JPH06337419A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To divide orientation in the almost equal division ratio without carrying out troublesome alignment. CONSTITUTION:A picture element electrode 24 at a constant picture element pitch and an orientation film 26 are arranged on one substrate of the first and the second substrates 16 and 18 while including liquid crystal 20 inserted between the first and the second opposed substrates 16 and 18, and a common electrode 21 and an oriented film 22 are arranged on the other substrate of the first and the second substrates 16 and 18, and the oriented film 26 of at least one substrate of the first and the second substrates 16 and 18 is composed of a lower layer side orientation material layer 51 and an upper layer side orientation material layer 53, and the lower layer side orientation material layer 51 is formed flatly over the whole surface, and the upper layer side orientation material layer 53 is formed at a pitch of not more than 1/4 of a picture element pitch.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device in which the alignment state of liquid crystal is made different for each minute region (alignment division).

[0002]

2. Description of the Related Art A liquid crystal display device comprises a liquid crystal panel in which liquid crystal is inserted between a pair of transparent glass substrates facing each other.
A common electrode and an alignment film are provided on the inner surface of one glass substrate, and a pixel electrode and an alignment film are provided on the inner surface of the other substrate. Further, an active matrix circuit is formed simultaneously with the pixel electrodes on the latter substrate. Further, a polarizing plate is provided on the outside of each of these substrates. Normal,
These polarizing plates are arranged such that the transmission axes of polarized light are orthogonal to each other. The following description will be made by taking the normally white mode as an example, but it goes without saying that technically similar ones are also applied to the normally black mode (parallel to the polarizing plate).

In a liquid crystal display device, liquid crystal molecules are aligned and pretilt in accordance with the rubbing directions of the alignment films on both substrates.
In a twisted nematic liquid crystal display device in which polarizing plates are arranged orthogonally, the rubbing directions of the alignment films on both substrates are substantially perpendicular to each other, and the liquid crystal molecules spiral from one substrate to the other. Twist. In the normally white mode in which the polarizing plates are arranged orthogonally, white display is obtained when no voltage is applied, and the liquid crystal rises when voltage is applied to obtain black display. In this way, an image with bright and dark contrast as a whole is formed while controlling the voltage applied to the liquid crystal.

In the liquid crystal display device, the contrast of light and dark of the image changes depending on the direction in which the viewer looks at the screen. This is generally recognized as a viewing angle characteristic of a liquid crystal display device. For example, FIG. 6 is a diagram showing the viewing angle characteristics of a liquid crystal display device. A chain line C is a voltage-transmittance curve when the liquid crystal display device is viewed from the front. Dashed lines U and L indicate angle 3
3 is a voltage-transmittance curve when viewed from obliquely above and obliquely below 0 degrees. In the case of the broken line L, since the decrease in the transmittance is small even if the voltage is increased, even if an attempt is made to obtain a black display,
The display is relatively bright. In the case of the broken line U, when a slight voltage is applied, the transmittance is significantly reduced, and an image with a large contrast ratio is obtained, but the transmittance is increased again as the voltage is increased, and the correspondence relationship between the voltage and the transmittance is It can be inconvenient to invert and get an intermediate color between white and black.

In order to solve the influence of such viewing angle characteristics, Japanese Patent Laid-Open No. 54-5754 and Japanese Patent Laid-Open No. 63-10 are recommended.
As disclosed in Japanese Patent No. 6624, it is known that two regions having different alignment states of liquid crystals are formed in one pixel (referred to as alignment division). Of the two regions having different alignment states, one region is subjected to the alignment treatment having the characteristics shown in FIG. 6, and the other region is subjected to the alignment treatment having the characteristics opposite to those shown in FIG. Suggest to do. That is, in the other region, the characteristic indicated by the broken line L in FIG. 6 is obtained when the liquid crystal display device is viewed obliquely from above, and the characteristic indicated by the broken line U in FIG. 6 is obtained when viewed from the oblique lower direction. . By such alignment division, the two viewing angle characteristics that are reversed in the vertical direction can be averaged, and the visual characteristics as a whole can be improved.

FIG. 4 is a diagram showing an example of a conventional alignment-divided liquid crystal display device. The liquid crystal display device is one in which liquid crystal 20 is injected between a pair of glass substrates 16 and 18.
A common electrode 21 and an alignment film 22 are formed on the inner surface of one glass substrate 16, and a pixel electrode 24 and an alignment film 26 are formed on the inner surface of the other glass substrate 18. In FIG. 4, 1
The area equivalent to a pixel is divided into two minute areas A and B,
Each of these minute regions A and B is rubbed as shown in FIG.

In FIG. 5, a dashed arrow indicates the rubbing direction of the display surface side substrate (upper substrate) 16, and a solid line arrow indicates the rubbing direction of the light incident side substrate (lower substrate) 18. As a result of such rubbing, liquid crystal molecules in an intermediate position between the substrates 16 and 18 in the respective regions are removed from each other as shown in FIG.
As shown in FIG. 5, the pre-tilt is performed in the minute area A in a direction (arrow U) when the upper substrate 16 is viewed obliquely from above and in the direction (arrow L) when the upper substrate 16 is viewed from obliquely below in the minute area B. is doing.

FIG. 6 shows the viewing angle characteristics when the alignment process corresponding to the minute area A is performed, and the minute area B has the opposite characteristic to the minute area A. Therefore, by arranging the minute area A and the minute area B adjacent to each other,
The characteristic of the solid line I in FIG. 6 is obtained when viewed from an oblique direction.
The characteristics of the solid line I are those obtained by adding the characteristics of the broken line L and the broken line U and dividing by 2, and are close to the characteristics of the alternate long and short dash line C as seen from the normal direction. The viewing angle direction having a low rate is eliminated, and the viewing angle characteristics are improved.

In the orientation-divided liquid crystal display device, as shown in FIG. 5, rubbing in the opposite direction must be performed for every two adjacent minute regions A and B. Such a rubbing process is performed by masking the alignment film by a photolithography process to perform rubbing on each substrate, and then masking another position of the alignment film by a photolithography process to perform rubbing. It was However, since the photolithography process and the rubbing are performed many times in this way, the manufacturing cost increases and the alignment film 2 is formed.
There is a problem that the surfaces of Nos. 2 and 26 are rough and the alignment of the liquid crystal is not stable.

In order to solve such a problem, the applicant of the present application has previously performed only one rubbing on one substrate without photolithography treatment and one photolithography treatment on the other substrate. Later, I proposed that you only have to rub once. FIG. 7 is a diagram showing one of the substrates of such a prior application. In FIG. 7, the alignment film 26 of the substrate 18 has a two-layer structure including an alignment material layer 51 on the lower layer side and an alignment material layer 53 on the upper layer side, and the alignment material layer 5 on the upper layer side.
3 is patterned according to the minute regions A and B.

In FIG. 7, the orientation material layer 53 on the upper layer side is 1
It is formed with a pitch equal to the pixel pitch (that is, the upper alignment material layer 53 extends with a width half the one pixel pitch,
Adjacent gaps or openings of the same width). One pixel pitch is the width of the pixel electrode 24 plus the size of the non-pixel portion. The non-pixel portion is a gap between two adjacent pixel electrodes 24. In one example, one pixel pitch is 0.4 mm, the width of the pixel electrode 24 is 0.3 mm, and the width of the non-pixel portion is 0.1 mm.

[0012]

Therefore, if the upper alignment material layer 53 is formed at a predetermined position with reference to the pixel electrode 24, as shown in FIG. The widths of the formed minute regions A and B are each 0.15 mm on the pixel electrode 24. However, as shown in FIG. 7B, if the upper alignment material layer 53 is formed with a shift, the area ratio between the upper alignment material layer 53 and the opening adjacent to it is the Up to 1: 2 on 24.
Thus, even if the division ratio is uniform within one pixel pitch, if the position of the alignment layer 53 on the upper layer side is deviated, the alignment division ratio will not be uniform within the one pixel electrode 24. When forming the orientation material layer 53, it is necessary to perform alignment. There is a problem in that the positioning of the members having minute dimensions is troublesome, and an automatic recognition device for performing the positioning is necessary.

It is an object of the present invention to provide a liquid crystal display device capable of performing alignment division at a substantially equal division ratio without complicated alignment.

[0014]

A liquid crystal display device according to the present invention includes a liquid crystal 20 inserted between first and second opposing substrates 16 and 18, and one of the first and second substrates is provided. The pixel electrode 24 and the alignment film 26 having a constant pixel pitch are provided on the first substrate, and the common electrode 21 and the alignment film 22 are provided on the other substrate of the first and second substrates.
And the alignment film 26 of at least one of the second substrates
Is composed of a lower-layer-side alignment material layer 51 and an upper-layer-side alignment material layer 53, the lower-layer-side alignment material layer 51 is formed over the entire surface, and the upper-layer-side alignment material layer 53 has the pixel pitch of 1/4
It is characterized by being formed at the following pitches.

Further, in another feature, the liquid crystal display device according to the present invention is provided with a first and a second opposed substrate 1.
6 and 18, a liquid crystal 20 is inserted between the first and second substrates, and a pixel electrode 24 having a constant pixel pitch and an alignment film 26 are provided on one of the first and second substrates. Two
The common electrode 21 and the alignment film 22 are provided on the other substrate of the first substrate, and the alignment film 26 of at least one of the first and second substrates has the lower alignment material layer 51 and the upper alignment film. The lower layer side alignment material layer 51 is formed over the entire surface in a solid manner, and the upper layer side alignment material layer 53 is formed at a pitch substantially equal to the size of the non-pixel portion within the pixel pitch. It is characterized by being

[0016]

In the above structure, the upper alignment layer 5 is formed.
Regardless of the position of position 3, the area ratio of the upper orientation material layer 53 on the pixel electrode and the opening adjacent thereto is considerably equalized. Therefore, it is not necessary to accurately align the upper alignment material layer 53 with the pixel electrode 24, and the manufacturing process is simplified. (That is, it can be realized by the printing method)

[0017]

1 and 3, a liquid crystal display device includes a liquid crystal panel 10, and polarizing plates (not shown) are arranged on both sides of the liquid crystal panel 10. The polarizing plates are arranged in a vertical relationship in the normally white mode and in a parallel relationship in the normally black mode. The liquid crystal panel 10 is one in which a liquid crystal 20 is sealed between a pair of transparent glass substrates 16 and 18. The liquid crystal 20 is a twisted nematic liquid crystal. Light from a light source (not shown) enters the liquid crystal panel 10 from the direction of the arrow P, and the viewer views the liquid crystal panel 10 from the direction opposite to the incident direction.
In the following description, the substrate 16 on the light incident side will be referred to as the lower substrate, and the substrate 18 on the viewer side will be referred to as the upper substrate.

The color filter layer 1 is formed on the inner surface of the upper substrate 16.
9, the ITO common electrode 21 and the alignment film 22 are provided,
A pixel electrode 24 and an alignment film 26 are provided on the inner surface of the lower substrate 18. An active matrix circuit is provided on the lower substrate 18 at the same time as the pixel electrodes 24. As shown in FIG. 3, the active matrix circuit includes data bus lines 30 and gate bus lines 32 extending vertically and horizontally in a matrix, and the pixel electrode 24 is a thin film transistor (TF).
T) 34, and is connected to the data bus line 30 and the gate bus line 32.

As shown in FIG. 1, one alignment film 22 is formed.
Is formed over the entire surface, and the other alignment film 26
Has a two-layer structure including a lower-layer-side orientation material layer 51 and an upper-layer-side orientation material layer 53, which are stacked. The lower orientation material layer 51 and the upper orientation material layer 53 are made of materials having different pretilts θ ₁ and θ ₂ when the same rubbing is performed. The lower orientation material layer 51 is made of, for example, an inorganic orientation material such as SiO ₂ / TiO ₂ , and the upper orientation material layer 53 is made of an organic orientation material such as polyimide having an imidization ratio of 100%. A part of the upper alignment material layer 53 is a minute region A that is divided by alignment, and an opening adjacent to the upper alignment material layer 53 is a small region B. Further, the alignment film 22 on the upper substrate 16 is subjected to alignment treatment so that the alignment direction and the pretilt φ are substantially constant. The pretilts of the liquid crystal molecules in contact with the alignment films 22 and 26 of the upper and lower substrates 16 and 16 satisfy the relationship of θ ₁ >φ> θ ₂ .

Therefore, in the minute region B, the pretilt angle θ ₁ on the lower substrate 18 side is larger than the pretilt angle φ on the upper substrate 16 side, and the liquid crystal molecules are mainly aligned according to the larger pretilt angle θ ₁ . Therefore, if the upper alignment material layer 53 on the lower substrate 18 side is rubbed according to the solid arrow in the region B of FIG. 5, the rubbing direction of the alignment film 22 on the upper substrate 16 side is the broken arrow of the region B in FIG. 4 does not follow the above, the alignment direction of the liquid crystal molecules in the region B of FIG. 1 rises to the right similarly to the alignment direction of the liquid crystal molecules in the region B of FIG.

Similarly, in the minute region A, the pretilt angle φ on the upper substrate 16 side is larger than the pretilt angle θ ₂ on the lower substrate 18 side, and the liquid crystal molecules are mainly aligned according to the larger pretilt angle θ _2. So the upper substrate 1
If the alignment film 22 on the 6 side is rubbed according to the broken line arrow in the region A in FIG. 5, the alignment material layer 51 on the lower layer side on the lower substrate 18 side is formed.
5 does not follow the solid line arrow in the region A of FIG. 5, the alignment direction of the liquid crystal molecules in the region A of FIG. 1 rises to the left similarly to the alignment direction of the liquid crystal molecules in the region A of FIG. become. Thus, the liquid crystal display device of FIG. 1 has the same orientation division as that shown in FIGS. 4 and 5.

Further, as a feature of the present invention, as shown in FIG. 1, the alignment material layer 53 on the upper layer side has a 1 pixel pitch.
It is formed with a pitch of / 4 or less. That is, four or more upper alignment material layers 53 having a relatively narrow width are provided between corresponding one ends of two adjacent pixel electrodes 24.
Therefore, four or more sets of alignment division regions A within one pixel pitch,
There will be B. Further, the alignment material layer 53 on the upper layer side (therefore, the alignment division regions A and B) is the gate bus line 32.
It is formed in a stripe shape in parallel with.

FIG. 8 is a diagram showing an example in which the upper alignment material layer 53 is formed at a pitch of ¼ of one pixel pitch.
In this example, the orientation material layer 53 on the upper layer side is 1 / pixel pitch of 1 pixel.
This is a typical example in the case of forming at a pitch of 4 or less, and even if the position of the alignment material layer 53 on the upper layer side is deviated from the pixel electrode 24, the area ratio of the alignment division regions A and B is considerably equal. It turns out that it can be transformed. In FIG. 8 also, the pitch of one pixel is 0.4 mm, the width of the pixel electrode 24 is 0.3 mm, and the width of the non-pixel portion is 0.1 mm.

As shown in FIG. 8A, if the upper alignment material layer 53 is formed at a predetermined position with respect to the pixel electrode 24, the minute regions A and B which are divided by the alignment are formed. The total width of the above is 0.15 mm on the pixel electrode 24. As shown in FIG. 8B, even if the upper alignment material layer 53 is formed deviated, the total width of the alignment-divided minute regions A and B is 0 on the pixel electrode 24. 0.15 mm each.

Comparing the configuration of FIG. 7 and the configuration of FIG. 8, only a part of the three upper alignment material layers 53 is placed on the pixel electrode 24 in FIG. 7B. In contrast to the unbalanced orientation division ratio due to the approaching opening, in FIG. 8, three alignment material layers 53 on the upper layer side and three openings are almost on the pixel electrode 24. Yes, the orientation division ratio is balanced. Thus, the alignment layer 53 on the upper layer side
Are formed at a pitch of ¼ or less of one pixel pitch, the area ratio between the alignment division regions A and B can be considerably equalized.

Further, in FIG. 8, the alignment material layer 53 on the upper side is formed.
Are formed at a pitch substantially equal to the size of the non-pixel portion within one pixel pitch. That is, the width of the upper alignment layer 53 in FIG. 8 is half the width of the gap between two adjacent pixel electrodes 24. Therefore, for example, the alignment material layer 53 on the upper side of the left end portion of FIG. 8 is always in the non-pixel state both in the position of FIG. 8A and in the position of FIG. 8B. Therefore, the orientation area ratio does not change depending on the position of the orientation material layer 53 on the upper side of the left end portion.

FIG. 2 is a diagram showing a manufacturing process of the liquid crystal panel 10 of FIG. As shown in the left part of FIG. 2, the upper substrate 16 is rubbed in the direction indicated by the arrow X after applying the common electrode 21 and the alignment film 22. Regarding the alignment film 26 of the lower substrate 18, the pixel electrode 24 and the active matrix circuit are formed, the lower alignment material layer 51 is applied thereon, and then the upper alignment material layer 53 is formed in a predetermined pattern.

The upper alignment layer 53 can be formed by a printing method or a photolithography method. In the former case, the upper alignment material layer 53 is printed on the lower alignment material layer 51 in a predetermined pattern. In the latter case, the upper alignment material layer 53 is applied over the entire surface of the lower alignment material layer 51, and then, for example, a positive photoresist is applied, and the resist is developed into a predetermined pattern. Using the remaining resist as a mask, the upper alignment material layer 53 is etched, and finally the resist is peeled off. The upper alignment material layer 53 made of polyimide is easily dissolved in the alkaline etching solution, but the lower alignment material layer 51 is not dissolved in the etching solution.

As shown in the lower right part of FIG. 2, after patterning the upper alignment material layer 53, the lower alignment material layer 51 and the upper alignment material layer 53 are simultaneously rubbed in the direction of arrow Y. . Alignment material layer 53 on the upper layer side, and alignment material layer 5 on the lower layer side exposed from the opening of the alignment material layer 53 on the upper layer side
1 is rubbed in the same direction. However, the angles of the pretilts θ ₁ and θ ₂ differ depending on whether the liquid crystal molecules are in contact with the upper alignment material layer 53 or the lower alignment material layer 51. The relationship between the rubbing directions X and Y is also shown in FIG. 3, for example.

Examples of inorganic oriented materials suitable for the lower oriented material layer 51 include AL1054 manufactured by Japan Synthetic Rubber and AT-LO28 manufactured by Nissan Kagaku, which have a pretilt θ ₂
Is about once. Examples of high pretilt type polyimide suitable for the upper alignment layer 53 include JALS246 and 214 made by Japan Synthetic Rubber. This is the pretilt θ
₁ is more than 5 degrees. Then, the alignment film 22 of the upper substrate 16
As an example of a medium pretilt type polyimide suitable for
There is JALS219 made by Japan Synthetic Rubber, which has a pretilt φ of about 1 to 5 degrees.

The selected orientation material has a constant pretilt due to the substantially constant rubbing method, but the pretilt also changes when the rubbing method changes. For example, if the rubbing is relatively light, the pretilt becomes relatively large,
The pretilt becomes relatively small when the rubbing is performed strongly (pressing strongly, performing many times, performing rubbing quickly, etc.). Since a reproducible relationship is experimentally determined between the rubbing method and the pretilt, the pretilt depending on the rubbing method using the alignment material layer 53 on the upper side of the lower substrate 18 and the alignment film 22 of the upper substrate 16 as the same material. You can also make a difference.

[0032]

As described above, according to the present invention,
It is possible to save the labor of alignment in the alignment division process, and obtain a liquid crystal display device having excellent viewing angle characteristics and contrast.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing the alignment treatment of FIG.

FIG. 3 is a partial cross-sectional plan view of the lower substrate of FIG.

FIG. 4 is a diagram showing a conventional technique.

FIG. 5 is a diagram showing a rubbing process for alignment division.

FIG. 6 is a diagram showing viewing angle characteristics of a liquid crystal display device.

7A and 7B are diagrams showing an example of performing pixel division by an alignment film having a two-layer structure, FIG. 7A is a diagram showing a case where an upper alignment material layer is in a predetermined position, and FIG. 7B is a top layer side. It is a figure which shows the case where the orientation material layer of FIG.

FIG. 8 is a diagram showing an example of performing pixel division by an alignment film having a two-layer structure according to the present invention, (A) showing a case where an upper alignment material layer is in a predetermined position, (B) [Fig. 6] is a diagram showing a case where the upper alignment material layer is displaced.

[Explanation of symbols]

 16, 18 ... Substrate 20 ... Liquid crystal 21 ... Common electrode 22, 26 ... Alignment film 24 ... Pixel electrode 51 ... Alignment material layer on lower layer 53 ... Alignment material layer on upper layer side

Claims (5)

[Claims] 1. A first and a second opposing substrate (16, 1).
8) includes a liquid crystal (20) inserted between the first and second substrates, and one of the first and second substrates is provided with a pixel electrode (24) and an alignment film (26) having a constant pixel pitch, and The first
A common electrode (21) and an alignment film (22) are provided on the other substrate of the first and second substrates, and the alignment film (26) of at least one of the first and second substrates is on the lower layer side. An orientation material layer (51) and an upper orientation material layer (53),
The lower alignment layer (51) is formed on the entire surface in a solid manner,
The orientation material layer (53) on the upper layer side is 1/4 of the pixel pitch.
A liquid crystal display device characterized by being formed at the following pitches. 2. An alignment material layer (53) on the upper side of an alignment film (26) of at least one of the first and second substrates.
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is formed in a stripe shape. 3. The liquid crystal display device according to claim 1, wherein an alignment film (22) of the other substrate of the first and second substrates is formed over the entire surface in a solid manner. 4. The alignment material layer (51) on the lower layer side and the alignment material layer (53) on the upper layer side of the alignment film (26) of at least one of the first and second substrates are arranged in a liquid crystal alignment direction. Of the same size and different pretilts (θ ₁ , θ ₂ ) from each other to form first and second adjacent minute regions (A, B), and the alignment film (26) of the other substrate has an alignment direction and a pretilt (26). (Φ)
Are substantially the same, and there is a relationship of θ ₁ >φ> θ ₂ , the liquid crystal display device according to claim 3. 5. First and second opposing substrates (16, 1)
8) includes a liquid crystal (20) inserted between the first and second substrates, and one of the first and second substrates is provided with a pixel electrode (24) and an alignment film (26) having a constant pixel pitch, and The first
A common electrode (21) and an alignment film (22) are provided on the other substrate of the first and second substrates, and the alignment film (26) of at least one of the first and second substrates is on the lower layer side. An orientation material layer (51) and an upper orientation material layer (53),
The lower alignment layer (51) is formed on the entire surface in a solid manner,
A liquid crystal display device, wherein the alignment layer (53) on the upper layer side is formed at a pitch substantially equal to the size of the non-pixel portion in the pixel pitch.