Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Screen other than for cathode-ray tube
Reexamination Certificate
1999-06-29
2001-06-05
McPherson, John A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Screen other than for cathode-ray tube
C430S200000, C430S945000
Reexamination Certificate
active
06242140
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for manufacturing a color filter, and more particularly, to a method for manufacturing a color filter of a liquid crystal display (LCD), by a thermal transfer method using a laser beam with modified energy distribution.
2. Description of the Related Art
A conventional color filter has the structure as shown in FIG.
1
. The conventional color filter includes black matrix layers
12
on a glass substrate
11
, red, blue and green color filter layers
13
a
,
13
b
and
13
c
formed among the black matrix layers
12
, and a protective layer
14
and a transparent electrode layer
15
sequentially formed on the black matrix layer
12
and the color filter layers
13
a
,
13
b
and
13
c.
The color filter is manufactured by a pigment dispersion method, a printing method or an electrodeposition method. According to the pigment dispersion method, the color filter is formed by coating, exposing, developing and sintering a pigment dispersed in a photosensitive resin. The above methods provide excellent accuracy and reproducibility, but manufacturing process is too long and complicated.
The color filter may also be manufactured by a printing method in which red, green and blue inks are coated on a printing board. However, the printing process has poor accuracy and reproducibility.
In the electrodeposition method, red, green and blue color filters are electrochemically formed on transparent electrodes. By this method, the planarity of the color filter is good, but color characteristics, such as purity, are deteriorated. To solve the above problems, a thermal transfer method has recently been proposed. U.S. Pat. Nos. 5,220,348, 5,256,506, 5,278,023 and 5,308,737 discloses a thermal transfer method. According to these disclosures, for the thermal transfer method, at least a light source, a transfer film and a substrate are required. The light emitted from the light source is absorbed by a light absorbent in the transfer film, and converted into heat energy. A material for forming a transfer layer of the transfer film is transferred onto a substrate by the heat energy, thereby resulting in a desired image. Also, U.S. Pat. No. 5,521,035 discloses that the thermal transfer method can be applied to the manufacture of a color filter for a LCD. In the manufacture of a color filter by the conventional methods, a laser beam having a shape like a Gaussian distribution, as shown in
FIG. 2
, is used as a light source for the transfer of a transfer layer.
U.S. Pat. No. 4,925,523 discloses the use of two or three laser beams having a shape like a Gaussian distribution so as to improve the etching depth and etching efficiency during etching of an organic material by a laser beam. In detail, an organic material is excited by a laser beam having a short wavelength and etched by adopting a laser beam having a long wavelength, wherein the size of two laser beams are similar to each other.
U.S. Pat. No. 5,018,805 discloses a laser printer using a plurality of lasers for a printing process, in which different laser beams are simultaneously irradiated onto different regions, not one region, in order to increase the printing speed.
In the thermal transfer method, the quality of transfer pattern depends on the energy distribution of a laser beam used for the transfer. In the case where a color filter is formed by the thermal transfer method as described above, using a laser having the Gaussian distribution as shown in
FIG. 2
, the laser generates a Gaussian beam
31
having a predetermined diameter as shown in
FIG. 3
, to scan an arbitrary color filter pattern
32
in the X direction for thermal transfer. In this way, the intensity of beams becomes weak at the edge of the pattern
32
, the quality of image formed on the edge is deteriorated compared to the image formed on the center of the pattern
32
. To solve these problems, the entire energy level throughout the pattern
32
can be strengthened, thereby improving the quality of an image at the edge of the pattern
32
. However, the energy level becomes excessive at the center of the Gaussian beams, thereby causing unevenness to a surface of the final color filter pattern.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for manufacturing a color filter having good surface roughness, in addition to being excellent in the formation of an image at the edge of a color filter pattern.
Accordingly, to achieve the above object, the present invention, as embodied and broadly defined herein, provides a method for manufacturing a color filter, comprising the steps of:
(a) forming a black matrix pattern on a substrate by photolithography;
(b) placing a transfer film having thermal color layers on the substrate;
(c) irradiating a laser beam with uniform energy distribution onto the transfer film to transfer the color layers onto the substrate; and
(d) curing the substrate onto which the color layer has been transferred, at 200~300° C.
Preferably, in the step
the laser beam is a complex laser beam formed of unit laser beams with different energy levels. The energy intensity of the unit laser beams located at the edges is higher than the energy intensity of the unit laser beam located at the center.
Also, the laser beam includes a plurality of unit laser beams having a high energy intensity at the edges, and a unit laser beam having a high energy intensity at the center.
According to another aspect of the invention, as embodied herein, a method for manufacturing a color filter, comprising the steps of:
(a) forming a black matrix pattern on a substrate by photolithography;
(b) placing a transfer film having thermal color layers on the substrate;
(c) irradiating a laser beam which dithers in a direction perpendicular to a transfer direction of the color layer, onto the transfer film to transfer the color layer onto the substrate; and
(d) curing the substrate onto which the color layer has been transferred, at 200~300° C.
Preferably, the laser beam has uniform energy distribution over the entire transfer film, or dithers such that the energy intensity is stronger at the edges than at the center, and the section of laser beam has an enlogated form in the transfer direction.
In the step @ the laser beam is a complex laser beam formed of unit laser beams with equal energy levels. Here, the unit laser beams dither with different phases.
The laser beam vibrates with a frequency of 100~1,000 kHz, having a width of 50~150 &mgr;m.
In a method of color filter according to the present invention, a transparent electrode is formed on the red, green and blue color filter layers. Here, the thickness of the transparent electrode layer is 800~4000 Å and the sheet resistance thereof is 2~100 &OHgr;/□.
It is also preferable that after the red, green and blue color filter layers are formed on the substrate, the buffer layer is formed to a thickness of dozens through hundreds of Å to increase adhesion between the color filter layer and the transparent electrode layer, before the transparent electrode layer is formed. The buffer layer is formed of SiO
2
or a silicon nitride (SiN
x
).
Preferably, a protective layer is formed on the substrate where the black matrix layer and the red, green and blue color filter layers are formed, to increase planarity. More preferably, an SiO
2
layer acting as a buffer layer is further formed on the protective layer to a thickness of dozens through hundreds of A.
Also, preferably, a surface of the substrate is treated with UV rays and/or O
3
or a surfactant, before and after forming the black matrix layer, the color filter layer, the transparent electrode layer and the buffer (SiO
2
) layer.
REFERENCES:
patent: 5482803 (1996-01-01), Ishiwata et al.
patent: 5521035 (1996-05-01), Wolk et al.
patent: 41725 (1992-01-01), None
patent: 477717 (1992-03-01), None
patent: 4-100005 (1992-04-01), None
patent: 5-53008 (1993-03-01), None
patent: 6265720 (1994-09-01), None
patent: 6242311 (1994-09-01), None
p
Choi Kyu-Hwan
Choi Young-sook
Kang Tae-min
Kim Lee-gon
Kwon Jang-hyuk
Leydig , Voit & Mayer, Ltd.
McPherson John A.
Samsung SDI & Co., Ltd.
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