JPH1114994A - Orientation method of liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a pretilt angle large and uniform even in an orienting process using a rubbing roller with robbing cloth. SOLUTION: While plus ions are stuck on the surface of an orientation film 36 and minus ions are stuck on the surface of the rubbing roller 32, rubbing is carried out. At this time, static electricity is generated, but minus static electricity generated on the surface of the orientation film 36 is combined with plus ions stuck on the the surface and neutralized and plus static electricity generated on the surface of the rubbing roller 32 is neutralized by being combined with minus ions stuck on the same surface. Consequently, the generation of the static electricity at the time of the rubbing is suppressed and even in the orienting process using the rubbing roller 32 having the rubbing cloth, the pretilt angle can be made large and uniform. Here, pure water may be sprayed instead of the ions. Furthermore, the surface of the orientation film 36 may be coated thinnly with substance which has small surface tension, e.g. oil having a hydrophobic base like a long-chain alkali base such as fatty acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for aligning a liquid crystal display.

[0002]

2. Description of the Related Art Actively driven twisted nematic liquid crystal display devices (hereinafter referred to as TN-L) are known.
CD). FIG. 2 shows such a conventional TN-L
FIG. 2 shows a partial cross-sectional view of an example of a CD. This T
The N-LCD has a lower glass substrate 1 and an upper glass substrate 11. A scanning signal line 2 including a gate electrode is provided at a predetermined location on the upper surface of the lower glass substrate 1, an auxiliary capacitance line 3 is provided at another predetermined location, and a gate insulating film 4 is provided over the entire upper surface. Have been. A thin film transistor (including the gate electrode) 5 is provided at a predetermined location on the upper surface of the gate insulating film 4, and a pixel electrode 6 is provided at another predetermined location connected to the thin film transistor 5. A data signal line 7 is provided at a location connected to the thin film transistor 5. A passivation film 8 is provided on the entire upper surface except the pixel electrode 6, and an alignment film 9 is provided on the upper surfaces of the pixel electrode 6 and the passivation film 8.

On the other hand, a black matrix 12 is provided on the lower surface of the upper glass substrate 11, a color filter 13 is provided on the lower surface, a common electrode 14 is provided on the lower surface, and an alignment film 15 is provided on the lower surface. Is provided. Then, the lower glass substrate 1 and the upper glass substrate 11 are bonded via a sealing material (not shown), and the respective alignment films 9 and 15 are bonded.
A liquid crystal 16 is sealed between them. In this case, the liquid crystal 16
Is composed of a twisted nematic liquid crystal twisted continuously by 90 °.

In such a TN-LCD, the pretilt angle is generally as low as about 2 ° to 3 °. In particular, when the number of pixel electrodes 6 is increased to enable high-definition display, the Significant reduction in display quality due to the occurrence of discrination is a major problem. That is, when a horizontal electric field is generated between the pixel electrode 6 and a predetermined part of the auxiliary capacitance line 3 as shown by a dotted line in FIG. When the molecules are arranged in the same direction as the pretilt angle, the normal display area 22
On the other hand, by arranging the liquid crystal molecules along the electric field indicated by the dotted line on the right side of the dashed line indicated by the reference numeral 21, that is, by arranging the liquid crystal molecules in the direction opposite to the pretilt angle,
The right side is an abnormal display area 23 where light leakage occurs and white spots occur, and a dashed line indicated by reference numeral 21 therebetween is a disclination line. FIG. 3 shows a plan view of one pixel electrode 6 in this case.
In the figure, an area indicated by oblique lines is an abnormal display area 23 in which light leakage occurs and white spots occur. As described above, when a blank portion occurs in a part of one pixel electrode 6, TN-LC
The contrast of the entire display portion of D is significantly reduced, and the display quality is significantly reduced. Therefore, conventionally, the light leakage due to the disclination is reduced by providing the black matrix 12 according to the position where the disclination occurs.

[0005]

However, in such a conventional TN-LCD, since the black matrix 12 is provided according to the position where disclination occurs, the aperture ratio is greatly reduced. was there. It should be noted that increasing the pretilt angle can prevent the occurrence of disclination, but the conventional general orientation treatment, that is, the orientation using a rubbing roller in which a rubbing cloth made of a flocked cloth is wound around a rubbing roller body. In the processing, since the control of the rubbing density, which means the rubbing strength, is performed by the amount of pushing the bristle of the rubbing cloth into the alignment film, the margin for controlling the pretilt angle to be high is narrow, and the variation of the pretilt angle is large. Another problem is that misalignment is likely to occur. On the other hand, in the case of a simple matrix type STN-LCD,
Since the twist angle is larger than in the case of the TN-LCD, the pretilt angle is set higher than in the case of the TN-LCD. There is a problem that alignment unevenness easily occurs. An object of the present invention is to make it possible to make the pretilt angle high and uniform even in an orientation process using a rubbing roller having a rubbing cloth.

[0006]

According to the first aspect of the present invention,
When rubbing the surface of an alignment film provided on one surface of a substrate with a rubbing roller having a rubbing cloth, a substance for reducing a coefficient of friction between the alignment film and the rubbing roller is supplied. Things. According to a third aspect of the present invention, when the surface of the alignment film provided on one surface of the substrate is rubbed by a rubbing roller having a rubbing cloth, a substance having a small surface tension is applied to the surface of the alignment film. Things.

According to the present invention, a rubbing cloth is provided when a substance for reducing the coefficient of friction is supplied between the alignment film and the rubbing roller, or when a substance having a small surface tension is applied to the surface of the alignment film. The pretilt angle can be made high and uniform even in the orientation treatment using a rubbing roller.

[0008]

FIG. 1 is a sectional view showing a schematic configuration of an orientation device according to an embodiment of the present invention.
This orienting device includes a table 31 movable in the direction of arrow A.
A rubbing roller 32 rotatable in the direction of arrow B is disposed on the upper side, and the first ion gun 3 is provided in front of the rubbing roller 32.
3 is arranged, and a second ion gun 34 is arranged on the rear side of the rubbing roller 32. The rubbing roller 32 is formed by winding a rubbing cloth made of a flocked cloth such as rayon or cotton cloth around the rubbing roller body, not shown in detail. The first ion gun 33 includes a glass substrate 3 fixed on a table 31.
5 is for irradiating the surface of the alignment film 36 made of polyimide provided on the upper surface of the substrate 5 with + ions (gas phase ions) such as N ₂ ⁺ . The second ion gun 34, the surface of the rubbing roller 32 OH ^- is for irradiating ions (gas phase ion) - or the like.

Next, a case in which an alignment process is performed by this alignment apparatus will be described. First, the table 31 is moved in the direction of arrow A together with the glass substrate 35 fixed thereon, and the first ion gun 33 irradiates the surface of the alignment film 36 on the glass substrate 35 with + ions such as N ₂ ^+. , Alignment film 3
+ Ions are attached to the surface of No. 6. Further, by rotating the rubbing roller 32 in the direction of arrow B, the surface OH of the rubbing roller 32 by a second ion gun 34 ^- etc. - is irradiated with ions, the surface of the rubbing roller 32 - adhering the ions. Then, the alignment film 3 is moved by the rubbing roller 32.
When the surface of No. 6 is rubbed in a certain direction, static electricity is generated during the rubbing. In this case,-
Is generated, but the negative static electricity is combined with the + ions attached to the surface of the alignment film 36 and neutralized. On the other hand, + static electricity is generated on the surface of the rubbing roller 32, and this + static electricity is neutralized by combining with − ions attached to the surface of the rubbing roller 32. As a result, the generation of static electricity during rubbing is suppressed.

As described above, the generation of static electricity during rubbing can be suppressed. As a result, the rubbing roller 32
The coefficient of friction between the film and the alignment film 36 is reduced, and the pretilt angle can be made high and uniform even in the alignment processing using the rubbing roller 32 having a rubbing cloth.
Therefore, in the case of the TN-LCD, the occurrence of disclination can be prevented, and in the case of the STN-LCD, the occurrence of alignment unevenness such as a reverse twist can be prevented.

The orientation film 3 is sprayed using a pure water spray nozzle.
6 may be sprayed on at least one of the surface of the rubbing roller 32 and the surface of the rubbing roller 32. In this case, the generation of static electricity is suppressed by humidification,
Thereby, the friction coefficient between the rubbing roller 32 and the alignment film 36 is reduced, and the pretilt angle can be made high and uniform even in the alignment processing using the rubbing roller 32 having the rubbing cloth.

A substance having a small surface tension, for example, an oil having a hydrophobic group such as a long-chain alkyl group, such as a fatty acid, is applied to the surface of the rubbing cloth of the rubbing roller 32 on the surface of the alignment film 36 made of polyimide. The applied oil may be thinly applied to the surface of the alignment film 36 during rubbing. In this case, the surface tension of the surface of the alignment film 36 is reduced, and the pretilt angle can be made high and uniform even in the alignment process using the rubbing roller 32 having a rubbing cloth. Note that oil may be directly applied to the surface of the alignment film 36 using an oil application roller. Further, using an oil spray nozzle, oil is sprayed on the surface of the rubbing cloth of the rubbing roller 32,
At the time of rubbing, the sprayed oil may be applied to the surface of the alignment film 36, or the oil may be sprayed directly on the surface of the alignment film 36.

Further, in the above-described embodiment, as shown in FIG. 1, a table 31 is fixed to a glass substrate 3 fixed thereon.
Rubbing roller 3 while moving in the direction of arrow A with
2 is rotated in the direction of arrow B to rub the surface of the alignment film 36 in a fixed direction, but the table 31 is fixed and the rubbing roller 32 is moved in the direction of arrow A while rotating in the direction of arrow B. You may make it do. In either case, the rubbing angle may be adjusted by adjusting the angle of the table 31 or by adjusting the angle of the rubbing roller 32.

[0014]

As described above, according to the present invention, a substance for reducing the friction coefficient is supplied between the alignment film and the rubbing roller, or a substance having a small surface tension is provided on the surface of the alignment film. Is applied, the pretilt angle can be made high and uniform even in the orientation treatment using a rubbing roller having a rubbing cloth. As a result, T
In the case of the N-LCD, the occurrence of disclination can be prevented, and in the case of the STN-LCD, the occurrence of alignment unevenness such as a reverse twist can be prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a schematic configuration of an orientation device shown for describing an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of an example of a conventional liquid crystal display device.

FIG. 3 is a plan view showing a state in which disclination has occurred in one pixel electrode under a certain condition.

[Description of Reference Numerals] 31 table 32 rubbing roller 33 first ion gun 34 second ion gun 35 glass substrate 36 orientation film

Claims (4)

[Claims] When rubbing the surface of an alignment film provided on one surface of a substrate with a rubbing roller having a rubbing cloth, a substance for reducing a coefficient of friction between the alignment film and the rubbing roller is used. A method for aligning a liquid crystal display device, comprising: 2. The method according to claim 1, wherein the substance is gas phase ions or pure water. 3. A liquid crystal, characterized in that when rubbing the surface of an alignment film provided on one surface of a substrate with a rubbing roller having a rubbing cloth, a substance having a small surface tension is applied to the surface of the alignment film. Display device orientation method. 4. The method according to claim 3, wherein the substance is an oil having a hydrophobic group.