JPH0651737B2 - Photosensitive composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a photosensitive composition having high sensitivity and excellent thermal stability.

(Prior Art) There are various types of photosensitive compositions that can be used for letterpress printing plates, squirrel films, photoresists for printed wiring boards, etc. Among them, ethylenically unsaturated compounds that can be polymerized by light irradiation. A composition containing a monomer as a main component is preferably used. In addition to the above ethylenically unsaturated monomer, such a composition usually contains a radical generator and a photoinitiator for causing a polymerization reaction of the monomer. For example, JP-B-45-37377 discloses a photosensitive composition (photographic image forming composition) using a hexaarylbiimidazole compound as a public initiator. 2.2'-Bis (o-chlorophenyl) -4 in which a chloro group is substituted at the ortho position of the phenyl group at the 2-position among these compounds
・ 4 ′ ・ 5.5 ′ ′-tetrakisphenylbiimidazole [2- (2-chlorophenyl) -4,5-diphenylimidazolyl dimer; Cl-HABI] is preferable because it has excellent thermal stability. Has been done.

However, none of the above compounds can be said to have high sensitivity because of their low absorptivity of light in the wavelength range of 300 to 400 nm used for ordinary exposure. When the above-mentioned photosensitive composition is used for a lith film, a large amount of carbon black or a pigment is usually added to the lith film, which causes a problem that light is blocked during exposure and the monomer is not sufficiently polymerized. is there. Furthermore, all of the above photoinitiators, especially Cl-HABI
Has the drawback of being highly bioaccumulative. Chemicals that spill into the water system can enter the body of aquatic organisms and be concentrated, eventually migrating through the food chain to the human body. Therefore, the Ministry of International Trade and Industry requires new chemical substances under the Chemical Substances Examination and Regulation Act to be concentrated and biotested in fish bodies. None of the above photoinitiators can be practically used because it greatly exceeds this regulation standard.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned conventional drawbacks, and an object of the present invention is to provide a photoinitiator with high sensitivity, excellent thermal stability, and low bioaccumulation. An object of the present invention is to provide a photosensitive composition containing an agent and having excellent resolution.

(Means and Actions for Solving Problems) The photosensitive composition of the present invention contains a photoinitiator, a radical generator and an ethylenically unsaturated monomer, and the photoinitiator is represented by the following formula (I). It is the indicated 2,4,5-trially-Ruimidazolyl dimer, which achieves the above objectives.

(Where X is a halogen group, a cyano group, or a carbon number of 1 to
4 alkyl group or aryl group; Y _{1 to} Y ₄ each represent an alkoxyl group having 1 to 4 carbon atoms; Z _{1 to} Z ₁₀ each represent hydrogen or an alkoxyl group having 1 to 4 carbon atoms. However, Y _{1 to} Y ₄ and Z _{1 to} Z ₁₀ do not have to be the same substituents. ) The photoinitiator contained in the photosensitive composition of the present invention is a 2,4,5-trially-imidazolyl dimer having the above chemical structure (I). Such photoinitiators include, for example:
2- (2-chlorophenyl) -4.5-bis (3.5-
Dimethoxyphenyl) imidazolyl dimer, 2- (2-
Chlorphenyl) -4- (3,5-dimethoxyphenyl) -5- (3,4,5-trimethoxyphenyl) imidazolyl dimer, 2- (2-chlorophenyl) -4.5
-Bis (3,4,5-trimethoxyphenyl) imidazolyl dimer, 2- (2-chlorophenyl) -4- (2.
3,5-trimethoxyphenyl) -5- (3,4,5-
Trimethoxyphenyl) imidazolyl dimer, 2- (2
-Chlorophenyl) -4,5-bis (3,4,5-trimethoxyphenyl) imidazolyl dimer, 2- (2-Chloro-5-methoxyphenyl) -4,5-bis (3.5)
There is a -dimethoxyphenyl) imidazolyl dimer. In addition, instead of the chloro group (as X in the above structural formula)
Other halogen groups such as bromine group, fluoro group and iodo group; cyano group; alkyl groups such as methyl group, ethyl group, propyl group, butyl group; compounds substituted with aryl groups such as phenyl group and methoxy group instead of methoxy group (In the above structural formula
Y _{1 to} Y ₄ , Z _{1 to} Z ₁₀ ) ethoxy group, propoxy group,
A compound in which another alkoxyl group such as a butoxy group is substituted is also included. These compounds are characterized in that Y _{1 to} Y ₄ are alkoxyl groups. Since the alkoxyl group is substituted at this position, the light absorption in the region of 300 to 400 nm is high. That is, the sensitivity of the photoinitiator increases, and as a result, the sensitivity of the photosensitive composition also increases. Therefore, even if it is used as a lith film containing a large amount of carbon black, sufficient sensitivity can be obtained.

The photoinitiator is added to the photosensitive composition (excluding the solvent; hereinafter, when the content is shown, the value excluding the solvent is used as a reference).
It is contained in a proportion of 0.3 to 15.0% by weight. If the amount is too small, the radical reaction due to light irradiation does not sufficiently occur, and the polymerization reaction of the monomers described below becomes insufficient and the sensitivity deteriorates. Even if it is excessive, no further effect can be obtained.

The radical generator contained in the composition of the present invention includes:
The radical generator used in a usual radical reaction can be used. Such compounds include amines, leuco dyes, halogenated hydrocarbons, thiourea acids, indole derivatives, benzyl derivatives, and the like, for example, N-phenylglycine, Michler's ketone, Michler's thioketone,
Dimedone, indoleacetic acid, N-naphthylglycine, S
-N-butylthioglycolic acid, 4.4'-bis (dimethylamino) benzyl, p-dialkylaminobenzoic acid ester, leuco crystal violet, indoxylic acid, 1-chloroindoxylic acid, 2-chloroindoxylic acid, 4,4'-bis (diethylamino) benzyl, p-
Methyl diethylaminobenzoate, tri (p-diethylamino-o-tolyl) methane, tri (p-dimethylamino-o-tolyl) methane, 5-chloroindoleacetic acid and the like can be mentioned. Of these compounds, particularly preferred in combination with the photoinitiator used in the present invention are dimedone, indoleacetic acid, N-naphthylglycine, Sn
-Butylthioglycolic acid, 4,4'-bis (dimethylamino) benzyl, p-dialkylaminobenzoic acid ester, leuco crystal violet, indoxylic acid and derivatives of these compounds.

The radical generator is a hydrogen donating or electron donating compound, and when used in combination with a photoinitiator, it generates a radical capable of initiating a polymerization reaction. That is, the photoinitiator decomposes by absorbing light to generate a specific radical. The radical itself generated from this photoinitiator does not have a polymerization initiation function. However, when the above "radical generator" (which functions as a hydrogen donor or an electron donor) is present here, the photodecomposed photoinitiator abstracts hydrogen or an electron from the radical generator, and as a result, a radical is generated. The generator changes into a radical having a polymerization initiation function to initiate polymerization of the monomer.

The radical generator is contained in the composition in a proportion of 0.3 to 15.0% by weight. If the amount is too small, the radical reaction due to light irradiation does not sufficiently occur, and the polymerization reaction of the monomers described below becomes insufficient and the sensitivity deteriorates. Even if it is excessive, no further effect can be obtained.

The ethylenically unsaturated monomer is a compound having an unsaturated group and capable of forming a polymer by addition polymerization by a radical reaction initiated by a radical generator. As such a compound, a derivative of acrylic acid or methacrylic acid [(meth) acrylic acid derivative] is preferably used. Examples of such compounds include alkyl (meth) acrylates such as cyclohexyl acrylate, decyl acrylate, and lauryl acrylate; hydroxyalkyl (meth) acrylates such as 2-hydroxytyl acrylate; amino such as N · N-dimethylaminoethyl acrylate. Alkyl (meth) acrylates; ether alkyl (meth) acrylates such as 2-methoxyethyl acrylate; glycidyl acrylates; halogenated alkyl acrylates; trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, triethylene glycol dimethacrylate, etc. And polyfunctional (meth) acrylates.

In addition to the above compounds, a polymer having an ethylenically unsaturated group in its side chain, for example, the following thermoplastic resins can also be used as the ethylenically unsaturated monomer.

Such an ethylenically unsaturated monomer is contained in the composition at 25-80
It is contained in a weight percentage. If the amount is too small, the membrane performance will deteriorate. If it is excessive, the amount of other additives will decrease,
Sensitivity and film performance are reduced.

The photosensitive composition optionally contains a thermoplastic binder. As the thermoplastic binder, a thermoplastic resin soluble in acid, alkali, or organic solvent is used. As such a thermoplastic binder, polyamide, polyacrylic acid ester, acrylic acid-acrylic acid alkyl ester copolymer, methacrylic acid-methacrylic acid alkyl ester copolymer, polyvinylphenol, polyvinyl ester, polyacrylamide, polyvinyl alcohol , Polyethylene oxide, gelatin, cellulose ester,
Cellulose ether or the like is used.

When the composition is exposed to light and the ethylenically unsaturated monomer undergoes a polymerization reaction, such a thermoplastic binder is incorporated between the molecules of the resulting polymer to form a matrix together with the polymer. As a result, the exposed portion as a whole becomes insoluble in the developer made of acid, alkali or organic solvent. A thermoplastic binder having a polymerizable group in its side chain (for example, polyvinylphenol) may participate in a polymerization reaction together with an ethylenically unsaturated monomer to form a polymer. Among the above thermoplastic binders, polymers containing a carboxyl group, a hydroxyphenyl group, a sulfonic acid group, and a nitrogen atom that can be quaternized with an acid are preferably used.
A polymer having a carboxyl group, a hydroxyphenyl group, and a sulfonic acid group is soluble in an aqueous alkaline solvent, and a polymer containing a nitrogen atom that can be quaternized with an acid is soluble in an aqueous acid solvent. Therefore, it is easy to develop using these solvents and stop the development by washing with water. For example, a polymer having a carboxyl group may be (meth) acrylic polymer, a polymer having a hydroxyphenyl group may be polyvinylphenol, a polymer having a sulfonic acid group may be polystyrenesulfonic acid, and a quaternized acid. Polymers containing nitrogen atoms include polyacrylamide.

The thermoplastic binder is contained in the composition in a proportion of 60.0% by weight or less. If it is excessive, the amount of ethylenically unsaturated monomer becomes too small, and the polymerization reaction by exposure becomes insufficient, resulting in poor resolution.

The composition of the present invention further comprises, if necessary, a sensitizer,
Actinic ray absorber, energy transfer dye, oxygen scavenger,
Additives such as chain transfer accelerators and thermal polymerization inhibitors are included. Among the above additives, as a sensitizer, a hydroxyphthalein dye such as fluorescein or eosin; 3.6
-Aminoacridine dyes such as bis (alkylamino) acridines; Carbocyane dyes such as 3.3'-diethyloxacarbocyanine iodide; 7-dimethylamino-4-methylcoumarin, 7-diethylamino-4-
Coumarins such as methylcoumarin; p-aminophenyl ketones; furans; oxazoles; oxadiazoles; aromatic hydrocarbons; perylenes; pyrenes; bis (p-aminophenyl) -α, β-unsaturation Active light absorbers such as ketones include carbon black,
Titanium oxide, metal or metal oxide powder, pigment, dye, etc. are used.

The above additives are contained in the composition in a proportion of 3% by weight or less. However, when used in applications such as UV-curable paints that use multiple pigments, photoresist inks, and non-silver-based lith films, the total amount of additives is 5%.
It may be contained in a proportion of up to 75% by weight.

The composition containing the above-mentioned photoinitiator, radical generator, ethylenically unsaturated monomer, and, if necessary, thermoplastic binder, various additives, etc., is used for letterpress, lithographic printing plate, non-silver lith film. It can be used as a printing-related material such as a color proof plate, or as an electronic-related material such as a photoresist or a solder mask. The composition may be used in a liquid form or in a solid form such as a film form depending on the purpose.

For example, in order to prepare a lith film using the photosensitive composition of the present invention, a suitable solvent is added to the above composition containing carbon black in an amount of 5 to 75% by weight to dilute the composition. Apply evenly on a transparent plastic sheet using a coater and dry. The thickness after drying is 10 μm or less, preferably 1 to 5 μm. A desired original image (pattern mask) is overlaid on the photosensitive layer of the lith film thus obtained and exposure is performed. When this is developed with, for example, an aqueous acid solvent or an aqueous alkaline solvent,
The unexposed portion is dissolved and removed, and the exposed portion remains insoluble. As a result, relief with fine irregularities is obtained. Since carbon black is blended in the insoluble part, a black film is obtained in the exposed part and a transparent film is obtained in the unexposed part.

In this way, a highly sensitive photosensitive composition can be obtained by using a photoinitiator having a specific structure. The photoinitiator used in the composition of the present invention, unlike conventional photoinitiators, is also soluble in non-halogenated solvents such as alcoholic solvents. Therefore, it is not necessary to use a halogen-based solvent such as chloroform or dichloromethane as the coating dope solvent.
Therefore, there is no risk that the coating device such as a coater will be corroded by the halogen-based solvent, and there is no risk of inhaling the halogen-based solvent that is suspected of being carcinogenic during work. Photoinitiators are bioaccumulative (bioaccumulative)
Since it is extremely small, it is safe for living organisms. Furthermore, because of its excellent thermal stability, even if the photosensitive composition is stored for a long time, for example, at room temperature for one year or more, there is almost no change in the resolution of the composition.

Experimental Examples and Examples Experimental examples showing various properties of the photoinitiator used in the composition of the present invention and Examples of the composition of the present invention are shown below.

Experimental Example 1 The solubility of the photoinitiator used in the present invention and the conventional photoinitiator in organic solvents (methanol, ethyl acetate, chloroform) was examined (Experimental Examples 1-1 to 1-5 and Comparative Experimental Example 1). -1-1-2). The results are shown in Table 1.

It is clear from Table 1 that all of the photoinitiators used in the present invention have relatively good solubility in solvents other than halogen-based solvents such as alcohol-based solvents and acetic acid ester-based solvents.

Experimental Example 2-1 2- (2-chlorophenyl) -4.5 as photoinitiator
0.0080 g of bis (3,4,5-trimethoxyphenyl) imidazolyl dimer and dimedone as a radical generator
0.0030 g, 0.032 g of trimethylolpropane triacrylate as an ethylenically unsaturated monomer, 0.10 g of methyl methacrylate-methacrylic acid copolymer (molar ratio 70:30) as a thermoplastic binder, and methylene chloride as a solvent.
A composition containing a methanol mixture (weight ratio 3: 1) at a ratio of 10.00 g was stored at 40 ° C. in the dark for 2 days. The residual rate of the photoinitiator after storage was measured. The results are shown in Table 2.
Experimental Examples 2-1 to 2-3 and Comparative Experimental Examples 2-1 to 2-6
The results are also shown in Table 2.

Experimental Example 2-2 2- (2-chlorophenyl) -4.5- as a photoinitiator
The same procedure as in Experimental Example 2-1 except that the bis (3.5-dimethoxyphenyl) imidazolyl dimer was used.

Experimental Example 2-3 2- (2-chlorophenyl) -4- (3 as photoinitiator
-It is the same as that of Experimental example 2-1 except having used 4,5-trimethoxyphenyl) -5- (3,5-dimethoxyphenyl) imidazolyl dimer.

Comparative Experimental Example 2-1 2- (2-chlorophenyl) -4.5 as photoinitiator
It is the same as that of Experimental example 2-1 except having used the diphenyl imidazolyl dimer.

Comparative Experimental Example 2-2 2- (2-methoxyphenyl) -4.5 as photoinitiator
The same as Example 2-1 except that -bis (3-methoxyphenyl) imidazolyl dimer was used.

Comparative Experimental Example 2-3 2- (2-Chlorophenyl) -4.5- as a photoinitiator
The same as Example 2-1 except that the bis (4-methoxyphenyl) imidazolyl dimer was used.

Comparative Experimental Example 2-4 The same as Experimental Example 2-1 except that 2-naphthyl-4,5-diphenylimidazolyl dimer was used as the photoinitiator.

Comparative Experimental Example 2-5 The same as Experimental Example 2-1 except that 2,4,5-triphenylimidazolyl dimer was used as the photoinitiator.

Comparative Experimental Example 2-6 2- (2-methoxyphenyl) 4.5 as photoinitiator
It is the same as that of Experimental example 2-1 except having used the diphenyl imidazolyl dimer.

From Table 2, it can be seen that the photoinitiator used in the present invention has excellent thermal stability in a solution. A conventional photoinitiator, 2- (2-chlorophenyl) -4,5-diphenylimidazolyl dimer, also has high thermal stability, but this compound is not preferable because it has a high bioaccumulation potential.

Experimental Example 3-1 This partition coefficient was measured in an n-octyl alcohol-water system as a measure of the bioaccumulation potential of the photoinitiator.

About 10 ml of n-octyl alcohol and about 10 ml of water were placed in a separating funnel, and 2- (2-chlorophenyl) -4,5-bis (3,4,5-trimethoxyphenyl) imidazolyl was used as a photoinitiator. The dimer (1.0 g) was added, and the mixture was shaken several times and then allowed to stand. The amounts of the photoinitiator dissolved in n-octyl alcohol and water were measured and the partition coefficients were calculated: Partition coefficient (ρ) = log (O / w) where O is the light dissolved in n-octyl alcohol. Amount of initiator, and W indicates the amount of photoinitiator dissolved in water.

The results are shown in Table 3. The results of Experimental Examples 3-2 to 3-3 and Comparative Experimental Examples 3-1 to 3-2 are also shown in Table 3.

Experimental Example 3-2 2- (2-chlorophenyl) -4.5- as a photoinitiator
It is the same as that of Experimental example 3-1 except having used bis (3, 5- dimethoxyphenyl) imidazolyl dimer.

Experimental Example 3-3 2- (2-chlorophenyl) -4- (3 as photoinitiator
-It is the same as that of Experimental example 3-1 except having used 4,5-trimethoxyphenyl) -5- (3,5-dimethoxyphenyl) imidazolyl dimer.

Comparative Experimental Example 3-1 2- (2-Chlornaphthyl) -4.5-as Photoinitiator
It is the same as that of Experimental example 3-1 except having used the diphenyl imidazolyl dimer.

Comparative Experimental Example 3-2 2- (2-chlorophenyl) -4.5-as a photoinitiator
It is the same as that of Experimental example 3-1 except having used the diphenyl imidazolyl dimer.

The larger the partition coefficient in the n-octyl alcohol-water system, the greater the concentration / accumulation in living organisms. Normally, the partition coefficient is 3
The following are considered safe compounds. From Table 3, the partition coefficients of the photoinitiators used in the present invention are all 3 or less, and are considered to be safe compounds.

Experimental Example 4-1 Photoinitiator 2- (2-Chlorophenyl) -4,5-bis (3,4,5-trimethoxyphenyl) imidazolyl dimer was dissolved in 10 ppm chloroform solution and placed in a quartz cell (thickness).
(1.0 cm) was used to measure the absorbance at 365 nm. The results are shown in Table 4. The results of Experimental Examples 4-2 to 4-3 and Comparative Experimental Examples 4-1 to 4-3 are also shown in Table 4.

Experimental Example 4-2 2- (2-chlorophenyl) -4.5- as a photoinitiator
It is the same as that of Experimental example 4-1 except having used bis (3.5 dimethoxyphenyl) imidazolyl dimer.

Experimental Example 4-3 2- (2-chlorophenyl) -4- (3 as a photoinitiator
-It is the same as that of Experimental example 4-1 except having used 4,5-trimethoxyphenyl) -5- (3,5-dimethoxyphenyl) imidazolyl dimer.

Comparative Experimental Example 4-1 2- (2-chlornaphthyl) -4.5-as a photoinitiator
It is the same as that of Experimental example 4-1 except having used the diphenyl imidazolyl dimer.

Comparative Experimental Example 4-2 The same as Experimental Example 4-1, except that 2- (2-chlorophenyl) 4,5-bis (3-methoxyphenyl) imidazolyl dimer was used as the photoinitiator.

Comparative Experimental Example 4-3 2- (2-chlorophenyl) -4.5- as a photoinitiator
It is the same as that of Experimental example 4-1 except having used the diphenyl imidazolyl dimer.

From Table 4, the photoinitiator of the present invention is usually exposed to light 30
Since the absorbance at 0 to 400 nm is high, it is clear that the sensitivity is good.

Example 1 Methyl methacrylate-methacrylic acid copolymer (molar ratio 7
0:30) 43.4 parts by weight, carbon black (ultraviolet blocking agent) 10.6 parts by weight, trimethylolpropane triacrylate 36.0 parts by weight, 2- (2-chlorophenyl) -4.5
10.0 parts by weight of a mixture of bis (3,4,5-trimethoxyphenyl) imidazolyl dimer (photoinitiator) and dimedone (radical generator) at a molar ratio of 1: 1 and 0.03 part by weight of bideroquinone monomethyl ether. And methanol
317.0 parts by weight were mixed to prepare a photosensitive composition. The composition was applied onto a 100 μm-thick transparent biaxially stretched polyethylene terephthalate film having an undercoat layer using a reverse coater so that the thickness after drying was 4 μm. The optical density of the formed photosensitive layer is 350-40
The average was 2.6 in the 0 nm range. Further on the surface of the photosensitive layer
An aqueous solution of 10% polyvinyl alcohol (saponification degree: 98 to 99 mol%, polymerization degree: 500) was applied and dried to form a protective layer having a thickness of 2 μm.

On the surface of the protective layer of the obtained squirrel film Super high pressure mercury lamps (Oak Seisakusho; Polymer Printer 3000; 140 W) stacked with step tablets (Kodak)
/ M ² ). After washing with water to remove the protective layer, it was immersed in a 2% aqueous sodium carbonate solution at 25 ° C. for 6 seconds, further immersed in water and rubbed with a sponge to develop. In this way, the exposure time was changed variously, and the optimum exposure time for curing the six steps of the step tablet was determined. Separately, the unexposed lith film was immersed in a 2% sodium carbonate aqueous solution at 25 ° C., and the time required for the photosensitive layer to completely dissolve was measured.

Then, the unexposed lith film was kept in the dark at 40 ° C for a predetermined time (1
After storage for one month and two months), an experiment for determining the optimum exposure time and an experiment for measuring the time required for the unexposed photosensitive layer to completely dissolve were carried out.

The results are shown in Table 5. The results of Examples 2 to 5 and Comparative Examples 1 to 4 are also shown in Table 5.

Example 2 2- (2-chlorophenyl) -4.5- as a photoinitiator
The procedure is the same as in Experimental Example 1 except that the bis (3.5-dimethoxyphenyl) imidazolyl dimer is used.

Example 3 2- (2-chlorophenyl) -4- (3 as photoinitiator
-It is the same as that of Experimental example 1 except having used 4,5-trimethoxyphenyl) -5- (3,5-dimethoxyphenyl) imidazolyl dimer.

Comparative Example 1 The same as in Experimental Example 1 except that 2,4,5-triphenylimidazolyl dimer was used as the photoinitiator.

Comparative Example 2 2- (2-methoxyphenyl) 4.5 as photoinitiator
It is the same as that of Experimental example 1 except having used the diphenyl imidazolyl dimer.

Comparative Example 3 2- (2-chlorophenyl) -4.5- as a photoinitiator
It is the same as that of Experimental example 1 except having used the diphenyl imidazolyl dimer.

Comparative Example 4 2- (2-chlorophenyl) -4.5- as a photoinitiator
It is the same as that of Experimental example 1 except having used bis (3-methoxyphenyl) imidazolyl dimer.

From Table 5, it is clear that the photosensitive composition of the present invention has high sensitivity and hardly changes with time.

(Effect of the Invention) In the present invention, as described above, a highly sensitive photoinitiator having a specific structure is used, and as a result, a photosensitive composition having high sensitivity and high resolution can be obtained. The photoinitiator used in the composition of the present invention, unlike conventional photoinitiators, is also soluble in non-halogenated solvents such as alcoholic solvents. Therefore, it is not necessary to use a halogen-based solvent such as chloroform or dichloromethane as the coating dope solvent. Therefore, there is no risk that the coating device such as a coater will be corroded by the halogen-based solvent, and there is no risk of inhaling the halogen-based solvent that is suspected of being carcinogenic during work. Since the photoinitiator has a minimal bioaccumulation (bioconcentration), it is safe for living organisms. further,
Since it has excellent thermal stability, the photosensitive composition can be used for a long time.
For example, even if the composition is stored at room temperature for one year or more, there is almost no change in the resolution of the composition. Such a photosensitive composition can be applied to many technical fields such as a lith film, a plate material for letterpress printing, and a photoresist for a printed wiring board.

Claims (2)

[Claims] 1. A photosensitive composition containing a photoinitiator, a radical generator and an ethylenically unsaturated monomer, wherein the photoinitiator is represented by the following formula (I). Trially-Ruimidazolyl dimer, photosensitive composition: (Where X is a halogen group, a cyano group, or a carbon number of 1 to
4 alkyl group or aryl group; Y _{1 to} Y ₄ each represents an alkoxyl group having 1 to 4 carbon atoms; Z _{1 to} Z ₁₀ each represent hydrogen or an alkoxyl group having 1 to 4 carbon atoms.
However, Y _{1 to} Y ₄ and Z _{1 to} Z ₁₀ may not be the same substituent. ) 2. The radical generator is dimedone, indoleacetic acid, N-naphthylglycine, Sn-butylthioglycolic acid, 4,4′-bis (dimethylamino) benzyl, p-dialkylaminobenzoic acid ester, The photosensitive composition according to claim 1, which is selected from the group consisting of leuco crystal violet, indoxylic acid and derivatives of these compounds.