WO2021060446A1 - Uv硬化型組成物およびそれを用いたuv硬化型シート - Google Patents
Uv硬化型組成物およびそれを用いたuv硬化型シート Download PDFInfo
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- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F279/00—Macromolecular compounds obtained by polymerising monomers on to polymers of monomers having two or more carbon-to-carbon double bonds as defined in group C08F36/00
- C08F279/02—Macromolecular compounds obtained by polymerising monomers on to polymers of monomers having two or more carbon-to-carbon double bonds as defined in group C08F36/00 on to polymers of conjugated dienes
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- C09J7/10—Adhesives in the form of films or foils without carriers
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- C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
- C08J7/04—Coating
- C08J7/043—Improving the adhesiveness of the coatings per se, e.g. forming primers
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- C08L15/00—Compositions of rubber derivatives
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- C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
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- C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
- C08L9/06—Copolymers with styrene
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- C09J109/00—Adhesives based on homopolymers or copolymers of conjugated diene hydrocarbons
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- C09J109/00—Adhesives based on homopolymers or copolymers of conjugated diene hydrocarbons
- C09J109/06—Copolymers with styrene
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- C09J4/00—Adhesives based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; adhesives, based on monomers of macromolecular compounds of groups C09J183/00 - C09J183/16
- C09J4/06—Organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond in combination with a macromolecular compound other than an unsaturated polymer of groups C09J159/00 - C09J187/00
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- C09J7/00—Adhesives in the form of films or foils
- C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
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- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2205/00—Polymer mixtures characterised by other features
- C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
- C08L2205/025—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group containing two or more polymers of the same hierarchy C08L, and differing only in parameters such as density, comonomer content, molecular weight, structure
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- C08L2207/00—Properties characterising the ingredient of the composition
- C08L2207/32—Properties characterising the ingredient of the composition containing low molecular weight liquid component
- C08L2207/324—Liquid component is low molecular weight polymer
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- C09J2301/00—Additional features of adhesives in the form of films or foils
- C09J2301/40—Additional features of adhesives in the form of films or foils characterized by the presence of essential components
- C09J2301/408—Additional features of adhesives in the form of films or foils characterized by the presence of essential components additives as essential feature of the adhesive layer
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- C09J2301/00—Additional features of adhesives in the form of films or foils
- C09J2301/40—Additional features of adhesives in the form of films or foils characterized by the presence of essential components
- C09J2301/416—Additional features of adhesives in the form of films or foils characterized by the presence of essential components use of irradiation
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- C09J2409/00—Presence of diene rubber
Definitions
- the present invention relates to UV (ultraviolet) curable compositions and UV curable sheets, and more particularly to UV curable resin compositions and UV curable sheets that can be suitably used for adhesive sheets, stretchable sheets and the like. ..
- the joining interface When a material is joined, the joining interface is constantly stressed by heat shrinkage, deformation, vibration, and the like. The stress gradually accumulates at the junction interface, eventually causing fracture of the junction interface. In particular, when the materials are different materials, warpage and wrinkles may occur depending on the combination of materials, and the resulting destruction of the material may become a problem. Examples of the method of relieving these stresses include a method of using a soft component such as a plasticizer as an adhesive. Making the adhesive layer flexible means inducing plastic deformation, and by plastically deforming the adhesive layer so as to follow the deformation of the material, the destruction of the material and the adhesive layer is suppressed. ..
- Patent Document 1 describes a radical initiator consisting of (A) a rubber component having a diene skeleton, (B) a monomer and / or oligomer having 6 or more ethylenically unsaturated groups, and (C) an organic peroxide.
- An adhesive composition comprising an agent is disclosed.
- Patent Document 1 describes that an adhesive composition containing rubber, having excellent adhesive strength, and capable of sufficiently suppressing and reducing warpage and wrinkles, and an adhesive sheet using the same can be obtained. There is.
- Patent Document 1 uses an organic peroxide which is a thermal radical initiator as a radical source, a heating step of about 180 ° C. is required for its thermosetting, and it has heat resistance. There was room for improvement in that it was difficult to apply to low-grade adherends.
- Patent Document 2 discloses a method for producing a crosslinked rubber, which comprises subjecting a conjugated diene-based uncrosslinked rubber having an unsaturated bond to a crosslinking reaction by irradiation with active light in the presence of a photopolymerization initiator. There is. It is described that this production method makes it easy to obtain a uniform thin film, has good production efficiency, and the obtained crosslinked rubber has excellent heat resistance and the like as compared with uncrosslinked rubber, and is useful as an adhesive or the like. ing. According to the method of Patent Document 2, a cured product can be obtained at a low temperature and in a short time. Therefore, it is considered that it can be applied to an adherend having low heat resistance because a heating step is not required. However, the crosslinked rubber obtained by this method has a problem that sufficient adhesiveness to the adherend cannot be obtained.
- the present invention has been made in view of the above circumstances, and is a UV-curable composition that can be cured without undergoing a high-temperature heating step and has excellent adhesiveness (adhesive strength), and a UV-curable sheet using the same.
- the purpose is to provide.
- the present inventor has found that in a UV curable composition containing a rubber component having a diene skeleton, a photopolymerization initiator and a cross-linking agent, the rubber component is solid at 25 ° C.
- the above problems can be solved by using a conventional rubber component and a liquid rubber component in combination, and have arrived at the present invention.
- the adhesive composition of the present invention is a UV curable composition, which contains a rubber component having a diene skeleton, a photopolymerization initiator, and a cross-linking agent, and the rubber component having the diene skeleton is It is characterized by containing a solid rubber component and a liquid rubber component at 25 ° C.
- At least one of the solid rubber component and the liquid rubber component preferably contains a modified rubber containing at least one selected from modified butadiene rubber, modified styrene butadiene rubber and modified isoprene rubber.
- the modified rubber preferably contains a rubber modified with at least one selected from a carboxy group, an acid anhydride group, an amino group, an alkoxysilyl group, a hydroxyl group and an epoxy group.
- the modified rubber is preferably a rubber component that is liquid at 25 ° C.
- the blending amount of the liquid rubber is preferably in the range of 3 to 50% by mass ratio with respect to the total amount of the rubber components.
- the solid rubber component it is preferable to contain at least one selected from butadiene rubber and styrene-butadiene rubber.
- the UV curable sheet of the present invention has an adhesive layer formed from any of the above UV curable compositions.
- the thickness of the adhesive layer is preferably 5 to 200 ⁇ m.
- the UV curable sheet preferably has a 90-degree peeling force based on JISK-6854 of 4 N / inch or more after being irradiated with UV having an integrated light intensity of 1600 mJ / cm 2 at room temperature with a high-pressure mercury lamp.
- the UV curable composition or the cured product of the UV curable sheet can be preferably used.
- the gel fraction of the cured product is preferably 50% or more.
- the UV curable sheet according to one aspect of the present invention is a UV curable sheet containing a rubber component having a diene skeleton, and after irradiating UV with an integrated light amount of 1600 mJ / cm 2 at room temperature with a high-pressure mercury lamp.
- the tensile strength at the time of cutting based on JISK-6251 is 3.5 MPa or more in the range of sheet thickness of 25 ⁇ m to 50 ⁇ m.
- the UV curable composition of the present invention can be cured by UV irradiation for a short time, it can be applied not only to an adherend having high heat resistance but also to a wide range of members.
- the cured product obtained from the UV curable composition of the present invention has excellent adhesiveness, is uniform even when thinned, and has high mechanical strength. Therefore, it can be suitably used not only as an adhesive sheet but also as a stretchable sheet.
- ⁇ which represents a numerical value range represents the range including the numerical value described as the upper limit value and the lower limit value, respectively.
- the unit when the unit is described only for the upper limit value in the numerical range, it means that the lower limit value is also the same unit as the upper limit value.
- the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise.
- the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.
- the content or content of each component in the composition refers to the content of each component in the composition when a plurality of substances corresponding to each component are present in the composition, unless otherwise specified. Means the total content or content of a substance.
- the UV curable composition of the present invention contains a rubber component having a diene skeleton, a photopolymerization initiator, and a cross-linking agent, and the rubber component having the diene skeleton is a solid rubber component and a liquid at 25 ° C. Contains the rubber component of.
- a heating step is indispensable because a thermal radical initiator is used as a radical source, and the adhesive composition softened by the heating step is applied to the uneven portion on the surface of the adherend. Excellent adhesiveness was obtained due to the penetration and anchor effect.
- the UV curable composition uses a photoradical initiator as a radical source and is cured by UV irradiation, so that a cured product can be obtained in a short time without going through a heating step.
- the heating step since the heating step is not performed, it is difficult to obtain the anchor effect, and sufficient adhesiveness cannot be obtained.
- the adhesiveness to an adherend can be improved without going through a heating step. It was completed after finding out what it could do. Further, in the UV curable composition of the present invention, a sheet having high mechanical strength and being uniform even when thinned can be obtained.
- UV curable composition of the present invention The components contained in the UV curable composition of the present invention will be described below.
- the UV curable composition of the present invention contains a rubber component having a diene skeleton (hereinafter, also referred to as “component (A)”). Therefore, after curing by UV irradiation, the component (A) is crosslinked and has rubber elasticity. As a result, the cured resin composition can alleviate the stress concentration generated by heat shrinkage and thermal shock, and can sufficiently suppress and reduce warpage and wrinkles.
- component (A) a solid rubber component at 25 ° C.
- solid rubber component a solid rubber component at 25 ° C.
- A-2) a liquid rubber at 25 ° C. Contains a component (hereinafter referred to as "liquid rubber component”).
- Solid rubber component examples include butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), isoprene rubber (IR), chloroprene rubber (CR), and butyl rubber.
- BR butadiene rubber
- SBR styrene butadiene rubber
- NBR acrylonitrile butadiene rubber
- IR isoprene rubber
- CR chloroprene rubber
- butyl rubber examples thereof include (IIR), natural rubber (NR) and the like, or modified rubbers such as modified BR, modified SBR, modified IR, modified NBR, modified CR, modified IIR and modified NR in which a functional group is introduced therein.
- BR, SBR, modified BR, and modified SBR are preferable from the viewpoint of solvent solubility, adhesiveness, and the like.
- Examples of the functional group of the modified rubber include an amino group, an alkoxysilyl group, a hydroxyl group, an epoxy group, a carboxy group, an acid anhydride group and the like.
- the position where the functional group is introduced is not particularly limited, and the monomer having a functional group is directly copolymerized and introduced into the polymer chain, modified with a modifier and introduced into the end of the polymer, or heavy. It may be any of the cases where it is introduced into the side chain of coalescence.
- SBR and the modified SBR either a block copolymer or a random copolymer can be used.
- the lower limit of the styrene content of SBR and modified SBR is preferably 15% by mass, more preferably 18% by mass.
- the upper limit of the styrene content of SBR and modified SBR is preferably 60% by mass, more preferably 50% by mass.
- the lower limit of the vinyl content of SBR and modified SBR is preferably 10% by mass.
- the upper limit of the vinyl content of SBR and modified SBR is preferably 50% by mass.
- the vinyl content refers to the content ratio of 1 and 2 conjugates in the butadiene monomer unit of the polymer chain.
- One type of solid rubber component may be used, or two or more types may be used in combination.
- the solid rubber component is not particularly limited as long as it is solid at 25 ° C.
- the Mooney viscosity is preferably in the range of 10 to 90, more preferably in the range of 20 to 60. By setting the Mooney viscosity to 10 or more, the mechanical strength is improved, and the effect of suppressing squeezing and dripping when the sheet is formed can be expected. On the other hand, by setting the Mooney viscosity to 90 or less, the solubility in a solvent can be satisfied.
- Mooney viscosity means Mooney viscosity (Moony viscosity ML1 + 4 (100 ° C.)) measured at 100 degreeC, and is measured according to JISK-6300-1: 2013.
- Mooney viscosity is an index of industrial viscosity measured by Mooney viscometer, which is a kind of rotational plasticity meter.
- ML1 + 4 (100 ° C.) means that M is Mooney viscosity, L is a large rotor (L type), 1 + 4 is a preheating time of 1 minute, and a rotor rotation time is 4 minutes. Means that it is a value.
- the Mooney viscosity can be controlled within the above range by adjusting the molecular weight and molecular weight distribution of the solid rubber component, the styrene content, the microstructure, and the like.
- the method for producing the modified rubber is not particularly limited, but it can be produced by, for example, the following method.
- a method of introducing the above functional group by modifying each of BR, SBR, IR, NBR, CR, IIR or NR which is a natural product synthesized by anionic polymerization with a modifying agent, or a monomer having the above functional group.
- the above-mentioned functional group is introduced into the polymer chain by copolymerizing with the monomer constituting the base polymer.
- the UV curable composition of the present invention is characterized by containing a liquid rubber component in addition to the solid rubber component.
- a liquid rubber component By adding the liquid rubber component, the adhesiveness of the cured product can be improved without going through a heating step. Further, even when the film is thinned, a sheet having higher uniform strength and high mechanical strength can be obtained.
- the term "liquid” means having fluidity at normal temperature and pressure (1 atm, 25 ° C.). Specifically, when the rubber component put in the container is tilted by 45 °, the shape cannot be held for 5 minutes or more, which means that the shape changes.
- liquid rubber component examples include BR, SBR, IR, NBR, CR, IIR, NR, etc., or modified BR, modified SBR, modified IR, modified NBR, modified CR, modified IIR, modified NR, etc. in which a functional group is introduced therein.
- Modified rubber can be mentioned. Among these, modified rubber is preferable. By introducing a functional group, the polarity can be improved, and the adhesion to the adherend can be expected to be improved.
- the UV curable composition of the present invention contains a liquid rubber component, it has excellent fluidity and easily penetrates into recesses on the surface of the adherend. Therefore, it adheres to the uneven shape of the surface of the adherend and has excellent adhesiveness. Further, it is considered that by using the modified rubber into which the functional group is introduced, the polar functional group on the surface of the adherend and the functional group of the modified rubber interact with each other, and the adhesiveness with the adherend is further improved. The same effect can be obtained when a solid rubber component is used as the modified rubber. Of course, a solid modified rubber and a liquid modified rubber can be used in combination.
- Examples of the functional group include an amino group, an alkoxysilyl group, a hydroxyl group, an epoxy group, a carboxy group, an acid anhydride group and the like. Considering the interaction with the polar functional group of the adherend, among these, a carboxy group and an acid anhydride group are preferable.
- Examples of the modified rubber having a carboxy group include (i) a dicarboxylic acid monoester-modified rubber composition in which the acid anhydride group of the rubber composition having an acid anhydride group is opened with alcohol, or (ii) acid. Examples thereof include a dicarboxylic acid-modified rubber composition obtained by hydrolyzing an acid anhydride group of a rubber composition having an anhydride group with water.
- Examples of the rubber composition having an acid anhydride group include a rubber composition modified with maleic anhydride.
- the position where the functional group is introduced is not particularly limited, and the monomer having a functional group is directly copolymerized, modified with a denaturing agent and introduced into the terminal of the polymer, or the side chain of the polymer. It may be any of the cases where it is introduced into.
- the SBR and the modified SBR either a block copolymer or a random copolymer can be used.
- One type of liquid rubber component may be used, or two or more types may be used in combination.
- the method for producing modified BR, modified SBR, modified IR, modified NBR, modified CR, modified IIR, and modified NR is not particularly limited, but is the same as the production method described for (A-1) solid rubber component. It can be prepared by the method.
- the molecular weight of the liquid rubber component is not particularly limited as long as it has fluidity at 25 ° C., but the number average molecular weight is preferably 80,000 or less, and the number average molecular weight is 1,000 to 50,000. More preferably, it is particularly preferably 2,000 to 40,000.
- the lower limit of the content of the liquid rubber component is preferably 3% by mass, more preferably 8% by mass, based on the entire rubber component, that is, the total amount of the solid rubber component and the liquid rubber component.
- the upper limit of the content of the liquid rubber component is preferably 50% by mass, more preferably 40% by mass, based on the entire rubber component, that is, the total amount of the solid rubber component and the liquid rubber component.
- the fact that the UV curable composition contains a liquid rubber component can be confirmed by appropriately combining known methods.
- the extract is confirmed by means such as gel permeation chromatography (GPC) measurement, infrared spectroscopy (IR) measurement, and nuclear magnetic resonance (NMR) measurement. be able to.
- GPC gel permeation chromatography
- IR infrared spectroscopy
- NMR nuclear magnetic resonance
- UV curable composition of the present invention contains a photopolymerization initiator, it can be cured in a short time by UV irradiation. Therefore, unlike an adhesive composition containing an organic peroxide as a thermal radical initiator, it is not necessary to heat it at a high temperature of about 180 ° C., and it can be applied to more adherend materials. ..
- Examples of the photopolymerization initiator used in the UV curable composition of the present invention include an alkylphenone-based polymerization initiator, an acylphosphine oxide-based photopolymerization initiator, a titanosen-based compound, an oxime ester-based compound, a benzoin-based compound, and an acetophenone-based compound. , Benzophenone compounds, thioxanthone compounds, ⁇ -acyloxime ester compounds, phenylglioxylate compounds, benzyl compounds, azo compounds, diphenyl sulfide compounds, organic dye compounds, iron-phthalocyanine compounds, benzoin ethers Examples thereof include system compounds and anthraquinone compounds.
- One type of photopolymerization initiator may be used, or two or more types may be used in combination. Of these, alkylphenone-based compounds and acylphosphine oxide-based compounds are preferable from the viewpoint of reactivity and the like.
- alkylphenone-based polymerization initiator examples include ⁇ -aminoalkylphenone-based and benzylmethyl-ketal-based, and specifically, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropane-1-.
- 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone-1 2-methyl-1- [4- (methoxythio) -phenyl] -2-morpholinopropane-2-one
- Examples thereof examples thereof include 2-dimethoxy-1,2-diphenylethane-1-one and 1-hydroxycyclohexylphenylketone. These may be used alone or in combination of two or more.
- acylphosphine oxide-based photopolymerization initiator examples include 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide and the like. These may be used alone or in combination of two or more.
- the content of the photopolymerization initiator is preferably 0.01% by mass to 10% by mass, preferably 0.1% by mass to 5% by mass, based on the entire rubber component, that is, the total amount of the solid rubber component and the liquid rubber component. It is more preferably mass%, and particularly preferably 0.5 mass% to 3 mass%. By setting the content of the photopolymerization initiator to 0.01% by mass or more with respect to the entire rubber component, that is, the total amount of the solid rubber component and the liquid rubber component, cross-linking can be performed with a low integrated light amount.
- the content of the photopolymerization initiator is 10% by mass or less with respect to the entire rubber component, that is, the total amount of the solid rubber component and the liquid rubber component, cross-linking can be performed uniformly in the film thickness direction.
- the curing of the UV curable composition proceeds more effectively, and the adhesiveness and mechanical strength of the obtained cured product can be further improved.
- (C) Cross-linking agent Since the UV curable composition of the present invention contains (C) a cross-linking agent, the cohesive force of the cured product is improved, and the mechanical strength and adhesiveness of the cured sheet are improved.
- a cross-linking agent for example, a polyfunctional (meth) acrylate having 2 or more ethylenically unsaturated groups, more preferably 3 or more, and further preferably 6 or more can be used.
- known polyester (meth) acrylates, polyether (meth) acrylates, epoxy (meth) acrylates, urethane (meth) acrylates, silicone (meth) acrylates, etc. which have two or more ethylenically unsaturated groups. Can be mentioned.
- (meth) acrylate having two or more ethylenically unsaturated groups one type may be used, or two or more types may be used in combination.
- (meth) acrylate means acrylate or methacrylate.
- a heating step of about 180 ° C. is required. Therefore, when a cross-linking agent having 5 or less ethylenically unsaturated groups is used, the cross-linking agent volatilizes during heating, so that a UV-curable sheet satisfying mechanical strength and adhesiveness may not be obtained. ..
- the cross-linking agent having 5 or less ethylenically unsaturated groups does not volatilize and has excellent mechanical strength and adhesiveness. It is presumed that a UV curable sheet can be obtained.
- the ethylenically unsaturated group of the cross-linking agent is preferably 15 or less, and more preferably 10 or less. When the number of ethylenically unsaturated groups is 15 or less, it is possible to obtain a UV curable sheet having better weather resistance because the functional groups can be sufficiently reacted when irradiated with ultraviolet rays and the reaction with time can be suppressed during use. it can.
- the content of the cross-linking agent is preferably 0.1% by mass to 100% by mass, and 1% by mass to 40% by mass, based on the entire rubber component, that is, the total amount of the solid rubber component and the liquid rubber component. Is more preferable.
- the UV curable composition of the present invention can contain various components in addition to the above components, if necessary. These components will be described below.
- Adhesive-imparting agent D
- the tackifier can be contained in the UV curable composition of the present invention. By adding the tackifier, the adhesive strength after curing can be further improved. Further, by incorporating a tackifier, it is possible to impart tackiness to the UV curable composition.
- tackifier examples include styrene resin, xylene resin, terpene resin, phenol resin, rosin, polymerized rosin, disproportionated rosin and its derivatives, phenol-modified resins such as polyterpene resin, terpenephenol, and rosinphenol, alkylphenol resin, and kumaron.
- Inden resin, xylene resin, aliphatic hydrocarbon resin, alicyclic hydrocarbon resin, aromatic hydrocarbon resin and hydrogenated products thereof can be used.
- One type of tackifier may be used, or two or more types may be used in combination.
- the content of the tackifier is preferably 0.1% by mass to 100% by mass, preferably 1% by mass to 50% by mass, based on the total amount of the rubber component, that is, the total amount of the solid rubber component and the liquid rubber component. More preferably.
- the UV curable composition of the present invention further includes a film forming aid, various fillers, a functional filler, an antioxidant, a light stabilizer, a colorant, a flame retardant, a defoamer, a leveling agent, a lubricant, and the like.
- a film forming aid such as a dispersant, a processing aid, a plasticizer, and a coupling agent can be appropriately blended.
- the UV curable sheet of the present invention has an adhesive layer formed from the above UV curable composition.
- the above UV curable composition is applied to the surface of the release film to form an adhesive layer, and then the adhesive layer is peeled off from the release film to obtain only the adhesive layer. You can also do it.
- a plurality of adhesive layers can be laminated by applying the UV curable composition to at least one surface of the base material.
- the release film, the base material, and the adhesive layer will be described.
- Release films include polyethylene film, polypropylene film, polymethylpentene (TPX) film, polyethylene film with silicone release agent, polypropylene film with silicone release agent, polyethylene terephthalate (PET) film with silicone release agent, and polyethylene resin.
- Coated paper, polypropylene resin coated paper, TPX resin coated paper and the like can be used.
- the thickness of the release film can be appropriately selected as needed. For film bases, it is preferably 12 to 250 ⁇ m, and for paper bases, it is preferably 50 to 300 ⁇ m.
- the base material is not particularly limited and can be appropriately selected according to the application of the UV curable sheet. Specifically, polyethylene terephthalate, polyethylene naphthalate, polyethylene, polypropylene, polycarbonate, acrylic resin, triacetyl cellulose, cycloolefin polymer, cycloolefin copolymer, aramid, polyimide, polyamide, polyphenylene sulfide, polyetherimide, polyethersulfone, A film, non-woven fabric, paper or the like made of a synthetic resin such as aromatic polyamide or polysulfone can be used.
- the thickness of the base material is not particularly limited and can be appropriately selected depending on the intended use.
- the thickness of the adhesive layer can be appropriately set according to the use of the UV curable sheet.
- the lower limit is preferably 5 ⁇ m, more preferably 10 ⁇ m.
- the upper limit is preferably 200 ⁇ m, more preferably 150 ⁇ m.
- the UV curable composition of the present invention is dissolved or dispersed in a solvent to prepare a coating liquid for forming an adhesive layer (hereinafter referred to as "coating liquid").
- the solid content concentration of the coating liquid is preferably 10% by mass to 90% by mass, more preferably 20% by mass to 60% by mass.
- a coating liquid is applied to the surface of the release film, dried, formed into a film or sheet, peeled from the release film, and UV-cured consisting of only an adhesive layer. Get a mold sheet.
- a coating liquid is applied to the surface of one side or both sides of the base material and then dried to obtain a UV curable sheet.
- the method of applying the coating liquid is not particularly limited, and is known using a wire bar, an applicator, a brush, a spray, a roller, a gravure coater, a die coater, a lip coater, a comma coater, a knife coater, a reverse coater, a spin coater, or the like.
- the method can be used. If necessary, the surface of the release film or the base material to which the coating liquid is applied can be surface-treated in advance.
- the method for drying the coating liquid is not particularly limited, and known methods such as hot air drying and vacuum drying can be used.
- the drying conditions can be appropriately set according to the type of UV curable composition, the type of solvent used for adjusting the coating liquid, the film thickness of the adhesive layer, and the like. Usually, it is dried at 60 ° C. to 130 ° C. for 1 minute to 10 minutes.
- the UV curable sheet of the present invention can be used as a normal adhesive sheet if UV irradiation is possible. Specifically, adhesion between materials with different linear expansion coefficient (CTE), adhesive sheet with reworkability, heteroconductive adhesive sheet, heat-dissipating adhesive sheet, adhesive sheet that can follow the expansion and contraction of the material, silicone type It can be suitably used as an alternative to urethane-based adhesive sheets, adhesive sheets with vibration durability, and the like.
- CTE linear expansion coefficient
- adhesive sheet with reworkability esion between materials with different linear expansion coefficient (CTE), adhesive sheet with reworkability, heteroconductive adhesive sheet, heat-dissipating adhesive sheet, adhesive sheet that can follow the expansion and contraction of the material, silicone type It can be suitably used as an alternative to urethane-based adhesive sheets, adhesive sheets with vibration durability, and the like.
- the UV curable sheet obtained as described above can be irradiated with UV to crosslink the rubber component having a diene skeleton to obtain a cured product.
- UV can be irradiated by a high-pressure mercury lamp, a fusion H lamp, a xenon lamp, a metal halide lamp, a UV-LED lamp, or the like.
- the integrated light intensity is preferably about 300 to 3,000 mJ / cm 2.
- UV curable sheet provided with an adhesive layer on the surface of the base material UV may be irradiated from the adhesive layer side or from the base material side. However, when irradiating from the base material side, the base material must be ultraviolet transparent.
- the gel fraction of the obtained cured product is preferably 50% to 100%, more preferably 50% to 95%.
- the gel fraction is 50% or more, high mechanical strength can be obtained.
- the gel fraction is 95% or less, higher elasticity can be obtained.
- the gel fraction may exceed 95%, but in this case, it becomes too hard and may not be suitable depending on the application.
- the gel fraction was measured according to the following method. A UV-curable sheet composed of only an adhesive layer having a predetermined thickness was cured by irradiating it with UV having an integrated light intensity of 1600 mJ / cm 2 at room temperature with a high-pressure mercury lamp, and then a test piece having a size of 30 mm ⁇ 30 mm was prepared.
- the 90-degree peeling force of the UV curable sheet of the present invention is preferably 4 N / inch or more, more preferably 7 N / inch or more, and particularly preferably 10 N / inch or more.
- the 90 degree peeling force of the UV curable sheet was measured according to the following method. As the adherend, a PET substrate having a thickness of 50 ⁇ m and a brightly annealed stainless steel (SUS304, thickness 1.5 mm) were used.
- a UV-curable sheet consisting of only an adhesive layer having a predetermined thickness is sandwiched between the adherends and bonded by a hand roller, and a high-pressure mercury lamp is used to emit UV having an integrated light amount of 1600 mJ / cm 2 at room temperature on the PET substrate side. It was irradiated from the surface and cured to prepare a test piece. Using this test piece, a 90-degree peeling force with respect to stainless steel was measured at a tensile speed of 50 mm / min in accordance with JIS K-6854. A universal testing machine # 5982 manufactured by Instron was used for the measurement.
- the mechanical strength of UV curable sheet was evaluated by the following method.
- a UV curable sheet consisting of only an adhesive layer having a predetermined thickness was cured by irradiating it with UV having an integrated light amount of 1600 mJ / cm 2 at room temperature, and then the test piece was changed to 10 mm ⁇ 150 mm.
- the tensile strength at the time of cutting (MPa) and the elongation at the time of cutting (%) were measured according to the above.
- the tensile speed was set to 500 mm / min.
- the tensile strength at the time of cutting of the UV curable sheet of the present invention after curing is preferably 2 MPa or more, and more preferably 3 MPa or more.
- the elongation at the time of cutting of the UV curable sheet of the present invention after curing is preferably 200% or more, and more preferably 300% or more.
- the UV curable sheet of the present invention is characterized by high tensile strength at the time of cutting after curing even if it is thin.
- the JIS K-6251 is subjected to UV irradiation with an integrated light intensity of 1600 mJ / cm 2 at room temperature with a high-pressure mercury lamp. It has been confirmed that the tensile strength at the time of cutting is 3.5 MPa or more.
- thermosetting adhesive sheet when the sheet thickness is thick, the tensile strength at the time of cutting shows a high value, but when the sheet thickness is thin, the tensile strength at the time of cutting sharply decreases. Therefore, with the thermosetting adhesive sheet, it was not possible to realize a tensile strength at the time of cutting of 3.5 MPa or more in the range of the sheet thickness of 25 ⁇ m to 50 ⁇ m.
- the UV curable sheet of the present invention has a tensile strength at the time of cutting of 3.5 MPa or more in the entire range of the sheet thickness of 25 ⁇ m to 100 ⁇ m.
- the tensile strength at cutting measured by the above method of the cured product of the UV curable sheet prepared in the range of sheet thickness of 25 ⁇ m to 50 ⁇ m is 3.5 MPa or more, it is the UV curable sheet of the present invention. Can be confirmed.
- (Components of UV curable composition) Rubber component having a diene skeleton (A-1) Solid rubber component (A-1-1) Styrene butadiene rubber: (Styrene content: 25%, Mooney viscosity ML1 + 4 (100 ° C.): 47) (A-1-2) Styrene-butadiene rubber: (Styrene content: 46%, Mooney viscosity ML1 + 4 (100 ° C.): 45) (A-1-3) Butadiene rubber: (Moony viscosity ML1 + 4 (100 ° C.): 45) (A-2) Liquid rubber component (A-2-1) Styrene-butadiene random copolymer: (1,2 vinyl (butadiene): 70%, styrene content: 25%, Mn: 4.5 ⁇ 1000) (A-2-2) Maleic anhydride-modified styrene-butadiene rubber: (Mn: 9.1 ⁇ 1000
- the above A-2-4 component was prepared by the following production method.
- Maleic anhydride-modified styrene-butadiene rubber (A-2-2 component, 25 g) and 10.3 g of toluene, 12.5 g of monoglime and 2.7 g of pure water as a diluting solvent are put into an Erlenmeyer flask with an Allihn condenser connected to the top. Then, the mixture was stirred with a magnetic stirrer until the resin insoluble content could not be confirmed. The amount of pure water added was 10 times the amount equivalent to the acid anhydride. Then, the ring-opening reaction was carried out in an outdoor bath at 95 ° C. for 7 hours.
- the diluting solvent and water were removed using a vacuum concentrator and a vacuum dryer to obtain a carboxy group-modified styrene-butadiene rubber (A-2-4).
- the infrared absorption spectrum of the obtained carboxy group-modified styrene-butadiene rubber (A-2-4) was compared with the infrared absorption spectrum of the maleic anhydride-modified styrene-butadiene rubber (A-2-2) before the reaction.
- the above A-2-5 component was prepared by the following production method.
- Maleic anhydride-modified styrene-butadiene rubber (A-2-2 component, 25 g) and 19.4 g of toluene and 7.0 g of ethanol as a diluting solvent were put into an Erlenmeyer flask with an Allihn condenser connected to the top, and put into a magnetic stirrer. The mixture was stirred until the resin insoluble content could not be confirmed. The amount of ethanol added was 10 times the amount equivalent to the acid anhydride. Then, the ring-opening reaction was carried out in an outdoor bath at 95 ° C. for 7 hours.
- A-2-5 a carboxy group-modified styrene-butadiene rubber
- A-2-5 The infrared absorption spectrum of the carboxy group-modified styrene-butadiene rubber (A-2-5) was compared with the infrared absorption spectrum of the maleic anhydride-modified styrene-butadiene rubber (A-2-2) before the reaction.
- Examples 1 to 16 Comparative Examples 1 to 2 and Reference Examples 1 to 4
- Each component was blended in the mass ratios shown in Tables 1 to 4, put in toluene, mixed and stirred, and then defoamed under reduced pressure to obtain a coating liquid.
- the obtained coating liquid was applied onto a release film (PET film with a silicone release agent) using an applicator.
- the thickness of the adhesive layer after drying was adjusted to be the thickness shown in Tables 1 to 4. After drying at 120 ° C. for 3 minutes, the release film was peeled off to obtain a UV curable sheet.
- the UV curable sheets of Examples 1 to 16 and Comparative Examples 1 and 2 were irradiated with UV having an integrated light intensity of 1600 mJ / cm 2 at room temperature with a high-pressure mercury lamp to obtain a cured product.
- Tables 1, 2 and 4 show the results of measuring the gel fraction, 90 degree peeling force, tensile strength at cutting and elongation at cutting of the obtained cured product by the above-mentioned methods.
- Table 3 shows the measurement results of the gel fraction of the cured product and the 90-degree peeling force.
- the composition of Reference Example 1 using an organic peroxide as a thermal radical initiator was also prepared. In the reference example, a cured product was obtained by heating at 180 ° C. for 1 hour.
- the effect of the UV curable composition of the present invention containing a solid rubber component and a liquid rubber component as a rubber component having a diene skeleton was confirmed.
- the liquid rubber component as the rubber component
- the fluidity of the UV curable composition is improved as compared with Comparative Example 1 containing only the solid rubber component, and the UV curable composition is also formed in the recesses on the surface of the adherend. It is probable that an object entered and the anchor effect was obtained.
- the gel fraction of the cured product of Example 1 was about the same as that of the cured product of Reference Example 1 (conventional method) obtained by thermosetting.
- Example 1 had the mechanical strength normally required as a rubber composition, similar to the cured product of Reference Example 1 having a thickness of 100 ⁇ m obtained by thermosetting.
- Heating at 180 ° C. is required, but since PET is used as the adherend, the 90-degree peeling force could not be measured.
- the 90-degree peeling force could be measured. Then, it was confirmed that the obtained value also has the adhesive strength normally required for an adhesive sheet.
- a UV curable type that can be cured without going through a high-temperature heating step, has excellent adhesiveness (adhesive strength), and can be used even for an adherend having inferior heat resistance. It was found that the composition was obtained.
- Example 2 instead of the liquid rubber component of Example 1 (A-2-1) styrene-butadiene random copolymer, the modified rubber (A-2-2) maleic anhydride-modified styrene-butadiene rubber (Example). 2), (A-2-3) maleic anhydride-modified butadiene rubber (Example 3), (A-2-4) carboxy group-modified styrene-butadiene rubber (water-opened product of A-2-2) (Example) 4) and (A-2-5) carboxy group-modified styrene-butadiene rubber: (A-2-2 ethanol-opened product) (Example 5) are used.
- Example 2 the adhesive strength was further improved as compared with Example 1. Since the liquid rubber component is contained in Examples 2 to 5, the fluidity of the UV-curable composition is improved as compared with Comparative Example 1 containing only the solid rubber component, and the recesses of the adherend are also UV-curable. It is considered that the composition entered and the anchor effect was obtained. Then, in Examples 2 to 5 using the modified liquid rubber component into which the functional group was introduced, the adhesive force was increased due to the interaction between the functional group in the modified liquid rubber component and the polar functional group on the surface of the adherend. It is presumed that it has improved further.
- Example 2 since the 90-degree peeling force of Examples 4 and 5 using the carboxy group-modified styrene-butadiene rubber is high, it is considered that the modified rubber having a carboxy group introduced is particularly effective.
- Example 2 and Example 3 are examples in which a liquid rubber modified with maleic anhydride is used, Example 2 in which both the solid rubber component and the liquid rubber component are styrene-butadiene rubber is 90 degrees. It was also confirmed that the peeling force, the tensile strength at the time of cutting, and the elongation at the time of cutting showed good results.
- a UV curable sheet and a cured product were prepared in the same manner as in Example 1 except that the thickness of the adhesive layer of Example 2 was changed, and used as Examples 6 and 7. The evaluation results will be described later.
- the effect of the present invention can be obtained even in a configuration in which the tackifier (D-1) aromatic-modified terpene resin or (D-2) alkylphenol-modified xylene resin is added. It was confirmed that.
- thermosetting sheet and a cured product were prepared in the same manner as in Example 1 and used as Reference Example 2.
- the thickness of the adhesive layer at the time of drying was adjusted to 50 ⁇ m (Reference Example 3) and 25 ⁇ m (Reference Example 4), respectively, to obtain a cured product.
- Example 1 shows the relationship between the thickness of the above-mentioned Examples (Examples 2, 6 and 7) and Reference Examples (Reference Examples 2 to 4) and the tensile strength at the time of cutting. From FIG. 1, in the cured product of the reference example, the tensile strength at the time of cutting decreases as the thickness decreases, whereas in the cured product of the example, the tensile strength at the time of cutting is constant regardless of the thickness. was confirmed to be obtained. Specifically, when the thickness was 100 ⁇ m, the tensile strength of the cured product of Reference Example 2 at the time of cutting was 5.3 MPa.
- thermosetting resin as in Reference Examples 3 to 4
- the influence of heat convection between the solid rubber component and the liquid rubber component becomes remarkable.
- liquid rubber components are gathered and crystallized, and locally non-uniform parts are generated, and breakage is likely to occur starting from these parts.
- Examples 2, 6 and 7 of the UV curable type since the amount of heat during UV irradiation is small, heat convection between the solid rubber component and the liquid rubber component in the sheet is unlikely to occur, and local non-uniform parts are formed. Since it is unlikely to occur, it is considered that a sheet having high tensile strength at the time of cutting can be obtained even if it is thin.
- the UV curable composition and the UV curable sheet were prepared in the same manner as in Example 1 except that the ratio of the solid rubber component and the liquid rubber component in Example 2 was changed, and used as Examples 10 to 13.
- the contents of the liquid rubber component with respect to the total amount of the rubber component having a diene skeleton were 5% by mass (Example 10), 30% by mass (Example 11), 50% by mass (Example 12) and 70% by mass (Example 12), respectively. 13).
- Table 3 shows the results of evaluating the gel fraction of the obtained cured product and the 90-degree peeling force. As a comparison, the result of Comparative Example 1 is also shown.
- the 90-degree peeling force increases as the content of the liquid rubber component increases, the liquid rubber component content reaches its maximum at around 30% by mass, and then decreases as the liquid rubber component increases. I understood it.
- Example 14 The same as in Example 1 except that the photopolymerization initiator was changed from (B-1) 1-hydroxycyclohexylphenyl ketone to (B-2) 2,2-dimethoxy-1,2-diphenylethane-1-one.
- Table 4 shows the results of preparing and evaluating the UV curable composition and the UV curable sheet by the method of (Example 14). From the above results, it was confirmed that even if 2,2-dimethoxy-1,2-diphenylethane-1-one was used as the photopolymerization initiator, excellent adhesiveness and mechanical strength were exhibited, and the effect of the present invention could be obtained. Was done.
- the cross-linking agent was changed to (C-1) dipentaerythritol hexaacrylate to be (C-2) aromatic polyester acrylate (Example 15) and (C-3) urethane acrylate (Example 16).
- Table 4 also shows the results of preparing and evaluating the UV curable composition and the UV curable sheet in the same manner as in Example 14. From the above results, it was found that the adhesiveness was improved and excellent mechanical strength could be obtained by using any of the cross-linking agents of Example 14, Example 15, and Example 16. From the results in the table, it was confirmed that excellent adhesiveness can be obtained when the number of ethylenically unsaturated groups is 2 or more. Although not shown in the table, it was found that better adhesiveness can be obtained by using a cross-linking agent having up to 15 ethylenically unsaturated groups.
Abstract
Description
これらの応力を緩和させる方法としては、接着剤に可塑剤等の柔軟成分を用いる方法が挙げられる。接着材層を柔軟化させることは、塑性変形を誘発することを意味し、材料の変形に追従するように接着材層を塑性変形させることで材料と接着材層の破壊を抑制することになる。ところが、一旦変形した材料が元に戻ろうとすると、接着材層の変形によって生じた歪みは接着材層や接合界面に内部応力として蓄積され、ひいては凝集力低下による材料破壊のリスクにつながる。
特許文献1には、(A)ジエン骨格を有するゴム成分と、(B)エチレン性不飽和基の数が6以上であるモノマーおよび/またはオリゴマーと、(C)有機過酸化物からなるラジカル開始剤と、を含むことを特徴とする接着剤組成物が開示されている。特許文献1には、ゴムを含み優れた接着力を有し、かつ、反りや皺を十分に抑制低減することのできる接着剤組成物およびこれを用いた接着シートが得られることが記載されている。
しかしながら、特許文献1の接着剤組成物は、ラジカル源として熱ラジカル開始剤である有機過酸化物を用いているため、その熱硬化には180℃程度の加熱工程を要しており、耐熱性の低い被着体への適用が難しい点で改善する余地があった。
特許文献2の方法により、低温且つ短時間で硬化物を得ることが可能となる。このため、加熱工程が不要なことで、耐熱性の低い被着体にも適用可能と考えられる。しかしながら、この方法により得られる架橋ゴムでは、被着体との十分な接着性が得られないという問題点があった。
また、上記変性ゴムは、カルボキシ基、酸無水物基、アミノ基、アルコキシシリル基、水酸基およびエポキシ基から選択される少なくとも1種で変性されているゴムを含有することが好ましい。
さらに、上記変性ゴムは、25℃において液状のゴム成分であることが好ましい。
上記液状ゴムの配合量は、ゴム成分の総量に対して質量比で3~50%の範囲であることが好ましい。
また、上記固体状のゴム成分として、ブタジエンゴムおよびスチレンブタジエンゴムから選択される少なくとも1種を含有することが好ましい。
上記接着剤層の厚みは5~200μmであることが好ましい。
また、上記UV硬化型シートは、室温で高圧水銀灯により、積算光量1600mJ/cm2のUVを照射した後の、JISK-6854に基づく90度剥離力が4N/inch以上であることが好ましい。
なお、本明細書中、数値範囲を表す「~」は、その上限値および下限値としてそれぞれ記載されている数値を含む範囲を表す。また、数値範囲において上限値のみ単位が記載されている場合は、下限値も上限値と同じ単位であることを意味する。
本明細書に段階的に記載されている数値範囲において、ある数値範囲で記載された上限値または下限値は、他の段階的な記載の数値範囲の上限値または下限値に置き換えてもよい。
また、本明細書に記載されている数値範囲において、ある数値範囲で記載された上限値または下限値は、実施例に示されている値に置き換えてもよい。
本明細書において組成物中の各成分の含有率または含有量は、組成物中に各成分に該当する物質が複数種存在する場合、特に断らない限り、組成物中に存在する当該複数種の物質の合計の含有率または含有量を意味する。
一般にラジカル重合型の接着剤組成物では、ラジカル源として熱ラジカル開始剤を用いているために加熱工程が必須であり、その加熱工程によって軟化した接着剤組成物が被着体表面の凹凸部に入り込み、アンカー効果により、優れた接着性が得られていた。
これに対して、UV硬化型組成物は、ラジカル源として光ラジカル開始剤を使用し、UV照射によって硬化させるため、加熱工程を経ることなく短時間で硬化物を得ることができる。しかしながら、従来のUV硬化型組成物では、加熱工程を経ないことから、アンカー効果を得にくく、十分な接着性が得られなかった。
本発明は、ジエン骨格を有するゴム成分として、25℃において固体状のゴム成分と液状のゴム成分を併用することにより、加熱工程を経ることなく、被着体との接着性を向上させることができることを見出し、完成されたものである。さらに、本発明のUV硬化型組成物では、薄膜化しても均一で、高い機械強度を有するシートが得られる。
本発明のUV硬化型組成物はジエン骨格を有するゴム成分(以下「(A)成分」ともいう。)を含む。このため、UV照射による硬化後、この(A)成分が架橋してゴム弾性を有する。その結果、硬化後の樹脂組成物は、熱収縮や熱衝撃により発生する応力集中を緩和し、反りや皺を十分に抑制低減することができる。
なお、本発明においては、(A)成分として、(A―1)25℃において固体状のゴム成分(以下、「固体状ゴム成分」という。)および(A―2)25℃において液状のゴム成分(以下、「液状ゴム成分」という。)を含有する。以下にそれぞれの成分について説明する。
固体状ゴム成分として、例えば、ブタジエンゴム(BR)、スチレンブタジエンゴム(SBR)、アクリロニトリルブタジエンゴム(NBR)、イソプレンゴム(IR)、クロロプレンゴム(CR)、ブチルゴム(IIR)、天然ゴム(NR)等またはこれらに官能基が導入された変性BR、変性SBR、変性IR、変性NBR、変性CR、変性IIR、変性NR等の変性ゴムが挙げられる。これらの中でも、溶剤溶解性、接着性等の観点から、BR、SBR、変性BR、変性SBRが好ましい。
変性ゴムの官能基としては、例えばアミノ基、アルコキシシリル基、水酸基、エポキシ基、カルボキシ基、酸無水物基等が挙げられる。官能基が導入される位置は特に限定されず、官能基を有する単量体を直接共重合してポリマー鎖に導入する場合、変性剤により変性させて重合体の末端に導入する場合、または重合体の側鎖に導入する場合の何れであってもよい。
なお、SBR、変性SBRはブロックコポリマー、ランダムコポリマーの何れを用いることもできる。SBR、変性SBRのスチレン含量の下限は、15質量%であることが好ましく、18質量%であることがより好ましい。SBR、変性SBRのスチレン含量の上限は60質量%であることが好ましく、50質量%であることがより好ましい。SBR、変性SBRのビニル含量の下限は、10質量%であることが好ましい。SBR、変性SBRのビニル含量の上限は、50質量%であることが好ましい。なお、ビニル含量とはポリマー鎖のブタジエンモノマー単位における1,2結合体の含有比率を言う。固体状ゴム成分は、1種類を用いることもできるし、2種類以上を組み合わせて用いることもできる。
なお、本明細書において、ムーニー粘度は、100℃で測定したムーニー粘度(ムーニー粘度ML1+4(100℃))を意味し、JISK-6300-1:2013に準じて測定される。
ムーニー粘度とは、回転可塑度計の1種であるムーニー粘度計で測定される工業的な粘度の指標である。ML1+4(100℃)とは、Mはムーニー粘度、Lは大ローター(L型)、1+4は予備加熱時間が1分間、ローターの回転時間が4分間であり、100℃の条件下にて測定した値であることを意味する。固体ゴム成分の分子量や分子量分布あるいはスチレン含量、ミクロ構造等を調整することにより、ムーニー粘度を上記範囲に制御することができる。
本発明のUV硬化型組成物は、固体状ゴム成分に加えて、液状ゴム成分を含有することを特徴とする。
液状ゴム成分を加えることにより、加熱工程を経ることなく、硬化物の接着性を向上させることができる。さらに、薄膜化した場合にもより均一で、高い機械強度を有するシートを得ることができる。
ここで液状とは、常温常圧(1atm、25℃)において流動性を有することをいう。具体的には、容器に入れたゴム成分を45°傾けた場合、その形状を5分以上保持できず、形状の変化を生じることを意味する。
液状ゴム成分としては、BR、SBR、IR、NBR、CR、IIR、NR等またはこれらに官能基が導入された変性BR、変性SBR、変性IR、変性NBR、変性CR、変性IIR、変性NR等の変性ゴムが挙げられる。これらの中でも、変性ゴムが好ましい。官能基を導入することにより、極性が向上し、被着体との密着性の向上が期待できる。
官能基としては、例えばアミノ基、アルコキシシリル基、水酸基、エポキシ基、カルボキシ基、酸無水物基等が挙げられる。
被着体の極性官能基との相互作用を考慮すると、これらの中でも、カルボキシ基、酸無水物基が好ましい。カルボキシ基を有する変性ゴムとしては、例えば、(i)酸無水物基を有するゴム組成物の酸無水物基をアルコールで開環させたジカルボン酸モノエステル変性のゴム組成物、あるいは(ii)酸無水物基を有するゴム組成物の酸無水物基を水で加水分解することで得られるジカルボン酸変性のゴム組成物が挙げられる。酸無水物基を有するゴム組成物としては、無水マレイン酸変性のゴム組成物等が挙げられる。
なお、官能基が導入される位置は特に限定されず、官能基を有する単量体を直接共重合する場合、変性剤により変性させて重合体の末端に導入する場合、または重合体の側鎖に導入する場合の何れであってもよい。また、SBR、変性SBRはブロックコポリマー、ランダムコポリマーの何れを用いることもできる。液状ゴム成分は、1種類を用いることもできるし、2種類以上を組み合わせて用いることもできる。
変性BR、変性SBR、変性IR、変性NBR、変性CR、変性IIR、変性NRの製造方法は特に限定されるものではないが、(A―1)固体状ゴム成分で記載した製造方法と同様の方法で調製することができる。
液状ゴム成分の含有量をゴム成分全体、すなわち固体状ゴム成分と液状ゴム成分の総量に対して、3質量%以上とすることにより、樹脂のフロー性が向上し、基材との密着性向上の効果が期待できる。
一方、液状ゴム成分の含有量をゴム成分全体、すなわち固体状ゴム成分と液状ゴム成分の総量に対して、50質量%以下とすることにより、高い機械強度を保持する効果が期待できる。
本発明のUV硬化型組成物は、光重合開始剤を含有するため、UV照射により短時間で硬化させることができる。このため、熱ラジカル開始剤として有機過酸化物を含有する接着剤組成物のように、180℃程度の高温で加熱する必要がなくなり、より多くの被着体材料に適用することが可能となる。
本発明のUV硬化型組成物に用いる光重合開始剤としては、アルキルフェノン系重合開始剤、アシルフォスフィンオキサイド系光重合開始剤、チタノセン系化合物、オキシムエステル系化合物、ベンゾイン系化合物、アセトフェノン系化合物、ベンゾフェノン系化合物、チオキサントン系化合物、α-アシロキシムエステル系化合物、フェニルグリオキシレート系化合物、ベンジル系化合物、アゾ系化合物、ジフェニルスルフィド系化合物、有機色素系化合物、鉄-フタロシアニン系化合物、ベンゾインエーテル系化合物、アントラキノン系化合物等が挙げられる。
光重合開始剤は、1種類を用いることもできるし、2種類以上を組み合わせて用いることもできる。
これらのうち、反応性等の観点から、アルキルフェノン系化合物、アシルフォスフィンオキサイド系化合物が好ましい。
光重合開始剤の含有量をゴム成分全体、すなわち固体状ゴム成分と液状ゴム成分の総量に対して、0.01質量%以上とすることにより、低い積算光量で架橋させることができる。
一方、光重合開始剤の含有量をゴム成分全体、すなわち固体状ゴム成分と液状ゴム成分の総量に対して、10質量%以下とすることにより、膜厚方向で均一に架橋させることができる。
光重合開始剤の含有量を上記範囲とすることにより、UV硬化型組成物の硬化がより効果的に進行し、得られる硬化物の接着性および機械強度をさらに向上させることができる。
本発明のUV硬化型組成物は、(C)架橋剤を含有するため、硬化物の凝集力が向上し、硬化後のシートの機械強度と接着性が向上する。
架橋剤としては、例えば、エチレン性不飽和基の数が2以上、より好ましくは3以上、さらに好ましくは6以上の多官能(メタ)アクリレートを用いることができる。具体的には、エチレン性不飽和基の数が2以上である公知のポリエステル(メタ)アクリレート、ポリエーテル(メタ)アクリレート、エポキシ(メタ)アクリレート、ウレタン(メタ)アクリレート、シリコーン(メタ)アクリレート等が挙げられる。これらエチレン性不飽和基の数が2以上の多官能(メタ)アクリレートは、1種類を用いることもできるし、2種類以上を組み合わせて用いることもできる。なお、(メタ)アクリレートとはアクリレートまたはメタクリレートのことを示す。
熱ラジカル開始剤を用いた従来技術では、180℃程度の加熱工程が必要となる。このため、エチレン性不飽和基の数が5以下の架橋剤を用いた場合、加熱時に当該架橋剤が揮発するため、機械強度と接着性を満足するUV硬化型シートが得られない場合がある。これに対し、UV硬化を用いた本発明では、加熱硬化工程が必要ないため、エチレン性不飽和基の数が5以下の架橋剤は揮発することがなく、優れた機械強度と接着性を有するUV硬化型シートを得ることができるものと推測される。
なお、架橋剤のエチレン性不飽和基は、15以下であることが好ましく、10以下であることがより好ましい。エチレン性不飽和基の数が15以下であれば、紫外線照射時に官能基が十分反応し、使用時に経時反応が生じることを抑制できるため、耐候性のより優れたUV硬化型シートを得ることができる。
架橋剤の含有量は、ゴム成分全体、すなわち固体状ゴム成分と液状ゴム成分の総量に対して、0.1質量%~100質量%であることが好ましく、1質量%~40質量%であることがより好ましい。架橋剤の含有量を上記範囲にすることにより、より優れた接着性を有するUV硬化型組成物およびUV硬化型シートを得ることができる。
本発明のUV硬化型組成物には、(D)粘着付与剤を含有させることができる。粘着付与剤を加えることにより、硬化後の接着力をさらに向上させることができる。また、粘着付与剤を含有させることにより、UV硬化型組成物にタック性を付与することもできる。
粘着付与剤は、1種類を用いることもできるし、2種類以上を組み合わせて用いることもできる。
粘着付与剤の含有量は、ゴム成分全体、すなわち固体状ゴム成分と液状ゴム成分の総量に対して、0.1質量%~100質量%であることが好ましく、1質量%~50質量%であることがより好ましい。粘着付与剤を上記範囲とすることにより、UV硬化型組成物の未硬化時の作業性と硬化後の接着性をさらに向上させることができる。
本発明のUV硬化型シートは、上記UV硬化型組成物から形成された接着剤層を有する。本発明のUV硬化型シートは、離型フィルムの表面に上記UV硬化型組成物を塗布して接着剤層を形成した後、離型フィルムから接着剤層を剥離して接着剤層のみを得ることもできる。また、基材の少なくとも一面に上記UV硬化型組成物を塗布することにより複数の接着剤層を積層させることもできる。以下、離型フィルム、基材および接着剤層について説明する。
本発明のUV硬化型組成物を用いることにより、熱硬化の場合と比較して薄くて均一な構造を有するシートを生産性よく製造することができる。得られるUV硬化型シートは、薄くしても機械強度が高く、伸縮性が高いため、接着シート、ストレッチャブルシート等として好適に用いることができる。
本発明のUV硬化型組成物を溶剤に溶解または分散して、接着剤層形成用塗工液(以下、「塗工液」という。)を調製する。塗工液の固形分濃度は、10質量%~90質量%とすることが好ましく、20質量%~60質量%とすることがより好ましい。離型フィルムを用いる場合には、離型フィルム表面に塗工液を塗布した後、乾燥し、フィルム状またはシート状に形成して、離型フィルムから剥離して接着剤層のみからなるUV硬化型シートを得る。また、基材を用いる場合には、基材の片側または両側の表面に塗工液を塗布した後、乾燥してUV硬化型シートとする。
基材の表面に接着剤層が設けられているUV硬化型シートの場合、接着剤層側からUVを照射してもよいし、基材側から照射してもよい。ただし、基材側から照射する場合には、基材が紫外線透過性でなければならない。
得られた硬化物のゲル分率は、50%~100%であることが好ましく、50%~95%であることがより好ましい。ゲル分率が50%以上であることにより、高い機械強度を得ることができる。ゲル分率が95%以下であることにより、より高い伸縮性を得ることができる。なお、ゲル分率は、95%を超えてもよいが、この場合、硬くなりすぎ、用途によっては、適さない可能性もある。ゲル分率は、以下の方法に従って測定した。
所定の厚みの接着剤層のみからなるUV硬化型シートに、高圧水銀灯により、室温で積算光量1600mJ/cm2のUVを照射して硬化させた後、サイズ30mm×30mmのテストピースを作製した。このテストピースを、ポリエステル製メッシュ[質量(Ag)]で包み込んだ状態で、質量(Bg)を測定した。次いで、100mlのトルエン中に浸漬し、室温にて96時間以上放置した。その後、メッシュ付きテストピースを取り出し、トルエンで洗浄し、120℃で、3時間乾燥した。乾燥後の質量(Cg)を測定し、以下の式によりゲル分率を算出した。
ゲル分率(質量%)=[(C-A)/(B-A)]×100
本発明のUV硬化型シートの90度剥離力は、4N/inch以上であることが好ましく、7N/inch以上であることがさらに好ましく、10N/inch以上であることが特に好ましい。UV硬化型シートの90度剥離力は、以下の方法に従って測定した。
被着体として、厚み50μmのPET基材と光輝焼鈍されたステンレス鋼(SUS304、厚み1.5mm)とを用いた。所定の厚みの接着剤層のみからなるUV硬化型シートを上記被着体の間に挟んでハンドローラにより貼合し、高圧水銀灯により、室温で積算光量1600mJ/cm2のUVをPET基材側から照射して硬化させ、試験片とした。この試験片を用いてJISK-6854に準拠し、引張速度50mm/minでステンレス鋼に対する90度剥離力の測定を行った。測定には、インストロン社製万能試験機#5982を用いた。
本発明においては、以下の方法によって機械強度の評価を行った。
所定の厚みの接着剤層のみからなるUV硬化型シートに、室温で積算光量1600mJ/cm2のUVを照射して硬化させた後、試験片を10mm×150mmに変更した以外は、JISK-6251に準拠して、切断時引張強さ(MPa)および切断時伸び(%)を測定した。なお、引張速度は500mm/minとした。
本発明のUV硬化型シートの硬化後の切断時引張強さは、2MPa以上であることが好ましく、3MPa以上であることがさらに好ましい。
本発明のUV硬化型シートの硬化後の切断時伸びは、200%以上であることが好ましく、300%以上であることがさらに好ましい。
なお、本発明のUV硬化型シートは、薄くても硬化後の切断時引張強さが高いことが特徴である。具体的には、本発明のUV硬化型シートでは、シート厚みが25μm、50μmおよび100μmの何れでも、室温で高圧水銀灯により、積算光量1600mJ/cm2のUVを照射した後の、JISK-6251に基づく切断時引張強さが、3.5MPa以上の値を示すことが確認されている。
一方、熱硬化型接着シートでは、シート厚みが厚いときには、切断時引張強さは高い値を示すが、シート厚みを薄くすると切断時引張強さは急激に低下する。そのため、熱硬化型接着シートでは、シート厚み25μm~50μmの範囲において、3.5MPa以上の切断時引張強さを実現することはできなかった。これに対して、本発明のUV硬化型シートでは、シート厚み25μm~100μmの全範囲で、3.5MPa以上の切断時引張強さを有する。したがって、25μm~50μmのシート厚みの範囲に調製されたUV硬化型シートの硬化物の上記方法で測定した切断時引張強さが3.5MPa以上であれば、本発明のUV硬化型シートであることが確認できる。
(A)ジエン骨格を有するゴム成分
(A-1)固体状ゴム成分
(A-1-1)スチレンブタジエンゴム:(スチレン含量:25%、ムーニー粘度ML1+4(100℃):47)
(A-1-2)スチレンブタジエンゴム:(スチレン含量:46%、ムーニー粘度ML1+4(100℃):45)
(A-1-3)ブタジエンゴム:(ムーニー粘度ML1+4(100℃):45)
(A-2)液状ゴム成分
(A-2-1)スチレン・ブタジエンランダムコポリマー:(1,2ビニル(ブタジエン):70%、スチレン含量:25%、Mn:4.5×1000)
(A-2-2)無水マレイン酸変性スチレンブタジエンゴム:(Mn:9.1×1000、酸価:34mgKOH/g)
(A-2-3)無水マレイン酸変性ブタジエンゴム:(Mn:5.0×1000、酸価:57mgKOH/g)
(A-2-4)カルボキシ基変性スチレンブタジエンゴム:(ジカルボン酸変性スチレンブタジエンゴム)
(A-2-5)カルボキシ基変性スチレンブタジエンゴム:(ジカルボン酸モノエステル変性スチレンブタジエンゴム)
(A-2-6)無水マレイン酸変性イソプレンゴム:(Mn:34.0×1000、酸価:9~11mgKOH/g)
(A-2-7)カルボキシ基変性イソプレンゴム:(Mn:30×1000、38℃における粘度430Pa・s)
(A-2-8)エポキシ基変性ブタジエンゴム:(Mn:1000~2000、エポキシ当量:190~210(g/eq))
(A-2-9)水酸基変性ブタジエンゴム:(Mn:3.2×1000、水酸基価:0.64meq/g)
(B)光重合開始剤
(B-1)1-ヒドロキシシクロヘキシルフェニルケトン
(B-2)2,2-ジメトキシ-1,2-ジフェニルエタン-1-オン
(B’)有機過酸化物からなるラジカル開始剤
(B’-1)ジクミルパーオキサイド
(C)架橋剤
(C-1)ポリエステルアクリレートの一種であるジペンタエリスリトールヘキサアクリレート、エチレン性不飽和基の数:6
(C-2)芳香族ポリエステルアクリレート、エチレン性不飽和基の数:2)
(C-3)ウレタンアクリレート:エチレン性不飽和基の数:10)
(D)粘着付与剤
(D-1)芳香族変性テルペン樹脂:YSレジンTO115(ヤスハラケミカル社製)
(D-2)アルキルフェノール変性キシレン樹脂:ニカノールGHP-150(フドー社製)
その後、外浴95℃のウォーターバスにて7時間かけて開環反応を行った。
反応後、減圧濃縮器および真空乾燥機を用いて、希釈溶剤と水を除去し、カルボキシ基変性スチレンブタジエンゴム(A-2-4)を得た。
得られたカルボキシ基変性スチレンブタジエンゴム(A-2-4)の赤外線吸収スペクトルを、反応前の無水マレイン酸変性スチレンブタジエンゴム(A-2-2)の赤外線吸収スペクトルと比較した。A-2-4では、酸無水物基のC=O伸縮振動に起因する吸収ピーク(1785cm-1)のピーク強度がA-2-2に比べて減少した。さらに、A-2-2では認められないカルボキシ基のC=O伸縮振動に起因する吸収ピーク(1710cm-1)が発現することが確認された。この結果から、ジカルボン酸変性のゴム組成物が得られたことを確認した。
上部にアリーン冷却器を接続した三角フラスコに無水マレイン酸変性スチレンブタジエンゴム(A-2-2成分、25g)、ならびに希釈溶剤としてトルエン19.4gおよびエタノール7.0gを投入し、マグネチックスターラーにて樹脂不溶分が確認できなくなるまで撹拌した。なお、エタノール添加量は、酸無水物当量の10倍量とした。
その後、外浴95℃のウォーターバスにて7時間かけて開環反応を行った。
反応後、減圧濃縮器および、真空乾燥機を用いて、希釈溶剤とエタノールを除去し、カルボキシ基変性スチレンブタジエンゴム(A-2-5)を得た。
カルボキシ基変性スチレンブタジエンゴム(A-2-5)の赤外線吸収スペクトルを、反応前の無水マレイン酸変性スチレンブタジエンゴム(A-2-2)の赤外線吸収スペクトルと比較した。A-2-5では、酸無水物基のC=O伸縮振動に起因する吸収ピーク(1785cm-1)のピーク強度がA-2-2に比べて減少した。さらに、A-2-2では認められないカルボキシ基およびエステル基のC=O伸縮振動に起因する吸収ピーク(1710cm-1および1740cm-1)が発現することが確認された。この結果から、ジカルボン酸モノエステル変性のゴム組成物が得られたことを確認した。
表1~表4に示す質量比で各構成成分を配合し、トルエン中に入れて混合撹拌した後、減圧下で脱泡して塗工液を得た。得られた塗工液を、アプリケータを用いて離型フィルム(シリコーン離型剤付きPETフィルム)上に塗布した。ここで、乾燥後の接着剤層の厚みが表1~表4に記載の厚みになるように調製した。120℃で3分乾燥した後、離型フィルムを剥離して、UV硬化型シートを得た。
その後、実施例1~16および比較例1~2のUV硬化型シートに、室温で高圧水銀灯により、積算光量1600mJ/cm2のUVを照射して、硬化物を得た。得られた硬化物のゲル分率、90度剥離力、切断時引張強さおよび切断時伸びを上述した方法で測定した結果を表1、表2および表4に示す。表3には、硬化物のゲル分率および90度剥離力の測定結果を示す。
なお、参考として、ラジカル源として熱ラジカル開始剤である有機過酸化物を用いた参考例1の組成物も調整した。参考例では、180℃で1時間加熱することにより、硬化物を得た。
これに対して、実施例1では、得られた硬化物のゲル分率は、69.2%と比較例1と同程度であったが、90度剥離力は、5.1N/inchと大幅に向上した。このことから、ジエン骨格を有するゴム成分として固体状ゴム成分および液状ゴム成分を含有する本発明のUV硬化型組成物の効果が確認された。ゴム成分として液状ゴム成分を含有することにより、固体状ゴム成分のみを含有する比較例1に比べUV硬化型組成物の流動性が向上して、被着体表面の凹部にもUV硬化型組成物が入り込みアンカー効果が得られたためと考えられる。
なお、実施例1の硬化物のゲル分率は、熱硬化により得られた参考例1(従来法)の硬化物と同程度であった。また、実施例1の硬化物においては、熱硬化により得られた厚み100μmの参考例1の硬化物と同様にゴム組成物として通常求められる機械強度を有することも確認された。なお、参考例1では180℃での加熱を要するが、被着体としてPETを使用しているため、90度剥離力を測定することができなかった。
一方、実施例1では、加熱を要しないため被着体としてPETを使用しているにも関わらず、90度剥離力を測定することができた。そして、得られた値も接着シートとして通常求められる接着力を有することが確認された。このことから、本発明により、高温の加熱工程を経ることなく硬化可能で、且つ優れた接着性(粘着力)を有し、耐熱性に劣る被着体に対しても使用可能なUV硬化型組成物が得られることがわかった。
そして、官能基が導入された変性液状ゴム成分を用いた実施例2~5では、変性液状ゴム成分中の官能基と被着体表面の極性官能基との相互作用に起因して接着力がさらに向上したと推測される。特に、カルボキシ基変性スチレンブタジエンゴムを用いた実施例4および5の90度剥離力が高いことから、カルボキシ基を導入した変性ゴムが特に有効であると考えられる。なお、実施例2と実施例3は何れも無水マレイン酸変性の液状ゴムを使用した例であるが、固体状ゴム成分と液状ゴム成分ともスチレンブタジエンゴムである実施例2の方が、90度剥離力、切断時引張強さおよび切断時伸びが良好な結果を示すことも確認できた。
実施例6の固体状ゴム成分である(A-1-1)スチレンブタジエンゴムに変えて、(A-1-2)スチレンブタジエンゴムまたは(A-1-3)ブタジエンゴムを用いた他は、実施例1と同様に、UV硬化型シートおよび硬化物を調製し、それぞれ実施例8および実施例9とした。上記UV硬化型シートおよび硬化物の評価結果より、上記固体状ゴム成分を用いても本発明の効果が得られることが確認された。
また、実施例2の変性液状ゴム成分である(A-2-2)無水マレイン酸変性スチレンブタジエンゴムに変えて、(A-2-6)無水マレイン酸変性イソプレンゴム、(A-2-7)カルボキシ基変性イソプレンゴム、(A-2-8)エポキシ基変性ブタジエンゴムおよび(A-2-9)水酸基変性ブタジエンゴムをそれぞれ用いた他は、実施例1と同様に、UV硬化型シートおよび硬化物を調製した。表中には記載していないが、上記硬化型シートおよび硬化物の評価結果より、上記液状ゴム成分を用いても本発明の効果が得られることが確認された。
さらに、表中には記載していないが、粘着付与剤である(D-1)芳香族変性テルペン樹脂または(D-2)アルキルフェノール変性キシレン樹脂を添加した構成でも、本発明の効果が得られることが確認された。
本発明において薄くても優れた機械強度を有する硬化物が得られる理由は、以下のように考えられる。熱硬化型樹脂では、参考例3~4のように、シートの厚みが薄くなると固体状ゴム成分と液状ゴム成分の熱対流の影響が顕著になる。その結果、例えば、液状ゴム成分が集まって結晶化する等、局所的に不均一な箇所が発生し、そこを起点として破断が生じやすくなる。一方、UV硬化型の実施例2、6および7では、UV照射時の熱量が少ないため、シート内での固体状ゴム成分と液状ゴム成分の熱対流が生じにくく、局所的な不均一箇所が生じにくいため、薄くても切断時引張強さの高いシートが得られるものと考えられる。
架橋剤を(C-1)ジペンタエリスリトールヘキサアクリレートに変えて、(C-2)芳香族ポリエステルアクリレート(実施例15)および(C-3)ウレタンアクリレート(実施例16)とした他は、実施例14と同様の方法でUV硬化型組成物およびUV硬化型シートを調製して評価した結果についても表4に示す。上記結果より、実施例14、実施例15、および実施例16のいずれの架橋剤を用いても、接着性が向上し、かつ優れた機械強度が得られることがわかった。
表中の結果より、エチレン性不飽和基の数が2以上であれば、優れた接着性が得られることが確認された。そして、表中には記載していないが、エチレン性不飽和基の数が15までの架橋剤を用いることにより、より優れた接着性が得られることがわかった。
Claims (13)
- ジエン骨格を有するゴム成分と、光重合開始剤と、架橋剤と、を含むUV硬化型組成物であって、前記ジエン骨格を有するゴム成分が25℃において固体状のゴム成分と液状のゴム成分とを含有するUV硬化型組成物。
- 前記固体状ゴム成分または液状ゴム成分の少なくとも一方は、変性ブタジエンゴム、変性スチレンブタジエンゴムおよび変性イソプレンゴムから選択される少なくとも1種を含む変性ゴムを含有する請求項1に記載のUV硬化型組成物。
- 前記変性ゴムは、カルボキシ基、酸無水物基、アミノ基、アルコキシシリル基、水酸基およびエポキシ基から選択される少なくとも1種で変性されているゴムを含有する請求項2に記載のUV硬化型組成物。
- 前記変性ゴムは、25℃において液状のゴム成分である請求項2または3に記載のUV硬化型組成物。
- 前記液状ゴムの配合量が、ゴム成分の総量に対して質量比で3~50%の範囲である請求項1~4の何れか1項に記載のUV硬化型組成物。
- 前記固体状のゴム成分として、ブタジエンゴムおよびスチレンブタジエンゴムから選択される少なくとも1種を含有する請求項1~5の何れか1項に記載のUV硬化型組成物。
- 請求項1~6の何れか1項に記載のUV硬化型組成物から形成された接着剤層を有するUV硬化型シート。
- 前記接着剤層の厚みが5~200μmである請求項7に記載のUV硬化型シート。
- 請求項1~6の何れか1項に記載のUV硬化型組成物の硬化物。
- 請求項7または8に記載のUV硬化型シートの硬化物。
- ゲル分率が50%以上である請求項9または10に記載の硬化物。
- 室温で高圧水銀灯により、積算光量1600mJ/cm2のUVを照射した後の、JISK-6854に基づく90度剥離力が4N/inch以上である請求項7または8に記載のUV硬化型シート。
- ジエン骨格を有するゴム成分を含有するUV硬化型シートであって、室温で高圧水銀灯により、積算光量1600mJ/cm2のUVを照射した後の、JISK-6251に基づく切断時引張強さが、25μm~50μmのシート厚みの範囲で3.5MPa以上であるUV硬化型シート。
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