JP3510722B2 - Method for manufacturing viscoelastic sheet - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a viscoelastic sheet. 2. Description of the Related Art In recent years, as a method for producing an adhesive tape, there has been a demand for environmental protection, such as switching from the use of a solvent-type adhesive to a water-based adhesive such as an emulsion-type adhesive, a hot-melt adhesive, or an ultraviolet polymerization. There has been a change to a solventless process for adhesive tapes using a mold adhesive or the like. [0003] The solvent-free process of the pressure-sensitive adhesive tape using the ultraviolet-curable pressure-sensitive adhesive or the like is carried out in addition to the above-mentioned environmental protection purpose, as described in, for example, Japanese Patent Publication No. 57-17030. In the process of producing a pressure-sensitive adhesive tape using a pressure-sensitive adhesive, it is possible to efficiently and efficiently produce a pressure-sensitive adhesive tape or a viscoelastic sheet having a thick-film pressure-sensitive adhesive layer, which has been low in productivity. Furthermore, in addition to the above, the solvent-free process of the adhesive tape using an ultraviolet-curable adhesive or the like, the monomer is polymerized by ultraviolet light after coating, so there is little restriction on the viscosity of the coating solution, It has become possible to increase the molecular weight of the agent and to manufacture a pressure-sensitive adhesive tape exhibiting high performance. However, the solvent-free process of the pressure-sensitive adhesive tape using the ultraviolet-curable pressure-sensitive adhesive or the like involves coating a photopolymerizable composition containing a low-viscosity monomer as a main component. It is necessary to increase the viscosity of the coating liquid composed of the photopolymerizable composition in order to obtain a coated film having an appropriate thickness. As a method for increasing the viscosity of the coating liquid, Japanese Patent Application Laid-Open No.
Japanese Patent No. 11684 discloses a thickening method by adding fumed silica. However, in the method of thickening the coating liquid by adding fumed silica or the like, the viscosity characteristics of the coating liquid become structural viscosity (thixotropic), and it is difficult to remove bubbles mixed during stirring or transport of the coating liquid. In addition, there is a disadvantage that the appearance quality of the obtained sheet is deteriorated and that the coating liquid has a strong dependency on the shear rate, so that the sheet is easily affected by the coating speed and the thickness accuracy of the coating film is reduced. The invention of claim 10 disclosed in Japanese Patent Publication No. 3-40752 discloses (1) producing a composition which can be polymerized into a pressure-sensitive adhesive state, and (2) producing the composition. At least 15% pores by (3) coating the foam on a backing, and (4) polymerizing the coated foam in situ to a pressure-sensitive adhesive state. 12. A method for producing a pressure-sensitive adhesive product comprising the steps of obtaining a pressure-sensitive adhesive film having a cellular structure comprising the method of claim 11, wherein the composition comprises a photoinitiator; 11. The method of claim 10, wherein (4) further comprises exposing to ultraviolet radiation. [0007] The pre-thickening method disclosed in Japanese Patent Publication No. 3-40752 discloses a coating liquid containing a crosslinking monomer having two or more unsaturated double bonds at the time of ultraviolet irradiation for thickening. Is gelled, so that it is necessary to carry out pre-thickening in a state where no crosslinkable monomer is contained, and then it is necessary to add a crosslinkable monomer. In particular, in the case where light pre-thickening is continuously performed in-line, it is necessary to continuously and uniformly mix only a small amount of a low-viscosity crosslinkable monomer into the photo-pre-thickened high-viscosity composition. This method leaves problems in accuracy and mixing operation itself and lacks stability in quality. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has as its object to provide a viscoelastic sheet which is easily and stable in quality by a single mixing process. It is to provide a manufacturing method of. According to the present invention, there is provided (a) 50 to 98% by weight of at least one (meth) acrylic acid ester of an alcohol having an alkyl group having 4 to 12 carbon atoms, and (b)
Monomers 50 to 2 copolymerizable with (a) having a polar group
With respect to 100 parts by weight of the monomer mixture consisting of
(C) 0.01 to 5 parts by weight of a crosslinking agent or a metal crosslinking agent having at least two functional groups selected from the group consisting of an aliphatic or alicyclic isocyanate group, an aziridinyl group, and an epoxy group; A photopolymerizable composition containing 0.01 to 5 parts by weight of an agent is preliminarily photopolymerized at a conversion of 1 to 50%, coated in a sheet form, and irradiated with ultraviolet rays on the coated sheet. The gist of the present invention is a method for producing a viscoelastic sheet. [0010] (a) 4 carbon atoms used in the present invention
Specific examples of the (meth) acrylate of an alcohol having an alkyl group of from 12 to 12 include n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, and (meth) acrylate. ) N-octyl acrylate, isononyl (meth) acrylate,
Lauryl (meth) acrylate and the like. These (meth) acrylates may be used alone or in combination of two or more. Glass transition temperature (Tg) of homopolymer
Is mainly composed of a (meth) acrylic acid ester having a temperature of −50 ° C. or lower, and (meth) acrylic acid of a lower alcohol such as methyl (meth) acrylate and ethyl (meth) acrylate is selected from the balance of tackiness and cohesiveness. Esters can be used in combination. The content of the (meth) acrylate (a) is 50 to 98% by weight, preferably 70 to 95% by weight. When the content of the above (a) is less than 50% by weight, the cohesive force becomes too strong, and the pressure-sensitive adhesiveness is reduced.
On the other hand, when the content of (a) exceeds 98% by weight, the cohesive strength becomes too low, and a high shear strength cannot be obtained. Examples of the monomer (b) copolymerizable with the polar group-containing (a) include a carboxyl group-containing monomer such as (meth) acrylic acid, maleic acid, fumaric acid, and itaconic acid, or an anhydride thereof; ) Hydroxy group-containing monomers such as 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, polyoxyethylene (meth) acrylate, polyoxypropylene (meth) acrylate, and modified caprolactone (meth) acrylate. . The monomer (b) copolymerizable with the polar group-containing (a) is used when the polymer is crosslinked by reacting with a crosslinking agent used in the present invention described below.
The content of the monomer (b) copolymerizable with the polar group-containing (a) is 50 to 2% by weight, preferably 20 to 2% by weight.
5% by weight. When the content of the above (b) exceeds 50% by weight, the cohesive strength becomes too strong, and the peeling adhesive strength decreases. If the content of (b) is less than 2% by weight, the cohesive strength is too low, and a high shear strength cannot be obtained. In order to improve the cohesion, (meth) acrylonitrile, N
Nitrogen-containing monomers such as -vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, (meth) acrylamide, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and dimethylaminopropylacrylamide may be contained. A crosslinking agent or metal crosslinking agent (c) having at least two functional groups selected from the group consisting of an aliphatic or alicyclic isocyanate group, an aziridinyl group and an epoxy group;
Is, as a polyfunctional aliphatic isocyanate-based cross-linking agent, for example, trimethylhexamethylene diisocyanate, as the polyfunctional alicyclic isocyanate-based cross-linking agent, for example, isophorone diisocyanate,
Examples of the polyfunctional aziridine-based cross-linking agent include N, N '
-Hexamethylene-1,6-bis (1-aziridinecarboxamide); examples of the polyfunctional epoxy crosslinking agent include 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N ', N'-
Tetraglycidyl-m-xylylenediamine and the like. Examples of the metal crosslinking agent include chelate compounds such as aluminum, titanium, and zinc. Two or more of these crosslinking agents may be used in combination. Since the aromatic isocyanate crosslinking agent causes polymerization inhibition by radicals being captured for a long time and disappearing in the electron cloud composed of the aromatic ring and the isocyanate group, the above-mentioned photo-preliminary thickening is impossible, and in the present invention, Is not used. In the present invention, the cross-linking agent having at least two aliphatic or alicyclic isocyanate groups refers to a cross-linking agent having at least two or more isocyanate groups, excluding aromatic isocyanate-based cross-linking agents for the above-mentioned reasons. Alternatively, it indicates that the crosslinking agent is limited to a crosslinking agent having at least two or more alicyclic isocyanate groups. The content of the crosslinking agent or metal crosslinking agent (c) having at least two functional groups selected from the group consisting of aliphatic or alicyclic isocyanate groups, aziridinyl groups and epoxy groups is 0.01 to 5%. Parts by weight, preferably 0.02 to 3 parts by weight. When the content of (c) is 0.
If the amount is less than 01 parts by weight, the degree of crosslinking is not sufficient, and the necessary cohesive strength cannot be obtained. If the content of (c) exceeds 5 parts by weight, the crosslink density increases and the cohesive strength increases. Too much pressure-sensitive adhesiveness is reduced. A part of the monomer mixture consisting of (a) and (b) in the photopolymerizable composition may be replaced with another monomer copolymerizable with (a) and (b). Other monomers copolymerizable with the above (a) and (b) include, for example, vinyl acetate, vinyl propionate, styrene, isobornyl (meth) acrylate and the like.
The content of these monomers is preferably 30% by weight or less based on the total amount of monomers in the monomer mixture. If the content exceeds 30% by weight, the cohesive force becomes too large, and the pressure-sensitive adhesiveness is reduced. The photopolymerization initiator (d) is not particularly restricted but includes, for example, 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl)
Ketone [for example, Ciba-Geigy, trade name: Darocure 2959], α-hydroxy-α, α'-dimethylacetophenone [for example, Ciba-Geigy, trade name:
Darocure 1173], methoxyacetophenone,
2,2-dimethoxy-2-phenylacetophenone [for example, Ciba-Geigy Co., trade name: Irgacure 65
1), acetophenone-based photopolymerization initiators such as 2-hydroxy-2-cyclohexylacetophenone [for example, trade name: Irgacure 184, manufactured by Ciba Geigy Co., Ltd.], ketal-based photopolymerization initiators such as benzyldimethyl ketal, halogenated ketones, Other photopolymerization initiators such as acylphosphine oxide and acylphosphonate can be exemplified. The content of the photopolymerization initiator (d) is 0.1.
It is 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight. When the content is less than 0.01 part by weight, the polymerization conversion rate is reduced and only a viscoelastic sheet having a strong monomer odor can be obtained. On the other hand, if the content exceeds 5 parts by weight, the amount of generated radicals increases, and the molecular weight decreases, so that the necessary cohesive strength cannot be obtained. The photopolymerizable composition having the above structure may be provided with a tackifying resin in order to improve the adhesion to an adherend such as a plastic having a small polarity, without departing from the spirit of the present invention. An additive such as (TF) or a filler or a chain transfer agent for polymerization may be contained. Examples of the TF include a rosin resin, a modified rosin resin, a terpene resin, a terpene phenol resin, C5 and C5.
A ninth petroleum resin, a hydrogenated product thereof, and a hydrogenated product of a coumarone resin may be used alone or in combination of two or more. However, these TFs usually have many phenolic or hydroquinone aromatic rings that inhibit photopolymerization, and therefore highly hydrogenated TFs are preferred. The photopolymerizable composition to which the above additives have been added is
If necessary, the amounts of the chain transfer agent and the crosslinking agent (c) are appropriately adjusted for adjusting the polymerization reaction. The chain transfer agent is used to adjust the molecular weight of the acrylic copolymer obtained by photopolymerization, and, for example, n-dodecyl mercaptan, t-dodecyl mercaptan and the like are preferably used. The amount of the chain transfer agent is in the range of 0.01 to 0.1 part by weight based on 100 parts by weight of all monomers of the photopolymerizable composition. Examples of the filler include glass bubbles and plastic beads. The above-mentioned photopolymerization (light prepolymerization) at a conversion of 1 to 50% is carried out by using a tank equipped with a stirrer provided with an ultraviolet irradiation window, and purging the tank with an inert gas such as nitrogen. The oxygen concentration is kept at 1,000 ppm or less, and the photopolymerizable composition is irradiated with ultraviolet rays while stirring. The light source of the ultraviolet irradiation device has a wavelength of 400
A lamp having a light emission distribution of not more than nm is used. Examples of the lamp include a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, and a metal halide lamp. The output of the ultraviolet irradiation device is set in consideration of the total amount of the photopolymerizable composition, the capacity of the tank, and the like, and is generally 100 mW to 200 W / cm.
Degree is used. As a method of performing the photoprepolymerization continuously and inline, while flowing the photopolymerizable composition in a pipe provided with an ultraviolet irradiation window, irradiating ultraviolet rays in the same manner as in the tank. Done. The monomer conversion in the above photoprepolymerization is from 1 to 50%. If the monomer conversion is less than 1%, the solution viscosity of the obtained photoprepolymerized photopolymerizable composition is suitable for coating. If the viscosity does not sufficiently rise, and if the monomer conversion exceeds 50%, the solution viscosity of the photopolymerizable composition subjected to photoprepolymerization becomes too high, or if the viscosity is suppressed low, the low molecular weight component may be reduced. Increases and reduces sticky properties. The appropriate coating viscosity is 100 to 10
It is 0000 cps. The method of applying the photopolymerizable composition subjected to the photoprepolymerization is not particularly limited, and examples thereof include a roll coater, a die coater, a bar coater, a comma coater, a gravure coater and a Meyer bar coater. This is performed using a coating device. Generally, a film thickness of 1 mm to
When coating thick about 5mm, the above light pre-polymerization,
The photopolymerizable composition having a viscosity of 10,000 to 50,000 cps is applied using, for example, a roll coater, a bar coater, a comma coater, a die coater, or the like. When the coating is applied to a very thin film having a thickness of several μm to 30 μm, the above-mentioned photo-prepolymerization is carried out,
The 1,000 cps photopolymerizable composition is applied using, for example, a gravure coater or a Meyer bar coater. At the time of the coating, it is effective to seal the coating portion with an inert gas such as nitrogen gas or carbon dioxide gas to suppress the inhibition of the subsequent polymerization reaction by oxygen, as in the case of the photopreliminary polymerization described above. Further, as a means for preventing the subsequent polymerization reaction from being inhibited by oxygen, a sheet-like photopolymerizable composition coated on a release-treated polyethylene terephthalate film or a fluororesin film is exposed to ultraviolet light. A transparent and the same kind of release-treated polyethylene terephthalate film or fluororesin film may be closely adhered and coated, and ultraviolet light may be irradiated from above the coated film. Further, a light-transmissive window in which the sheet-shaped photopolymerizable composition coated on the polyethylene terephthalate film or the fluororesin film subjected to the release treatment as described above is subjected to oxygen purging with an inert gas such as nitrogen or carbon dioxide gas. Ultraviolet rays may be applied while running or standing in an inert zone provided with. The range of the thickness of the viscoelastic sheet obtained by the method for producing a viscoelastic sheet of the present invention is not particularly limited.
A range of about mm is a preferable range. The viscoelastic sheet is obtained by irradiating the coated sheet coated with the above with ultraviolet rays, and the ultraviolet irradiating apparatus for irradiating the coated sheet is the same as that used in the photoprepolymerization. The same kind is used effectively.
Particularly, the chemical lamp efficiently emits light in the active wavelength region of the photopolymerization initiator, and the light absorption of substances other than the photopolymerization initiator of the photopolymerizable composition subjected to the photoprepolymerization is small, Since light penetrates into the inside of the coated sheet of the photopolymerizable composition, it is effective when manufacturing a product having a large film thickness. The irradiation intensity of ultraviolet rays on the coated sheet is as follows:
It is a main factor that determines the degree of polymerization of the acrylic copolymer, which is a main constituent component of the obtained viscoelastic sheet, and is appropriately set for each type of product. When a photopolymerization initiator of the cleavage type having an acetophenone group is used as the photopolymerization initiator, the irradiation intensity of the ultraviolet light is adjusted to a wavelength region effective for photodecomposition of the photopolymerization initiator (the type of the photopolymerization initiator). At 365 to 420 nm).
１００100 mW / cm. The irradiation time of the ultraviolet rays on the coated sheet is as follows:
It is about 60 to 600 seconds. When the irradiation time is 60 seconds or less, the polymerization is not sufficiently performed, the residual monomer is present, and not only the tackiness is reduced but also the monomer odor is strong. Although there is no particular problem if the irradiation time exceeds 600 seconds, 600 seconds is sufficient to complete the ultraviolet polymerization, and further irradiation is unnecessary. In the photopolymerization by the irradiation of the ultraviolet light, a light cut filter or the like is used to suppress the radiant heat from the lamp or to make the back surface of the coating sheet opposite to the irradiation surface pass through a cooling plate. The viscoelastic sheet obtained by heating and shrinking the release film for coating or the release film for cover which is coated on the coated sheet-shaped photopolymerizable composition is heated by rapid reaction heat. And the like can be prevented from being caused. The method for producing a viscoelastic sheet of the present invention is constituted as described above, so that the photopolymerizable composition can be treated with one liquid, and a very small amount of a low-viscosity crosslinkable monomer can be used. A simple raw material mixing process that does not require a mixing process that has a problem in the measurement accuracy and mixing operation itself, such as continuously and uniformly mixing with a high-viscosity composition that has been preliminarily thickened. A method for manufacturing a viscoelastic sheet of stable quality with high efficiency can be provided by a coating apparatus that includes the coating apparatus. Embodiments of the present invention will be specifically described below with reference to examples. In a five-necked flask equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel and a nitrogen gas inlet, 500 parts by weight of 2-ethylhexyl acrylate, 450 parts by weight of butyl acrylate, 50 parts by weight of acrylic acid, 10 parts by weight of 2-hydroxyethyl methacrylate, 30 parts by weight of hexamethylene diisocyanate, and 10 parts by weight of 2,2-dimethoxy-2-phenylacetophenone (trade name: Irgacure 651 manufactured by Ciba Geigy Co., Ltd.) From the atmosphere and dissolved oxygen were removed by purging with nitrogen gas. Next, the polymerizable composition was irradiated with 1 W / cm ² ultraviolet rays from a position 20 cm away from the wall surface of the flask using an ultraviolet irradiation device equipped with a black light lamp. As a result, the monomer conversion of the photopolymerizable composition obtained by photoprepolymerization was 6.2%, and the viscosity was 22%.
00 cps. The resulting photopolymerizable composition obtained by photoprepolymerization was subjected to a mold release treatment onto a 50 μm-thick polyethylene terephthalate film having a thickness of 0.5 ± 0.5 at the end of polymerization.
0.1 mm, coated with a roll coater, and further coated the coated surface with the release-treated polyethylene terephthalate film in close contact, and using an ultraviolet irradiation device equipped with a high-pressure mercury lamp, the coated film was coated. The position of the lamp was adjusted so that the above irradiation intensity was 10 mW / cm ^2, and ultraviolet light was irradiated for 3 minutes to produce a viscoelastic sheet. The amount of residual monomer in the obtained viscoelastic sheet was 0.1%.
The content was 1% or less, and there was no surface appearance quality defect due to wrinkles, bumps, or irregular thickness. Furthermore, after leaving the obtained viscoelastic sheet for 3 days, 0.2 g was weighed to obtain a sample, which was immersed in 50 g of tetrahydrofuran with stirring for 24 hours. The sample was filtered through a 200-mesh wire gauze, the residue on the wire gauze was dried in an oven at 110 ° C. for 3 hours, weighed, the percentage of the weight of the collected sample was taken as the gel fraction, and the value of 92% was taken as the gel fraction. Obtained. Example 2 500 parts by weight of 2-ethylhexyl acrylate, 450 parts by weight of butyl acrylate, 50 parts by weight of acrylic acid, N, N'-hexamethylene-1,6
-Bis (1-aziridinecarboxamide) 0.1 part by weight, 2,2-dimethoxy-2-phenylacetophenone (Ciba Geigy, trade name: Irgacure 651)
10 parts by weight were subjected to light prepolymerization in the same manner as in Example 1. The monomer conversion of the photopolymerizable composition obtained by photoprepolymerization was 5.5%, and the viscosity was 1800 cps. A viscoelastic sheet was prepared from the photopolymerizable composition obtained by photoprepolymerization in the same manner as in Example 1. The residual monomer content in the obtained viscoelastic sheet was 0.1% or less, and there was no surface appearance quality defect due to wrinkles, bumps, or irregular thickness. Further, the gel fraction of the obtained viscoelastic sheet was measured in the same manner as in Example 1, and was measured.
% Values were obtained. (Example 3) In place of 0.1 part by weight of N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide) of Example 2, 1,3-bis (N, N −
Photoprepolymerization was carried out in the same manner as in Example 2 except that 0.1 part by weight of (diglycidylaminomethyl) cyclohexane was used, and then a viscoelastic sheet was produced. The photopolymerizable composition obtained by the photoprepolymerization had a monomer conversion of 5.8% and a viscosity of 1900 cps. Further, the residual monomer amount in the obtained viscoelastic sheet is 0.1% or less,
The surface was free from defects in appearance quality due to wrinkles, bumps, and irregular thickness. Further, the gel fraction of the obtained viscoelastic sheet was measured in the same manner as in Example 1, and a value of 57% was obtained. Example 4 An aluminum acetylacetone chelate compound (Soken Chemical Co., Ltd.) was used in place of 0.1 part by weight of N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide) in Example 2. Product name: M1
2AT) Photoprepolymerization was performed in the same manner as in Example 2 except that 0.5 parts by weight was used, and then a viscoelastic sheet was produced. The photopolymerizable composition subjected to the photoprepolymerization had a monomer conversion of 5.7% and a viscosity of 1900 cps. Also, the amount of residual monomer in the obtained viscoelastic sheet is
The content was 0.1% or less, and there was no surface appearance quality defect due to wrinkles, bumps, or irregular thickness. Furthermore,
The gel fraction of the obtained viscoelastic sheet was measured in the same manner as in Example 1, and a value of 25% was obtained. (Comparative Example 1) A double bond is present at both molecular terminals instead of 0.1 part by weight of N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide) of Example 2. Photoprepolymerization was carried out in the same manner as in Example 2, except that 0.5 parts by weight of hexanediol acrylate diester was used. However, a gel-like substance was deposited on the photopolymerizable composition obtained by photoprepolymerization. However, during the measurement of the viscosity, it was wound around the rotating roller of the measuring instrument, and the measurement of the viscosity became impossible. A viscoelastic sheet was prepared in the same manner as in Example 2 using the photopolymerizable composition obtained by photopreliminary polymerization in which the gel substance was precipitated. The amount of the residual monomer in the obtained viscoelastic sheet is 0.1% or less, the number of bumps presumed to be caused by the gel-like substance occurs frequently, and the uneven coating is presumed to be caused by the gel-like substance. As a result, the thickness accuracy and the appearance quality were poor. Comparative Example 2 An adduct of tolylenediisocyanate of trimethylolpropane was used in place of 0.1 part by weight of N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide) in Example 2. Photoprepolymerization was carried out in the same manner as in Example 2 except that 30 parts by weight of a polymer (manufactured by Nippon Polyurethane Co., trade name: Coronate L) was used.
For more than a minute, the viscosity of the photopolymerizable composition did not increase, and neither a photopolymerizable composition nor a viscoelastic sheet that could be applied was obtained. Table 1 summarizes the monomer conversion and the viscosity of the photopolymerizable compositions obtained by the photoprepolymerization of the above Examples and Comparative Examples, the residual monomer content, the gel fraction and the appearance quality of the obtained viscoelastic sheet. Was. In addition, the viscosity measurement of the photopolymerizable composition by photopreliminary polymerization was performed using a B-type rotational viscometer. Further, those having no abnormality in the appearance quality of the viscoelastic sheet were indicated by a circle. [Table 1] Since the method for producing a viscoelastic sheet of the present invention is constituted as described above, the photopolymerizable composition can be treated with one liquid, and a very small amount of low-viscosity crosslinkable Simple mixing of raw materials without the need for a mixing process that has problems with metering accuracy and mixing operation itself, such as continuously and uniformly mixing monomers into a high-viscosity composition pre-thickened with light. A coating apparatus including a process can provide a method for efficiently producing a viscoelastic sheet of stable quality with high efficiency.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI C08J 7/04 C08J 7/04 Z // C08G 18/04 C08G 18/04 59/18 59/18 C09J 7/02 C09J 7 / JP-A-61-83274 (JP, A) JP-A-5-59338 (JP, A) JP-A-4-81482 (JP, A) JP-A-4-81479 (JP, A) JP-A-1-178567 (JP, A) JP-A-2-215878 (JP, A) JP-A-56-30410 (JP, A) JP-A-6-56932 (JP, A) JP-A-60-26074 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09J 7/00 B32B 27/00 C08F 2/50 C08F 20/04 C08F 20/12 C08J 7/04 C08G 18/04 C08G 59/18 C09J 7/02

Claims (1)

(57) [Claim 1] (a) 50 to 98% by weight of at least one kind of (meth) acrylic acid ester of an alcohol having an alkyl group having 4 to 12 carbon atoms, and (b) a polar group (C) a functional group selected from the group consisting of an aliphatic or alicyclic isocyanate group, an aziridinyl group and an epoxy group with respect to 100 parts by weight of a monomer mixture comprising 50 to 2% by weight of a monomer copolymerizable with (a) A photopolymerizable composition containing 0.01 to 5 parts by weight of a crosslinking agent or a metal crosslinking agent having at least two or more of (d) a photopolymerization initiator in an amount of from 1 to 50 parts by weight in advance. % Photopolymerized, coated in sheet form,
A method for producing a viscoelastic sheet, comprising irradiating the coated sheet with ultraviolet rays.