WO2003052502A1

WO2003052502A1 - A manufacturing method of liquid crystal display

Info

Publication number: WO2003052502A1
Application number: PCT/KR2002/000271
Authority: WO
Inventors: Young-Mi Tak; Woon-Yong Park
Original assignee: Samsung Electronics Co., Ltd.
Priority date: 2001-12-14
Filing date: 2002-02-20
Publication date: 2003-06-26
Also published as: AU2002233812A1; KR100853214B1; KR20030051142A

Abstract

In a method of manufacturing a liquid crystal display panel using a divided exposure, an overlapping area in the boundary between adjoining shots is formed and the area of the shots is exposed in a way to gradually decrease and increase to the left and right of the boundary to reduce the difference of brightness occurred due to stitch errors between the two shots. For example, the number of unit stitches assigned to the left shot gradually decreases and the number of unit stitches assigned to the right shot gradually increases as going toward the right along the horizontal direction in the overlapping area. At this time, one of small domains, which are divided from a pixel into at least two is used as a unit stitch.

Description

A MANUFACTURING METHOD OF LIQUID CRYSTAL DISPLAY

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a method of manufacturing a liquid crystal display (LCD), more in detail, to a method of manufacturing a liquid crystal display to reduce the difference of brightness due to the stitch error occurred when a substrate of the LCD is formed with the process of divided exposure.

(b) Description of the Related Art

Generally, in case that the active area of a liquid crystal display panel is larger than the size of an exposure mask, a divided exposure, in which the active area is divided into at least two domains and step-and-repeat process

is conducted for the individual domains, is needed form patterns in the active area. That is, the active area needs to be exposed by more than two shots. In this case, since real shots are shifted, rotated and/or distorted,

misalignment between the shots occurs (referred to as 'stitch error'

hereinafter). Because of the misalignment, either the difference of parasitic

capacities between wires and pixel electrodes located near the boundary

between the shots or change of the locations of the patterns are caused.

Since the difference of parasitic capacities and that of the locations of

the patterns respectively result in the difference of electric characteristics

and that of the aperture ratio between the domains of the LCD panel, the difference of the brightness of the display near the boundary between the shots occurs.

Fig. 1 is a plan view showing the boundary between shots of a conventional LCD panel. As shown in Fig. 1 , since there is a sudden change of brightness between shot A and shot B near the boundary of the shots due to the stitch error occurred between the adjoining shots A and B, a streak is observed in the boundary area of the shots.

To reduce the difference of brightness, in a conventional method of manufacturing an LCD, shots are set to have saw-shaped boundary as shown in Fig. 2. A plan view of two adjoining shots set in this way is shown in

Fig. 2, and an exposure area and brightness are respectively shown in Fig.

8b and Fig. 9b. Although the difference of brightness between the shots changes less sudden in the boundary area between the shots in Fig. 9b than in Fig. 8b, the streak is still visible with the naked eyes. Moreover, a mosaic pattern may be observed if a unit stitch is large enough.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method of manufacturing a panel for a liquid crystal display (LCD) in which the difference of brightness between shots due to a stitch error gradually changes when observed with the naked eyes.

To achieve the above object, overlapping area is formed in the boundary of shots (referred to as a 'stitch area' hereinafter) in the process of

divided exposure, and exposed in the way that the exposure area of the left and right shots gradually increases or decreases, respectively, as moved in the horizontal direction in the stitch area. At this time, a pixel is divided into more than two domains to be used as a unit stitch.

In summary, it is possible to gradually change brightness in the boundary between the shots by gradually changing the exposure area assigned to shots of either sides of the boundary in the area near the boundary. Finally, there does not appear a distinctive boundary line between the shots.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or the similar component, wherein:

Fig. 1 and Fig. 2 are plan views showing two adjoining shots of the conventional liquid crystal display;

Fig. 3 is a plan view showing shots A and B of a liquid crystal display according to a first and a second preferred embodiment of the present invention;

Fig. 4 is a plan view showing a boundary area of shots of a liquid crystal display according to a first preferred embodiment of the present invention;

Fig. 5 is a plan view showing unit stitches of a liquid crystal display according to a first preferred embodiment of the present invention; Fig. 6 is a plan view showing the boundary area of shots of a liquid crystal display according to a second preferred embodiment of the present invention;

Fig. 7 is a plan view showing unit stitches of a liquid crystal display according to a second preferred embodiment of the present invention; Figs. 8a and 8b illustrate the exposure area assigned to shot A and shot B near the boundary area between the shots according to the conventional liquid crystal display;

Fig. 8c illustrates the exposure area assigned to shot A and shot B near the boundary area between the shots according to a first and a second preferred embodiment of the present invention;

Figs. 9a and 9b illustrate the difference of brightness between the shorts of the conventional liquid crystal display; and

Fig. 9c illustrates the difference of brightness between the shorts according to a first and a second preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Fig. 3 is a plan view showing adjoining shots of a liquid crystal display

panel according to preferred embodiments of the present invention.

Fig. 4 is a plan view showing a boundary area of shots of an LCD

panel according to a first preferred embodiment of the present invention;

Fig. 5 is a plan view showing unit stitches of a liquid crystal display

according to a first preferred embodiment of the present invention;

As shown in Fig. 4, a stitch area, which is an overlap between two adjoining shots, for example, left shot A (shown as white portion) and right shot B (shown as black portion), is comprised of a plural number of unit

stitches, for example, 10 X 9 number of unit stitches. The unit stitch refers to one portion as a basic unit in case that the stitch area is divided into n X m number of portions (n and m are natural numbers).

A first preferred embodiment according to the present invention uses

one of small portions, which are divided from a pixel into two or more, as a unit stitch. By reducing the size of the unit stitch, it is possible to prevent a

mosaic pattern from occurring. As shown in Fig. 5, a pixel is divided into two portions A and B, each of which is used as a unit stitch, in a first preferred

embodiment of the present invention.

The unit stitch of a first preferred embodiment of this invention will be

explained more in detail with reference to Fig. 5.

As shown in Fig. 5, a pixel is defined by intersections of gate lines 20

and data lines 70 formed on a thin film transistor panel in the horizontal direction and in the vertical direction, respectively. A pixel electrode 90, which includes a thin film transistor and apertures 901 , 903, 905, 907, 909, 91 1 , and 913, is formed in the pixel. A common electrode (not shown), on which apertures 401 , 403, 405, 407, 409, 41 1 , and 413 are patterned, is formed on a color filter panel (not shown), which opposes to the thin film transistor panel. The apertures 401 , 403, 405, 407, 41 1 , and 413 formed on the common electrode are illustrated with a dotted pattern. The apertures 901 , 903, 905, 907, 909, 91 1 , and 913 of the pixel electrode 90 and the apertures 401 , 403, 405, 407, 411 , and 413 of the common electrode are aligned in turns and divide the pixel area into a plural number of small domains. At this time, arrangement of the apertures in portion a and the apertures in portion b is symmetrical, and the boundary of the portions a and b is defined by the aperture 407 of the common electrode.

In the first preferred embodiment of this invention, it is possible to expose the- portion a with shot A and the portion b with shot B using the portions a and b, which are divisions of a pixel, as unit stitches. This method prevents a display stain such as mosaic pattern since it is possible to lower the difference of brightness more with delicacy than does the method in which a whole pixel is used as the unit stitch. In addition, since the aperture 407 is arranged in the boundary between the unit stitches, it is possible to shield the boundary line between shots which may appear even dimly due to the difference of brightness between the unit stitches.

A method of manufacturing an LCD panel to reduce stitch errors will be described with reference to Fig. 4.

According to the first preferred embodiment of this invention, in the stitch area, the number of unit stitches of shot A exposure gradually decreases and the number of unit stitches of shot B exposure gradually increases as going toward the right side along the horizontal direction. Therefore, brightness in the stitch area continuously changes. Here, the unit stitches of any shot exposure refer to the unit stitches that are exposed by the shot.

For example, in case that a stitch area is comprised of 9 columns of unit stitches and 10 rows of unit stitches, 9 exposure unit stitches of the shot A and 1 exposure unit stitch of the shot B are assigned to the first column, 8 exposure unit stitches of the shot A and 2 exposure unit stitches of the shot B to the second column, 7 exposure unit stitches of the shot A and 3 exposure unit stitches of the shot B to the third column, and so on. At this , time, the unit stitches of the shot A and the shot B is desired to be assigned in the way. that the unit stitches of the same kind shot are not gathered. It is because there may be a display stain, when taking a broad view of it, if the unit stitches of the same kind shot are gathered.

As exemplified above, the number of unit stitches of the shot A gradually decreases and the number of unit stitches of the shot B gradually increases along the horizontal direction.

Fig. 8c illustrates an exposure area for shot A, a stitch area, and a exposure area for shot B formed in the horizontal direction. As shown in Fig. 8c, since the number of unit stitches of the shot A and that of the shot B decreases and increases, respectively, along the horizontal direction in the first preferred embodiment of the present invention, the difference of brightness between the shots A and B gradually changes. Fig. 9c illustrates the difference of brightness between adjoining shorts and a stitch area of an LCD panel according to a first preferred embodiment of the present invention.

The horizontal axis of Fig. 9c indicates shot A, a stitch area, and shot B in an increasing direction, and the vertical axis of Fig. 9c indicates brightness. In this graph, which shows the change of brightness in the stitch area in case that the shot A is brighter than the shot B, the stitch area becomes gradually darker as going from A portion to B portion.

Meanwhile, Fig. 6 is a plan view showing the boundary area of shots ^"of a liquid crystal display according to a second preferred embodiment of the ' , present invention, and Fig. 7 is a plan view showing unit stitches of a liquid crystal display according to a second preferred embodiment of the present invention.

As shown in Fig. 6, the second preferred embodiment of the present invention is a method for forming shots in the way that the exposure area of the shot A in each unit stitch gradually decreases in the stitch area as going to the right columns along the horizontal direction and the exposure area of the shot B in each unit stitch gradually increases in the stitch area as going to the right columns. As a result, the brightness in the stitch area gradually changes.

For example, in case that the stitch area is comprised of 9 columns of

unit stitches and 10 rows of unit stitches, the first column of each unit stitch

of the shot A and each those of the shot B are exposed at 90 % and 10%

respectively, the second column of each unit stitch of the shot A and those of the shot B are exposed at 80% and 20% respectively, the third column of

each unit stitch of the shot A and those of the shot B are exposed at 70%

and 30% respectively, and so on.

As this, the exposure area of the unit stitches of the shot A gradually

decreases and the exposure area of the unit stitches of the shot B gradually increase in the stitch area along the horizontal direction. By assigning as this,

the brightness between the unit stitches of the shot A and unit stitches of shot B gradually changes along the horizontal direction.

A second preferred embodiment according to the present invention

uses one of small portions, which are divided from a pixel into two or more, as a unit stitch. By reducing the size of the unit stitch, it is possible to prevent a mosaic pattern from occurring. As shown in Fig. 7, a pixel is divided into

four portions a, b, c, and d, each of which is used as a unit stitch, in a second

preferred embodiment of the present invention. Hereinafter, the unit stitches according to the second preferred

embodiment of the present invention will be explained more in detail with

reference to Fig. 7.

As shown in Fig. 7, a pixel is defined by intersections of gate lines 20 and data lines 70 formed on a thin film transistor panel in the horizontal direction and in the vertical direction, respectively. A pixel electrode 90, which includes a thin film transistor and apertures 901 , 903, 905, 907, 909, 91 1 , and 913, is formed in the pixel. A common electrode (not shown), on which apertures 401 , 403, 405, 407, 409, 411 , and 413 are patterned, is formed on a color filter panel (not shown), which opposes to the thin film transistor panel. The apertures 401 , 403, 405, 407, 411 , and 413 formed on the common electrode are illustrated with a dotted pattern. The apertures 901 , 903, 905, 907, 909, 91 1 , and 913 of the pixel electrode 90 and the apertures 401 , 403, 405, 407, 41 1 , and 413 of the common electrode are aligned in turns and divide the pixel area into a plural of small domains. At this time, the arrangement of the apertures in the portion a and the portion b is symmetrical from the boundary of the two portions as a central line, and the arrangement of the apertures in the portion c and the portion c is also symmetrical from the boundary of the two portions. At this time, the boundaries between the portions a, b, c, and d are formed by apertures 401 , 403, 405, 407, 409, 411 , 413, 901 , 903, 905, 907, 909, and 911 of the pixel electrode and the common electrode. In the above, although apertures were exemplified as a domain dividing measure, protrudes or concave pattern can be used to divide a pixel into a plural number of domains.

In the second preferred embodiment of this invention, it is possible to expose portions a, b, c, and d with different shots using a unit stitch. For example, a pair of shots A: B includes a: b, c, & d; a & b: c & d; a, b, & c: d; and a & d: b & c. By doing this, a display stain such as a mosaic pattern can be prevented since it is possible to lower the difference of brightness more with delicacy than does the method in which a whole pixel is used as a unit stitch. In addition, since the apertures 401 , 403, 405, 407, 409, 411 , 413, 901 , 903, 905, 907, 909, 91 1 are arranged in the boundary between the unit stitches, it is possible to shield the boundary line between shots which may appear even dimly due to the difference of brightness between the unit stitches.

The exposure area and the change of brightness between the adjoining shots according to the second preferred embodiment of this invention are illustrated in Fig. 8c and Fig. 9c, respectively. Description of Fig. 8c and Fig. 9c according to the second preferred embodiment are the same as that according to the first preferred embodiment.

Meanwhile, a plural number of photolithography process, that is a plural number of exposures for a plural layers, is needed to form wires, pixel electrodes, and switching devices of a liquid crystal display, especially an active matrix liquid crystal display (AMLCD). In this case, it is needed to align the stitch area and the unit stitch in the exposure process of the plural layers to gradually change brightness with accuracy. It is also possible way to differ either the stitch area or the unit stitches, or to form stitches with linear or saw-shaped boundary for any specific layers.

As described above, it is possible to reduce the difference of brightness due to stitch errors occurring on an LCD panel by gradually changing the exposure area between the right and left shots in the process of divided exposure of the LCD panel.

Claims

WHAT IS CLAIMED IS:

1. A manufacturing method of a liquid crystal display, comprising the steps of: conducting a divided exposure process in an active area with a plural number of shots including a first shot and a second shot that are adjoining, wherein a stitch area, which is overlapping area of the first shot and the second shot, is formed in a boundary between the first shot and the second shot , an area for the first shot gradually decreases and an area for the second shot gradually increases in the stitch area along the direction going from the first shot to the second shot, and small portions are divided from a pixel into at least two and each of the portions is used as a unit for the increase of the area for the first shot and the decrease of the area for the second shot.

2. The method of claim 1 wherein a domain dividing measure is formed in the pixel and the domain dividing measure is located in a boundary, which is included in the pixel, between the small portions.