JPH06331968A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To make uniform orientation and to lower a threshold voltage by providing only the one substrate of a pair of substrates with an orientation treating means and bringing a pair of substrates into tight contact with each other by a column-shaped resin. CONSTITUTION:This liquid crystal display device consists of two sheets of the substrates 101 and 102 and electrodes 103, 104 are formed to face each other on these substrates. A liquid crystal material 106, etc., are clamped therebetween. An oriented film 105 is formed on the surface formed with the electrodes of at least either of the substrates and is rubbed. Spacers 108 are sprayed and a mixture composed of a liquid crystal material 106 and the uncured high-polymer resin is injected into the space. The orientation state of this liquid crystal cell is not twist orientation often observed in the case of formation of the oriented films 105 on two sheets of the substrates 101, 102 but is the uniform orientation. The high-polymer resin (PCS) 107 adheres the inside of two sheets of the substrates 101, 102 and the PCS 107 is formed to the columnar shape between two sheets of the substrates.

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.

[0002]

2. Description of the Related Art Recently, large-area liquid crystal displays have been receiving attention. However, when an inexpensive gas substrate or resin substrate (plastic substrate) is used, the deflection of the substrate itself occurs due to the large area. On the other hand, consideration of measuring a high-speed response of a liquid crystal display device has also been considered as an important issue. For this purpose, a method of using a material capable of high-speed response such as a ferroelectric liquid crystal as the liquid crystal material is considered.

However, when a ferroelectric liquid crystal is used as a liquid crystal material to measure a high-speed response, there is a problem that the area of the liquid crystal display device cannot be increased. This is because the ferroelectric liquid crystal has a layered structure, so that the substrate is deformed so that the layered structure is destroyed and the display is hindered. This problem is not limited to ferroelectric liquid crystals, but can be basically said even when a large number of liquid crystal materials are used.

Further, conventionally, a spacer of silicon oxide held between the substrates is used to keep the space between the substrates, and an organic resin material also held between the substrates is used to bring the substrates into close contact with each other. Was there. The spacer is, as the name implies, for holding the distance between the substrates, and the diameter of the spacer determines the distance between the substrates. The organic resin used to bring the substrates into close contact with each other has a diameter larger than a required substrate interval, and has a function of bringing the upper and lower substrates into close contact with each other by being crushed between the substrates.

In the conventional structure as described above, the substrate is first subjected to the orientation treatment, then the spacer and the resin are sprinkled on one of the substrates, and then the substrates are adhered to each other, whereby the distance between the substrates is increased. After making the decision, the basic manufacturing method was to bond the substrates to each other and then inject the liquid crystal between the substrates. When injecting this liquid crystal, for example, the temperature is set to 100 degrees and then 5 degrees /
The liquid crystal material can be aligned according to the alignment regulating force of the alignment film by gradually cooling with the hr.

However, as a result of studying the above-mentioned conventional manufacturing process, when the liquid crystal changes its orientation and its state according to the orientation regulating force, the resin material for bringing the substrates into close contact with each other acts as an orientation liquid crystal. It turned out that it regulates.

[0007] The above two problems are as follows: -It is necessary to have a structure for keeping the substrate spacing constant. -When aligning the liquid crystal, the material that brings the substrates into close contact with each other adversely affects the alignment of the liquid crystal. As a method of solving such a problem, there is an invention disclosed by the present inventors in Japanese Patent Application No. 5-55237.

According to the present invention, a pair of translucent substrates having electrodes on the surfaces are provided so as to face each other with the electrodes inside, and a liquid crystal material and at least one of the pair of substrates are provided between the pair of substrates. An alignment means for arranging the liquid crystal material in a certain direction is provided on the inner surface of the substrate, and the column-shaped resin material formed by depositing and curing the uncured resin mixed in the liquid crystal material is the The liquid crystal display device is characterized in that it is adhered to the alignment means or the substrate.

According to the method of manufacturing a liquid crystal electro-optical device, a liquid crystal material and a resin material containing a reaction initiator are mixed and sealed between a pair of opposed transparent substrates which have been subjected to an alignment treatment. After aligning the liquid crystal, the resin component is cured by irradiation with ultraviolet rays, and the resin component is cured and formed into a column shape.

The column-shaped resin deposited from the liquid crystal as described above is a PCS in the sense of a column-shaped resin spacer.
(Polymerrigied Column Spacer).

The outline of the above configuration will be described with reference to FIG.
FIG. 1 shows a simple matrix type liquid crystal display device. In FIG. 1, alignment means 114 and 115 for aligning a liquid crystal material in a certain direction are provided on a substrate on a transparent substrate 110 and 111 having electrodes 112 and 113.
Is provided. A liquid crystal material 116 is sandwiched between the substrates. The liquid crystal material 116 is an alignment means 114, 115.
Uniaxially oriented according to. On the other hand, the resin 117 separated and precipitated from the liquid crystal material has a columnar shape (columnar shape) and is adhered to the alignment means 114 and 115 on the two substrates 110 and 111. When the aligning means is formed only on one of the substrates, the resin 117 is, for example, the aligning means 114.
And the transparent substrate 111 or the substrate and the electrode 113 are bonded.

In order to manufacture this liquid crystal electro-optical device, the electrodes 11 whose substrate distance is determined by the spacer 118 are used.
A mixture of a liquid crystal material and an uncured resin to which a reaction initiator is added is sandwiched between a pair of translucent substrates 110 and 111 each having 2, 113, and the uncured resin from the mixture is sandwiched between the translucent substrates. Are deposited to align the liquid crystal material along the alignment means. Then, by applying a means for curing the precipitated uncured resin, the uncured resin is cured to form a column (indicated by 117) to bond the both substrates.

When the configuration shown in FIG. 1 is adopted, the resin is cured after the liquid crystal material 116 is aligned according to the alignment means 115, so that a good liquid crystal alignment state before curing can be maintained, and the resin after curing is The influence on the orientation is extremely small. This column-shaped cured resin 117 has the effect of maintaining the substrate distance and improving the adhesion.
It has the effect of improving the orientation of the liquid crystal.

It is desirable that the resin material used in the above structure exhibits a mixed state with the liquid crystal material in a high temperature state, and separates and precipitates from the liquid crystal material in a state where the temperature is lowered. Further, in order to cure the resin sandwiched between the two substrates, it is highly desirable that the uncured resin contains no solvent. Furthermore, since the separation of the liquid crystal material and the resin and the formation of the alignment state of the liquid crystal material largely depend on the temperature, it is desirable that the resin be cured by a factor different from the temperature. Considering such matters, it is preferable to use, for example, an ultraviolet curable resin as the uncured resin and an ultraviolet ray as the resin curing means. Further, in the above configuration, the type of liquid crystal and the operation mode of the liquid crystal are not particularly limited.

[0015]

Although the above structure is an excellent structure, a higher contrast is required.
In order to increase the contrast, it is useful to make the liquid crystal alignment uniform. In the case of an active type liquid crystal display device, it is necessary to lower the threshold value of the liquid crystal display device. This is a switching element (T
After the voltage is applied to the liquid crystal material by the switching of FT or MIM type element), it is necessary to maintain the state of the liquid crystal even if the voltage applied to the liquid crystal is reduced due to a leak current between electrodes. This is because. Therefore, it is an object of the present invention to uniformly align the liquid crystal material in order to increase the contrast and lower the threshold voltage of the liquid crystal display device.

[0016]

The present invention is a liquid crystal device having a mixture of a liquid crystal material and a resin material held between a pair of substrates, wherein only one of the pair of substrates is subjected to an alignment treatment. Means are provided, and the pair of substrates are closely adhered by the column-shaped resin material.

[0017]

(Operation) (1) When the alignment film has one surface, the liquid crystal material is likely to be in uniform alignment instead of twist alignment. (2) Since there is only one alignment film, it is easy to exchange charges. (3) Low threshold voltage drive (in the case of TFT drive, drive is possible even if the inter-electrode voltage is not kept high).

【Example】

FIG. 2 shows the structure of the liquid crystal cell. The liquid crystal cell is composed of two substrates 101 and 102, electrodes 103 and 104 for driving a liquid crystal material are opposed to each other on the substrate, and a liquid crystal material or the like is sandwiched between the substrates. Here, the thickness of the two substrates is 1.1 mm, 100 × 80 mm
The blue plate glass of was used. A transparent electrode ITO is formed on the two substrates by a method such as a sputtering method. The film thickness of the ITO is 1000Å. The size of the pixel is 60 mm □. The distance between the substrates is 1.5 μm.

An alignment film 105 was formed on the surface of one of the substrates on which the electrodes were formed. The alignment film material is a polyimide resin such as LQ-5200 (manufactured by Hitachi Chemical Co., Ltd.), LP-64 (manufactured by Toray), RN-305 (manufactured by Nissan Kagaku), and LP-64 is used here. The alignment film is diluted with a solvent such as n-methyl-2-pyrrolidone,
It was applied by spin coating. The coated substrate is 250
The coating was cured by heating at ~ 300 ° C, here 280 ° C for 2.5 hours to dry the solvent. The film thickness of the alignment film after curing was 300Å.

Next, the alignment film is rubbed. For rubbing, use a roller wrapped with a cloth such as rayon or cotton for 450-90.
Rubbing was performed in one direction at a rotation speed of 0 rpm, here 450 rpm.

Next, as a spacer 108 for keeping the cell intervals constant, a spherical ball (made by Catalyst Kasei) having a diameter of 1.5 μm was sprinkled on the substrate on the side where the alignment film was applied.
On the other substrate, in order to fix the two substrates, a two-component epoxy adhesive is applied as a sealant by screen printing around the substrates, and then the two substrates are bonded. Fixed

A mixture of the liquid crystal material 106 and the uncured polymer resin is injected into the substrate. Biphenyl-based ferroelectric liquid crystal was used as the liquid crystal material. This liquid crystal has a phase sequence of Iso-SmA-SmC * -Cry. Structural formula _{C 8 H 17 O-C 6} H 4 -C 6 H 4 -COO-C * HCH 3 C 2 H
_{5 C 10 H 21 O-C} 6 H 4 -C 6 H 4 -COO-C * HCH 3 C 2
It is H ₅ , and the above two materials are mixed at a ratio of 1: 1. A commercially available ultraviolet curable resin was used as the polymer resin. The weight ratio of liquid crystal material and uncured polymer resin is 9
Mix at a ratio of 5: 5 and 85:15. The mixture was stirred at a temperature at which it became an Iso (isotropic) phase so that it was uniformly mixed. In the mixture, the transition point from the Iso phase to the SmA phase was lowered by 5 to 20 ° C. as compared with the case where only the liquid crystal material was used.

The injection of the above mixture was carried out under vacuum at 100 ° C. for the liquid crystal cell and the mixture. 2 liquid crystal cells after injection
It was gradually cooled at a rate of -20 ° C / hr, here 3 ° C / hr.

When the alignment state of this liquid crystal cell was observed under a crossed Nicols with a polarization microscope, the extinction position at a certain rotation angle, that is, the light incident on one polarizing plate did not pass through the other polarizing plate, as if it were light. A state in which the power was cut off was obtained. This indicates that the liquid crystal material has a uniform alignment instead of the twist alignment that is often seen when the alignment films are formed on two substrates.

Further, it was observed that polymer resins were scattered and precipitated in the liquid crystal material. Since the polymer resin did not exhibit birefringence, it did not transmit light under a polarizing microscope and appeared black. In this state, the liquid crystal material and the uncured resin can be separated.

Next, ultraviolet rays were irradiated to cure the polymer resin of the cell. Irradiation intensity is 3 to 30 mW / c
m ² , here 10 mW / cm ² , and the irradiation time is 0.1.
5 to 5 minutes, here 1 minute.

After the irradiation of ultraviolet rays, the alignment state of the liquid crystal cell was observed under a polarizing microscope in the same manner as above, but the alignment state was hardly changed. No effect of UV irradiation on the alignment was observed.

The optical characteristics of the above liquid crystal cell were measured. The measurement method is to drive a liquid crystal cell with a rectangular wave of ± 20 V under a crossed Nicols by a polarization microscope using a halogen lamp as a light source, and detect the transmitted light intensity with a photomultiplier. The results are shown in Table 1 below.

[0029]

[Table 1]

According to the results of Table 1 above, the higher the ratio of the cured polymer resin (hereinafter referred to as PCS: Polymarized Column spacer) 107, the larger the area occupied by PCS in the electrode portion. Although the transmittance in the bright display is low, the contrast ratio is a quotient of them, so that there is no significant difference.

When the electrode portion of the liquid crystal cell is observed with the naked eye, the existence of the resin is completely unknown. From these results, when the mixing ratio of the uncured resin is about 0.1 to 20%, it can be compared with the device using only the liquid crystal material.

Next, in order to confirm the effect of slow cooling of the alignment state of the liquid crystal material, the state of the alignment state when the cooling rate is changed is shown in Table 2 below. According to Table 2, the rate of slow cooling is 100 ° C.
If it is faster than / hr, some parts will not be aligned and
When it was slower than / hr, the orientation was good.

[0033]

[Table 2]

The display state of the fabricated cell did not change even when the cell was made vertical. This is because the PCS scattered in the liquid crystal material internally adheres the two substrates to each other to keep the distance between the substrates constant and prevent the cells from expanding like a gourd.

Next, the cross section of the liquid crystal cell was observed with a scanning electron microscope. The liquid crystal material was extracted with alcohol. According to the observation results, the PCS has a columnar shape between the two substrates.
You can see that.

The shape of PCS is the phase sequence of liquid crystal material, liquid crystal /
Some of them have an indefinite shape that changes depending on the slow cooling rate of the resin mixture, and some of them have a major axis of the resin in the uniaxial orientation treatment direction. The PCS interval is 10 to 100 μm.

When a switching element is formed in the cell of this embodiment and active driving is performed, the alignment film is formed on only one side as compared with the case where the alignment films are formed on both sides. Therefore, an electric field is applied to the liquid crystal material. Since it becomes easier to reduce the threshold value, even if the inter-electrode voltage becomes low due to leakage current between the electrodes after the pulse is applied from the switching element to invert the liquid crystal material, The display state of the liquid crystal material can be maintained.

[0038]

The following effects can be obtained by adopting the configuration of the present invention. (1) Uniform orientation: The contrast ratio was improved. (2) Internal adhesion effect: No bending or swelling occurred regardless of the cell installation location. (3) Low threshold drive ... In the case of TFT drive, the liquid crystal material can be operated even if the inter-electrode voltage is not kept high.

[Brief description of drawings]

FIG. 1 shows a schematic view of a conventional liquid crystal cell.

FIG. 2 shows a schematic view of a liquid crystal cell of an example.

[Explanation of symbols]

 101 ... Substrate 102 ... Substrate 103 ... Electrode 104 ... Electrode 105 ... Alignment Film 106 ... Liquid Crystal Material

Claims (2)

[Claims] 1. A liquid crystal device having a mixture of a liquid crystal material and a resin material held between a pair of substrates, wherein only one of the pair of substrates is provided with an alignment treatment means. A liquid crystal display device, wherein a pair of substrates are adhered to each other by the column-shaped resin material. 2. A liquid crystal display device according to claim 1, wherein an alignment film is provided on one of the substrates as an alignment treatment means.