The present invention relates to a photosensitive composition, a white coating and a production method thereof. The white coating can be obtained from a colorless, transparent liquid by coating the said photosensitive composition on a substrate and then irradiating ultraviolet light thereon.
No white dye has been known yet until now. For this reason, white inorganic pigments such as titanium oxide have been in use for a white paint. In general, the dye is a coloring agent which colors by being dissolved in a vehicle but it does not matter whether it has dyeability or not. On the other hand, the pigment is fine colored powder which cannot be dissolved in water or solvents and has certain shapes and sizes differently from the dye.
However, since the inorganic pigments (fine powders) such as titanium oxide have necessarily been used for the white paint in the past problems as explained in the following have been pointed out.
Because the white inorganic pigments are dispersed in the liquid of the conventional white paint, the inorganic pigments settle gradually settled by the difference in the specific gravity between the liquid and the pigments, while the paint is left to rest. Especially, this tendency is remarkable in the case of the white paint of low viscosity.
When the pigments settle, the density of the pigments becomes ununiform, so that the quality of the white paint becomes unstable. For this reason, the white paint rust be stirred homogeneously at every use, which requires much time.
In addition, if the white paint is used in the condition of insufficient dispersion of the inorganic pigments by insufficient stirring, the whiteness degree (light and shade) of the letters painted by the said white paint because uneven or the opacifying property at the coated area becomes so ununiform that the substrate color is sometimes seen through.
Further, if the pigment density becomes ununiform by the settlement of the inorganic pigments, there is a danger that printer nozzles are stopped up with the inorganic pigments in the case of use of an ink-jet printer. Therefore, the ink-jet printer nozzles for white ink are furnished with a washing device for the nozzles and a stirrer unit for the ink container.
Furthermore, stopping-up or clogging of the nozzle by the white pigments occurs to a felt-pen impregnated with eraser liquid or white ink and various problems with its practical use are caused.
The present invention was found considering the above mentioned defects of the conventional examples, and the purpose of the present invention is to provide a novel photosensitive composition for forming a white coating which can give white color without use of the inorganic pigments.
The photosensitive composition of the present invention is colorless, transparent at an ambient temperature, but the said composition is a photocurable composition which is cured and whitened by irradiation of ultraviolet light.
Further, the present invention provides a method of forming the above mentioned white coating.
The photosensitive composition of the present invention comprises photopolymerizable monomers, materials incompatible with the said photopolymerizable monomers, common solvents which have solubility characteristics to both the said photopolymerizable monomers and the said incompatible materials and photopolymerization initiators for curing the said photopolymerizable monomers by the irradiation of ultraviolet light, and is a colorless, transparent or pale colored transparent liquid as each component is soluble in one another at an ambient temperature. The said photosensitive composition is cured and whitened to result in a white substance by irradiation of ultraviolet light. Therefore, the said composition can be used as a paint or an ink for white color.