Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1999-04-07
2001-02-06
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S155000
Reexamination Certificate
active
06184956
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) and, more particularly, to a reflective plate used in the LCD and a method for making the same.
2. Description of the Prior Art
Liquid crystal display (LCD) devices have recently undergone development to enable increases in size and improvements in definition while decreasing power dissipation. For these and other reasons, the LCD device has a most promising future.
Generally, there are two basic types of LCDs: a light transmissive type and a light reflective type.
The light transmissive LCD comprises a backlight disposed on a rear side of a liquid crystal cell. The light radiated from the backlight selectively passes through a liquid crystal, thereby realizing desired images.
The light reflective LCD comprises a reflective plate disposed on a rear side of the liquid crystal cell so as to reflect incident light toward the front side of the LCD cell, thereby realizing desired images.
The present invention is directed to the light reflective LCD, which will be referred to as a “reflective LCD.”
FIG. 1
shows a conventional reflective LCD.
The conventional reflective LCD comprises upper and lower substrates
2
and
4
. ITO electrode patterns
10
and
10
′ are disposed on opposing inner surfaces of the upper and lower substrates
2
and
4
, respectively. Insulating layers
12
and
12
′ and orientation layers
14
and
14
′ are disposed on the ITO electrode patterns
10
and
10
′, respectively. Disposed between the lower substrate
4
and the ITO electrode pattern
10
′ are a reflective layer
6
and a first diffuser layer
8
. Disposed between the orientation layers
14
and
14
′ is a liquid crystal layer
16
.
A polarizer layer
18
and a second diffuser layer
20
are in this order disposed on an outer surface of the upper substrate
2
. A retardation film may be further disposed on the outer or inner surface of the upper substrate
2
in case of an STN-LCD.
In the above described reflective LCD, only 50% of outer light introduced into the LCD as linear polarization by the polarizer layer
18
can be used to display an image. That is, the conventional reflective LCD has a drawback of a low light efficiency.
To solve the above drawback, Japanese laid-open Patents No. 92-243226 and 97-258219 disclose reflective LCDs having a reflective plate which can improve light efficiency. The reflective plate is shown in FIG.
2
and is designated by the reference numeral
64
.
The reflective plate
64
comprises a substrate
40
, an unevenly-surfaced layer
60
formed on the substrate
40
, and a reflective layer
62
deposited on and unevenly-surfaced by the unevenly-surfaced layer
60
. To form the unevenly surfaced layer
60
, a photoresist resin layer is first deposited on the substrate
40
, then patterned using a photo-mask, thereby obtaining an uneven surface. The photoresist pattern is hardened through a heat-treatment process, then the reflective layer
62
is deposited on the substrate to cover the photoresist pattern.
However, in the reflective plate
64
, since the uneven surface of the reflective layer is formed in a uniform pattern as the same is formed through the photo-etching process, luminance may deteriorate by an interference of reflecting light.
In addition, to form the photosensitive pattern, additional devices such as a light exposure system and a mask, and additional processes such as an etching process are required. This increases manufacturing costs and complicates the manufacturing process.
SUMMARY OF THE INVENTION
The present invention has been made in an effort to solve the above-described problems of the prior art.
It is a first objective of the present invention to provide a reflective plate for an LCD in which a reflective layer is unevenly non-uniformly surfaced to prevent the interference of reflecting light.
It is a second objective of the present invention to provide a method for making a reflective plate in which the reflective plate can be easily made without using a photo-masking device.
To achieve the first objective, the present invention provides a reflective plate used in a reflective LCD, which comprises a base substrate, a plurality of spacer cores dispersed on the base substrate, an adhesive disposed on the base substrate to attach the spacer cores on the base substrate, a combination of the spacer cores and the adhesive defining an unevenly non-uniformly surfaced layer, and a reflective layer deposited on the unevenly non-uniformly surfaced layer.
According to an embodiment of the present invention, the adhesive is deposited around the spacer cores, then molten by heat to attach the spacer cores on the base substrate. The spacer cores are made of silica or plastic.
According to another embodiment of the present invention, the spacer cores may be made of a same material with the adhesive. Preferably, the material may be a thermosetting resin.
Preferably, each of the spacer cores is spherical having a diameter of about 1-10 &mgr;m. The spacer cores are randomly dispersed on the base substrate.
According to still another embodiment of the present invention, the reflective plate may further comprises a roughness adjusting layer disposed between the unevenly non-uniformly surfaced layer and the reflective layer.
According to the present invention, a surface roughness (k) of the reflective plate is 6-10 degree when the surface roughness (k) is defined by a following formula;
k
=
1
L
∫
0
L
α
2
ⅆ
x
where, the L is a surface length of the substrate and &agr; is a mean angle of surface inclination.
According to another aspect, the present invention provides a method for making a reflective plate used in an LCD, comprising the steps of preparing a base substrate, dispersing a plurality of spacers on the base substrate to form an uneven layer on the substrate, and depositing a reflective layer on the base substrate to cover the spacers.
According to still another aspect, the present invention provides a method for making a reflective plate used in an LCD, comprising the steps of pre-heating a lump of thermosetting resin, grinding the thermosetting resin into a powder, mixing the powder with pure water or isopropyl alcohol, spraying the mixture on a substrate in a randomly scattered pattern, heating the sprayed mixture at a temperature higher than that for the preheating, melting the mixture, and hardening the mixture so that an unevenly non-uniformly surfaced layer formed on the substrate.
REFERENCES:
patent: 4104102 (1978-08-01), Eagon et al.
patent: 4401494 (1983-08-01), Pernicano et al.
patent: 5207852 (1993-05-01), Lightle et al.
patent: 5917567 (1999-06-01), Oh et al.
patent: 1-120530 (1989-05-01), None
Choi Young-Il
Kang Seung-Gon
Kim Byung-hee
Kim Sun-Hwa
Shin Hyun-Eok
Baker & McKenzie
Nguyen Dung
Samsung Display Devices Co. Ltd.
Sikes William L.
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