CN111465668A - Adhesive sheet with release film and method for producing the same - Google Patents

Abstract

The present invention providesA release film-equipped adhesive sheet (1) comprising: a photocurable pressure-sensitive adhesive sheet (50) having a first main surface and a second main surface, and a first release film (10) temporarily attached to the first main surface of the pressure-sensitive adhesive sheet, wherein the first release film comprises a release layer (15) on a film base (11), the release layer (15) is in contact with the pressure-sensitive adhesive sheet (50), the pressure-sensitive adhesive sheet (50) contains a photocurable acrylic polymer and an ultraviolet absorber, the release layer (15) is a silicone-based release layer, and the content of Si atoms is 0.02 to 0.07g/m²。

Description

Adhesive sheet with release film and method for producing the same

technical field

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

Background technique

A transparent pressure-sensitive adhesive sheet is used when bonding optical members to display devices such as liquid crystal displays and organic EL displays, and input devices for displays such as touch panels. The transparent pressure-sensitive adhesive sheet is usually provided as a release-film-attached pressure-sensitive adhesive sheet on both sides. When using a pressure-sensitive adhesive sheet, first, one release film (light release film) is peeled off to expose one side of the pressure-sensitive adhesive sheet, and the first adherend is bonded, and the other release film (heavy release film) is peeled off. ) peeled off, and the second adherend was attached to the other side of the adhesive sheet.

From the viewpoint of suppressing deterioration of elements due to ultraviolet rays, and the like, ultraviolet light blocking properties are sometimes required for optical members used in display devices, input devices, and the like. For example, in an organic EL display, deterioration of organic molecules constituting a light-emitting layer and the like due to ultraviolet rays has a large influence on display characteristics, and therefore, high ultraviolet blocking properties are required for optical members arranged on the front surface of the element. In addition, for polarizers used in liquid crystal displays and organic EL displays, in order to prevent deterioration of the polarizer (for example, discoloration of iodine) caused by ultraviolet rays, an optical member arranged on the front surface of the polarizer is required. UV blocking properties.

As a method of imparting ultraviolet blocking properties to an adhesive sheet, a method of adding an ultraviolet absorber to an adhesive composition is known. For example, Patent Document 1 describes that an adhesive composition obtained by adding an ultraviolet absorber to a thermally polymerizable acrylic pressure-sensitive adhesive solution is coated in a film form, and then heated and dried to obtain an adhesive composition having ultraviolet light. Barrier adhesive sheet. Patent Document 2 describes that a photocurable acrylic pressure-sensitive adhesive composition containing a photocurable acrylic composition, a photopolymerization initiator, and an ultraviolet absorber is applied in a layer on a release film substrate , another release film was laminated thereon to block contact with the air, and photocuring was performed in this state, thereby obtaining a photocurable adhesive sheet having ultraviolet barrier properties.

prior art literature

Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 2013-75978

Patent Document 2: Japanese Patent Laid-Open No. 2016-155981

SUMMARY OF THE INVENTION

The problem to be solved by the invention

If a photocurable pressure-sensitive adhesive is used as described in Patent Document 2, since a solvent is not required at the time of forming the pressure-sensitive adhesive sheet, it is easy to increase the thickness of the pressure-sensitive adhesive sheet. In addition, there is an advantage that the smoothness of the adhesive sheet can be improved by photocuring in a state where the release sheet is in contact with both surfaces of the sheet-like photocurable adhesive composition.

However, according to the study of the present inventors, when the photocurable adhesive composition containing an ultraviolet absorber is irradiated with ultraviolet rays through a mold release film to be photocured, the mold release film on the light-irradiated surface and the adhesive after photocuring are found. The peeling force of the bonding sheet is greatly increased, and it may be difficult to peel off the mold release film when it is bonded to an adherend. In view of this problem, an object of the present invention is to provide a release film-attached pressure-sensitive adhesive sheet which has ultraviolet barrier properties and has good releasability from a release film.

way of solving the problem

The pressure-sensitive adhesive sheet with a release film of the present invention includes 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 is provided with a release layer on the film base material, and the release layer is in contact with the adhesive sheet, and the adhesive sheet includes a photocurable acrylic polymer and an ultraviolet absorber. The pressure-sensitive adhesive sheet with a release film may include a second release film temporarily attached to the second main surface of the pressure-sensitive adhesive sheet.

The first main surface of the pressure-sensitive adhesive sheet is a light-irradiated surface at the time of photocuring the photocurable pressure-sensitive adhesive composition. That is, a photocurable adhesive sheet is formed by irradiating the photocurable adhesive composition with light through the first release film. As the first release film attached to the light-irradiated surface side of the photocurable adhesive composition, by using a release film provided with a predetermined silicone-based release layer, even if the adhesive contains ultraviolet rays In the case of an absorbent, an excessive increase in peeling force can also be suppressed. The Si atom content of the silicone-based mold release layer of the first mold release film is preferably 0.02 to 0.07 g/m ² .

The light transmittance of the pressure-sensitive adhesive sheet at a wavelength of 380 nm is preferably 10% or less. The pressure-sensitive adhesive sheet preferably contains 0.1 to 10 parts by weight of the ultraviolet absorber relative to 100 parts by weight of the acrylic polymer. As the ultraviolet absorber, for example, a triazine type ultraviolet absorber is used. The acrylic polymer of the pressure-sensitive adhesive sheet may contain, as a monomer component, a polyfunctional monomer component having two or more polymerizable functional groups in one molecule.

The photocurable adhesive composition is irradiated with light through the first release film in a state in which the first main surface of the photocurable adhesive composition layer is attached with the above-mentioned first release film. A release film-attached pressure-sensitive adhesive sheet can be obtained. The photocurable adhesive composition contains an acrylic material, an ultraviolet absorber, and a photopolymerization initiator. Examples of the acrylic material contained in the photocurable adhesive composition include acrylic monomers and partial polymers thereof. The acrylic material may contain both an acrylic monomer and a partial polymer of an acrylic monomer.

In one Embodiment, light is irradiated from the 1st release film side with respect to the laminated body with the photocurable adhesive composition layer sandwiched between the 1st release film and the 2nd release film, and the photocurable The pressure-sensitive adhesive composition is photocured to obtain a pressure-sensitive adhesive sheet with a release film temporarily attached to both surfaces. The peeling force of a 1st release film and an adhesive sheet may be larger than the peeling force of a 2nd mold release film and an adhesive sheet with respect to the adhesive sheet to which the release film was temporarily affixed to both surfaces.

effect of invention

A pressure-sensitive adhesive sheet having high visible light transmittance and UV-shielding properties can be suitably used as an optical pressure-sensitive adhesive sheet for display devices and input devices for displays that require UV-shielding properties. The release film-attached pressure-sensitive adhesive sheet of the present invention can suppress an excessive increase in the peeling force between the pressure-sensitive adhesive sheet and the first release film, thereby preventing the release film from being peeled from the pressure-sensitive adhesive sheet and the pressure-sensitive adhesive sheet and the adherend. The operability of the fit is excellent.

Description of drawings

FIG. 1 is a cross-sectional view showing a laminated structure of a release film-attached pressure-sensitive adhesive sheet.

Symbol Description

1: Adhesive sheet with release film

50: Adhesive sheet

10, 20: Release film

11, 21: Substrate

15, 25: Release layer

5: Laminate

55: Photocurable Adhesive Composition Layer

Detailed ways

The pressure-sensitive adhesive sheet with a release film of the present invention includes a release film temporarily attached to at least one side of the pressure-sensitive adhesive sheet. "Temporary sticking" means the state sticking in a peelable manner. The PSA sheet with a release film may have a release film temporarily attached to both surfaces of the PSA sheet.

1 : is sectional drawing of the pressure-sensitive adhesive sheet 1 with a release film in which the release films 10 and 20 were temporarily stuck to both surfaces of the pressure-sensitive adhesive sheet 50. As shown in FIG. The adhesive sheet 50 is formed by forming an adhesive in a sheet shape. The adhesive sheet 50 is transparent, and its visible light absorption is small. The total light transmittance of the adhesive sheet 50 is preferably 85% or more, and more preferably 90% or more. The haze of the pressure-sensitive adhesive sheet is preferably 2% or less, and more preferably 1% or less. The total light transmittance and haze were measured according to JIS K7136 using a haze meter.

The adhesive sheet 50 is an acrylic adhesive containing a photocurable acrylic polymer, and contains an ultraviolet absorber in addition to the acrylic polymer. The acrylic pressure-sensitive adhesive sheet is formed of a light-curable pressure-sensitive adhesive obtained by combining a partial polymer (prepolymer) containing an acrylic monomer and/or an acrylic polymer, an ultraviolet absorber, and The photocurable adhesive composition of a photoinitiator is apply|coated in the form of a layer, and it is obtained by photocuring. In addition, in this specification, the "photocurable" adhesive means a photocurable adhesive including a compound containing a photopolymerizable functional group such as a vinyl group and a (meth)acryloyl group and is capable of being photocurable. The mixture "photocured" adhesive refers to an adhesive obtained by photocuring a photocurable adhesive. In addition, when a part of the photopolymerizable compound remains unreacted in the adhesive after polymerizing the photocurable adhesive, the adhesive is photocured and photocured. In the case of photocurable.

[Photocurable Adhesive Composition]

The photocurable adhesive composition contains a photopolymerizable acrylic material, an ultraviolet absorber, and a photopolymerization initiator.

＜Photopolymerizable acrylic material＞

Examples of the photopolymerizable acrylic material contained in the photocurable adhesive composition include acrylic monomers and partial polymers (prepolymers) thereof.

(single component)

As the acrylic monomer, an alkyl (meth)acrylate having an alkyl group of 1 to 20 carbon atoms can be suitably used, and the alkyl group of the alkyl (meth)acrylate may have a branch. The content of the alkyl (meth)acrylate is preferably 40% by weight or more, more preferably 50% by weight or more, and further preferably 60% by weight or more with respect to the total amount of monomer components of the acrylic material.

The monomer component may contain high polar monomers such as a hydroxyl group-containing monomer and a nitrogen-containing monomer in addition to the alkyl (meth)acrylate. When the acrylic polymer contains a highly polar monomer unit, the cohesive force of the adhesive can be improved, the adhesiveness of the adhesive sheet to the adherend can be improved, and the whitening of the adhesive in a high-temperature and high-humidity environment can be suppressed. It becomes cloudy, and there exists a tendency for the transparency of an adhesive sheet to improve.

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

唑、乙烯基吗啉、(甲基)丙烯酰基吗啉、N-乙烯基羧酸酰胺类、N-乙烯基己内酰胺等乙烯基类单体、丙烯腈、甲基丙烯腈等氰基丙烯酸酯类单体等。含氮单体优选具有含有氮原子的环状结构，其中，优选N-乙烯基吡咯烷酮等内酰胺类乙烯基单体。相对于单体成分总量，含氮单体的含量优选为0.5～50重量％、更优选为1～40重量％、进一步优选为3～30重量％。Examples of nitrogen-containing monomers include N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinyl imidazole, vinyl

azoles, vinylmorpholine, (meth)acryloylmorpholine, N-vinylcarboxylic acid amides, N-vinylcaprolactam and other vinyl monomers, acrylonitrile, methacrylonitrile and other cyanoacrylates Monomer, etc. The nitrogen-containing monomer preferably has a cyclic structure containing a nitrogen atom, and among them, lactam-based vinyl monomers such as N-vinylpyrrolidone are preferable. The content of the nitrogen-containing monomer is preferably 0.5 to 50% by weight, more preferably 1 to 40% by weight, and even more preferably 3 to 30% by weight relative to the total amount of monomer components.

The monomer component may contain monomers other than the above, such as a carboxyl group-containing monomer, a cyclic ether group-containing monomer, and a silane-based monomer.

唑啉、肼、羟甲基等聚合性官能团的化合物等。其中，优选在1分子中具有2个以上C＝C键的多官能聚合性化合物。多官能聚合性化合物可以以单体或低聚物的形式存在于粘合剂组合物中，也可以与预聚物成分的羟基等官能团键合。The monomer component may contain a polyfunctional polymerizable compound having two or more polymerizable functional groups in one molecule. Examples of the polyfunctional polymerizable compound include compounds having two or more C=C bonds in one molecule, compounds having one C=C bond, epoxy, aziridine,

Compounds with polymerizable functional groups such as oxazoline, hydrazine, and methylol. Among them, a polyfunctional polymerizable compound having two or more C=C bonds in one molecule is preferable. The polyfunctional polymerizable compound may exist in the adhesive composition as a monomer or an oligomer, and may be bonded to functional groups such as hydroxyl groups of the prepolymer component.

As the polyfunctional polymerizable compound having two or more C=C bonds in one molecule, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, new Pentanediol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate ) acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetra Polyfunctional acrylates such as methylolmethane tri(meth)acrylate (ester compound of polyol and (meth)acrylic acid); allyl (meth)acrylate, vinyl (meth)acrylate, divinyl benzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl di(meth)acrylate, hexyl di(meth)acrylate, etc. Among these, polyfunctional acrylates are preferred, and trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate, dipentaerythritol hexa(meth)acrylate, etc. are suitable as polyfunctional monomers .

The amount of the polyfunctional monomer to be used varies depending on its molecular weight, the number of functional groups, and the like, but is preferably 5 wt % or less, more preferably 3 wt % or less, and further preferably 2 wt % or less with respect to the total amount of monomer components. The amount of the polyfunctional monomer to be used may be 0.001 part by weight or more, 0.01 part by weight or more, or 0.05 part by weight or more with respect to the total amount of the monomer components.

In the photocurable adhesive composition, the above-mentioned monomer components may exist in the form of a partial polymer (prepolymer). The prepolymer refers to a polymer obtained by partially polymerizing a monomer component. By making a monomer component exist as a prepolymer, the viscosity of a photocurable adhesive composition can be adjusted to the range suitable for apply|coating to a support base material.

The prepolymer can be prepared, for example, by partially polymerizing a composition for forming a prepolymer obtained by mixing a monomer component and a polymerization initiator. The composition for prepolymer formation may contain all the monomer components which comprise an acrylic polymer, and may contain only a part of the monomer which comprises an acrylic polymer. When the monomer component constituting the acrylic polymer contains a monofunctional monomer and a polyfunctional monomer, the adhesive can be prepared by adding the polyfunctional monomer to the prepolymer composition obtained by partially polymerizing only the monofunctional monomer agent composition. By adding a polyfunctional monomer to a prepolymer composition obtained by partially polymerizing only a monofunctional monomer and carrying out post-polymerization, the crosslinking points by the polyfunctional monomer can be uniformly introduced into the polymer. A part of the polyfunctional monomer component which comprises an acrylic polymer may be contained in the composition for prepolymer formation, and after superposing|polymerizing a prepolymer, the remainder of a polyfunctional monomer component may be added and post-polymerization may be performed.

The prepolymer can be prepared by polymerization in two or more stages or three or more stages. For example, after prepolymerizing only a monofunctional monomer, a polyfunctional monomer may be added, partial polymerization may be performed, a prepolymer composition may be prepared, and if necessary, a monomer component may be further added and postpolymerization may be performed.

The polymerization method of the prepolymer is not particularly limited, but from the viewpoint of adjusting the reaction time and setting the molecular weight (polymerization rate) of the prepolymer in a desired range, photopolymerization by irradiation with actinic rays such as ultraviolet rays is preferable. In the case of photopolymerization, the prepolymer composition preferably contains a photopolymerization initiator, and specific examples of the photopolymerization initiator will be described later.

The composition for prepolymer formation may contain a chain transfer agent, etc. as needed, in addition to the monomer component and the polymerization initiator. The chain transfer agent has a function of accepting free radicals from the growing polymer chain to stop the elongation of the polymer, and the chain transfer agent that has received the free radical attacks the monomer to restart the polymerization. By using a chain transfer agent, an excessive increase in molecular weight is suppressed without reducing the radical concentration in the reaction system. As the chain transfer agent, α-thioglycerol, dodecyl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, mercaptoglycolic acid, 2-ethylhexyl mercaptoglycolic acid, 2, Thiols such as 3-dimercapto-1-propanol.

The polymerization rate of the prepolymer is not particularly limited, but is preferably 3 to 50%, and more preferably 5 to 40%, from the viewpoint of obtaining a viscosity suitable for coating on a substrate. The polymerization rate of the prepolymer can be adjusted to a desired range by adjusting the type and amount of the photopolymerization initiator, the irradiation intensity/irradiation time of actinic rays such as ultraviolet rays, and the like. The polymerization rate was calculated according to the following formula from the weight before and after heating (drying) when the prepolymer composition was heated at 130° C. for 3 hours. In the case of partial polymerization by solution polymerization, the weight obtained by subtracting the amount of the solvent from the total weight of the prepolymer composition was used as the weight before heating in the following formula, and the polymerization rate was calculated.

Polymerization rate (%) of polymer=100×(weight after heating/weight before heating)

<Preparation of photocurable adhesive composition>

A photocurable adhesive is obtained by mixing the remaining monomer components, an ultraviolet absorber, a photopolymerization initiator, and other additives with the above-mentioned photopolymerizable acrylic material (monomer and/or a partial polymer thereof) combination.

＜Ultraviolet absorber＞

Examples of the ultraviolet absorber include: benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, triazine-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, and the like . Triazine-based UV absorbers are preferred, and among them, triazine-based UV absorbers containing a hydroxyl group are preferred because they have high UV-absorbing properties, are excellent in compatibility with acrylic polymers, and can obtain high-transparency acrylic pressure-sensitive adhesive sheets. In particular, hydroxyphenyltriazine-based ultraviolet absorbers are preferred. The number of hydroxyl groups of the triazine-based ultraviolet absorber is preferably two or less.

As the ultraviolet absorber, a commercial item can be used. As a commercial item of a triazine type ultraviolet absorber, 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5 -Reaction product of hydroxyphenyl and [(alkoxy)methyl]ethylene oxide ("TINUVIN 400" manufactured by BASF), 2-(2,4-dihydroxyphenyl)-4,6-bis- Reaction product of (2,4-dimethylphenyl)-1,3,5-triazine and (2-ethylhexyl)glycidate (“TINUVIN 405” manufactured by BASF), (2,4 -Bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine ("TINUVIN 460" manufactured by BASF), 2- (4,6-Diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]phenol (“TINUVIN 577” manufactured by BASF), 2-(2-hydroxy-4 -[1-Octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine ("TINUVIN479" manufactured by BASF) and the like.

The content of the ultraviolet absorber in the photocurable adhesive composition is preferably 0.1 to 10 parts by weight, more preferably 0.3 to 7 parts by weight, and even more preferably 0.5 to 5 parts by weight relative to 100 parts by weight of the monomer components. By making content of an ultraviolet absorber into the said range, the fall of transparency by the exudation etc. of an ultraviolet absorber can be suppressed, and the ultraviolet-blocking property of an adhesive sheet can be improved. In addition, when the content of the ultraviolet absorber is within the above range, the reduction in the polymerization rate of the adhesive composition can be suppressed.

<Photopolymerization initiator>

The photocurable adhesive composition contains a photopolymerization initiator. The photopolymerization initiator is a photoradical generator that generates radicals by visible light or ultraviolet rays having a wavelength shorter than 450 nm.

When an ultraviolet absorber is contained in a photocurable adhesive composition, a part of irradiation light for photocuring is absorbed by the ultraviolet absorber. From the viewpoint of promoting the generation of radicals by cleavage of the photopolymerization initiator and increasing the polymerization rate, it is preferable to use a photopolymerization initiator having sensitivity in a wavelength region where the absorption by the ultraviolet absorber is small. Specifically, the photopolymerization initiator preferably has a sensitivity at a wavelength longer than 380 nm, and more preferably has a sensitivity at a wavelength longer than 400 nm. It is preferable to use a photopolymerization initiator having an absorption coefficient at a wavelength of 405 nm of 1×10 ² [mLg ⁻¹ cm ⁻¹ ] or more. The photopolymerization initiator having long-wavelength photosensitivity may have sensitivity to light having a wavelength of 400 nm or less.

Specific examples of the photopolymerization initiator having a light sensitivity of 400 nm or more in wavelength include 2,4,6-trimethylbenzoyldiphenylphosphine oxide ("Lucirin TPO" manufactured by BASF), 2,4,6-trimethylbenzoyldiphenylphosphine oxide ("Lucirin TPO" manufactured by BASF), Acylphosphine oxides such as 6-trimethylbenzoylphenylethoxyphosphine oxide ("Lucirin TPO-L" manufactured by BASF); 2-benzyl-2-dimethylamino-1-(4-morpholine) Amino ketones such as phenyl)butanone-1 (“Irgacure 369” manufactured by BASF); bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (“Irgacure 819” manufactured by BASF), 2, 2-Dimethoxy-1,2-diphenylethan-1-one ("Irgacure651" manufactured by BASF), bis(2,6-dimethoxybenzoyl)-2,4,4-tris Bisacylphosphine oxides such as methylamylphosphine oxide ("CGI403" manufactured by BASF), etc.

As the photopolymerization initiator, a photopolymerization initiator having a long-wavelength photosensitivity and a photopolymerization initiator not having a long-wavelength photosensitivity (for example, an absorption coefficient at a wavelength of 405 nm of less than 1×10 ² [mLg ^{− 1} cm ^-1 ] of photopolymerization initiator).

Examples of photopolymerization initiators that do not have long-wavelength photosensitivity include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-alcohol ketone-based photopolymerization initiators, and photoactive oximes. Photopolymerization initiator, benzoin-based photopolymerization initiator, benzil-based photopolymerization initiator, benzophenone-based photopolymerization initiator, ketal-based photopolymerization initiator, thioxanthone-based photopolymerization initiator, Acylphosphine oxide-based photopolymerization initiator, cyclopentadiene titanium-based photopolymerization initiator, etc.

The content of the photopolymerization initiator in the photocurable adhesive composition is preferably 0.02 to 10 parts by weight, and more preferably 0.05 parts by weight relative to 100 parts by weight of the total of the monomer components and prepolymer components constituting the acrylic polymer. ~ 5 parts by weight. When there are too few photoinitiators, the polymerization rate may become insufficient, and when there are too many photoinitiators, the molecular weight of a polymer may be low, and the adhesive force of an adhesive may become insufficient.

As described above, in the preparation (partial polymerization) of the prepolymer, a photopolymerization initiator can also be used. The photopolymerization initiator used for the partial polymerization may be the same as or different from the photopolymerization initiator added to the photocurable adhesive composition. The composition for forming a prepolymer does not contain an ultraviolet absorber, but when the ultraviolet absorber is added after the partial polymerization, the photopolymerization initiator used for the partial polymerization may not have long-wavelength photosensitivity. The unreacted product of the photopolymerization initiator used for the partial polymerization may be used as it is as the photopolymerization initiator in the photopolymerizable adhesive composition.

From the viewpoint of the utilization efficiency of irradiated light, etc., it is preferable to add the ultraviolet absorber to the partially polymerized prepolymer composition without containing the ultraviolet absorber in the prepolymer-forming composition. For example, it is preferable to use a photopolymerization initiator that does not have a long-wavelength photosensitivity as a pre-added polymerization initiator, perform partial polymerization, and add an ultraviolet absorber and a post-added polymerization initiator with a long wavelength to the partially polymerized composition. A photopolymerization initiator with a light sensitivity of 100% is used to prepare a photocurable adhesive composition, and after coating the photocurable adhesive composition in a layer on a substrate, post-polymerization is performed.

＜Other ingredients＞

A chain transfer agent may be contained in the photocurable adhesive composition. The chain transfer agent contained in the photocurable adhesive composition is not particularly limited, and for example, the above-mentioned chain transfer agent can be used. A silane coupling agent, a crosslinking agent, a tackifier, a plasticizer, a softener, etc. may be contained in the adhesive composition for the purpose of adjusting the adhesive force or the like. In addition, the adhesive composition may contain additives such as anti-deterioration agents, fillers, colorants, antioxidants, surfactants, and antistatic agents within a range that does not impair the properties of the adhesive.

The photocurable adhesive composition preferably has a viscosity suitable for coating on a substrate (for example, about 5 to 100 poise). The viscosity of the adhesive composition can be adjusted by, for example, addition of various polymers such as tackifiers, polyfunctional monomers, and the like, the polymerization rate of the prepolymer, and the like. In the photocurable adhesive composition, the content of the acrylic monomer component (the acrylic monomer and the partial polymer of the acrylic monomer) is 50% by weight or more, more preferably 70% by weight or more, and even more preferably 80% by weight or more.

[Formation of adhesive sheet]

The above-mentioned photocurable adhesive composition is applied on a support substrate and photocured to obtain an adhesive sheet. Examples of methods for applying the adhesive composition to the substrate include roll coating, lick coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, Bar coating method, blade coating method, air knife coating method, curtain coating method, die lip coating method, die coating method. Since oxygen in the air inhibits photo-radical polymerization, it is preferable to block oxygen by attaching a cover sheet to the coating layer of the photocurable adhesive composition. The pressure-sensitive adhesive composition may also be applied so that the photocurable pressure-sensitive pressure-sensitive adhesive composition is sandwiched between two sheets (support base material and cover sheet).

The coating thickness of the photocurable pressure-sensitive adhesive composition (thickness of the pressure-sensitive adhesive sheet 50 ) is not particularly limited, but is, for example, about 10 to 500 μm. The thickness of the adhesive sheet is preferably 50 μm or more, more preferably 100 μm or more, and even more preferably 150 μm or more, from the viewpoint of improving the ultraviolet absorbability by the adhesive sheet. The light transmittance of the pressure-sensitive adhesive sheet 50 at a wavelength of 380 nm is preferably 10% or less, more preferably 5% or less, and further preferably 3% or less.

The laminated body provided with the photocurable acrylic pressure-sensitive adhesive composition layer on the support substrate is irradiated with ultraviolet rays and/or short-wavelength visible light, and photocured to obtain a pressure-sensitive adhesive sheet. In the case of photocuring by irradiating the laminated body with the photocurable adhesive composition layer sandwiched between the support base and the cover sheet, it can be cured from the support base material side and the cover sheet side. Light irradiation may be performed on either side, or light irradiation may be performed from both sides. As described in detail later, in the present invention, a release film 10 provided with a predetermined release layer 15 can be used as a support substrate or a cover sheet attached to the light-irradiated surface side of the pressure-sensitive adhesive sheet.

From the viewpoint of improving the curing speed, the light irradiation intensity is preferably 5 mW/cm ² or more. From the viewpoint of sufficiently increasing the molecular weight of the acrylic polymer after photocuring and securing the retention force at high temperature, the light irradiation intensity is preferably 20 mW/cm ² or less,

The cumulative light amount of the irradiation light is preferably about 100 to 5000 mJ/cm ² . The light source for light irradiation is not particularly limited as long as it can irradiate light in the wavelength range of the sensitivity of the photopolymerization initiator contained in the adhesive composition, but LED light sources, high-pressure mercury lamps, ultra-high-pressure mercury lamps, Metal halide lamps, xenon lamps, etc.

Most of the ultraviolet light irradiated to the photocurable adhesive composition containing the ultraviolet absorber is absorbed by the ultraviolet absorber. It is preferable to irradiate light in a wavelength region where the light absorption by the ultraviolet absorber is small from the viewpoints of suppressing lowering of the molecular weight due to temperature rise and improving the utilization efficiency and curing speed of the irradiated light. Since heat generation from the light source is small and light in a narrow wavelength range can be irradiated, an LED light source is preferably used. When an LED light source is used, the emission peak wavelength is preferably 350 nm or more, more preferably 380 nm or more, and further preferably 400 nm or more.

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

[Release film]

As a support substrate for applying the adhesive composition, and a cover sheet attached to the surface of the coating layer of the adhesive composition, it is preferable to use a mold release provided on the contact surface with the coating layer (adhesive sheet). layer of release film. In the present invention, it is performed in a state where the release film (first release film) 11 provided with the predetermined silicone-based release layer 15 is attached on the light irradiation surface side of the photocurable adhesive composition layer 55 . light curing.

＜Substrate＞

As the base materials 11 and 21 of the release films 10 and 20, various resin films having transparency are used. Examples of the resin material include polyester-based resins such as polyethylene terephthalate and polyethylene naphthalate, acetate-based resins, polyethersulfone-based resins, polycarbonate-based resins, and polyamides. resin, polyimide-based resin, polyolefin-based resin, (meth)acrylic resin, polyvinyl chloride-based resin, polyvinylidene chloride-based resin, polystyrene-based resin, polyvinyl alcohol-based resin, polyarylene Ester resin, polyphenylene sulfide resin, etc. Among these, polyester-based resins such as polyethylene terephthalate are particularly preferable. The thickness of the base materials 11 and 21 is preferably 10 to 200 μm, and more preferably 25 to 150 μm.

＜Release layer＞

As a material of a mold release layer, a silicone-based mold release agent, a fluorine-based mold release agent, a long-chain alkyl-based mold release agent, a fatty acid amide-based mold release agent, a silica powder, etc. are mentioned. Since both adhesiveness and peelability to an acrylic pressure-sensitive adhesive sheet can be achieved, it is preferable to use a release film having a silicone-based mold release layer 25 formed of a silicone-based mold release agent on the surface of the film substrate 21 as a release film. Molding film 20 .

The release film 10 attached to the light irradiation surface side of the photocurable adhesive composition layer 55 includes the silicone-based release layer 15 . The Si atomic content per unit area of the silicone-based mold release layer 15 is 0.02 to 0.07 g/m ² . The Si atom content of the silicone-based mold release layer 15 is preferably 0.025 to 0.06 g/m ² , and more preferably 0.03 to 0.055 g/m ² .

The silicone-based mold release layer 15 of the mold release film 10 contains a curable silicone resin. The silicone-based resin may be a type that is itself a main component, or a silicone obtained by introducing a reactive silicone into an organic resin such as a urethane resin, an epoxy resin, and an alkyd resin by graft polymerization or the like. Modified resin. As the silicone resin, silicone resins of various curing reaction types such as addition type, condensation type, ultraviolet curing type, electron beam curing type, and solvent-free type can be used. In particular, since it is excellent in adhesiveness with the film base material and can achieve both moderate adhesiveness and releasability with respect to an acrylic pressure-sensitive adhesive sheet, it is preferable to use a type that forms a releasable film by curing by an addition reaction with heat of silicone resins.

Examples of the silicone-based material to be cured by addition reaction include polyorganosiloxane having a vinyl group or an alkenyl group in the molecule. Examples of the alkenyl group include 3-butenyl, 4-pentenyl, 5-hexenyl, 6-heptenyl, 7-octenyl, 8-nonenyl, 9-decenyl, 10-undecenyl, 11-dodecenyl, etc. Examples of the polyorganosiloxane include polyalkylalkylsiloxanes such as polydimethylsiloxane, polydiethylsiloxane, and polymethylethylsiloxane; polyalkylarylsiloxanes; Alkane, poly(dimethylsiloxane-diethylsiloxane, etc.), a copolymer containing a plurality of Si atom-containing monomer components, etc. are used. Among these, polydimethylsiloxane is preferable.

As the silicone resin, a commercially available composition containing a curable silicone resin can be used. Commercially available curable silicone-based mold release agents include KS-774, KS-775, KS-778, KS-779H, KS-847H, KS-856, and X-62-2422 manufactured by Shin-Etsu Chemical Industry Co., Ltd. , and X-62-2461; YSR-3022, TPR-6700, TPR-6720, and TPR-6721 manufactured by Toshiba Silicones; LTC300B, LTC303E, LTC310, LTC314, SRX357, BY24-749, SD7333 manufactured by Toray Dow Corning , BY24-179, BY24-840, BY24-842, BY24-850, SP7015, SP7259, SD7220, SD7226, and SD7229; DKQ3-202, DKQ3-203, DKQ3-204, DKQ3-205, DKQ3 manufactured by Dow Corning Asia -210 etc.

The curable silicone-based mold release agent composition may further contain an additive (peeling control agent) for the purpose of adjusting the peelability of the mold release layer or the like. The addition-type silicone-based mold release agent composition may contain a curing catalyst. As the curing catalyst, platinum-based catalysts are preferred. Examples of the platinum-based catalyst include chloroplatinic acid, an olefin complex of platinum, an olefin complex of chloroplatinic acid, and the like. The amount of the platinum-based catalyst to be used is about 10 to 1000 ppm in terms of platinum with respect to the total solid content of the silicone-based mold release agent composition.

The silicone-based mold release agent 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; ketones such as acetone and methyl ethyl ketone Solvents; alcohol solvents such as methanol, ethanol, butanol, etc. The organic solvent may also be a mixed solvent. It is preferable that the usage-amount of an organic solvent is about 80-99.9 mass % in a silicone type mold release agent composition.

The silicone-based mold release agent composition may contain various additives such as fillers, antistatic agents, antioxidants, plasticizers, and colorants as needed.

The silicone-based mold release layer is formed by applying the silicone-based mold release agent composition on the base material 11 and heating and drying it. Examples of the coating method include roll coating, lick coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, blade coating, gas coating Knife coating method, curtain coating method, die lip coating method, die coating method. As a heat drying method, hot air drying is mentioned. The conditions of hot air drying vary depending on the heat resistance of the base material, 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 mold release agent composition may be adjusted so that the amount of the silicone resin is about 0.03 to 1 g/m ² . The thickness of the silicone-based mold release layer 15 is, for example, 10 to 500 nm. The coating amount of the silicone-based mold release agent composition and the thickness of the silicone-based mold release layer 15 may be adjusted so that the Si atom content of the silicone-based mold release layer 15 is within the above-mentioned range.

[Releasability of release film and adhesive sheet]

For a release film-attached pressure-sensitive adhesive sheet in which a release film is temporarily adhered to both sides of the pressure-sensitive adhesive sheet, the peeling force between the pressure-sensitive adhesive sheet and one release film is generally relatively smaller than the peeling force between the pressure-sensitive adhesive sheet and the other release film. force. When using a pressure-sensitive adhesive sheet, a release film (light release film) with a low peeling force was peeled from the pressure-sensitive adhesive sheet and bonded to the first adherend, and then a release film with a relatively large peeling force ( Heavy release film) was peeled off, and lamination with the second adherend was performed. By providing a difference in peeling force to the release film temporarily bonded on the front and back of the pressure-sensitive adhesive sheet, the light release film can be selectively peeled off when bonding with the first to-be-adhered body, so that the bonding operation can be improved sex.

In a photocurable PSA sheet, the adhesive strength of the PSA differs before and after photocuring. Therefore, the light release film and the heavy release film are adjusted in consideration of the adhesive properties of the PSA sheet after photocuring. Adhesiveness (peelability) of the adhesive sheet. In the case where the adhesive composition does not contain an ultraviolet absorber, the magnitude relationship of the peeling force between one release film and the other release film does not change before and after photocuring. On the other hand, when the photocurable adhesive composition contains an ultraviolet absorber, the increase in the peeling force of the first release film on the side where the light is irradiated is remarkably larger than that of the second release film arranged on the opposite side. The tendency for the peel force of the film to increase.

Therefore, in the pressure-sensitive adhesive sheet with a release film of the present invention, it is preferable to make the first release film 10 of the light irradiation surface a heavy release film, and the second release film 20 of the opposite surface to be a light release film . That is, it is preferable that the peeling force of the 1st release film 10 and the adhesive sheet 50 is larger than the peeling force of the 2nd release film 20 and the adhesive sheet 50.

When the peeling force between the first release film 10 (heavy release film) and the pressure-sensitive adhesive sheet 50 is too large, the first release film 10 is removed from the adhesive sheet in a state where the pressure-sensitive adhesive sheet 50 is attached to the first adherend. When the surface of the bonding sheet 50 is peeled off, problems such as deformation of the pressure-sensitive adhesive sheet and peeling of the pressure-sensitive adhesive sheet from the adherend may occur. The peeling force of the pressure-sensitive adhesive sheet 50 after photocuring and the first release film 10 is preferably 0.1 to 1.1 N/50 mm, more preferably 0.2 to 0.8 N/50 mm, and even more preferably 0.3 to 0.7 N/50 mm. The peeling force between the release film and the pressure-sensitive adhesive sheet is a measured value obtained by a 180° peel test at a tensile speed: 0.3 m/min. In this invention, by making the Si atom content in the release layer 15 of the 1st release film 10 into the said range, the excessive rise of the peeling force of the pressure-sensitive adhesive sheet after photocuring and the 1st release film can be suppressed .

When the photocurable adhesive composition contains an ultraviolet absorber, the reason why the peeling force of the first release film increases, and the adjustment of the Si content in the release layer can suppress the deterioration of the adhesive composition. The reason for the excessive increase in the peeling force after photocuring is not clear, but it is presumed to be related to the reaction between the unreacted thermally reactive functional group in the release layer and the compound in the pressure-sensitive adhesive composition.

As described above, most of the ultraviolet light irradiated to the photocurable adhesive composition containing the ultraviolet absorber is absorbed by the ultraviolet absorber. Even when the sensitivity wavelength of the photopolymerization initiator and the wavelength of the irradiation light are shifted to the long wavelength side (eg, 400 nm or more), it is difficult to completely suppress the light absorption by the ultraviolet absorber. When the UV absorber absorbs light, the light energy is converted into heat energy, and the temperature rises. In particular, in the vicinity of the interface between the release layer 15 and the adhesive composition layer 55 on the light-irradiated surface side, the light absorption amount by the ultraviolet absorber is large, and therefore the temperature tends to rise. When the temperature rises under light irradiation, in addition to the photocuring reaction, the thermosetting reaction also tends to proceed. Therefore, it is considered that unreacted thermally reactive functional groups (vinyl groups, alkenyl groups, alkoxysilyl groups, silanol groups, hydrosilyl groups, etc.) in the release layer 15 react with the compounds in the adhesive composition , the adhesive force (peeling force) increases.

By reducing the Si atom content per unit area of the silicone-based mold release layer 15, the amount of unreacted thermally reactive functional groups in the mold release layer 15 is reduced. Therefore, in the present invention, it is considered that the amount of residual reactive functional groups in the release layer 15 that can react with the compound in the pressure-sensitive adhesive composition layer 15 is small, and the pressure-sensitive adhesive sheet 50 and the release film after photocuring can be suppressed. Excessive rise in peel force of 10.

As described above, the light irradiation to the pressure-sensitive adhesive composition may be performed from either side of the support substrate side and the cover sheet side, or may be performed from both sides. When light irradiation is performed from the support base material side, what is necessary is just to use the mold release film 10 provided with the above-mentioned silicone-based mold release layer 15 as the support base material to which the adhesive composition is applied. When light irradiation is performed from the cover sheet side, the release film 10 provided with the above-mentioned silicone-based mold release layer 15 may be used as the cover sheet attached to the adhesive composition layer 55 .

When light is irradiated from both sides, the above-mentioned mold release film may be used for either the support base or the cover sheet. The above-mentioned release film may be used for both the support base and the cover sheet. As described in Japanese Patent Application Laid-Open No. 2014-65754, in the case of irradiating both surfaces with light while conveying along a folded route in which the conveying direction is reversed, it is preferable to use the above-mentioned release film for the surface irradiated with light first.

[Use of adhesive sheet]

The above-mentioned photocurable pressure-sensitive adhesive sheet has high visible light transmittance and UV-blocking properties, and is therefore suitable as an optical adhesive for display devices and input devices for displays that require UV-blocking properties. As a display device, a liquid crystal display device, an organic EL (electroluminescence) display device, a PDP (plasma display panel), electronic paper, etc. are mentioned. As an input device, a touch panel is mentioned. Moreover, the above-mentioned photocurable pressure-sensitive adhesive sheet can also be used for bonding of a display device and an input device, bonding with a transparent plate arranged on the surface of a display device and an input device, and the like.

When using a release film-attached pressure-sensitive adhesive sheet to which a release film is temporarily stuck on both sides, first, the light release film (second release film 20) is peeled off to expose the second main surface of the pressure-sensitive adhesive sheet 50, and the first The fit of the adherend. Then, the heavy release film (1st release film 10) is peeled off, the 1st main surface of the pressure-sensitive adhesive sheet 50 is exposed, and bonding with a 2nd to-be-adhered body is performed. After peeling off the release film on both sides, you may perform bonding with the to-be-adhered body. When the PSA sheet has photocurability, the PSA sheet bonded to the adherend may be further irradiated with light. By further photocuring the pressure-sensitive adhesive sheet after bonding with the to-be-adhered body, the adhesion reliability with the to-be-adhered body may be improved.

Example

Hereinafter, although an Example and a comparative example are given and demonstrated further, this invention is not limited to these Examples.

[Preparation of Photocurable Adhesive Composition]

<Adhesive composition A>

In a monolith consisting of 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 1-Hydroxycyclohexyl phenyl ketone ("Irgacure 184" manufactured by BASF) was added as a photopolymerization initiator (photopolymerization initiator was added first) to the bulk mixture: 0.035 parts by weight, and 2,2-dimethoxy- 1,2-Diphenylethan-1-one ("Irgacure 651" manufactured by BASF): 0.035 part by weight. This composition was irradiated with ultraviolet rays and prepolymerized until the viscosity at room temperature reached about 20 Pa·s, and a prepolymer having a polymerization rate of about 8% was obtained.

To 100 parts by weight of the prepolymer, hexanediol diacrylate (HDDA): 0.15 parts by weight, silane coupling agent ("KBM-403" manufactured by Shin-Etsu Chemical Industry Co., Ltd.): 0.3 parts by weight, ultraviolet absorber (2,4 -Bis-[{4-(4-ethylhexyloxy)-4-hydroxy}-phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine; manufactured by BASF" Tinosorb S") 15% by weight solution of butyl acrylate (BA): 4.7 parts by weight (ultraviolet absorber: 0.7 parts by weight), and bis(2,4,6-trimethylbenzyl as a post-addition polymerization initiator) Acyl) phenylphosphine oxide ("Irgacure 819" by BASF): 0.15 weight part, and the ultraviolet-curable acrylic pressure-sensitive adhesive composition A was obtained.

<Adhesive composition B>

An adhesive composition B was obtained in the same manner as in the preparation of the adhesive composition 1, except that the addition amount of the post-addition polymerization initiator was changed from 0.15 part by weight to 0.1 part by weight.

<Adhesive composition C>

In the preparation of the prepolymer composition, the composition of the monomer mixture was changed to 2EHA: 30.5 parts by weight, isostearyl acrylate (ISTA): 30.5 parts by weight, isobornyl acrylate (IBXA): 19 parts by weight, and 4-Hydroxybutyl acrylate (4HBA): 20 parts by weight, and the addition amount of the photopolymerization initiator: 1-hydroxycyclohexyl phenyl ketone: 0.05 parts by weight, and 2,2-dimethoxy-1,2- Diphenylethan-1-one: 0.05 part by weight Except for these changes, adhesive composition C was obtained in the same manner as in the preparation of adhesive composition 1.

[Preparation of silicone-based mold release agent solution]

<Mold release agent solution A>

A hexenyl group-containing addition type silicone (containing a polyorganosiloxane having a hexenyl group in a molecule and a hydrosilyl group having a 30% toluene solution (“LTC761” manufactured by Toray Dow Corning): 30 parts by weight, silicone dispersion (“BY 24 manufactured by Toray Dow Corning”) -850"): 0.9 parts by weight, and a platinum catalyst for silicone curing ("SRX 212" by Toray Dow Corning): 2 parts by weight were diluted to a predetermined concentration shown in Table 1, and a release agent solution A was prepared.

<Mold release agent solution B>

Using a mixed solvent of toluene and hexane at a volume ratio of 1:1, 10 parts by weight of a 30% toluene solution of vinyl-containing addition silicone ("KS-847T" manufactured by Shin-Etsu Chemical) and a platinum catalyst for silicone curing ( A release agent solution B was prepared by diluting 1 part by weight of Shin-Etsu Chemical Co., Ltd. "CAT-PL-50T" to a predetermined concentration shown in Table 1.

[Example 1]

<Production of base material release film>

Using a wire bar (#15), a release agent solution prepared so that the solid content of silicone was 1.25% by weight was applied to one side of a biaxially oriented polyester film (“Lumirror XD500P” manufactured by Toray Advanced Materials Korea) having a thickness of 75 μm. B, it heated for 1 minute using a 130 degreeC hot air dryer, and formed the mold release layer.

<Production of lid release film>

Using a wire bar (#9), a release agent solution prepared so that the solid content of silicone was 0.7% by weight was applied to one side of a biaxially oriented polyester film (“Lumirror XD500P” manufactured by Toray Advanced Materials Korea) having a thickness of 75 μm. A, it heated for 1 minute using a 130 degreeC hot air dryer, and formed the mold release layer.

<Preparation of pressure-sensitive adhesive sheet with release film>

On the release layer forming surface of the above-mentioned coating base release film, the adhesive composition A was applied to a thickness of 150 μm to form a coating layer, and a lid release film was attached to the surface of the coating layer to obtain a Laminate. This laminate was irradiated with ultraviolet rays from the lid release film side under the conditions of illuminance: 6.5 mW/cm ² , cumulative light intensity: 1500 mJ/cm ² , and the coating layer was photocured to obtain a photocurable adhesive. An adhesive sheet with a release film on both sides of the layer.

[Examples 2 to 6 and Comparative Examples 1 to 3]

The type and concentration of the release agent solution, the wire diameter (type) of the wire rod, and the type of the adhesive composition were changed as shown in Table 1 at the time of making the lid release film, and other than these changes, the same Example 1 A photocurable pressure-sensitive adhesive sheet having a release film on both surfaces was produced in the same manner.

[Evaluation]

<Si atom content of mold release layer>

The amount of Si atoms per unit area (mg/m ² ) was calculated by X-ray fluorescence analysis (XRF) of the surface of the release layer covering the release film. In the XRF analysis, a scanning type fluorescent X-ray analyzer (“ZSX100e” manufactured by Rigaku) having a vertical rhodium tube as an X-ray source was used, analysis area: 30 mmφ, analysis element: Si, spectroscopic crystal: RX4, output: 50 kV , the measurement was carried out under the condition of 70mA.

<Peeling force of release film>

The pressure-sensitive adhesive sheet with the release film was cut out to a width of 50 mm, and a 180° peel test was carried out at a tensile speed of 0.3 m/min using a tensile tester in an environment of 23° C. The respective peeling force when the lid release film is peeled off from the pressure-sensitive adhesive sheet.

[Evaluation results]

The structure of the release layer (type of release agent solution, silicone concentration, thickness, and Si amount), type of adhesive, and evaluation results of peeling force in the cover release films of Examples and Comparative Examples are shown. in Table 1.

[Table 1]

In Examples 1 to 6 and Comparative Examples 1 to 3, the peeling force of the base material release film was all about 0.2 N/50 mm, and no significant difference was observed. In Comparative Example 3 in which the same release agent was used for the base release film and the cover release film, the peel force of the cover release film after photocuring of the pressure-sensitive adhesive sheet was set to More than 10 times, peeling is difficult. In Comparative Example 1 in which the type of the silicone release agent of the lid release film and the composition of the adhesive were changed, similarly to Comparative Example 3, the peeling force of the lid release film was greatly increased. From these results, it was found that when photocuring was performed by irradiating a laminate in which a photocurable pressure-sensitive adhesive sheet containing an ultraviolet absorber was sandwiched between two release films, the release sheet on the light-irradiated surface had The peeling force increases.

In Comparative Example 2 in which the concentration and coating thickness of the release agent solution at the time of making the cover release film were made larger than those of Comparative Example 1, the amount of Si per unit area of the release layer increased, and the cover after photocuring the pressure-sensitive adhesive sheet The peeling force of the mold release film was also larger than that of Comparative Example 1.

In Examples 1, 4, and 5 in which the amount of Si per unit area was reduced by adjusting the concentration of the release agent solution and the coating thickness at the time of producing the lid release film, the lid release after photocuring the pressure-sensitive adhesive sheet The peeling force of the mold film is reduced to less than 1 N/50 mm, and problems such as deformation of the pressure-sensitive adhesive sheet during peeling are less likely to occur. From the results of Examples 1, 4, 5 and Comparative Examples 1 and 2, it was found that by reducing the amount of Si per unit area of the release layer, the peeling force of the cover release film after photocuring of the pressure-sensitive adhesive sheet was reduced.

In Example 2 and Example 3 in which the same lid release film as in Example 1 was used but the composition of the adhesive was changed, the peeling force of the lid release film was equivalent to that of Example 1. Also in Example 6 using the same PSA sheet as in Example 2, the peelability of the lid release film after photocuring the PSA sheet was favorable.

From the above results, it was found that by attaching a release sheet having a release layer having a Si atomic weight per unit area within a predetermined range to a photocurable pressure-sensitive adhesive sheet containing an ultraviolet absorber, it is possible to suppress the photocuring of the pressure-sensitive adhesive sheet. An excessive increase in the peeling force of the release film.

Claims (9)

1. An adhesive sheet with a release film comprising: a photocurable pressure-sensitive adhesive sheet having a first main surface and a second main surface, and The first release film temporarily attached to the first main surface of the pressure-sensitive adhesive sheet, in, The first release film is provided with a release layer on the film substrate, the release layer is in contact with the adhesive sheet, The adhesive sheet includes a photocurable acrylic polymer and an ultraviolet absorber, The mold release layer is a silicone-based mold release layer, and the Si atom content is 0.02-0.07 g/m ² . 2 . The release film-attached pressure-sensitive adhesive sheet according to claim 1 , further comprising a second release film temporarily attached to the second main surface of the pressure-sensitive adhesive sheet. 3 . 3. The pressure-sensitive adhesive sheet with a release film according to claim 2, wherein The peeling force of the said 1st mold release film and the said adhesive sheet is greater than the peeling force of the said 2nd mold release film and the said adhesive sheet. 4 . The release film-attached pressure-sensitive adhesive sheet according to claim 1 , wherein The light transmittance of the pressure-sensitive adhesive sheet at a wavelength of 380 nm is 10% or less. 5 . The release film-attached pressure-sensitive adhesive sheet according to claim 1 , wherein The acrylic polymer includes, as a monomer component, a polyfunctional monomer component having two or more polymerizable functional groups in one molecule. 6 . The release film-attached pressure-sensitive adhesive sheet according to claim 1 , wherein The ultraviolet absorber is a triazine ultraviolet absorber. 7 . The release film-attached pressure-sensitive adhesive sheet according to claim 1 , wherein The pressure-sensitive adhesive sheet contains 0.1 to 10 parts by weight of the ultraviolet absorber with respect to 100 parts by weight of the acrylic polymer. 8. A method for producing a PSA sheet with a release film, the PSA sheet with a release film comprising: A photocurable pressure-sensitive adhesive sheet having a first main surface and a second main surface, the first release film temporarily attached to the first main surface of the pressure-sensitive adhesive sheet, and The second release film temporarily attached to the second main surface of the pressure-sensitive adhesive sheet, The method includes: A step of preparing a laminate in which a photocurable adhesive composition layer containing an acrylic monomer and /or partial polymers of acrylic monomers, UV absorbers, and photopolymerization initiators; and The step of irradiating the laminate with light from the first release film side to photocuring the photocurable adhesive composition, in, The first release film is provided with a release layer on the surface of the film substrate on the side that is in contact with the photocurable adhesive composition, The mold release layer is a silicone-based mold release layer, and the Si atom content is 0.02-0.07 g/m ² . 9 . The method for producing a pressure-sensitive adhesive sheet with a release film according to claim 8 , wherein The photopolymerization initiator has sensitivity at a wavelength longer than 400 nm.

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