TW202138521A - Adhesive sheet with release film and manufacturing method thereof - Google Patents

Abstract

This adhesive sheet (1) with release film is provided with a first release film (10) which is temporarily adhered to a first primary surface of a photocurable adhesive sheet (50) and a second release film (20) which is temporarily adhered to the second primary surface of the adhesive sheet. The adhesive sheet contains a photocurable acrylic polymer and a UV absorbing agent. A first release layer (15) of the first release film is a fluorine-base release layer or a condensation-type silicone release layer. This adhesive sheet with release film is obtained, for example, by providing, in layer form between the first release film and the second release film, a photocurable adhesive composition that contains acrylic monomers and/or a partial polymer of acrylic monomers, a UV absorbing agent and a photopolymerization initiator, and irradiating light from the first release film side to photo-cure the photocurable adhesive composition.

Description

Adhesive sheet with release film and manufacturing method thereof

The invention relates to an adhesive sheet temporarily attached with a release film and a manufacturing method thereof.

In display devices such as liquid crystal displays or organic EL (Electroluminescence) displays, or display input devices such as touch panels, a transparent adhesive sheet is used for bonding optical members. The transparent adhesive sheet is usually provided in the form of an adhesive sheet with a release film attached on both sides. When using an adhesive sheet, first peel off one of the release films (light release film) to expose one side of the adhesive sheet and adhere to the first adherend, and then peel off the other release film (heavy release film) to make the adhesive The other side of the sheet is attached to the second adherend.

In consideration of deterioration of self-inhibiting elements due to ultraviolet rays, there are cases in which optical members used in display devices, input devices, and the like are required to have ultraviolet cutoff properties. For example, in an organic EL display, the organic molecules constituting the light-emitting layer and the like are degraded by ultraviolet rays, which greatly affects the display characteristics. Therefore, the optical members arranged on the front surface of the element require high ultraviolet cutoff properties. In addition, with regard to the polarizing plate used in the liquid crystal display or the organic EL display, in order to prevent the deterioration of the polarizing element caused by ultraviolet rays (for example, the fading of iodine), the optical member arranged on the front surface of the polarizing element is required to have ultraviolet cutoff properties.

As a method of imparting ultraviolet cut-off properties to the adhesive sheet, a method of adding an ultraviolet absorber to the adhesive composition is known. For example, it is described in Patent Document 1 that an adhesive composition with a UV absorber added to a thermally polymerizable acrylic adhesive solution is coated into a film, and then heated and dried to obtain an adhesive sheet with UV cut-off properties. . Patent Document 2 describes that a photocurable acrylic adhesive composition is sandwiched between two release films to obtain a photocurable adhesive sheet having ultraviolet cut-off properties. The acrylic adhesive composition contains a photocurable acrylic composition, a photopolymerization initiator, and an ultraviolet absorber. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2013-75978 [Patent Document 2] Japanese Patent Laid-Open No. 2019-112505

[The problem to be solved by the invention]

The photocurable adhesive sheet usually does not require a solvent, and is obtained by photocuring (photopolymerization) in a state where the substrate sheet is attached to both sides of the photocurable adhesive composition. Therefore, the light-curing adhesive sheet has the advantages of being easy to increase in thickness and improving smoothness.

However, as described in Patent Document 2, there are cases where a photocurable adhesive composition containing an ultraviolet absorber is irradiated with ultraviolet light through a release film to be photocured, and the release film and photocuring of the light-irradiated surface The peeling force of the subsequent adhesive sheet will be greatly improved, and it is difficult to peel off the release film when it is attached to the adherend. It is proposed in Patent Document 2 that by adjusting the thickness of the addition-molded silicone release layer, etc., the peeling force of the release film and the adhesive sheet can be reduced, but the peeling force of the release film and the adhesive sheet after photocuring can be sufficiently reduced It is not easy.

In view of the above-mentioned problems, the object of the present invention is to provide an adhesive sheet with a release film that has ultraviolet cutoff properties and has good peelability from the release film. [Technical means to solve the problem]

The adhesive sheet with release film of the present invention includes: a light-curing adhesive sheet having a first main surface and a second main surface, and a first release film temporarily adhered to the first main surface of the adhesive sheet. The first release film is provided with a first release layer on the first film substrate, and the first release layer is connected to the adhesive sheet. The adhesive sheet with release film may also have a second release film temporarily adhered to the second main surface of the adhesive sheet. The adhesive sheet contains a light-curing acrylic polymer and an ultraviolet absorber.

The first main surface of the adhesive sheet is the light irradiated surface when the photocurable adhesive composition is photocured. That is, the photocurable adhesive composition is irradiated with light via the first release film to form a photocurable adhesive sheet. The first release layer of the first release film attached to the light-irradiated side of the photocurable adhesive composition is a fluorine-based release layer or a condensed silicone release layer. The second release layer of the second release film can also be a non-fluorine-based addition type silicone release layer.

The light transmittance of the adhesive sheet at a wavelength of 380 nm is preferably 50% or less. With respect to 100 parts by weight of the acrylic polymer, the adhesive sheet may contain 0.1-10 parts by weight of the ultraviolet absorber. The acrylic polymer of the adhesive sheet may contain a polyfunctional monomer component having two or more polymerizable functional groups in one molecule as a monomer component.

In the state where the first release layer of the first release film is in contact with the first main surface of the photocurable adhesive composition layer, the photocurable adhesive composition is exposed to light from the side of the first release film. Irradiate to obtain an adhesive sheet with a release film. The photocurable adhesive composition contains an acrylic material, an ultraviolet absorber, and a photopolymerization initiator. As the acrylic material contained in the photocurable adhesive composition, acrylic monomers and partial polymers thereof may be mentioned. The acrylic material may include both acrylic monomers and partial polymers of acrylic monomers.

In one embodiment, light is irradiated from the side of the first release film to the laminate with the photocurable adhesive composition layer sandwiched between the first release film and the second release film to combine the photocurable adhesive The material is cured by light to obtain an adhesive sheet with a release film temporarily attached to both sides. In an adhesive sheet with a release film temporarily attached to both sides, the peeling force (peel strength) of the first release film and the adhesive sheet can be greater than the peeling force of the second release film and the adhesive sheet. [Effects of Invention]

Adhesive sheets with high visible light transmittance and ultraviolet cut-off properties are suitable for use as optical adhesive sheets for display devices or input devices for displays that require ultraviolet cut-off properties. Since the adhesive sheet with a release film of the present invention suppresses excessive increase in the peeling force of the adhesive sheet and the first release film, the workability of peeling the release film from the adhesive sheet and bonding the adhesive sheet and the adherend is excellent.

The adhesive sheet with release film of the present invention has release films temporarily adhered to both sides of the adhesive sheet. The so-called "temporary adhesion" means the state of peeling and attaching. FIG. 1 is a cross-sectional view of an adhesive sheet 1 with release films 10 and 20 temporarily attached to both sides of an adhesive sheet 50. The adhesive sheet 50 is one in which the adhesive is formed into a sheet shape. 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 in accordance with JIS K7136.

The adhesive sheet 50 is an acrylic adhesive containing a light-curing acrylic polymer. The acrylic adhesive sheet contains a light-curing adhesive by combining a partial polymer (prepolymer) containing an acrylic monomer and/or acrylic polymer, and a photopolymerization initiator. The curable adhesive composition is coated in a layered form and photocured to obtain it. In this specification, "photocurable" adhesive refers to an adhesive that contains a compound containing a photopolymerizable functional group such as a vinyl group or (meth)acryloyl group and can be photocured. "Photocurable" "photocured)" adhesive refers to the adhesive after photocuring the photocurable adhesive. Furthermore, in the adhesive after polymerizing the photocurable adhesive, when a part of the photopolymerizable compound does not react and remains, there are cases where the adhesive is both photocured and photocurable. (photocurable) situation.

[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.

(Monomer component) As the acrylic monomer, an alkyl (meth)acrylate whose alkyl group has 1 to 20 carbon atoms is suitably used. The alkyl group of the alkyl (meth)acrylate may have branches. The content of the alkyl (meth)acrylate relative to the total amount of monomer components of the acrylic material is preferably 40% by weight or more, more preferably 50% by weight or more, and even more preferably 60% by weight or more.

In addition to the alkyl (meth)acrylate, it may also contain high-polarity monomers such as hydroxyl-containing monomers or nitrogen-containing monomers as copolymerization components. By making the acrylic polymer contain high-polarity monomer units, the cohesive force of the adhesive is increased to improve the adhesion of the adhesive sheet to the adherend, and the turbidity of the adhesive under the high temperature and high humidity environment is suppressed, and the adhesive sheet The tendency to increase transparency.

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

Examples of nitrogen-containing monomers include: N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperidone, vinylpyrrolidone, Vinyl monomers such as vinyl pyrrole, vinyl imidazole, vinyl azole, vinyl oxoline, (meth) acryloline, N-vinyl carboxamide, N-vinyl caprolactam, etc. ; Or cyanoacrylate monomers such as acrylonitrile and methacrylonitrile. The nitrogen-containing monomer is preferably one having a cyclic structure containing a nitrogen atom, and among them, a lactam-based 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, and still more preferably 3 to 30% by weight relative to the total amount of monomer components.

As the comonomer component, monomers other than the above-mentioned monomers such as carboxyl group-containing monomers, cyclic ether group-containing monomers, and silane-based monomers may be included.

The comonomer component may include 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; or one C=C bond and epoxy group, aziridinyl group, and oxazoline in one molecule Compounds with polymerizable functional groups such as hydrazine group, hydrazine group, and methylol group. Among them, a polyfunctional polymerizable compound having two or more C=C bonds in one molecule is preferred. The polyfunctional polymerizable compound may be present in the adhesive composition as a monomer or oligomer, and may also be bonded to a functional group such as a hydroxyl group 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 tetra(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate Base) acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, Multifunctional (meth)acrylate (ester compound of polyol and (meth)acrylic acid) such as tetramethylolmethane tri(meth)acrylate. The polyfunctional (meth)acrylate may have a (meth) at the end of the polymer chain such as epoxy (meth)acrylate, polyester (meth)acrylate, (meth)acrylate urethane, etc. Acrylic based.

The amount of the polyfunctional monomer used varies depending on the molecular weight or the number of functional groups, and relative to the total amount of monomer components, it is preferably 5% by weight or less, more preferably 3% by weight or less, and still more preferably 2% by weight or less. Relative to the total amount of monomer components, the usage amount of the multifunctional monomer can be 0.001% by weight or more, 0.01% by weight or more, or 0.05% by weight or more.

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

The 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 composition for forming a prepolymer may contain all the monomer components constituting the acrylic polymer, or may include only a part of the monomers constituting the acrylic polymer. When the monomer components constituting the acrylic polymer include monofunctional monomers and polyfunctional monomers, it is also possible to add a polyfunctional monomer to a prepolymer composition formed by partially polymerizing only the monofunctional monomer. Prepare the adhesive composition. By adding a polyfunctional monomer to a prepolymer composition obtained by partially polymerizing only a monofunctional monomer for post-polymerization, the crosslinking points generated by the polyfunctional monomer can be uniformly introduced into the polymer. The composition for forming a prepolymer may contain a part of the polyfunctional monomer component constituting the acrylic polymer, and after polymerizing the prepolymer, the remaining part of the polyfunctional monomer component may be added to perform post-polymerization.

Prepolymers can also be prepared by polymerization in more than 2 stages or more than 3 stages. For example, after prepolymerizing only a monofunctional monomer, a polyfunctional monomer is added and partially polymerized to prepare a prepolymer composition, and a monomer component or the like may be further added to perform post-polymerization as necessary.

The polymerization method of the prepolymer is not particularly limited. From the viewpoint of self-adjusting the reaction time so that the molecular weight (polymerization rate) of the prepolymer is within the desired range, photopolymerization by irradiation with active light such as ultraviolet rays is preferred. In the case of photopolymerization, the composition for forming a prepolymer preferably contains a photopolymerization initiator. Specific examples of the photopolymerization initiator will be described below.

In addition to the monomer component and the polymerization initiator, the composition for forming a prepolymer may optionally contain a chain transfer agent and the like. The chain transfer agent has the function of receiving free radicals from the growing polymer chain to stop the elongation of the polymer, and the chain transfer agent that has received the free radicals attacks the monomer to start the polymerization again. By using a chain transfer agent, the excessive increase in molecular weight can be suppressed without reducing the concentration of free radicals in the reaction system. As the chain transfer agent, α-thioglycerol, lauryl mercaptan, glycidyl mercaptan, thioglycolic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolic acid, 2,3 -Thiols such as dimercapto-1-propanol.

The polymerization rate of the prepolymer is not particularly limited. In order to have a viscosity suitable for coating on the support, it is preferably 3-50%, more preferably 5-40%. The polymerization rate of the prepolymer can be adjusted to a desired range by adjusting the type or amount of the photopolymerization initiator, the irradiation intensity of active rays such as ultraviolet rays, and the irradiation time. The polymerization rate was calculated by the following formula based on the weight before and after heating (drying) of the prepolymer composition when the prepolymer composition was heated at 130°C for 3 hours. In addition, in the case of partial polymerization by solution polymerization, the amount obtained by subtracting the solvent amount from the total weight of the prepolymer composition is used as the weight before heating in the following formula to calculate the polymerization rate. Polymerization rate (%)=100×(weight after heating/weight before heating)

<Preparation of light-curing adhesive composition> By mixing the remaining monomer components, ultraviolet absorbers, photopolymerization initiators, and other additives to the above-mentioned photopolymerizable acrylic material (monomers and/or partial polymers thereof), the photocurability is obtained Adhesive composition. The photocurable adhesive composition preferably contains the above-mentioned polyfunctional monomer as the remaining monomer component.

<Ultraviolet absorber> Examples of the ultraviolet absorber include: benzotriazole-based ultraviolet absorber, benzophenone-based ultraviolet absorber, tri-methanone-based ultraviolet absorber , salicylate-based ultraviolet absorber, and cyanoacrylic acid Ester-based ultraviolet absorbers, etc. In order to easily obtain acrylic adhesives with high ultraviolet absorption, excellent compatibility with acrylic polymers, and high transparency, three-type ultraviolet absorbers and benzotriazole-type ultraviolet absorbers are preferred. , Preferably a triple-type ultraviolet absorber containing a hydroxyl group, and a benzotriazole-type ultraviolet absorber having one benzotriazole skeleton in one molecule.

A commercially available product can be used as the ultraviolet absorber. As a commercially available product of a tri-based ultraviolet absorber, for example: 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-tris-2-yl)- The reaction product of 5-hydroxyphenyl and [(alkoxy)methyl]oxirane ("TINUVIN 400" manufactured by BASF), 2-(2,4-dihydroxyphenyl)-4,6- The reaction product of bis-(2,4-dimethylphenyl)-1,3,5-tris and glycidyl (2-ethylhexyl) ester (``TINUVIN 405'' manufactured by BASF), (2 ,4-Bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-tris ("TINUVIN 460" manufactured by BASF ), 2-(4,6-diphenyl-1,3,5-tris-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-tris (manufactured by BASF 「TINUVIN 479」), 2,4-bis-[{4-(4-ethylhexyloxy)-4-hydroxy}-phenyl]-6-(4-methoxyphenyl)-1,3 ,5-tris ("Tinosorb S" made by BASF), 2-(4,6-diphenyl-1,3,5-tris-2-yl)-5-[2-(2-乙(Methylhexyloxy)ethoxy]-phenol ("ADK STAB LA-46" manufactured by ADEKA), etc.

Examples of commercially available benzotriazole-based ultraviolet absorbers include: 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4 -(1,1,3,3-Tetramethylbutyl)phenol ("TINUVIN 928" made by BASF), 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotris Azole ("TINUVIN PS" manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (manufactured by BASF) "TINUVIN 900"), 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetra Methylbutyl)phenol ("TINUVIN 928" manufactured by BASF), 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol ("TINUVIN 928" manufactured by BASF), TINUVIN 571''), 2-(2H-benzotriazol-2-yl)-p-cresol ("TINUVIN P" manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4 -6-Bis(1-methyl-1-phenylethyl)phenol ("TINUVIN 234" manufactured by BASF), 2-[5-chloro(2H)-benzotriazol-2-yl]-4 -Methyl-6-(tertiary butyl)phenol ("TINUVIN 326," manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-ditertiary pentylphenol ("TINUVIN 328" made by BASF), 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol ("TINUVIN 328" made by BASF) TINUVIN 329''), phenylpropionic acid and 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy (C7-9 side chain and straight chain Alkyl) ester compound ("TINUVIN 384-2" manufactured by BASF), 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl) The reaction product of methyl propionate and polyethylene glycol ("TINUVIN 1130" manufactured by BASF), 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4- The reaction product of methyl hydroxyphenyl) propionate and polyethylene glycol 300 ("TINUVIN 213" manufactured by BASF), 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalein) Dimethyliminomethyl)-5-methylphenyl]benzotriazole ("Sumisorb250" manufactured by Sumitomo Chemical), etc.

The content of the ultraviolet absorber in the photocurable adhesive composition is preferably 0.1-10 parts by weight, more preferably 0.3-7 parts by weight, and still more preferably 0.5-5 parts by weight, relative to 100 parts by weight of the monomer components . By keeping the content of the ultraviolet absorber within the above-mentioned range, the decrease in transparency caused by the exudation of the ultraviolet absorber, etc., can be suppressed, and the ultraviolet cut-off property of the adhesive sheet can be improved. Moreover, if the content of the ultraviolet absorber is within the above-mentioned range, the decrease 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 photo-radical generator that generates free radicals by visible light or ultraviolet light with a wavelength shorter than 450 nm.

If a UV absorber is included in the photocurable adhesive composition, a part of the irradiated light for photocuring will be absorbed by the UV absorber. In order to promote the generation of free radicals caused by the cleavage of the photopolymerization initiator and increase the polymerization rate, it is preferable to use a photopolymerization initiator with sensitivity in the wavelength region where the absorption of the ultraviolet absorber is small. Specifically, the photopolymerization initiator is preferably one having sensitivity to wavelengths longer than 380 nm, and more preferably one having sensitivity to wavelengths longer than 400 nm. It is preferable to use a photopolymerization initiator having an absorption coefficient of 1×10 ² [mLg ^-1 cm ^{-1] or more at a wavelength of 405 nm.} The photopolymerization initiator with long-wavelength light sensitivity can also have sensitivity to light with a wavelength below 400 nm.

As a specific example of a photopolymerization initiator having a light sensitivity with a wavelength of 400 nm or more, there may be mentioned: 2,4,6-trimethylbenzyl diphenyl phosphine oxide ("Lucirin TPO" manufactured by BASF) ), 2,4,6-trimethylbenzylphenyl ethoxy phosphine oxide ("Lucirin TPO-L" manufactured by BASF) and other phosphine oxides; 2-benzyl-2-dimethyl Amino-1-(4-𠰌linephenyl)butanone-1 ("Irgacure 369" manufactured by BASF) and other amino ketones; bis(2,4,6-trimethylbenzyl) -Phenyl phosphine oxide ("Irgacure 819" made by BASF), 2,2-Dimethoxy-1,2-diphenylethane-1-one ("Irgacure 651" made by BASF), double (2,6-Dimethoxybenzyl)-2,4,4-trimethylpentyl phosphine oxide ("CGI403" manufactured by BASF Corporation) and other bis-amino phosphine oxides.

As the photopolymerization initiator, it can be those with long-wavelength photosensitivity and those without long-wavelength photosensitivity (for example, those whose absorbance coefficient at a wavelength of 405 nm is less than 1×10 ² [mLg ^-1 cm ^-1 ]) Useful.

系光聚合起始劑、醯基氧化膦系光聚合起始劑、二茂鈦系光聚合起始劑等。Examples of photopolymerization initiators that do not have long-wavelength photosensitivity include: benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, and photopolymerization initiators. Active oxime-based photopolymerization initiator, benzoin-based photopolymerization initiator, benzophenone-based photopolymerization initiator, benzophenone-based photopolymerization initiator, ketal-based photopolymerization initiator, 9-oxygen Sulfur

It is a photopolymerization initiator, an phosphine oxide-based photopolymerization initiator, a titanocene-based photopolymerization initiator, etc.

The content of the photopolymerization initiator in the photocurable adhesive composition is preferably 0.02-10 parts by weight, more preferably 0.05 to 5 parts by weight. If the photopolymerization initiator is too small, the polymerization rate may become insufficient. If the photopolymerization initiator is too much, the molecular weight of the polymer may be low, and the adhesive force of the adhesive may become insufficient.

As mentioned above, a photopolymerization initiator can also be used in the preparation (partial polymerization) of the prepolymer. The photopolymerization initiator used for partial polymerization may be the same as or different from the photopolymerization initiator added to the photocurable adhesive composition. The composition for forming the prepolymer does not contain an ultraviolet absorber, and when an 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 partial polymerization can be directly used as the photopolymerization initiator in the photopolymerizable adhesive composition.

Considering the utilization efficiency of irradiated light, etc., it is preferable that the ultraviolet absorber is not contained in the prepolymer forming composition, and the ultraviolet absorber is added to the partially polymerized prepolymer composition. For example, it is preferable to use a photopolymerization initiator that does not have long-wavelength photosensitivity as the polymerization initiator to be added first, to perform partial polymerization, and to add an ultraviolet absorber to the partially polymerized composition and as a post-polymerization initiator. The starter is a photopolymerization initiator with long-wavelength photosensitivity to prepare a photocurable adhesive composition. After the photocurable adhesive composition is coated on the substrate in a layered form, post-polymerization is performed.

＜Other ingredients＞ The photocurable adhesive composition may also contain a chain transfer agent. The chain transfer agent contained in the photocurable adhesive composition is not particularly limited. For example, the above-mentioned chain transfer agent can be used.

In order to adjust the adhesive force or viscosity of the adhesive, the photocurable adhesive composition may also contain various oligomers. As the oligomer, for example, those having a weight average molecular weight of about 1,000 to 30,000 are used. As the oligomer, an acrylic oligomer is preferred in terms of excellent compatibility with the acrylic polymer.

In addition to the above components, the photocurable adhesive composition may also contain additives such as a silane coupling agent, a crosslinking agent, an adhesion imparting agent, a plasticizer, and a softening agent. In addition, the adhesive composition may contain additives such as deterioration inhibitors, fillers, colorants, antioxidants, surfactants, and antistatic agents within a range that does not affect the characteristics 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, the addition of various polymers such as tackifier additives or polyfunctional monomers, the polymerization rate of the prepolymer, and the like. In the photocurable adhesive composition, the content of acrylic monomer components (acrylic monomers and partial polymers of acrylic monomers) is preferably 50% by weight or more, more preferably 70% by weight or more, and more preferably It is 80% by weight or more.

[Formation of Adhesive Sheet] The photocurable adhesive composition is coated on the support, or an adhesive composition layer is formed between the support and the cover sheet, and the adhesive composition is irradiated with active energy rays to perform photocuring, thereby obtaining adhesion piece. As the coating method of the adhesive composition, for example: roll coating, touch roll coating, gravure coating, reverse coating, roll brush coating, spray coating, dip roll coating, bar coating , Knife coating, air knife coating, curtain coating, die lip coating, die nozzle coating.

The coating thickness of the photocurable adhesive composition (the thickness of the adhesive sheet 50) is not particularly limited, and is, for example, about 10 to 500 μm. In order to improve the ultraviolet absorption of the adhesive sheet, the thickness of the adhesive sheet is preferably 50 μm or more. The light transmittance of the adhesive sheet 50 at a wavelength of 380 nm is preferably 50% or less, more preferably 30% or less, still more preferably 10% or less, and may also be 5% or less or 3% or less.

An adhesive sheet can be obtained by irradiating ultraviolet and/or short-wavelength visible light to a laminate having a photocurable acrylic adhesive composition layer on a supporting base material to perform photocuring. In the case of photocuring by irradiating light to the laminate formed by sandwiching the photocurable adhesive composition layer between the support substrate and the cover sheet, it can be from either the support substrate side or the cover sheet side Light irradiation can also be carried out from both sides. As described in detail below, in the present invention, the release film 10 provided with a specific release layer 15 is used as a supporting substrate or a cover sheet attached to the light-irradiated surface side of the adhesive sheet.

In order to increase the curing speed, the light irradiation intensity is preferably 5 mW/cm ² or more. In order to sufficiently increase the molecular weight of the acrylic polymer after light curing and ensure the retention at high temperature, the light irradiation intensity is preferably 20 mW/cm ² or less.

The cumulative amount of irradiated light is preferably about 100 to 5000 mJ/cm ² . As the light source for light irradiation, it 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. It is preferable to use an LED light source, a high-pressure mercury lamp, or an ultra-high pressure light source. 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. In order to suppress the low molecular weight caused by the increase in temperature, and to increase the utilization efficiency and curing speed of the irradiated light, it is preferable to irradiate the ultraviolet absorber to absorb light in a relatively small wavelength region. It is preferable to use an LED light source because the heat dissipation from the light source is less and light with a smaller wavelength width can be irradiated. When using an LED light source, the emission peak wavelength is preferably 350 nm or more, and can also be 360 nm or more, 380 nm or more, or 400 nm or more.

The final polymerization rate of the monomer components of the adhesive sheet after light curing is preferably 90% or more, more preferably 95% or more, and still more preferably 98% or more. The gel fraction of the adhesive sheet is preferably 50% or more, more preferably 75% or more, and still more preferably 85% or more.

[Release film] As a support substrate for coating the adhesive composition and a cover sheet attached to the surface of the coating layer of the adhesive composition, it is used on the contact surface with the coating layer (adhesive sheet) of the adhesive composition. Type layer of release film. In the present invention, a release film (first release film) 10 provided with a specific first release layer 15 is attached to the first main surface (light irradiation surface side) of the photocurable adhesive composition layer 55 Light hardening is carried out under the following conditions. A release film (second release film) 20 having a second release layer 25 is attached to the second main surface of the photocurable adhesive composition layer 55.

＜Film base material＞ As the film base materials 11 and 21 of the release films 10 and 20, various resin films having transparency are used. Examples of resin materials include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, acetate resins, polyether ether resins, polycarbonate resins, and polyamides. Amine resins, polyimide resins, polyolefin resins, (meth)acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl alcohol resins, Polyarylate resin, polyphenylene sulfide resin, etc. Among them, particularly preferred are polyester resins such as polyethylene terephthalate. The thickness of the film substrates 11 and 21 is preferably 10 to 200 μm, more preferably 25 to 150 μm.

＜Release layer＞ As the material of the release layers 15 and 25, silicone-based resins, long-chain alkyl-based resins, fatty amide resins, etc. may be mentioned. These resins may contain fluorine atoms in the side chain of the polymer. For example, the silicone resin may be a fluorinated silicone resin containing fluorine atoms in the side chain.

The silicone release agent used to form the silicone release layer is roughly classified into condensation type silicone release agent and Addition type silicone release agent.

In the formation of the addition-type silicone-based release layer, a silicone-based resin composition that is cured by an addition reaction is used. The type of silicone resin composition that is cured by addition reaction preferably includes a polyorganosiloxane resin having an alkenyl group such as a vinyl group or a hexenyl group, and a polyorganosilicon having a hydrosilyl group (SiH) The oxane compound (crosslinking agent) further includes a curing catalyst (hydrosilation catalyst). The silicone resin composition is heated to form a peelable coating (release layer) by the reaction between the alkenyl group of the polyorganosiloxane resin and the hydrosilyl group of the crosslinking agent (hydrosilation reaction).

Examples of polyorganosiloxanes include polyalkylalkylsiloxanes such as polydimethylsiloxane, polydiethylsiloxane, and polymethylethylsiloxane; polyalkylaryl groups. Silicone; poly(dimethylsiloxane-diethylsiloxane, etc.) Among them, polydimethylsiloxane is preferred. Polyorganosiloxane may be one Si atom bonded with plural Kind of organic base.

The crosslinking agent is a polyorganosiloxane having a hydrosilyl group, and preferably has two or more silicon atoms having Si-H bonds in one molecule. As the polyorganosiloxane having a hydrosilyl group, it is preferably polymethylhydrosiloxane or poly(dimethylsiloxane-methylhydrosiloxane), or polydimethylsiloxane terminated with hydrosilyl group. Silicone etc.

Commercial products in which a polyorganosiloxane resin having an alkenyl group and a polyorganosiloxane compound having a hydrosilyl group are mixed in advance can also be used. Examples of commercially available products containing polyorganosiloxane resins having alkenyl groups and polyorganosiloxane compounds having hydrosilyl groups include: "KS-847" and "X-62-2829 manufactured by Shin-Etsu Chemical Co., Ltd." ", and "SRX211", "LTC761" and "LTC300B" manufactured by Toray Dow Corning Corporation.

As the catalyst for the addition reaction (hydrosilation reaction), a platinum-based catalyst is preferred. Examples of platinum-based catalysts include chloroplatinic acid, platinum olefin complexes, and chloroplatinic acid olefin complexes.

In the formation of the condensed silicone-based release layer, a silicone-based resin composition that is cured by a condensation reaction is used. As a type of silicone resin composition that is cured by a condensation reaction, for example, polyorganosiloxane resins containing silanol groups at the molecular ends, polymethylhydrosiloxanes, cellulose derivatives, and alcohols can be mentioned. Acid resins, etc., further include hardening catalysts.

As the polyorganosiloxane having a silanol group at the molecular end, it is preferable to introduce an alkyl group such as a methyl group or an ethyl group, a phenyl group, or the like as a functional group (organic group) of the side chain. The condensation type silicone resin composition may include an alkoxy-containing polyorganosiloxane that functions as a crosslinking agent.

As the catalyst for the condensation reaction, an organotin catalyst is preferred. Examples of the organotin catalyst include dibutyltin dilaurate, dibutyltin diacetate, and dibutyltin dioctoate.

In the formation of the fluorine-based release layer, a resin composition containing a fluorine-based resin is used. The fluororesin contains fluorine atoms in the side chain portion of the polymer, and specific examples thereof include fluorocarbon resins such as polytetrafluoroethylene, fluorinated silicone resins, and the like. From the viewpoint of releasability from the adhesive sheet, a fluorinated silicone resin is preferred.

The fluorinated silicone resin may be a hardening type or a non-hardening type. The curable fluorinated silicone resin (cured product of the curable fluorinated silicone) is preferred because of its high adhesion to the film substrate and forming a strong film. As the curable fluorinated silicone resin, an addition type silicone is preferred. For example, a part or all of the alkyl group of the side chain of the polyorganosiloxane in the above addition type silicone composition is substituted with a fluorine atom or a fluoroalkyl group.

Examples of commercially available curable fluorinated silicone resins include: "KP-911" and "X-70-201S" manufactured by Shin-Etsu Chemical Industry, and "FS1265-300CS" and "FS1265-300CS" manufactured by Toray Dow Corning Corporation. FS1265-1000CS", "FS1265-10000CS", "BY24-900", "BY24-903", "Syl-off 3062" and "Q2-7785", etc.

The composition for forming the release layer (release agent composition) may contain an organic solvent in addition to the resin component. 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; acetone, methyl ethyl Ketone-based solvents such as base ketones; alcohol-based solvents such as methanol, ethanol, butanol, etc. The organic solvent may also be a mixed solvent.

The release agent composition may optionally contain various additives such as fillers, antistatic agents, antioxidants, plasticizers, and colorants.

The release agent composition is coated on the film substrate, heated and dried, and if necessary, a curing reaction is performed to form a release layer. Examples of coating methods include: roll coating, touch roll coating, gravure coating, reverse coating, roll brushing, spray coating, dipping roll coating, bar coating, blade coating, and air coating. Knife coating, curtain coating, die lip coating, die nozzle coating. As the heating and drying method, hot air drying may be mentioned. The conditions of hot air drying vary depending on the heat resistance of the substrate, and it is usually dried at a temperature of about 80 to 150°C for about 10 seconds to 10 minutes. In order to promote the curing reaction, etc., heat treatment and ultraviolet irradiation and other active energy rays may be used as necessary.

As described above, when the photocurable adhesive composition layer 55 is photocured, light is irradiated from the side of the first release film 10. The first release layer 15 of the first release film 10 is preferably a fluorine-based release layer or a condensed silicone release layer. The silicone resin of the condensed silicone release layer can be fluorine-based or non-fluorine-based. When the first release layer 15 is a fluorine-based release layer or a condensed silicone release layer, compared to the use of a release film with a non-fluorine-based addition type silicone release layer, there is a difference The peeling force of hardened adhesive sheets tends to decrease.

The second release layer 25 of the second release film 20 is not particularly limited. In order to exhibit a moderate peeling force, it is preferably a non-fluorine-based addition molded silicone release layer. The first release layer 15 of the first release film 10 (heavy release film) on the light irradiation surface is a fluorine-based release layer or a condensed silicone release layer, and the second release film 20 (light release film) on the opposite side When the second release layer 25 of the film) is a non-fluorine-based addition type silicone release layer, the following adhesive sheet with a release film can be obtained, and the first release film 10 is easily self-curing from the light-curing adhesive layer 50 peeling, and the balance between the peeling force of the first release film and the peeling force of the second release film is more appropriate.

[Releasability of release film and adhesive sheet] In an adhesive sheet with a release film temporarily attached to both sides of the adhesive sheet, usually, the peeling force of the adhesive sheet and one of the release films is compared to the peeling force of the adhesive sheet and the other release film ,Relatively small. When using the adhesive sheet, peel off the release film with low peel strength (low peel film) from the adhesive sheet, and bond it with the first adherend, and then remove the release film with relatively large peel strength (heavy peeling) The film is peeled off, and it is bonded to the second adherend. By making the release film temporarily adhered to the front and back of the adhesive sheet have different peeling forces, the light peeling film can be selectively peeled off when attaching to the first adherend, so the workability of attaching can be improved.

In light-curing adhesive sheets, since the adhesive strength of the adhesive before and after light curing is different, considering the adhesive properties of the light-curing adhesive sheet, adjust the adhesion between the light release film and the heavy release film and the adhesive sheet (peelability) ). When the adhesive composition does not contain ultraviolet absorbers, the relationship between the peeling force of one release film and the other release film will not change before and after photocuring. In contrast, when the UV absorber is included in the photocurable adhesive composition, the increase in the peeling force of the first release film 10 on the side where the light is irradiated is significantly greater than that of the second release film on the opposite side. The tendency of the peeling force of the release film 20 to increase.

Therefore, in the adhesive sheet with a release film, it is preferable to set the first release film 10 on the light-irradiated side as a heavy release film, and set the second release film 20 on the opposite side as a light release film. That is, it is preferable that the peeling force of the first release film 10 and the adhesive sheet 50 is greater than the peeling force of the second release film 20 and the adhesive sheet 50.

As described above, the light irradiation to the adhesive composition may be performed from either side of the support substrate side and the cover sheet side, or light irradiation may be performed from both sides. When light is irradiated from the supporting substrate side, as the supporting substrate to be coated with the adhesive composition, the first release film 10 provided with the above-mentioned first release layer 15 may be used. When light is irradiated from the cover sheet side, as the cover sheet attached to the adhesive composition layer 55, the first release film 10 provided with the above-mentioned first release layer 15 may be used.

In the case of irradiating light from both sides, the above-mentioned first release film may be used for either of the supporting base material or the cover sheet. It is also possible to use a release film with a fluorine-based release layer or a condensed silicone release layer for both the support substrate and the cover sheet. As described in Japanese Patent Laid-Open No. 2014-65754, when conveying on a passing route that reverses the conveying direction and irradiating both sides with light, it is better to use the above for the first irradiated surface. Release film.

If the peeling force of the first release film 10 (heavy release film) and the adhesive sheet 50 is too large, the first release film will be peeled off from the surface of the adhesive sheet 50 with the adhesive sheet 50 attached to the first adherend. At 10 o'clock, some defects such as deformation or whitening of the adhesive sheet, peeling of the adhesive sheet from the adherend, etc. sometimes occur. The peel strength (peel strength) between the adhesive sheet 50 and the first release film 10 after photocuring is preferably 0.1-1 N/50 mm, more preferably 0.2-0.8 N/50 mm, and still more preferably 0.3-0.7 N/50 mm. The peeling force of the release film and the adhesive sheet is the measured value obtained by the 180° peeling test at a tensile speed: 0.3 m/min. As described above, when the release layer 15 of the first release film 10 is a fluorine-based release layer or a condensed silicone release layer, the adhesive sheet 50 and the first release film 10 after photocuring can be suppressed Excessive increase of the peeling force.

When the UV absorber is included in the photocurable adhesive composition, the reason for the increase in the peeling force of the release film on the light-irradiated side is not clear, but it is assumed to be related to the unreacted reactive functional group in the release layer. It is related to the reaction of the compounds in the 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. If the ultraviolet absorber absorbs light, the light energy will be converted into heat energy and the temperature will rise. Especially in the vicinity of the interface between the release layer of the release film and the adhesive composition layer on the side of the light irradiated surface, the temperature tends to rise due to the large amount of light absorption of the ultraviolet absorber. If the temperature rises under light irradiation, in addition to the photohardening reaction, the thermal hardening reaction also proceeds easily. Therefore, it is considered that the adhesive force (peeling force) is improved by the reaction between the unreacted heat-reactive functional group in the release layer 15 and the compound in the adhesive composition.

As shown in the following reference example, if the release film whose peel strength is increased by the light curing of the adhesive is temporarily peeled from the adhesive sheet (the peel strength at this time is set as the first peel strength F1), the same or the same type of release The film was attached to the pressure-sensitive adhesive sheet again, and a peel test was performed (the peel strength at this time was referred to as the second peel strength F2), and the second peel strength F2 was smaller than the first peel strength F1. Based on the above, it is believed that the formation of chemical bonds during photocuring is the cause of the increased adhesion between the release layer and the adhesive layer.

It is believed that the condensed silicone resin constituting the condensed silicone release layer has fewer or no thermally reactive functional groups such as alkenyl groups, so the temperature rises due to the light absorption of the ultraviolet absorber even during light curing. In this case, it is also difficult to generate a reaction between the compound in the adhesive composition layer 55 and the functional group in the release layer 15, which can prevent excessive increase in the peeling force.

It is believed that the fluorine-based resin constituting the fluorine-based release layer has a small surface free energy, so the interaction between the more reactive functional groups in the adhesive composition and the release layer is small, and it is difficult to produce chemical reactions at the interface. And so on, help to suppress the increase in peeling force.

As described above, the first peel strength F1 when the first release film 10 is peeled from the photocurable adhesive sheet 50 is preferably 0.1 to 1 N/50 mm. When the first release film 10 is peeled from the photocurable adhesive sheet 50, and the same or the same type of release film is attached again for peeling, the second peel strength F2 is preferably less than F1. F1/F2 is preferably 3 or less. F1/F2 is usually 0.5 or more. F1/F2 is more preferably 0.7 to 2.5, and still more preferably 0.8 to 2.0.

[Use of Adhesive Sheet] The above-mentioned photocurable adhesive sheet has high visible light transmittance and ultraviolet cutoff properties, so it is suitable for use as an optical adhesive for display devices or display input devices that require ultraviolet cutoff properties. The display device may, for example, be a liquid crystal display device, an organic EL (electroluminescence) display device, a PDP (Plasma Display Panel), electronic paper, and the like. As the input device, a touch panel can be mentioned. In addition, the above-mentioned light-curing adhesive sheet can also be used for bonding a display device and an input device, bonding to a transparent plate disposed on the surface of the display device or the input device, and the like.

When using an adhesive sheet with a release film temporarily attached on both sides, first peel off the light release film (second release film 20) to expose the second main surface of the adhesive sheet 50, and then adhere to the first Be considerate. After that, the heavy release film (the first release film 10) is peeled to expose the first main surface of the adhesive sheet 50, and then it is bonded to the second adherend. It can also be attached to the adherend after peeling off the release film on both sides. When the adhesive sheet has photocuring properties, light can be irradiated to the adhesive sheet after being bonded to the adherend. By light-curing the adhesive sheet after being bonded to the adherend, the reliability of the adhesion with the adherend can be improved. [Example]

The following examples and comparative examples are taken as examples to describe the present invention in more detail, but the present invention is not limited by these examples.

[Preparation of Adhesive Composition] To contain 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 To the monomer mixture, add 1-hydroxycyclohexyl phenyl ketone ("Irgacure 184" manufactured by BASF) as a photopolymerization initiator: 0.035 parts by weight, and 2,2-dimethoxy-1,2- Diphenylethane-1-one ("Irgacure 651" manufactured by BASF): 0.035 parts by weight. The composition was irradiated with ultraviolet rays and prepolymerized until the viscosity at room temperature became about 20 Pa·s, and a prepolymer with a polymerization rate of about 8% was obtained.

To 100 parts by weight of the prepolymer composition, respectively add: polyester urethane diacrylate with a weight average molecular weight of 12,500 ("Artresin UN-350" manufactured by Negami Kogyo): 2 parts by weight, acrylic oligomer : 5 parts by weight; UV absorber ("Tinosorb S" manufactured by BASF): 0.70 parts by weight; as a photopolymerization initiator "Irgacure 184" manufactured by BASF: 0.05 parts by weight, "Irgacure 651 manufactured by BASF" ": 0.05 parts by weight, and "Irgacure 819" manufactured by BASF: 0.40 parts by weight; α-methylstyrene dimer as a chain transfer agent ("Nofmer MSD" manufactured by NOF Corporation): 0.07 parts by weight; And "KBM-403" manufactured by Shin-Etsu Chemical as a silane coupling agent: 0.3 parts by weight, and then uniformly mixed these to prepare a photocurable adhesive composition. The above-mentioned acrylic oligomer uses an oligomer with a weight average molecular weight of 5100 having dicyclopentyl methacrylate and methyl methacrylate (MMA) as monomer components in a weight ratio of 60:40.

[Production of Release Film A] Diluted by a mixed solvent of toluene and hexane in a volume ratio of 1:1: Non-fluorine-based addition type silicone composition containing polyorganosiloxane with hexenyl group ("LTC761" manufactured by Toray Dow Corning Corporation): 30 parts by weight, silicone dispersion ("BY 24-850" manufactured by Toray Dow Corning): 0.9 parts by weight, and platinum catalyst for curing silicone ("SRX 212" manufactured by Toray Dow Corning): 2 parts by weight Part, prepare the release agent solution. Coat the solution on one side of a biaxially stretched polyester film with a thickness of 75 μm and heat it with a hot air dryer at 130°C for 1 minute to produce a release layer with a non-fluorine-based addition type silicone release layer on one side of the polyester film. Type film A.

[Comparative Example 1] In Comparative Example 1, the above-mentioned release film A was used for the support release film and the cover release film, respectively. On the release layer forming surface supporting the release film, the adhesive composition was coated with a thickness of 300 μm to form a coating layer, and the coating layer was attached to the surface of the coating layer to cover the release film to obtain a laminate. On the laminate, use a black light lamp whose position is adjusted so that the irradiation intensity of the irradiation surface directly below the lamp becomes 5 mW/cm ² , and irradiate ultraviolet rays from the side of the release film to be photo-cured to obtain a photo-curing adhesive Adhesive sheets with release film on both sides of the layer.

[Example 1] As a cover release film, a release film with a fluorine-based addition type silicone release layer on one side of the polyester film ("FSC6" manufactured by Nippa) is used instead of the release film A. Otherwise, in the same manner as in Comparative Example 1, an adhesive sheet having a release film on both sides of the photocurable adhesive layer was obtained.

[Example 2] As a cover release film, a release film with a non-fluorine-based condensation type silicone release layer on one side of the polyester film (SR(S)" manufactured by Nippa Corporation) is used instead of the release film A. Otherwise, in the same manner as in Comparative Example 1, an adhesive sheet having a release film on both sides of the photocurable adhesive layer was obtained.

[Reference example 1] In Comparative Example 1 and Examples 1 and 2, UV irradiation was carried out from the opposite side, that is, the side supporting the release film, to harden the coating layer to obtain adhesion with release film on both sides of the photocurable adhesive layer piece.

[Peelability evaluation] ＜Peel strength of release film＞ Cut the adhesive sheet with the release film into a width of 50 mm, and use a tensile testing machine at a temperature of 23°C to perform a 180° peel test at a tensile speed of 0.3 m/min to measure the peeling of the cover release film from the adhesive sheet Time peel strength. That is, for the samples of Comparative Example 1 and Examples 1 and 2, the peeling strength of the release film on the light-irradiated side was measured, and for Reference Example 1, the peeling of the release film on the side opposite to the light-irradiated surface was measured. strength.

[evaluation result] Table 1 shows the types of the coating release films of the Examples and Comparative Examples and the measurement results of the peel strength of the coating release films.

[Table 1] Cover release film release layer Cover release film peel strength (N/50 mm) Light-irradiated surface The surface opposite to the light irradiated surface (Reference example 1) Comparative example 1 Addition silicone (non-fluorine series) 1.61 0.31 Example 1 Addition silicone (fluorine-based) 0.49 0.29 Example 2 Condensed silicone (non-fluorine-based) 0.40 0.29

In the case of light curing of the adhesive by light irradiation from the supporting release film side (Reference Example 1), no significant difference was found in the peel strength of the covering release film regardless of the type of release film used. In the case of light irradiation from the side of the cover release film, in Comparative Example 1, the peel strength exceeded 1 N/50 mm, and the peel strength was found to increase significantly. On the other hand, in Example 1 using a fluorine-based silicone release film and Example 2 using a condensed silicone release film, compared with Reference Example 1, the peeling strength is increased, but the peeling The strength is less than 0.5 N/50 mm.

[Reference example 2] From the above-mentioned comparative example 1 (using a non-fluorine-based addition type silicone release film as an example of covering the release film), peel off the support release film (light release film) and attach the adhesive sheet To the glass plate. The cover release film (heavy release film) was peeled from the sample, the same type of release film was attached to the adhesive sheet, and pressure was applied with a hand roller. A cut with a width of 5 cm was made in the release film, and the peel strength was measured. The result was 0.20 N/50 mm.

According to the comparison between Comparative Example 1 and Reference Example 1 and Reference Example 2, it is believed that in Comparative Example 1, the effect of improving the adhesion between the release layer and the adhesive layer by light irradiation when the adhesive composition is hardened (for example , The formation of chemical bonds caused by the reaction between the resin component of the release agent and the hardening component in the adhesive, etc.) is stronger, so the peel strength is improved.

On the other hand, it is considered that in Example 1 and Example 2, the residual amount of hardening-reactive functional groups in the resin material constituting the release layer is small. Furthermore, the introduction of fluorine in Example 1 makes the release layer The surface free energy is small, so the adhesion enhancement effect caused by the formation of the chemical bond between the release layer and the adhesive layer is small, and the excessive increase of the peeling strength is suppressed.

1: Adhesive sheet with release film 10: Release film 11: Membrane substrate 15: Release layer 20: Release film 21: Film substrate 25: Release layer 50: Light-curing adhesive layer 55: Light-curing adhesive composition layer

Figure 1 is a cross-sectional view showing the laminated structure of an adhesive sheet with a release film.

1: Adhesive sheet with release film

10: Release film

11: Membrane substrate

15: Release layer

20: Release film

21: Film substrate

25: Release layer

50: Light-curing adhesive layer

55: Light-curing adhesive composition layer

Claims (10)

An adhesive sheet with a release film, comprising: a light-curing adhesive sheet having a first main surface and a second main surface; a first release film temporarily adhered to the first main surface of the adhesive sheet; and temporary adhesion The second release film on the second main surface of the above-mentioned adhesive sheet; The first release film is provided with a first release layer on the first film substrate; The second release film is provided with a second release layer on the second film substrate; The first release layer and the second release layer are respectively connected to the adhesive sheet; The above-mentioned adhesive sheet includes a light-curing acrylic polymer and an ultraviolet absorber; The first release layer is a fluorine-based release layer or a condensed silicone release layer. The adhesive sheet with a release film of claim 1, wherein the peel strength when the first release film is peeled from the adhesive sheet obtained by a 180° peel test at a peeling speed of 0.3 m/min is 0.1 to 1 N/50 mm. For example, the adhesive sheet with release film of claim 1 or 2, wherein the first peel strength F1 and the second peel strength F2 satisfy F1/F2≦3, The first peel strength F1 is the peel strength when the first release film is peeled from the adhesive sheet, The second peel strength F2 is the peeling of the sample after peeling off the first release film from the adhesive sheet, and then bonding the first release layer of the first release film and the adhesive sheet again The peel strength of the above-mentioned first release film. The adhesive sheet with a release film of claim 1 or 2, wherein the peel strength of the first release film from the adhesive sheet is greater than the peel strength of the second release film from the adhesive sheet. The adhesive sheet with release film of claim 1 or 2, wherein the photocurable acrylic polymer contains a multifunctional monomer having two or more polymerizable functional groups in one molecule as a comonomer component. Such as the adhesive sheet with release film of claim 1 or 2, wherein the light transmittance of the adhesive sheet with a wavelength of 380 nm is less than 50%. The adhesive sheet with a release film of claim 1 or 2, wherein the adhesive sheet contains 0.1-10 parts by weight of the ultraviolet absorber with respect to 100 parts by weight of the acrylic polymer. Such as the adhesive sheet with release film of claim 1 or 2, wherein the second release layer is a non-fluorine-based addition type silicone release layer. A method for manufacturing an adhesive sheet with a release film. The adhesive sheet with a release film includes: a light-curing adhesive sheet with a first main surface and a second main surface; temporarily adhered to the first main surface of the adhesive sheet The first release film; and the second release film temporarily adhered to the second main surface of the above-mentioned adhesive sheet; the manufacturing method of the adhesive sheet with the release film includes the following steps: A photocurable adhesive composition containing acrylic monomers and/or acrylic monomers, a UV absorber, and a photopolymerization initiator is layered on the first release film and the first release film Between the two release films, a layered body is formed; and Irradiating the photocurable adhesive composition between the first release film and the second release film with light from the side of the first release film, so that the photocurable adhesive composition is photocured; and The first release film is provided with a first release layer on the surface of the side contacting the photocurable adhesive composition on the film substrate; The second release film is provided with a second release layer on the surface of the side contacting the photocurable adhesive composition on the film substrate; The first release layer is a fluorine-based release layer or a condensed silicone release layer. For example, the method for manufacturing an adhesive sheet with a release film of claim 9, wherein the second release layer is a non-fluorine-based addition type silicone release layer.

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