JP7285641B2 - Adhesive sheet with release film and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive sheet to which a release film is temporarily attached and a method for producing the same.

2. Description of the Related Art In display devices such as liquid crystal displays and organic EL displays and input devices for displays such as touch panels, substrate-less transparent adhesive sheets are used for bonding optical members. A substrate-less transparent pressure-sensitive adhesive sheet is generally provided as a pressure-sensitive adhesive sheet with a release film having release films attached on both sides. When using the adhesive sheet, first, one release film (light release film) is peeled off to expose one surface of the adhesive sheet, which is then attached to the first adherend, and then the other release film is exposed. The (heavy release film) is peeled off, and the second adherend is attached to the other surface of the pressure-sensitive adhesive sheet.

As a method for producing a substrate-less pressure-sensitive adhesive sheet, a method has been proposed in which a release film is coated with a photocurable pressure-sensitive adhesive composition in layers, and photocuring is performed by irradiating actinic rays such as ultraviolet rays. . As the release film, a release layer formed on the surface of a film substrate with a silicone-based release agent is widely used (see, for example, Patent Document 1).

JP 2015-151473 A

When peeling the release film from the adhesive sheet, the peeling is often performed at high speed from the viewpoint of work efficiency. As described in Patent Document 1, when the adhesive is photocured on a release film having a silicone-based release layer, the release film tends to be difficult to separate from the adhesive sheet. If a large force is applied when peeling the release film from the adhesive sheet, deformation (zipping) of the adhesive sheet is likely to occur. Therefore, when the peeling force (peel strength) during high-speed peeling is large, the peeling speed must be reduced in order to prevent deformation of the pressure-sensitive adhesive sheet, resulting in reduced workability.

On the other hand, when the peeling force at high-speed peeling is small, the shear force tends to be small. When conveying an adhesive sheet with a release film on a roll or when winding an adhesive sheet with a release film into a roll, the adhesive sheet is curved, so shear strain is generated at the bonding interface between the adhesive sheet and the release film. occurs. Also, when cutting the adhesive sheet into a predetermined shape, a shearing force is generated at the bonding interface. If the shear force of the release film is small, the shear force during handling or processing may cause the release film to separate from the pressure-sensitive adhesive sheet or air bubbles to enter the interface.

In view of the above, an object of the present invention is to provide a pressure-sensitive adhesive sheet with a release film that is resistant to peeling of the release film due to shearing and that is excellent in high-speed peelability of the release film.

The pressure-sensitive adhesive sheet with a release film of the present invention comprises a photocurable pressure-sensitive adhesive sheet having a first main surface and a second main surface, and a first release film temporarily attached to the first main surface of the pressure-sensitive adhesive sheet. . The first release film has a release layer on the film substrate, and the release layer and the adhesive sheet are in contact with each other. The adhesive sheet contains a photocurable acrylic polymer. The pressure-sensitive adhesive sheet with a release film may have a second release film temporarily attached to the second main surface of the pressure-sensitive adhesive sheet.

A pressure-sensitive adhesive sheet with a release film is obtained by irradiating the photocurable pressure-sensitive adhesive composition with light while the layered photocurable pressure-sensitive adhesive composition is in contact with the release layer of the first release film. is obtained. A photocurable pressure-sensitive adhesive composition contains an acrylic material and a photopolymerization initiator. Examples of the acrylic material contained in the photocurable pressure-sensitive adhesive composition include acrylic monomers and partial polymers thereof. The acrylic material may contain both acrylic monomers and partially polymerized acrylic monomers.

The release layer of the first release film is a cured resin layer (silicone release layer) of a silicone resin composition containing a polyorganosiloxane resin having a vinyl group and a polyorganosiloxane resin having a hexenyl group. The silicone-based resin composition used for forming the silicone-based release layer is polyorganosiloxane having a vinyl group with respect to a total of 100 parts by weight of the polyorganosiloxane resin having a vinyl group and the polyorganosiloxane resin having a hexenyl group. It preferably contains 20 to 80 parts by weight of resin.

The 180° peel strength when peeling the first release film from the adhesive sheet at a peel speed of 10 m/min is preferably 0.05 to 0.3 N/50 mm.

In the pressure-sensitive adhesive sheet with a release film of the present invention, since the pressure-sensitive adhesive sheet and the release film have appropriate adhesion, the release film is less likely to peel off during storage, transportation, transportation, etc. When the release film is peeled off at high speed, the peeling is easy and the workability is excellent.

FIG. 3 is a cross-sectional view showing a laminated structure of a pressure-sensitive adhesive sheet with a release film. FIG. 3 is a longitudinal cross-sectional view of a test piece used for measuring shear force.

The pressure-sensitive adhesive sheet with a release film of the present invention includes a release film temporarily attached to at least one surface of the pressure-sensitive adhesive sheet. “Temporarily attached” means a state of being releasably attached. The pressure-sensitive adhesive sheet with a release film may have release films temporarily attached to both sides of the pressure-sensitive adhesive sheet.

FIG. 1 is a cross-sectional view of a release film-attached pressure-sensitive adhesive sheet 1 in which release films 10 and 20 are temporarily attached to both surfaces of a pressure-sensitive adhesive sheet 50 . The adhesive sheet 50 is formed by forming an adhesive into a sheet. The total light transmittance of the adhesive sheet 50 is preferably 85% or more, more preferably 90% or more. The haze of the adhesive sheet is preferably 2% or less, more preferably 1% or less. The total light transmittance and haze are measured using a haze meter according to JIS K7136.

The adhesive sheet 50 is an acrylic adhesive containing a photocurable acrylic polymer. The acrylic pressure-sensitive adhesive sheet is obtained by applying a photocurable pressure-sensitive adhesive composition containing acrylic monomers and/or acrylic polymer partial polymers (prepolymers) and photopolymerization initiators in layers, followed by photocuring. It consists of a photo-curing adhesive. As used herein, the term “photocurable” pressure-sensitive adhesive refers to a pressure-sensitive adhesive that contains a photopolymerizable functional group-containing compound such as a vinyl group or a (meth)acryloyl group and can be photo-cured. A "photocured" adhesive refers to an adhesive after photocuring the photocurable adhesive. In addition, in the adhesive after polymerization of the photocurable adhesive, if part of the photopolymerizable compound remains unreacted, the adhesive is photocured and photocurable ( photocurable).

[Photocurable adhesive composition]
The photocurable pressure-sensitive adhesive composition contains a photopolymerizable acrylic material and a photopolymerization initiator.

<Photopolymerizable acrylic material>
Examples of the photopolymerizable acrylic material contained in the photocurable pressure-sensitive adhesive composition include acrylic monomers and partial polymers thereof (prepolymers).

(monomer component)
As acrylic monomers, (meth)acrylic acid alkyl esters in which the alkyl group has 1 to 20 carbon atoms are preferably used. The (meth)acrylic acid alkyl ester may have a branched alkyl group. The content of the (meth)acrylic acid alkyl ester is preferably 40% by weight or more, more preferably 50% by weight or more, and even more preferably 60% by weight or more, relative to the total amount of the monomer components of the acrylic material.

In addition to the (meth)acrylic acid alkyl ester, a highly polar monomer such as a hydroxyl group-containing monomer or a nitrogen-containing monomer may be contained as a copolymerization component. By containing a highly polar monomer unit in the acrylic polymer, the cohesive force of the adhesive is improved, the adhesion of the adhesive sheet to the adherend is enhanced, and cloudiness of the adhesive is suppressed in high-temperature and high-humidity environments. and the transparency of the pressure-sensitive adhesive sheet tends to be improved.

Examples of hydroxy group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, (meth) 8-hydroxyoctyl acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)-methyl acrylate and the like. The content of the hydroxy group-containing monomer is preferably 1 to 40% by weight, more preferably 3 to 30% by weight, even more preferably 5 to 20% by weight, based on the total amount of the monomer components.

Nitrogen-containing monomers include N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, (meth)acryloylmorpholine, N-vinyl Vinyl monomers such as carboxylic acid amides and N-vinylcaprolactam, and cyanoacrylate monomers such as acrylonitrile and methacrylonitrile can be used. The nitrogen-containing monomer preferably has a cyclic structure containing a nitrogen atom, and among these, a lactam vinyl monomer such as N-vinylpyrrolidone is preferred. The content of the nitrogen-containing monomer is preferably 0.5 to 50% by weight, more preferably 1 to 40% by weight, even more preferably 3 to 30% by weight, based on the total amount of the monomer components.

As a copolymerizable monomer component, monomers other than those described above, such as carboxyl group-containing monomers, cyclic ether group-containing monomers, and silane-based monomers, may be included.

The copolymerizable monomer component may contain a polyfunctional polymerizable compound having two or more polymerizable functional groups in one molecule. Examples of polyfunctional polymerizable compounds include compounds having two or more C=C bonds in one molecule, and compounds having one C=C bond and a polymerizable functional group such as epoxy, aziridine, oxazoline, hydrazine, and methylol. and compounds having Among them, polyfunctional polymerizable compounds having two or more C=C bonds in one molecule are preferred. The polyfunctional polymerizable compound may exist in the pressure-sensitive adhesive composition as a monomer or oligomer, and may bond with functional groups such as hydroxy groups of the prepolymer component.

Examples of polyfunctional polymerizable compounds having two or more C=C bonds in one molecule 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, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate and other polyfunctional (meth)acrylates (polyhydric alcohol and (meth)acrylic acid ester compound); allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl di(meth)acrylate, hexyl di(meth)acrylate, and the like. Among these, polyfunctional (meth)acrylates are preferred, and polyfunctional acrylates are particularly preferred because of their high photopolymerizability.

The amount of the polyfunctional monomer used varies depending on its molecular weight, the number of functional groups, etc., but is preferably 5% by weight or less, more preferably 3% by weight or less, and even more preferably 2% by weight or less, relative to the total amount of the monomer components. The amount of polyfunctional monomer used can be 0.001 parts by weight or more, 0.01 parts by weight or more, or 0.05 parts by weight or more based on the total amount of the monomer components.

In the photocurable pressure-sensitive adhesive composition, the above monomer component may exist as a partial polymer (prepolymer). A prepolymer is a product obtained by partially polymerizing a monomer component. Presence of the monomer component as a prepolymer allows the viscosity of the photocurable pressure-sensitive adhesive composition to be adjusted within a range suitable for application onto a support.

A prepolymer can be prepared, for example, by partially polymerizing a composition for forming a prepolymer in which a monomer component and a polymerization initiator are mixed. The prepolymer-forming composition may contain all the monomer components constituting the acrylic polymer, or may contain only a part of the monomers constituting the acrylic polymer. When the monomer component constituting the acrylic polymer contains a monofunctional monomer and a polyfunctional monomer, the pressure-sensitive adhesive composition is prepared by adding the polyfunctional monomer to a prepolymer composition obtained by partially polymerizing only the monofunctional monomer. may By adding a polyfunctional monomer to a prepolymer composition obtained by partially polymerizing only a monofunctional monomer and performing post-polymerization, cross-linking points by the polyfunctional monomer can be uniformly introduced into the polymer. A part of the polyfunctional monomer component constituting the acrylic polymer may be contained in the prepolymer-forming composition, and after the prepolymer is polymerized, the remainder of the polyfunctional monomer component may be added for post-polymerization.

Prepolymers may be prepared in two or more or three or more stages of polymerization. For example, after prepolymerizing only a monofunctional monomer, a polyfunctional monomer may be added for partial polymerization to prepare a prepolymer composition, and if necessary, a monomer component or the like may be further added for postpolymerization. good.

The prepolymer polymerization method is not particularly limited. Photopolymerization by irradiation with actinic rays such as ultraviolet rays is preferable from the viewpoint of adjusting the reaction time to set the molecular weight (polymerization rate) of the prepolymer within a desired range. When photopolymerization is performed, the prepolymer-forming composition preferably contains a photopolymerization initiator.

The photopolymerization initiator is not particularly limited as long as it initiates photoradical polymerization. Sulfonyl chloride photoinitiator, photoactive oxime photoinitiator, benzoin photoinitiator, benzyl photoinitiator, benzophenone photoinitiator, ketal photoinitiator, thioxanthone photoinitiator agent, acylphosphine oxide-based photopolymerization initiator, and the like can be used.

The prepolymer-forming composition may contain a chain transfer agent and the like, if necessary, in addition to the monomer components and the polymerization initiator. The chain transfer agent receives radicals from the growing polymer chain to terminate the elongation of the polymer, and the chain transfer agent that receives the radicals attacks the monomers to initiate polymerization again. By using a chain transfer agent, excessive increase in molecular weight can be suppressed without lowering the radical concentration in the reaction system. Preferred chain transfer agents include thiols such as α-thioglycerol, lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol. used for

Although the polymerization rate of the prepolymer is not particularly limited, it is preferably 3 to 50%, more preferably 5 to 40%, from the viewpoint of obtaining a viscosity suitable for coating on the support. The degree of polymerization of the prepolymer can be adjusted within a desired range by adjusting the type and amount of the photopolymerization initiator used, and the irradiation intensity and irradiation time of actinic rays such as ultraviolet rays. The polymerization rate is calculated by the following formula from the weights before and after heating (drying) when the prepolymer composition is heated at 130° C. for 3 hours. When partial polymerization is performed by solution polymerization, the polymerization rate is calculated by using the total weight of the prepolymer composition minus the amount of the solvent as the weight before heating in the following formula.
Polymer polymerization rate (%) = 100 x (weight after heating/weight before heating)

<Preparation of photocurable pressure-sensitive adhesive composition>
A photocurable pressure-sensitive adhesive composition can be obtained by mixing the above photopolymerizable acrylic material (monomer and/or partial polymer thereof) with the remaining monomer components, a photopolymerization initiator, and other additives. be done. The photocurable pressure-sensitive adhesive composition preferably contains a polyfunctional monomer as the remaining monomer component. As the polyfunctional monomer, a polyfunctional polymerizable compound having two or more C=C bonds in one molecule as exemplified above is preferably used.

The photopolymerization agent is not particularly limited, and for example, the photopolymerization initiators described above can be used. The content of the photopolymerization initiator in the photocurable pressure-sensitive adhesive composition is preferably 0.02 to 10 parts by weight with respect to a total of 100 parts by weight of the monomer component and prepolymer component that constitute the acrylic polymer. 0.05 to 5 parts by weight is more preferred. When the photopolymerization initiator in the prepolymer-forming composition remains uninactivated in the prepolymer composition, the addition of the photopolymerization initiator may be omitted.

A chain transfer agent may be contained in the photocurable pressure-sensitive adhesive composition. The chain transfer agent contained in the photocurable pressure-sensitive adhesive composition is not particularly limited, and for example, the chain transfer agent described above can be used. The pressure-sensitive adhesive composition may contain a silane coupling agent, a cross-linking agent, a tackifier, a plasticizer, a softening agent, and the like for the purpose of adjusting adhesive strength and the like. In addition, the pressure-sensitive adhesive composition may contain additives such as deterioration inhibitors, fillers, colorants, antioxidants, surfactants, and antistatic agents to the extent that the properties of the pressure-sensitive adhesive are not impaired.

The photocurable pressure-sensitive adhesive composition preferably has a viscosity suitable for coating on a support (for example, about 5 to 100 poise). The viscosity of the pressure-sensitive adhesive composition can be adjusted, for example, by adding various polymers such as thickening additives, polyfunctional monomers, and the like, and the polymerization rate of prepolymers. In the photocurable pressure-sensitive adhesive composition, the content of acrylic monomer components (acrylic monomers and partially polymerized acrylic monomers) is preferably 50% by weight or more, more preferably 70% by weight or more. It is preferably 80% by weight or more, and more preferably 80% by weight or more.

[Release film]
A pressure-sensitive adhesive sheet can be obtained by applying the above photocurable pressure-sensitive adhesive composition onto a support and subjecting it to photocuring. Since photoradical polymerization is inhibited by oxygen in the air, a cover sheet is provided on the coating layer of the photocurable pressure-sensitive adhesive composition before photocuring, and a photocurable adhesive composition is formed between the support and the coversheet. It is preferable to block oxygen by forming a laminate in which the pressure-sensitive adhesive composition is provided in layers. Lamination in which a photocurable pressure-sensitive adhesive composition is applied in layers between two sheets (a support and a cover sheet), and the photocurable pressure-sensitive adhesive composition is provided in layers between the support and the cover sheet You can form a body.

At least one of the support for applying the pressure-sensitive adhesive composition and the cover sheet attached to the surface of the pressure-sensitive adhesive composition-coated layer has a mold release on the contact surface with the pressure-sensitive adhesive composition-coated layer (adhesive sheet). A release film comprising a layer. In a laminate in which a photocurable pressure-sensitive adhesive composition is provided in layers between a support and a cover sheet, both the support and the cover sheet are preferably release films.

<Film substrate>
As the film substrates 11 and 21 of the release films 10 and 20, various transparent resin films are used. Examples of resin materials include polyester-based resins such as polyethylene terephthalate and polyethylene naphthalate, acetate-based resins, polyethersulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, (meth)acrylic-based resins, Polyvinyl chloride-based resins, polyvinylidene chloride-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, polyarylate-based resins, polyphenylene sulfide-based resins, and the like are included. Among these, polyester resins such as polyethylene terephthalate are particularly preferred. The thickness of the film substrates 11 and 21 is preferably 10-200 μm, more preferably 25-150 μm.

<Release layer>
Materials for the release layer include silicone-based release agents, fluorine-based release agents, long-chain alkyl-based release agents, and fatty acid amide-based release agents. The release layer 15 of the release film 10 is a silicone-based release layer formed by curing a curable silicone-based resin composition.

A silicone-based resin composition that cures through an addition reaction is used to form the silicone-based release layer 15 . A silicone-based resin composition that cures by an addition reaction contains a polyorganosiloxane resin having an addition-reactive functional group and a polyorganosiloxane compound (crosslinking agent) having a hydrosilyl group (SiH), and further contains a curing catalyst. (hydrosilylation catalyst) is preferably included. When this silicone-based resin composition is heated, the reaction (hydrosilylation reaction) between the addition-reactive groups of the polyorganosiloxane resin and the hydrosilyl groups of the cross-linking agent forms a release film (release layer).

Addition-reactive functional groups include alkenyl groups. Examples of alkenyl groups include vinyl, allyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, and dodecenyl groups. A mixture of a polyorganosiloxane resin having a vinyl group and a polyorganosiloxane resin having a hexenyl group is used to form the silicone release layer 15 .

Examples of polyorganosiloxane include polydimethylsiloxane, polydiethylsiloxane, polyalkylalkylsiloxane such as polymethylethylsiloxane; polyalkylarylsiloxane; poly(dimethylsiloxane-diethylsiloxane). The polyorganosiloxane may be one in which a plurality of types of organic groups are bonded to Si groups.

The cross-linking agent is a polyorganosiloxane having hydrosilyl groups, preferably having two or more silicon atoms having Si—H bonds in one molecule. As the polyorganosiloxane having a hydrosilyl group, polymethylhydrogensiloxane, poly(dimethylsiloxane-methylhydrogensiloxane), hydrosilyl group-terminated polydimethylsiloxane, and the like are preferable.

As the silicone-based resin composition, a commercially available product in which a polyorganosiloxane resin having an addition-reactive functional group and a polyorganosiloxane compound having a hydrosilyl group are mixed in advance may be used. Commercially available products containing a polyorganosiloxane resin having a vinyl group and a polyorganosiloxane compound having a hydrosilyl group include "KS-847" and "X-62-2829" manufactured by Shin-Etsu Chemical Co., Ltd., and Dow Corning Toray Co., Ltd. "SRX211" and the like. Commercially available products containing a polyorganosiloxane resin having a hexenyl group and a polyorganosiloxane compound having a hydrosilyl group include "LTC761" and "LTC300B" manufactured by Dow Corning Toray.

The content of the polyorganosiloxane resin having a vinyl group is preferably 20 to 80 parts by weight, preferably 30 to 70 parts by weight, with respect to a total of 100 parts by weight of the polyorganosiloxane resin having a vinyl group and the polyorganosiloxane resin having a hexenyl group. is more preferred. By setting the ratio of both in this range, it is possible to obtain a pressure-sensitive adhesive sheet with a release film having a large shearing force of the release film and a small peel strength during high-speed peeling.

A platinum-based catalyst is preferable as the curing catalyst for the silicone-based resin composition. Examples of platinum-based catalysts include chloroplatinic acid, olefin complexes of platinum, and olefin complexes of chloroplatinic acid. The amount of the platinum-based catalyst used (in terms of platinum) is preferably about 10 to 1000 ppm with respect to the total amount of the polyorganosiloxane resin having an addition-reactive functional group and the polyorganosiloxane compound having a hydrosilyl group.

The silicone-based resin composition may contain a reaction inhibitor (hydrosilylation inhibitor) for the purpose of improving storage stability after addition of the catalyst. Examples of reaction inhibitors include 3,5-dimethyl-1-hexyn-3-ol, 3-methyl-1-penten-3-ol, 3-methyl-3-penten-1-yne, 3,5-dimethyl- 3-hexene-1-yne and the like.

The silicone resin composition may contain an organic solvent. Examples of organic solvents include 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. alcoholic solvents such as methanol, ethanol and butanol; The organic solvent may be a mixed solvent. The amount of the organic solvent used is preferably about 80 to 99.9% by mass in the silicone resin composition.

The silicone-based resin composition may contain a polyorganosiloxane resin having no reactive functional group (for example, trimethylsiloxy-terminated polydimethylsiloxane, etc.). However, when the amount of polyorganosiloxane resin that does not have a reactive functional group added increases, the shearing force between the release film and the adhesive sheet decreases, and when the adhesive sheet with the release film is conveyed by rolls, Undesirable peeling may occur when the pressure-sensitive adhesive sheet with a film is wound into a roll. Therefore, the amount of the polyorganosiloxane resin that does not have a reactive functional group is 2 parts by weight with respect to the total of 100 parts by weight of the polyorganosiloxane resin that has an addition reaction functional group and the polyorganosiloxane compound that has a hydrosilyl group. Part or less is preferable, 1 part by weight or less is more preferable, and 0.5 part by weight or less is even more preferable.

The silicone-based resin composition may contain various additives such as fillers, antistatic agents, antioxidants, plasticizers and colorants, if necessary.

By applying the silicone-based resin composition onto the film substrate 11 and heating, the silicone-based resin composition is cured by a hydrosilylation reaction to form the silicone-based release layer 15 . Coating methods include 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. Hot-air drying is mentioned as a heat-drying method. The hot-air drying conditions vary depending on the heat resistance of the film substrate, but are usually about 80 to 150° C. for about 10 seconds to 10 minutes. If necessary, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination for the purpose of promoting the addition reaction of silicone.

The coating amount of the silicone-based resin composition may be adjusted so that the silicone resin amount is about 0.03 to 1 g/m ² . The thickness of the silicone release layer 15 is preferably, for example, about 10 to 500 nm.

[Formation of Adhesive Sheet]
A photocurable pressure-sensitive adhesive composition is applied onto a support, or a pressure-sensitive adhesive composition layer is formed between a support and a cover sheet, and the pressure-sensitive adhesive composition is irradiated with active energy rays for photocuring. An adhesive sheet is obtained by carrying out. The adhesive composition can be applied by 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. is mentioned. The coating thickness of the photocurable adhesive composition (the thickness of the adhesive sheet 50) is not particularly limited, but is, for example, about 10 to 500 μm.

The wavelength and intensity of actinic rays for photocuring may be appropriately determined according to the composition, thickness, etc. of the pressure-sensitive adhesive. The light source for light irradiation is not particularly limited as long as it can irradiate light in the wavelength range to which the photopolymerization initiator contained in the pressure-sensitive adhesive composition is sensitive. Lamps, metal halide lamps, xenon lamps and the like are preferably used.

From the viewpoint of improving the curing speed, the light irradiation intensity is preferably 5 mW/cm ² or more. The light irradiation intensity is preferably 20 mW/cm ² or less from the viewpoint of sufficiently increasing the molecular weight of the acrylic polymer after photocuring and ensuring the holding power at high temperatures. The integrated light quantity of the irradiation light is preferably about 100 to 5000 mJ/cm ² .

The final polymerization rate of the monomer component in the adhesive sheet after photocuring is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. The gel fraction of the pressure-sensitive adhesive sheet is preferably 50% or higher, more preferably 75% or higher, even more preferably 85% or higher.

[Peelability of Release Film and Adhesive Sheet]
Photocuring of the adhesive composition is performed while the photocurable adhesive composition is in contact with the release layer 15 of the release film 10 . If an unreacted alkenyl group (C=C bond) remains in the silicone release agent, the remaining C=C bond in the release layer undergoes radical polymerization when the photocurable pressure-sensitive adhesive composition is photocured. Since it participates in the reaction, a chemical bond is formed between the silicone resin of the release layer and the adhesive, and there is a tendency for the release film to be peeled off from the adhesive sheet more slowly (peel strength and shear force increase).

If the peel strength is excessively high, problems such as deformation of the adhesive sheet are likely to occur when the release film is peeled from the adhesive sheet at high speed. From the viewpoint of facilitating high-speed peeling of the release film from the adhesive sheet, the peel strength when peeling the release film 10 from the adhesive sheet 50 180° at a peeling speed of 10 m / min is 0.3 N / 50 mm or less. It is preferably 0.25 N/50 mm or less, more preferably 0.23 N/50 mm or less. On the other hand, from the viewpoint of ensuring the adhesion between the adhesive sheet 50 and the release film 10, the peel strength is preferably 0.05 N/50 mm or more, more preferably 0.1 N/50 mm or more. The 180° peel strength at a peel speed of 0.3 m/min is also preferably within the above range.

From the viewpoint of suppressing peeling of the release film due to shear force during processing such as cutting when the pressure-sensitive adhesive sheet with release film is curved, the contact area with the pressure-sensitive adhesive sheet: Measured using a sample of 20 mm × 20 mm. The shearing force of the released film is preferably 20 N or more, more preferably 25 N or more.

In the adhesive sheet with a release film of the present invention, the release layer 15 of the release film 10 is a cured resin of a silicone-based resin composition containing a polyorganosiloxane resin having a vinyl group and a polyorganosiloxane resin having a hexenyl group. Since it is a layer, the peel strength at high speed peeling is small and the shear force is large. Therefore, it is difficult to peel off the release film during storage, transport, transportation, cutting, etc., and it is easy to peel off at high speed when peeling off the release film to bond the adhesive sheet to the adherend. and excellent workability.

The higher the ratio of the polyorganosiloxane resin having a vinyl group in the silicone-based resin composition, the higher the peel strength (high-speed peel strength) and shear force in a 180° peel test at a peel speed of 10 m/min. High-speed peel strength and shear strength tend to decrease as the ratio of polyorganosiloxane resin having hexenyl groups in the silicone resin composition increases.

One of the reasons why the ratio of the vinyl group-containing component and the hexenyl group-containing component affects the release force between the release film and the photocurable pressure-sensitive adhesive sheet is the formation of the silicone release layer (curing of the silicone resin composition). It is conceivable that the vinyl group tends to remain unreacted during the process. In polyorganosiloxane resins having vinyl groups, carbon atoms bonded to Si atoms of polyorganosiloxane form addition reactive groups (C═C bonds). Therefore, the C=C bond of the vinyl group tends to be embedded in the resin matrix of the polyorganosiloxane. On the other hand, in the polyorganosiloxane resin having a hexenyl group, since four carbon atoms are interposed between the Si atom of the polyorganosiloxane and the carbon atoms forming the C=C bond, the hexenyl group The C═C bond is farther from the resin matrix of the polyorganosiloxane.

When curing a silicone-based resin composition, vinyl groups that are likely to be embedded in the resin matrix of polyorganosiloxane have relatively low reactivity, and hexenyl groups that have a large distance between Si atoms and C=C bonds are relatively is considered to be highly reactive to Therefore, the higher the ratio of the polyorganosiloxane resin having a hexenyl group, the smaller the amount of residual C=C bonds in the silicone-based release layer, and the higher the ratio of the polyorganosiloxane resin having a vinyl group, the higher the silicone-based release layer. It is believed that the amount of residual C=C bonds in the layer increases. Therefore, by using both a polyorganosiloxane resin having a vinyl group and a polyorganosiloxane resin having a hexenyl group and adjusting the ratio thereof, the amount of residual C=C bonds in the silicone-based release layer (photocurable It is thought that the density of reaction points with the monomer in the PSA composition can be appropriately adjusted, and the release force between the PSA sheet and the release film after photocuring can be adjusted within an appropriate range.

In a pressure-sensitive adhesive sheet with a release film in which a release film is temporarily attached to both sides of the pressure-sensitive adhesive sheet, the peel strength when peeling one release film from the pressure-sensitive adhesive sheet is generally sufficient to peel off the other release film from the pressure-sensitive adhesive sheet. It is relatively small compared to the peel strength at the time of peeling. When using an adhesive sheet, after peeling off the relatively low peel strength release film (light release film) from the adhesive sheet and bonding it to the first adherend, the relatively high peel strength The release film (heavy release film) is peeled off, and the adherend is laminated to the second adherend. By providing a difference in peel strength between the release films that are temporarily attached to the front and back of the adhesive sheet, the light release film can be selectively peeled off when the adhesive sheet is attached to the first adherend. You can enhance your sexuality.

As shown in FIG. 1, when release films are temporarily attached to both sides of the pressure-sensitive adhesive sheet 50, the release film 10 including the release layer 15 formed by curing the above-described silicone-based resin composition is light. Either a release film or a heavy release film may be used. The configuration of the release layer 25 of the other release film 20 is not particularly limited. In addition to the release layer 15, the release layer 25 may also be a cured resin layer of a silicone-based resin composition containing a polyorganosiloxane resin having a vinyl group and a polyorganosiloxane resin having a hexenyl group. For example, by changing the resin composition of the release layer 15 and the release layer 25 (ratio of polyorganosiloxane having a vinyl group and polyorganosiloxane having a hexenyl group), a release temporarily attached to the front and back of the adhesive sheet 50 The films 10 and 20 may have different peel strengths.

[Use of adhesive sheet]
The photocurable pressure-sensitive adhesive sheet described above has a high visible light transmittance, and is therefore suitably used as an optical pressure-sensitive adhesive for forming a display device. Examples of display devices include liquid crystal display devices, organic EL (electroluminescence) display devices, PDP (plasma display panels), electronic paper, and the like. Moreover, the photocurable adhesive sheet can also be used for laminating a display device and an input device such as a touch panel, or laminating a transparent plate arranged on the surface of the display device or the input device.

When using the release film-attached pressure-sensitive adhesive sheet to which the release films are temporarily attached on both sides, first, the light release film (first release film 10) is peeled off to expose the first main surface of the pressure-sensitive adhesive sheet 50, and then the second main surface is exposed. Bonding to one adherend is performed. After that, the heavy release film (second release film 20) is peeled off to expose the second main surface of the adhesive sheet 50, which is then attached to the second adherend. After peeling off the release films on both sides, bonding to the adherend may be performed. When the pressure-sensitive adhesive sheet has photocurability, the pressure-sensitive adhesive sheet after being attached to the adherend may be further irradiated with light. By further photocuring the pressure-sensitive adhesive sheet after bonding to the adherend, the reliability of adhesion to the adherend may sometimes be improved.

Examples and comparative examples are given below for further explanation, but the present invention is not limited to these examples.

[Preparation of photocurable adhesive composition]
2-ethylhexyl acrylate (2EHA): 78 parts by weight, N-vinyl-2-pyrrolidone (NVP): 18 parts by weight, and 2-hydroxyethyl acrylate (HEA): 4 parts by weight, As a photopolymerization initiator, 1-hydroxycyclohexylphenyl ketone (manufactured by BASF "Irgacure 184"): 0.035 parts by weight, and 2,2-dimethoxy-1,2-diphenylethan-1-one (manufactured by BASF "Irgacure 651 ”): 0.035 parts by weight was added. This composition was irradiated with ultraviolet rays and prepolymerized until the viscosity at room temperature reached about 20 Pa·s to obtain a prepolymer having a polymerization rate of about 8%.

100 parts by weight of the prepolymer, 0.15 parts by weight of hexanediol diacrylate (HDDA), 0.3 parts by weight of a silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd. "KBM-403"), and as a photopolymerization initiator, Bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (“Irgacure 819” manufactured by BASF): 0.15 parts by weight was added to obtain a photocurable acrylic adhesive composition.

[Comparative Example 1]
<Production of release film>
100 parts by weight of a 30% toluene solution of vinyl group-containing addition type silicone (“KS-847T” manufactured by Shin-Etsu Chemical Co., Ltd.) and 1 part by weight of a platinum catalyst for curing silicone (“CAT-PL-50T” manufactured by Shin-Etsu Chemical Co., Ltd.) A release agent solution was prepared by diluting with a mixed solvent of toluene and hexane at a ratio of 1:1 so that the silicone concentration was 0.7% by weight. This release agent solution is applied to one side of a 75 μm thick biaxially oriented polyester film (“Lumirror XD500P” manufactured by Toray Advanced Materials Korea) using a wire bar (#9), and dried with hot air at 130°C. It was heated in a machine for 1 minute to form a release layer.

<Production of adhesive sheet with release film>
In Comparative Example 1, the above release film was used for both the support release film and the cover release film. The pressure-sensitive adhesive composition was applied to the release layer forming surface of the support release film in a thickness of 150 μm to form a coating layer, and the cover release film was attached to the surface of the coating layer to obtain a laminate. This laminate is irradiated with ultraviolet rays from the release film side of the cover under the conditions of illuminance: 6.5 mW/cm ² and integrated light amount: 1500 mJ/cm ² to photocure the coating layer to form a photocurable pressure-sensitive adhesive layer. A pressure-sensitive adhesive sheet having release films on both sides was obtained.

[Comparative Example 2]
<Preparation of support release film>
30% toluene solution of hexenyl group-containing addition-type silicone (addition-type silicone release agent containing polyorganosiloxane having hexenyl group in the molecule and polyorganosiloxane cross-linking agent having hydrosilyl group in the molecule) (Toray Industries, Inc.) Dow Corning "LTC761"): 100 parts by weight, silicone dispersion (Toray Dow Corning "BY 24-850"): 3.0 parts by weight, and a platinum catalyst for silicone curing (Toray Dow Corning "SRX 212" ): 6.7 parts by weight was diluted with a mixed solvent of toluene and hexane at a volume ratio of 1:1 so that the silicone concentration was 0.7% by weight to prepare a release agent solution. This release agent solution is applied to one side of a 75 μm thick biaxially oriented polyester film (“Lumirror XD500P” manufactured by Toray Advanced Materials Korea) using a wire bar (#9), and dried with hot air at 130°C. It was heated in a machine for 1 minute to form a release layer.

<Production of adhesive sheet with release film>
The above release film was used as the support release film, and the same release film as the release film of Comparative Example 1 was used as the cover release film. Other than that, in the same manner as in Example 1, the adhesive composition was applied on the support release film, the cover release film was laminated, and the ultraviolet irradiation was performed. A pressure-sensitive adhesive sheet having

[Examples 1 to 4]
As a release agent solution for forming the release layer of the support release film, a vinyl group-containing addition type silicone solution (KS-847T) and a xenyl group-containing addition type silicone solution (LTC761) are shown in Table 1. They were mixed at the indicated ratio, and the amounts of the catalyst and the like used were adjusted according to the ratio of the two. A pressure-sensitive adhesive sheet having release films on both sides of the photocurable pressure-sensitive adhesive layer was obtained in the same manner as in Comparative Example 2, except that the composition of the release agent solution was changed.

[Peelability evaluation]
<Peel strength of release film>
Cut out the pressure-sensitive adhesive sheet with a release film to a width of 50 mm, and perform a 180 ° peel test at a tensile speed of 10 m / min (high speed) and 0.3 m / min (low speed) using a tensile tester in an environment of 23 ° C. Then, the peel strength was measured when the supporting release film was peeled from the pressure-sensitive adhesive sheet.

<Shear force>
Cut the pressure-sensitive adhesive sheet with a release film into a length of 200 mm × width of 20 mm, put the cover release film 20 side up, make a cut at a position of 90 mm from one end in the length direction, and cover the area of 90 mm from the one end The release film 20 and the adhesive layer 50 were removed. The sample is turned over, a cut 10x is made in the support release film 10 at a position 90 mm from the other end in the length direction, and one cut piece 10a of the support release film and the adhesive layer 50 are a 20 mm × 20 mm area. A test piece adhered with was produced (see FIG. 2). Both ends of the test piece were chucked at a distance between chucks of 100 mm, and a tensile test was performed at a tensile speed of 10 mm / min in an environment of 23 ° C. until the support release film 10a was completely peeled off from the adhesive layer 50. The maximum value of the test force was taken as the shear force.

[Evaluation results]
Table 1 shows the compositions of the release agent solutions used in the preparation of the support release films of Examples and Comparative Examples, and the evaluation results of the peelability of the support release films. All numerical values for the composition of the release agent in Table 1 are parts by weight.

In Comparative Example 1, in which the vinyl group-containing addition-type silicone was used as the material for forming the release layer, the peel strength during high-speed peeling was high, and the workability in peeling the release film from the adhesive sheet was poor. In Comparative Example 2, in which hexenyl group-containing addition-type silicone was used as the material for forming the release layer, the shear force was small, and when the pressure-sensitive adhesive sheet was bent, the shear strain at the interface between the pressure-sensitive adhesive sheet and the supporting release film resulted in Peeling occurred at the interface between the two. Examples 1 to 4, in which the vinyl group-containing addition-type silicone and the hexenyl group-containing addition-type silicone were used in combination, had a high-speed peeling force of 0.3 N/50 mm or less, exhibiting excellent high-speed peeling properties and exhibiting a sufficiently large shear force. .

1: PSA sheet with release film 10, 20: Release film 11, 21: Film substrate 15, 25: Release layer 5: Laminate 9: Test piece for measuring shear force

Claims (7)

A photocurable adhesive sheet having a first main surface and a second main surface ; a first release film temporarily attached to the first main surface of the adhesive sheet ; and a temporary release film attached to the second main surface of the adhesive sheet A release film-attached pressure-sensitive adhesive sheet comprising a second release film attached,
The first release film comprises a release layer on a film substrate,
The release layer and the adhesive sheet are in contact,
The adhesive sheet contains a photocurable acrylic polymer,
The release layer is a cured resin layer of a silicone-based resin composition containing a polyorganosiloxane resin having a vinyl group and a polyorganosiloxane resin having a hexenyl group ,
A pressure-sensitive adhesive sheet with a release film, wherein the peel strength of the first release film from the pressure-sensitive adhesive sheet is lower than the peel strength of the second release film from the pressure-sensitive adhesive sheet. The silicone-based resin composition contains 20 to 80 parts by weight of a polyorganosiloxane resin having a vinyl group with respect to a total of 100 parts by weight of a polyorganosiloxane resin having a vinyl group and a polyorganosiloxane resin having a hexenyl group. The pressure-sensitive adhesive sheet with a release film according to claim 1. According to claim 1 or 2, the peel strength when peeling the first release film from the adhesive sheet obtained by a 180° peel test at a peel speed of 10 m / min is 0.05 to 0.3 N / 50 mm. Adhesive sheet with release film described. The release film according to any one of claims 1 to 3 , wherein the photocurable acrylic polymer contains, as a copolymerizable monomer component, a polyfunctional monomer having two or more polymerizable functional groups in one molecule. Adhesive sheet with. A photocurable adhesive sheet having a first main surface and a second main surface; a first release film temporarily attached to the first main surface of the adhesive sheet; and temporarily attached to the second main surface of the adhesive sheet A pressure-sensitive adhesive sheet with a release film, wherein the peel strength of the first release film from the pressure-sensitive adhesive sheet is lower than the peel strength of the second release film from the pressure-sensitive adhesive sheet. A manufacturing method comprising:
A photocurable pressure-sensitive adhesive composition containing an acrylic monomer and/or a partially polymerized acrylic monomer and a photopolymerization initiator is provided as a layer between the first release film and the second release film. forming a laminated body; and irradiating the photocurable pressure-sensitive adhesive composition between the first release film and the second release film with light to remove the photocurable pressure-sensitive adhesive composition. Having a step of photocuring,
The first release film has a release layer on the surface of the film substrate that is in contact with the photocurable pressure-sensitive adhesive composition,
A method for producing a pressure-sensitive adhesive sheet with a release film, wherein the release layer is a cured resin layer of a silicone-based resin composition containing a polyorganosiloxane resin having a vinyl group and a polyorganosiloxane resin having a hexenyl group. The silicone-based resin composition contains 20 to 80 parts by weight of a polyorganosiloxane resin having a vinyl group with respect to a total of 100 parts by weight of a polyorganosiloxane resin having a vinyl group and a polyorganosiloxane resin having a hexenyl group. The method for producing a pressure-sensitive adhesive sheet with a release film according to claim 5 . The method for producing a release film-attached pressure-sensitive adhesive sheet according to claim 5 or 6 , wherein the photocurable pressure-sensitive adhesive composition contains a polyfunctional monomer having two or more polymerizable functional groups in one molecule.

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