Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-06-14
2003-12-23
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S098000, C349S176000, C349S185000, C349S194000
Reexamination Certificate
active
06667788
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a liquid crystal display and, more particularly, to a method for producing an image on a liquid crystal panel, the liquid crystal panel and a liquid crystal display equipped with the liquid crystal panel.
DESCRIPTION OF THE RELATED ART
A typical example of the liquid crystal display is shown in
FIG. 1
of the drawings. The prior art liquid crystal display is broken down into a liquid crystal panel, a pair of polarizing plates
201
/
208
and a back light source
209
. The liquid crystal panel is sandwiched between the polarizing plates
201
and
208
, and light is radiated from the back light source
209
through the polarizing plate
208
to the liquid crystal panel.
The liquid crystal panel includes a pair of glass substrates
202
and
207
and liquid crystal
205
filling the gap between the glass substrates
202
and
207
. Color filter elements
203
R,
203
G and
203
B are arranged on the inner surface of the glass substrate
202
, and the color filter elements
203
R/
203
G/
203
B are covered with a common electrode
204
. On the other hand, segment electrodes
206
are arrayed on the inner surface of the other glass substrate
207
, and the segment electrodes
206
are aligned with the color filter elements
203
R/
203
G/
203
B. The color filter elements
203
R,
203
G and
203
B respectively transmit wavelengths recognized as red, wavelengths recognized as green and wavelengths recognized as blue therethrough, and a set of color filter elements
203
R,
203
G and
203
B is associated with a pixel.
The color filters
203
R/
203
G/
203
B and the common electrode
204
are formed on the inner surface of the glass substrate
202
, and the segment electrodes
206
are formed on the inner surface of the other glass substrate
207
. The glass substrates
201
and
207
are assembled together, and the liquid crystal
205
is injected into the gal between the glass substrates
202
and
207
.
When a potential difference is applied between the common electrode
204
and selected segment electrodes
206
, the liquid crystal changes the orientation of the liquid crystal molecules between the selected segment electrodes
206
and the color filter elements
203
R/
203
G/
203
B. The back light source
209
radiates light toward the liquid crystal panel, and the liquid crystal molecules between the selected segment electrodes
206
and the common electrode
204
allow the light to pass therethrough. Thus, the light components are incident onto the color filter elements
203
R/
203
G/
203
B. The color filter elements
203
R/
203
G/
203
B absorb particular wavelengths of the incident light components, and transmits other wavelengths of the incident light components to the outside of the liquid crystal panel. The transmitted light components produce a color image on the liquid crystal panel.
A problem is encountered in the prior art liquid crystal display in a low transmittance of the light and a low production yield. The low transmittance is derived from the absorption of the incident light components. Each color filter element
203
R/
203
G/
203
B absorbs two third of the incident light components, and only a third of the incident light components participates the production of the color image. The utilization factor of the Incident light is low. This is the first problem inherent in the prior art liquid crystal display. The low production yield is due to misalignment between the segment electrodes
206
and the color filter elements
203
R/
203
G/
203
B. Even if the misalignment is not serious, the color image is not sharp.
The first problem may be solved by using a cholesteric filter disclosed in Japanese Patent Publication of Unexamined Application No. 8-234196.
FIG. 2
illustrates the prior art cholesteric filter disclosed in the Japanese Patent Publication of Unexamined Application.
A light source
10
is encircled with a reflecting mirror
12
, and a circularly polarizing plate
16
is provided between the light source
10
and the prior art cholesteric filter
18
. The light source
10
generates the natural light, and the reflecting mirror
12
directs the natural light toward the circularly polarized plate
16
. The light source
10
, the reflecting mirror
12
and the circularly polarized plate
16
as a whole constitute a polarized light source. The polarized light source radiates circularly polarized light, which is polarized in a particular direction, toward the prior art cholesteric filter
18
.
The prior art cholesteric filter
18
transmits the circularly polarized light of a particular waveband, but the circularly polarized light of the other waveband is reflected thereon. The prior art cholesteric filter
18
consists of two filter layers
20
and
22
, and the filter layers
20
/
22
are divided into sections R, G and B. The sections R transmit wavelength components recognized as green and blue, and reflects the wavelength components recognized as red. The sections G transmit wavelength components recognized as red and blue, and reflect other the wavelength components recognized as green. The sections B transmit wavelength components recognized as red and green, and reflect the other wavelength components recognized as blue. The sections R/G/B of the filter layer
20
are offset from the sections R/G/B of the other filter layer
22
. If the section B is overlapped with the section R, the part of the cholesteric filter
18
transmits the wavelength components recognized as green. Similarly, the wavelength components recognized as blue pass the section R overlapped with the section G, and the wavelength components recognized as red pass the section G overlapped with the section B. Two third of the incident light is previously reflected toward the circularly polarized light source, and is reused. For this reason, the utilization factor is increased.
When the cholesteric filter
18
is applied to a liquid crystal display, the cholesteric filter is inserted between the substrates. Noise component of the transmitted light component is absorbed by using a color filter.
However, the second problem is also encountered in a liquid crystal display equipped with the prior art cholesteric filter due to the misalignment between the pixels, the sections R/G/B of the cholesteric filter and the color filter during the assembling work. Even if the misalignment is not serious, the color image is not sharp.
SUMMARY OF THE INVENTION
It is therefore an important object of the present invention to provide a method for producing a clear color image on a liquid crystal display.
It is also an important object of the present invention to provide a liquid crystal panel, which is fabricated at a high yield.
It is also an important object of the present invention to provide a liquid crystal display, which is equipped with the liquid crystal panel for producing a sharp color image through the method.
To accomplish the object, the present invention proposes to recycle circularly polarized light components reflected on a cholesteric filter.
In accordance with one aspect of the present invention, there is provided a method for producing a visual image on a liquid crystal display comprising the steps of radiating an incident light, selecting one of the right-handed circularly polarized light component and the left-handed circularly polarized light component of a waveband from the incident light so as to recycle the other of the right-handed circularly polarized light component and the left-handed circularly polarized light component of the waveband and other light components of other wavebands of the incident light as a part of the incident light, converting the aforesaid one of the right-handed circularly polarized light component and the left-handed circularly polarized light component to a linearly polarized light component, removing a noise component of the other wavebands from the linearly polarized light component, if any, and producing a visual image from the linearly polarized light component by changing an orientation of liquid crystal mo
Fujimaki Eriko
Maruyama Muneo
NEC LCD Technologies Ltd.
Nguyen Hoan
LandOfFree
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