactured by Mitsubishi Chemical Corporation, product name: Diafoil T190E38) was prepared. Next, release treatment layer forming composition c was applied to one side of the PET film using a bar coater so that the thickness after drying was 100 nm, and the film was dried at 100°C for 3 minutes to form a release treatment layer on the PET film. The obtained film was stored for more than 5 days in an environment of 23°C and 60% relative humidity to obtain release film 3 (light release film).

[0107] (1-11) Preparation of release film 4 A release film 4 (heavy release film) was obtained by the same method as for release film 3, except that release layer forming composition d was used instead of release layer forming composition c.

[0108] (1-12) Preparation of release film 5 A release film 5 (lightly release film) was obtained by the same method as for release film 3, except that release layer forming composition e was used instead of release layer forming composition c.

[0109] (1-13) Preparation of release film 6 A release film 6 (heavy release film) was obtained by the same method as for release film 3, except that release layer forming composition f was used instead of release layer forming composition c.

[0110] (1-14) Preparation of release film 7 A release film 7 (heavy release film) was obtained by the same method as for release film 3, except that release layer forming composition g was used instead of release layer forming composition c.

[0111] (1-15) Preparation of release film 8 Release film 8 (lightly release film) was obtained using the same method as release film 3, except that the drying temperature was changed from 100°C to 80°C.

[0112] (1-16) Preparation of release film 9 Release film 9 (double release film) was obtained using the same method as release film 4, except that the drying temperature was changed from 100°C to 80°C.

[0113] (2) Preparation of adhesive composition (2-1) Preparation of acrylic resin solution 1 A reaction vessel equipped with a condenser, nitrogen inlet tube, thermometer, and stirrer was charged with 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. The internal temperature was raised to 55°C while replacing the air in the apparatus with nitrogen gas to eliminate oxygen. Subsequently, the entirety of a solution of 0.14 parts azobisisobutyronitrile dissolved in 9.86 parts ethyl acetate was added as a polymerization initiator. The temperature was maintained at this level for 1 hour after the addition of the initiator. Then, while maintaining the internal temperature at 54-56°C, ethyl acetate was continuously added to the reaction vessel at an addition rate of 17.3 parts / hr until the acrylic resin concentration reached 35%, at which point the addition of ethyl acetate was stopped. The temperature was then maintained at this level for 12 hours from the start of ethyl acetate addition. Finally, ethyl acetate was added to adjust the acrylic resin concentration to 20%, and acrylic resin solution 1 was prepared. The obtained acrylic resin had a weight-average molecular weight (Mw) of 1.3 million and a molecular weight distribution (Mw / Mn) of 4.2. Mw and Mn were measured using "TSKgel GMH" manufactured by Tosoh Corporation as the column in the GPC instrument. HR Two "-H(S)" units were connected in series, tetrahydrofuran was used as the eluate, and measurements were taken using standard polystyrene equivalents 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 To 100 parts of the solid content of the acrylic resin solution 1 obtained in (2-1), 0.5 parts on an active ingredient basis of a crosslinking agent (manufactured by Tosoh Corporation: trade name "Coronate L" (ethyl acetate solution of trimethylolpropane adduct of tolylene diisocyanate (solid content concentration 75% by mass)) was added, and then ethyl acetate was added to bring the solid content concentration to 7% to obtain adhesive composition 1.

[0115] (2-3) Preparation of adhesive composition 2 To 100 parts of the solid content of the acrylic resin solution 1 obtained in (2-1), 0.5 parts on an active ingredient basis of a crosslinking agent (Mitsui Chemicals: trade name "D-103" (ethyl acetate solution of trimethylolpropane adduct of tolylene diisocyanate (solid content concentration 75% by mass)) was added, and then ethyl acetate was added to bring the solid content concentration to 7% to obtain adhesive composition 2.

[0116] (2-4) Preparation of adhesive composition 3 To 100 parts of the solid content of the acrylic resin solution 1 obtained in (2-1), 0.5 parts of the crosslinking agent "D-103" on an active ingredient basis was added, and 0.01 parts of the silane compound (manufactured by Shin-Etsu Chemical Co., Ltd.: trade name "KBM-403" (3-glycidoxypropyltrimethoxysilane)) on an active ingredient basis was added, and then ethyl acetate was added to bring the solid content concentration to 7% to obtain adhesive composition 3.

[0117] (2-5) Preparation of adhesive composition 4 To 100 parts of the solid content of the acrylic resin solution 1 obtained in (2-1), 0.5 parts of the crosslinking agent "D-103" on an active ingredient basis was added, 0.01 parts of a silane compound (manufactured by Shin-Etsu Chemical Co., Ltd.: trade name "KR-519" (mercapto group-containing silicone oligomer)) on an active ingredient basis was added, and then ethyl acetate was added to bring the solid content concentration to 7% to obtain adhesive composition 4.

[0118] (3) Preparation of substrate-less double-sided adhesive sheets [Example 1] The adhesive composition 1 prepared in (2-2) above was applied to the release layer of the release film 1 using an applicator, and then dried at 100°C for 1 minute to obtain an adhesive layer with a thickness of 5 μm. The release film 2 was laminated to the exposed adhesive side of the obtained adhesive layer opposite to the release film 1, with the release layer side of the release film 2 facing outwards. The resulting laminate was left to stand for 7 days or more in an environment of 23°C and 55% relative humidity to produce a substrate-less double-sided adhesive sheet 1.

[0119] [Example 2] The adhesive composition 2 prepared in (2-3) above was applied to the release layer of the release film 3 using an applicator, and then dried at 100°C for 1 minute to obtain an adhesive layer with a thickness of 5 μm. The release film 4 was laminated to the exposed adhesive side of the obtained adhesive layer opposite to the release film 3, with the release layer side facing outwards. The resulting laminate was left to stand for 7 days or more in an environment of 23°C and 60% relative humidity to produce a substrate-less double-sided adhesive sheet 2.

[0120] [Example 3] The adhesive composition 2 prepared in (2-3) above was applied to the release treatment layer of the release film 5 using an applicator, and then dried at 100°C for 1 minute to obtain an adhesive layer with a thickness of 5 μm. The release film 6 was laminated to the exposed adhesive side of the obtained adhesive layer opposite to the release film 5, with the release treatment layer side facing outwards. The resulting laminate was left to stand for 7 days or more in an environment of 23°C and 60% relative humidity to produce a substrate-less double-sided adhesive sheet 3.

[0121] [Example 4] The adhesive composition 3 prepared in (2-4) above was applied to the release layer of the release film 3 using an applicator, and then dried at 100°C for 1 minute to obtain an adhesive layer with a thickness of 5 μm. The release film 4 was laminated to the exposed adhesive side of the obtained adhesive layer opposite to the release film 3, with the release layer side facing outwards. The resulting laminate was left to stand for 7 days or more in an environment of 23°C and 60% relative humidity to produce a substrate-less double-sided adhesive sheet 4.

[0122] [Example 5] The adhesive composition 3 prepared in (2-4) above was applied to the release treatment layer of the release film 5 using an applicator, and then dried at 100°C for 1 minute to obtain an adhesive layer with a thickness of 5 μm. The release film 6 was laminated to the exposed adhesive side of the obtained adhesive layer opposite to the release film 5, with the release treatment layer side facing outwards. The resulting laminate was left to stand for 7 days or more in an environment of 23°C and 60% relative humidity to produce a substrate-less double-sided adhesive sheet 5.

[0123] [Example 6] The adhesive composition 4 prepared in (2-5) above was applied to the release treatment layer of the release film 5 using an applicator, and then dried at 100°C for 1 minute to obtain an adhesive layer with a thickness of 5 μm. The release film 7 was laminated to the exposed adhesive side of the obtained adhesive layer opposite to the release film 5, with the release treatment layer side facing outwards. The resulting laminate was left to stand for 7 days or more in an environment of 23°C and 60% relative humidity to produce a substrate-less double-sided adhesive sheet 6.

[0124] [Example 7] The adhesive composition 3 prepared in (2-4) above was applied to the release layer of the release film 8 using an applicator, and then dried at 100°C for 1 minute to obtain an adhesive layer with a thickness of 5 μm. The release film 9 was laminated to the exposed adhesive side of the obtained adhesive layer opposite to the release film 8, with the release layer side facing outwards. The resulting laminate was left to stand for 7 days or more in an environment of 23°C and 60% relative humidity to produce a substrate-less double-sided adhesive sheet 7.

[0125] [Comparative Example 1] The adhesive composition 1 prepared in (2-2) above was applied to the release treatment surface of the release film 2 using an applicator, and then dried at 100°C for 1 minute to obtain an adhesive layer with a thickness of 5 μm. The release film 1 was laminated to the exposed adhesive surface of the obtained adhesive layer on the side opposite to the release film 2, with the release treatment layer side of the release film 1 facing outwards. The resulting laminate was left to stand for 7 days or more in an environment of 23°C and 55% relative humidity to produce a substrate-less double-sided adhesive sheet 8.

[0126] [Comparative Example 2] The adhesive composition 3 prepared in (2-4) above was applied to the release layer of the release film 4 using an applicator, and then dried at 100°C for 1 minute to obtain an adhesive layer with a thickness of 5 μm. The release film 3 was laminated to the exposed adhesive side of the obtained adhesive layer opposite to the release film 4, with the release layer side of the release film 3 facing outwards. The resulting laminate was left to stand for 7 days or more in an environment of 23°C and 60% relative humidity to produce a substrate-less double-sided adhesive sheet 9.

[0127] [Comparative Example 3] The adhesive composition 3 prepared in (2-4) above was applied to the release layer of the release film 6 using an applicator, and then dried at 100°C for 1 minute to obtain an adhesive layer with a thickness of 5 μm. The release film 5 was laminated to the exposed adhesive side of the obtained adhesive layer opposite to the release film 6, with the release layer side facing outwards. The resulting laminate was left to stand for 7 days or more in an environment of 23°C and 60% relative humidity to produce a substrate-less double-sided adhesive sheet 10.

[0128] (Method for measuring the water contact angle of the adhesive layer surface) After peeling off the release film 1 (light release film) from the substrate-less double-sided adhesive sheet 1 prepared in Example 1, deionized water was dropped onto the exposed adhesive layer surface using a water contact angle meter (FACE CA-X type (manufactured by Kyowa Interface Chemical Co., Ltd.)) at a temperature of 23°C and a relative humidity of 55%, and the water contact angle was measured immediately afterward. Subsequently, a 38 μm PET film was laminated to the exposed adhesive layer surface, and the release film 2 (heavy release film) on the opposite side was peeled off. At a temperature of 23°C and a relative humidity of 55%, deionized water was dropped onto the exposed adhesive surface using a water contact angle meter (FACE CA-X type (manufactured by Kyowa Interface Chemical Co., Ltd.)), and the water contact angle was measured immediately afterward.

[0129] The water contact angle of the adhesive layer surface was also measured for the substrate-less double-sided adhesive sheets 2-7 prepared in Examples 2-7. As in Example 1, the water contact angle of the surface of the adhesive layer exposed by peeling off the light release film was measured, and then the water contact angle of the surface of the adhesive layer exposed by peeling off the heavy release film was measured.

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

[0131] The water contact angle of the adhesive layer surface was also measured for the substrate-less double-sided adhesive sheets 9 and 10 prepared in Comparative Examples 2 and 3. As with Comparative Example 1, the water contact angle of the surface of the adhesive layer exposed by peeling off the heavy release film was measured, and then the water contact angle of the surface of the adhesive layer exposed by peeling off the light release film was measured.

[0132] The water contact angle was calculated using the θ / 2 method. Five measurements were taken, and the average value was used as the measured value. The results are shown in [Table 1].

[0133] (Method for measuring peel sensitivity) The substrate-less double-sided adhesive sheets 1 and 8 prepared in Example 1 and Comparative Example 1 were cut to a width of 50 mm x 190 mm. The release film 2 (heavy release film) side of the obtained test piece was fixed to a glass plate using double-sided tape. An Autograph (AGS-X 50N, manufactured by Shimadzu Corporation) was used to chuck the glass plate in the lower chuck and the release film 1 (light release film) in the upper chuck. The adhesive layer was peeled off in a 180° direction at a speed of 300 mm / min, and the transfer state of the adhesive layer to the release film 1 (light release film) was judged accordingly. ○: No or minimal transfer of the adhesive layer to release film 1 (lightly release film) is observed. ×: Transfer of the adhesive layer to release film 1 (light release film) is confirmed across the entire surface.

[0134] The peel sensitivity of the substrate-less double-sided adhesive sheets 2-7, 9, and 10 prepared in Examples 2-7 and Comparative Examples 2-3 was also measured and evaluated. The results are shown in [Table 1]. Similar to Example 1 and Comparative Example 1, the light-release film was chucked and the state of adhesion of the adhesive layer to the light-release film was confirmed.

[0135] [Table 1]

[0136] In Comparative Examples 1 to 3, where a substrate-less double-sided adhesive sheet was prepared by coating a release film (heavy-release film) with a release treatment layer containing a heavy-release additive with an adhesive composition, separation occurred. On the other hand, in Examples 1 to 7, where a substrate-less double-sided adhesive sheet was prepared by coating a release film (light-release film) with a release treatment layer that does not contain a heavy-release additive with an adhesive composition, no separation occurred and good release sensitivity was obtained.

Claims

1. A method for manufacturing a substrate-less double-sided adhesive sheet, comprising an adhesive layer, a heavy release film laminated on one side of the adhesive layer, and a light release film laminated on the other side of the adhesive layer, A coating step in which an adhesive composition is applied to the aforementioned light release film to form a coating layer, A drying step of drying the coating layer to obtain the adhesive layer, A lamination step of laminating a heavy release film onto the adhesive layer, A step of curing treatment after the lamination process, Includes, A method for manufacturing a substrate-less double-sided adhesive sheet, wherein, in the substrate-less double-sided adhesive sheet after the curing process, the water contact angle on the surface of the adhesive layer on the light release film side is smaller than the water contact angle on the surface of the adhesive layer on the heavy release film side.

2. The aforementioned double-release film is a film in which a release treatment layer containing a double-release additive is formed on a plastic film. The method for manufacturing a substrate-less double-sided adhesive sheet according to claim 1, wherein the light-release film is a film in which a release treatment layer that does not contain a heavy-release additive is formed on a plastic film.

3. The method for manufacturing a substrate-less double-sided adhesive sheet according to Claim 1, wherein, in the substrate-less double-sided adhesive sheet after the curing process, the difference between the water contact angle on the surface of the adhesive layer on the light release film side and the water contact angle on the surface of the adhesive layer on the heavy release film side is 3 degrees or more.

4. A method for manufacturing a laminate comprising an optical component, an adhesive layer, and a double-release film in this order, A step of manufacturing a substrate-less double-sided adhesive sheet by the manufacturing method described in any one of claims 1 to 3, A method for manufacturing a laminate, comprising a lamination step of peeling off a light release film from the substrate-less double-sided adhesive sheet and bonding the adhesive layer and an optical member.

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