Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-06-18
2004-07-27
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S106000, C349S122000, C349S138000
Reexamination Certificate
active
06768531
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a so-called lateral electric field type liquid crystal display device.
2. Description of the Related Art
In a so-called lateral electric field type liquid crystal display device, on each pixel region on a liquid-crystal-side surface of one substrate out of respective substrates which are arranged to face each other in on opposed manner by way of liquid crystal, a pixel electrode and a counter electrode which generates an electric field between the pixel electrode and the counter electrode are formed, and the light transmittance of the liquid crystal is controlled by components of the electric field substantially parallel to the substrates.
In such a liquid crystal display device adapted to an active matrix type, on the liquid-crystal-side surface of the above-mentioned one substrate, regions which are surrounded by gate signal lines which are extended in the x direction and are arranged in parallel in the y direction and the drain signal lines which are extended in the y direction and are arranged in parallel in the x direction are formed as pixel regions, and a switching element which is operated in response to scanning signals from the gate line, a pixel electrode to which video signals are supplied from the drain signal lines through the switching element and a counter electrode which is arranged in a spaced-apart manner from the pixel electrode are formed on each pixel region.
Then, in performing the color display, there has been known a liquid crystal display device having the structure in which color filters are formed on the above-mentioned one substrate side and the color filters are not formed on the other substrate side. Such a structure is devised to reduce the influence of the displacement of alignment of the other substrate to one substrate to cope with the recent demand for high definition.
SUMMARY OF INVENTION
However, in the liquid crystal display device having such a constitution, the layer thickness is not made uniform over all color filters of red (R), green (G) and blue (B).
Such a situation occurs when the layer thickness of respective color filters are intentionally set to different values to attain the balance of transmittance or color purity among respective color filters of R, G and B or when the layer thickness is not made uniform over all color filters of red (R), green (G) and blue (B) due to the irregularities in manufacturing the color filters.
In these cases, when the pixel electrodes and the counter electrodes are formed by way of an interlayer insulation film on upper layers of the color filters, the height of the interlayer insulation film with respect to a surface of one substrate is reflected on the layer thickness of the color filters so that the respective heights of the pixel electrodes or the counter electrodes (heights from the surface of one substrate) differ.
This makes the layer thickness of the liquid crystal at respective pixels non-uniform so that the equal light transmittance cannot be obtained with respect to the respective color pixels.
Further, when the interlayer insulation film which is interposed between the pixel electrodes and the counter electrodes is made of resin material or the like which is formed by coating, the thickness of the interlayer insulation film differs depending on the respective pixels of different colors. Accordingly, the voltage drop which differs depending on the interlayer insulation film between the pixel electrodes and the counter electrodes displaces brightness-voltage characteristics thus leading to the collapsing of the color balance of the intermediate gray scale.
The present invention has been made in view of these circumstances and it is an object of the present invention to provide a liquid crystal display device which can enhance the display quality.
To briefly explain the summary of the typical inventions among the inventions disclosed in this specification, they are as follows.
Means 1.
A liquid crystal display device according to the present invention is, for example, characterized in that:
a pair of electrodes which constitute an upper layer and a lower layer with respect to an interlayer insulation film are formed as different layers at respective pixel regions on a liquid-crystal-side surface of one substrate out of respective substrates which are arranged to face each other in an opposed manner by way of liquid crystal,
at two pixel regions which are selected from the respective pixel regions, the heights of background layers on which the electrodes which constitute the lower layers with respect to the interlayer insulation films differ with respect to a surface of one substrate, and
the film thickness of the interlayer insulation film is set small with respect to the high background layer out of the respective background layers which differ in height and is set large with respect to the low background layer out of the respective background layers.
Means 2.
A liquid crystal display device according to the present invention is, for example, characterized in that:
a pair of electrodes which constitute an upper layer and a lower layer with respect to an interlayer insulation film are formed on at least color filters as different layers at respective pixel regions on a liquid-crystal-side surface of one substrate out of respective substrates which are arranged to face each other in an opposed manner by way of liquid crystal from the one substrate side,
at two pixel regions which are selected from the respective pixel regions and on which two color filters of different colors are formed, the heights of surfaces of the color filters differ with respect to a surface of one substrate, and
the film thickness of the interlayer insulation film is set to satisfy a following formula (1).
0<film thickness difference of the interlayer insulation film between pixel regions<film thickness difference of the color filters between pixel regions (1)
Means 3.
A liquid crystal display device according to the present invention is, for example, characterized in that:
a pair of electrodes which constitute an upper layer and a lower layer with respect to an interlayer insulation film are formed on at least color filters as different layers at respective pixel regions on a liquid-crystal-side surface of one substrate out of respective substrates which are arranged to face each other in an opposed manner by way of liquid crystal from the one substrate side,
at two pixel regions which are selected from the respective pixel regions and on which two color filters of different colors are formed, the heights of surfaces of the color filters differ with respect to a surface of one substrate, and
the film thickness of the interlayer insulation film is set to satisfy a following formula (2).
¼×film thickness difference of color filter between pixel regions<film thickness difference of interlayer insulation film between pixel regions, <¾×film thickness difference of color filter between pixel regions (2)
Means 4.
A liquid crystal display device according to the present invention is, for example, based on the constitution of the means 2 or 3, characterized in that the film thickness of the interlayer insulation film is set to satisfy a following formula (3).
film thickness of interlayer insulation film<{fraction (3/2)} times film thickness of thickest color filter (3)
Means 5.
A liquid crystal display device according to the present invention is, for example, based on the constitution of the means 2 or 3, characterized in that the film thickness of the interlayer insulation film is set to satisfy a following formula (4).
¼ times film thickness of thinnest color filter<film thickness of interlayer insulation film<{fraction (3/2)} times film thickness of thickest color filter (4)
Means 6.
A liquid crystal display device according to the present invention is, for example, character
Ochiai Takahiro
Oke Ryutaro
Ono Kikuo
Yanagawa Kazuhiko
A. Marquez, Esq. Juan Carlos
Duong Tai
Fisher Esq. Stanley P.
Reed Smith LLP
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