PHOTOCURABLE COMPOSITION

Abstract: Disclosed are photocurable compositions which comprise (A) a compound having at least one epoxy group and at least one photocurable unsaturated ethylenic double bond within the same molecule; (B) an organometallic compound and (C) a silicon compound capable of generating silanol group by irradiation of light, or comprise (A) a compound having at least one epoxy group and at least one photocurable unsaturated ethylenic double bond within the same molecule; (E) an epoxy compound; (F) an organic phosphorus compound; and (G) a photosensitizer. The compositions of the present invention have excellent film characteristics such as good adhesion property, light resistance, heat resistance and weathering resistance.

Description: This invention relates to a photocurable composition, more particularly to a photocurable composition which has good photocurability and rapid curability as well as excellent coating workability such as flowability, smoothness and uniformity of the coated film, and can also give a cured product having excellent adhesiveness, coating performance, heat resistance and weathering resistance. Photocurable resin compositions, having generally advantages in aspects of conservation of energy, conservation of resources, saving of space and counter-measures against pollution, are now under aggressive researches and developments in various fields such as ink, paint and varnish. Accordingly, demands in aspect of perfomance corresponding to respective fields are also increasing. For example, in photocurable resin compositions to be used for paint, it is desired to improve physical properties of the coated film, particularly adhesiveness, heat resistance and toughness. However, in resin compositions based on acrylic resins, while having an advantage of rapid curing speed, there is involved the drawback of poor adhesiveness. Also, for improvement of coated film performance of said acrylic resins, attempts have been made to solve the problem by formulating heat resistant resins or tough resins to copolymerize said resins with acrylic resins. In any case, while some improvements of respective physical properties may be recognized, the composition will suffer from solidification or thickening to be limited in improvements of respective physical properties. Thus, the problem remains with respect to working characteristics. More specifically, one proposal is a photocurable composition comprising an epoxy resin and an acrylic (methacrylic) resin. The specific feature of the photocuring mechanism in this composition resides in modifying the epoxy resin with acrylic acid, etc. in order to introduce acryloyl groups having photocurability into the epoxy resin and photopolymerizing the vinyl groups introduced. However, the cured product obtained from this composition had the drawback of being lowered in characteristics such as heat resistance and adhesiveness as compared with the epoxy resin itself [see "The Present Situation and Future Development of UV-curable Paint" in Coating & Paint, May (No. 324), p. 45, 1980]. Another known composition is a photocurable composition comprising an epoxy resin and a photocurable catalyst of the type releasing strong acid (see Macromolecules, Vol. 10, p. 1037, 1977). The specific feature of photocuring mechanism in this composition resides in curing the composition by utilizing the photolytic activity of the catalyst represented by the formula: wherein Ar represents a group such as phenyl, X an iodine atom, a sulfur atom or a diazo group and Y BF₄, PF₆, AsF₆ or SbF₆. However, in the cured product obtained from this composition, while having good mechanical characteristics and heat resistance, there are involved the drawbacks such the characteristics of the cured product will be deteriorated by heating or with lapse of time, and also that corrosive phenomenon of the cured product will be brought about, because the catalyst component is a strong acid which will become an ionic impurity. Also, this composition had a great drawback in difficult handleability, and also a drawback of having no adhesive force at all when cured rapidly. An object of the present invention is to provide a photocurable composition, comprising an epoxy compound as the base, which is excellent in coated film characteristics, particularly adhesion property and low in viscosity. Another object of the present invention is to provide a photocurable composition, which is excellent in rapid curing characteristic and can also give a cured product having good coating performance, heat resistance and weathering resistance. Still another object of the present invention is to provide a photocurable composition which is good in curability and also excellent in coating characteristics such as flowability, smoothness and uniformity of coated film. The present inventors have accomplished the present invention by use of a reaction product of a low viscosity epoxy monomer compound which is usually called as diluent with a compound having an unsaturated double bond as the material corresponding to the acrylic resin of the prior art. The photocurable composition of the present invention comprises: (A) a compound having at least one epoxy group and at least one photocurable unsaturated ethylenic double bond within the same molecule; (E) an epoxy compound; (F) an organic phosphorus compound; and (G) a photosensitizer. The compound (A) to be used in the composition of the present invention may be any compound, provided that it has at least one epoxy group and at least one photocurable unsaturated ethylenic double bond, respectively, in the same molecule. Said compound can be obtained by addition of a low viscosity epoxy monomer conventionally called as diluent and a compound having a photocurable unsaturated ethylenic double bond. By this reaction, an unsaturated epoxy compound having a very lower viscosity than the epoxyacrylate type resin of the prior art can be obtained. The epoxy monomer compound to be used in the above addition reaction may be a compound having any viscosity of 200 m Pas or lower, but the viscosity is desirably as low as possible in view of workability. Said epoxy compound may include compounds having groups as represented by the following formulae: Specifically, there may be included those conventionally called as epoxy diluents in the prior art, for example, vinylcyclohexene diepoxide cyclohexene epoxide tert-fatty acid monoglycidyl ether, glycerol glycidyl ether, polyglycol diglycidyl ether, alkylmonoglycidyl ether, alkylphenol monoglycidyl ether, vinyl cyclohexene epoxide glycidyl acrylate glycidyl methacrylate cyclopentadiene diepoxide and the like. On the other hand, the compound having a photocurable unsaturated ethylenic double bond may include the compounds having groups represented by the following formulae: Specifically, there may be included acrylic acid, methacrylic acid, sinnamic acid, maleic acid, fumaric acid, styrene, α-methyl styrene, stilbene, furan, dihydrofuran, pyrrole, imidazole and derivatives of these. Among them, it is preferable to use at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic acid and fumaric acid. In the epoxy compound and the compound having an unsaturated ethylenic double bond, hydrogen atoms bonded to carbon atom may be substituted by halogen atoms such as chlorine and fluorine, alkyl groups such as methyl group, aromatic groups such as phenyl group or other functional groups. The addition reaction of both compounds as described above may be carried out by refluxing these compounds in the presence of a polymerization inhibitor and an alkaline reagent in a solvent. In said reaction, the epoxy compound is formulated in an amount over equal moles, preferably two or more moles per mole of the compound having a double bond. As the solvent, a low polar solvent such as toluene may be used, while quinones such as hydroquinone may be used as the polymerization inhibitor and quaternary ammonium salts, amines, etc. may be used as the alkaline agent. The reaction temperature may be generally 100 to 120 °C, and the reaction time is generally 2.0 to 9.0 hours. After completion of the reaction, the product can be treated in a conventional manner such as extraction or solvent evaporation to give a low viscosity unsaturated epoxy compound. This compound can be constituted by synthesizing as desired according to a molecular design depending on the purpose as described above. However, on the other hand, it is also possible to synthesize readily the compound by allowing acrylic acid, methacrylic acid, sinnamic acid, maleic acid or the like to react with an epoxy resin conventionally used. As the epoxy resin employed in the latter method, there may be included bisphenol A type epoxy resins; bisphenol F type epoxy resins; phenol novolac type epoxy resins; alicylic epoxy resins; heterocyclic ring-containing epoxy resins such as triglycidyl isocyanurate or hydantoin epoxy; hydrogenated bisphenol A type epoxy resins; aliphatic epoxy resins such as propylene glycol-diglycidyl ether, pentaerythritolpolyglycidyl ether; epoxy resins obtained by the reaction of aromatic, aliphatic or alicyclic carboxylic acids with epichlorohydrin; spiro ring-containing epoxy resins; glycidyl ether type epoxy resins which are reaction products of o-allylphenol novolac compounds with epichlorohydrin; and glycidylether type epoxy resins which are reaction products of diallylbisphenol compounds having allyl groups at the o-positions of the respective hydroxyl groups of bisphenol A with epichlorohydrin. At least one selected from these groups can be employed as desired. Specific examples of said compound may include addition compounds in which the proton eliminated group of the above compound having ethylenic double bond is bonded to the epoxy group moiety of the above epoxy compound, more specifically those represented by the following formulae: The epoxy compound (E) to be used in the photocurable composition according to the invention is a component for improving adhesiveness of the component (A). The number of epoxy groups in one molecule of the compound may be any of 1 or more, but preferably a plural number, particularly 2 to 3. Typical examples of the above compound may include epoxy-modified compounds of novolac type phenol resins, specifically o-cresol novolac epoxy resins, m-cresol novolac epoxy resins, p-cresol novolac epoxy resins. Also, as oil soluble novolac epoxy resins belonging to said epoxy-modified compounds, there may be employed p-tert-butylphenol epoxy resins, nonylphenol epoxy resins, etc.; as divalent phenol epoxy resins, resorcin novlac epoxy resins, catechol novolac epoxy resins, hydroxynovolac epoxy resins, etc.; as resins imparted with heat resistance, o-, m- or p-fluoro, bromo or iodo halogenated phenol novolac epoxy resins, etc.; modified novolac epoxy resins such as novolac epoxy resins modified with aniline, melamine, aminobenzene, etc., xylene-modified novolac epoxy resins and unsubstituted phenol novolac epoxy resins. It is also possible to use non-novolac type modified phenol resins represented by the following formulae: These compounds may be used either singly or as a mixture of two or more compounds. The above compound may be formulated in the composition according to the second embodiment in an amount of 1 to 80 % by weight, preferably 15 to 30 % by weight, based on the total amount of the components (A) and (E). The organic phosphorus compound (F) to be used in the photocurable composition according to the invention is a component which improves adhesiveness of the component and also accelerates the curing speed. Specific examples of such compounds may include, for example, phosphates such as 2-methacryloyloxyethylphosphate, 2-acryloyloxyethylphosphate, diphenyl-2-methacryloyloxyethylphosphate, diphenyl-2-acryloyloxyethylphosphate, bis methacryloyloxybutylphosphate, bisacryloyloxybutylphosphate, diallyldibutylphosphonosuccinate, etc.; alkylphosphates such as trimethylphosphate, triethylphosphate, tributylphosphate, etc.; alkoxyphosphates such as trimethoxyphosphate, tributoxyphosphate, etc.; other phosphate such as trisdichloropropylphosphate, triphenylphosphate, tricresylphosphate, etc.; phosphites such as triphenylphosphite, trilauryl·trithiophosphite, dibutenylhydrogenphosphite, etc.; phosphonates such as dibutyl·butylphosphonate, di(2-ethylhexyl)-2-ethylhexylphosphonate, 2-ethylhexylphosphonic acid, etc. These compounds may be used either singly or as a mixture of two or more compounds. The above organic phosphorus compound may be formulated in the composition according to the second embodiment in an amount of 0.01 to 10 parts by weight, preferably 0.1 to 2.0 parts by weight, based on 100 parts by weight of the total amount of the components (A) and (E). If the proportion is less than 0.01 % by weight, no effect can be obtained, while a proportion over 10 % will cause geration of the composition because of the reaction with the epoxy compounds. The photosensitizer (G) to be used in the photocurable composition according to the invention may be any one which can photosensitize the above compound (A), and it can suitably be selected depending on the components to be formulated as well as the light source, etc. Such photosensitizers may include, for example, aromatic hydrocarbons, benzophenone and derivatives thereof, esters of o-benzoylbenzoic acids, acetophenone and derivatives thereof, benzoin and benzoin ethers and derivatives thereof, xanthone and derivatives thereof, thioxanthone and derivatives thereof, disulfide compounds, quinone compounds, halogenated hydrocarbons, amines, etc. Examples of the aromatic hydrocarbon may include benzene, benzene-d₆, toluene, p-xylene, fluorobenzene, chlorobenzene, bromobenzene, iodobenzene, naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, 1-fluoronaphthalene, 1-chloronaphthalene, 2-chloronaphthalene, 1-bromonaphthalene, 2-bromonaphthalene, 1-iodonaphthalene, 2-iodonaphthalene, 1-naphthol, 2-naphthol, biphenyl, fluorene, p-terphenyl, acenaphthene, p-quaterphenyl, triphenylene, phenanthrene, azulene, fluoranthene, chrycene, pyrene, 1,2-benzpyrene, anthracene, 1,2-benzanthracene, 9,10-dichloroanthracene, 9,10-dibromoanthracene, 9,10-diphenylanthracene, perylene, tetracene, pentacene, etc. Examples of the benzophenone and the derivatives thereof may include benzophenone, 2,4-dimethylbenzophenone, 2,4-dichlorobenzophenone, 4,4'-bis(dimethylamino)benzophenone, etc. Examples of the esters o-benzoylbenzoic acids may include methyl o-benzoylbenzoate, ethyl o-benzoylbenzoate, phenyl o-benzoylbenzoate, Examples of the acetophenone and the derivatives thereof may include acetophenone, 4-methylacetophenone, 3-methylacetophenone, 3-methoxyacetophenone, etc. Examples of the benzoin, the benzoin ethers and the derivatives of these may include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-butyl ether, benzoin triphenylsilyl ether, Examples of the xanthone and the derivatives thereof may include xanthone, 2,4-dimethylxanthone, 2,4-dichloroxanthone, etc. Examples of the thioxanthone and the derivatives thereof may include thioxanthone, 2,4-dimethylthioxanthone, 2,4-dichlorothioxane, etc. Examples of the disulfide compounds may include; Examples of the quinone series compounds may include benzoquinone, naphthoquinone, anthraquinone, 5,12-naphthacene dione, 2,7-pyrene dione, etc. Examples of the halogenated hydrocarbons may include carbon tetrachloride, hexachloroethane, carbon tetrabromide, Examples of the amines may include diphenylamine, carbazole, triphenylamine, Examples of the other photosensitizers may include propiophenone, anthrone, benzaldehyde, butylophenone, 2-naphthylphenylketone, 2-naphthaldehyde, 2-acetonaphthone, 1-naphtylphenylketone, 1-acetonaphthone, 1-naphthoaldehyde, fluorenone, 1-phenyl-1,2-propane dione, benzoethrile, acetone, biacetyl, acridine orange, acridine, Rhodamine-B, eosine, fluorescein, In the compositions described above, each of the components (F) and (G) may be used as a single species or two or more species, and incorporated at a proportion generally within the range from 0.01 to 10 % weight based on the resin components (A) and (E). Further, in the photocurable compositions according to the invention, in addition to the above components, colorants, inorganic fillers or other additives may also be incorporated, if desired. The photocurable composition of the present invention can be cured according to any desirable curing method, depending on the purpose and the use, such as normal temperture photocuring, heating photocuring, after-cure which is effected after the photocuring, etc. to be provided for practical use. The wavelength of the light irradiated in such curing may differ depending on the composition of the photocurable composition, but it is generally 180 to 700 nm. Above all, irradiation of UV-ray is effective. The irradiation time may differ depending on the composition of the photocurable resin, the kind of the catalyst and light source, but it is generally 0.1 second to 180 minutes, preferably 1 second to 10 minutes. The heating temperature in the case of heating photocuring may be generally 20 to 200 °C, preferably 60 to 150 °C. As the light source, any one conventionally used for photocuring may be available, including, for example, low pressure mercury lamp, high pressure mercury lamp, carbon arc lamp, metal halide lamp, xenon-mercury lamp, xenon-lamp, hydrogen discharge tube, tungsten lamp, halogen lamp, sodium discharge tube, neon discharge tube, argon discharge tube, He-Ne laser, Ar ion laser, N₂ laser, Cd ion laser, He-Cd laser, dye laser and various electron beams and radioactive rays such as X-ray, and others. One or two or more light sources selected from the group consisting of these may suitably be used. According to the composition of the present invention, its adhesiveness can be improved without impairing the characteristics of the acrylic compound which is the base of said composition. Also, since a low viscosity unsaturated epoxy resin as different from the acrylic resin of the prior art is employed, there is no fear of worsening in workability due to solidification or thickening of the composition. Accordingly, for improvement of various coated film characteristics, other resins can easily be formulated to be copolymerized. Also, the photocurable composition of the present invention has good photocurability to be cured rapidly, and also excellent working characteristics such as flowability, smoothness and uniformity of coated film. Further, the cured product obtained has good light resistance, heat resistance and weathering resistance. Therefore, the composition of the present invention is useful as very excellent photocurable composition in various fields such as ink, paint, adhesive, surface coating material, printing plate material, encapsulating material, electric insulating material, etc., and its industrial value may be appreciated to be great. This invention will be described in greater detail by giving the following Examples. Example 1 Into a four-necked flask equipped with a thermometer, a reflux condenser, a N₂ gas inlet and a stirrer, 300 g of vinylcyclohexene epoxide (trade name: ERL-4206, produced by UCC, alicyclic epoxide, epoxy equivalent: 70), 140 g of acrylic acid, 200 g of toluene, 0.005 g of hydroquinone and 1.5 g of trimethylamine as the catalyst were charged. After replacement with N₂ gas, the mixture was gradually elevated in temperature under stirring and the reaction was carried out under the reflux temperature of toluene. Progress of the reaction was monitored by measuring the amount of consumed acrylic acid with 0.1 N standard NaOH solution, and the reaction was terminated when acid value becames substantially 0. After completion of the reaction, the reaction solution was mixed with 1000 ml of deionized water, washed six times and then the toluene layer was separated by a separating funnel, followed by evaporation of toluene under reduced pressure. By this reaction, an acrylic acid epoxy resin (abbreviated as VHEA) having a viscosity of 2500 m Pas (25 °C) and an epoxy equivalent of about 500 was obtained. Example 2 Into a four-necked flask equipped with a thermometer, a reflux condenser, a N₂ gas inlet and a stirrer, 280 g (2.0 mole) of ERL-4206 (trade name, produced by UCC Co., vinylcyclohexene diepoxide, epoxy equivalent: 70), 72 g (1.0 mole) of acrylic acid (produced by Wako Junyaku Co.), one liter of toluene, 0.01 g of p-methoxyphenol and 1.20 g of tetrabutylammonium chloride as the catalyst were charged, the mixture was gradually elevated in temperature under stirring and the reaction was carried out under the reflux temperature of toluene. Progress of the reaction was monitored by measuring the amount of consumed acrylic acid with 0.1 N standard NaOH solution, and the reaction was terminated when an acid value becames substantially 0. After completion of the reaction, the reaction solution was mixed with one liter of deionized water, washed 3 times and then the toluene layer was separated by a separating funnel, followed by evaporation of toluene under reduced pressure. The compound synthesized was an acrylated epoxy resin (hereinafter abbreviated as VHEA) having a viscosity of 25 poise (25 °C) and an epoxy equivalent of 480. Examples 3 - 9 In addition to VHEA prepared in the above Examples 1 and 2, cresol novolac type epoxy resins EOCN-102S (trade name, melting point: 50 °C or higher, produced by Nihon Kayaku Co.) and ECN-1235 (trade name, melting point: 40 °C or higher, produced by Ciba-Geigy AG.) were employed as the adhesion enhancer, and methacryloyloxyethyl phosphate (hereinafter abbreviated as MAEP) as the adhesiveness imparting agent. Further, as the photosensitizer, D-1173 (acetophenone type sensitizer, produced by Merck Co.) and benzophenone (produced by Kanto Kagaku) were employed to provide essential materials of the invention. Various materials as mentioned above were formulated according to the compositions (represented by parts by weight) shown in Table 1 to prepare compositions belonging to this invention as shown below. Comparative examples 1 - 4 As comparative examples, compositions in which epoxyacrylate (hereinafter abbreviated to as DYEPAC) conventionally used in the art was formulated as the base resin were prepared. Main component Auxiliary Photosensitizer VHEA DYEPAC ECON-102S ECN-1235 MAEP D-1173 Benzophenone Example 3 100 - - - 2 6 - 4 100 - - - 2 - 6 5 80 - 20 - 2 6 - 6 80 - 20 - 2 - 6 7 80 - 20 - 2 4 2 8 80 - - 20 2 6 - 9 80 - - 20 2 - 6 Comparative example 1 - 100 - - 2 6 - 2 - 100 - - 2 - 6 3 - 80 - 20 2 6 - 4 - 80 20 - 2 - 6 These compositions were applied according to conventional methods on aluminum plates, TES (Tin Free steel) plates and tin plates. Then, these were introduced into a photocuring box in which air-cooled mercury lamp of 80 W/cm was arranged 10 cm above the conveyor surface and irradiated for 0.5 to 3.0 seconds. After irradiation, coating thickness, coating hardness (pencil hardness), coating adhesiveness (checker peel-off) and flexural test (180° bending) were tested and the results obtained are shown in Table 2. Coating adhesiveness Pencil hardness Flexural est Film thickness(µ) Aluminum TFS Tin Example 3 60/100 50/100 10/100 HB-H O 5 4 70/100 40/100 20/100 HB-H O 6 5 90/100 90/100 30/100 H O 6 6 100/100 100/100 30/100 H-2H Δ 6 7 100/100 100/100 40/100 2H O 5 8 100/100 100/100 20/100 2H O 7 9 100/100 100/100 30/100 H O 5 Comparative example 1 30/100 10/100 0/100 H X 6 2 30/100 0/100 0/100 HB X 5 3 100/100 50/100 0/100 HB Δ 6 4 100/100 70/100 0/100 HB X 6 Note 1) Curing conditions: Three air-cooling type mercury lamps were used, irradiation time was 1 second, and these lamps were disposed 10 cm above the surface of the conveyor. Note 2) "100/100" means that no peel-off was observed at the peeling test on checkers. Note 3) With regard to the bending test, O represents no occurence of cracks on the coating film, Δ represents the slight occurence of cracks, and X represents the remarkable occurence of cracks. As can clearly be seen from the above description, it has been confirmed that excellent cured films can be obtained according to the composition of the invention.

Claims: A photocurable composition comprising: (A) a compound having at least one epoxy group and at least one photocurable unsaturated ethylenic double bond within the same molecule; (E) an epoxy compound; (F) an organic phosphorus compound; and (G) a photosensitizer. A photocurable composition according to Claim 1, wherein the compound (A) is a reaction product of an epoxy compound having a viscosity of 200 m Pas or less and a compound having a photocurable unsaturated ethylenic double bond. A photocurable composition according to claim 1 or claim 2, wherein the epoxy compound (E) is an epoxy-modified compound of a phenol novolac resin. A photocurable composition according to any preceding claim, wherein the amount of epoxy compound (E) present in the composition is 1 to 80 % by weight based on the total amount of the compound (A) and the epoxy compound (E). A photocurable composition according to any preceding claim, wherein the organic phosphorus compound (F) is a (meth)-acryloyloxyalkyl phosphate compound. A photocurable composition according to any preceding claim, wherein the amount of organic phosphorus compound (F) present in the composition is 0.01 to 10 parts by weight based on 100 parts by weight of the total amount of the compound (A) and the epoxy compound (E). A photocurable composition according to any preceding claim, wherein the amount of photosensitizer (G) present in the composition is 0.01 to 10 parts by weight based on 100 parts by weight of the total amount of the compound (A) and the epoxy compound (E).

Inventors: HAYASE, SHUZI C/O KABUSHIKI KAISHA TOSHIBA, MIKOGAMI, YUKIHIRO C/O KABUSHIKI KAISHA TOSHIBA, SUZUKI, SHUICHI C/O KABUSHIKI KAISHA TOSHIBA, WADA, MIROYASU C/O KABUSHIKI KAISHA TOSHIBA, WADA, YUUSUKE C/O KABUSHIKI KAISHA TOSHIBA
Applicants: KABUSHIKI KAISHA TOSHIBA
Application year: 1985
Main classification: C08G59
IPC codes: C08G65, C08G59, G03F7