JP7630467B2 - Method for producing pressure-sensitive adhesive sheet and method for producing optical film with pressure-sensitive adhesive sheet - Google Patents

Description

The present invention relates to a method for producing a pressure-sensitive adhesive sheet and a method for producing an optical film with a pressure-sensitive adhesive sheet.

Various image display devices, such as liquid crystal display devices and electroluminescence (EL) display devices, generally include an optical laminate including an optical film such as a polarizing film and an adhesive sheet. Adhesive sheets are usually used to bond the optical films included in the optical laminate and to bond the optical laminate to an image display panel. A typical adhesive sheet is a sheet obtained by curing a monomer group including an acrylic monomer, a silicone monomer, etc., by polymerization and crosslinking. Patent Document 1 discloses a method of forming an adhesive sheet from a coating layer by irradiating light to a laminate including a base sheet, a coating layer including a photocurable composition, and a release liner in this order. In this method, both main surfaces of the coating layer are covered by the base sheet and the release liner, so that inhibition of the photocuring reaction caused by oxygen can be suppressed.

JP 2016-155981 A

Forming an adhesive sheet by curing usually requires energy such as heat or light. A method that uses light (photocuring method) can reduce the amount of energy required to form an adhesive sheet compared to a method (thermal curing method) in which a coating layer containing an adhesive composition and a solvent is thermally cured in an oven. However, from the perspective of reducing the environmental impact during the production of adhesive sheets, it is not enough to simply focus on the amount of energy required to cure the coating layer.

The present invention aims to provide technology suitable for manufacturing adhesive sheets with low environmental impact.

The present invention relates to
A step A of irradiating a laminate including a base sheet, a coating layer including a photocurable composition, and the release liner in this order with light using a release liner to form a pressure-sensitive adhesive sheet from the coating layer;
and step B of peeling the release liner from the pressure-sensitive adhesive sheet,
The steps A and B are repeatedly performed using the release liner peeled off in the step B,
As the release liner, a sheet is used which has a peel strength _PS3 with respect to the adhesive sheet of less than 1.0 N/50 mm as measured after being peeled from the adhesive sheet three times, counting from an unused state.
A method for producing a pressure-sensitive adhesive sheet,
to provide.

In another aspect, the present invention provides a method for producing a composition comprising:
A method for producing an optical film with a pressure-sensitive adhesive sheet, comprising: arranging an optical film on an exposed surface of the pressure-sensitive adhesive sheet formed by the pressure-sensitive adhesive sheet producing method of the present invention to form an optical film with a pressure-sensitive adhesive sheet;
to provide.

The present invention provides a technology suitable for manufacturing adhesive sheets with low environmental impact.

1A to 1C are schematic diagrams illustrating an example of a method for producing a pressure-sensitive adhesive sheet of the present invention. FIG. 1 is a cross-sectional view that illustrates a schematic example of a release liner that can be used in the method for producing a pressure-sensitive adhesive sheet of the present invention. 1A to 1C are schematic diagrams illustrating an example of a method for producing a pressure-sensitive adhesive sheet of the present invention. 1A to 1C are schematic diagrams illustrating an example of a method for producing a pressure-sensitive adhesive sheet of the present invention. FIG. 2 is a schematic diagram for explaining an example of a method for producing an optical film with a pressure-sensitive adhesive sheet of the present invention. FIG. 2 is a schematic diagram for explaining an example of a method for producing an optical film with a pressure-sensitive adhesive sheet of the present invention. FIG. 2 is a schematic diagram for explaining an example of a method for producing an optical film with a pressure-sensitive adhesive sheet of the present invention.

A method for producing a pressure-sensitive adhesive sheet according to a first aspect of the present invention includes the steps of:
A step A of irradiating a laminate including a base sheet, a coating layer including a photocurable composition, and the release liner in this order with light using a release liner to form a pressure-sensitive adhesive sheet from the coating layer;
and step B of peeling the release liner from the pressure-sensitive adhesive sheet,
The steps A and B are repeatedly performed using the release liner peeled off in the step B,
As the release liner, a sheet is used which has a peel strength _PS3 with respect to the adhesive sheet of less than 1.0 N/50 mm as measured after being peeled from the adhesive sheet three times, counting from an unused state.

In a second aspect of the present invention, for example, in the method for producing a pressure-sensitive adhesive sheet according to the first aspect,
The release liner has a peel strength _PS0 from the pressure-sensitive adhesive sheet of 0.01 N/50 mm or more when measured in an unused state.

In a third aspect of the present invention, for example, in the method for producing a pressure-sensitive adhesive sheet according to the first or second aspect,
The release liner has a ratio PS ₃ /PS ₀ of the peel strength PS ₃ to the peel strength PS ₀ from the pressure-sensitive adhesive sheet measured in an unused state, that is, 10 or less.

In a fourth aspect of the present invention, for example, in a method for producing a pressure-sensitive adhesive sheet according to any one of the first to third aspects,
The release liner has a peel strength PS1/PS0 ratio of the peel strength _PS1 measured after being peeled from the adhesive sheet once, counting from the unused state, to the peel strength _PS0 measured from the adhesive sheet in an _unused state, of ₁₀ or less.

In a fifth aspect of the present invention, for example, in a method for producing a pressure-sensitive adhesive sheet according to any one of the first to fourth aspects,
the release liner has a release layer on the surface of the coating layer;
The release layer has a thickness of 110 nm or less.

In a sixth aspect of the present invention, for example, in a method for producing a pressure-sensitive adhesive sheet according to any one of the first to fifth aspects,
The peel strength between the release liner and the pressure-sensitive adhesive sheet is smaller than the peel strength between the base sheet and the pressure-sensitive adhesive sheet.

In a seventh aspect of the present invention, for example, in the method for producing a pressure-sensitive adhesive sheet according to any one of the first to sixth aspects,
The photocurable composition contains a monomer group including a (meth)acrylic monomer and/or a partial polymer of the monomer group.

In an eighth aspect of the present invention, for example, in the method for producing a pressure-sensitive adhesive sheet according to the seventh aspect,
The (meth)acrylic monomer includes a carboxyl group-containing monomer.

A method for producing an optical film with a pressure-sensitive adhesive sheet according to a ninth aspect of the present invention includes the steps of:
The method includes forming an optical film with a pressure-sensitive adhesive sheet by disposing an optical film on an exposed surface of the pressure-sensitive adhesive sheet formed by the method for producing a pressure-sensitive adhesive sheet according to any one of the first to eighth aspects.

In a tenth aspect of the present invention, for example, in the method for producing an optical film with a pressure-sensitive adhesive sheet according to the ninth aspect,
The optical film includes at least one film selected from the group consisting of a polarizing film and a retardation film.

The present invention will be described in detail below, but the present invention is not limited to the following embodiments, and can be modified as desired without departing from the spirit of the present invention.

The present inventor came up with the idea of further reducing the environmental load in the manufacturing process of a pressure-sensitive adhesive sheet by reusing a release liner that was discarded immediately after peeling, and proceeded with research based on this idea to complete the present invention. The release force of a release liner after peeling from a pressure-sensitive adhesive sheet is greater than that of an unused state. Meanwhile, according to the research of the present inventor, the degree of increase in the release force tends to decrease with the number of peelings. The release force _PS3 after peeling from a pressure-sensitive adhesive sheet three times, counting from an unused state, is useful as an index reflecting the increase in the release force. A release liner with a release force _PS3 of less than 1.0 N/50 mm is suitable for repeated use. The more repeatedly used, the less release liners are discarded, and the less environmental load can be reduced.

[Method of manufacturing pressure-sensitive adhesive sheet]
An example of the method for producing a pressure-sensitive adhesive sheet of the present invention will be described with reference to FIG. 1. In this example, a first laminate 10 including a base sheet 11, a coating layer 12 containing a photocurable composition, and a release liner 13 in this order is irradiated with light 14 to form a pressure-sensitive adhesive sheet 1 from the coating layer 12 (step A). The light 14 penetrates the release liner 13 to reach the coating layer 12, and cures the coating layer 12. However, the irradiation with light 14 may be performed from the side of the base sheet 11, or from both the side of the release liner 13 and the base sheet 11. In step A, the pressure-sensitive adhesive sheet 1 is formed using the release liner 13. The formed pressure-sensitive adhesive sheet 1 is sandwiched between the base sheet 11 and the release liner 13 to form a part of the second laminate 17 until the release liner 13 is peeled off. After step A, the release liner 13 is peeled off from the pressure-sensitive adhesive sheet 1 (step B). 1 , steps A and B are repeatedly performed using the release liner 13 peeled off in step B. Step A using the peeled release liner 13 is performed by forming a first laminate 10 including, in this order, a base sheet 11, a coating layer 12, and the peeled release liner 13, and irradiating the formed first laminate 10 with light 14.

In the method of Fig. 1, a release liner 13 is used that has a peel strength _PS3 with respect to the adhesive sheet 1 of less than 1.0 N/50 mm, measured after being peeled from the adhesive sheet 1 three times, counting from an unused state. With the implementation of step A, the peel strength of the release liner 13 with respect to the adhesive sheet 1 usually increases. It is presumed that the increase in peel strength is due to an increase in the amount of functional groups or radicals present on the surface of the release liner 13 on the side of the coating layer 12 due to the irradiation with light 14. The increase may be due to the fact that a chemical bond is formed between the release liner 13 and the adhesive sheet 1 by the irradiation with light 14, and a part of the bond or a group formed by decomposition of the bond remains on the surface even after the adhesive sheet 1 is peeled off.

<Step A>
(Release liner)
The release force _PS3 of the release liner 13 may be 0.9 N/50 mm or less, 0.8 N/50 mm or less, 0.7 N/50 mm or less, 0.6 N/50 mm or less, 0.5 N/50 mm or less, 0.4 N/50 mm or less, 0.3 N/50 mm or less, 0.2 N/50 mm or less, or even 0.15 N/50 mm or less. The lower limit of the release force _PS3 is, for example, 0.01 N/50 mm or more, and may be 0.03 N/50 mm or more, 0.05 N/50 mm or more, 0.08 N/50 mm or more, or even 0.1 N/50 mm or more.

The release liner 13 may have a peel strength _PS0 from the PSA sheet 1 measured in an unused state of 0.01 N/50 mm or more, 0.02 N/50 mm or more, or even 0.03 N/50 mm or more. The upper limit of the peel strength _PS0 is, for example, 0.2 N/50 mm or less, and may be 0.17 N/50 mm or less, 0.15 N/50 mm or less, 0.12 N/50 mm or less, or even 0.1 N/50 mm or less.

The ratio _PS3 / _PS0 of the peel strength _PS3 from the PSA sheet 1 measured in an unused state to _PS0 may be 10 or less, or may be 7 or less, 5 or less, 4 or less, 3 or less, 2 or less, or even 1.8 or less. The lower limit of the ratio _PS3 / _PS0 is, for example, 1.1 or more, or even 1.2 or more.

The release liner 13 may have a ratio PS1 _/PS0 of the peel strength from the adhesive sheet 1 measured after peeling it once from the adhesive sheet 1 counting from the unused state to the peel strength _PS0 from the adhesive sheet ₁ measured in an unused state, which may be 10 or less, or may be 7 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1.8 or less, or even 1.7 or less. The lower limit of _the ratio _PS1 / _PS0 is, for example, 1.05 or more, or even 1.1 or more.

The peel strength PS _n (n is an integer equal to or greater than 0 corresponding to the number of peels; when n=0, the peel strength PS ₀ in the unused state) after n peelings from the pressure-sensitive adhesive sheet 1, counting from an unused state, can be evaluated by carrying out step A and step B n times using the release liner to be evaluated, and then carrying out step A for the (n+1)th time to form a second laminate 17, which is cut to a width of 50 mm to prepare a test piece, and carrying out a 180° peel test in which only the release liner 13 is peeled off from the prepared test piece. The peel test is carried out about 0.5 to 1 hour after the formation of the pressure-sensitive adhesive sheet 1. From the formation of the pressure-sensitive adhesive sheet 1 until the peel test is carried out, the second laminate 17 and the test piece are placed in an air atmosphere at 23° C.±5° C. A tensile tester can be used for the peel test. More specifically, the entire surface of the test piece on the side of the base sheet 11 is fixed to a fixing plate (e.g., a SUS plate) with a double-sided adhesive tape, and one end of the fixing plate in the length direction is fixed to the upper chuck of a tensile tester, and the end of the release liner 13 on the side of the upper chuck is peeled off, folded back 180°, and fixed to the lower chuck of the tensile tester. The fixing plate can be one having sufficient mechanical strength to stably perform the peel test. The double-sided adhesive tape can be one having sufficient adhesive strength to prevent the base sheet 11 from peeling off from the fixing plate during the peel test. The peel test is performed at a peel speed of 300 mm/min and at a test temperature of 23°C ± 5°C. If the width of the second laminate 17 is less than 50 mm, the measured value at the original width may be converted to a value per 50 mm width. If the formation direction of the coating layer 12 can be determined, the TD perpendicular to the MD, which is the direction of the coating layer 12, can be determined as the width direction of the test piece. When the base sheet 11 and the release liner 13 are long, the width direction thereof can be set as the width direction of the test piece.

The peel forces PS ₀ , PS _n and the degree of increase in PS _n due to repeated peeling can vary depending on, for example, the composition of the photocurable composition, the composition, formation conditions and thickness of the adhesive sheet 1 to be formed, the material, thickness and condition of the release surface of the release liner 13, and the composition, formation conditions and thickness of the release layer that the release liner 13 may have.

An example of the substrate of the release liner 13 (hereinafter referred to as the "liner substrate") is a resin film. Examples of resins that may be contained in the liner substrate are polyesters such as polyethylene terephthalate and polyethylene naphthalate, acetate resins, polyethersulfone, polycarbonate, polyamide, polyimide, polyolefin, (meth)acrylic resins, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl alcohol, polyarylate, and polyphenylene sulfide. The resin is preferably a polyester such as polyethylene terephthalate.

It is preferable that the release liner 13 has excellent transparency to the light 14 irradiated in step A.

The thickness of the release liner 13 is, for example, 10 to 200 μm, and may be 25 to 150 μm.

The release liner 13 may have a layer other than the liner substrate. The release liner 13 may have a release layer. The release liner 13 in FIG. 2 has a liner substrate 131 and a release layer 132 formed on one surface of the liner substrate 131. The release liner 13 in FIG. 2 can be used such that the release layer 132 is on the coating layer 12 side.

The release layer 132 is typically a cured layer of a release agent composition containing a release agent. Various types of release agents can be used, such as silicone-based release agents, fluorine-based release agents, long-chain alkyl-based release agents, fatty acid amide-based release agents, and silica powder. The release liner 13 may have a cured layer of a release agent composition containing a silicone-based release agent as the main component (hereinafter, "silicone release layer"). The silicone release layer is particularly suitable for achieving both adhesion and releasability to the acrylic adhesive sheet 1. In this specification, the main component means the component with the largest content.

The silicone-based release agent is, for example, a variety of curable silicone materials such as addition reaction type, condensation reaction type, ultraviolet curable type, electron beam curable type, and solventless type, and addition reaction curable silicone materials are preferred. Addition reaction curable silicone materials are particularly suitable for forming a release layer that is compatible with adhesion and releasability to the acrylic adhesive sheet 1. The curable silicone material may be a silicone-modified resin in which reactive silicone is introduced into an organic resin such as urethane, epoxy, or alkyd resin by graft polymerization or the like.

An example of the addition reaction curing silicone material is a polyorganosiloxane having a vinyl group or an alkenyl group in the molecule. The addition reaction curing silicone material may not have a hydrosilyl group. Examples of the alkenyl group are 3-butenyl, 4-pentenyl, 5-hexenyl, 6-heptenyl, 7-octenyl, 8-nonenyl, 9-decenyl, 10-undecenyl, and 11-dodecenyl. Examples of the polyorganosiloxane are polyalkylalkylsiloxanes such as polydimethylsiloxane, polydiethylsiloxane, and polymethylethylsiloxane, polyalkylarylsiloxane, and copolymers of multiple types of Si atom-containing monomers such as poly(dimethylsiloxane-diethylsiloxane). The polyorganosiloxane is preferably polydimethylsiloxane.

A release agent composition containing a silicone-based release agent as a main component (hereinafter referred to as "silicone release agent composition") usually contains a crosslinking agent. An example of the crosslinking agent is a polyorganosiloxane having a hydrosilyl group. The crosslinking agent may have two or more hydrosilyl groups in one molecule.

The silicone release agent composition may contain a curing catalyst. An example of the curing catalyst is a platinum-based catalyst. Examples of the platinum-based catalyst are chloroplatinic acid, platinum olefin complexes, and chloroplatinic acid olefin complexes. The amount of the platinum-based catalyst used is, for example, 10 to 1000 ppm (by weight, platinum equivalent) based on the total solid content of the composition.

The silicone release agent composition may contain additives. Examples of additives are release control agents and adhesion promoters. Examples of release control agents are unreactive silicone resins, and more specific examples are organosiloxanes such as octamethylcyclotetrasiloxane, and MQ resins. The amount of the release control agent and adhesion promoter used is, for example, 1 to 30% by weight in total based on the total solid content of the composition. Further examples of additives are fillers, antistatic agents, antioxidants, ultraviolet absorbers, plasticizers, and colorants. The amount of the further additives used is, for example, 10% by weight or less in total based on the total solid content of the composition.

The silicone release agent composition may contain an organic solvent. Examples of organic solvents are hydrocarbon solvents such as cyclohexane, n-hexane, and n-heptane; aromatic solvents such as toluene and xylene; ester solvents such as ethyl acetate and methyl acetate; ketone solvents such as acetone and methyl ethyl ketone; and alcohol solvents such as methanol, ethanol, and butanol. Two or more types of organic solvents may be contained. The amount of the organic solvent used is preferably 80 to 99.9% by weight of the silicone release agent composition.

The release layer 132 can be formed, for example, by heating and drying a coating film containing a release agent composition formed on the liner substrate 131. Various coating methods can be used to apply the release agent composition, such as roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coating. For example, hot air drying can be used to heat and dry. The heating temperature and time vary depending on the heat resistance of the liner substrate, but are usually 80 to 150°C and about 10 seconds to 10 minutes. If necessary, irradiation with active energy rays such as ultraviolet rays may be used in combination.

The thickness of the release layer 132 is, for example, 10 to 300 nm. The upper limit of the thickness may be 200 nm or less, 150 nm or less, 120 nm or less, 110 nm or less, 100 nm or less, less than 100 nm, 90 nm or less, 80 nm or less, 70 nm or less, less than 70 nm, or even 65 nm or less. The lower limit of the thickness may be 15 nm or more, 20 nm or more, 25 nm or more, 30 nm or more, 35 nm or more, 40 nm or more, 45 nm or more, or even 50 nm or more. The thickness of the release layer 132 may be 110 nm or less, in other words, the release liner 13 may have a release layer 132 on the surface on the side of the coating layer 12, and the thickness of the release layer 132 may be 110 nm or less.

The release liner 13 may be in sheet or elongated form.

(Base sheet)
An example of the base sheet 11 is a resin film. Examples of the resin contained in the base sheet 11 are the same as the examples of the resin that can be contained in the liner base material.

The base sheet 11 may be transparent to the light 14 irradiated in step A, or may have the same degree of transparency to the light 14 as the release liner 13.

The thickness of the base sheet 11 is, for example, 10 to 200 μm, and may be 25 to 150 μm.

The base sheet 11 may have a release layer on the surface on the side of the coating layer 12. Examples of the release layer that the base sheet 11 may have and the manufacturing method thereof are the same as the examples of the release layer that the release liner 13 may have and the manufacturing method thereof. Both the release liner 13 and the base sheet 11 may have a release layer. In this case, both release layers may be formed from a release agent composition containing the same release agent as a main component. In addition, the thicknesses of both release layers may be different; for example, the release layer provided on the base sheet 11 may be thicker.

For the base sheet 11, a sheet that has a greater peel strength with respect to the adhesive sheet 1 than the release liner 13 can usually be selected.

The base sheet 11 may be in the form of a sheet or a long piece.

(Photocurable composition)
The photocurable composition is a composition that can form the adhesive sheet 1 from the coating layer 12 by irradiation with light 14. The photocurable composition contains, for example, a monomer group containing a (meth)acrylic monomer and/or a partial polymer of the monomer group. The content of the (meth)acrylic component in the photocurable composition, i.e., the (meth)acrylic monomer and its partial polymer, may be 50% by weight or more, 60% by weight or more, 70% by weight or more, or even 80% by weight or more. In this case, an acrylic adhesive sheet 1 containing a (meth)acrylic polymer and its crosslinked product as the main components can be formed. However, the photocurable composition is not limited to the above example. In this specification, (meth)acrylic means acrylic and methacrylic. (Meth)acrylate means acrylate and methacrylate.

An example of a (meth)acrylic monomer is a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms on the side chain. The number of carbon atoms in the alkyl group may be 7 or less, 6 or less, 5 or less, or even 4 or less. The alkyl group may be linear or branched. Examples of (meth)acrylic acid alkyl esters are methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate (lauryl (meth)acrylate), n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, and octadecyl (meth)acrylate. The (meth)acrylic acid alkyl ester may be n-butyl (meth)acrylate.

The content of the (meth)acrylic acid alkyl ester in the monomer group is, for example, 40% by weight or more, and may be 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, or even 95% by weight or more. In calculating the content, the weight of the partially polymerized product is converted into the weight of each monomer before polymerization.

The monomer group may contain a carboxyl group-containing monomer. The carboxyl group-containing monomer may be a (meth)acrylic monomer, in other words, the (meth)acrylic monomer may contain a carboxyl group-containing monomer. Examples of the carboxyl group-containing monomer are (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. The content of the carboxyl group-containing monomer in the monomer group may be, for example, 10% by weight or less, 9% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5.5% by weight or less, or even 5% by weight or less. The lower limit of the content may be, for example, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. The monomer group may not contain a carboxyl group-containing monomer.

The rate of polymerization and curing of the carboxyl group-containing monomer by irradiation with light 14 is usually higher than that of a (meth)acrylic acid alkyl ester not containing a carboxyl group. The higher rate means that the elastic modulus of the pressure-sensitive adhesive sheet 1 can be increased to improve the dimensional stability against deformation force, while the peel force of the release liner from the pressure-sensitive adhesive sheet 1 tends to be large. For this reason, the use of a release liner 13 with a suppressed peel force PS ₃ is particularly advantageous when the photocurable composition contains a carboxyl group-containing monomer.

The monomer group may contain a hydroxy group-containing monomer. The hydroxy group-containing monomer may be a (meth)acrylic monomer, in other words, the (meth)acrylic monomer may contain a hydroxy group-containing monomer. The hydroxy group-containing monomer may contribute to improving the cohesive strength of the adhesive sheet 1. Examples of the hydroxy group-containing monomer are 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methyl acrylate. The hydroxy group-containing monomer is preferably 2-hydroxyethyl (meth)acrylate or 4-hydroxybutyl (meth)acrylate. The content of the hydroxyl group-containing monomer in the monomer group is, for example, 5% by weight or less, and may be 4% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, 0.8% by weight or less, 0.5% by weight or less, 0.3% by weight or less, 0.2% by weight or less, or even 0.1% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.03% by weight or more, or even 0.05% by weight or more. The monomer group may not contain a hydroxyl group-containing monomer.

In the photocurable composition, each of the above-mentioned monomers may be contained as a partial polymer. The partial polymer may be either a homopolymer or a copolymer. The partial polymer may contribute to the stable formation of the coating layer 12 by appropriately increasing the viscosity of the photocurable composition.

The photocurable composition usually contains a photopolymerization initiator. An example of a photopolymerization initiator is a photoradical generator that generates radicals in response to visible light and/or ultraviolet light having a wavelength shorter than 450 nm.

Examples of photopolymerization initiators include benzoin ethers such as benzoin methyl ether, benzoin isopropyl ether, and benzil dimethyl ketal; substituted benzoin ethers such as anisole methyl ether; substituted acetophenones such as 2,2-diethoxyacetophenone and 2,2-dimethoxy-2-phenylacetophenone; α-hydroxyalkylphenones such as 1-hydroxycyclohexyl-phenyl ketone; substituted alpha-ketol such as 2-methyl-2-hydroxypropiophenone; aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride; and photoactive compounds such as 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. Oximes; benzophenone compounds such as benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, and 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and 2,4-diethylthioxanthone; 2,4,6-trichloro-s-triazine, 2-phenyl-4,6-bis(trichloromethyl)-s- triazine, 2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, 2-(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine, 2-piperonyl-4,6-bis(trichloromethyl)-s-triazine, 2,4-bis(trichloromethyl)-6-styryl-s-triazine, 2-(naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-methoxy-naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2,4-trichloromethyl-(piperonyl)-6-triazine, 2,4-trichloromethyl-(4'-methoxystyryl)-6-triazine, etc. triazine-based compounds; oxime ester-based compounds such as 1,2-octanedione, 1-[4-(phenylthio)-, 2-(O-benzoyloxime)], O-(acetyl)-N-(1-phenyl-2-oxo-2-(4'-methoxy-naphthyl)ethylidene)hydroxylamine; phosphine-based compounds such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; quinone-based compounds such as 9,10-phenanthrenequinone, camphorquinone, and ethylanthraquinone; borate-based compounds; carbazole-based compounds; imidazole-based compounds; and titanocene-based compounds. The photocurable composition may contain one or more photopolymerization initiators.

The amount of photopolymerization initiator in the photocurable composition is, for example, 0.02 to 10 parts by weight, and may be 0.05 to 5 parts by weight, per 100 parts by weight of the total of the monomer group and its partial polymer.

The photocurable composition may contain a crosslinking agent. An example of the crosslinking agent is a polyfunctional monomer having two or more polymerizable functional groups in one molecule. The polyfunctional monomer may be a (meth)acrylic monomer. An example of the polyfunctional monomer is a monomer having two or more C=C bonds in one molecule, and a monomer having one or more C=C bonds and one or more polymerizable functional groups such as epoxy groups, aziridine groups, oxazoline groups, hydrazine groups, and methylol groups in one molecule. The polyfunctional monomer is preferably a monomer having two or more C=C bonds in one molecule.

Examples of crosslinking agents include (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol diacrylate (NDD A), polyfunctional acrylates (such as ester compounds of polyhydric alcohols and (meth)acrylic acid) such as 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and tetramethylolmethane tri(meth)acrylate; allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl di(meth)acrylate, and hexyl di(meth)acrylate. The polyfunctional monomer is preferably a polyfunctional acrylate, and more preferably trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

The amount of the crosslinking agent to be blended varies depending on the molecular weight, the number of functional groups, etc., but may be, for example, 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or even 0.5 parts by weight or less per 100 parts by weight of the total of the monomer group and its partial polymer. The lower limit of the blending amount may be, for example, 0.01 parts by weight or more, or even 0.05 parts by weight or more.

The photocurable composition may contain additives other than those mentioned above. Examples of additives include chain transfer agents, silane coupling agents, viscosity modifiers, tackifiers, plasticizers, softeners, antioxidants, fillers, colorants, antioxidants, surfactants, antistatic agents, and UV absorbers.

The content of the solvent in the photocurable composition is, for example, 5% by weight or less, and may be 4% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, or even 0.5% by weight or less. The photocurable composition may be substantially free of solvent. "Substantially free of solvent" means that solvents derived from additives, etc. are permitted at a content of, for example, 0.1% by weight or less, preferably 0.05% by weight or less, and more preferably 0.01% by weight or less.

The viscosity of the photocurable composition is preferably 5 to 100 poise. Photocurable compositions having a viscosity in the above range are particularly suitable for forming the coating layer 12.

(First Laminate and Its Formation)
The first laminate 10 may include an additional layer other than the base sheet 11, the coating layer 12, and the release liner 13. The additional layer may be disposed on the side of the base sheet 11 and/or the release liner 13 opposite to the side of the coating layer 12. It is preferable that the coating layer 12 is in contact with the base sheet 11 and the release liner 13.

The first laminate 10 can be formed, for example, by forming a coating layer 12 on a base sheet 11 (or a release liner 13) and then placing a release liner 13 (or base sheet 11) on the formed coating layer 12. Alternatively, the first laminate 10 may be formed by applying a photocurable composition by pouring it into the space between the base sheet 11 and the release liner 13, which are held at a predetermined distance so that their main surfaces face each other. The peeled release liner 13 may be used so that the surface that was on the side of the coating layer 12 in step A immediately before peeling, for example the surface on the release layer 132 side, becomes the side of the coating layer 12 again.

Various coating methods can be used to form the coating layer 12, including roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coating.

The thickness of the coating layer 12 can be adjusted according to the thickness of the adhesive sheet 1 desired, and may be, for example, 5 to 100 μm, 5 to 50 μm, 5 to 25 μm, or even 5 to 20 μm.

The first laminate 10 may include a long base sheet 11, a long coating layer 12, and a long release liner 13, or in other words, may be long. The long first laminate 10 can be obtained, for example, by forming the coating layer 12 between the base sheet 11 and the release liner 13 while conveying them from a roll.

(Light irradiation)
The light 14 irradiated to the first laminate 10 is, for example, visible light or ultraviolet light having a wavelength shorter than 450 nm. The light 14 may contain light having a wavelength in the same region as the absorption wavelength of the photopolymerization initiator contained in the photocurable composition. The light 14 may be irradiated with light having a short wavelength of 300 nm or less cut by a filter or the like, and cutting the short wavelength light is suitable for suppressing deterioration of the release liner 13 caused by the light 14. The light source of the light 14 is, for example, a light irradiation device equipped with an ultraviolet irradiation lamp. Examples of the ultraviolet irradiation lamp are ultraviolet light LED, low pressure mercury lamp, medium pressure mercury lamp, high pressure mercury lamp, ultra-high pressure mercury lamp, metal halide lamp, xenon lamp, microwave excited mercury lamp, black light lamp, chemical lamp, germicidal lamp, low pressure discharge mercury lamp, and excimer laser. Two or more ultraviolet irradiation lamps may be combined.

The irradiation of light 14 may be continuous or intermittent.

The irradiation intensity of the light 14 is, for example, 1 to 20 mW/cm ^2. The integrated light amount of the light 14 on the first laminate 10 is, for example, 100 to 5000 mJ/cm ² .

The polymerization rate of the monomer group in the adhesive sheet 1 is preferably 90% or more. The polymerization rate may be 95% or more, 98% or more, or even 99% or more.

The gel fraction of the adhesive sheet 1 is, for example, 50% or more, and may be 75% or more, 80% or more, or even 85% or more.

<Step B>
In step B, the release liner 13 is peeled off from the cured second laminate 17. The second laminate 17 includes, in this order, a base sheet 11, a pressure-sensitive adhesive sheet 1, and a release liner 13. By the above peeling, a third laminate 15 including the release liner 13, the base sheet 11, and the pressure-sensitive adhesive sheet 1 is obtained.

The peel strength between the release liner 13 and the adhesive sheet 1 may be smaller than the peel strength between the base sheet 11 and the adhesive sheet 1.

The peel strength of the base sheet 11 against the adhesive sheet 1 is, for example, 0.1 to 10 N/50 mm, and may be 1 to 8 N/50 mm, 2 to 7 N/50 mm, or even 3 to 5 N/50 mm.

The number of times that the release liner 13 is peeled off and reused in the production of the PSA sheet 1 is not particularly limited, and may be, for example, 3 or more times, 5 or more times, or even 7 or more times. There is no particular upper limit to the number of times, and use may be continued as long as the peel force _PSn from the PSA sheet 1 does not exceed 3.0 N/50 mm, for example.

The peeled release liner 13 may be re-used after being wound into a roll.

The thickness of the adhesive sheet 1 is, for example, 2 to 70 μm, and may be 2 to 50 μm, 5 to 40 μm, 10 to 30 μm, 10 to 25 μm, or even 10 to 20 μm.

The adhesive sheet 1 can be used, for example, in an optical laminate including an optical film. In other words, the adhesive sheet 1 may be for an optical laminate. The optical laminate may be an optical film with an adhesive sheet. However, the uses of the adhesive sheet 1 are not limited to the above examples.

With reference to FIG. 3, another example of the method for manufacturing the adhesive sheet of the present invention will be described. In this example, a coating layer 12 of a photocurable composition is formed on one side of a long base sheet 11 unwound from a roll 31 by a coating device 32. Next, a long release liner 13 unwound from a roll 33 is placed on the coating layer 12 to form a long first laminate 10. Next, light 14 is irradiated from a light irradiation device 34 to the first laminate 10 to form a long adhesive sheet 1. Next, the release liner 13 is peeled off from a second laminate 17 including the adhesive sheet 1 and wound up on a roll 35. The above steps are performed while transporting the base sheet 11 and the release liner 13. The wound release liner 13 is reused. The third laminate 15 formed by peeling off the release liner 13 can be used, for example, for an optical film with an adhesive sheet or for the manufacture thereof. The method of FIG. 3 is particularly suitable for mass production of the adhesive sheet 1.

With reference to Figure 4, another example of the method for producing an adhesive sheet of the present invention will be described. This example is the same as the example of Figure 3, except that the release liner 13 peeled off from the second laminate 17 is reused in the production of the adhesive sheet 1 without being wound up into a roll 35. The method of Figure 4 is particularly suitable for mass production of the adhesive sheet 1.

[Release liner]
According to a different aspect of the present invention, there is provided a release liner for use in the method for producing a pressure-sensitive adhesive sheet of the present invention. Examples of the release liner are the same as those mentioned above in the description of the method for producing a pressure-sensitive adhesive sheet.

[Method of manufacturing optical film with adhesive sheet]
With reference to FIG. 5, an example of the manufacturing method of the optical film with adhesive sheet of the present invention will be described. In this example, the optical film 2 is arranged on the exposed surface 18 of the adhesive sheet 1 formed by peeling the release liner 13 from the second laminate 17 including the base sheet 11, the adhesive sheet 1, and the release liner 13 in this order, to form the optical film with adhesive sheet 21. The optical film with adhesive sheet 21 includes the base sheet 11, the adhesive sheet 1, and the optical film 2 in this order. The second laminate 17 can be formed by the above-mentioned process A. The peeling of the release liner 13 may be performed as the above-mentioned process B. The optical film with adhesive sheet 21 can be used as it is or after peeling the base sheet 11, for example, as an optical laminate including the adhesive sheet 1 and the optical film 2 in an image display device or the like. The optical laminate may be attached to an object (for example, an image forming panel) via the adhesive sheet 1. However, the use of the optical film with adhesive sheet 21 is not limited to the above example. An additional member such as an optical film may be disposed on the exposed surface 18 formed by peeling the base sheet 11 from the optical film 21 with the adhesive sheet, and as one example, an optical film 22 with the adhesive sheet can be formed that includes an optical film 2A, an adhesive sheet 1, and an optical film 2B in this order (see FIG. 6). The optical films 2A and 2B may be the same or different from each other.

The optical film 2 may be disposed directly or indirectly on the exposed surface 18. In other words, the optical film 2 may be disposed so as to be in contact with the exposed surface 18, or may be disposed with another layer sandwiched between the optical film 2 and the exposed surface 18.

With reference to FIG. 7, another example of the method for manufacturing an optical film with a pressure-sensitive adhesive sheet of the present invention will be described. In this example, a long optical film 2 is placed on the exposed surface 18 of the pressure-sensitive adhesive sheet 1 in the third laminate 15 formed by the method of FIG. 3 to form a long optical film with a pressure-sensitive adhesive sheet 21. The optical film 2 is unwound from a roll 36 and placed on the exposed surface 18. As shown in FIG. 7, the formation of the pressure-sensitive adhesive sheet 1 and the formation of the optical film with a pressure-sensitive adhesive sheet 21 may be carried out continuously. The method of FIG. 7 is particularly suitable for mass production of the optical film with a pressure-sensitive adhesive sheet 21.

The optical film 2 is, for example, a film including at least one selected from the group consisting of a polarizing film and a retardation film. The optical film 2 may be a laminated film including a polarizing film and/or a retardation film. The optical film 2 may include a glass film. However, the optical film 2 is not limited to the above examples.

The polarizing film includes a polarizer. The polarizing film typically includes a polarizer and a protective film (transparent protective film). The protective film is, for example, disposed in contact with the main surface (the surface having the widest area) of the polarizer. The polarizer may be disposed between two protective films. The protective film may be disposed on at least one surface of the polarizer.

The polarizer is not particularly limited, and examples thereof include hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified ethylene-vinyl acetate copolymer films, which are uniaxially stretched after adsorbing dichroic substances such as iodine and dichroic dyes; and polyene-based oriented films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride. Polarizers are typically made of polyvinyl alcohol films (polyvinyl alcohol films include partially saponified ethylene-vinyl acetate copolymer films) and dichroic substances such as iodine.

The thickness of the polarizer is not particularly limited, and may be, for example, 80 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, or even 20 μm or less. The lower limit of the thickness of the polarizer is not particularly limited, and may be, for example, 1 μm or more, 5 μm or more, 10 μm or more, or even 15 μm or more. A thin polarizer (for example, a thickness of 20 μm or less) suppresses dimensional changes and can contribute to improving the durability of the optical laminate, particularly the durability at high temperatures.

As the material of the protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture blocking property, isotropy, etc. is used. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The material of the protective film may be a thermosetting resin or an ultraviolet-curing resin such as a (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone. When the polarizing film has two protective films, the materials of the two protective films may be the same or different from each other. For example, a protective film made of a thermoplastic resin may be attached to one main surface of the polarizer via an adhesive, and a protective film made of a thermosetting resin or an ultraviolet-curing resin may be attached to the other main surface of the polarizer. The protective film may contain one or more types of additives. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, color inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, colorants, etc.

The thickness of the protective film can be determined as appropriate, but is generally about 10 to 200 μm, taking into consideration strength, ease of handling, thinness, etc.

The polarizer and the protective film are usually adhered to each other via a water-based adhesive or the like. Examples of water-based adhesives include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl latex, water-based polyurethane, water-based polyester, and the like. Examples of adhesives other than the above-mentioned adhesives include ultraviolet-curable adhesives and electron beam-curable adhesives. Electron beam-curable polarizing plate adhesives exhibit suitable adhesion to various protective films. The adhesive may contain a metal compound filler.

In polarizing films, instead of a protective film, a retardation film or the like can be formed on the polarizer. Another protective film can be further provided on the protective film, or a retardation film or the like can be provided.

The protective film may have a hard coat layer on the surface opposite to the surface attached to the polarizer, and may also be treated for the purposes of anti-reflection, anti-sticking, diffusion, anti-glare, etc.

The polarizing film may be a circular polarizing film.

The retardation film may be one obtained by stretching a polymer film or one obtained by aligning and fixing a liquid crystal material. The retardation film has birefringence, for example, in the in-plane and/or thickness direction.

Retardation films include anti-reflection retardation films (see JP 2012-133303 A [0221], [0222], [0228]), viewing angle compensation retardation films (see JP 2012-133303 A [0225], [0226]), and tilted orientation retardation films for viewing angle compensation (see JP 2012-133303 A [0227]).

The specific configuration of the retardation film, such as the retardation value, arrangement angle, three-dimensional birefringence, whether it is a single layer or a multilayer, is not particularly limited, and any known retardation film can be used.

The thickness of the retardation film is preferably 20 μm or less, more preferably 10 μm or less, even more preferably 1 to 9 μm, and particularly preferably 3 to 8 μm.

The retardation film may include, for example, a quarter-wave plate and/or a half-wave plate in which liquid crystal material is oriented and fixed.

An image display device may be formed using the optical film with adhesive sheet formed by the above manufacturing method. The image display device may be formed, for example, by bonding the optical film with adhesive sheet 21, 22 to an image display panel. The bonding may be performed using the adhesive sheet 1. The image display device may be an organic EL display or a liquid crystal display. However, the image display device is not limited to the above examples. The image display device may be an electroluminescence (EL) display, a plasma display (PD), a field emission display (FED), etc. The image display device may be used for home appliance applications, in-vehicle applications, public information display (PID) applications, etc.

The present invention will be described in more detail below with reference to examples. The present invention is not limited to the examples shown below.

(Production Example 1: Preparation of photocurable composition)
100 parts by weight of n-butyl acrylate (BA), 5 parts by weight of acrylic acid (AA), 0.1 parts by weight of 2-hydroxyethyl acrylate (2HEA), and 0.05 parts by weight of each of Omnirad 184 and Omnirad 651 (both manufactured by IGM Resins) as photopolymerization initiators were charged into a four-bottom flask, and ultraviolet rays were irradiated under a nitrogen atmosphere to obtain a partially photopolymerized monomer syrup. The ultraviolet rays were irradiated until the viscosity of the solution in the flask (measurement conditions: BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30°C) became about 20 Pa·s. Next, 0.1 parts by weight of 1,9-nonanediol diacrylate (NDDA) as a crosslinking agent was uniformly mixed with 100 parts by weight of the monomer syrup to obtain a photocurable composition.

(Production Example 2: Preparation of Release Liner A)
Addition reaction curing type silicone (LTC761 containing hexenyl group-containing polyorganosiloxane, 30 wt% toluene solution, manufactured by Toray Dow Corning) 100 parts by weight, release control agent (BY24-850 containing unreactive silicone resin, manufactured by Toray Dow Corning) 0.9 parts by weight, and curing catalyst (SRX212 containing platinum catalyst, manufactured by Toray Dow Corning) 2 parts by weight, and toluene / hexane mixed solvent (volume ratio 1: 1) as a dilution solvent were mixed to obtain a silicone-based release agent composition A. The concentration of silicone solids in the release agent composition A was 1.0 wt%. Next, the release agent composition A was applied to one side of a liner substrate (Lumirror 38R75, a polyester film, thickness 38 μm) with a wire bar, and heated at 130 ° C. for 1 minute to produce a release liner A having a release layer (thickness 60 nm) on one side.

(Production Example 3: Preparation of Release Liner B)
A release liner B having a release layer (thickness 120 nm) on one side was prepared in the same manner as in Production Example 2, except that the thickness of the release agent composition A applied to the liner substrate was changed.

(Production Example 4: Preparation of Release Liner C)
33.3 parts by weight of addition reaction curing type silicone (KS-847T containing vinyl group-containing polyorganosiloxane, 30 wt% toluene solution, Shin-Etsu Chemical Co., Ltd.), 1 part by weight of curing catalyst (CAT-PL-50T containing platinum catalyst, Shin-Etsu Chemical Co., Ltd.), and a toluene/hexane mixed solvent (volume ratio 1:1) as a dilution solvent were mixed to obtain a silicone-based release agent composition C. The concentration of silicone solids in the release agent composition C was 1.0 wt%. Next, the release agent composition C was applied with a wire bar to one side of a liner substrate (Lumirror 38R75, a polyester film, thickness 38 μm), and heated at 130° C. for 1 minute to produce a release liner C having a release layer (thickness 100 nm) on one side.

(Production Example 5: Preparation of Release Liner D)
Addition reaction curing type silicone (KS-847H containing vinyl group-containing polyorganosiloxane, 30 wt% toluene solution, Shin-Etsu Chemical Co., Ltd.) 66.6 parts by weight, curing catalyst (CAT-PL-50T containing platinum catalyst, Shin-Etsu Chemical Co., Ltd.) 0.2 parts by weight, and a toluene/hexane mixed solvent (volume ratio 1:1) as a dilution solvent were mixed to obtain a silicone-based release agent composition D. The silicone solid content concentration in the release agent composition D was 1.0 wt%. Next, the release agent composition D was applied with a wire bar to one side of a liner substrate (Lumirror 38R75, a polyester film, thickness 38 μm), and heated at 130° C. for 1 minute to produce a release liner D having a release layer (thickness 100 nm) on one side.

[Evaluation of peel strength PS ₀ ]
The photocurable composition of Production Example 1 was applied to one side of a substrate sheet (Lumirror 38R75, a polyester film without a release layer, thickness 38 μm) with an applicator to form a coating layer. Next, the release liners of Production Examples 2 to 5 were placed on the formed coating layer to obtain a first laminate. The release liners were placed so that the release layer was in contact with the coating layer. Next, ultraviolet light (black light source) was irradiated from the release liner side of the first laminate under conditions of an illuminance of 2.4 mW/ ^cm2 and an integrated light quantity of 2880 mJ/ ^cm2 to photocure the coating layer, thereby forming a second laminate a composed of the substrate sheet, the adhesive sheet (thickness 20 μm), and the release liner.

A test piece 220 mm long and 50 mm wide (the length direction was the coating direction of the photocurable composition) was cut out from the formed second laminate a. The entire surface of the base sheet side of the test piece was fixed to a SUS plate as a fixing plate, and a 180° peel test was performed using a tensile tester to peel only the release liner in the length direction to evaluate the peel force _PS0 . The peel test conditions were as described above.

[Evaluation of peel strengths PS ₁ , PS ₂ , and PS ₃ ]
A part of the second laminate a in the length direction was cut off so that the sampled area was not included, and then the release liner was peeled off for reuse. A second laminate b was formed in the same manner as the formation of the second laminate a, except that the peeled release liner was used. A release force PS ₁ was evaluated in the same manner as the evaluation of the release force PS ₀ , except that the test piece cut out from the second laminate b was used as the evaluation object. Next, a second laminate c (second reuse) was formed from the second laminate b, and a second laminate d (third reuse) was formed from the second laminate c in the same manner as the above method of peeling the release liner from the second laminate a and reusing the peeled release liner to form the second laminate b. A release force PS 2 and a release force PS 3 were evaluated in the same manner as the evaluation of the release force PS ₀ , except that the test pieces cut out from the _second laminate c and the second laminate _d were used as the evaluation objects.

[Evaluation of ease of peeling of release liner with only the edge fixed (ease of peeling)]
For the second laminate d, both ends in the length direction were fixed to a fixing surface with double-sided adhesive tape on the base sheet side, and the release liner was peeled off from one of the ends. Depending on the state of peeling, the ease of peeling was evaluated as follows.
A: The unfixed portion of the second laminate did not lift off from the fixing surface, and the release liner could be easily peeled off.
B: The unfixed portion of the second laminate was slightly lifted from the fixed surface, but the release liner could be peeled off.
C: The portion of the second laminate that was not fixed as described above rose from the fixing surface, making it difficult to peel off the release liner.

The evaluation results for the release strength and ease of peeling for each release liner are shown in Table 1 below.

The adhesive sheet obtained by the manufacturing method of the present invention can be used, for example, in optical laminates and image display devices.

Reference Signs List 1: Adhesive sheet 2, 2A, 2B: Optical film 10: (First) laminate 11: Substrate sheet 12: Coating layer 13: Release liner 131: Liner substrate 132: Release layer 14: Light 18: Exposed surfaces 21, 22: Optical film with adhesive sheet

Claims (10)

A step A of irradiating a laminate including a base sheet, a coating layer including a photocurable composition, and the release liner in this order with light using a release liner to form a pressure-sensitive adhesive sheet from the coating layer;
and step B of peeling the release liner from the pressure-sensitive adhesive sheet,
The steps A and B are repeatedly performed using the release liner peeled off in the step B,
As the release liner, a sheet is used which has a peel strength _PS3 with respect to the adhesive sheet of less than 1.0 N/50 mm as measured after being peeled from the adhesive sheet three times, counting from an unused state.
A method for manufacturing an adhesive sheet. The method for producing a pressure-sensitive adhesive sheet according to claim 1 , wherein the release liner has a peel strength PS ₀ between the release liner and the pressure-sensitive adhesive sheet measured in an unused state of 0.01 N/50 mm or more. The method for producing a pressure-sensitive adhesive sheet according to claim 1 , wherein the release liner has a ratio PS ₃ /PS ₀ of the peel strength PS ₃ to the peel strength PS 0 between the release liner and the pressure-sensitive adhesive sheet measured in an unused state, that is, PS 3 /PS _0, of 10 or less. 2. The method for producing an adhesive sheet according to claim 1, wherein the release liner has a peel strength _PS1 / _PS0 ratio of the peel strength _PS1 measured after being peeled from the adhesive sheet once counting from the unused state to the peel strength _PS0 measured in an unused state, of 10 or less. the release liner has a release layer on the surface of the coating layer;
The method for producing a pressure-sensitive adhesive sheet according to claim 1 , wherein the release layer has a thickness of 110 nm or less. The method for producing an adhesive sheet according to claim 1, wherein the peel strength between the release liner and the adhesive sheet is smaller than the peel strength between the base sheet and the adhesive sheet. The method for producing a pressure-sensitive adhesive sheet according to claim 1, wherein the photocurable composition contains a monomer group including a (meth)acrylic monomer and/or a partial polymer of the monomer group. The method for producing a pressure-sensitive adhesive sheet according to claim 7, wherein the (meth)acrylic monomer includes a carboxyl group-containing monomer. A method for producing an optical film with a pressure-sensitive adhesive sheet, comprising forming an optical film with a pressure-sensitive adhesive sheet by disposing an optical film on the exposed surface of the pressure-sensitive adhesive sheet formed by the manufacturing method according to any one of claims 1 to 8. The method for producing an optical film with a pressure-sensitive adhesive sheet according to claim 9, wherein the optical film includes at least one film selected from the group consisting of a polarizing film and a retardation film.

Images