Liquid crystal cells – elements and systems – Particular structure – Particular illumination
Reexamination Certificate
2000-06-01
2003-02-04
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Particular illumination
C349S063000
Reexamination Certificate
active
06515722
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display for displaying information on a television system, on automobiles and on toys.
2. Description of the Related Art
Liquid crystal displays are classified into reflection type crystal displays, semitransparent type liquid crystal displays and transparent type liquid crystal displays.
A conventional reflection type liquid crystal display shown in
FIG. 8
has a liquid crystal cell
21
constructed by sealing a liquid crystal, not shown, between two rectangular insulating substrates
22
and
23
made of glass, and attaching polarizers
24
and
25
to the respective outer surfaces of the insulating substrates
22
and
23
, respectively. A reflecting film
26
of a transparent resin provided with a reflecting layer
26
a
of silver on one surface thereof is attached to the back surf ace of the liquid crystal cell
21
, and a protective film
27
of a plastic material is attached to the back surface of the reflecting film
26
.
External light falls on the front surface, i.e., the viewing-side surface, of the liquid crystal cell
21
, the external light is reflected by the reflecting film
26
to form a picture on the liquid crystal cell
21
. Accordingly, the visibility of the reflection type liquid crystal display is unsatisfactory in a dim environment because light of high intensity is unavailable in a dim environment.
A conventional semitransparent type liquid crystal display shown in
FIG. 9
has a liquid crystal cell
21
constructed by sealing a liquid crystal, not shown, between two rectangular insulating substrates
22
and
23
made of glass, and attaching polarizers
24
and
25
to the respective outer surfaces of the insulating substrates
22
and
23
, respectively. A reflecting film
28
of silver capable of transmitting and reflecting light is deposited by evaporation on the back surface of the lower polarizer
25
, and an electroluminescent panel (hereinafter referred to as “EL panel”)
29
serving as a light source is attached to the back surface of the reflecting film
28
.
When the semitransparent type liquid crystal display is used in good light, external light falls on the front surface, i.e., the viewing-side surface, of the liquid crystal cell
21
, the external light is reflected by the reflecting film
28
to form a picture on the liquid crystal cell
21
. When the semitransparent type liquid crystal display is used in a dim environment, the EL panel
29
is energized, light emitted by the EL panel
29
is transmitted by the reflecting film
28
to form a picture on the liquid crystal cell
21
. The light emitted by the EL panel
29
is attenuated while the same is transmitted by the reflecting film
28
. Consequently, the illuminating efficiency of the EL panel
29
to the liquid crystal cell
21
is low and satisfactory pictures cannot be displayed.
A conventional transparent type liquid crystal display shown in
FIG. 10
has a liquid crystal cell
21
constructed by sealing a liquid crystal, not shown, between two rectangular insulating substrates
22
and
23
of glass, and attaching polarizers
24
and
25
to the respective outer surfaces of the insulating substrates
22
and
23
, respectively. A light guide panel
30
of a transparent resin, such as a transparent acrylic resin, provided in one surface thereof with irregularities formed at pitches on the order of 300 &mgr;m is disposed on the back surface of the lower polarizer
25
with the surface provided with the irregularities in contact with the back surface of the lower polarizer
25
to guide light emitted by a light source
31
, such as a cold cathode discharge tube.
When displaying pictures on the liquid crystal display, the light source
31
is turned on, light emitted by the light source
31
is guided by the light guide panel
30
, the light is scattered by the irregularities of the light guide panel
30
into the liquid crystal cell
21
to form a picture on the liquid crystal cell
21
. Glaring light scattered by the light guide panel
30
falls directly on the eyes of the viewer, spoiling the quality of the picture. Since the pitches of the irregularities of the light guide panel
30
are as large as about 300 &mgr;m, the irregularities are visible and spoil the quality of pictures displayed on the liquid crystal display.
The visibility of the conventional reflection type liquid crystal display is unsatisfactory in a dim environment because bright light is unavailable in a dim environment. Light emitted by the EL panel
29
of the conventional semitransparent type liquid crystal display is attenuated by the reflecting film
29
and hence the EL panel
29
is unable to illuminate the liquid crystal cell
21
efficiently. Since glaring light scattered by the light guide panel
30
of the conventional transparent type liquid crystal display impinges directly on the eyes of the viewer, spoiling the quality of pictures and since the pitches of the irregularities of the light guide panel
30
are as large as about 300 &mgr;m, the irregularities are visible and spoil the quality of pictures displayed on the conventional transparent type liquid crystal display
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a liquid crystal display capable of clearly displaying pictures in sufficient brightness regardless of the ambient brightness and of preventing glare.
According to a first aspect of the present invention, a liquid crystal display comprises: a liquid crystal cell having a front surface serving as a viewing-side surface, and a back surface; a light guide panel having a first major surface provided with minute irregularities and a second major surface finished in a smooth flat plane, and disposed on the front surface of the liquid crystal cell with the second major surface thereof finished in a smooth flat plane in contact with the front surface of the liquid crystal cell; a light source formed of a cold cathod discharge tube and disposed near the light guide panel; and a reflecting film attached to the back surface of the liquid crystal cell.
The light source is disposed beside a side surface of the light guide panel, and the irregularities of the light guide panel are formed at a pitch in the range of 1 to 100 &mgr;m.
The irregularities may be ridges extended along lines substantially parallel to the side surface of the light guide panel and having a triangular cross section.
The irregularities may be a plurality of elliptic projections arranged along lines substantially parallel to the side surface of the light guide panel.
The elliptic projections may be arranged with their major axes extended along lines substantially parallel to the side surface of the light guide panel, and the length of the major axes of the elliptic projections may be in the range of 1 to 100 &mgr;m.
Flat surfaces may be formed between the adjacent ridges, respectively.
REFERENCES:
patent: 5040878 (1991-08-01), Eichenlaub
patent: 5473454 (1995-12-01), Blanchard
patent: 5608550 (1997-03-01), Epstein et al.
patent: 5671994 (1997-09-01), Tai et al.
patent: 5953089 (1999-09-01), Hiji et al.
patent: 6008871 (1999-12-01), Okumura
patent: 6104453 (2000-08-01), Watanabe
patent: 6104454 (2000-08-01), Hiyama et al.
patent: 2699853 (1997-09-01), None
Akkapeddi P. R.
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Sikes William L.
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