JPH0320402B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to photopolymerizable compositions.
In particular, the present invention relates to a photopolymerizable composition that exhibits high sensitivity to light sources in the visible region. Conventionally, many image forming methods using photopolymerization systems have been known. agent,
A photosensitive material is prepared by preparing a photopolymerizable composition consisting of a colorant, a plasticizer, etc., and applying the photopolymerizable composition without a solvent or as a solution onto a support to provide a layer of the photopolymerizable composition. A method in which a cured relief image is formed by imagewise exposing a desired image, polymerizing and curing the exposed portion, and dissolving and removing the unexposed portion; A method in which a polymerizable composition layer is provided, and an image is formed by imagewise exposure from the side of the transparent support to induce a change in adhesive strength due to light, and then peeling off the support. There are image creation methods that utilize changes in toner adhesion due to Conventionally, benzoin, benzoin alkyl ether, benzophenone, anthraquinone, benzyl, Michler's ketone, etc. have been used as photopolymerization initiators for photopolymerizable compositions applied to such methods. However, the ability of these photoinitiators to initiate photopolymerization against a light source in the visible light region of 400 nm or more is significantly lower than that with a light source in the ultraviolet region of 400 nm or less, and therefore, the ability of photopolymerization initiators containing them to initiate photopolymerization is significantly lower. The scope of application has been severely limited. Several proposals have been made regarding photopolymerization systems sensitive to visible light. Formerly US Patent No.
No. 2850445 reports that certain photoreducible dyes, such as rose bengal, eosin, erythrosin, riboflavin, etc., have effective visible light sensitivity. Later, as an improved technology, a composite initiation system of dye and aliphatic amine (Special Publication No. 44-20189),
A system of hexaarylbiimidazole, a radical generator and a dye (Japanese Patent Publication No. 45-37377), a system of hexaarylbiimidazole and p-dialkylaminobenzylidene ketone (Japanese Patent Publications No. 47-2528, No. 54)
-155292) Hexaarylbiimidazole and indanone system (JP-A-155292), cyclic cis-α
- Dicarbonyl compound and dye system (Unexamined Japanese Patent Publication No. 1973-
84183) and a system of substituted triazine and merocyanine dyes (Japanese Patent Application Laid-Open No. 151024-1983).
Although these techniques are certainly effective for visible light, their photosensitivity is still not fully satisfactory, and further improved techniques have been desired. As a result of intensive studies aimed at improving the problems of the above-mentioned prior art, the present inventors discovered that the intended purpose could be achieved by using a photopolymerization initiation system consisting of a specific combination. He has completed his invention. That is, the gist of the present invention is to provide a photopolymerizable composition comprising an addition-polymerizable compound having at least one ethylenically unsaturated double bond and a photopolymerization initiation system, wherein the photopolymerization initiation system comprises (a) a general formula [In the formula, R ¹ and R ² represent an alkyl group, Ring A and Ring B represent a benzene ring or a naphthalene ring which may have a substituent, X ^- represents an anion, and n is 0 or 1 is shown. ], and (b) general formula [In the formula, R ³ , R ⁴ and R ⁵ are an alkyl group or an aryl group which may have a substituent, or
Alkenyl group, piperidino group, -NR ₂ , -OR, -
SR (Here, R represents a hydrogen atom or an alkyl group.)
, at least one of which represents a mono-, di- or trihalogen-substituted methyl group. ] A photopolymerizable composition comprising an s-triazine derivative represented by the following. The present invention will be explained in detail below. The photopolymerization initiation system, which is the first essential component in the photopolymerizable composition of the present invention, will be explained. The photopolymerization initiation system generates radicals by irradiation with actinic rays and brings about an addition polymerization reaction of a compound having an ethylenically unsaturated bond, which will be described later. The photopolymerization initiation system of the present invention consists of a combination of two types of components, the first component (a) of which is a cyanine dye represented by the above general formula (). When sensitivity is considered, it is preferable that at least one of ring A and ring B in the general formula () is a naphthalene ring which may be substituted with a substituent such as an alkyl group. Specifically, for example, 1,1-bis(3-methyl-2-benzothiazole) methinecyanine,
1,1-bis(3-ethyl-2-benzothiazole)methincyanine, 1-(3-methyl-2-α
-naphthothiazole)-1-(3-methyl-2-benzothiazole) methine cyanine, 1-(3-ethyl-2-α-naphthothiazole)-1-(3-ethyl-2-benzothiazole) methine cyanine,
1-(3-ethyl-2-β-naphthothiazole)-
1-(3-ethyl-2-benzothiazole) methinecyanine, 1,1-bis(3-methyl-2-α
-naphthothiazole) methinecyanine, 1,1-
Bis(3-ethyl-2-α-naphthothiazole)
Methinecyanine, 1-(3-ethyl-2-α-naphthothiazole)-1-(3-ethyl-2-β-naphthothiazole)methyncyanine, 1,1-bis(3-methyl-2-β-naphthothiazole) Methinecyanine, 1,1-bis(3-ethyl-2-β
-naphthothiazole) methinecyanine, 1,3-
Bis(3-methyl-2-benzothiazole) trimethine cyanine, 1-(3-methyl-2-β-naphthothiazole)-3-(3-methyl-2-benzothiazole) trimethine cyanine, 1,3- Examples include bis(3-methyl-2-β-naphthothiazole) trimethine cyanine. Particularly preferred is 1,1-bis(3-
Examples include ethyl-2-α-naphthothiazole) methinecyanine and 1,1-bis(3-methyl-2-β-naphthothiazole)methyncyanine. Examples of the counter anion X ^- in the general formula () include halogen anions such as C ^- , Br ^- , and I ^- , inorganic anions such as CO ₄ ^- , BF ₄ ^- , and PF ₆ ^- , and CH ₃ SO ₄ ^-. ,

[Formula] Examples include organic anions such as CH ₃ COO ^- , and any of these can be suitably used. The cyanine dye used in the present invention is, for example, J.
D.Kendall et al, J.chem.Soc., 1503, (1949)
and Brooker et al, J.Am.Chem.Soc., 57 ,
547 (1935), etc.,
It can be synthesized using the corresponding 2-methylbenzo(naphtho)thiazole and 2-mercaptobenzo(naphtho)thiazole as raw materials. The second component (b) is an s-triazine derivative in which at least one mono-, di-, or trihalogen-substituted methyl group represented by the general formula () is bonded to an s-triazine ring. .
Chem.Soc.Japan, 42 , 2924, (1969), US Patent
No. 3987037, FCSchaefer et al, J.Org.
Chem., 29 , 1527, (1964). Specifically, 2,4,6-tris(trichloromethyl)-s-triazine, 2-methyl-
4,6-bis(trichloromethyl)-s-triazine, 2-phenyl-4,6-bis(trichloromethyl)-s-triazine, 2-(p-chlorophenyl)-4,6-bis(trichloromethyl)- s-
Triazine, 2-(2,4-dichlorophenyl)-
4,6-bis(trichloromethyl)-s-triazine, 2-(p-bromphenyl)-4,6-bis(trichloromethyl)-s-triazine, 2-(p-bromphenyl)-4,6-bis(trichloromethyl)-s-triazine
-tolyl)-4,6-bis(trichloromethyl)-
s-triazine, 2-(p-methoxyphenyl)-
4,6-bis(trichloromethyl)-s-triazine, 2-n-propyl-4,6-bis(trichloromethyl)-s-triazine, 2-(α,α,β
-trichloroethyl)-4,6-bis(trichloromethyl)-s-triazine, 2-styryl-4,
6-bis(trichloromethyl)-s-triazine,
2,4,6-tris(dichloromethyl)-s-triazine, 2,4,6-tris(monochloromethyl)-s-triazine, 2-(p-methoxystyryl)-4,6-bis(trichloromethyl)- s-triazine, 2,4,6-tris(tribromomethyl)-s-triazine, 2-methyl-4,6-bis(tribromomethyl)-s-triazine, 2,
4,6-tris(dibromomethyl)-s-triazine, 2-methoxy-4,6-bis(tribromomethyl)-s-triazine, 2-amino-4,6
-bis(tribromomethyl)-s-triazine,
Examples include 2-piperidino-4,6-bis(tribromomethyl)-s-triazine. Particularly preferred are 2,4,6-tris(trichloromethyl)-s-triazine, 2-phenyl-4,6-
Bis(trichloromethyl)-s-triazine, 2
-Methyl-4,6-bis(trichloromethyl)-
Examples include s-triazine, 2,4,6-tris(tribromomethyl)-s-triazine, and the like. These can be synthesized by reacting the corresponding nitrile compound with aluminum bromide in the presence of hydrogen chloride or via the corresponding imidate, according to the above-mentioned literature. The photopolymerization initiation system of the present invention can only exhibit remarkable effects by combining the two components (a) and (b) described above, and the ratio of their use is 1:10 to 10:1 by weight.
preferably from 1:4 to 4:1. The photopolymerization initiation system contained in the photopolymerizable composition of the present invention is preferably 0.1% to 30% by weight of the addition polymerizable compound having at least one ethylenically unsaturated double bond. ranges from 0.5% to 20%. Next, at least one ethylenically unsaturated double bond, which is the second essential component of the photopolymerizable composition of the present invention, is added.
The addition-polymerizable compound possessed by the compound will be explained. When the photopolymerizable composition is irradiated with actinic rays, the compound undergoes addition polymerization due to the action of the photodecomposition product of the photopolymerization initiation system, which is the first essential component, thereby curing and substantially rendering it insolubilized. It is a monomer having an ethylenically unsaturated double bond such as the one that gives rise to the formation of a compound, or a polymer having an ethylenically unsaturated double bond in its side chain or main chain. In addition, what is meant by monomer in the present invention is a concept that is opposed to a so-called polymer substance, and therefore includes dimers, trimers, and oligomers in addition to monomers in the narrow sense. It is. Examples of monomers having ethylenically unsaturated bonds include unsaturated carboxylic acids, esters of unsaturated carboxylic acids and aliphatic polyhydroxy compounds, esters of unsaturated carboxylic acids and aromatic polyhydroxy compounds, and unsaturated carboxylic acids. Examples include esters obtained by an esterification reaction between a polyhydric carboxylic acid and a polyhydric hydroxy compound such as the aforementioned aliphatic polyhydroxy compound or aromatic polyhydroxy compound. Specific examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, and maleic acid. Examples of aliphatic polyhydroxy compounds include dihydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, neopentyl glycol, propylene glycol, and 1,2-butanediol, trimethylolethane, trimethylolpropane, and glycerol. These include trihydric alcohols such as, tetrahydric or higher alcohols such as pentaerythritol and tripentaerythritol, and polyhydric hydroxycarboxylic acids such as dihydroxymaleic acid. Examples of aromatic polyhydroxy compounds include hydroquinone, resorcinol, catechol, and pyrogallol. Examples of polycarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, tetrachlorophthalic acid, trimellitic acid, pyromellitic acid, benzophenone dicarboxylic acid, maleic acid, fumaric acid, malonic acid, glutaric acid, adipic acid, and sebacic acid. , tetrahydrophthalic acid, etc. Specific examples of esters of aliphatic polyhydroxy compounds and unsaturated carboxylic acids include ethylene glycol diacrylate, triethylene glycol diacrylate, tetramethylene glycol diacrylate, trimethylolpropane triacrylate, trimethylolethane triacrylate, and pentaerythritol. Acrylic acid esters such as diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, tripentaerythritol octaacrylate, glycerol diacrylate, triethylene glycol diacrylate, etc. Methacrylate, tetramethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetraacrylate, dipentaerythritol dimethacrylate,
dipentaerythritol trimethacrylate, dipentaerythritol tetramethacrylate, tripentaerythritol octamethacrylate,
Ethylene glycol dimethacrylate, 1,2-
Methacrylic acid esters such as butanediol dimethacrylate and sorbitol tetramethacrylate, ethylene glycol diitaconate, propylene glycol diitaconate, 1,2-butanediol diitaconate, tettomethylene glycol diitaconate, pentaerythritol triitaconate Itaconic acid esters such as ethylene glycol dicrotonate, diethylene glycol dicrotonate, crotonic acid esters such as pentaerythritol tetracrotonate, maleic acids such as ethylene glycol dimaleate, triethylene glycol dimaleate, pentaerythritol dimaleate, etc. There is an ester. Examples of esters of aromatic polyhydroxy compounds and unsaturated carboxylic acids include hydroquinone diacrylate, hydroquinone dimethacrylate, resorcin diacrylate, resorcin dimethacrylate, and pyrogallol triacrylate. The ester obtained by the esterification reaction of an unsaturated carboxylic acid with a polyhydric carboxylic acid and a polyhydric hydroxy compound is not necessarily a single product, but typical examples are shown in Table 1. Z in the table represents an acryloyl group or a methacryloyl group.

[Table] Examples of other compounds having ethylenically unsaturated double bonds that can be used in the present invention include acrylamides such as acrylamide, ethylenebisacrylamide, hexamethylenebisacrylamide, ethylenebismethacrylamide, hexamethylenebismethacrylamide, etc. Examples include allyl esters such as methacrylamides, diallyl phthalate, diallyl malonate, diallyl fumarate, and triallylisocyanurate, and vinyl-containing compounds such as divinyl adibate, divinyl phthalate, and ethylene glycol divinyl ether. Polymers having ethylenically unsaturated bonds in the main chain include, for example, polyesters obtained by a polycondensation reaction of unsaturated dihydric carboxylic acids and dihydroxy compounds;
Examples include polyamides obtained by a polycondensation reaction of unsaturated dihydric carboxylic acids and diamines. These polymers used in the present invention usually have a molecular weight of 10,000 to 100,000. Examples of unsaturated dihydric carboxylic acids include maleic acid and fumaric acid. Polymers having ethylenically unsaturated bonds in their side chains include dicarboxylic acids having unsaturated bonds in their side chains, such as itaconic acid, α-methyl itaconic acid, γ-methyl itaconic acid, propylidenesuccinic acid, and α-ethylidene glycol. Examples include polyester obtained by a polycondensation reaction of tannic acid, ethylidenemalonic acid, propylidenemalonic acid, etc. with a dihydroxy compound, and polyamide obtained by a polycondensation reaction of a diamine. Also suitable are polymers obtained by a polymer reaction between a polymer having a reactive functional group such as a hydroxyl group or a halogenated methyl group in its side chain and an unsaturated carboxylic acid such as (meth)acrylic acid or crotonic acid. It can be used for Examples of polymers having functional groups having reactive activity include polyvinyl alcohol, copolymers of vinyl alcohol and vinyl acetate, copolymers of vinyl alcohol and acrylonitrile, styrene, vinyl chloride, vinylidene chloride, etc., polyepichlorohydrin, Copolymers of 2-hydroxyethyl methacrylate and acrylonitrile, methyl methacrylate, butyl methacrylate, styrene, vinylidene chloride, vinyl acetate, etc., obtained by reaction of epichlorohydrin and 2,2-bis(4-hydroxyphenyl)-propane Examples include polyether, poly(4-hydroxystyrene), poly(N-methylolacrylamide), and the like. Among the addition-polymerizable compounds having at least one ethylenically unsaturated double bond described above, monomers of acrylic esters or methacrylic esters can be particularly preferably used. The photopolymerizable composition of the present invention contains the above-described photopolymerization initiation system and a compound having an ethylenically unsaturated bond as essential components. An organic polymer substance can be further added as an agent. The binder may be appropriately selected depending on the purpose of improving compatibility, film-forming properties, developability, adhesion, etc. Specifically, for example, to improve water-based developability, (meth)acrylic acid copolymers, itaconic acid copolymers, partially esterified maleic acid copolymers, acidic cellulose modified products having carboxyl groups in side chains, polyethylene oxide, Polyvinylpyrrolidone, etc. are used, and to improve film strength and adhesion, polyethers of epichlorohydrin and bisphenol A, soluble nylon, polyalkyl methacrylates such as polymethyl methacrylate, polyalkyl acrylates, and alkyl methacrylates are used. and acrylonitrile, acrylic acid, methacrylic acid,
Copolymers of vinyl chloride, vinylidene chloride, styrene, etc., copolymers of acrylonitrile and vinyl chloride, vinylidene chloride, vinylidene chloride, chlorinated polyolefins, copolymers of vinyl chloride and vinyl acetate, polyvinyl acetate, acrylonitrile and styrene copolymers, acrylonitrile and butadiene, styrene copolymers, polyvinyl alkyl ethers, polyvinyl alkyl ketones, polystyrene, polyamides, polyurethanes, polyethylene terephthalate isophthalate, acetyl cellulose polyvinyl butyral, and the like. The weight ratio of these binders to the compound having an ethylene bond is 500% or less, preferably 200%.
% or less. The photopolymerizable composition of the present invention may further contain thermal polymerization inhibitors, colorants, plasticizers, surface protectants, smoothing agents, coating aids, etc., as required. Examples of thermal polymerization inhibitors include hydroquinone,
Examples of colorants include p-methoxyphenol, pyrogallol, catechol, 2,6-di-t-butyl-p-cresol, and β-naphthol. Examples of colorants include phthalocyanine pigments, azo pigments, carbon black, and titanium oxide. There are pigments, triphenylmethane dyes, azo dyes, and anthraquinone dyes. The addition amount of these thermal polymerization inhibitors and coloring agents is 0.01% of the total weight of the compound having an ethylenically unsaturated double bond and the binder.
% to 3%, colorant 0.001% to 10% is preferred. Examples of plasticizers include dioctyl phthalate, didodecyl phthalate, dibutyl phthalate, butylbenzyl phthalate, triethylene glycol dicaprylate, dimethyl glycol phthalate, tricresyl phosphate, dioctyl adipate, dibutyl adipate, dibutyl sebacate, dibutyl maleate, Triacetylglycerin and the like can be added in an amount of 5% or less based on the total weight of the compound having an ethylenically unsaturated double bond group and the binder. The photopolymerizable composition of the present invention can be used to form a photosensitive material in the absence of a solvent, or can be dissolved in a suitable solvent to form a solution, which is coated on a support and dried to prepare a photosensitive material. Examples of solvents include methyl ethyl ketone, acetone, cyclohexanone, ethyl acetate,
Butyl acetate, amyl acetate, ethyl propionate,
Examples include toluene, xylene, benzene, monochlorobenzene, chloroform, carbon tetrachloride, trichloroethylene, trichloroethane, dimethylformamide, methyl cellosolve, ethyl cellosolve, tetrahydrofuran, pentoxone, methanol, ethanol, propanol, and the like. Examples of the support used when preparing a photosensitive material using the photopolymerizable composition of the present invention include metals such as aluminum, magnesium, copper, zinc, chromium, nickel, and iron, or alloys containing these as main components. sheets, high-quality paper, art paper, paper such as release paper, glass, inorganic sheets such as ceramics,
Polyethylene terephthalate, polyethylene, polymethyl methacrylate, vinyl chloride, vinyl chloride-vinylidene chloride copolymer, polystyrene, 6
- Polymer sheets such as nylon, 6,6-nylon, cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, etc. These supports may be applied to both sides of the photosensitive layer, and may be surface-treated to adjust the adhesive strength. In addition, the photopolymerizable composition of the present invention can be further processed using known techniques to prevent negative effects such as decreased sensitivity and storage stability due to oxygen, such as providing a removable transparent cover sheet on the photosensitive layer or providing oxygen permeability. It is also possible to provide a coating layer made of a waxy substance having a small amount of water, a water-soluble or alkali water-soluble polymer, or the like. Exposure light sources that can be applied to the composition of the present invention include carbon arc, high pressure mercury lamp, xenon lamp,
180nm metal halide lamp, fluorescent lamp, tungsten lamp, argon ion laser, helium cadmium laser, krypton laser, etc.
General-purpose light sources including the above-mentioned ultraviolet rays and visible rays can be suitably used. The photopolymerizable composition of the present invention is useful in a wide range of application fields, such as the production of printing plates for planography, intaglio, letterpress, and laser engraving, photoresists for production of printed wiring and ICs, relief images, etc. It can be used for image formation such as image duplication, photocurable ink, paint, adhesive, etc., and is particularly effective in application fields that use a visible light source. EXAMPLES The present invention will be specifically explained below using Examples and Comparative Examples, but the present invention is not limited to these Examples. The components of the photopolymerization initiation system are indicated by the following abbreviations. In the formula, Me represents a methyl group and Et represents an ethyl group. Examples 1 to 9, Comparative Examples 1 to 6 2.9 g of methyl methacrylate/methacrylic acid copolymer (binder) obtained by partially hydrolyzing 8 mol% polymethyl methacrylate BR-83 (manufactured by Mitsubishi Rayon Co., Ltd.) using a conventional method. and pentaerythritol triacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.)
A photosensitive solution stock solution was prepared by dissolving 6.8 g of p-methoxyphenol and 18 mg of p-methoxyphenol in 80 g of methyl ethyl ketone. To this photosensitive liquid stock solution, 0.25 g of each component of the photopolymerization initiation system shown in the table was added, and if there was any insoluble matter at room temperature, this was removed by decantation. The resulting photosensitive solution was applied to a grained and anodized aluminum sheet using a whirler to give a dry film thickness of 20 mg/dm ²
It was coated so that the coating was applied and then dried at 60°C for 3 minutes. This surface is further coated with polyvinyl alcohol GL-
A sample was prepared by applying a 6% by weight aqueous solution of 05 (manufactured by Nippon Gosei Co., Ltd.) using a whirler to a dry film thickness of 20 mg/dm ² . A step tablet (manufactured by Eastman Kodak Co., Ltd.) was placed on the obtained sample, and a 490 mm beam was obtained from a xenon lamp light source through both an interference filter KL-49 and a sharp cut filter Y-47 (both manufactured by Toshiba Glass Co., Ltd.). Light beams of different wavelengths (light intensity 2 mw/cm ² ) were irradiated for 60 seconds.
Next, the unexposed areas were dissolved and removed using an aqueous solution containing 9% by weight of butyl cellosolve and 1% by weight of sodium silicate, and the sensitivity was measured by the number of stages of the resulting photocured image. The results are shown in Table 2.

[Table] Examples 10 to 19, Comparative Examples 7 to 12 Evaluations were made according to the method of Example 1 except that a light beam with a wavelength of 436 nm was used as the exposure condition. The results are shown in Table 3.

【table】

[Table] Examples 20, 21, Comparative Examples 13, 14 Evaluation was carried out according to the method of Example 1, except that the exposure condition was to use a light beam with a wavelength of 600 nm and the exposure time was doubled. The results are shown in Table 4.

[Table] Examples 22 to 25, Comparative Examples 15 to 18 Evaluation was performed according to the method of Example 1, except that the exposure condition was irradiation with a 3KW high-pressure mercury lamp for 10 seconds at a distance of 1 m. The results are shown in Table 4.

[Table] Examples 26 and 27, Comparative Examples 19 and 20 A photosensitive liquid stock solution was prepared by dissolving 9.7 g of diallyl phthalate prepolymer Dap K type (manufactured by Osaka Soda Co., Ltd.) and 18 mg of p-methoxyphenol in 80 g of methyl ethyl ketone. To this photosensitive solution stock solution, 0.25 g of each component of the photopolymerization initiation system shown in Table 5 was added, and if there was any insoluble matter at room temperature, this was removed by decantation. The resulting photosensitive solution was applied onto a grained and anodized aluminum sheet using a whirler to give a dry film thickness of 20 mg/dm ² .
℃ for 3 minutes. A step tablet (manufactured by Eastman Kodak Co., Ltd.) was placed on the obtained sample,
The baking frame was evacuated and exposed for 8 minutes using a 3KW high-pressure mercury lamp as the light source. Then benzyl alcohol
35g, tetrahydrofurfuryl alcohol 20g,
Sensitivity was measured by the number of steps in the photocured image obtained by dissolving and removing the unexposed areas with a liquid consisting of 4 g of 85% phosphoric acid, 2 g of glycerin, and 28 g of water. The results are shown in Table 5.

【table】

Claims (1)

[Scope of Claims] 1. A photopolymerizable composition comprising an addition polymerizable compound having at least one ethylenically unsaturated double bond and a photopolymerization initiation system, wherein the photopolymerization initiation system has (a) the general formula [In the formula, R ¹ and R ² represent an alkyl group, Ring A and Ring B represent a benzene ring or a naphthalene ring which may have a substituent, X ^- represents an anion, and n is 0 or 1 is shown. ], and (b) general formula [In the formula, R ³ , R ⁴ and R ⁵ are an alkyl group or an aryl group which may have a substituent, or
Alkenyl group, piperidino group, -NR ₂ , -OR, -
SR (Here, R represents a hydrogen atom or an alkyl group.)
, at least one of which represents a mono-, di- or trihalogen-substituted methyl group. A photopolymerizable composition comprising an s-triazine derivative represented by the following.