JPH0411610A - Photopolymerizable composition - Google Patents

Abstract

PURPOSE:To obtain the title composition which can give a high-molecular weight polymer even at an increased rate of polymerization by compounding a vinyl monomer based on an acrylic monomer and a specified photopolymerization initiator. CONSTITUTION:The title composition comprises a vinyl monomer based on an acrylic monomer (e.g. 2-ethylhexyl acrylate or acrylic acid) and a photopolymerization initiator of formula I or II, wherein R1 to R6 are each alkyl, R1 and R2 or R3 and R4 may be combined together to form a ring; Z is a (substituted) aromatic group, -Ar1-T-Ar2- (wherein Ar1 and Ar2 are each a (substituted)aromatic group; T is alkylene, carbonyl, O or S); Y is alkylene; and n is 2-10.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to photopolymerizable compositions. More specifically, the present invention relates to an acrylic photopolymerizable composition.

[Conventional technology]

A photopolymerizable composition consisting of an acrylic monomer and a photopolymerization initiator is known, and an acrylic viscoelastic product obtained by irradiating this acrylic photopolymerizable composition with light and polymerizing it is, for example, an acrylic adhesive. It is well known and is used as adhesives, acrylic adhesive tapes, acrylic adhesive sheets, double-sided adhesive tapes, heat-sensitive adhesive sheets, sealants, and adhesive processed products for foams. Since this acrylic viscoelastic product has an acrylic polymer as its main component, it has excellent light resistance, weather resistance, oil resistance, etc. This acrylic viscoelastic product is used as a plastic film, or acrylic adhesive tapes and films with paper, etc. on the surface of the base material have excellent adhesive performance such as adhesive force and cohesive force, and aging resistance such as heat resistance and weather resistance. Are better. Therefore, these products are widely used. Taking as an example an acrylic adhesive tape that is a typical product of these acrylic viscoelastic products, this adhesive tape generally has an acrylic monomer such as alkyl acrylate and/or alkyl methacrylate as its main component. A pressure-sensitive adhesive solution obtained by solution polymerizing a vinyl-based monomer in an organic solvent is coated or impregnated onto a base material, and then the adhesive solution is heated and dried. Alternatively, after emulsifying the vinyl monomers by placing them in water together with an emulsifier,
It is manufactured by coating or impregnating a base material with an emulsion obtained by polymerization and drying it by heating. Recently, a photopolymerizable composition in which a photopolymerization initiator such as benzoin methyl ether is contained in a vinyl monomer mainly composed of an acrylic monomer has been disclosed in US Patent No. 4.181.
, No. 752. In this US patent, this photopolymerizable composition layer is provided on a substrate, and ultraviolet rays with a wavelength of 300 to 400 nm are applied to the photopolymerizable composition at 0.1 to 7 mW.
A method is disclosed for producing an acrylic adhesive tape by irradiating with a light intensity of /cm'' and polymerizing it.

[Problem to be solved by the invention]

However, the method of polymerizing the vinyl monomer in an organic solvent requires a lot of energy because the adhesive solution is dried at high temperatures. There is a problem in that large-scale solvent recovery equipment is required to maintain safety to prevent the danger of In addition, methods using emulsions require more energy to evaporate water than when using organic solvents, and in terms of performance, water resistance is said to decrease due to emulsifiers mixed in when making emulsions. There's a problem. Furthermore, this method using an emulsion has the problem that water-soluble monomers cannot be used. The method of using a photopolymerizable composition produces adhesive tapes without using organic solvents or water, so the above-mentioned problems with using organic solvents and water are solved, and acrylic adhesives with good performance are produced. can be manufactured. However, with this method,
Since the polymerization reaction is slow, there is a problem of poor productivity for practical use. Generally, the polymerization rate of a photopolymerization reaction of a vinyl monomer such as an acrylic monomer is proportional to the square root of the product of a photopolymerization initiator and light intensity. Therefore, in order to increase productivity, the inventors tried to speed up the polymerization reaction rate by increasing the amount of photopolymerization initiator added or increasing the light intensity, but the molecular weight of the resulting polymer decreased. The balance between adhesive strength and cohesive strength of the adhesive tape cannot be maintained at a high level.
A good adhesive tape could not be manufactured. When the polymerization rate was increased for acrylic viscoelastic products other than adhesive tapes, similarly inferior products were produced. Therefore, an object of the present invention is to propose an acrylic photopolymerizable composition with good performance that does not cause a decrease in the molecular weight of the polymer even when the polymerization rate is increased.

[Means to solve the problem]

The present invention has been made to solve the above problems and achieve the above objects, and is directed to a photopolymerizable composition comprising a vinyl monomer containing an acrylic monomer as a main component and a photopolymerization initiator. As a photopolymerization initiator, the following structural formula [1
] or [1'] is used. atoms or sulfur atoms. R2 In structural formula [1], [1'], R,, R,, R3, Ra
, Rs and Rh are linear or branched alkyl groups, and even if both sets of R1 and RZ, R:l and R4, or any one set of them combine with each other to form a ring, good. Z is a substituted or unsubstituted aromatic group or one represented by the structural formula [2]. Moreover, Y is a linear or branched alkylene group. Art T Arz (2) In the structural formula [2], Ar, Arz are substituted or unsubstituted aromatic groups, and T is a linear or branched alkylene group, carbonyl group, oxygen. , acrylic monomer is a general term for alkyl acrylate and alkyl methacrylate.In the present invention, all of these acrylic monomers can be used, but acrylic monomers having an alkyl group having 1 to 14 carbon atoms are used. Monomers are preferably used.A more preferable range is acrylic monomers to which an alkyl group having 4 to 12 carbon atoms is bonded. Examples of these acrylic monomers include n-butyl acrylate, n- Examples include butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate, isooctyl methacrylate, isononyl acrylate, isononyl methacrylate, etc. In the present invention, these acrylic monomers are used singly or in combination. The vinyl monomer mainly composed of an acrylic monomer in the present invention may be the above acrylic monomer alone, or may be a mixture of the acrylic monomer and a vinyl monomer copolymerizable with the acrylic monomer. This means that the mixing ratio is preferably in the range of 60 to 100 parts by weight of the acrylic monomer and 0 to 40 parts by weight of the vinyl monomer.Suitable vinyl monomers that can be copolymerized with such acrylic monomers include: , acrylic acid, methacrylic acid,
Acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, N-substituted acrylamide, hydroxyethyl acrylate, N-vinylpyrrolidone,
Examples include maleic acid, itaconic acid, N-methylolacrylamide, hydroxyethyl methacrylate, and the like. When producing an adhesive, a polymer with a low glass transition point is preferred in view of the balance between adhesiveness and cohesiveness, and the above monomers are appropriately selected and used. That is, in the case of a homopolymer of acrylic monomers,
It is preferable to use a material having a glass transition point of 150°C or less. In the case of a copolymer, a copolymer of this acrylic monomer and a lower alkyl monomer or a copolymerizable vinyl monomer is preferable. Suitable vinyl monomers copolymerizable with acrylic monomers that form polymers with a low glass transition point include vinyl monomers such as tetrahydrofurfuryl acrylate, polyethylene glycol acrylate, polypropylene glycol acrylate, fluorine acrylate, and silicoacrylate. Monomers may be mentioned. In the present invention, the photopolymerization initiator represented by structural formula [1] or [1'] has two or more photo-induced cleavage points in one molecule. Therefore, when irradiated with light, polymerization starts from two or more cleavage points, increasing the polymerization rate.
Furthermore, this photopolymerization initiator is cross-linked to produce a polymeric viscoelastic product. As a result, high-speed production of acrylic viscoelastic products with excellent physical properties is possible. An example of a polymerization initiator having two or more photo-cleavage points is 4,4'-bis(α-hydroxy-2-isobutyryl).
Benzophenone 2-bis(4-(2-hydroxy-2-methyl-propanoyl)-phenyl)-ethanpo IJ(4-(α-hydroxyisobutyryl)-α-methylstyrene) 2,3-bis(4- (2-hydroxy-2-methylpropanoyl)-phenyl)-2,3-dimethyl-butane OCH3 1,1-bis(4-(2-hydroxy-2-methyl-propanoyl)-phenyl)-methane 3.4 -Bis(4-
(2-hydroxy-2-methyl-propanoyl)-phenyl)-3,4-dimethyl-hexane 4,4'-bis-(α-hydroxy-isobutyl)-diphenyloxide 4,4'-bis-(α- Examples include hydroxy-isobutyl) diphenyl sulfide. Furthermore, in the present invention, the photopolymerization initiator (1) or [1'] having two or more of these cleavage points may be used alone, but it may be used alone. A mixture of monofunctional photopolymerization initiators having one production point may be used. The mixing ratio of this monofunctional photopolymerization initiator is preferably within about 20% by weight. When the photopolymerization initiator represented by structural formula [1] or [1'] is used alone, if the light intensity is too low,
Depending on the composition of the photopolymerizable composition, gelation may occur and the adhesive strength may decrease. In such cases, gelation can be suppressed by using a monofunctional photopolymerization initiator in combination. Further, when these monofunctional photopolymerization initiators are used together, there is an advantage that high-speed polymerization can be achieved even if the concentration of the photopolymerization initiator having two or more cleavage points is low. Such monofunctional polymerization initiators include 4-(2hydroxyethoxy)phenyl (2-hydroxy 2-propyl) ketone: [Darocure-2959Lα-hydroxy-α・α′-dimethyl-acetophenone manufactured by Merck & Co., Ltd.] Examples include acetophenone types such as Glocure 1173), methoxyacetophenone, and 2,2-dimethoxy-2-phenylacetophenone, benzoin ether types such as benzoin ethyl ether and benzoin isopropyl ether, and ketal types such as benzyl dimethyl ketal. Furthermore, other examples include halogenated ketones, acylphosphinoxides, acyl phosphonates, and the like. In the photopolymerizable composition of the present invention, the mixing ratio of the vinyl monomer containing acrylic yarn as a main component and the photopolymerization initiator may be determined as appropriate; The best results can be obtained when a photopolymerization initiator containing a photopolymerization initiator as a main component is mixed in a proportion of 0.001 to 5 parts by weight based on 100 parts by weight of the monomer components. That is, if the amount of the photopolymerization initiator is less than 0.001 part by weight, the photopolymerization initiator is consumed by light energy at the initial stage of polymerization, so that unreacted polymers tend to remain, and seven polymers are likely to remain. Not only does the odor remain, but the cohesive strength decreases. On the other hand, if it exceeds 5 parts by weight, the polymerization reaction rate will increase, but the decomposition odor of the photopolymerization initiator will become intense, the molecular weight will vary widely, and the adhesive performance will deteriorate. When polymerizing the photopolymerizable composition of the present invention, due to adhesive properties,
The weight average molecular weight of the photopolymerized polymer is approximately 30 to 100.
It is preferable to adjust the range to about 50,000, and more preferably the range is about 50,000.
It is 0 to 1 million. Therefore, depending on the target molecular weight of the polymer, the type and amount of the photopolymerization initiator and the intensity of light are adjusted so that it falls within the above range. Furthermore, in the present invention, a photocrosslinking agent may be included in order to improve heat resistance, cohesive force at high temperatures, etc. Such photocrosslinking agents include hexanediol diacrylate, hexanediol dimethacrylate, ethylene glycol diacrylate, polyethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, propylene glycol diacrylate, polypropylene glycoyl diacrylate, and propylene glycol. Dimethacrylate, polypropylene glycol dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, pentaerythritol diacrylate, pentaerythritol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol triacrylate methacrylate, dipentaerythritol hexaacrylate,
Examples include dipentaerythritol hexamethacrylate. Furthermore, other examples include epoxy acrylate, polyester acrylate, and urethane acrylate. The preferred amount of the photocrosslinking agent added is
00 parts by weight, it is 5 parts by weight or less. By adding this photocrosslinking agent, crosslinking bonds are generated between polymer molecules during the photopolymerization reaction, and the heat resistance of the adhesive is improved. In the case of adhesive tapes, the cohesive force at high temperatures increases and the holding power at high temperatures improves. In the present invention, other additives commonly used in adhesives, such as thickeners, thixotropic agents, fillers, fillers, etc., may be added. As the thickener, acrylic rubber, epichlorohydrin rubber, etc. are used. Further, as the filler, calcium carbonate, titanium oxide, clay, etc. are used. In addition, as fillers, glass balloons, alumina balloons,
Examples include inorganic hollow bodies such as ceramic balloons, organic spherical bodies such as nylon beads, acrylic beads, and silicon beads, organic hollow bodies such as vinylidene chloride balloons and acrylic balloons, and single fibers such as polyester, rayon, and nylon. Products obtained by photopolymerizing the photopolymerizable composition of the present invention include acrylic adhesives, acrylic adhesive tapes, acrylic adhesive sheets, double-sided adhesive tapes, heat-sensitive adhesive sheets, sealing materials for buildings and automobiles, and vibration-proofing materials. Used for manufacturing various viscoelastic products such as interlayer films. In order to produce a viscoelastic product using the photopolymerizable composition of the present invention, the oxygen dissolved in the composition is usually removed to reduce the dissolved oxygen concentration in the photopolymerizable composition to 1 ppm or less. Thereafter, this photopolymerizable composition is irradiated with light to polymerize. To remove oxygen dissolved in this photopolymerizable composition, the photopolymerizable composition may be blown with an inert gas such as nitrogen gas, or phenyl diisodecyl phosphite, triisodecyl phosphite, octane, etc. A compound with an oxygen removing effect, such as a stannous acid, is added. By adding this compound with oxygen removal effect, sufficient polymerization (curing) can be achieved even if the atmospheric oxygen concentration is to some extent high (even if the atmospheric oxygen concentration is high to some extent). A double-sided adhesive tape without a base material can be produced by coating or injecting it onto a surface such as a plastic film, paper, cellophane, cloth, etc., photopolymerizing it by irradiating it with light, and peeling it off from a release paper or release form. When applied or impregnated onto a base material such as nonwoven fabric or metal foil, and photopolymerized by irradiating it with light,
A pressure-sensitive adhesive sheet is obtained in which a pressure-sensitive adhesive layer is provided on the surface of a base material. In addition, when manufacturing a sealant, a photopolymerizable composition is injected into a long and narrow mold with an inner surface that is easily releasable, and the composition is irradiated with light to polymerize, and then the polymer is removed from the mold. The sealant is ready. When applying, impregnating, or injecting a photopolymerizable composition onto molds, substrates, etc., it is possible to thicken the photopolymerizable composition by adding an extender or thixotropic agent so that the work can be carried out smoothly. preferable. In addition to adding an extender or a thixotropic agent as described above, another method for thickening a photopolymerizable composition is to irradiate the photopolymerizable composition with a small amount of ultraviolet light to preliminarily dissolve the monomer components. There is a method of partial polymerization. For this coating, impregnating, or injecting operation, an apparatus designed to prevent contact with air (oxygen) is used so that the dissolved oxygen concentration in the photopolymerizable composition does not become high. After coating, impregnating or injecting onto a mold, substrate, etc., the photopolymerizable composition is transferred into a photopolymerization chamber, where the photopolymerizable composition is irradiated with light and polymerized. Typically, the photopolymerization chamber introduces an inert gas to reduce the atmospheric oxygen concentration and prevent the dissolved oxygen concentration in the photopolymerizable composition from increasing during photopolymerization. Alternatively, as a method other than introducing an inert gas, the surface of the photopolymerizable composition whose dissolved oxygen concentration has been reduced is covered in advance with a film with low oxygen permeability such as a polyester film, and the composition is passed through a photopolymerization chamber. There is a way. In this way, oxygen will not dissolve into the photopolymerizable composition even if it is not inside the photopolymerization chamber where the atmospheric oxygen concentration is reduced. In this case, it is preferable to add a compound having an oxygen removing effect. In the present invention, the composition is polymerized by light, and the light used at this time is electromagnetic waves such as visible light, ultraviolet rays, and electron beams. Usually ultraviolet light is used. The photopolymerization chamber is made of a material whose top surface is transparent to light. For example, if the irradiation light is ultraviolet rays, the material is made of a material that transmits ultraviolet rays, such as quartz glass, pyrex glass, or boric acid glass, and the ultraviolet rays are irradiated from the top surface of this photopolymerized material through the material that transmits ultraviolet rays. Ru. As an ultraviolet lamp that emits this ultraviolet light, one having a spectral distribution in the wavelength range of 300 to 400 nm is usually used. Such ultraviolet lamps include chemical lamps, blank light lamps (trade name of Toshiba Denzai ■), low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, microwave-excited mercury lamps, and the like. The first two lamps are used when emitting relatively low light intensity, and the second lamp is used when emitting relatively high light intensity. The light intensity is generally about 5 to 300 mW/cm'' on the surface of the irradiated object by adjusting the distance to the irradiated object and the voltage, and the irradiation time is preferably about 0.3 to 5 minutes. Irradiation with light polymerizes the acrylic monomer-based monomer component to obtain a viscoelastic product.Usually, with the above light intensity and irradiation time, the residual monomer is 0.
．． The product contains 5% by weight or less. This level of remaining children
usually does not adversely affect the performance of viscoelastic products. Incidentally, the light irradiation may be carried out at a constant light intensity during the polymerization period, but the light irradiation may also be carried out in two or more stages, each with a different light intensity. By performing polymerization in two or more stages in this way, the physical properties of the viscoelastic product can be adjusted more precisely.

[For use]

The present invention is a photopolymerizable composition in which a monomer component containing an acrylic monomer as a main component contains a specific photopolymerization initiator having two or more photo-cleavage points in one molecule. When a photopolymerization composition containing such a specific photopolymerization initiator is irradiated with light, this photopolymerization initiator is cleaved to generate radicals, and the above monomer components are rapidly polymerized, resulting in a very small amount of residual monomer. A low molecular weight viscoelastic product is produced. The mechanism of polymerization of the viscoelastic product obtained in this way is not necessarily clear, but when a compound with two or more photo-cleavage points in one molecule is used as a photopolymerization initiator, the cleavage creates polyfunctional radicals. is born. Polymer molecules grow from this multifunctional radical as a starting point, and the radicals recombine at a certain point to form a polymer, but the length of the resulting polymer from the starting point to the reaction termination point is Even if the strength is high or the number of photoinitiators is large, and the polymerization is shortened as in the case of conventional monofunctional photoinitiators, each polymer molecule starts from the initiator and becomes a polyfunctional radical. It is presumed that the polymer as a whole has a high molecular weight because it stretches in three directions.

【Example】

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. (Measurement of physical properties) For the double-sided adhesive tapes obtained in Examples and Comparative Examples, the weight average molecular weight of the adhesive (measured only when no photocrosslinking agent is added), amount of residual monomer, and gel content were measured using the following measuring methods. The rate/swelling degree, adhesive strength, and holding power were measured. (1) Weight average molecular weight A sample solution obtained by dissolving in tetrahydrofuran and leaving it for 24 hours, excluding insoluble matter, is measured by gel permeation chromatography (GPC) using a refractive index detector using standard polystyrene as a reference. did. (2) Residual amount of polyethylene glycol (Product name 2 manufactured by Gascro Kogyo Co., Ltd.)
The measurement was performed using a separation column in which chromosorb- carrying 0M) was treated with an acid, and a gas chromatograph (GC-6A, manufactured by Shimadzu Corporation) equipped with a hydrogen flame ionization detector. The sample for measurement was obtained by collecting 2 cc of a solution of 100 mg of the adhesive sample dissolved in 5 cc of methyl acetate, and mixing 2 cc of this solution with 2 cc of an internal standard solution in which 2-ethylhexyl methacrylate was dissolved in methyl acetate. Adjusted. (3) Gel fraction/swelling degree Dissolve the adhesive sample ioomg in tetrahydrofuran,
Let stand for 24 hours and filter through a 200 mesh stainless steel filter. It was determined by measuring the weight of the filtered swollen gel and the weight of the dried gel obtained by drying the swollen gel at 100°C for 2 hours. (4) Adhesive strength Paste a 25 μm thick polyester film on one side of double-sided adhesive tape to make an adhesive tape with a width of 25 mm and a length of 300 mm, and then attach one end of the tape to a steel plate polished with 4280 sandpaper. length 100-120m
M section was placed and pasted by moving a 2 kg roller back and forth once, and at 23°C and 165% RH, the other end of this tape was pasted at a 180 degree angle using an Instron tensile tester at a speed of 300 mm/min. The film was peeled off in the opposite direction, and the peel resistance at that time was measured and defined as adhesive strength (g/mm width). (5) Holding power Attach aluminum foil with a thickness of 100 μm to one side of the double-sided adhesive tape to make an adhesive tape with a width of 25 mm.
Place one end of the tape on a steel plate polished with No. 280 sandpaper so that the adhesive area is 25 mm in width and 25 mm in length, and paste it by making one reciprocation with a 2 kg roller. A 1 kg weight was fixed to the other end, this was hung in an atmosphere of 100°C, and the time until the weight fell together with the tape was measured to determine the holding force (time). Note that this holding force is normally measured at 40°C, but in this measurement, it was measured under harsh conditions of 100°C and the measurement time was shortened. Moreover, the measurement was discontinued after a maximum of 150 hours. (Example 1) To 100 parts by weight of a monomer component consisting of 97% by weight of 2-ethylhexyl acrylate and 3% by weight of acrylic acid,
Add 1.0 parts by weight of 4,4'-bis(α-hydroxy-imbutyryl)-benzophenone, a prototype product of Merck Co., Ltd. (this compound will be abbreviated as Pl from now on), and stir with a stirrer to mix uniformly. A photopolymerizable composition was produced. The resulting photopolymerizable composition was blown with nitrogen gas to remove dissolved oxygen, and then impregnated into a nylon nonwoven fabric placed on a transparent polyester film treated with a release agent, and its plane was covered with the same film as above. This was passed through a squeeze roll of an applicator to create a laminate with a uniform thickness. The light intensity radiated from the ultra-high pressure mercury lamp to this laminate is 2
A double-sided adhesive tape with a film thickness of 220 μm was manufactured by irradiating light of 5 mW/cm" (center wavelength: 365 nm). The adhesive of this double-sided adhesive tape has 99.7% of the monomer polymerized, and is substantially Polymerization was completed. The time required at this time was 1.5 minutes. The gel fraction of the obtained polymer was 22%, the degree of swelling of the polymer excluding gel was 45, and the weight average molecular weight was 33. (Comparative Example 1) Monofunctional Darocure-1173 (α
-Hydroxy-α,α′-dimethyl-acetophenone;
When a double-sided adhesive tape was prepared in the same manner as in Example 1, except that the amount was changed to 0.4 parts by weight, the time required for completion of polymerization was 1.5 minutes. The result was the same as in the example, but the weight average molecular weight of the obtained polymer was only 180,000 (and the cohesive force (holding force) was small. (Comparative Example 2) The amount of Glocure-1173 was reduced to 0. A double-sided adhesive tape was prepared in the same manner as in Comparative Example 1, except that the amount was 8 parts by weight.The time required to complete polymerization was 0.7 minutes, which was faster than in the example, but the weight of the obtained polymer The average molecular weight is 14
It was as small as 1,000,000 and had no cohesive force (holding force). (Examples 2 to 5) To 100 parts by weight of a monomer component consisting of 97 parts by weight of 2-ethylhexyl acrylate and 3 parts by weight of acrylic acid,
Add 1.0 parts by weight of a photopolymerization initiator (PI), and further add 0 (not added), 0.05, 0.10, and 0.20 parts by weight of hexanediol diacrylate as a photocrosslinking agent, respectively. A liquid syrup-like photopolymerizable composition was prepared by uniformly stirring. A double-sided adhesive tape was prepared using this photopolymerizable composition in the same manner as in Example 1. The light intensity of the lamp at this time was 25 mW/cm" and the irradiation time was 1.5 minutes. The results are shown in Table 1. As is clear from Table 1, according to the present invention, the fast reaction A polymer with excellent holding power can be obtained even in the case of using a photopolymerization initiator, and even better adhesive properties can be obtained by adding a photocrosslinking agent. (Comparative Examples 3 to 6) As a photopolymerization initiator, Darocure -1173 was added in an amount of 0.4 parts by weight, and 0 (not added) and 0.10.0.
20.0.40 parts by weight was added to increase the light intensity to 25 mW/
cm” and the irradiation time was 1.5 minutes, double-sided adhesive tapes were prepared in the same manner as in Examples 2 to 5. The physical properties of the double-sided adhesive tapes thus prepared were evaluated, and their The results are shown in Table 1. In the case of Comparative Examples 3 to 6, since the molecular weight of the main chain polymer was small, the adhesive force was high in the non-crosslinked state, but the holding force was low;
On the other hand, in the crosslinked state, the adhesive force was low and interfacial destruction was likely to occur, so the holding force was also low.

【Effect of the invention】

The photopolymerizable composition of the present invention is composed of a vinyl monomer mainly composed of acrylate photon additives, so when it is photopolymerized, it becomes a viscoelastic product with excellent light resistance, weather resistance, oil resistance, etc. A viscoelastic product using this as an adhesive tape is extremely useful as it has excellent adhesive performance such as adhesive force and cohesive force, heat resistance, and weather resistance. Furthermore, since the photopolymerizable composition of the present invention contains a photopolymerization initiator that has two or more photo-induced cleavage points in one molecule, when this composition is irradiated with light, even under high-speed reaction conditions, it has a high molecular weight. Because it produces a polymer of It is. Furthermore, when the present invention is applied to, for example, the production of adhesive tapes, there is no need for solvents or drying energy solvent recovery equipment as in conventional methods, so production can be performed at low cost through a simple process that saves resources and energy. becomes. Furthermore, since the photopolymerizable composition of the present invention does not use an emulsifier, it is possible to produce viscoelastic products with good water resistance.

Claims (1)

[Claims] (1) In a photopolymerizable composition consisting of a vinyl monomer whose main component is an acrylic monomer and a photopolymerization initiator, the photopolymerization initiator is represented by the following structural formula [1] or [1'
] A photopolymerizable composition characterized by using a photopolymerization initiator represented by the following. ▲There are mathematical formulas, chemical formulas, tables, etc.▼[1] ▲There are mathematical formulas, chemical formulas, tables, etc.▼[1'] In structural formulas [1], [1'], R_1, R_2, R_3,
R_4, R_5, R_6 are linear or branched alkyl groups, and both sets of R_1 and R_2, R_3 and R_4,
Alternatively, any one pair thereof may be bonded to each other to form a ring. Z is a substituted or unsubstituted aromatic group or structural formula [2]
This is shown in . Moreover, Y is a linear or branched alkylene group. -Ar_1-T-Ar_2-[2] In structural formula [2], Ar_1 and Ar_2 are substituted or unsubstituted aromatic groups, and T is a linear or branched alkylene group, carbonyl group, oxygen atoms or sulfur atoms.