Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1998-11-03
2001-09-04
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S111000, C349S137000, C349S106000, C430S007000, C428S432000
Reexamination Certificate
active
06285424
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a black mask, a color filter and a liquid crystal display.
2. Description of the Related Art
A STN or TFT color liquid crystal display includes a color filter at a position opposite to a liquid crystal layer. The color filter has colored resins separated by a black mask having a plurality of apertures, and the visibility of the liquid crystal display depends upon the characteristics of the black mask. Conventional black masks are described in JP-A-8-179301, 8-36171, and 9-243801.
In a color filter for use in a liquid crystal display, it is required to reduce the optical reflectivity on the surface of a black mask, and the wavelength dependence of the reflectivity in the visible wavelength range in order to improve the visibility of a panel, that is, to make the change of the reflectivity in the wavelength range (wavelength dependence of reflectivity) small.
The black mask described in JP-A-8-179301 is so constructed that all of the layers contain the same kind of metal. That is, the black mask described in the above publication comprises a first antireflection film consisting of a chromium compound, a second antireflection film consisting of a chromium compound, and a screening film consisting of chromium, the films being successively formed. More particularly, the first antireflection film consisting of a chromium compound contains Cr, O, N, and C, the second antireflection film consisting of a chromium compound contains Cr, N, O, and C, and the screening film consisting of chromium contains only chromium metal. However, the wavelength dependence of the reflectivity on the surface of this black mask remains large, and the reflectivity is not reduced sufficiently.
The first antireflection film consisting of a chromium compound in the black mask described in the above JP-A-8-36171 contains chromium and oxygen as main components, the second antireflection film consisting of a chromium compound contains chromium and nitrogen as main components, and the screening film consisting of chromium contains chromium metal as a main component. However, there is a substantial difference in etching rates among these films. The etching rates depend upon the conditions of the film-forming process. Assuming the etching rate of the screening film mainly composed of chromium metal being subjected to wet etching by the use of an etchant such as ammonium cerium (IV) nitrate to be 1, the etching rate of the first antireflection film mainly composed of chromium and oxygen is generally 0.5 or less, while the etching rate of the second antireflection film mainly composed of chromium and nitrogen is generally 5 or more. Therefore, when the black mask of the above-described three-layer structure is subjected to wet etching, a precise pattern can be hardly formed due to the difference in etching rates among these films.
The black mask described in JP-A-9-243801 does not contain a chromium component. However, a precise pattern cannot be formed due to the difference in etching rate among the three layers.
An object of the present invention is to provide a black mask having improved etching characteristics at the manufacturing process, having low reflectivity in the whole visible wavelength range, and having a small wavelength dependence of reflectivity, which can be preferably used for a color filter and a liquid crystal display which can show clear pictures.
SUMMARY OF THE INVENTION
The black mask of the present invention comprises: a first and a second antireflection films each comprising oxide, nitride, carbide, oxide nitride, oxide carbide, nitride carbide, or oxide nitride carbide of at least one kind of metal selected from the group consisting of chromium, molybdenum, tungsten, nickel, and germanium, and said films each having a different composition; and a screening film comprising at least one kind of metal selected from the group consisting of chromium, molybdenum, tungsten, nickel, and germanium; wherein said three films are successively formed on a transparent substrate, and at least one but not all of said three films contains chromium.
REFERENCES:
patent: 4720442 (1988-01-01), Shinkai et al.
patent: 5419969 (1995-05-01), Miyazaki et al.
patent: 5570212 (1996-10-01), Steigerwald
patent: 6128057 (2000-10-01), Suzuki et al.
Birch & Stewart Kolasch & Birch, LLP
Sumitomo Chemical Company Limited
Ton Toan
LandOfFree
Black mask, color filter and liquid crystal display does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Black mask, color filter and liquid crystal display, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Black mask, color filter and liquid crystal display will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2481377