Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1999-10-19
2003-09-16
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S122000, C349S138000
Reexamination Certificate
active
06621540
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a reflection type liquid crystal display.
2. Description of the Related Art
A number of reflection type liquid crystal displays that create a recognizable image by reflecting incident light originating from the observer's side have been proposed to date.
FIG. 1
is a sectional view of one such conventional reflection type liquid crystal display.
As shown in
FIG. 1
, such a conventional reflection type liquid crystal display has a thin film transistor (hereinafter referred to as the TFT) as a switching element on an insulating substrate
10
of quartz glass or non-alkali glass or the like.
First, gate electrodes
11
of a refractory metal, such as chromium (Cr) or molybdenum (Mo), a gate insulating film
12
, and active layers
13
of polysilicon films are successively formed on the insulating substrate (TFT substrate)
10
.
Each active layer
13
includes channels
13
c
formed above the gate electrodes
11
, and a source
13
s
and a drain
13
d
that are formed on both sides of the channels
13
c
by ion doping using stopper insulating films
14
on the channels
13
c
as masks.
Then, an inter-layer insulating film
15
, which includes a SiO
2
film, a SiN film and a SiO
2
film deposited in succession, is formed over the entire surfaces of the gate insulating film
12
, the active layer
13
and the stopper insulating films
14
. A drain electrode
16
is formed by filling a contact hole, which is formed to correspond to the drain
13
d
, with a metal, such as aluminum (Al). Furthermore, a planarization insulating film
17
, which consists of an organic resin, for example, and serves to flatten the surface, is formed over the entire surface. A contact hole is formed at a location of the planarization insulating film
17
corresponding to the source
13
s
. A reflective display electrode
19
as a reflection electrode, which consists of aluminum (Al) in contact with the source
13
s
through this contact hole and serves also as the source electrode
18
, is formed on the planarization insulating film
17
. An alignment film
20
consisting of an organic resin, such as polyimide, and aligning liquid crystal elements
21
, is formed on the reflective display electrode
19
.
On a counter electrode substrate
30
facing the TFT substrate
10
and comprising an insulating substrate, are provided a color filter
31
including primary colors, red (R), green (G), and blue (B) and a black matrix
32
with a function to shield light; a protective film
33
of a resin formed on the color filter
31
; and a counter electrode
34
and an alignment film
35
formed over the entire surface of the protective film
33
. On the side not facing the TFT substrate
10
, a polarizer
41
is located. The counter electrode substrate
30
and the TFT substrate
10
are bonded together with their peripheries sealed with a sealing bond (not shown), thus forming a space inside, and this space is filled with a twisted nematic (TN) liquid crystal
21
.
The propagation of light when a user views the reflection type liquid crystal display as above is described below with reference to FIG.
1
.
As indicated by a broken line, a natural light
100
coming from the outside enters from the polarizer
41
on the side of an observer
101
, and passes through the counter electrode substrate
30
, the color filter
31
, the protective film
33
, the counter electrode
34
, the alignment film
35
, the alignment film
20
, the TN liquid crystal
21
, and the alignment film
20
on the TFT substrate
10
. The light is reflected by the reflective display electrode
19
, travels through the layers in a direction opposite to the direction of incidence, emerges from the polarizer
41
on the counter electrode substrate
30
and enters the eyes of the observer
101
.
However, when, as indicated by broken line
102
, the incident natural light advances linearly and is reflected by the reflective display electrode
19
of the reflective material, the reflected light travels linearly and in parallel with the light
100
. Therefore, a part of the light
102
travelling linearly in parallel travels through a place not related with a display, such as the black matrix
32
of the color filter
31
.
Therefore, when the display is observed, the observed display in a specific viewing angle can be bright by the light having passed through a place other than the place not related with the display, but the entire observed image is disadvantageously dark. Moreover, as another disadvantage, an image blur, or a bleeding of a color image tends to be easily generated because the light of a pixel to be displayed is emitted from other pixels in the vicinity as shown in FIG.
1
.
SUMMARY OF THE INVENTION
The present invention has been made to rectify the disadvantages described above and has as its object to provide a reflection type liquid crystal display that enhances a luminance of each display pixel and offers a high-quality display.
According to one aspect of the present invention, there is provided a reflection type liquid crystal display, which comprises a liquid crystal held in a gap between a first substrate and a second substrate disposed facing each other, and electrodes for driving the liquid crystal for each pixel disposed on the first and second substrates facing the liquid crystal. The electrode on the first substrate comprises a plurality of reflective display electrodes divided for the pixels and formed of conductive reflective materials, and each of the plurality of reflective display electrodes has a concavity toward the first substrate on at least a surface facing the liquid crystal.
According to another aspect of the present invention, in the reflection type liquid crystal display, a switching element for each pixel is further formed on the first substrate, and the switching element is connected to the corresponding electrode out of the plurality of reflective display electrodes.
According to yet another aspect of the present invention, at least a surface of the reflective display electrode facing the liquid crystal is concaved toward the first substrate in the vicinity of a pixel area center.
As described above, since the reflective display electrode is provided with the concavity in each pixel area, the light reflected by the reflective display electrode is converged within the pixel area, so that the light is prevented from being propagated or lost through a light shield area other than the pixel area as an invalid light, or from being emitted from an adjacent pixel area. Therefore, the luminance of the reflected light obtained in each display pixel can substantially be enhanced. Moreover, since the reflected light is emitted from the same pixel area without leaking to adjacent pixels, image blur and the bleeding of a displayed color image can be prevented, so that a display quality can be enhanced.
Furthermore, in the present invention, the second substrate is provided with a light diffusing member, so that the light converged by the concavity of the reflective display electrode can be diffused and emitted. Therefore, the intensity of the emitted light can be uniformed in a single pixel, luminance nonuniformity is prevented and the display quality can further be enhanced.
In still another aspect of the present invention, the concavity of the reflective display electrode may also be obtained by the following constitution.
For example, in the device, at least an insulating film is formed between the reflective display electrode and the first substrate.
A concavity toward the first substrate is formed on the surface of the insulating film facing the liquid crystal for each of the pixel areas. The concavity of the insulating film is continued to the surface of the reflective display electrode facing the liquid crystal, formed on the insulating film.
Moreover, the switching element formed for each pixel and a wire for supplying a signal to the switching element are formed on the first substrate. The plurality of reflective display
Noritake Kazuto
Ogawa Shinji
Cantor & Colburn LLP
Chung David
Kim Robert H.
Sanyo Electric Co,. Ltd.
LandOfFree
Reflection type 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 Reflection type liquid crystal display, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reflection type liquid crystal display will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3082149