Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Screen other than for cathode-ray tube
Reexamination Certificate
2000-08-28
2002-09-24
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
C347S106000, C347S107000, C349S106000
Reexamination Certificate
active
06455209
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display employed in color liquid crystal displays, color video cameras, image scanners, personal computers, and the like, and a color filter, and a production method of the same.
In recent years, along with the rapid growth of portable personal computers, demand for liquid crystal displays has tended to increase, and at the same time, cost reduction of such devices has been demanded. Especially, cost reduction for expensive color filters has increasingly been demanded. Namely, desired are excellent quality color filters, which are produced at high yield, employing a short production process, and said production method thereof. However, those, which meet with requirements, have not yet been realized.
Color filters for liquid crystal display s are prepared by suitably arranging three filters of blue (B), green (G), and red (R) color. one color filter forms each pixel, and the cell size formed by one pixel is approximately (60 to 100 &mgr;m)×(180 to 300 &mgr;m). In order to minimize surface reflection, each pixel cell is surrounded by a partition wall, that is, a black matrix (hereinafter referred to as BM).
Said color filter is a simple structure. However, due to its complicated and lengthy production process, the yield is low which increases the cost. Thus, demanded are high quality color filters having reduced production cost.
The conventional production methods will now be described below.
The first production method of the color filter for liquid crystal display, which is most frequently employed, is a dyeing method.
In said method, a dyeable photosensitive polymer layer is formed on a support substrate. With the use of photolithography, patterning is carried out while matching the filter shape, and the resulting pattern is dyed.
This operation is repeated three times, one for each color, and subsequently a protective layer is provided. Thus a filter, having three colors of B, G, and R is formed.
The second method is a pigment dispersion method. In said method, a photosensitive resinous layer, into which pigments are dispersed, is formed on a support substrate. The resulting layer is subjected to patterning to obtain a monochromatic pattern.
This operation is also repeated three times, once for each color, and subsequently a protective layer is provided. Thus a filter, having three colors of B, G, and R, is formed.
The third method is an electrodeposition method. In this method, a filter pattern is formed on a support substrate, employing an electrode. Subsequently, the resulting support substrate is immersed into an electrodeposition coating composition comprising pigments, resins, and solvents, and a first color is electrodeposited by applying electricity to the electrode. Said operation is again repeated three times, once for each color, and subsequently a protective layer is provided. Thus a filter having three colors of B, G, and R is formed.
The fourth method is a printing method. In this method, pigments are dispersed into a thermohardening resin and printing is carried out on a glass support substrate. Again, said operation is repeated three times, once for each color, and subsequently a protective layer is provided. Thus a filter, having three colors of B, G, and R is formed.
Drawbacks common with conventional methods are as follows. In order to produce three colors of B, G, and R, it is necessary to repeat the process three times, such as spin coating of photosensitive resins, exposure, development, electrodeposition, printing, and the like. Thus, a lot of resources are wasted; due to the lengthy process, staining chances increase; the yield decreases and the cost increases.
Further, since in the electrodeposition method, dyes are deposited on the electrode, it is necessary to electrically connect an electrode pattern. Thus the pattern shape of filters is limited and at present, it is difficult to apply this method to the TFT use.
Still further, in the printing method, for example, in offset printing, ink is transferred twice and the resolution is degraded, and it is difficult to obtain a finely spaced pattern. Further, since the filter surface results in unevenness, a subsequent process to flatten the surface is required.
In order to overcome these drawbacks, color filters, which are prepared employing an ink jet method, are proposed.
This ink jet method is different from conventional methods and is a method in which each of R, G, and B inks is ejected onto a support substrate from the respective nozzles to form a colored layer. When this method is employed, the required amount of ink can be applied onto a required place at a specific time. Accordingly, there is no waste of ink. Further, since colored layers of R, G, and B are formed simultaneously, the production process is shortened, and it is possible to markedly reduce cost.
However, when a colored layer is formed by ejecting ink onto a pixel forming area (hereinafter occasionally referred to as a convex section) which is formed on the support substrate, employing said ink jet method, the support substrate, which is different from cloth and paper, does not absorb ink. As a result, the ink floods from one pixel (one concave section), and tends to mix with the ink in the adjacent pixel (the concave section).
Further, when physical parameters, such as surface tension, viscosity, and the like of the employed ink, are not adaptable to the surface free energy of the support substrate, the colored layer is repelled. As a result, the thickness of the filter layer loses its uniformity and the color density also tends to not be uniform and white spot marks or ink-omitted spots, where an ink could not be applied due to some defects, tend to form. Further, the surface of the colored layer tends to be roughened, and problems occur in which the layer is incapable of being brought into uniform contact with the liquid crystal layer.
Since the ink jet method is highly efficient and minimizes material waste compared to the conventional methods, it is possible to produce color filters at low cost. However, as described above, the ink in the concave sections tends to mix with that in adjacent concave sections and the ink density (the ink concentration) in the concave sections loses its uniformity. Particularly, big problems occur in which white spot marks tend to form due to lack of ink in parts of concave sections or in the boundary between the concave and convex sections.
In order to overcome the stated drawbacks, it is desirous that the ink, which is ejected onto one of concave sections, does not flow into adjacent concave sections while spreading across the surface of the black matrix area (hereinafter occasionally referred to as the convex section) so that the ink in one concave section does not mix with that in adjacent concave sections.
Further, it is desirous that the ink in the concave sections spreads uniformly.
In order to overcome the stated drawbacks, the surface of the support substrate is treated so that the convex section is ink-repellent while the concave section is ink-affinitive. However, the concave section, having ink affinity, is surrounded by the convex sections having ink repellency. As a result, even though ink spreads uniformly in the concave section, the ink is repelled in the area in contact with the convex section. Thus problems occur in which the color density at the periphery of the concave section decreases, and the contrast of displayed color images is degraded due to the tendency of formation of white spot marks.
As noted above, in order to manufacture filters employing the ink jet method, the treatment that a support substrate (a glass substrate) is treated in order to be accurately and minutely divided into ink-repellent areas and ink-affinitive areas, has been conducted in many prior arts.
For example, Japanese Patent Publication Open to Public Inspection Nos. 9-230123, 7-35916, and 4-123005 disclose methods to form color filters as follows. A photosensitive material and a material such as fluorine-contained r
Kikukawa Shozo
Murakami Takeshi
Nonaka Masaharu
Okaniwa Kenichiro
Bierman, Muserlian and Lucas
Konica Corporation
McPherson John A.
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