Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-07-13
2004-11-30
Chowdhury, Tarifur R. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
Reexamination Certificate
active
06825904
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to liquid crystal devices, color filter substrates, methods for manufacturing liquid crystal devices, and methods for manufacturing color filter substrates.
2. Description of the Related Art
In general, in a liquid crystal device having a liquid crystal panel in which a pair of substrates composed of a glass or the like holds liquid crystal therebetween, a color filter substrate may be used in some cases in order to perform color display. In this color filter substrate, color layers (for example, R (red), G (green), B (blue), and BM (black: black matrix or black mask)) for constituting a filter portion of the color filter are formed on a surface of a transparent substrate such as a glass. These color layers are formed of a resin containing a coloring agent, such as a pigment or a dye.
In the color filter, a surface protective layer composed of a transparent resin or the like is generally formed on the color layers. This surface protective layer is formed for preventing infiltration of a chemical solution when another layer (such as a transparent electrode pattern) is further formed on the color filter and, in addition, is formed so as to ensure the flatness of the surface of the color filter.
On the surface of the color filter, transparent electrodes composed of a transparent conductive material such as ITO (Indium Tin Oxide) may be formed in some cases. However, in general, since the adhesion between the surface protective layer and the transparent electrodes described above is insufficient, when the transparent electrodes are formed directly on the color filter, there has been a problem in that the pattern accuracy of the electrode pattern cannot be ensured. Accordingly, heretofore, an insulating film (an intermediate layer) composed of SiO
2
is formed by sputtering or the like on the surface of the surface protective layer formed on the color filter, and the transparent electrodes are formed on this insulating film.
When the transparent electrodes are formed on the insulating film described above, since the transparent electrodes are formed by patterning a transparent conductive film formed by sputtering or the like, a resist pattern on the transparent conductive layer must be developed by using an alkaline solution such as an aqueous solution containing potassium hydroxide, and in addition, after the transparent electrodes are formed by patterning, the remaining resist pattern on the electrode pattern must be removed by an alkaline solution.
However, since an insulating film composed of SiO
2
has poor resistance against the alkaline solution described above, the insulating film is adversely influenced by this chemical treatment, for example, part of the insulating film is dissolved by the alkaline solution while the transparent electrodes are formed by patterning, and as a result, the insulating film may be separated from the color filter in some cases.
In addition, when an insulating film composed of SiO
2
is formed by using a sputtering apparatus, SiO
2
adhered to the inside of the apparatus is spread in the powdered form, and as a result, there is a problem in that the environment is contaminated. The reason for this is that since SiO
2
has a coefficient of thermal expansion significantly different from those of metal constituent members used inside the apparatus and also has the property of easily absorbing the moisture in air, the SiO
2
adhered to the inside of the apparatus is easily separated from the inside surface of the apparatus after sputtering is completed. In addition, when a SiO
2
film is formed by sputtering, an abnormal discharge is likely to occur on the target due to a low dielectric constant thereof, and hence, there is also a problem in that it is difficult to obtain stable film-forming conditions.
Furthermore, compared to the transparent electrode described above generally having a high refractive index of approximately 1.8 to 1.9, since the insulating film composed of SiO
2
has a low refractive index (n=1.455), the light transmittance is decreased due to the occurrence of light reflection or interference at the interface between the insulating film and the transparent electrode, and as a result, there has been a problem in that the brightness of display is decreased.
Accordingly, the present invention was made to solve the problems described above, and an object of the present invention is, in a color filter substrate or a liquid crystal device having a conductive film formed on the color filter, to provide a structure which can suppress the problems caused by an insulating film provided between the color filter and the conductive film.
SUMMARY OF THE INVENTION
A liquid crystal device of the present invention comprises: a first substrate; a second substrate disposed so as to oppose the first substrate; a color layer provided on the first substrate; an insulating film provided on the color layer and comprising at least one of Ta
2
O
5
, ZrO
2
, and TiO
2
as a primary component; and a conductive film having the property of transmitting light provided on the insulating film.
Since Ta
2
O
5
, ZrO
2
, and TiO
2
each has a refractive index higher than that of SiO
2
, the difference in refractive index from the transparent conductive layer can be decreased, and the optical loss at a laminated portion formed of the transparent conductive layer and the insulating film can be decreased. In particular, the refractive index of the metal oxide described above which is formed by a vapor phase method can also be controlled or adjusted by the film-forming conditions therefor. In addition, since the insulating film used in the present invention is unlikely to produce particles compared to that composed of SiO
2
, the degree of contamination in the environment in the manufacturing process can be decreased.
In addition, since both Ta
2
O
5
and ZrO
2
formed by a vapor phase method have sufficient corrosion resistance against an alkaline solution, the separation thereof is unlikely to occur when an alkaline solution is used for patterning the transparent conductive layer. That is, the insulating film preferably comprises at least one of Ta
2
O
5
and ZrO
2
so as to have alkali resistance.
When an optional wavelength in the visible wavelength region is represented by &lgr;, it is preferable that the sum of the optical thickness of the insulating film and the optical thickness of the conductive film of the present invention be substantially equal to the product of &lgr;/2 and a natural number. In the case described above, at the surface of the insulating film at the color filter side and at the surface of the conductive film at the side opposite to the color filter, reflectance of a visible light can be decreased, and as a result, the light transmittance can be increased.
The optical thickness can be represented by n·d (n is the refractive index of the laminated portion, and d is the total thickness of the insulating film and the conductive film) when the insulating film and the conductive film have substantially the same refractive index, and when the refractive index of the insulating film and the refractive index of the conductive film substantially differ from each other, the optical thickness can be represented by n
1
·d
1
+n
2
·d
2
(n
1
is the refractive index of the insulating film, d
1
is the thickness of the insulating film, n
2
is the refractive index of the conductive film, and d
2
is the thickness of the conductive film). In addition, the visible wavelength region described above is a region in which the wavelength is in the range of from 380 nm to 780 nm. As a typical wavelength in the visible wavelength region, &lgr; described above is preferably 550 nm.
In the present invention, it is preferable that a transparent resin film be further provided between the color layer and the insulating film. This transparent resin film (the surface protective layer described later) is generally formed so as to protect the color layer and, in addition,
Chowdhury Tarifur R.
Harness & Dickey & Pierce P.L.C.
Rude Timothy L
Seiko Epson Corporation
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