Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-03-21
2004-08-31
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S063000
Reexamination Certificate
active
06784958
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display (LCD), and more specifically to an illumination method of removing moire phenomenon in a reflective type LCD assembly that minimizes moire phenomena and light leakage, which are frequently generated in the reflective type LCD assembly, without display performance degradation, and a reflective type LCD assembly using the same. A light supply unit for assembly, and a method of fabricating a light distribution alteration unit thereof are also disclosed.
2. Description of the Related Art
Generally, an LCD is one kind of flat panel displays precisely. LCD controls an electro-optical property of liquid crystal to display an image and converts image data of electric signals to a picture that a user can recognize.
In order to perform an improved display operation through the LCD, it is very important to control both material characteristic and optical characteristic of the liquid crystal. However, in view of the fact that the liquid crystal is a light receiving device, it is also very important to efficiently use a light source which is supplied to the liquid crystal.
In case there is not provided the light source, or the light source is not efficiently used, even the precisely controlled liquid crystal of the LCD cannot allow the user to recognize any data through the LCD.
According to the use of the light source, LCDs are classified into a reflective type LCD in which the display operation is performed using an external light source, and a backlight LCD in which light is generated using its own charged energy and the display operation is performed using the light.
The reflective type LCD that displays images using only the light from the external light source consumes much less power compared to the backlight LCD. However, without external light source, the user cannot recognize the display.
This is a fatal disadvantage in a display device if the device cannot operate in any conditions or environments.
To solve the problem, there has been provided an improved reflective type LCD assembly that, if the light is insufficiently supplied from the external light, generates additional lights to normally perform the display operation, thereby having advantages of both the reflective type LCD and the backlight LCD.
In order to achieve an improved reflective type LCD assembly
100
, as shown in
FIGS. 1 and 2
, an LCD
10
in which the liquid crystal is controlled to adjust an optical transmittance and a light supply unit
20
that supplies the light to the LCD
10
with small power consumption are necessary.
At this time, the light supply unit
20
has a light source
21
and first and second optical members
25
and
27
for uniformly supplying the light generated from the light source
21
to the LCD
10
.
More particularly, a point light source type of light emitting diode (LED) with a power consumption of only a few to a few tens mW is mostly served as the light source
21
.
By using the point light source type LED, the power consumption can be remarkably reduced.
However, if the LED is directly applied to a desired portion of the LCD
10
, some parts of the LCD
10
, which are near to the LED, are bright, but other parts, which are far from the point light source, are dark. In other words, the luminance difference in a display screen degrades the display performance of the LCD.
In order to cure the non-uniform luminance problem of the LED as described above, the first optical member
25
and the second optical member
27
are necessary to indirectly transform the light generated from the point light source type LED into the planar light.
The first optical member
25
and the second optical member
27
transform the light from the point light source type LED into the linear light, and then the linear light into the planar light.
Particularly, the first optical member
27
has a desired length to transform the point light source into the linear light source type. The first optical member
27
is formed into a square rod, and provided with the point light source at an end thereof.
As shown in
FIG. 1
, the first optical member
27
irradiates the light in an angle of 2.
The linear light source formed by the first optical member
27
should be transformed into the planar light source. However, in order to achieve the planar light source, a complicated optical mechanism is required.
As shown in
FIGS. 1 and 2
, the light irradiated from the first optical member
27
, which has a light distribution in the linear light source, is transferred to the second optical member
25
in the form of a square plate. On an upper portion of the second optical member
25
, there is formed a sawtooth-shape light reflective pattern
25
a.
At this time, the light coming from the first optical member
27
is uniformly transferred from a front portion
25
b
of the light reflective pattern
25
a
, which is adjacent to the first optical member
27
, to a rear portion
25
c
of the light reflective pattern
25
a.
Therefore, the light irradiated from the first optical member
27
is transformed into the light having the light distribution in the planar light source.
The planar light transformed by the second optical member
25
is then incident onto the reflective type LCD
10
.
Then, the incident light on the reflective type LCD
10
is reflected by a reflective electrode
15
which is formed in the reflective type LCD
10
in the form of a matrix, and is passed again through the second optical member
25
, and is then incident on user's eyes so that the user can visually recognize desired information.
The improved reflective type LCD assembly
100
can display images even in a dark place.
The light reflective pattern
25
a
that provides planar light source, overlaps with the reflective electrode
15
formed in the LCD
10
. If two patterns are overlapped each other as described above, a moire pattern may be generated, degrading the display performance.
To solve the problem, an aligning angle between the light reflective pattern
25
a
and the reflective electrode
15
has been changed to avoid parallel alignment of each other but to form a cross alignment.
At this time, when the aligning angle between the light reflective pattern
25
a
and the reflective electrode
15
is about 22.5°, as shown in
FIG. 2
, the moire phenomenon is the least generated.
However, even though the light reflective pattern
25
a
and the reflective electrode
15
are aligned to cross each other, narrower pitches of the light reflective pattern
25
a
and the reflective electrode
15
may generate the moire phenomenon again.
To this end, the moire phenomenon is not a problem in a conventional mid and small-sized LCD having low resolution. However, in a large-sized LCD, the narrow pitches of the light reflective pattern
25
a
and the reflective electrode
15
generate the moire phenomenon again.
Further, if the light reflective pattern
25
a
and the reflective electrode
15
are tilted at a desired angle, e.g., 22.5°, only a half of the light reflected by the light reflective pattern
25
a
goes to the reflective electrode
15
, and the rest of the light goes to an undesired place by the tilted light reflective pattern
25
a
. Therefore, there is another problem that an entire luminance of the reflective type LCD assembly is lowered, and a power consumption of the assembly is thus increased.
Recently, to solve the problem, it was attempted to conform the pitch of the light reflective pattern
25
a
to the pitch of the reflective electrode
15
, thereby reducing the moire.
However, if the pitch of the reflective electrode
15
changes, the light reflective pattern
25
a
should be re-fabricated. Further, if the light reflective pattern
25
a
and the reflective electrode
15
do not align correctly, it creates the moire again, and lowers the display. In this case, the power consumption also increases because of the low luminance.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a
Chung David Y.
McGuireWoods LLP
Samsung Electronics Co,. Ltd.
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