JPH10268311A - Liquid crystal cell and its alignment treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the uneven alignment of liquid crystals from being visually recognized as uneven brightness and darkness, etc., by confining the relative moving distance of a rubbing roller and a stage within a very small pixel width. SOLUTION: Plural transparent electrodes 24 and 14 exist to face each other perpendicularly. These electrodes form the plural grid-like pixels A together with color filters and antiferroelectric liquid crystals. These pixels act as display sections at the time of driving of a liquid crystal cell. The transparent electrodes 14 are provided thereon with alignment layers by offset printing in an oriented film forming stage, by which an electrode substrate 10 is formed. The alignment layers of the electrode substrates 10 and 20 are subjected to a rubbing treatment in a rubbing state. The relative moving distance L between the stage and the rubbing roller while the rubbing roller revolves one turn is confined within the width of the two pixels, by which the uneven alignment of the liquid crystals appearing at least one pitch in the relative moving distance L may be confined within the width of the two pixels. As a result, even the one pitch of the uneven liquid crystal alignment by the eccentricity of the rubbing roller may be suppressed within the width of the two pixels and the striped uneven liquid crystal alignment is not visually recognized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal cell and a method for aligning the liquid crystal cell.

[0002]

2. Description of the Related Art Conventionally, as a general alignment treatment method for a liquid crystal cell, a method described in JP-A-63-240522 has been proposed. This involves placing the electrode substrate on the stage, installing a rubbing roller wound with a rubbing cloth facing the electrode substrate, rotating the rubbing roller, and moving the stage in a certain direction, so that the surface of the alignment film on the electrode substrate Rubbing.

The rubbing density is ((πr × N−
V) / V), and at the time of rubbing, the rubbing density is set in the range of 15 to 1000. Here, r (cm) is the diameter of a rubbing roller wound with a rubbing cloth, N (rpm) is the number of rotations of the rubbing roller, and V (c).
m / min) represents the moving speed of the stage, that is, the electrode substrate.

[0004]

According to the study of the present inventors, when a liquid crystal cell was subjected to rubbing treatment using the above-mentioned conventional alignment treatment method, good liquid crystal alignment was not obtained. FIG. 7 shows a plan view of a liquid crystal cell K manufactured using the above-described conventional alignment treatment method. Regions with good liquid crystal alignment (regions without hatching) and regions with poor liquid crystal (regions with hatching) alternately appear as stripes with respect to the rubbing direction, causing uneven liquid crystal alignment. The striped alignment unevenness is a problem because it is visually recognized as uneven brightness of dark brightness and uneven brightness during driving display.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a liquid crystal cell in which uneven alignment of liquid crystal is not visually recognized, and an alignment processing method thereof.

[0006]

The present inventors have made intensive studies and as a result, the width formed by the above-described two adjacent regions having good alignment and bad alignment, that is, one pitch of the stripe-like liquid crystal alignment unevenness is as follows. It was confirmed that this occurred at least once during one rotation of the rubbing roller. Here, the relative speed V between the rubbing roller and the stage is given by: V = πr × N ±, where r is the diameter of the rubbing roller on which the rubbing cloth is wound, N is the number of rotations of the rubbing roller, and V ′ is the moving speed of the stage. V ′ (in the case where the rotation direction of the rubbing roller is the same as the movement direction of the stage: +, and in the opposite case, −).

The relative movement distance L (hereinafter, referred to as relative movement distance) L between the rubbing roller and the stage per one rotation of the rubbing roller is represented by L = πr ± (V ′ / N). That is, one pitch of the alignment unevenness of the liquid crystal appears within the range of the relative movement distance L. From this, the present inventors,
It was considered that the alignment unevenness of the liquid crystal was mainly caused by the radial eccentricity of the rubbing roller. Here, the eccentricity means that the rotation axis of the rubbing roller is deviated from the center of the circle, or the rubbing roller itself is not a perfect circle (for example, elliptical) even when the rotation axis is at the center of the circle.

If the rubbing roller has radial eccentricity,
Since the distance between the rubbing roller and the surface of the alignment film changes during one rotation of the rubbing roller, the region where the surface of the alignment film is strongly rubbed by the rubbing cloth and the region where the surface of the alignment film is weakly rubbed are formed in the above-mentioned stripes. Correspondingly, the alignment unevenness of the liquid crystal also becomes striped. The present inventors have found that it is actually difficult to completely eliminate radial eccentricity of the rubbing roller due to factors such as processing errors in the production of the rubbing roller and unevenness in the degree of wear of the rubbing cloth. I thought there was.

Therefore, the present inventors have proposed that the relative movement distance L is shortened and the pitch of the liquid crystal alignment unevenness is reduced, so that even if there is actually a stripe-shaped alignment unevenness, the apparent alignment unevenness may occur. Was not visually recognized, and it was considered that the liquid crystal alignment might be at a level considered to be uniform. Simply, the relative movement distance L should be close to infinity, but the rubbing time becomes enormous, which is not preferable in practical use. Therefore, an experiment was conducted to determine a practical allowable range. When the relative movement distance L was reduced within a minute pixel width that was not visible with reference to the pixel width of the liquid crystal cell, the above liquid crystal alignment was regarded as uniform. I found that I can achieve the level that is expected.

That is, according to the first aspect of the present invention, the liquid crystal cell (1) has a pair of electrode substrates which are overlapped so as to face each other with the alignment films (16, 26) via the annular seal (30). (10, 20) and both electrode substrates (1
A liquid crystal (60) sealed between the first and second electrode substrates (0, 20) to form a plurality of pixels (A) together with the two electrode substrates (10, 20), and an alignment film (16, 26). Is aligned by using a rubbing roller (70), and at least one pitch of the alignment unevenness of the liquid crystal (60) generated by the alignment processing falls within a minute pixel width that cannot be seen among a plurality of pixels (A). As described above, the alignment film (16, 26) is subjected to an alignment treatment.

In other words, according to the present invention, the relative speed V is reduced with respect to the pixels provided in the liquid crystal cell (1) based on one pitch of the liquid crystal alignment unevenness. The relative movement distance L is set so as to be within a very small pixel width such that uneven alignment is not visually recognized. As a result, it is possible to provide a liquid crystal cell in which the alignment unevenness of the liquid crystal becomes uneven in brightness and darkness and is not visually recognized. Here, the minute pixel width that cannot be visually recognized is 2 as in claim 2.
Pixels are preferred.

Further, according to the invention of claim 3, according to claim 1,
Is fixed on the stage (72), and the alignment film (1) of the electrode substrate (10, 20) is fixed.
A rubbing roller (70) is disposed so as to face the liquid crystal (6, 26).
In order to make the relative speed between the stage (72) and the rubbing roller (70) such that at least one pitch of the alignment unevenness of 0) falls within a minute pixel width that is not visible among the plurality of pixels (A), The alignment process is performed by driving at least one of the stage (72) and the rubbing roller (70).

According to the present invention, it is possible to provide a method for aligning a liquid crystal cell which achieves the above-mentioned effects. According to a fifth aspect of the present invention, in the liquid crystal cell alignment processing method according to the third or fourth aspect, the relative movement direction between the rubbing roller (70) and the stage (72) is set to be relative to the rubbing direction. And is inclined at a predetermined angle (θ).

As a result, the rubbing roller (70) moves in the rubbing direction while being shifted with respect to the stage (72) in the rotation axis direction. Therefore, even when an abnormal portion occurs in the bristles of the rubbing cloth around the outer periphery of the rubbing roller (70), the same portion of the alignment film (16, 26) is not rubbed a plurality of times only by the abnormal portion. Therefore,
In addition to the functions and effects of the third and fourth aspects of the present invention, it is possible to provide an alignment processing method for a liquid crystal cell that reduces damage to an alignment film.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) The embodiment of the present invention shown in the drawings will be described below. FIG. 1 shows a sectional structure of a liquid crystal cell 1 according to the present invention. The liquid crystal cell 1 includes an electrode substrate 10 and an electrode substrate 20 which are superposed on each other.
These two electrode substrates 10 and 20 are adhered and supported via an annular seal 30, a spacer 50 and adhesive fine particles 40.

An antiferroelectric liquid crystal 60 is sealed between the two electrode substrates 10 and 20. The distance (cell gap) between the two electrode substrates 10 and 20 is 1.5 μm.
m. The electrode substrate 10 has a transparent substrate 11 made of, for example, glass. On the inner surface of the transparent substrate 11, a plurality of (for example, 400) stripe-shaped transparent electrodes 14, an insulating film 15, and an alignment film 16 are sequentially formed. Are laminated. Of these, the alignment film 16 is provided on the inner peripheral side of the seal 30.

On the other hand, the electrode substrate 20 has a transparent substrate 21 made of, for example, glass. On the inner surface of the transparent substrate 21, a color filter 22 made of resin, an overcoat film 23, (For example, 256) transparent electrodes 24, insulating films 25, and alignment films 26 are stacked. Among them, the color filter 22 and the alignment film 2
6 is provided on the inner peripheral side of the seal 30.

As shown in FIG. 2 in an enlarged manner, the plurality of transparent electrodes 24 (for example, 100 μm in width) are
(For example, 200 μm in width), and these transparent electrodes 14, 24 are provided with a plurality of grid-like pixels (for example, 10 μm) together with the color filter 22 and the antiferroelectric liquid crystal 60.
(0 μm × 200 μm) A is formed. These lattice-shaped pixels A function as a display unit on which display is performed when the liquid crystal cell 1 is driven.

Here, the transparent electrodes 14 and 24 are made of ITO (I
Alignment films 16 and 26 are made of polyimide resin or the like. Next, a method of manufacturing the liquid crystal cell 1 having the above configuration will be described with reference to FIG. Original substrate forming step S for electrode substrates 10 and 20
In 1, a transparent electrode 14 and an insulating film 15 are sequentially formed on the inner surface of a transparent substrate 11. On the other hand, a color filter 22, an overcoat film 23, a transparent electrode 24, and an insulating film 25 are sequentially laminated on the inner surface of the transparent substrate 21.

In the orientation film forming step S2, the orientation film 16 is formed by offset printing on the transparent electrode 14 and the insulating film 1.
5, and an electrode substrate 10 is formed. On the other hand, the alignment film 26 is provided on the color filter 22 via the overcoat film 23, the transparent electrode 24, and the insulating film 25 to form the electrode substrate 20. In the rubbing step S3, the electrode substrate 1
The rubbing process is performed on the alignment film 16 of zero and the alignment film 26 of the electrode substrate 20 as follows.

Here, the rubbing device of this embodiment is shown in FIG.
And FIG. FIG. 4 is generally referred to as a stage moving rubbing machine, and has a cylindrical rubbing roller 70 indicated by a two-dot chain line in the figure, a roller rotation motor 71 to which the rubbing roller 70 is attached, and a variable number of rotations.
A stage 72 on which the electrode substrate 10 or the electrode substrate 20 is placed, and a stage moving motor 73 having a variable moving speed for moving the stage 72 in the rubbing direction are provided. In FIG. 4, the roller rotation motor 71 is shown in a see-through manner.

The angle of the roller rotation motor 71 and the stage 72 can be adjusted, and the rubbing roller 70 and the electrode substrate 10 or 20 can be adjusted.
By changing the angle, the rubbing direction can be inclined with respect to the stage moving direction. The inclination angle is desirably 4 ° to 86 °. FIG. 5 is a cross-sectional view of the rubbing roller 70 during rubbing and the electrode substrates 10 and 20 to be rubbed. A rubbing cloth 70a is wound around the outer periphery of the rubbing roller 70, and bristles (pile) 70b are provided on the rubbing cloth 70a so as to stand upside down. The rubbing cloth 70a and the bristles 70b are made of rayon, nylon, cotton, or the like.
The electrode substrates 10 and 20 show only the alignment films 16 and 26, and other laminated portions are omitted.

The rubbing process is performed as follows using the rubbing apparatus having the above configuration. The rubbing roller 70 is attached to a roller rotation motor 71. Then, the alignment films 16 and 26 of the electrode substrates 10 and 20 are set on the stage 72 so as to face the rubbing roller 70, and the height of the rubbing roller 70 and the stage 72 is set to a predetermined value so that a predetermined rubbing strength is obtained. Adjust to.

Subsequently, the roller rotating motor 71 is driven to rotate the rubbing roller 70 around the axis at a predetermined number of revolutions, while moving the stage 72 in the direction of the rubbing roller 70 at a predetermined speed. The stage 72 is moved back and forth in the rubbing direction under the rubbing roller 70 by the stage moving motor 73 (arrows D and E in FIG. 5).
Direction).

When the electrode substrates 10 and 20 come under the rubbing roller 70 in either the forward movement indicated by the arrow D in FIG. 5 or the return movement indicated by the arrow E in FIG. As shown, the bristles 70 of the rubbing cloth 70a
The surfaces of the alignment films 16 and 26 are rubbed by b. In the present embodiment, the alignment films 16 and 26 are rubbed during the backward movement.
That is, the rotation direction of the rubbing roller 70 and the stage 72
Is the same as the moving direction.

Using the rubbing device described above, the liquid crystal 60
The rubbing process is performed by driving the stage 72 so that the relative speed between the stage 72 and the rubbing roller 70 is set so that at least one pitch of the alignment unevenness of the pixel A falls within a minute pixel width that is not visible among the plurality of pixels A. I do. In the present embodiment, as shown in FIG.
The relative moving distance L between the stage 72 and the rubbing roller 70 during one rotation is within a two-pixel width (about 500 μm in the present embodiment). Thereby, the alignment unevenness of the liquid crystal 60 in which at least one pitch appears in the relative movement distance L can be set within a width of two pixels.

Here, the reference pixel width is equal to the electrode substrate 10.
And the width of two pixels includes the width of the gap between the adjacent transparent electrodes 14. By the way, the actual rubbing condition is obtained as a rubbing density R, and the rubbing density R is R = (πr × N−V ′) /
It is expressed by the equation of V ′. Here, r is the diameter of the rubbing roller 70 wound with a rubbing cloth (7.5 c in this embodiment).
m), N is the number of revolutions of the rubbing roller 70 (1000 rpm in the present embodiment), and V ′ is the moving speed of the stage 72 (3.3 mm / sec (= 19.8 cm / in the present embodiment).
Min)). Therefore, in the present embodiment, the rubbing density R
Is 1188, which is approximately 1200.

That is, in this embodiment, the rubbing density is higher than the rubbing density of 15 to 1000 described in the section of the prior art. Incidentally, the relative speed V between the stage 72 and the rubbing roller 70 is represented by (πr
× N−V ′), but using the above values,
The relative velocity V is about 23500 cm / min.

By setting each parameter as in the above numerical values, the relative movement distance L can be set to a width of two pixels. These numerical values show an example of the present embodiment, and each parameter is not limited to the above numerical values. in short,
By adjusting the parameters r, N, and V ', the relative movement distance L
Is set to be within two pixel widths.

As described above, the parameters are set, and as shown in FIG. 2, the electrode substrate 10 is moved in a direction perpendicular to the stripe of the transparent electrode 14 shown by the arrow B, and the electrode substrate 20 is moved by the arrow. A rubbing process is performed in a fixed direction parallel to the stripe of the transparent electrode 24 shown in C, and the rubbing step S3 ends. Subsequently, in the spacer / adhesion fine particle dispersing step S4, on the alignment film of the electrode substrate 10,
The spacers 40 and the adhesion fine particles 50 are dispersed. on the other hand,
In the seal printing step S5, the seal 30 is formed annularly on the outer peripheral edge of the inner surface of the electrode substrate 20 by printing a sealant. Note that a liquid crystal injection port is formed in a part of the seal 30.

Subsequently, in a superposition step S6, the electrode substrate 10 is superposed on the electrode substrate 20 via the seal 30, the spacer 40 and the adhesive fine particles 50. In the present embodiment, as shown in FIG. 2, the rubbing direction B of the electrode substrate 10 and the rubbing direction C of the electrode substrate 20 are opposite and parallel to each other, but may be the same and parallel to each other. Alternatively, both rubbing directions B and C may not be parallel to each other but have an angle.

Then, in the seal hardening step S7, the pressure is applied to both the electrode substrates 10 and 20 while heating, and the seal 30 is pressed.
And a predetermined cell gap is secured. Thereafter, in the liquid crystal enclosing step S8, the antiferroelectric liquid crystal 60 is liquefied, injected and filled between the inner surfaces of the two electrode substrates 10 and 20 from the liquid crystal injection port of the seal 30, and the liquid crystal injection port is sealed. I do. Thereby, the manufacture of the liquid crystal cell 1 is completed.

When the state of the liquid crystal alignment of the liquid crystal cell 1 was observed under magnification using a microscope, as shown in FIG. 2, a region where the liquid crystal alignment was good (a region without diagonal hatching) and a region where the liquid crystal alignment was bad (diagonal hatching) with respect to the rubbing direction. Area)
Appeared alternately in stripes. However, it was confirmed that one pitch of the alignment unevenness of the liquid crystal was within the width of two pixels of the pixel A. The uneven liquid crystal alignment was not visually recognized as light and dark unevenness.

As described above, according to the alignment processing method of the present embodiment, by setting the relative movement distance L within a small two pixel width, one pitch of the liquid crystal alignment unevenness caused by the eccentricity of the rubbing roller 70 can be obtained. Can also be suppressed within the width of two pixels, so that it is possible to provide the liquid crystal cell 1 in which the stripe-shaped uneven liquid crystal alignment is not visually recognized. (Second Embodiment) Rubbing Step S3 of the First Embodiment
6A, the relative movement direction of the rubbing roller 70 and the stage 72, that is, the movement direction of the stage 72 is parallel to the rubbing direction indicated by the arrow Q in the figure. The rubbing direction is a direction orthogonal to the rotation axis of the rubbing roller 70.

In the second embodiment, as shown in FIG. 6B, the moving direction of the stage 72 is inclined by a predetermined angle θ from a rubbing direction (a direction orthogonal to the rotation axis of the rubbing roller 70) Q. Rubbing is performed at the same rubbing density R as in the first embodiment. Thereby, in the present embodiment, the rubbing roller 70 moves in the rubbing direction while being shifted from the stage 72 in the rotation axis direction.
Therefore, even when an abnormal portion F of the bristles 70b (see FIG. 6B) occurs around the outer periphery of the rubbing roller 70, the same portion of the alignment films 16 and 26 is rubbed a plurality of times only at the abnormal portion F. Therefore, the abnormal portion F is distributed and hits the alignment films 16 and 26. Therefore, in addition to the functions and effects of the first embodiment, damage to the alignment film can be reduced.

Here, in order to realize the effects of the present embodiment, it is preferable to set the above-mentioned predetermined angle θ in a range of 10 ° to 80 °. Note that the pixel width in each of the embodiments described above does not have to be two pixels corresponding to various pixel sizes. For example, when the pixel width in the rubbing direction is larger than the pixel width in each of the embodiments, 1. 5 pixels, 1 pixel, 0.5 pixels, etc., may be smaller than 2 pixels, and when the pixel width in the rubbing direction is smaller than the above, 2.5 pixels, 3 pixels, 4 pixels, etc. It may be more than two pixels. In this case, it is needless to say that one pitch of the liquid crystal alignment is small so that uneven brightness is not visually recognized.

It is to be noted that the starting point and the ending point of one pitch of the liquid crystal alignment unevenness do not have to coincide with both ends in the width direction of the transparent electrode 14 as shown in FIG. good. In the above embodiments, the surfaces of the alignment films 16 and 26 are rubbed by the rubbing roller 70 during the backward movement (the direction of arrow E in FIG. 5), but the forward movement (FIG. 5).
Rubbing density R when rubbing at the time of
R = (πr × N + V ′) / V ′ In this case, the relative pixel speed (πr × N + V ′) between the rubbing roller 70 and the stage 72 may be adjusted to make the pixel width minute.

In the rubbing apparatus of each of the above embodiments, the rotating rubbing roller is fixed and the stage is moved. On the contrary, the stage is fixed and the rotating rubbing roller is moved. Is also good. Each of the above embodiments can be applied to a liquid crystal cell using a ferroelectric liquid crystal or a nematic liquid crystal other than the antiferroelectric liquid crystal. Further, a color filter may not be provided, and a plurality of stripe-shaped partition spacer structures may be used instead of the spacers and the adhesion fine particles.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a liquid crystal cell according to a first embodiment of the present invention.

FIG. 2 is a plan view in which the pixel configuration of the liquid crystal cell of FIG. 1 is enlarged by microscopic observation.

FIG. 3 is a manufacturing process diagram of the liquid crystal cell of the first embodiment.

FIG. 4 is a perspective configuration diagram showing a rubbing device used in the first embodiment.

FIG. 5 is an operation explanatory view of the rubbing device of FIG. 4;

FIG. 6A is an explanatory diagram illustrating an alignment processing method according to the first embodiment, and FIG. 6B is an explanatory diagram illustrating an alignment processing method according to a second embodiment of the present invention.

FIG. 7 is a plan view showing uneven liquid crystal alignment of a conventional liquid crystal cell.

DESCRIPTION OF SYMBOLS 1 ... liquid crystal cell, 10, 20 ... electrode substrate, 16, 26 ... alignment film, 40 ... antiferroelectric liquid crystal, 70 ... rubbing roller,
72: stage, A: pixel.

Claims (5)

[Claims] 1. A pair of electrode substrates (10, 20) which are overlapped so as to face each other with an alignment film (16, 26) via an annular seal (30), and both electrode substrates (10, 20). The seal (3
0) and sealed between the two electrode substrates (10, 20).
And a liquid crystal (60) forming a plurality of pixels (A), wherein the alignment film (16, 26) is subjected to an alignment process using a rubbing roller (70), and the liquid crystal (60) generated by the alignment process is provided. 60) The alignment films (16, 26) are aligned so that at least one pitch of the striped liquid crystal alignment unevenness falls within a small pixel width that is not visible among the plurality of pixels (A). A liquid crystal cell characterized by the above-mentioned. 2. The liquid crystal cell according to claim 1, wherein the small pixel width that cannot be seen is within two pixels. 3. The electrode substrate according to claim 1, wherein
0) is fixed on the stage (72), and the electrode substrate (1) is fixed.
The rubbing roller (70) is disposed so as to face the alignment film (16, 26) of (0, 20), and at least one pitch of the striped liquid crystal alignment unevenness of the liquid crystal (60) generated by the alignment processing. The stage (72) and the rubbing roller (70) so that the relative speed between the stage (72) and the rubbing roller (70) is within a small pixel width that cannot be seen out of the plurality of pixels (A). (70) An alignment treatment method for a liquid crystal cell, wherein the alignment treatment is performed by driving at least one of the above. 4. The method according to claim 3, wherein the invisible minute pixel width is within two pixel widths. 5. The rubbing roller (70) and the stage (72) are inclined relative to each other by a predetermined angle (θ) with respect to the rubbing direction.
Or the alignment treatment method for a liquid crystal cell according to 4.