Methods of making LCD devices having color filter

Details Methods of making LCD devices having color filter Methods of making LCD devices having color filter

2000-02-18

2001-11-27

Sikes, William L. (Department: 2871)

Liquid crystal cells, elements and systems

Particular structure

Having significant detail of cell structure only

C349S095000, C349S110000, C430S007000

Reexamination Certificate

active

06323920

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to liquid crystal display (LCD) devices and fabrication methods therefor, and more particularly to color filters for LCD devices and fabrication methods therefor.
BACKGROUND OF THE INVENTION
Liquid crystal display (LCD) devices are widely used for flat panel displays of images. As is well known to those having skill in the art, an LCD device generally includes a thin film transistor panel and a color filter panel which are spaced apart from one another. The thin film transistor panel generally includes a first substrate and a plurality of thin film transistors which are formed on the surface thereof. The color filter panel generally includes a second substrate and a color filter layer formed on a surface thereof. As is well known to those having skill in the art, it is generally desirable for LCD devices to have a high aperture ratio, to thereby improve the resolution thereof. The aperture ratio is the area through which a light beam is transmitted through the panel.
FIG. 1
is a cross-sectional view of a conventional color filter for an LCD device. As shown in
FIG. 1
, color filter
5
includes a light shielding layer
2
on a transparent substrate
1
, such as glass. The light shielding layer includes an array of apertures therein. The light shielding layer
2
forms a black matrix for the color filter.
A color filter layer including red, green and blue color filters
3
-
1
,
3
-
2
and
3
-
3
respectively, is formed on the light shielding layer
2
and spans the apertures therein. The color filters may be formed by depositing color dyes on the light shielding layer
2
. Each color filter
3
-
1
,
3
-
2
and
3
-
3
is formed between two adjacent light shielding portions and on the ends of the two adjacent light shielding portions. A protective layer
4
is formed on the light shielding layer
2
and the color filter layer.
A color filter according to
FIG. 1
may be fabricated by forming an opaque layer, such as chromium, chromium oxide or organic material on a glass substrate
1
and then pattern in the opaque layer to form the light shielding layer
2
. Color dyes of red, green and blue are then sequentially deposited and patterned to form the color filters
3
-
1
,
3
-
2
and
3
-
3
respectively. Finally, a protective layer
4
is deposited over the color filters and the light shielding layer, to protect the color filter layer and to provide a smooth outer surface for the color filter.
In a conventional LCD device as described above, the aperture ratio is generally dependent upon the area through which a light beam from a back light on the thin film transistor panel is transmitted. In order to improve the resolution of the display, higher aperture ratios are generally desirable.
However, as shown in
FIG. 1
, a light beam
6
which is transmitted from the back light on the thin film transistor panel, will only penetrate the portion A of the color filter layer, but will not penetrate the portion A′, due to the light shielding layer
2
. Accordingly, the aperture ratio in a conventional LCD device may be reduced and it may become difficult to increase the resolution thereof.
In order to increase the aperture ratio, it may be desirable to form larger apertures in the light shielding layer
2
. However, if the apertures in the light shielding layer are enlarged, it may be difficult to align the color filters
3
-
1
,
3
-
2
and
3
-
3
to the apertures in the light shielding layer
2
. Moreover, planarity problems may be produced.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide improved color filters for liquid crystal display (LCD) devices and methods of fabricating the same.
It is another object of the present invention to provide LCD device color filters which can have high aperture ratios without requiring larger apertures in the light shielding layers thereof.
It is another object of the present invention to provide methods of fabricating color filters for LCD devices which do not require highly precise alignment between color filter layers and light shielding layers thereof.
These and other objects are provided, according to the present invention, by color filters for LCD devices and fabrication methods therefor which include a concave lens layer in the color filter. The concave lens layer, which may be formed from reflowed photoresist, can increase the aperture ratio without requiring reduction in the size of the apertures of the light shielding layer. Thus, high aperture ratio LCD devices can be provided without requiring ultra-high resolution color filters.
In particular, color filters for LCDs according to the invention include a transparent substrate, and a light shielding layer on the transparent substrate. The light shielding layer includes an array of apertures therein. The color filter layer spans the apertures. The color filter also includes means for dispersing light which passes through the color filter layer.
Preferably, the transparent substrate includes front and rear surfaces. The light shielding layer and the color filter are on the front surface, and the dispersing means is on the rear surface. The color filter layer is preferably on the light shielding layer, opposite the transparent substrate, and extends into and across the apertures. The color filter layer more preferably fills the apertures.
The dispersing means is preferably a lens layer, on the rear surface of the substrate. The lens layer is located opposite the light shielding layer and extends at least partially to opposite the apertures in the light shielding layer. The lens layer is preferably a concave lens layer formed of photoresist. The lens layer can increase the aperture ratio without requiring an increase in the size of the apertures in the light shielding layer.
Color filters for LCDs according to the present invention may be fabricated using self-aligned methods. In particular, a light shielding layer, including an array of first apertures therein, is formed on the front face of a transparent substrate. A light dispersing layer is formed on the rear face of the transparent substrate. The light dispersing layer is preferably reflowable photoresist.
The light dispersing layer is patterned through the transparent substrate using the light shielding layer as a mask, to form a patterned light dispersing layer having several apertures opposite the first apertures in the light shielding layer. The patterned light dispersing layer is flowed to form a lens layer opposite the light shielding layer which extends on the rear surface at least partially to opposite the array of first apertures. A color filter layer is formed on the light shielding layer, spanning the first apertures therein. Since methods according to the present invention can form color filters having high aperture ratios without requiring precise alignment of the light shielding layer and a color filter layer, high resolution LCD devices can be formed, having a wide viewing angle.


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patent: 5101279 (1992-03-01), Kurematsu et al.
patent: 5187599 (1993-02-01), Nakanishi et al.
patent: 5398125 (1995-03-01), Willet et al.
patent: 5412506 (1995-05-01), Felblum et al.
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patent: 5666226 (1997-09-01), Ezza et al.
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