1. Field of the Invention
The present invention relates to a color filter composition, a color display device, and a production method of same.
2. Description of the Related Art
In recent years, there has been much studies on differentiation of products through improvements in the performance of the color display device, represented by a vacuum fluorescent light emitting device (VFD), an electrofluorescent light emitting device (EL), a photodiode light emitting device (LED), and other image tubes or a plasma display device (PDP), a field emission display device (FED), a cathode ray tube (CRT), and other picture tubes and on a reduction of costs by reexamination of the mass production system.
In a CRT such represented by a Braun tube of a television set, an electron beam emitted from an electron gun strikes the surface of the layer of fluophors to energize the fluophor particles and cause emission of light for the display. The diversification of various kinds of visual apparatuses using CRTs accompanying the advances in the field of electronics in recent years has led to various improvements and developments.
For example, the fluophors used in the CRTs are improved in color purity by coating an inorganic pigment on the fluophor particles. However, since the coated pigment is adhered to the fluophor particles in state and not formed as a separate layer, the luminance of the emission of the fluophors has been lowered.
In order to compensate for this state, it may be considered to raise the output of the electron beam irradiated to the fluophor surface, but this method is liable to lead to a deviation in color due to the thermal expansion of the shadow mask and a reduction of the service life of the fluophors.
Further, a color display device provided with a color filter containing at least one type of metal compound of nickel and cobalt and also using a dye has been proposed (Japanese Unexamined Patent Publication (Kokai) No. 2-46403).
A dye filter, however, is insufficient in the heat resistance and light resistance, so a sintering step cannot be used and thus it is used in a laminated glass system. Further, a color display device of this dye filter system cannot be used for the purpose of an outdoor video apparatus.
Also, in the process for production of a color CRT having a fluophor surface on the inner surface of a face plate, there is known a process for production of a CRT equipped with a color filter wherein a ultrafine particle pigment dispersion is coated on the inner surface of a face plate made of glass to form a pigment layer and then a fluopher suspension is further coated to form a laminate layer, then collective exposure via the shadow mask and development for patterning (photolithography) are carried out.
Nevertheless, this photolithography method has disadvantages of the throughput and stability. Namely, a UV crosslinking type vehicle (PVA/ADC-base) has a pot life, so it is impossible to avoid a coarsening of the pigment due to an aging by a dark reaction. This leads to a reduction of the workability due to the frequency of exchange of the dispersions and a poor stability of the quality (deterioration of transmittance).
Further, a difficult point at the time of coating of the laminate layers of the color filter and the fluophor layer has been the fact that an upper coating layer (10 .mu.m.ltoreq.fluophor thick film) invades a lower coating layer (3 .mu.m.ltoreq.color filter thin film) due to a double coating by the same vehicle-base. Accordingly, it is hard to obtain a good layer-separated coating film, which has led to a fluctuation in the quality.
Further, in such a color display device equipped with the color filter, for improvement of the contrast, it is necessary to raise the coloring density of the color filter. Since coarse particles of 1 .mu.m or more are mixed in and also the distribution of the particle size is wide at the conventional pigment dispersion level, the transmittance of light is degraded. Thus there has been a limit to raising the contrast and increasing the color reproduction range.