JPH06130396A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To provide the liquid crystal display element for a high-quality display which can reduce the complexity of a manufacture process, improves the productivity, and also improves the combination precision. CONSTITUTION:The liquid crystal display element 10 is constituted by sandwiching a liquid crystal layer 30 between 1st and 2nd substrates 11 and 21 which has electrodes 12 and 22 on their surfaces and are installed having the electrodes 12 and 22 confronted with each other; when the angle (pretilt angle) to make between liquid crystal molecules of the liquid crystal layer 30 on the substrate surface and the substrate surface is defined as alpha, a liquid crystal orienting film 13 which has orienting ability with alpha1 is formed on the surface of the 1st substrate and a liquid crystal orienting surface 25 which has orienting ability to be varied to alpha2 from alpha and a liquid crystal orienting surface 24 which has orienting ability to be varied to alpha3 from alpha are formed on the surface of the 2nd substrate, and the relation between the pretilt angles are alpha2>alpha1>alpha3.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a liquid crystal display device,
In particular, it relates to the molecular alignment state of the liquid crystal layer.

[0002]

2. Description of the Related Art Due to the advantages of thinness, light weight and low power consumption,
Liquid crystal display devices are being used in place of cathode ray tubes as display devices for office automation equipment such as word processors and personal computers. Typical liquid crystal display methods are an optical rotation mode and a birefringence mode.

A liquid crystal display element in the optical rotation mode is, for example, 90
° Twisted nematic (TN) type liquid crystal with twisted molecular arrangement. In principle, it is a black and white display and has a high contrast ratio. Because it's relatively fast,
It is applied to full-color display liquid crystal televisions, OA devices, etc. by using simple matrix drive or active matrix drive having a switching element for each pixel, in combination with TFTs, MIMs, and color filters.

On the other hand, a birefringence mode display type liquid crystal display device is generally a super twist (ST) type liquid crystal having a molecular arrangement in which liquid crystal molecules between substrates are twisted by 90 ° or more and has steep electro-optical characteristics. Even with a simple matrix electrode structure in which a switching element is not provided for each pixel, a large capacity display can be easily obtained by time division driving.

However, these liquid crystal display elements are
There is a viewing angle dependency that the contrast ratio and the display color change depending on the viewing angle and direction. Various techniques have been proposed to improve the viewing angle dependence of the liquid crystal display device. Among them are Young (KH Yang, 1991, IDRC, p
68) proposed method of improving the viewing angle dependence by using a liquid crystal display element in which two regions in which the rising directions of liquid crystal molecules are different by 180 ° are provided in one pixel (Two Domain TN: T
DTN), or as a method of achieving this method by rubbing in one direction on the same substrate, domain division TN (Y. Koike, et al.) Characterized by providing two regions with different pretilts in one pixel. 1992, SID p798, referred to as DDTN) has recently been proposed for dividing one pixel into two regions having different molecular arrangements.

In the case of TDTN as a means for changing the alignment direction of liquid crystal molecules in the same plane, these liquid crystal display elements perform alignment treatment by carrying out multiple rubbing on a layer coated with polyimide through a mask. . On the other hand, in the case of DDTN, after forming an alignment film, another alignment film is formed on the alignment film, the upper alignment film is provided on half of one pixel by photolithography, and the blunt tilt angle is obtained by rubbing once. We are creating different areas.

[0007]

However, the conventional improvement of the viewing angle based on these principles is that the first substrate 1 and the second substrate 2 are formed within one pixel as shown in FIGS. 5B and 5C.
Both have two kinds of liquid crystal alignment capabilities, for example, liquid crystal alignment films 3 and 4 having pretilt angles α2 and α3, which are angles formed by the liquid crystal molecules on the substrate surface, and the liquid crystal alignment films facing each other. Since there is a difference, there is a problem in the manufacturing process.

That is, in the manufacturing process, since the liquid crystal alignment films having two kinds of liquid crystal alignment ability are formed on both the first and second substrates, the number of processes is increased and the substrate and the two kinds of liquid crystal alignment films are formed. Since the alignment accuracy is involved, there is a problem that many errors are included.

The present invention solves the above inconvenience.

[0010]

DISCLOSURE OF THE INVENTION The present invention provides a liquid crystal display device in which a liquid crystal composition is sandwiched between first and second substrates having electrodes on their surfaces so that the electrodes face each other. In the above, when the angle (pretilt angle) formed by the liquid crystal molecules on the surface of the substrate and the surface of the substrate is α, the first substrate surface has a liquid crystal alignment surface having an alignment ability such that α becomes α1. A liquid crystal alignment surface having an alignment ability with α of α2 and a liquid crystal alignment surface with an alignment ability of α of α3, and α2>α1> α3. A display element is obtained. Here, the liquid crystal alignment surface is a surface that controls the alignment of liquid crystal molecules, and is actually determined by the type of liquid crystal alignment film.

Further, a liquid crystal alignment film having an alignment ability with a pretilt angle of α2 within one pixel on the second substrate,
A liquid crystal display device having a liquid crystal alignment film having an alignment ability with a pretilt angle of α3.

[0012]

The present invention achieves the above object, and the principle and method of achieving the same will be described below with reference to the drawings. As shown in FIGS. 5 (b) and 5 (c), the conventional TDTN
In the method of DDTN or DDTN, since two kinds of liquid crystal alignment films 3 and 4 are formed on each of the first and second substrates 1 and 2 in one pixel, the manufacturing process becomes complicated, and the substrate and the two kinds of liquid crystals are formed. Since there is a relation between the alignment accuracy with the alignment film and the alignment accuracy with the first and second substrates, there is a problem that the assembly accuracy also decreases.

The present invention, as shown in FIG.
The manufacturing process is simplified by using one type of liquid crystal alignment film 5 on the substrate 1 and using two types of liquid crystal alignment films 6 and 7 on the second substrate 2. As a result, the alignment accuracy of the first and second substrates is also improved. At this time, as shown in FIG. 5A, a liquid crystal alignment film 5 having an alignment ability such that the pretilt angle α of the liquid crystal 8 becomes α1 is provided on the surface of the substrate 1, and the pretilt angle α is provided on the surface of the second substrate 2. There is a liquid crystal alignment film 6 having an alignment ability with α of α2 and a liquid crystal alignment film 7 with α of α3, and α2>α1> α3. By setting each pretilt α1 of the upper substrate to an intermediate value between α2 and α3 of the alignment film of the lower substrate, the same effect as that of the conventional DDTN is exhibited. As described above, the effect of the invention is obtained by using three kinds of alignment films having different liquid crystal alignment ability. Further, by forming the configuration in one pixel, the conventional DDTN can be obtained.
You get the same effect as.

[0014]

EXAMPLES Examples of the present invention will be described below.

(Embodiment 1) FIGS. 1 to 3 show an embodiment in which the present invention is applied to matrix display. As shown in FIGS. 1 and 2, an upper substrate 11 made of glass on which a transparent common electrode 12 is formed and a lower substrate 21 made of glass on which a pixel electrode 22 and a TFT driving element 23 are formed are prepared. The pixel electrode 22 is an IT with a pixel size of 110 × 330 μm.
It consists of an O electrode. As the liquid crystal alignment film 13, a polyimide (SE-731) having a tilt angle (α1) of 5 ° is formed on the upper substrate 11.
1, manufactured by Nissan Kagaku Co., Ltd.) by a printing method to a uniform thickness of 850 Å.

On the substrate 21, a polyimide (AL-10) having a pretilt angle (α3) of 3 ° was formed as the first liquid crystal alignment film 24.
51, made of Japan Synthetic Rubber) and the second liquid crystal alignment film 25 is polyimide (SE-72) having a pretilt angle (α2) of 7 °.
10, manufactured by NISSAN CHEMICAL CO., LTD., And each pixel electrode is divided into a region A and a region B, and the electrodes are alternately arranged in stripes at 850.
It is formed to a thickness of angstrom by a printing method. Here, the pretilt angle is an angle α formed between the liquid crystal molecules on the substrate surface and the substrate surface, and has a relationship of α2>α1> α3. That is,
Α1 of the liquid crystal alignment film 13 of the upper substrate 11 is 2 of the lower substrate.
It is selected to be an intermediate value of α of the seed alignment film.

The substrates 11 and 21 thus obtained are subjected to rubbing alignment treatment on the polyimide liquid crystal alignment film so that the liquid crystal molecules are twisted by 90 °, and are arranged with the alignment film on the inside through a space, A liquid crystal cell 10 was obtained by sealing with a sealant. The liquid crystal (ZLI-113
2, manufactured by E. Merck) was injected to form a liquid crystal layer 30, and a liquid crystal display device was prepared. At this time, in this embodiment, each pixel is
Different liquid crystal alignment films 2 on regions A and B that divide the pixel electrode into two.
Since 4 and 25 give two kinds of orientation directions to the liquid crystal molecules, a discriminating line is generated at the boundary where these orientations are in contact with each other. The black matrix line 26 is printed and arranged in advance.

When the liquid crystal orientation of this liquid crystal display element was examined, a uniform orientation of 90 ° twist was obtained.
When this liquid crystal display device was driven and the viewing angle dependence of the contrast was measured, as shown in FIG. 3, almost uniform high-quality display was obtained in all directions.

Example 2 An upper substrate having the same structure as that of Example 1 was used, and a liquid crystal alignment film in the lower substrate of Example 1 was formed on the lower substrate as follows. That is, after the electrode surface of the lower substrate is hydrophilically treated with a silane coupling agent, only the region B of the regions A and B that divides the pixel electrode into two regions is used as a liquid crystal alignment film of polyimide (SE) having a pretilt angle α2 of 5 °. -7311, manufactured by Nissan Kagaku) by printing method 850
It was formed to a thickness of angstrom.

The pretilt angle α3 of the region A of the treated surface of the silane coupling agent is approximately 0 °, and the region B coated with the alignment film is
The lower substrate having α3 of 5 ° is completed. Others are Example 1
Is the same as.

The two substrates thus obtained are rubbed in the same direction on the upper and lower substrates so that a splay alignment in which liquid crystal molecules are not twisted is formed on the liquid crystal alignment film of polyimide, and spacers are provided with the alignment films inside. The liquid crystal cell was placed through the above and sealed with a sealant. A liquid crystal having a birefringence anisotropy Δn of 0.0625 (ZLI-16
95, manufactured by E. Merck), and the liquid crystal layer thickness d is 4.0.
A μm liquid crystal display device was obtained.

When this element was driven, the viewing angle dependency was improved and the contrast was high, and good display was obtained.

(Embodiment 3) In this embodiment, the present invention is applied to a color liquid crystal display device. As shown in FIG. 4, red R, green G, and blue B are arranged horizontally on a lower substrate. Electrode set 4
One pixel is configured as 0, and these pixels are arranged in a matrix to display a color liquid crystal. As the liquid crystal alignment film, the upper substrate is made of polyimide (S1) having a tilt angle (α1) of 5 °.
E-7311, manufactured by Nissan Kagaku Co., Ltd.) is applied and formed uniformly by a printing method to a thickness of 850 Å.

On the lower substrate, a polyimide (AL-105) having a pretilt angle (α3) of 3 ° is used as the first liquid crystal alignment film 24 so that the pixels are horizontally divided into lines.
1. Polyimide having a pretilt angle (α2) of 7 ° as the second liquid crystal alignment film 25 (SE-721).
0, manufactured by Nissan Kagaku Co., Ltd., alternately adjacent to each other in a striped pattern 8
It is formed to a thickness of 50 Å by printing.

A rubbing alignment treatment is performed on the thus obtained substrate so that the liquid crystal molecules are twisted by 90 ° on the polyimide liquid crystal alignment film, and the alignment film is placed inside with a space provided between the polyimide liquid crystal alignment film and the sealant. Then, a liquid crystal cell was obtained by sealing. A liquid crystal (ZLI-1132, manufactured by E. Merck) was injected into this liquid crystal cell to form a liquid crystal layer, and a liquid crystal display element was prepared.

When the liquid crystal orientation of this liquid crystal display element was examined, a uniform orientation of 90 ° twist was obtained.
When this liquid crystal display device was driven, the viewing angle dependency was improved, and the contrast was high and good display was obtained.

[0027]

According to the present invention, the conventional TDTN or DD
The complexity of the manufacturing process, which is a problem in TN, can be reduced, and the productivity is improved. Further, since the combination accuracy is also improved, it is possible to provide a high quality liquid crystal display device. In addition, although the present invention has been described in the above embodiment with respect to the element using the TFT, as the driving means, the active matrix driving using the MIM and the multiplex driving based on the simple matrix electrode structure not using the switching element are excellent. Needless to say,
Even when applied to a GH mode liquid crystal display device in which a dye is added to these, excellent effects can be obtained.

[Brief description of drawings]

FIG. 1 illustrates an embodiment of the present invention, and FIG.
-A sectional view taken along the line I and viewed in the direction of the arrow,

FIG. 2 is a partial plan view illustrating an embodiment of the present invention,

FIG. 3 is a curve diagram showing the iso-contrast ratio characteristic of the first embodiment,

FIG. 4 is a partial plan view illustrating another embodiment of the present invention,

5A and 5B are diagrams for explaining the action of the present invention, in which FIG. 5A is a schematic diagram illustrating the action of the present invention, and FIGS. 5B and 5C are schematic diagrams illustrating a conventional action for comparison with the present invention. .

[Explanation of symbols]

 11 ... Upper substrate, 12 ... Electrode, 13 ... Liquid crystal alignment film (pretilt angle α1) 21 ... Lower substrate, 22 ... Pixel electrode, 23 ... TFT drive element, 24 ... First liquid crystal alignment film (pretilt α3), 25 ... Second liquid crystal alignment film (pretilt each α2), 30 ... Liquid crystal layer

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[Procedure amendment]

[Submission date] February 3, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

The present invention, as shown in FIG.
The manufacturing process is simplified by using one type of liquid crystal alignment film 5 on the substrate 1 and using two types of liquid crystal alignment films 6 and 7 on the second substrate 2. As a result, the alignment accuracy of the first and second substrates is also improved. At this time, as shown in FIG. 5A, a liquid crystal alignment film 5 having an alignment ability such that the pretilt angle α of the liquid crystal 8 becomes α1 is provided on the surface of the substrate 1, and the pretilt angle α is provided on the surface of the second substrate 2. There is a liquid crystal alignment film 6 having an alignment ability with α of α2 and a liquid crystal alignment film 7 with α of α3, and α2>α1> α3. By setting the pretilt angle α1 of the upper substrate to an intermediate value between α2 and α3 of the alignment film of the lower substrate, the same effect as that of the conventional DDTN is exhibited. Thus, the effect of the present invention is obtained by using three kinds of alignment films having different liquid crystal alignment capabilities. Further, by forming the above configuration in one pixel, the conventional DDTN can be obtained.
You get the same effect as.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

Example 2 As a liquid crystal alignment film on the upper substrate
Polyimide with a pretilt angle (α1) of 3 ° (AL-10
51, made by Japan Synthetic Rubber) , the liquid crystal alignment film in the lower substrate of Example 1 was manufactured on the lower substrate as follows.
That is, after the electrode surface of the lower substrate is hydrophilically treated with a silane coupling agent, only the region B of the regions A and B that divides the pixel electrode into two regions has a pretilt angle (α2) as a liquid crystal alignment film.
Of 5 [deg.] (SE-7311, manufactured by Nissan Chemical Industries, Ltd.) was formed to a thickness of 850 angstrom by the printing method.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

The pre-tilt angle (α3) of the region A on the treated surface of the silane coupling agent is almost 0 °, and the lower substrate of the region B coated with the alignment film has the α3 of 5 °. Others are the same as those in the first embodiment.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] Explanation of code

[Correction method] Change

[Correction content]

[Description of Reference Signs] 11 ... Upper substrate, 12 ... Electrode, 13 ... Liquid crystal alignment film (pretilt angle α1) 21 ... Lower substrate, 22 ... Pixel electrode, 23 ... TFT drive element, 24 ... First liquid crystal alignment film ( Pretilt angle α3), 25 ... Second liquid crystal alignment film (pretilt angle α2), 30 ... Liquid crystal layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Hato 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa Incorporated company Toshiba Yokohama Office

Claims (2)

[Claims] 1. A liquid crystal display device comprising a liquid crystal layer sandwiched between first and second substrates each having an electrode on the surface so that the electrodes face each other. Angle between molecule and substrate surface (pretilt angle)
Where α is α, the first substrate surface has a liquid crystal alignment surface having an alignment ability with α being α1, and the second substrate surface has a liquid crystal alignment surface having an alignment ability with α being α2. And α
Has a liquid crystal orientation plane with an orientation ability of α3, and
A liquid crystal display device characterized in that the relationship of these pretilt angles is α2>α1> α3. 2. A liquid crystal alignment film having an alignment ability of α2 and a liquid crystal alignment film having an alignment ability of α3 to α3 are provided in one pixel on the second substrate.
The liquid crystal display element described.