JPH0876377A - Photopolymeerizable composition - Google Patents

Abstract

PURPOSE: To obtain a photopolymerizable compsn. excellent in practicality such as property of making a visible image by development, aging stability and sensitivity by incorporating a specified sensitizer and a specified activator into a photopolymn. initiating system. CONSTITUTION: In a photopolymerizable compsn. contg. a compd. having at least one addition polymerizable ethylenically unsatd. bond and a photopolymn. initiating system, a sensitizer represented by the formula and at least one kind of activator capable of generating radicals when irradiated with light under coexistence with the sensitizer is incorporated into the photopolymn. initiating system. In the formula, each of R<1> -R<6> is H, halogen, alkyl, aryl, aralkyl, acyl, etc., R<7> is an optionally substd. arom. hydrocarbon group or an optionally substd. arom. heterocyclic group, R<8> is H, alkyl, aryl, aralkyl, an alkali metal atom or quat. ammonium and each of X<1> and X<2> is halogen, alkyl, aryl, aralkyl, an optionally substd. hydrocarbon substituent, etc.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a photopolymerizable composition. In particular, the present invention relates to a photopolymerizable composition which not only exhibits extremely high sensitivity to light in the visible region, but also has excellent stability over time and provides good development visual imageability.

[0002]

2. Description of the Related Art Conventionally, many image forming methods utilizing a photopolymerization system are known. For example, a photopolymerizable composition comprising a compound containing an addition-polymerizable ethylenic double bond, a photopolymerization initiator, and an organic polymer binder optionally used is prepared, and the photopolymerizable composition is supported. A photosensitive material having a layer of the photopolymerizable composition applied on the body is prepared, and the desired image is imagewise exposed to polymerize and cure the exposed portion, and the unexposed portion is dissolved and removed to form a cured relief image. And a layer of the photopolymerizable composition is provided between two supports in which at least one of the above-mentioned photosensitive materials is transparent,
A method of forming an image by peeling the support after imagewise exposing from the transparent support side to induce a change in adhesive strength by light, and other changes in toner adhesion of the photopolymerizable composition layer due to light were used. There are image creation methods. Conventionally, benzoin, benzoin alkyl ether, benzyl ketal, benzophenone, anthraquinone, benzyl, or Michler's ketone has been used as the photopolymerization initiator of the photopolymerizable composition applied to these methods.

However, these photopolymerization initiators are
Compared with the ability to initiate photopolymerization for light in the ultraviolet region below 00 nm, it is significantly lower than that for light in the visible light region above 400 nm, thus limiting the range of application of photopolymerizable compositions containing them. In recent years, with the development of image forming technology, there has been a strong demand for photopolymers having a high sensitivity to light rays in the visible region. For example, it is a light-sensitive material suitable for non-contact type projection exposure plate making, laser plate making by visible light laser, and the like. Among these technologies, especially the 488 of argon ion laser
The plate-making method using a 532 nm beam of a YAG laser or a YAG laser is considered to be one of the most promising techniques in the future.

Several proposals have hitherto been made for photopolymerization compositions containing a photopolymerization initiation system capable of being sensitive to light rays in the visible light region. For example, a system of hexaarylbiimidazole and (p-dialkylaminobenzylidene) ketone (JP-A-47-2528, JP-A-54-155).
292, JP-A-56-166154), a system of ketocoumarin and an activator (JP-A-52-112681,
JP-A-58-15503, JP-A-60-88005), a system of a substituted triazine and a sensitizer (JP-A-54-54).
151024, JP-A-58-29803, JP-A-5-
8-40302), biimidazole, styrene derivative, thiol system (JP-A-59-56403), organic peroxide and dye system (JP-A-59-1402).
03, JP-A-59-189340)
A system of a titanocene compound and a sensitizer (JP-A-63-2211).
No. 10, JP-A-4-26154, JP-A-4-2197.
No. 56). Although they are certainly useful, they were still desired to be improved from a practical point of view.

[0005]

DISCLOSURE OF THE INVENTION The present invention is intended to provide a photopolymerizable composition which is more excellent in practicality such as sensitivity, stability over time, and visible image development.

[0006]

Means for Solving the Problems As a result of intensive investigations by the present inventors, by using a pyrromethene compound having a specific substituent as a sensitizer for a photopolymerization initiation system, a photopolymerization compound having more excellent practicality can be obtained. The present invention has been achieved by finding that it is a polymerizable composition. That is, an object of the present invention is to provide a photopolymerizable composition having more excellent visible sensitivity. Another object of the present invention is to provide a photopolymerizable composition having excellent stability over time. Still another object of the present invention is to provide a photopolymerizable composition which is advantageous in the visibility of development. Another object of the present invention is to provide a photopolymerizable composition suitable for laser plate making, which has various performances in a well-balanced manner.

Therefore, an object of the present invention is to provide a photopolymerizable composition containing a compound having at least one ethylenically unsaturated bond capable of addition polymerization and a photopolymerization initiation system, wherein the photopolymerization initiation system is ( a) a sensitizer represented by the following general formula [I] and

[0008]

Embedded image

(In the formula, R ^{1 to} R ⁶ are each a hydrogen atom,
Halogen atom, alkyl group, aryl group, aralkyl group, acyl group, alkoxycarbonyl group, substituted or unsubstituted hydrocarbon ring group, substituted or unsubstituted heterocyclic group or-
Represents SO ₃ -R ⁸ , wherein R ⁸ is a hydrogen atom, an alkyl group,
Aryl group, aralkyl group, alkali metal atom or 4
Represents a primary ammonium group. R ⁷ represents a substituted or unsubstituted hydrocarbon aromatic ring group or a substituted or unsubstituted heteroaromatic ring group, and X ¹ and X ² are each a halogen atom, an alkyl group, an aryl group, an aralkyl group, a substituted or unsubstituted It represents a hydrocarbon ring group or a substituted or unsubstituted heterocyclic group. (B) A photopolymerizable composition characterized by containing at least one activator capable of generating radicals upon irradiation with light in the coexistence with the sensitizer.

The present invention will be described in detail below. A compound capable of addition polymerization having at least one ethylenically unsaturated double bond contained as the first essential component in the photopolymerizable composition of the present invention (hereinafter referred to as “ethylenic compound”).
Abbreviated) means that when the photopolymerizable composition is exposed to actinic rays, it undergoes addition polymerization by the action of the photopolymerization initiation system, which is the second essential component, and cures, resulting in an ethylenically unsaturated double bond. And a polymer having an ethylenically unsaturated double bond in the side chain or the main chain. Incidentally, the meaning of the monomer in the present invention is a concept facing a so-called polymer substance, and therefore includes not only a narrowly defined monomer but also a dimer, a trimer and an oligomer. is there.

Examples of the monomer having an ethylenically unsaturated bond include unsaturated carboxylic acid, ester of aliphatic polyhydroxy compound and unsaturated carboxylic acid; ester of aromatic polyhydroxy compound and unsaturated carboxylic acid; Examples thereof include esters obtained by an esterification reaction of a saturated carboxylic acid with a polyvalent carboxylic acid and the above-mentioned aliphatic polyhydroxy compound, polyvalent hydroxy compound such as aromatic polyhydroxy compound, and the like.

The ester of the aliphatic polyhydroxy compound and the unsaturated carboxylic acid is not limited, but specific examples thereof include ethylene glycol diacrylate, triethylene glycol diacrylate, trimethylolpropane triacrylate, trimethylolethane triacrylate. Acrylic esters such as pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, glycerol acrylate, etc. Methacrylic acid ester replaced, Itaconic acid ester similarly replaced with itaconate Crotonate is maleic acid ester, and was replaced with crotonic acid ester or maleate was replaced.

Examples of the ester of an aromatic polyhydroxy compound and an unsaturated carboxylic acid 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 polyvalent carboxylic acid or a polyvalent hydroxy compound is not necessarily a single substance, but representative specific examples include acrylic acid, phthalic acid and ethylene glycol. Examples thereof include condensates, condensates of acrylic acid, maleic acid and diethylene glycol, condensates of methacrylic acid, terephthalic acid and pentaerythritol, condensates of acrylic acid, adipic acid, butanediol and glycerin.

Other examples of the ethylenic compound used in the present invention include acrylamides such as ethylenebisacrylamide; allyl esters such as diallyl phthalate;
Vinyl group-containing compounds such as divinyl phthalate are useful. The polymer having an ethylenically unsaturated bond in the main chain described above is, for example, a polyester obtained by a polycondensation reaction of an unsaturated divalent carboxylic acid and a dihydroxy compound,
There are polyamides and the like obtained by polycondensation reaction of unsaturated divalent carboxylic acid and diamine. The polymer having an ethylenically unsaturated bond in the side chain is a condensation polymer of a dicarboxylic acid having an unsaturated bond in the side chain, such as itaconic acid, propylidene succinic acid, ethylidene malonic acid, etc. and a dihydroxy or diamine compound. . Further, a polymer having a functional group having a reactive activity such as a hydroxy group or a methyl halide group in its side chain, for example, polyvinyl alcohol, poly (2-hydroxyethyl methacrylate), polyepichlorohydrin, etc. and acrylic acid, methacrylic acid, crotonic acid, etc. Polymers obtained by the macromolecular reaction with the unsaturated carboxylic acid can also be suitably used.

Of the above-mentioned ethylenic compounds, acrylic acid ester or methacrylic acid ester monomers can be particularly preferably used. Next, the photopolymerization initiation system which is the second essential component of the photopolymerization composition of the present invention will be described. The photopolymerization initiation system of the present invention is composed of a combination of two kinds of components, and the first component thereof has the structure of the pyrromethene complex represented by the above general formula [I] represented as (a) in the present invention. It is a sensitizer.

These sensitizers include, but are not limited to, US Pat. H. Boger
et al, Heteroatom Chemistr
y, Vol. 1, 5, 389 (1990). Regarding the photopolymerizable composition containing the sensitizer, some of the inventors of the present invention have already proposed a highly sensitive photopolymerizable composition (JP-A-5-24133).
No. 8, Japanese Patent Application No. 5-83587, Japanese Patent Application No. 6-192
No. 40). As a result of further diligent studies on the photopolymerizable composition, the present inventors have selected a group of sensitizers having a specific substituent, thereby providing stability in addition to sensitivity over time. The inventors have found that a photopolymerizable composition having excellent properties and visible image development and having extremely high practicality can be obtained, and thus reached the present invention.

That is, the sensitizer which characterizes the present invention is one in which R ⁷ in the above formula [I] represents a substituted or unsubstituted hydrocarbon aromatic ring group or heteroaromatic ring group.
The hydrocarbon aromatic ring group is generally mononuclear to trinuclear such as phenyl group, naphthyl group and anthryl group; and the heteroaromatic ring group has nitrogen, oxygen or sulfur atom as a hetero atom. Is mentioned. Of these, a phenyl group is particularly preferable. Examples of the substituent for the hydrocarbon ring group or heterocyclic group include an alkyl group, an alkoxy group, a carboalkoxy group, an acyl group, a cyano group, an amino group, a nitro group and a halogen atom.

Regarding the other substituents in the general formula [I], R ^{1 to} R ⁶ are each a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an aralkyl group, an acyl group, an alkoxycarbonyl group, a substituted or non-substituted one. Substituted hydrocarbon ring group, substituted or unsubstituted heterocyclic group or -SO ₃ -R
Represents ^8, R ⁸ is a hydrogen atom, an alkyl group, an aryl group, an aralkyl group, an alkali metal atom or represents a quaternary ammonium group, X ¹ and X ² are each halogen atom, an alkyl group, an aryl group, an aralkyl group, a substituted Or, represents an unsubstituted hydrocarbon ring group or a substituted or unsubstituted heterocyclic group.

When R ^{1 to} R ⁶ , R ⁸ , X ¹ and X ² represent an alkyl group, it preferably has 1 to 6 carbon atoms, particularly preferably 1 to 3 carbon atoms, and is linear. It may have a side chain. When R ^{1 to} R ⁶ represent an aralkyl group, an acyl group or an alkoxycarbonyl group, or when R ⁸ , X ¹ and X ² represent an aralkyl group, the alkyl part thereof has 1 to 3 carbon atoms, respectively.
Is particularly preferable. R ^{1 to} R ⁶ , X ¹ and X
^{When 2} represents a halogen atom, it is generally preferred to be a bromine atom or a chlorine atom, and when R ⁸ represents an alkali metal atom, it is generally preferred to be a lithium atom, a sodium atom or a potassium atom. R ¹
To R ⁶ , X ¹ and X ² represent a hydrocarbon ring group,
The hydrocarbon ring is preferably mononuclear or dinuclear, and examples of the substituent include an alkyl group, an alkoxy group, a carboalkoxy group, an acyl group, a cyano group, an amino group, a nitro group and a halogen atom. Particularly preferably, it is an alkyl group having 1 to 3 carbon atoms.

Typical examples of the sensitizer represented by the general formula [I] are shown below, but the sensitizer represented by the general formula [I] used in the present invention is not limited to these specific examples. Absent. In the following examples, unless otherwise specified, R ¹ , R ³ , R ⁴ and R ⁶ represent a methyl group,
X ¹ and X ² represent a fluorine atom.

[0021]

Table 1 Compound Examples [I-1] R ² and R ⁵ : ethyl group, R ⁷ : phenyl group [I-2] R ² and R ⁵ : ethyl group, R ⁷ : p-methoxyphenyl group [I- 3] R ² and R ⁵ : ethyl group, R ⁷ : pt
-Butylphenyl group [I-4] R ² and R ⁵ : ethyl group, R ⁷ : m, p
- dimethylphenyl group [I-5] R ² and R ^5: ethyl, R ^7: p-chlorophenyl group [I-6] R ² and R ^5: ethyl, R ^7: p-dimethylaminophenyl group [ I-7] R ² and R ^5: ethyl, R ^7: p-cyanophenyl group [I-8], R ² and R ^5: ethyl, R ^7: 1-naphthyl group [I-9] R ² and R ⁵ : ethyl group, R ⁷ : phenyl group [I-10] R ² and R ⁵ : methyl group, R ⁷ : p-acetophenyl group [I-11] R ² and R ⁵ : methyl group, R ⁷ : 2-furyl group [I-12] R ² and R ⁵ : ethoxycarbonyl group,
R ⁷ : 2-pyridyl group [I-13] R ² and R ⁵ : sulfonylethyl group, R
⁷ : Phenyl group These sensitizers can be prepared according to a conventional method.

In the present invention, at least one of the sensitizers described above is selected and used. The second component constituting the photoinitiating system of the present invention is an activator capable of generating active radicals when irradiated with light in the coexistence with the above-mentioned sensitizer represented by (b) in the present invention. As the activator, any activator can be used as long as it has a property of generating an active radical by causing some action with the photoexcited sensitizer. For example, a titanocene compound,
Hexaarylbiimidazole, halogenated hydrocarbon derivatives, organic thiol compounds, diaryliodonium salts, and organic peroxides can be mentioned.

Of these, a titanocene compound is particularly preferable. The titanocene compound is not particularly limited, but is disclosed in, for example, JP-A-59-152396 and JP-A-6-162.
It can be appropriately selected and used from various titanocene compounds described in JP-A No. 1-151197. More specifically, di-cyclopentadienyl-Ti-di-
Chloride, di-cyclopentadienyl-Ti-bis-
Phenyl, di-cyclopentadienyl-Ti-bis-
2,3,4,5,6-Pentafluorophen-1--1-
Il, di-cyclopentadienyl-Ti-bis-2,
3,5,6-Tetrafluorophenyl-1-yl, di-cyclopentadienyl-Ti-2,4,6-trifluorophen-1-yl, di-cyclopentadienyl-Ti-
Bis-2,6-di-fluorophen-1-yl, di-cyclopentadienyl-Ti-bis-2,4-di-fluorophen-1-yl, di-methylcyclopentadienyl-Ti-bis -2,3,4,5,6-pentafluorophen-1-yl, di-methylcyclopentadienyl-T
i-bis-2,3,5,6-tetrafluorophenyl-1
-Yl, di-methylcyclopentadienyl-Ti-bis-2,6-difluorophen-1-yl, di-cyclopentadienyl-Ti-bis-2,6-difluoro-3-
(Pyr-1-yl) -phen-1-yl (hereinafter, B-1
Represents. ) Etc. can be mentioned.

The suitable amounts of the sensitizer and activator constituting the photopolymerization initiation system used in the photopolymerizable composition of the present invention described above are not particularly limited, but the ethylenic compound 1 is used.
The sensitizer is generally 0.05 to 20 parts by weight with respect to 00 parts by weight.
Parts by weight, preferably 0.2 to 10 parts by weight, the active agent is generally used in a proportion of 0.1 to 100 parts by weight, preferably 0.5 to 50 parts by weight. There is.

In the photopolymerizable composition of the present invention, in addition to the above-mentioned constituents, it is preferable to further add an organic polymer substance as a binder in order to modify the composition and improve the physical properties after photocuring. . The binder may be appropriately selected depending on the improvement purpose such as compatibility, film forming property, developability, and adhesiveness. Specifically, for example, to improve the water-based developability, acrylic acid copolymer, methacrylic acid copolymer, itaconic acid copolymer, partially esterified maleic acid copolymer, acidic cellulose modified product having a carboxyl group in the side chain, Examples include polyethylene oxide and polyvinylpyrrolidone. To improve film strength and adhesion, a polyether of epichlorohydrin and bisphenol A; soluble nylon; alkyl polymethacrylate such as polymethylmethacrylate or alkyl polyacrylate; alkyl methacrylate and acrylonitrile, acrylic acid, methacrylic acid , Copolymers with vinyl chloride, vinylidene chloride, styrene, etc .; copolymers with acrylonitrile and vinyl chloride, vinylidene chloride; vinylidene chloride, chlorinated polyolefins, copolymers with vinyl chloride and vinyl acetate; polyvinyl acetate; Acrylonitrile / styrene copolymer; Acrylonitrile / butadiene / styrene copolymer; Polyvinyl alkyl ether; Polyvinyl alkyl ketone; Polystyrene; Polyamide; Polyurethane; Polyethylene terephthalate isophthalate Mention may be made of acetyl cellulose and polyvinyl butyral. These binders are generally used in a weight ratio of 500% or less, more preferably 20%, with respect to the ethylenic compound.
It can be added and mixed in the range of 0% or less.

The photopolymerizable composition of the present invention may further contain a thermal polymerization inhibitor, a coloring agent, a plasticizer, a surface protective agent, a smoothing agent, if necessary.
Coating aids and other additives can be added. Examples of the thermal polymerization inhibitor include hydroquinone, p-methoxyphenol, pyrogallol, catechol, 2,6-di-
There are t-butyl-p-cresol, β-naphthol, and the like. Examples of the colorant include phthalocyanine pigments, azo pigments, carbon black, pigments such as titanium oxide, ethyl violet, crystal violet, azo dyes, anthraquinone dyes. , There are cyanine dyes. When the binder is used, the thermal polymerization inhibitor and the colorant are added in an amount of 0.01% to 5% of the thermal polymerization inhibitor and 0.1% of the colorant with respect to the total weight of the ethylenic compound and the binder. 1%
It is preferably selected from the range of -40%.

Examples of the plasticizer include dioctyl phthalate, didodecyl phthalate, triethylene glycol dicaprylate, dimethyl glycol phthalate, tricresyl phosphate, dioctyl adipate, dibutyl sebacate, triacetyl glycerin, etc. When used, it is generally added in an amount of 20% or less based on the total weight of the ethylenic compound and the binder.

In addition, a sensitivity improver such as dialkylaminobenzoic acid ester and heterocyclic thiol may be added in an amount of 50% or less based on the total weight of the above. When the photopolymerizable composition of the present invention is used, the photosensitive material is formed without a solvent or dissolved in a suitable solvent to form a solution, which is coated on a support and dried to prepare a photosensitive material. can do. Examples of the solvent include methyl ethyl ketone, cyclohexanone, butyl acetate, amyl acetate, methyl lactate, toluene,
There are xylene, monochlorobenzene, carbon tetrachloride, trichloroethylene, trichloroethane, dimethylformamide, methyl cellosolve, ethyl cellosolve, tetrahydrofuran, bentoxone, propylene glycol methyl ether acetate and the like, and one kind or a combination of two or more kinds can be used.

The support applied when preparing a light-sensitive material using the photopolymerizable composition of the present invention may be any of those usually used. For example, a sheet of metal such as aluminum, magnesium, copper, zinc, chromium, nickel, iron or an alloy containing them as a main component; high-quality paper, art paper,
Papers such as release paper; inorganic sheets such as glass and ceramics; polyethylene terephthalate, polyethylene, polymethylmethacrylate, vinyl chloride, vinyl chloride-vinylidene chloride copolymer, polystyrene, 6-nylon, cellulose triacetate, cellulose acetate butyrate, etc. Polymer sheets, etc.

Further, the photopolymerizable composition of the present invention is further provided with a known technique for preventing adverse effects such as sensitivity decrease and storage stability deterioration due to oxygen, for example, providing a peelable transparent cover sheet on the photosensitive layer. Wax-like substance with low oxygen permeability,
It is also possible to provide a coating layer made of a water-soluble polymer or the like.
The exposure light source applicable to the composition of the present invention is not particularly limited, but carbon arc, high pressure mercury lamp, xenon lamp, metal halide lamp, fluorescent lamp, tungsten lamp, helium cadmium laser, argon ion laser, YAG laser, etc. of 400 nm or more. A general-purpose light source including visible light can be used more suitably.

[0031]

EXAMPLES The present invention will now be described with reference to Examples and Comparative Examples.
More specifically, the present invention does not go beyond the gist thereof.
As long as it is not limited to these examples. What
The sensitizer R-1 used in the comparative examples is represented by the general formula I
By the way, R¹= R³= R^Four= R⁶= Methyl group, R²= R
^Five= Ethyl group, X¹= X²= Fluorine atom, R ⁷= Methyl
Represents a group of compounds.

Examples 1 to 6 and Comparative Example 1 Methyl methacrylate / methacrylic acid copolymer (weight average molecular weight 45,000, polymerization ratio 85/15) (5 g) and trimethylolpropane triacrylate (5 g) were dissolved in 90 g of methyl ethyl ketone. did. To this, 0.2 g of the sensitizer shown in Table-1, 0.2 g of the titanocene compound B-1 and 1 g of ethyl p-dimethylaminobenzoate were added and dissolved to obtain a sample photosensitive solution.

On a grained and anodized aluminum sheet, the above photosensitive solution was applied to a dry film thickness of 2 μm by using a whirler, and a polyvinyl alcohol aqueous solution was applied to the surface thereof so that the dry film thickness became A photosensitive material sample was prepared by coating so as to have a thickness of 3 μm. Then, a xenon lamp manufactured by USHIO INC .; UI-501C was applied to this photosensitive material sample.
Was irradiated for 10 seconds using a spectral sensitivity measurement device manufactured by Narumi Co., Ltd. so that the horizontal axis represents wavelength and the vertical axis logarithmically weakened the light intensity. The exposed sample was developed with an aqueous solution containing 2% by weight of butyl cellosolve and 1% by weight of sodium silicate,
From the heights of the obtained cured images corresponding to the respective wavelengths, the minimum exposure amount required for forming the photocured image was calculated, and the sensitivity of the photosensitive composition at each wavelength was calculated.

The sensitivity is 5 at the initial stage and after 3 months at room temperature.
The value for a 32 nm ray was determined. On the other hand, the evaluation of the visible image development was relatively judged under the room light of a yellow lamp. The results are shown in Table-1. Initial sensitivity values in the table ([]
It is clear from the comparison of the values after 3 months from (inside) that each Example shows stable sensitivity as compared with the Comparative Example, while the visible image development is also improved.

[0035]

[Table 2]

[0036]

The photopolymerizable composition of the present invention has extremely high sensitivity to visible light and is excellent in storage stability with time and visible image development. Therefore, the composition is useful in a wide range of application fields, for example, a photoresist for preparing a printing plate such as a planographic printing plate, an intaglio printing plate, a relief printing plate, a printed wiring and an IC.
It is industrially very useful because it can be used for dry film, image formation such as relief image and image duplication, photocurable ink, paint, adhesive and the like.

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Claims (2)

[Claims] 1. A photopolymerizable composition comprising a compound having at least one ethylenically unsaturated bond capable of addition polymerization and a photopolymerization initiation system, wherein the photopolymerization initiation system is (a).
A sensitizer represented by the following general formula [I] and (In the formula, R ^{1 to} R ⁶ are each a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an aralkyl group, an acyl group, an alkoxycarbonyl group, a substituted or unsubstituted hydrocarbon ring group, a substituted or unsubstituted heterocycle, Group or --SO ₃ --R
Represents ^8, R ⁸ represents a hydrogen atom, an alkyl group, an aryl group, an aralkyl group, an alkali metal atom or a quaternary ammonium group. R ⁷ represents a substituted or unsubstituted hydrocarbon aromatic ring group or a substituted or unsubstituted heteroaromatic ring group, and X ¹ and X ² are each a halogen atom, an alkyl group, an aryl group, an aralkyl group, a substituted or unsubstituted It represents a hydrocarbon ring group or a substituted or unsubstituted heterocyclic group. (B) A photopolymerizable composition containing at least one activator capable of generating a radical upon irradiation with light in the presence of the sensitizer. 2. The photopolymerizable composition according to claim 1, wherein the activator capable of generating radicals is a titanocene compound.