Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Screen other than for cathode-ray tube
Reexamination Certificate
1999-05-27
2001-07-03
McPherson, John A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Screen other than for cathode-ray tube
Reexamination Certificate
active
06255025
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a filter used in a CCD camera, various display devices such as a liquid crystal display device, and an image sensor, and particularly it relates to a color filter.
2. Description of the Related Art
As a process for producing a color filter, (1) a dyeing method, (2) a pigment dispersion method, (3) a printing method, (4) an ink jet method and (5) an electrodeposition method have been known.
The dyeing method (1) is frequently used in a color charge-coupled device (CCD) since it provides a high transmittance and rich hues, and the technique has been fully established. However, the light resistance is inferior because of the use of a dye, and the number of steps in the production process is large due to the use of photolithography, which results in a high production cost. Therefore, the production for a liquid crystal display device (LCD) is being substituted by the pigment dispersion method.
The pigment dispersion method (2) is the main stream of the process for producing a color filter in recent years. This production process has advantages in that the resulting color filter has a high resolution and a high quality, and the technique has been fully established, but has a disadvantage in that the number of steps in the production process is large due to the use of photolithography, which results in a high production cost.
The printing method (3) does not require photolithography in the formation of R, G and B layers and exhibits a high mass-productivity, but is inferior in resolution and uniformity of the film thickness of the resulting color filter.
The ink jet method (4) does not require photolithography in the formation of R, G and B layers, but is inferior in resolution. Furthermore, it involves a high possibility of mixing the colors of the adjacent filter layers and is inferior in positional accuracy.
In the electrodeposition method (5), an electrodeposition coating is conducted in such a manner in that a high voltage of about 70 V is applied to a light transmissible electrode, which has been previously patterned, in an electrolytic solution comprising a water soluble polymer having a pigment dispersed therein, to form an electrodeposition film, and color filter layers of R, G and B are obtained by repeating these procedures three times. This method has a disadvantage in that it cannot be used for a liquid crystal driven by a TFT because the shape of the pattern is restricted since the light transmissible electrode has been previously patterned by photolithography, which is used as an electrode for electrodeposition.
In general, the color filter for a liquid crystal display cannot be used if it comprises color filter layers only, but it should be a color filter in that gaps among microcells are covered with a black matrix. In order to produce a color filter having a high resolution and a high controllability, the photolithography technique is used for producing the filter cells for each color and the black matrix, which is one of the factors of increasing the production cost.
Therefore, if a product having the equal performance can be obtained without using photolithography, a process for producing a color filter can be realized in that the number of steps is reduced to increase the yield, and the production cost is greatly reduced.
As a process for producing a color filter by using no photolithography, for example, a process for producing a color filter by an electrodeposition method using a photo-memory N-type photosemiconductor has been proposed in JP-A-5-150112.
This process comprises the following steps:
(1) An electrodeposition substrate is produced by forming a layer comprising a photo-memory N-type photosemiconductor, such as zinc oxide dispersed in a resin, on a conductive substrate, such as a stainless plate. The substrate is exposed to an ultraviolet light through a photomask corresponding to one color of the color filter, to generate conductivity only in the exposedpart (i.e., the resistance is decreased), whereas the insulating property of the non-exposed part is maintained.
(2) The conductive substrate, in which the exposed part is maintained to have conductivity due to the use of the photo-memory N-type photosemiconductor, is immersed in an electrodeposition solution for forming an electrodeposition film of that color, and a colored electrodeposition film is formed by electrodeposition by applying a voltage of from 20 to 80 V. At this time, the voltage is applied in such a manner that the N-type photosemiconductor becomes a cathode, the electrodeposition solution contains a cationic electrodeposition material.
(3) The steps of exposure and electrodeposition are repeated for each of the colors necessary for the color filter.
(4) The whole surface of the electrodeposition substrate having thereon a colored electrodeposition film is exposed to an ultraviolet ray, to generate conductivity on a part of the photo-memory photosemiconductor that is not covered with the colored electrodeposition film, and then a black matrix is formed by conducting metallic plating or electrodeposition of a black electrodeposition film by using an electrodeposition solution containing a mixed black pigment.
(5) The multi-color filter layer thus formed is transferred to a transparent substrate.
In this process, in order to improve the releasability between the multi-color filter layer and the photo-memory N-type photosemiconductor during transfer, a releasing layer has been provided between the two layers, or another step is required in that metallic plating is conducted on the whole surface of the photosemiconductor before providing the color filter layer, and after the transfer, the metallic plating layer remaining as attached on the multi-color filter layer is removed by dissolving.
This process realizes reduction in production cost in comparison with the related process using the photolithography method in the standpoint not using the photolithography method. However, it still requires a large number of steps in that the transfer step is required, exposure and electrodeposition are conducted in separate steps, and a step of providing the releasing layer is required.
Accordingly, a process for producing a color filter having a high performance in a low cost, in which the photolithography method is not used, and the number of steps is small, has been demanded.
SUMMARY OF THE INVENTION
An object of the invention is to provide a process for producing a color filter, in which the photolithography method is not used, the number of manufacturing steps is small, and the production cost is low.
Another object of the invention is to provide a color filter having excellent characteristics, in which a clear boundary is present between an edge part of a filter part and an edge part of a black matrix, which suffers no leakage or light, and the resolution and the controllability are high, by the process for producing a color filter.
The above and other objects of the invention are attained by the processes (1) and (2) for producing a color filter (1) and (2) described below.
(1) A process for producing a filter comprising:
a step of arranging an electrodeposition substrate, which comprises a light transmissible support having a light transmissible conductive film and a photosemiconductor thin film with a photoelectromotive function in this order provided thereon, in such a manner that at least the photosemiconductor thin film is immersed in an electrodeposition solution containing a colored electrodeposition material;
a step of imagewise exposing the electrodeposition substrate with applying a voltage or an electric current to the conductive film, to form a colored electrodeposition film in an exposed part;
a step of immersing at least the photosemiconductor thin film, on which the colored electrodeposition film has been formed, of the electrodeposition substrate in a metallic plating solution; and
a step of applying a voltage or an electric current to the conductive film, to forma black matrix comprising a m
Akutsu Eiichi
Ohtsu Shigemi
Pu Lyong Sun
Shimizu Keishi
Fuji 'Xerox Co., Ltd.
McPherson John A.
Oliff & Berridg,e PLC
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