JPH0651321A - Production of liquid crystal panel - Google Patents

Abstract

PURPOSE:To ameliorate the unequal orientation of an active matrix type liquid crystal panel by setting the implantation direction of a liquid crystal at the same bearing. CONSTITUTION:The liquid crystal panel is constituted of a driving substrate 1 which is integrated and formed with thin-film transistors as liquid crystal driving elements and a counter substrate 2 which has a counter electrode and is disposed to face this driving substrate 1 via a sealing material 3. The implantation direction DL is so set as to be the same bearing as the orientation direction DR1 of the driving substrate 1 at the time of injecting the liquid crystal 6 into the liquid crystal panel having such constitution. As a result, the damaging of the orientability of the driving substrate 1 is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal panel. More specifically, the present invention relates to a method of injecting liquid crystal into an active matrix type panel in which thin film transistors and pixel electrodes are integrally formed.

[0002]

2. Description of the Related Art In order to clarify the background of the present invention, first, a general structure of an active matrix type liquid crystal panel will be briefly described with reference to FIG. Liquid crystal 103 is injected and sealed between the drive substrate 101 and the counter substrate 102, which are bonded to each other with a predetermined gap. Drive substrate 101
The scanning lines 104 and the signal lines 10 orthogonal to each other are formed on the inner surface of the
5 are provided. Pixel electrodes 106 and thin film transistors (TFTs) 107 are arranged in a matrix at each intersection. Further, although not shown, an alignment film that has been subjected to a rubbing treatment is also formed on the inner surface of the drive substrate 101. On the other hand, a counter electrode 108 and a color filter layer 109 are formed on the inner surface of the counter substrate 102. The color filter layer 109 has RGB three primary color segments and is aligned with each pixel electrode 106. Further, although not shown, an alignment film similarly subjected to a rubbing treatment is provided on the surface of the counter electrode 108. Further, the polarizing plate 1 is formed on the outer surfaces of the driving substrate 101 and the counter substrate 102, which are adhered to each other.
10,111 are attached. The TFT 107 is selected via the scanning line 104, and the signal potential is written to the pixel electrode 106 via the signal line 105. A voltage is generated between the pixel electrode 106 and the counter electrode 108, and the liquid crystal 103 rises.
This is a pair of crossed Nicols arranged polarizing plates 110, 1
By 11, the color change is displayed by taking out the white incident light as a change in the transmission amount.

FIG. 9 is a schematic view showing one pixel of an active matrix type liquid crystal panel by cutting it out. The left side shows a state in which no voltage is applied and the right side shows a state in which voltage is applied. The polarization axis a of the upper polarizing plate 111 and the polarization axis b of the lower polarizing plate 110 are orthogonal to each other. Further, the rubbing direction, that is, the alignment direction of the upper alignment film 112 and the rubbing direction, that is, the alignment direction of the lower alignment film 113 are also orthogonal to each other. Therefore, the liquid crystal 103 has a twist orientation twisted by 90 °. When no voltage is applied, the linearly polarized light component of the incident light that has passed through the upper polarizing plate 111 is reflected by the twist-oriented liquid crystal 103.
It is rotated by 0 ° and transmitted through the lower polarizing plate 110. Therefore, white display is obtained when no voltage is applied. On the other hand, when a voltage is applied, the liquid crystal 103 rises and the optical rotatory power is lost. Therefore, the linearly polarized component of the incident light is blocked by the lower polarizing plate 110, and black display is obtained.

[0004]

As described above, the alignment films are formed on the inner surfaces of the drive substrate 101 and the counter substrate 102 and the rubbing treatment is performed. Counter substrate 10
Regarding No. 2, since the alignment film is deposited on the counter electrode 108 having a relatively flat surface, a uniform rubbing treatment can be performed and a relatively stable alignment property with respect to liquid crystal can be obtained. On the other hand, the TFT 107 is formed on the inner surface of the driving substrate 101.
The pixel electrode 106 and the like are formed in an integrated manner and include a step.
Therefore, since the surface of the alignment film deposited thereon has fine irregularities, the rubbing treatment cannot be performed uniformly,
There is a weakly oriented portion.

In manufacturing a liquid crystal panel, a drive substrate 101 and a counter substrate 102, which have been previously subjected to rubbing treatment or orientation treatment, are adhered to each other through a predetermined gap, and then a liquid crystal 103 is injected into the gap. At this time, since liquid crystal molecules flow, there is a problem or a problem that the fine structure on the surface of the alignment film is damaged. In particular, there is a problem in that damage is remarkably exhibited in a portion of the drive substrate 101 side where the orientation is weak, and a desired twist orientation cannot be obtained. Therefore, conventionally, defects such as display unevenness have frequently occurred.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, it is an object of the present invention to provide a liquid crystal injection method that does not adversely affect the alignment film. The following measures have been taken in order to achieve this object. That is, in a method of manufacturing a liquid crystal panel including a drive substrate in which thin film transistors are integratedly formed as a liquid crystal drive element, and a counter substrate having a counter electrode and arranged to face the drive substrate, a liquid crystal alignment direction of the drive substrate It is characterized in that the liquid crystal is injected into the liquid crystal panel in the same direction.

Further, a liquid crystal panel suitable for realizing such means has the following structure. That is, an active substrate including a liquid crystal drive element, a drive substrate on which an alignment film for imparting a predetermined alignment direction to liquid crystal is formed, a counter substrate on which a counter electrode is formed, and a liquid crystal layer injected into a gap between both substrates. The matrix type liquid crystal panel is characterized in that an injection port is provided at a specific position on the outer peripheral portion of the substrate so that the liquid crystal injection direction is in the same direction as the alignment direction.

[0008]

In the present invention, the liquid crystal is injected in the liquid crystal panel in the same direction as the liquid crystal alignment direction of the drive substrate. That is, during injection, the liquid crystal molecules flow along the alignment direction. Therefore, the possibility of damaging the fine groove structure on the surface of the alignment film formed by the rubbing treatment is reduced, and the initial state can be preserved as it is even in the region where the orientation is relatively weak. . Therefore, it is possible to remarkably suppress the disturbance of the twist alignment of the liquid crystal molecules or the alignment unevenness. Note that liquid crystal molecules flow in a direction orthogonal to the alignment direction on the counter substrate side. However, the alignment state on the counter substrate side is originally uniform and stable, and is not likely to be damaged by liquid crystal injection.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is an explanatory view showing an embodiment of a method for manufacturing a liquid crystal panel according to the present invention. As shown in (A), the drive substrate 1 and the counter substrate 2 are adhered to each other with a sealing material 3 with a predetermined gap. The predetermined gap is set to 4 to 6 μm, for example. Although the sealing material 3 extends over substantially the entire circumference of the substrate, a partial cutout is provided to form the injection port 4. It should be noted that pixel electrodes and TFTs are integrally formed in advance on the inner surface of the drive substrate 1 by an IC process.
Further, an alignment film is attached and rubbing treatment is also performed. On the other hand, on the inner surface of the counter substrate 2, a color filter layer and a counter electrode are formed in advance. Furthermore, an alignment film is applied and a predetermined rubbing treatment is also performed.

Next, the liquid crystal injection method will be described with reference to FIG. The alignment direction of the drive substrate 1 by the rubbing process is indicated by an arrow DR1 and extends from the lower end side to the upper end side of the liquid crystal panel. A pad electrode 5 for external connection is provided on the exposed surface of the drive substrate 1 at the upper end.
On the other hand, the alignment direction of the counter substrate 2 by the rubbing treatment is indicated by arrow D.
As indicated by R2, the liquid crystal panel faces from the right end side to the left end side.

The drive substrate 1 and the counter substrate 2 are attached to each other with the sealing material 3 as described above. A part of the sealing material 3 is removed on the lower end side of the liquid crystal panel, and the injection port 4
Stipulate. The liquid crystal 6 is introduced into the panel through the injection port 4 by, for example, a vacuum injection method. Therefore, the injection direction is from the lower end side to the upper end side of the liquid crystal panel as shown by the arrow DL, has the same orientation as the alignment direction DR1 of the drive substrate, and is orthogonal to the alignment direction DR2 of the counter substrate. This (B)
Indicates an intermediate state of the liquid crystal injection process, and the liquid crystal 6 flows and advances along the inner surface of the liquid crystal panel. Although the traveling direction is radial, the traveling direction when averaged over all is the injection direction DL.

Next, a specific example of the rubbing process will be described with reference to FIG. TFTs and pixel electrodes are integrally formed in advance on the surface of the drive substrate 1 made of quartz glass or the like by an IC process. An alignment film 7 is formed on the surface. The alignment film 7 is made of, for example, an organic polymer material and is supplied by printing or the like. The film thickness is, for example, about 80 nm. Then, the surface of the alignment film 7 is rubbed. In this example, the roller 8 covered with a fiber cloth such as cotton or rayon is used. This roller 8 is, for example, 100
It rotates counterclockwise at a speed of ~ 1000 rpm and moves from left to right in the drawing. At this time, a predetermined pressure is applied, and the surface of the alignment film 7 is rubbed. Therefore, the orientation direction DR1 of the drive substrate 1 coincides with the roller movement direction as shown. Unlike the counter substrate, there are many steps such as wiring patterns on the surface of the driving substrate 1, and the steps become more remarkable as the number of pixel electrodes increases. In the rubbing process, it is difficult to obtain a uniform alignment ability due to the influence of the pattern step, and there are regions where the alignment ability is weak, such as the shadow of the step portion.

Next, a liquid crystal injection method will be described with reference to FIG. In this embodiment, as shown in FIG.
Is used to perform so-called vacuum injection. A liquid crystal reservoir 10 is arranged at the bottom of the vacuum chamber 9 and contains the liquid crystal 6 to be injected. A panel 11 in which a drive substrate and a counter substrate are bonded together is housed in the upper part of the vacuum chamber 9. In this state, the vacuum chamber 9 is evacuated to reduce the pressure inside and the panel 11 is degassed. Next, (B)
As shown in, the panel 11 is lowered to bring the liquid crystal 6 held in the liquid crystal reservoir 10 into contact with the injection port. By doing so, the liquid crystal 6 gradually enters the inside of the panel 11 due to the capillary phenomenon. As the injection proceeds, nitrogen gas is introduced into the vacuum chamber 9 to gradually increase the pressure. In this way, the panel 11 is completely filled with the liquid crystal 6. The liquid crystal 6
Generally has a high viscosity and requires pressure for injection. If a rapid pressure change is applied in order to shorten the takt time of the implantation process, the alignment film may be damaged or the alignment ability may be damaged. Finally, as shown in (C), after the injection is completed, the panel 11 is pulled up, and the inside of the vacuum chamber 9 is returned to atmospheric pressure. Then, the panel 11 is taken out from the vacuum chamber 9 and the inlet is sealed with resin. Further, heat treatment is added to stabilize the alignment state of the liquid crystal.

In order to evaluate the effect of the present invention, the injection direction D
Four types of samples A, B, C, and D in which the combination of the alignment direction DR1 of the drive substrate and the alignment direction DR2 of the counter substrate were changed with respect to L were prepared. FIG. 4 shows the relationship between the injection direction and the orientation direction of each sample. In the sample A, the injection direction DL and the alignment direction DR1 of the drive substrate are orthogonal to each other, and the injection direction DL and the alignment direction DR2 of the counter substrate are opposite to each other. As for sample B, DL and DR1 are orthogonal to each other as in sample A, while DL and D are
R2 is in the same direction. DL for sample C
And DR1 are in the same direction, and DL and DR2 are orthogonal. That is, this sample C is an invention product. Finally, for sample D, DL and DR1 are in opposite directions, and DL and DR2 are orthogonal. Therefore, Samples A, B and D except Invention C are comparative products.

Next, the result of measuring the display unevenness occurrence rate of each sample will be shown with reference to FIG. The number of samples is n = 10 for each sample. The display unevenness was visually measured using a polarization microscope. The graph shown in (A) represents the display unevenness occurrence rate when the roller is set to low speed rotation and the rubbing process is performed. As is clear from this graph, the comparative products A, B, and D show remarkable display unevenness, while the invention product C does not show display unevenness.

(B) shows the display unevenness occurrence rate when the roller is set to high speed rotation and each sample is oriented. In this example, the rate of occurrence of display unevenness could be suppressed as a whole by increasing the rotation speed of the roller. However, the comparative products A, B and D still show some display unevenness, while the invention product C does not show any display unevenness. Inventive product C in which the alignment direction of the drive substrate and the liquid crystal injection direction coincide with each other in this manner can effectively prevent display unevenness regardless of the conditions of the rubbing treatment. In other words, if the present invention is adopted, there is an advantage that the degree of freedom in the process design of the rubbing process is increased.

Next, the mechanism of display unevenness or liquid crystal alignment unevenness will be described with reference to FIG. 6 by taking the sample A shown in FIG. 5 as an example. As shown in (A), in the sample A, the alignment direction DR1 of the drive substrate intersects the liquid crystal injection direction DL. When the liquid crystal is introduced through the inlet 4, it is filled in the panel through the flow path indicated by the arrow.

(B) is a schematic view showing a cross-sectional shape of the panel cut along the line XY shown in (A). As is clear from the figure, on the X side of the panel, that is, on the upper end side where the pad electrode is formed, the alignment direction DR1 and the direction of the liquid crystal flow channel match, and the liquid crystal molecules are normally aligned with a predetermined tilt angle. Forming a positive tilt region. on the other hand,
On the Y side of the liquid crystal panel, that is, on the lower end side, the alignment direction DR
Since the directions of 1 and the liquid crystal flow channel are opposite to each other, the liquid crystal molecules are aligned with an inverted tilt angle to form a reverse tilt region or a reverse tilt region. The 90 ° twist direction of the liquid crystal molecules in the positive tilt region and the 90 ° twist direction of the liquid crystal molecules in the reverse tilt region are opposite to each other, and a difference appears in the transmittance of the liquid crystal panel. In particular, a so-called disclination line is generated between the normal tilt area and the reverse tilt area, and the display quality is significantly impaired.

(C) shows a state in which the liquid crystal is stabilized by heat treatment after liquid crystal injection. As shown in the drawing, the reverse tilt region that has temporarily occurred is mostly returned to the normal state and is close to the normal tilt region. However, this recovery is not perfect, and the disorder of the alignment of the liquid crystal molecules partially remains, which appears as display unevenness. Unlike the counter substrate, pixels are integrated and formed on the surface of the driving substrate, and include innumerable steps. This is because damage occurs in the portion of the step portion where the orientation ability is weak.
Further, in the region where the liquid crystal flow direction and the alignment direction are different, the alignment force is generally reduced, and the display contrast becomes non-uniform.

In order to solve such a problem, in the present invention, the alignment direction of the drive substrate and the injection direction are set in the same direction during liquid crystal injection. As a result, the tilt angle of the liquid crystal molecules is not affected by the flow direction, damage is suppressed, and alignment is stabilized, so that display unevenness is reduced. Moreover, since the degree of freedom in the rubbing process setting conditions is increased even for a drive substrate on which uniform alignment process is generally difficult, a process suitable for mass production can be appropriately performed.

Finally, the process of assembling the liquid crystal panel according to the present invention will be described with reference to FIG. First, before assembling, a drive substrate on which pixel electrodes and thin film transistors are integrally formed and a counter substrate on which a color filter layer and a counter electrode are formed are prepared. In this example, a multi-cavity method is adopted, and the drive substrate is provided with circuit portions corresponding to a plurality of liquid crystal panels. First, in step S1, the surface of the driving substrate is washed. Next, in step S2, an alignment film is formed on the surface of the drive substrate. Then, in step S3, a rubbing process is performed. After cleaning is performed in step S4, the common electrode for leading out the counter electrode is transferred and printed in step S5.

In parallel with the steps S1 to S5 described above, the processing on the counter substrate side is performed. That is, after the surface of the counter substrate is washed in step S6, an alignment film is formed in step S7.
Then, a rubbing process is performed in step S8. After cleaning is performed in step S9, a sealing material is printed in step S10.

The drive substrate and the counter substrate which have been pretreated as described above are bonded by the following steps. First, step S11
In step 1, the drive substrate and the counter substrate are aligned and bonded to each other. In step S12, pressure and heat treatment is performed to cure the sealing material and bond the two substrates to each other. Next step S
In 13, the both substrates thus bonded are cut by a scriber and divided into individual panels. Process S1
At 4, the individual panels are filled with liquid crystal. Step S15
After sealing the injection port with resin in step S16, finally, in step S16
Heat treatment is applied to stabilize the alignment state of the liquid crystal.

[0024]

As described above, according to the present invention,
The injection direction when injecting liquid crystal into the panel is made to coincide with the liquid crystal alignment direction of the drive substrate. Therefore,
There is an effect that the orientation of the drive substrate is not damaged or damaged when the liquid crystal is injected. Since the orientation is not damaged or damaged, there is an effect that the degree of freedom of the orientation treatment is increased and the process design is facilitated. In particular, the present invention has a remarkable effect on an active matrix type liquid crystal panel having a region where the orientation is partially weak.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a method for manufacturing a liquid crystal panel according to the present invention.

FIG. 2 is an explanatory diagram showing a rubbing process.

FIG. 3 is an explanatory diagram showing a liquid crystal injection step.

FIG. 4 is a schematic diagram showing various samples prepared for the evaluation of the present invention.

FIG. 5 is a graph showing a display unevenness occurrence rate of the created sample.

FIG. 6 is a schematic diagram for explaining a mechanism of display unevenness.

FIG. 7 is a process drawing showing the method of assembling the liquid crystal panel.

FIG. 8 is a perspective view showing a structure of a general active matrix type liquid crystal panel.

FIG. 9 is an operation explanatory diagram of an active matrix liquid crystal panel.

[Explanation of symbols]

 1 Driving Substrate 2 Counter Substrate 3 Sealing Material 4 Injection Port 6 Liquid Crystal 7 Alignment Film 8 Roller 9 Vacuum Chamber 10 Liquid Crystal Storage 11 Panel DR1 Drive Substrate Orientation Direction DR2 Counter Substrate Orientation Direction DL Injection Direction

Claims (2)

[Claims] 1. A method of manufacturing a liquid crystal panel, comprising: a drive substrate having thin film transistors integrated as liquid crystal drive elements; and a counter substrate having a counter electrode and arranged to face the drive substrate. A method for manufacturing a liquid crystal panel, characterized in that the directions of injection of liquid crystals into the liquid crystal panel are the same with respect to the directions. 2. A liquid crystal drive element, a drive substrate on which an alignment film for imparting a predetermined alignment direction to the liquid crystal is formed, a counter substrate on which a counter electrode is formed, and a liquid crystal layer injected into a gap between the two substrates. In the active matrix type liquid crystal panel, the active matrix type liquid crystal panel is characterized in that an injection port is provided at a specific position on the outer peripheral portion of the substrate so that the liquid crystal injection direction is in the same direction as the alignment direction.