Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-01-18
2002-09-03
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S110000, C349S042000
Reexamination Certificate
active
06445432
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color liquid crystal display panel which comprises thin film transistors, and more particularly, to a color liquid crystal display panel in which tight contact between a black matrix and an underlying member is improved so as to achieve high fineness.
2. Description of the Related Art
A color liquid crystal display panel comprises two glass substrates and a liquid crystal layer which is disposed between the glass substrates. In general, in a panel of the thin film transistor (TFT; Thin Film Transistor) type, color layers of three colors (red, green and blue) are formed on a counter glass substrate which is faced with a TFT-side glass substrate which seats TFTs. However, since such a structure demands large margins for a black matrix which is disposed between adjacent inter-pixel opening portions to improve contrast, it is difficult to enhance the fineness of the panel with this structure.
Against this background, a color liquid crystal display panel seating three color layers on a TFT-side substrate has attracted attention over recent years.
FIG. 1
is a cross sectional view of a conventional color liquid crystal display panel in which three color layers are formed on a TFT-side substrate.
In a conventional color liquid crystal display panel, a liquid crystal layer
117
is disposed between a TFT-side glass substrate
101
and a counter glass substrate
102
. In the following, the closer sides to the liquid crystal layer
117
of the glass substrates
101
and
102
will be referred to as “the inner sides” and the opposite sides will be referred to as “the outer sides.”
Gate electrodes
103
are formed on an inner-side surface of the TFT-Side glass substrate
101
, and a gate insulation film
104
is formed so as to cover the gate electrodes
103
. The gate electrodes
103
are connected to gate lines (not shown) which extend in the direction of rows in the panel.
A semiconductor layer
105
is formed on an inner-side surface of the gate insulation film
104
at positions corresponding to the respective gate electrodes
103
, and drain electrodes
106
and source electrodes
107
are formed so as to sandwich the semiconductor layer
105
. The drain electrodes
106
are connected to signal lines (not shown) which extend in the direction of columns. On the other hand, the source electrodes
107
are intrinsic to the respective TFTs
108
. In this manner, the plurality of TFTs
108
are arranged in the form of a matrix. Further, an insulation film
109
is formed entirely over the inner-side surface of the TFT-side glass substrate
101
so as to coat the TFTs
108
.
A black resin layer (black matrix)
113
is formed on the respective TFTs
108
so as to sandwich the insulation layer
109
with the respective TFTs
108
. The black resin layer
113
is formed also on the respective gate lines, the respective signal lines and a frame portion
120
of the panel so as to sandwich the insulation layer
109
with them.
At the inter-pixel opening portions from which the red light is to be emitted, a red layer
110
alone is disposed as a color layer on the insulation layer
109
. At the inter-pixel opening portions from which the green light is to be emitted, a green layer
111
alone is disposed as a color layer on the insulation layer
109
. At the inter-pixel opening portions from which the blue light is to be emitted, a blue layer (not shown) alone is disposed an a color layer on the insulation layer
109
.
Still further disposed entirely on the inner-side surface of the TFT-side glass substrate
101
is a flattened film
114
which has a flattened surface and covers the TFTs
108
, the black resin layer
113
and the like. The flattened film
114
includes a plurality of contact holes
118
which reach even to the respective source electrodes
107
, and pixel electrodes
115
of an ITO film are formed inside the contact holes
118
. The pixel electrodes
115
protrude beyond and extend on the flattened film
114
, thereby covering the color layers at the respective inter-pixel opening portions.
Meanwhile, a counter transparent common electrode
116
is formed on the inner-side surface of the counter glass substrate
102
such that the counter transparent common electrode
116
stretches to face the respective pixel electrodes
115
. The counter transparent common electrode
116
is formed of an ITO film.
A sealant
119
surrounding the liquid crystal layer
117
is disposed between the glass substrates
101
and
102
In addition, an alignment film (not shown) is formed on each of the flattened film
114
and the counter transparent common electrode
116
.
In such a conventional color liquid crystal display panel, since the black matrix
113
is formed on the inner-side surface of the TFT-side glass substrate
101
it is possible to reduce the widths of the black matrix
113
. As a result, it is possible to improve an opening ratio beyond that heretofore achievable. For example, an XGA panel can have an opening ratio of about 80%.
In the case of the conventional color liquid crystal display panel as above, in which the three color layers are formed on the TFT-side substrate, during fabrication of the panel, after applying, developing and baking on the respective color layers or before forming the respective color layers, a black resin film which is a raw material of the black matrix is applied, developed and baked. Since the width used under the optimal condition for development (development margin) of the black resin film is extremely narrow, there is a problem in that the black resin film easily falls off the insulation film
109
while being developed. The black resin film falls off because the black resin film at its surface portions absorbs light during patterning by photolithography and thus fails to be sensitized inside. Although improvement is possible to a certain extent if the black resin film is formed as a thin film, this solution leads to a new problem of lowered optical density. As an optical density, an OD value of 3.0 or higher is said to be necessary. Further, in an effort to increase an optical density, an increased carbon content results in a trade off in that a ratio of an acrylic component, which contributes to a tight contact with the underlying member, decreases and hence a contact capability decreases. In short, such stripping of the black resin film becomes particularly remarkable when the black matrix
113
is formed thick or the carbon content in the black matrix
113
is increased and the like. This is another problem in that it is difficult to enhance optical density, namely, light shielding capability for the purpose of obtaining excellent contrast. In contrast, in the case of a color filter, since light is transmitted even inside, sufficient sensitizing is possible.
Further, a color liquid crystal display panel which uses a laminated member of three color layers as a light shielding film has been proposed (Japanese Patent Laid-Open Publication No. Sho 62-250416). However, even if such a laminated member is used on a TFT-side glass substrate as an alternative to a black matrix, sufficient shielding of light is not achieved, and therefore, the OD value decreases and contrast accordingly decreases.
On the other hand, as such a color filter for liquid crystal display in which three color layers are formed on a counter glass substrate described earlier, a color filter in which adjacent color layers are overlapped at their boundaries has been proposed (Japanese Patent Laid-Open Publication No Sho 63-173023). In the case of the color filter described in this official gazette, black ink is applied using a roller to the overlap portions described above to thereby form the black matrix. However, in such a color filter, since a light shielding rate becomes different depending on the color of the adjacent color layer, the contrast of a displayed image varies, and hence, the image appears uneven.
SUMMARY OF THE INVENTION
According to the present invention, a color liquid crys
Kikkawa Hironori
Maruyama Muneo
Okamoto Mamoru
Sakamoto Michiaki
Watanabe Takahiko
Hayes & Soloway P.C.
Nguyen Hoan C.
Sikes William L.
LandOfFree
Color liquid crystal display panel does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Color liquid crystal display panel, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Color liquid crystal display panel will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2886336