JPH05281558A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To provide a liquid crystal display element realizing all of uniformity of base spacing, high numerical aperture and high display quality without using special material, especially a TN-type or STN-type liquid crystal display element. CONSTITUTION:A pair of bases 1, 5 with electrodes and orientation films 3, 8 formed at the mutually opposed surface are held at a specified space apart through seals provided at the peripheral edge parts of the bases and a spacer 4 provided at a display part, and a liquid crystal 9 is filled between the bases to form a liquid crystal display element. In this liquid crystal display element, the side face of the spacer 4 possesses liquid crystal orientation capacity.

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, and more particularly to a liquid crystal display device of twisted nematic display system or super twisted nematic display system.

[0002]

2. Description of the Related Art A liquid crystal display device generally comprises a pair of substrates each having an electrode and an alignment film formed on the surfaces facing each other.
It has a structure in which a liquid crystal is sealed between the substrates, which are held at predetermined intervals via a seal provided on the peripheral portion of the substrate and a spacer provided on the display unit. In such a liquid crystal display element, a voltage is applied to the liquid crystal from the driving electrode provided on the substrate in the display section through the alignment film.

The spacers are used to uniformly define the distance between the substrates in the display section. The substrate interval of the liquid crystal display device is usually set to 1 to 20 μm, and this is ± 0.1
It is necessary to control uniformly with an accuracy of about μm. this is,
If there is a variation in the board spacing, it not only causes the display quality to deteriorate such as color unevenness and interference fringes, but also when the board spacing is narrowed by an external force, the electrodes come into contact with each other, causing circuit damage and display failure. This is because it becomes a generation factor. Thus, the spacer is an important member for maintaining the performance of the liquid crystal display element. As a material of the spacer, an inorganic material such as glass or silica and an organic material such as polystyrene polymer or photosensitive polyimide are used. Conventionally, as a method of forming spacers, a method of spraying particulate spacers and a method of using a photolithography technique are mainly used.

First, a method of manufacturing a liquid crystal display device including a step of spraying particulate spacers, which is the mainstream at present, will be described. One of the substrates on which the electrodes and the alignment film are formed is prepared, and a suspension in which the particulate spacer is suspended in an organic solvent is sprayed on the surface of the alignment film, and then the solvent is volatilized. A liquid crystal cell is formed by combining a substrate on which spacers are scattered and the other substrate on which an electrode and an alignment film are formed and sealing the peripheral edge with a sealing adhesive. After filling the liquid crystal cell with a liquid crystal substance, the injection port is sealed. A member similar to the particulate spacer may be mixed in the sealing adhesive.

However, in this method, it is difficult to control the diameter because the diameter of the spacer to be scattered is extremely small. Further, it is difficult to evenly disperse the spacers, and the spacers may be dispersed in a lump. When spacers are formed, the gap between the substrates becomes uneven,
As described above, the display quality is deteriorated. Further, since this method sprays particles having a size of several μm, it itself becomes a source of dust and is not suitable for work in a clean room.

Therefore, a method developed as an alternative method is a method of forming a spacer by using a photolithography technique. As an example, a method of manufacturing a liquid crystal display element including a step of forming a spacer using a photocurable resin will be described. A photocurable resin layer is formed on the substrate on which the electrodes and the alignment film are formed. After irradiating light through the exposure mask to selectively cure only the exposed portion, an appropriate etching liquid is used to remove the unexposed portion to form a spacer. A liquid crystal cell is formed by combining the electrode and the other substrate on which the alignment film is formed and sealing the peripheral edge with a sealing adhesive. After filling the liquid crystal cell with a liquid crystal substance, the injection port is sealed. A photodegradable resin may be used instead of the photocurable resin. Further, there is also used a method in which a mask material is once formed on the spacer material by a photolithography technique and the spacer material is etched using the mask material as a mask.

According to this method, the spacer can be formed at a specific position. For example, by arranging the spacer only on the non-pixel portion such as on the wiring, it is possible to prevent light leakage due to the spacer.
The display quality is improved. Although the same effect as the photolithography technique can be expected by the method of printing by mixing the spacer with the thermosetting resin, the photolithography technique is inferior in terms of accuracy and miniaturization.

On the other hand, currently widely used liquid crystal display elements are classified into a twisted nematic (TN) type and a super twisted nematic (STN) type according to the alignment state of liquid crystals in the element.

In the TN type, the upper and lower substrates are arranged so that the alignment directions of the alignment films are orthogonal to each other, and the average long-axis direction of the liquid crystal molecules is twisted by 90 ° between the upper and lower substrates. Let At this time, the liquid crystal layer exhibits optical rotation of 90 °.

This display element has a polarization plane parallel to each other.
When sandwiched between a pair of polarizing plates, it is called normally black (NB) display. That is, when no voltage is applied, light is blocked because the liquid crystal layer has optical rotatory power. When a voltage is applied, the liquid crystal stands upright except in the vicinity of the alignment film, and the liquid crystal layer loses its optical rotatory power, so that light is transmitted.
On the other hand, when this display element is sandwiched between two polarizing plates whose polarization planes are orthogonal to each other, a normally white (N
W) called display. In this case, the light is transmitted when the voltage is not applied, and the light is blocked when the voltage is applied. Both polarizing plate arrangements are widely used.

The STN type is basically the same as the TN type, except that the average twist angle of the liquid crystal in the display element in the direction of the major axis of the molecule is about 270 °. By setting this twist angle, the response of the liquid crystal to the voltage application can be speeded up.
However, problems such as difficulty in controlling the substrate spacing also occur.

The TN type was disregarded when the STN type first appeared. However, because of its high image quality, the TN type display system is adopted in many of the liquid crystal display devices by the active matrix system which have been rapidly popularized in recent years, and the importance thereof has been recognized again.

The liquid crystal display device according to these display methods is
There is a tendency for larger areas and higher definition. In particular, for projection type liquid crystal display elements, there is an urgent need for higher definition. To realize this, the pixel pitch is rapidly reduced. Along with this, display quality in the vicinity of the spacer in the pixel portion, more specifically, deterioration of contrast has become a problem. The cause of this contrast reduction is roughly classified into one caused by the spacer itself and one caused by the disorder of the liquid crystal alignment in the vicinity of the spacer.

A cause of the spacer itself is light leakage through the spacer. This is noticeable when displaying NB. As a solution to this problem, a dye is added to the spacer (JP-A-62-66228), the surface of the spacer is dyed (JP-A-1-14021), and the surface of the spacer is metal-plated (JP-A-2-96716).
No.) etc. have been proposed. However, these improvements have a problem that the liquid crystal is contaminated by a light absorbing material such as a dye and the mechanical strength of the spacer is reduced due to the surface modification. Further, it is impossible to eliminate the disorder of the liquid crystal alignment which may reach the same area range as the spacer.

As a solution to the reduction in contrast due to the disorder of the liquid crystal alignment, there is known a technique (Japanese Patent Laid-Open No. 63-32424) in which an alignment film is formed after spacers are dispersed and a rubbing treatment is performed. However, this technique uses a spraying method in which it is difficult to control the spacer density, and the spacers may move and agglomerate during the formation of the alignment film, which may further worsen the variation in the substrate spacing. Further, since the spacer impairs the flatness of the alignment film, defective display due to uneven rubbing occurs.

In order to solve both causes at once, there has been proposed a method of selectively arranging spacers other than pixels. As a typical example, a method of arranging a spacer under a black matrix (JP-A-63-228126), a method of selectively arranging a spacer containing a superconductor other than pixels (JP-A-2-62517), a magnetic material Method for selectively disposing spacers containing helium other than pixels
98421). However, these methods have a problem that they are difficult to put into practical use. For example, JP-A-63
The use of a black matrix such as No. 228126 causes the aperture ratio of the display unit to be extremely reduced as the definition becomes higher. JP-A-2-62517 and JP-A-2-198
In the case of No. 421, a special material is used, which is disadvantageous in terms of cost.

[0017]

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display device, particularly a TN type or STN, which can realize uniform substrate spacing, high aperture ratio and high display quality without using a special material. Type liquid crystal display device.

[0018]

In the liquid crystal display element of the present invention, a pair of substrates having electrodes and an alignment film formed on the surfaces facing each other are used as a seal and a display portion provided on the periphery of the substrates. In a liquid crystal display element in which liquid crystal is sealed between substrates by holding it at predetermined intervals via spacers provided, the side surfaces of the spacers have a liquid crystal aligning ability. In the present invention, it is desirable that the side surface of the spacer has an alignment capability of causing the liquid crystal molecules to be in a state during operation, that is, twisted alignment or vertical alignment. Hereinafter, the spacer constituting the liquid crystal display device of the present invention will be described in more detail.

First, in order to form the spacer according to the present invention in a predetermined shape at a predetermined position, it is generally considered that a printing technique or a photolithography technique is applied. For example, when forming a spacer having a cross-sectional area of 50 μm × 50 μm or more, a printing technique such as offset printing can be used. However, the value of 50 μm is
A spacer having a smaller cross-sectional area is preferable because it reaches half of 100 μm, which is a typical value of the pixel electrode spacing of a 10-inch liquid crystal display element. On the other hand, if the photolithography technique is used, a spacer having a cross-sectional area of several μm square can be formed. In this technique, a photosensitive resin is used as the main constituent of the spacer. As the photosensitive resin,
Examples thereof include polyimide, polyamide, polyvinyl alcohol, polyacrylamide, cyclized rubber, novolac resin, polyester, polyurethane, acrylate resin, bisphenol resin, or gelatin to which photosensitivity is imparted. The photosensitive resin may be a negative type or a positive type. Among these resins, when a negative photosensitive polyimide is used, the most excellent alignment state is obtained, and the controllability of the gap between the substrates is also good.

In the present invention, in order to impart the twist orientation ability to the side surface of the spacer, for example, a method of mechanically producing a twist or a method of utilizing a material which is twist-oriented by itself can be considered.

As a method for mechanically causing the twist,
Using a method of forming spacers made of a resin having excellent elasticity and having a height of several μm at a predetermined position on the substrate by using photolithography technology, stacking and adhering the opposing substrates, and then rotating the opposing substrates. You can In this method, a twisting stress is applied to the spacer to give the side surface the ability to twist the liquid crystal. However, this method can be applied only to a liquid crystal display element having a small display area (specifically, about 3 inches or less) so that the uniformity of the substrate spacing can be guaranteed if there is one spacer in the center of the display section. Is.

On the other hand, the method of using a material in which the spacer itself is twist-oriented as a constituent component of the spacer is more practical. These materials are used by being added to a photosensitive resin which is the main component of the spacer. Examples of such a material include a side chain type polymer liquid crystal substance having a chiral group,
Alternatively, a combination of a side chain type polymer liquid crystal substance and a low molecular weight organic substance having a chiral group may be mentioned. These materials are twisted and aligned by heat-treating for a predetermined time in a temperature range showing a liquid crystal phase. Therefore, the twisted alignment of the liquid crystal molecules is realized by the intermolecular force between the liquid crystal molecules and the constituent components of the twisted aligned spacers. In this case, a liquid crystal phase (chiral nematic phase) is exhibited at a temperature of 100 ° C. or higher, and a solid phase is preferable at a temperature lower than this. A material exhibiting a liquid crystal phase at a temperature of less than 100 ° C. may not serve as a supporting member, but may contaminate a liquid crystal substance. Further, when formed on a substrate having a color filter, it is preferable that the liquid crystal layer exhibits a temperature range of about 200 ° C. or lower. This is because when the heat treatment is performed at a high temperature exceeding 200 ° C., the color filter is significantly deteriorated. The following materials are available as materials satisfying the above temperature conditions. Examples of the side chain type polymer liquid crystal substance having a chiral group include cholesteryl-ω- (4-methacryloyloxyphenylalkanoate) having 2 or 6 alkyl carbon atoms and copolymerized at a polymerization ratio of 1: 1. There are some. Examples of the combination of the side chain type polymer liquid crystal substance and the low molecular weight organic substance having a chiral group include p-
A combination of cyanobiphenyl-4-methacryloyloxybenzoate and S (−)-2-methylbutylmethacrylate may be mentioned.

The heat treatment for imparting the twist orientation ability to the side surface of the spacer is carried out while forming the spacer at a predetermined position of the resin containing the side chain type polymer liquid crystal substance by using a photolithography technique or the like. It may be performed, or may be performed after formation. Further, when the above materials are used, it is desirable that the alignment film is formed in a state of having the liquid crystal alignment ability before forming the spacer. This is because the alignment direction of the side chain of the side chain type polymer liquid crystal substance is regulated by the surface of the alignment film,
This is because the spiral axis due to the twist orientation is in the direction perpendicular to the substrate.

In the present invention, as a method of imparting the vertical alignment ability to the side surface of the spacer, for example, a method of forming fine grooves on the side surface of the spacer, or a method of using a material which is itself vertically aligned as a constituent component of the spacer is used. Can be mentioned.

To form a fine groove on the side surface of the spacer,
The following method is used instead of the photolithography technique. That is, after a resin having a thickness of several μm is formed on a substrate, a mask material is formed at a predetermined position, and this mask material is used as a mask for RIE (Reactive Io).
n Etching), the resin is etched to form spacers having a predetermined shape at predetermined positions, and the side surfaces thereof are processed to form fine grooves. In this method, the liquid crystal molecules can be vertically aligned by the geometrical effect of the spacer side surface.

In the method of using a material that vertically aligns itself as a constituent component of the spacer, a linear polymer liquid crystal substance is used. These materials are also used by being added to the photosensitive resin which is the main component of the spacer. These materials are vertically aligned by heat-treating for a predetermined time in a temperature range showing a liquid crystal phase. Therefore, the vertical alignment of the liquid crystal molecules is realized by the intermolecular force between the constituent components of the vertically aligned spacers and the liquid crystal molecules. It is desirable that such a linear polymer liquid crystal substance also exhibits a liquid crystal phase in the same temperature range as in the case of the side chain polymer liquid crystal substance described above, and examples thereof include Novacurate (trade name of Mitsubishi Kasei). ..

In this case, it is desirable that the alignment film is not formed yet or has no liquid crystal aligning ability. This is because there is a possibility that the alignment of the linear polymer liquid crystal substance in the vertical direction may be disturbed. An external field may be applied in the vertical direction to promote the alignment of the linear polymer liquid crystal substance.

The display system of the liquid crystal display device according to the present invention is not particularly limited. That is, the active matrix type or the simple matrix type display system may be used, and the TN type or ST
It may be N-type, transmissive or reflective. Examples of these liquid crystal display elements will be described with reference to the drawings.

FIG. 8 is an exploded perspective view showing an example of a three-terminal active matrix type transmissive liquid crystal display element using a TN type liquid crystal. In FIG. 8, one glass substrate (T
Pixel electrodes 2 and TFT elements (thin film transistors) 11 are formed in a matrix on an FT array substrate) 1. A plurality of data wirings 2 are provided between each rectangular pixel composed of one pixel electrode 2 and one TFT element 11.
1 and the address wiring 22 are formed orthogonal to each other. The source electrode of the TFT element 11 is connected to the pixel electrode 2, the drain electrode is connected to the data wiring 21, and the gate electrode is connected to the address wiring 22. Such a TFT
An alignment film (not shown) is formed on the surface of the array substrate 1. A color filter 6, a counter electrode 7, and an alignment film (not shown) are sequentially formed on the other glass substrate (counter substrate) 5. A region where the pixel electrode 2 and the counter electrode 7 face each other corresponds to a pixel. These TFT array substrate 1
Between the substrate and the counter substrate 5, a seal is provided at the peripheral portion of the substrate, and a spacer (not shown) according to the present invention is provided at the display portion to define the inter-substrate gap. Then, a liquid crystal material is sealed between both substrates. Furthermore, in the case of transmissive display, TF
A backlight (back lighting) 53 is provided outside the T array substrate 1 via a polarizing plate 51 and a diffusion plate 52, and a polarizing plate 54 is provided outside the counter substrate 5.

In this liquid crystal display element, the pixel electrode 2 and the counter electrode 7 are made of, for example, ITO (Indium Tin).
Oxide), a conductive thin film made of a material such as a metal. In the case of a transmissive display element, IT is used for both electrodes.
A transparent material such as O is used. In the case of a reflective display element, only one of the electrodes needs to be transparent, and usually the counter electrode side is often transparent. Further, in this case, the polarizing plate 51, the diffusion plate 52, and the backlight 53 on the outside of the TFT array substrate 1 are unnecessary.

FIG. 9 is an exploded perspective view showing an example of a simple matrix type liquid crystal display element. In FIG. 9, a plurality of strip-shaped scanning electrodes 31 and an alignment film (not shown) are formed on the surface of one glass substrate 1 in the X-axis direction. On the surface of the other glass substrate (counter substrate) 5, a plurality of strip-shaped display electrodes 32 and an alignment film (not shown) are formed in the Y-axis direction. Scan electrode 31 and display electrode 3
The intersection of 2 corresponds to a pixel. Between the glass substrate 1 and the glass substrate 5, a seal is provided at the peripheral portion of the substrate and a spacer (not shown) according to the present invention is provided at the display portion to define the inter-substrate gap. Then, a liquid crystal material is sealed between both substrates.

The liquid crystal display element according to the present invention includes a transparent electrode made of an ITO film or the like, a TFT, a MIM (Meta).
l Insulator Metal) is formed on the surface of a substrate on which a driving element such as an Insulator Metal is formed by an alignment film and a spacer by the above-described method, and then an assembly process and a liquid crystal injection process are performed. Either of the alignment film and the spacer may be formed first, or they may be formed simultaneously. The formation order is determined in consideration of the convenience of the process and the performance of the display device. For example, when a photosensitive resin is used as the material for the spacer, the photosensitive resin can be pre-baked, exposed, heat-treated again from the substrate side, and then developed to form the spacer and the alignment film at the same time. That is, when the heat treatment is performed after the exposure, the photosensitive resin on the substrate side is polymerized and the dissolution rate in the developing solution is slowed, so that this portion can be left after the development. Therefore, if this portion is oriented, it can be used as an orientation film. If such a method is adopted, the step of independently forming the alignment film becomes unnecessary.

It is preferable that the spacer is formed, for example, at the end of the pixel. Further, in a liquid crystal display element in which a driving element is formed on one substrate, it is preferable to form a spacer in the central recess of the driving element.

[0034]

In the liquid crystal display device of the present invention, the side surfaces of the spacer are relatively flat and have liquid crystal aligning ability, so that liquid crystal molecules can be stably aligned even in the vicinity of the spacer without using a special material. be able to. Therefore, it is possible to prevent the deterioration of contrast due to the disordered alignment of the liquid crystal molecules, and it is possible to improve the display quality.

Further, when a material having a property of orienting itself is used as a constituent component of the spacer, the spacer itself has an optical rotatory property, that is, a light shielding property. Therefore, the amount of light transmitted through the spacer can be suppressed, and even in the case of NB display in which the black level is particularly demanding, without using a black matrix that reduces the aperture ratio,
A high-quality display can be achieved. In this case, if another material that improves the light-shielding property is used together as a constituent component of the spacer,
Greater effect can be expected.

Further, in the liquid crystal display element in which the driving element is formed on one of the substrates, the spacer can be formed in the central concave portion of the driving element to suppress the amount of light applied to the driving element. Therefore, malfunction of the drive element due to excessive light irradiation can be prevented, and the display quality can be further improved. In this case, if the spacer itself has a light shielding property as described above, a greater effect can be expected.

[0037]

Embodiments of the present invention will be described below with reference to the drawings. In the following examples and comparative examples, active matrix type liquid crystal cells using TN type liquid crystal as a liquid crystal display element were prepared and their characteristics were evaluated. Example 1

A spacer forming material was prepared in advance as follows. The method of Finkelmann et al. (Macr
omol. Chem. , 179, 829 (1978))
According to cholesteryl-ω- (4-methacryloyloxyphenylalkanoate), the number of alkyl carbon atoms is 2
Liquid crystal substances of Nos. 6 and 6 were synthesized, and further, these two kinds of liquid crystal substances were copolymerized at a polymerization ratio of 1: 1 to synthesize a side chain type polymer liquid crystal substance. The obtained side chain type polymer liquid crystal substance,
It was added to a solution of photosensitive polyimide (manufactured by Ciba-Geigy, trade name: Probimide 400) to form a spacer forming material.

As shown in FIGS. 1 and 2, one glass substrate (TFT array substrate) 1 on the surface of which display electrodes 2 and TFT elements 11 were formed in a matrix was prepared.
The structure of this TFT element 11 is as follows.
That is, the gate electrode 12, the gate insulating film 13, and the semiconductor layer 14 are sequentially formed on the glass substrate 1. Source and drain regions (not shown) are formed in the semiconductor layer 14. A source electrode 15 and a drain electrode 16 connected to these regions are formed on the semiconductor layer 14. The source electrode 15 is connected to the display electrode 2. The drain electrode 16 is connected to the data line, and the gate electrode 12 is connected to the address line. Figure 2
3, the TFT element 11 is formed at one corner of the display electrode 2, and one display electrode 2 and one TFT element 11 form one pixel of 130 μm × 100 μm.

On this TFT array substrate 1, thermosetting polyimide (manufactured by Japan Synthetic Rubber Co., Ltd., trade name: Optomer AL
After applying the solution of (1051) with a roll coater,
It was dried by heating at 200 ° C. for 1 hour. The surface of this polyimide film was rubbed with a roller equipped with a cloth to form an alignment film 3.

On the alignment film 3, the above-mentioned spacer forming material was spin-coated at 2500 rpm for 25 seconds.
Place the TFT array substrate on a hot plate at 110 ° C for 1
The spacer forming material was pre-baked for 5 minutes. The photomask 10 shown in FIG. 3 is provided at a position 6 μm above the surface of the cured film.
1 was placed. In this photomask 101, the vertical 260
Translucent part 110 having a diameter of 10 μm for every 200 μm
Is formed, and the other portion serves as the light shielding portion 120. In addition, as shown in FIG.
A photomask was aligned so that the light-transmitting portion 110 overlaps with the TFT element 11 of the alternate display electrode 2 at a diagonal position (spacer forming position).

400 mJ / c through this photomask
m² Parallel light was exposed. Curing under pressure with nitrogen gas
Sprinkle developer (QZ3301 made by Ciba-Geigy) on the film
And develop, and then mix the developer and rinse solution (
Gee Co., QZ3311) is sprayed and rinsed
Rinse with baggygie QZ3312)
Spin dry was performed using a raw gas. The development conditions are as follows.
On the street. Nitrogen pressurization 2.5kg / cm²  Developer injection amount 10 ml / min Developer processing time 240 seconds Overlap time 10 seconds Rinse time 10 seconds Nitrogen spin dry time 20 seconds

After the development treatment, the substrate was heated at 200 ° C. for 1 hour to volatilize the solvent. By this heat treatment, the side chain type polymer liquid crystal substance is held in the chiral smectic phase and twisted and aligned. This was allowed to cool to room temperature to form spacers 4.

Next, another glass substrate (counter substrate) 5 having a color filter 6 with a protective film and a counter electrode 7 formed on the surface thereof in order was prepared. A solution of thermosetting polyimide (manufactured by Japan Synthetic Rubber Co., Ltd., trade name: Optomer AL-1051) was applied onto the counter substrate 5 by a roll coater, and then heated at 200 ° C. for 1 hour to be dried. The surface of this polyimide film was rubbed with a cloth-mounted roller to form an alignment film 8. A thermosetting epoxy resin (manufactured by Mitsui Toatsu Co., Ltd., trade name: StructBond) was screen-printed on the peripheral portion of the counter substrate 5 as a sealing material.

The TFT array substrate 1 and the counter substrate 5 are combined so as to face each other, and the temperature is set to 180.degree.
After heating for a period of time, the liquid crystal cell was prepared by cooling to room temperature. This cell was placed in a vacuum chamber, and the nematic liquid crystal composition (ZLI manufactured by Merck & Co., Inc.) was placed inside the cell under vacuum.
-1370) 9 was enclosed. The inlet was sealed with a UV curable adhesive. Further, after washing the cell, polarizing plates were arranged outside the TFT substrate and outside the counter substrate, respectively, so that the vibration planes of the transmitted light were parallel to each other. Example 2

In this embodiment, the formation position of the spacer 4 is different from that of the first embodiment. That is, as shown in FIG.
A spacer 4 was formed in the central recess of the TFT element 11 formed on the TFT array substrate 1. A liquid crystal display device was produced in the same manner as in Example 1 except for this. Example 3

This embodiment differs from the first embodiment in the following.
An alignment film is formed on the TFT array substrate by such a method.
It was The display electrode 2 and the TFT element 11 are arranged on the surface of the matrix.
On the TFT array substrate 1 formed in a stripe shape, a photosensitive poly
Imide (manufactured by Ciba Geigy, trade name: Probimide 40
Spin coat 5% solution of 0) at 3000 rpm for 25 seconds.
I got it. Place the TFT array substrate on the hot plate 11
Pre-bake photosensitive polyimide by heating at 0 ° C for 15 minutes
did. At a position 6 μm above the surface of this cured film, the
The photomask 102 shown in FIG. This photo mass
In the case 102, the 0.2 μm wide transparent portion 110 and 1.0 μm
The light-shielding portion 120 having a width of m is formed in a stripe shape.
It 180mJ / cm through this photomask² Nodaira
After exposure to line light, spray development was performed as in Example 1.
It was. The developing conditions are as follows. Amount of developer jet 10ml / min Nitrogen pressurization 2.5kg / cm²  Developer processing time 60 seconds Overlap time 10 seconds Rinse time 15 seconds Nitrogen spin dry time 10 seconds

After the development treatment, the substrate was heated at 250 ° C. for 1 hour, dried, and allowed to cool to room temperature to form the alignment film 3. A liquid crystal display device was produced in exactly the same manner as in Example 1 except for this step. Example 4 In this example, unlike Examples 1 to 3, spacers were formed on the counter substrate 5.

First, in the same manner as in Example 1, a polyimide film was formed on a TFT array substrate on the surface of which display electrodes and TFT elements were formed, and a rubbing treatment was performed to form an alignment film.

Next, a counter substrate 5 having a color filter 6 with a protective film and a counter electrode 7 formed on its surface was prepared. On this counter substrate, 2000 of a solution of soluble polyimide (manufactured by Ciba-Geigy, trade name: Probimide 200)
After spin coating at rpm for 30 seconds, it was dried by heating at 180 ° C. for 1 hour. A Mo layer having a thickness of 1 μm was formed on the polyimide film by a sputtering method. This Mo layer is photo-etched, and as shown in FIG. 6, a diameter of 10 μm is provided on each corner of every other pixel so as to correspond to the color filter 6.
A mask material made of Mo was formed.

This counter substrate is placed in a vacuum chamber,
After evacuating to a high vacuum, introducing O ₂ gas, Ar ⁺ The polyimide film not masked by the mask material was subjected to reactive ion etching by irradiation with an ion beam. The conditions at this time are as follows. O ₂ gas concentration 1 × 10 ⁻⁴ Torr irradiation intensity 200 W irradiation time 5 minutes

Thus, the spacer and the alignment film having fine grooves in the direction perpendicular to the substrate were simultaneously formed. That is, under the above conditions, the etching of the polyimide film does not reach the substrate surface. Therefore, the remaining thin film portion can be used as an alignment film. Next, after Mo used as a mask material was etched, the alignment film was rubbed with a roller equipped with a cloth. Hereinafter, a liquid crystal display element was produced in the same manner as in Example 1. Example 5

In this embodiment, an alignment film is formed on the TFT array substrate by using a photosensitive resin in the same manner as in Embodiment 3, and a spacer and an alignment film are formed on the counter substrate in the same manner as in Embodiment 4. Formed. Hereinafter, a liquid crystal display element was produced in the same manner as in Example 1. Comparative Example 1

Thermosetting polyimide (manufactured by Nippon Synthetic Rubber Co., Ltd., trade name: Optomer AL) is formed on a TFT array substrate having display electrodes and TFT elements formed in a matrix on the surface.
After applying the solution of (1051) with a roll coater,
It heat-dried at 200 degreeC for 1 hour. The surface of this polyimide film was rubbed with a roller equipped with a cloth to form an alignment film. On this alignment film, a spherical spacer (manufactured by Sekisui Fine Chemical Co., trade name: Micropearl SP-20
The ethanol dispersion of 5) was sprayed.

On the other hand, a thermosetting polyimide (manufactured by Japan Synthetic Rubber Co., Ltd., trade name: Optomer A) is formed on a counter substrate on which a color filter with a protective film and a counter electrode are sequentially formed on the surface.
The solution of L-1051) was applied by a roll coater and then dried by heating at 200 ° C. for 1 hour. The surface of the obtained polyimide film was rubbed with a roller equipped with a cloth to form an alignment film. On this counter substrate, a thermosetting epoxy resin (manufactured by Mitsui Toatsu Co., Ltd., trade name: Structbond) was screen printed as a sealing material. Hereinafter, a liquid crystal display element was produced in the same manner as in Example 1. The liquid crystal cells of Examples 1 to 5 and Comparative Example 1 were observed and evaluated for the following characteristics. The results are shown in Table 1. Characteristic 1) Alignment state when no voltage is applied (visual observation) Characteristic 2) Alignment state when no voltage is applied (microscopic observation) Characteristic 3) VT characteristic (relationship between voltage of liquid crystal cell and amount of transmitted light) Characteristic 4) Contrast Ratio (amount of transmitted light when voltage is applied: amount of transmitted light when no voltage is applied) Characteristic 5) High temperature (85 ° C) movie display after 500 hours of life test

[0056]

[Table 1]

Microscopic observation of the liquid crystal cell of Comparative Example 1 confirmed that the periphery of the spacer was white and blurred in the dark field showing good alignment, and that alignment failure occurred. At this time, the spherical spacer portion appeared bright due to light leakage. In Comparative Example 1, it is considered that the contrast ratio is lowered due to these factors. On the other hand, in each of Examples 1 to 5, the alignment state was good and a high contrast ratio was obtained.

In the above embodiments, an active matrix type liquid crystal cell using TN type liquid crystal as a liquid crystal display element was manufactured, but the present invention can also be applied to a simple matrix type liquid crystal display element.

An example of a simple matrix type liquid crystal display element will be described with reference to FIG. As shown in FIG. 7, the glass substrate 1 having the scanning electrodes 31 formed on the surface thereof is coated with a thermosetting polyimide solution, heated and dried,
A rubbing process is performed to form the alignment film 3. Example 1
Similarly to the above, a spacer forming material is applied on the alignment film 3, prebaked, exposed and developed, and further heat-treated to form a spacer 4 having a twist alignment ability. next,
A solution of a thermosetting polyimide is applied on the other glass substrate (counter substrate) 5 having the display electrodes 32 formed on the surface, heated and dried, and then subjected to a rubbing treatment to form an alignment film 8. A thermosetting epoxy resin is screen-printed on the peripheral portion of the counter substrate 5 as a sealing material, the glass substrate 1 and the counter substrate 5 are combined so as to face each other, and heated to produce a liquid crystal cell. The liquid crystal composition 9 is sealed inside the cell, and the injection port is sealed. Again,
It is possible to obtain the same effect as that of the above-described embodiment.

In the examples shown below, a method of forming a spacer and an alignment film at the same time by using a photosensitive resin as a material for the spacer, pre-baking the photosensitive resin, exposing it to light again, heat treating it again, and then developing it Will be described. Example 6

TF formed with display electrodes and TET elements
A photosensitive polyimide (manufactured by Ciba-Geigy, trade name: Probimide 412) was spin-coated on a T-array substrate at 1500 rpm. The TFT array substrate was placed on a hot plate, and the polyimide film was prebaked under the usual condition of 110 ° C. for 15 minutes.

A photomask having a spacer pattern formed thereon.
The polyimide film was exposed through a screen. This board
Place it on the plate and again from the substrate side at 170 ° C for 10 minutes.
Heated. This heating causes the photosensitive resin on the substrate side to polymerize.
However, the parts exposed to light and the parts polymerized by heat treatment
The dissolution rate of the minute part in the developing solution becomes slow. This photosensitive tree
The fat was developed as in Example 1. The development conditions are as follows
Is the street. Nitrogen pressurization 1.3-2.5kg / cm²  Developer injection amount 8-10 ml / min Developer processing time 240 seconds Overlap time 10 seconds Rinse time 10 seconds Nitrogen spin dry time 20 seconds

This TFT array substrate was placed in an exhaust type oven and the polyimide film was cured at 250 ° C. for 1 hour. As a result, a cylindrical spacer having a height of 5 μm and a diameter of 15 μm and an alignment film having a thickness of 120 nm were formed. This alignment film was rubbed.

On the other hand, a thermosetting polyimide was applied to a counter substrate on which a color filter, a black matrix and a transparent electrode were formed, and a rubbing treatment was performed to form an alignment film. A sealing material was screen-printed on the peripheral portion of the counter substrate. TF
The T-array substrate and the counter substrate were combined and heated under pressure to cure the sealing material, thus producing a cell. At this time,
The spacer was arranged on the black matrix. Liquid crystal was injected into this cell and the injection port was sealed to manufacture a liquid crystal display element.

The accuracy of the inter-substrate gap was ± 0.1 μm on the entire surface of the obtained 4-inch diagonal liquid crystal display element.
It was also confirmed that the alignment state was good. Furthermore, since the spacers are arranged on the black matrix, there is no light leakage or reduction in aperture ratio due to the spacers.
It was also possible to prevent damage to the FT. Example 7

In the same manner as in Example 6, application, prebaking, exposure and heat treatment of the photosensitive polyimide (Probimide 412) onto the TFT array substrate were performed. At this time, the heat treatment condition after the exposure was different from that of Example 6 and was 200 ° C. for 10 minutes. This photosensitive polyimide was developed and cured under the same conditions as in Example 6. As a result, the height is 5 μm and the diameter is 1
A spacer having a thickness of 5 μm and an alignment film having a thickness of 150 nm was formed. This alignment film was rubbed. Hereinafter, a liquid crystal display element was produced in the same manner as in Example 6. The accuracy of the inter-substrate gap was ± 0.1 μm on the entire surface of the obtained 4-inch diagonal liquid crystal display element. It was also confirmed that the alignment state was good. Example 8

TF formed with display electrodes and TET elements
A photosensitive polyimide (manufactured by Ciba-Geigy, trade name: Probimide 408) was spin-coated on a T-array substrate at 1200 rpm. This TFT array substrate was placed on a hot plate, and the polyimide film was prebaked under the normal condition of 110 ° C. for 10 minutes. This polyimide film was exposed in the same manner as in Example 6, heat-treated under the same conditions as in Example 6, and further developed and cured under the same conditions as in Example 6 except that the development processing time was 100 seconds. As a result,
A cylindrical spacer having a height of 2 μm and a diameter of 10 μm and an alignment film having a thickness of 100 nm were formed. This alignment film was rubbed. Hereinafter, a liquid crystal display element was produced in the same manner as in Example 6. The accuracy of the inter-substrate gap was ± 0.2 μm on the entire surface of the obtained 4-inch diagonal liquid crystal display element. It was also confirmed that the alignment state was good. Example 9

In the same manner as in Example 6, the photosensitive polyimide (Providimide 412) was applied onto the TFT array substrate, prebaked, exposed and heat-treated. At this time, the heat treatment conditions after the exposure were different from those in Example 6, and an exhaust type oven was used.
The temperature was 20 ° C. for 1 hour. This photosensitive polyimide was developed and cured under the same conditions as in Example 6. As a result,
Spacer with a height of 5 μm and a diameter of 15 μm and a thickness of 150
An alignment film having a thickness of nm was formed. This alignment film was rubbed. Hereinafter, a liquid crystal display element was produced in the same manner as in Example 6. On the entire surface of the obtained 4-inch diagonal liquid crystal display element,
The accuracy of the gap between the substrates was ± 0.2 μm.

An alignment defect region of the liquid crystal was observed near the spacer, particularly behind the spacer with respect to the rubbing direction. However, when the rubbing process was made parallel to the black stripes, this defective alignment region was located under the black stripes, so that the display portion was not affected and good display results were obtained. Comparative example 2

In the same manner as in Example 6, coating, pre-baking and exposure of photosensitive polyimide (Probimide 412) on the TFT array substrate were carried out. However, heat treatment was not performed after the exposure. This photosensitive polyimide was developed and cured under the same conditions as in Example 6. As a result, a spacer having a height of 5 μm was formed, but the portions other than the spacer which were not irradiated with ultraviolet rays were all peeled off by the development and the alignment film was not formed.

[0071]

As described in detail above, according to the present invention, the uniformity of the substrate spacing, the high aperture ratio, the
This is a significant effect in providing a liquid crystal display device that realizes all of high display quality. In particular, it is effective in providing excellent VT characteristics, contrast, and performance of a moving image display state in a liquid crystal display device using a twisted nematic (TN) type display system or a super twisted nematic (STN) type display system. Is.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an active matrix liquid crystal display element according to a first embodiment of the present invention.

FIG. 2 is a plan view showing the formation positions of spacers on the TFT array substrate in the liquid crystal display element according to the first embodiment of the present invention.

FIG. 3 is a plan view of a photomask used for forming spacers in the liquid crystal display element according to the first embodiment of the present invention.

FIG. 4 is a plan view showing the formation positions of spacers on the TFT array substrate in the liquid crystal display element according to the second embodiment of the present invention.

FIG. 5 is a plan view of a photomask used for forming spacers in the liquid crystal display element according to the third embodiment of the present invention.

FIG. 6 is a plan view showing a formation position of a spacer on a counter substrate in a liquid crystal display element according to Example 4 of the present invention.

FIG. 7 is a sectional view of a simple matrix type liquid crystal display device according to another embodiment of the present invention.

FIG. 8 is an exploded perspective view showing an active matrix liquid crystal display element.

FIG. 9 is an exploded perspective view showing a simple matrix type liquid crystal display element.

[Explanation of symbols]

1 ... Glass substrate (TFT array substrate), 2 ... Pixel electrode,
3 ... Alignment film, 4 ... Spacer, 5 ... Glass substrate (counter substrate), 6 ... Color filter, 7 ... Counter electrode, 8 ... Alignment film, 9 ... Liquid crystal substance, 11 ... TFT element, 12 ... Gate electrode, 13 ... Gate insulating film, 14 ... Semiconductor layer, 15 ... Source electrode, 16 ... Drain electrode, 21 ... Data wiring, 22
... address wiring, 31 ... scanning electrode, 32 ... display electrode, 5
1 ... Polarizing plate, 52 ... Diffusing plate, 53 ... Backlight, 54
... polarizing plate, 101, 102 ... photomask, 110 ... translucent part, 120 ... light-shielding part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuko Gizu 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Stock company Toshiba Research Institute

Claims (1)

[Claims] 1. A pair of substrates each having an electrode and an alignment film formed on the surfaces facing each other are held at predetermined intervals via a seal provided on the peripheral portion of the substrates and a spacer provided on the display section. Then, in the liquid crystal display element in which liquid crystal is sealed between the substrates, a side surface of the spacer has a liquid crystal aligning ability.