PHOTOPOLYMERIZABLE COMPOSITION

Abstract: Disclosed is a photopolymerizable composition compris­ ing a vinyl monomer and a phototopolymerization initiator. The photopolymerization initiator is a combination of (a) at least one compound selected from a mercaptocarboxylic acid, a polysulfide and a thiosphoric derivative with (b) an α-diketone. The composition may include a storage stabilizer and/or a filler. The composition has an excellent storage sta­ bility under heat and circumstantial light, with no coloration and aging change for the tone and providing products with excellent mechanical performances.

Description: BACKGROUND OF THE INVENTION (1) Field of the Invention This invention relates to a novel photopolymerizable composition. More specifically, it relates to a photopolymerizable composition having excellent storage stability, with less coloration and capable of obtaining cured products having high mechanical performance. (2) Description of the Related Art Photopolymerization has been utilized in a wide variety of applications such as for image formation in fine fabrication processes, for example, for print materials, photosensitive agents for reproduction, printed wirings, IC and shadow masks; as well as for paints, printing inks, adhesives and the like. Polymerization has also been utilized in the dental field, for example, photopolymerizable compositions have been used for the production of a tooth filler (composite resin, etc), tooth sealing material and dental adhesives, as well as for the production of carious tooth preventive fillers, tooth crowns and denture. As the photopolymerizable compositions having been utilized heretofore as described above, Japanese Patent Publication No. 10986/1979, for instance, describes a photopolymerizable composition curable under the irradiation of visible light or ultraviolet light and having a specific composition. The photopolymerizable composition comprises a photoinitiator complex of a photosensitive agent/a reducing agent, that is, a photosensitive catalyst composed of (a) at least one photosensitive agent represented by the following general formula: where X represents C = 0, CR₁'R₂' or CR₃'OR₄' (wherein R₁' through R₄' which may be identical or different represent hydrogen or a hydrocarbon group), ℓ is 0 or 1, the groups A which may be identical or different represent substituted or unsubstituted hydrocarbon groups, in which both of the groups A may be coupled directly or joined together by way of a bivalent hydrocarbon group, or both of the groups A may form together a condensated aromatic ring, and the group A is substituted or unsubstituted aromatic group when ℓ is 1 and X represents CR₁'R₂' or when ℓ is 0, (b) at least one reducing agent represented by the following general formula: where the units R which may be identical or different represent hydrogen, substituted or unsubstituted hydrocarbon groups or two units R may form a ring together with N, provided that three units R are not simultaneously substituted hydrocarbon groups, and N is not directly coupled to the aromatic group, and (c) a polymerizable ethylenically unsaturated material. Specific examples of particularly preferred photosensitive agents can include biacetyl, benzyl, benzophenone, and camphorquinone. As the reducing agent, there can be mentioned trimethylamine, tripropylamine, demethylamine, propylamine, N,N'-dimethylaniline, N-methyldiphenylamine, ethylenediamine, hexamethylenediamine, dimethylaminoethyl methacrylate, piperidine, and the like. Although the materials using these photoinitiators can provide rapid curing under photoirradiation, there have been serious practical problems in that the cured products suffer from remarkable discoloration (mostly yellowing), a significant aging change of the color under sunlight and in water, and exhibit an inferior strength. Further, the composition has an extremely low storage stability under heat and circumstantial light (natural light), which results in a spontaneous curing. SUMMARY OF THE INVENTION The object of this invention is to overcome the foregoing problems in the prior art and provide a photopolymerizable composition having excellent storage stability under heat and circumstantial light, with no discoloration and aging change for the tone and providing products with excellent mechanical performances. In accordance with the present invention, there is provided a photopolymerizable composition comprising a vinyl monomer and a photopolymerization initiator, said vinyl monomer being selected from styrene, acrylonitrile, vinyl acetate, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, methoxyethyl acrylate, methoxyethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, ethylene glycol di-acrylate, ethylene glycol di-methacrylate, diethylene glycol di-acrylate, diethylene glycol di-methacrylate, triethylene glycol di-acrylate, triethylene glycol di-methacrylate, polyethylene glycol di-acrylate, polyethylene glycol di-methacrylate, 1,4-butane-diol di-acrylate, 1,4-butane-diol di-methacrylate, 1,3-butane-diol di-acrylate, 1,3-butane-diol di-methacrylate, 1,6-hexane-diol di-acrylate, 1,6-butane-diol di-methacrylate, glycerin di-acrylate or di-methacrylate of the following general formula: where R₂₅ represents a hydrogen atom or methyl group and p is an integer from 1 to 20, bisphenol A diglycidyl acrylates, bisphenol A diglycidyl methacrylates, urethane di-acrylates, urethane di-methacrylates, trimethylolpropane tri-acrylate, trimethyl-olpropane tri-methacrylate, pentaerythritol tetra-acrylate, penta-erythrytol tetra-methacrylate, bis-phenol A di-acrylate or di-methacrylate represented by the following general formula: where R₂₆ represents a hydrogen atom or methyl group and q is an integer from 1 to 20, wherein said photopolymerization initiator is a combination of (a) at least one compound selected from a mercaptocarboxylic acid, a polysulfide and a thiophosphoric derivative with (b) camphorquinone. DESCRIPTION OF THE PREFERRED EMBODIMENTS The vinyl monomer of this invention may be either a mono-functional vinyl compound or a poly-functional vinyl compound. The mono-functional vinyl compound includes, for example, styrene, acrylonitrile, vinyl acetate, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, methoxyethyl acrylate, methoxyethyl methacrylate, glycidyl acrylate and glycidyl methacrylate Further, the poly-functional vinylic compound includes, for example, ethylene glycol di-acrylate and ethylene glycol di-methacrylate, diethylene glycol di-acrylate and diethylene glycol di-methacrylate, triethylene glycol di-acrylate and triethylene glycol di-methacrylate, polyethylene glycol di-acrylate and polyethylene glycol di-methacrylate, 1,4-butane-diol di-acrylate and 1,4-butane-diol di-methacrylate, 1,3-butane-diol di-acrylate and 1,3-butane-diol di-methacrylate,1,6-hexane-diol di-acrylate and 1,6-butane-diol di-methacrylate, glycerin di-acrylate and glycerin di-methacrylate of the following general formula: where R₂₅ represents a hydrogen atom or methyl group and p is an integer from 1 to 20, as well as bisphenol A diglycidyl acrylates and bisphenol A diglycidyl methacrylates, urethane di-acrylates and urethane di-methacrylates, trimethylolpropane tri-acrylate and trimethylolpropane tri-methacrylate, pentaerythritol tetra-acrylate and pentaerythritol tetra-methacrylate, bisphenol A di-acrylate and bisphenol A di-methacrylate represented by the following general formula: where R₂₆ represents a hydrogen atom or methyl group and q is an integer from 1 to 20. These acrylates and methacrylates may be used alone or in a combination of two or more thereof. The mercaptocarboxylic acid used as the photopolymerization initiator in this invention is preferably a compound represented by the following general formula: where R₁ and R₂ independently represent an alkylene group from 1 to 5 carbon atoms or phenylene group, R₃ represents a nitro group, a hydroxy group, an amino group or a halogen atom. Specifically, they include o-, m- and p-mercaptobenzoic acid, o-, m- and p-mercaptophenyl acetic acid, o-, m- and p-mercaptophenyl propionic acid, o-, m-, and p-mercaptophenyl butyric acid, mercaptobiphenyl carboxylic acid, o-, m- and p-mercaptomethyl benzoic acid, o-nitro-p-mercapto benzoic acid, o-hydroxy-p-mercapto benzoic acid, o-amino-p-mercapto-benzoic acid and o-chloro-p-mercapto-benzoic acid. Particularly, the preferred mercaptocarboxylic acids are o-mercaptobenzoic acid (thiosalycilic acid), m-mercaptobenzoic acid, and p-mercaptobenzoic acid. The polysulfide used as the photopolymerization initiator in this invention is a compound, preferably represented by the following formula: R₄ - S - (S) m - S - R₄ where; m is an integer from 0 to 10; R₄ is a saturated or unsaturated alkyl group having 1 to 20 carbon atoms, a phenyl or a benzyl group, each of which may be unsubstituted or substituted with a carboxylic group at any position. Specific examples can include, for example, dimethyl disulfide, diethyl disulfide, dipropyl disulfide, dibutyl disulfide, diphenyl disulfide, dibenzyl sulfide, trimethylene disulfide, dimethyl trisulfide, diethyl trisulfide, dipropyl trisulfide, dibutyl trisulfide, diphenyl trisulfide, dibenzyl trisulfide, p-(phenyl disulfanil)benzoic acid, and 3,3'-trithiodipropionic acid. Particularly preferred polysulfide can include, for example, diphenyl disulfide, dibenzyl disulfide, di-t-butyl disulfide, trimethylene disulfide, p-(phenyl disulfanil) benzoic acid, diphenyl trisulfide, and dibenzyl trisulfide. It is preferable that the thiophosphoric acid derivative used in this invention be a monothiophosphoric compound represented by the general formula (Where, R₅ represents a hydrogen atom, an alkali metal or an alkyl group containing 1 to 20 carbon atoms and X represents a halogen atom.), a dithiophosphoric diester represented by the general formula: (Where, R₆ is a hydrogen, an alkali metal, a copper atom or a zinc atom and R₇ is an alkyl group containing 1 to 20 carbon atoms.) or a dithiophosphoric triester represented by the general formula (Where, R₈ represents an alkyl group containing 1 to 20 carbon atoms.). Specific examples can include, for example, monothiophosphoric compounds such as trioleyl thiophosphate, tris (2,3-dichloropropyl) thiophosphate, O,O'-diethylthiophosphoryl chloride, O,O'-diisopropylthiolphosphate and sodium diamylmonothiophosphate, dithiophosphoric diesters such as O,O'-diethyldithiophosphate, sodium dipropyldithiophosphate, zinc dipropyldithiophosphate and copper O,O'-di(2-ethylhexyl) dithiophosphate and dithiophosphoric triesters such as O,O'-di-n-butyl-s-ethyldithiophosphate and O,O'-dimethyl-dithio-phosphoryl acetate. Any one of these thiophosphoric derivatives or any combination of at least two of these compounds can be combined with an α-diketone. The photopolymerization initiator is added to the above-mentioned vinyl monomer by an amount from 10⁻⁵% by weight to 30% by weight, preferably, from 10⁻³% by weight to 15% by weight and, particularly preferably, from 10⁻¹% by weight to 5% by weight based on the monomer. The amount of the camphorquinone blended to the above-mentioned vinyl monomer is from 10⁻⁵% by weight to 30% by weight, preferably, from 10⁻³% by weight to 10% by weight and particularly preferably, from 10⁻²% by weight to 3% by weight based on the vinyl monomer. These blending amounts are suitable in that the photopolymerization curing product is free from discoloration and aging change in the color, and further, a composition having a high mechanical strength can be obtained. The storage stabilizer used preferably in this invention is added to significantly reduce the curing of the composition comprising the vinyl monomer and the photopolymerization initiator, under heating and circumstantial light. The storage stabilizer used in this invention can include the following. (A) A triazine compound represented by the general formula: where R₉ , R₁₀ and R₁₁ independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, a hydroxy group, an alkoxy group having 1 to 20 carbon atoms, a phenoxy group, an alkyl peroxy group having 1 to 20 carbon atoms, an amino group represented by NR₁₂R₁₃ in which R₁₂ and R₁₃ independently represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms or aromatic group having 6 to 20 carbon atoms, and derivatives thereof, or a thio group represented by SR₁₄ in which R₁₄ represents a hydrogen atom or a alkyl group having 1 to 20 carbon atoms, for example, 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylanilino)-1,3,5-triazine, 2-(N,N-dibutylamino)-4,6-dimercapto-1,3,5-triazine and 2-anilino-4,6-dimercapto-1,3,5-triazine. (B) A benzotriazole compound represented by the general formula: where R₁₅ represents hydrogen atom or a halogen atom, R₁₆ , R₁₇ , R₁₈ , R₁₉ and R₂₀ independently represent a hydrogen atom, a hydroxy group, an alkyl group having 1 to 10 carbon atoms, or benzyl group and derivatives thereof, for example, 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-(2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl)benzotriazole, 2-(3,5-di-tert-butyl-2-hydroxyphenyl)benzotriazole, 2-(3-tert-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3,5-di-tert-butyl-2-hydroxyphenyl-5-chlorobenzotriazole, or 2-(3,5-di-tert-amyl-2-hydroxyphenyl)benzotriazole. (C) Oxalic acid anilide compounds, for example, 2-ethoxy-2'-ethyloxalic acid anilide, 2-ethoxy-5-tert-butyl-2'-ethyloxalic acid bisanilide. (D) Hindered amine compounds, for example, poly-condensate of dimethyl-1-(2-hydroxyethyl)-4-hydroxy-2,6,6,6-tertramethylpiperidine succinate, (poly((6-(1,1,3,3-tetramethylbutyl)imino-1,3,5-triazine-2,4-di-yl) ((2,2,6,6,-tertramethyl-4-piperidyl)imino)hexamethylene ((2,2,6,6-tetramethyl-4-piperidyl)imino)), 2-(3,5-di-tert-butyl-4-hydroxybenzyl)-2-n-butyl malonic acid bis(1,2,2,6,6-pentamethyl-4-piperidyl). (E) Thiuram sulfide compounds represented by the general formula: where R₂₁ , R₂₂ , R₂₃ and R₂₄ independently represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms and n is an integer from 1 to 4, for example, tetraethylthiuram disulfide, tetramethylthiuram disulfide, or tetrakis(2-ethylhexyl)thiuram disulfide. Among these compounds, particularly preferred in view of the color, storage stability, and mechanical properties of the cured product, are 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylanilino)-1,3,5-triazine, 2-(5-methyl-2-hydroxyphenyl)benzotriazole and tetraethylthiuram disulfide. The above-mentioned storage stabilizer can be used singly or as a combination of two or more, and the amount thereof relative to the above-mentioned vinyl monomer is from 10⁻³% by weight to 10% by weight, preferably, from 10⁻²% by weight to 5% by weight, and particularly preferably, from 5 x 10⁻²% by weight to 1% by weight. In the composition according to this invention, a filler may be further added to the above-mentioned ingredients as required. The filler ingredient can include metals belonging to the groups I, II, III, IV, and V and transition metals of the periodical table, oxides, hydroxides, chlorides, sulfates, sulfite, carbonates, phosphates, silicates, as well as mixtures and complex salts thereof. Particularly preferred are silicone dioxide, quartz powder, aluminum oxide, barium sulfate, titanium oxide, talc, glass powder, glass bead, glass fillers containing barium salt and lead salt, silica gel, colloidal silica, carbon fibers, zirconium oxides, tin oxides and other ceramics powders. The above-mentioned fillers may be non-treated fillers, surface treated fillers with a silane coupling agent or the like, or organic compound fillers compounded with a polymer and then pulverized. The blending amount of the filler may be properly varied depending on the purpose of use for the photopolymerized curing product. For instance, where the filler is used as the filler for dental material, it is blended to the above-mentioned vinyl monomer within a range from 1 to 10³% by weight, preferably, from 10 to 9.5 x 10⁻²% by weight, and particularly preferably, from 20 to 9 x 10²% by weight, into a paste-like composition. Furthermore, the composition according to this invention also may be blended as required with colorants, polymerization inhibitors (for example, hydroquinone, methoxybenzophenone, methylphenol, hydroquinonemonomethyl ether), oxidation stabilizers, UV absorbers (for example, benzophenone), pigments (for example, iron oxide, and titanium oxide), dyes and the like. Since a photopolymerization initiator capable of curing within the range of visible rays is used in the photopolymerizable composition according to this invention, all of the problems in the prior art for UV-photopolymerization, that is, deleterious effect to human bodies, poor curing performance (depth), and expensive installation cost, can be avoided, and further, the cured product obtained through the photocuring has an excellent color stability and a high mechanical performance that could not be obtained in the prior method, and further, the composition according to this invention exhibits an extremely high storage stability. This invention will now be described more specifically by referring to examples, but the invention is not limited to these examples. Examples 1 - 3, Comparative Examples 1 - 2 A monomer mixture comprising: was poured into a Teflon tube (4 mm inner diameter, 20 mm height), sealed at the bottom until the upper surface of the solution was level with the upper surface of the Teflon tube. The Teflon tube was disposed such that the liquid level was situated at a distance of 1 mm from the light irradiation surface of a visible light irradiator (manufactured by 3M Corporation, Trade name: OPTILUX) and visible rays were irradiated for 30 seconds. The poured monomer mixture was recovered from the Teflon tube, removed with a nonpolymerized portion, and the "thickness" was measured for the thus-obtained polymerization curing product. Table 1 shows the kind and amount of the photoinitiator, as well as the result of the measurement of the foregoing "thickness". As apparent from Table 1, the compositions according to this invention have an excellent photocuring performance as compared with the known compositions of the comparative examples. Furthermore, the photocuring polymerizates according to this invention suffered no substantial discoloration, and were remarkably finer as compared with those of the comparative examples. Example 4-6 A monomer mixture comprising: was polymerized and evaluated in the same manner as described in Examples 1 - 3. Table 2 shows the kind and amount of the photoinitiator, as well as the results of the measurement of the foregoing "thickness". Further, the monomer mixture of the same composition as described above was also prepared separately and poured into two vessels made of polypropylene (30 cc volume) each by 5 g. One of the samples was placed in a dark room at 60°C after tightly closing the cover and the other of the samples was placed under circumstantial light at ambient temperature without closing the cover to measure the storage stability until they were spontaneously cured. Table 2 shows the kind and amount of the storage stabilizer, and the results of the measurement of the above-mentioned "thickness" and storage stability. As apparent from Table 2, it can be seen that the composition according to this invention exhibits a good photocuring performance even if the storage stabilizer is added and has an excellent storage stability. Further, the photocuring polymerizate according to this invention was substantially free from discoloration and much finer in appearance. Example 7 - 13 A monomer mixture comprising: was polymerized and evaluated in the same manner as described in Examples 1 - 3. Table 3 shows the kind and amount of the photoinitiator, as well as the results of the measurement of the foregoing "thickness". As apparent from Table 3, the compositions according to this invention have an excellent photocuring performance. Furthermore, the photocuring polymerizates according to this inventiOn did not suffer substantial discoloration, and were remarkably finer. Example 14 - 16 A monomer mixture comprising: was polymerized and evaluated in the same manner as described in Examples 4 - 6. Table 4 shows the kind and amount of the photoinitiator, as well as the results of the measurement for the above-mentioned "thickness" and storage stability. Examples 17 - 26 A monomer mixture comprising: was polymerized and evaluated in the same manner as described in Examples 1 - 3. Table 5 shows the kind and amount of the photoinitiator, as well as the results of the measurement of the foregoing "thickness". As apparent from Table 4, it can be seen that the composition according to this invention exhibits an excellent photocuring performance even if the storage stabilizer is added and has an excellent storage stability. Further, the photocuring polymerizate according to this invention was substantially free from discoloration and extremely fine and uniform in appearance. As apparent from Table 5, the compositions according to this invention have an excellent photocuring performance. Furthermore, the photocuring polymerizates according to this invention suffered no substantial discoloration, and were remarkably fine. Examples 27 - 29 A monomer mixture comprising: was polymerized and evaluated in the same manner as described in Examples 4 - 6. Table 4 shows the kind and amount of the photoinitiator, as well as the results of the measurement of the above-mentioned "thickness" and storage stability. As apparent from Table 6, it can be seen that the composition according to this invention exhibits a good photocuring performance even if the storage stabilizer is added and has an excellent storage stability. 25 Further, the photocuring polymerizate according to this invention was substantially free from discoloration and much finer in the appearance. Examples 30 - 32, Comparative Examples 3 - 4 A monomer filler mixture (paste) comprising: was polymerized and evaluated in the same manner as described in Examples 1 - 3. Table 7 shows the kind and amount of the photoinitiator, as well as the results of the measurement of the foregoing "thickness". As apparent from Table 7, the compositions according to this invention have an excellent photocuring performance also in the case where the filler is added, as compared with the known compositions of the comparative examples. Furthermore, the photocuring polymerizate according to this invention suffered no substantial discoloration, and was remarkably finer as compared with that of the comparative examples. Examples 33 - 35 A monomer-filler mixture (paste) comprising: was polymerized and evaluated in the same manner as described in Example 4 - 6. Table 8 shows the kinds and amount of the photoinitiator, and the result of the measurement of the storage stability and thickness. As apparent from Table 8, it can be seen that the composition according to this invention exhibits an excellent photocuring performance even if the filler is added and has an excellent storage stability. Further, the photocuring polymerizate according to this invention was substantially free from discoloration and extremely fine and uniform in appearance. Example 36 - 42 A monomer-filler mixture (paste) comprising: was polymerized and evaluated in the same manner as described in Examples 1 - 3. Table 9 shows the kind and amount of the photoinitiator, as well as the results of measurement of the foregoing "thickness". As apparent from Table 9, the compositions according to this invention have an excellent photocuring performance also in the case where the filler is added. Furthermore, the photocuring polymerizate according to this invention suffered no substantial discoloration, and were remarkably fine. Examples 43 - 45 A monomer filler mixture (paste) comprising: was polymerized and evaluated in the same manner as described in Example 4 - 6. Table 10 shows the kind and amount of the photoinitiator as well as the results of the measurement of the aforementioned "thickness" and storage stability. As apparent from Table 10, it can be seen that the composition according to this invention exhibits an excellent photocuring performance even if the filler is added and has an excellent storage stability. Further, the photocuring polymerizate according to this invention was substantially free from discoloration and extremely fine and uniform in appearance. Examples 46 - 55 A monomer filler mixture (paste) comprising: was polymerized and evaluated in the same manner as described in Example 1 - 3. Table 11 shows the kind and amount of the photoinitiator, as well as the results of the measurement of the foregoing "thickness". As apparent from Table 11, it can be seen that the composition according to this invention exhibits an excellent photocuring performance even if the filler is added and has an excellent storage stability. Further, the photocuring polymerizate according to this invention was substantially free discoloration and extremely fine and uniform in appearance. Examples 56 - 58 A monomer-filler mixture (paste) comprising: was polymerized and evaluated in the same manner as described in Example 4 - 6. Table 12 shows the kind and amount of the photoinitiator, as well as the results of the measurement of the aforementioned "thickness" and storage stability. As apparent from Table 12, it can be seen that the composition according to this invention exhibits an excellent photocuring performance even if the filler is added and has an excellent storage stability. Further, the photocuring polymerizate according to this invention was substantially free from discoloration and extremely fine and uniform in appearance. Comparative Example 5 After pouring each of the compositions corresponding to Examples 1 to 58 respectively into the above-mentioned Teflon tube, the upper surface of the Teflon tube was covered with an aluminum foil so that visible rays could not reach the poured mixture. Then, the tube was disposed such that the upper surface of the poured mixture was at a distance of 1 mm from the light irradiation surface and visible rays were irradiated for 3 minutes. No polymerization took place. Comparative Example 6 After pouring each of the compositions corresponding to Examples 1 to 58 respectively into the above-mentioned Teflon tube, the upper surface of Teflon tube was covered with an aluminum foil so that visible rays could not reach the poured mixture. Then, the tube was heated for 3 minutes at 60°C. No polymerization took place. Example 59 - 61, comparative Example 7 - 9 A monomer filler mixture (paste) comprising: was irradiated with visible rays for 60 seconds under the same procedures as those in Examples 1 - 3. Then, the thus obtained photopolymerization curing products were cut into cylindrical specimens each 4 x 6 mm, for which measurement was made of the compression strength, color change after an exposure test to sunlight for one week, and color change after one week immersion test in water at 60°C. Table 13 shows the kind and amount of the photoinitiator, as well as the results of the above-mentioned measurement. As apparent from Table 13, the compositions according to this invention have an excellent mechanical strength and extremely high color stability as compared with the known compositions Of the comparative examples. Examples 62 - 70 and comparative Example 10 A monomer-filler mixture (paste) comprising: was polymerized and evaluated in the same manner of Examples 59 - 61. Table 14 shows the kind and amount of the photoinitiator, as well as the results of the above-mentioned measurement. As apparent from Table 14, the compositions according to this invention have an excellent mechanical strength and extremely high color stability, even if the storage stabilizer is added as compared with the known compositions of the comparative example. Examples 72 - 78 A monomer filler mixture (paste) comprising: was polymerized and evaluated in the same manner described in Examples 59 - 61. Table 15 shows the kind and amount of the photoinitiator, as well as the results of the above-mentioned measurement. As apparent from Table 15, the compositions according to this invention have an excellent mechanical strength and extremely high color stability. Examples 79 - 88 and Comparative Example 11 A monomer-filler mixture (paste] comprising: was polymerized and evaluated in the same manner as described in Examples 59 - 61. Table 16 shows the kind and amount of the storage stabilizer and the results of the measurement as described above. As apparent from Table 16, the compositions according to this invention have an excellent mechanical strength and extremely high color stability, even if the storage stabilizer is added as compared with the known compositions of the comparative example. Examples 89 - 98 A monomer filler mixture (paste) comprising: was polymerized and evaluated in the same manner described in Examples 59 - 61. Table 17 shows the kind and amount of the photoinitiator, as well as the results of the above-mentioned measurement. As apparent from Table 17, the compositions according to this invention have an excellent mechanical strength and extremely high color stability. Examples 99 - 108 and Comparative Example 12 A monomer filler mixture (paste) comprising: was polymerized and evaluated in the same manner described in Examples 59 - 61. Table 18 shows the kind and amount of the storage stabilizer, as well as the results of the above-mentioned measurement. As apparent from Table 18, the compositions according to this invention have an excellent mechanical strength and extremely high color stability, even if the storage stabilizer is added as compared with the known compositions of the comparative examples.

Claims: A photopolymerizable composition comprising a vinyl monomer and a photopolymerization initiator, said vinyl monomer being selected from styrene, acrylonitrile, vinyl acetate, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, methoxyethyl acrylate, methoxyethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, ethylene glycol di-acrylate, ethylene glycol di-methacrylate, diethylene glycol di-acrylate, diethylene glycol di-methacrylate, triethylene glycol di-acrylate, triethylene glycol di-methacrylate, polyethylene glycol di-acrylate, polyethylene glycol di-methacrylate, 1,4-butane-diol di-acrylate, 1,4-butane-diol di-methacrylate, 1,3-butane-diol di-acrylate, 1,3-butane-diol di-methacrylate, 1,6-hexane-diol di-acrylate, 1,6-butane-diol di-methacrylate, glycerin di-acrylate or di-methacrylate of the following general formula: where R₂₅ represents a hydrogen atom or methyl group and p is an integer from 1 to 20, bisphenol A diglycidyl acrylates, bisphenol A diglycidyl methacrylates, urethane di-acrylates, urethane di-methacrylates, trimethylolpropane tri-acrylate, trimethyl-olpropane tri-methacrylate, pentaerythritol tetra-acrylate, penta-erythrytol tetra-methacrylate, bis-phenol A di-acrylate or di-methacrylate represented by the following general formula: where R₂₆ represents a hydrogen atom or methyl group and q is an integer from 1 to 20, wherein said photopolymerization initiator is a combination of (a) at least one compound selected from a mercaptocarboxylic acid, a polysulfide and a thiophosphoric derivative with (b) camphorquinone. The photopolymerizable composition according to claim 1, which further comprises a storage stabilizer. The photopolymerizable composition according to claim 1, which further comprises a filler. The photopolymerizable composition according to any of claims 1 to 3 wherein the mercaptocarboxylic acid is a compound represented by the following general formulas (I) or (II): independently an alkylene group having 1 to 5 carbon atoms or a phenylene group and R₃ represents a nitro group, a hydroxy group, an amino group or a halogen atom. The photopolymerizable composition according to any of claims 1 to 3, wherein said polysulfide is a compound represented by the following formula: where: m is an integer of from 0 to 10; R₄ is an unsaturated or saturated alkyl group having 1 to 20 carbon atoms, a phenyl or a benzyl group, each of which may be either unsubstituted or substituted with a carboxylic acid group at any position. The photopolymerizable composition according to any of Claims 1 to 3, wherein said thiophosphoric derivative is selected from the group consisting of: a monothiophosphoric compound represented by the general formula: wherein R₅ represents a hydrogen atom, an alkali metal or an alkyl group having 1 to 20 carbon atoms and X represents a halogen atom, a dithiophosphoric diester represented by the general formula: wherein R₆ represents a hydrogen atom, an alkali metal, a copper atom or a zinc atom and R₇ represents an alkyl group having 1 to 20 carbon atoms, and a thiophosphoric triester represented by the general formula: wherein R₈ represents an alkyl group having 1 to 20 carbon atoms. The photopolymerizable composition according to Claim 2 or 3, wherein the storage stabilizer is at least one compound selected from triazine compounds, benzotriazole compounds, oxalic acid anilide compounds, hindered amine compounds, and thiuram sulfide compounds. The photopolymerizable composition according to Claim 4, wherein the mercaptocarboxylic acid is at least one mercaptobenzoic acid selected from ortho-mercaptobenzoic acid (i.e., thiosalicyclic acid), metha-mercaptobenzoic acid, and para-mercaptobenzoic acid. The photopolymerizable composition according to Claim 5, wherein said polysulfide is diphenyl disulfide, dibenzyl disulfide, di-tert-butyl disulfide, trimethylene disulfide, para-(phenyl disulfanil)benzoic acid, diphenyl trisulfide or dibenzyl trisulfide. The photopolymerizable composition according to Claim 6, wherein the monothiophosphoric compound is trioleyl thiophosphate, tris(2,3-dichloropropyl) thiophosphate, 0,0'-diethylthiophosphoryl chloride, 0,0'-diisopropyl thiophosphate or sodium diamylmonothiophosphate; the dithiophosphoric diester is 0,0'-diethyl dithiophosphate, sodium dipropyldithiophosphate, zinc dipropyldithiophosphate or copper 0,0'-di(2-ethylhexyl)-dithiophosphate; and the dithiophosphoric triester is 0,0'-di-n-butyl-s-ethyldithiophosphate or 0,0'-dimethyl-dithiophosphoryl-acetate. The photopolymerizable composition according to Claim 7, wherein the triazine compounds are represented by the general formula: wherein R₉ , R₁₀ and R₁₁ independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, a hydroxy group, alkoxy group having 1 to 20 carbon atoms, a phenoxy group, an alkyl peroxy group having 1 to 20 carbon atoms, an amino group represented by NR₁₂R₁₃ (in which R₁₂ and R₁₃ independently represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms or an aromatic group having 6 to 20 carbon atoms or derivatives thereof), or a thio group represented by SR₁₄ in which R₁₄ represents hydrogen atom or alkyl group. The photopolymerizable composition according to Claim 11, wherein the triazine compounds are selected from 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylanilino)-1,3,5-triazine, 2-(N,N-dibutylamino)-4,6-dimercapto-1,3,5-triazine, and 2-anilino-4,6-dimercapto-1,3,5-triazine. The photopolymerizable composition according to Claim 7, wherein the benzotriazole compounds are represented by the general formula: wherein R₁₅ represents a hydrogen atom or a halogen atom and R₁₆ , R₁₇ , R₁₈ , R₁₉ and R₂₀ independently represent a hydrogen atom, a hydroxy group, an alkyl group having 1 to 10 carbon atoms, a benzyl group or derivatives thereof. The photopolymerizable composition according to Claim 13, wherein the benzotriazole compound is at least one compound selected from 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-(2-hydroxy-3,5-bis-(α,α-dimethylbenzyl)phenyl) benzotriazole, 2-(3,5-di-tert-butyl-2-hydroxyphenyl)benzotriazole, 2-(3-tert-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3,5-di-tert-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole, and 2-(3,5-di-tert-amyl-2-hydroxyphenyl)benzotriazole. The photopolymerizable composition according to Claim 7, wherein the oxalic acid anilide compound is 2-ethoxy-2'-ethyloxalic acid anilide or 2-ethoxy-5-tert-butyl-2'-ethyloxalic acid bisanilide. The photopolymerizable composition according to Claim 7, wherein the hindered amine compound is a polycondensate of dimethyl-1-(2-hydroxyethyl)-4-hydroxy-2,6,6,6-tetramethylpiperidine succinate, poly(6-(1,1,3,3-tetramethylbutyl)imino-1,3,5-triazine-2,4-di-yl), (2,2,6,6,-tetramethyl-4-piperidyl)imino hexamethylene (2,2,6,6-tetramethyl-4-piperidyl)imino) or 2-(3,5-di-tert-butyl-4-hydroxybenzyl)-2-n-butyl malonic acid bis(1,2,2,6,6-pentamethyl-4-piperidyl). The photopolymerizable composition according to Claim 7, wherein the thiuram sulfide compound is represented by the general formula: R₂₁ , R ₂₂ , R₂₃ and R₂₄ independently represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms and n is an integer from 1 to 4. The photopolymerizable composition according to Claim 17, wherein the thiuram sulfide compound is at least one compound selected from tetraethylthiuram disulfide, tetramethylthiuram disulfide, and tetrakis (2-ethylhexyl)thiuram disulfide.--

Inventors: IGE, HITOSHI, MUKAI, NOBUHIRO, SASAKI, ISAO
Applicants: MITSUBISHI RAYON CO., LTD.
Application year: 1986
Main classification: C08F2
IPC codes: G03F7, C08F2