JPH0895068A - Liquid crystal display device and manufacture thereof - Google Patents

Abstract

PURPOSE: To provide an STN system liquid crystal display device of which the distance between orientation films is uniform. CONSTITUTION: Display electrodes and orientation films 3, 9 are respectively provided on the opposite faces of upper and lower substrates 1, 7 having flexibility, spacers 4 are scattered on the orientation film 3 by the dispersion number of 1000-2000 pieces/mm<2> , thermal pressure fitting is executed so as to let flow the binding material layer 6 of the spacers 4 and make the diametral dimension of a core member 5 to be the distance between the orientation films, and the core member 5 is fixedly secured to both orientation films by solidifying the binding material layer 6. Hereby, even if the substrate is curved, the distance between the orientation films can by uniformly held. In addition, the characteristic of liquid crystal display becomes favorable, because the distance between the orientation films is uniformly held.

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 a method for manufacturing the same, and more particularly to a spacer for holding a predetermined distance between transparent substrates of an STN type liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, as a liquid crystal display device having this kind of flexibility, a display electrode and an alignment film are provided on opposite surfaces of a plastic transparent substrate, and particles are provided between the alignment films. There is a type in which the transparent spacers are dispersed and both transparent substrates are bonded to each other via a sealing material, and a liquid crystal is sealed between the transparent substrates inside the sealing material.
Conventionally, in a TN (Twisted Nematic) type liquid crystal display device, a gap between both transparent substrates (between alignment films) is, for example, 9 μm, and a spacer dispersion number is 1
It is set to 00 to 500 pieces / mm ² . The permissible value of the gap variation in this TN method is about ± 0.5 μm, and this permissible value is satisfied by setting the dispersion number in the above range. In addition, STN (Super Twi
In a liquid crystal display device of the “Sted Nematic” type,
The set value of the gap is 7 μm, and the allowable value of the gap variation is about ± 0.1 μm.

[0003]

[Problems to be Solved by the Invention] However, STN
When the spacers are arranged in the liquid crystal display device of the TN system with the same dispersion number as the above TN system, the allowable value of the gap variation is ± 0.5 μm and ± 0.1 μm as in the above.
The allowable value of m could not be satisfied, and a uniform gap was not formed. If a uniform gap cannot be obtained between the transparent substrates, inconvenience such as color unevenness occurs in the liquid crystal display. Particularly, in the STN type liquid crystal display device, since the twist angle of the liquid crystal is as large as 200 to 270 degrees, subtle variations in the gap have a great influence on the display characteristics. Further, since the transparent substrate has flexibility, there is a problem that the gap variation becomes large when the transparent substrate between the adjacent spacers is bent. The problem to be solved by the present invention is what kind of means should be taken to obtain a liquid crystal display device in which the gap between the substrates is always kept uniform and the display quality is good and stable.

[0004]

In order to solve the problems, therefore, the invention according to claim 1 interposes a spacer made of particles having a constant diameter between two transparent substrates provided with alignment films on opposite surfaces. Along with these transparent substrates, liquid crystal is enclosed between S
In the TN type liquid crystal display device, the spacer is 10
The solution is to arrange on the alignment film with a dispersion number of 00 to 2000 / mm ² . Further, the invention according to claim 2 is characterized in that the transparent substrate used in the liquid crystal display device has flexibility. Further, the invention according to claim 3 is characterized in that the spacer has a structure in which an adhesive layer is formed on the surface of a particulate core member.

According to a fourth aspect of the present invention, a spacer made of particles having a certain diameter is dispersed on the alignment film provided on the surface of at least one flexible transparent substrate, and then the other A transparent liquid crystal display device of STN type is manufactured by stacking both transparent substrates so that the alignment film provided on the surface of the flexible transparent substrate comes into contact with the spacer and enclosing the liquid crystal between the transparent substrates. In the above method, the spacers are dispersed so that the number of dispersed spacers is 1000 to 2000 pieces / mm ² . Further, in the invention according to claim 5, the spacer comprises an adhesive layer formed on the surface of a particulate core member, and when the transparent substrates are superposed, a heat treatment is performed to apply the adhesive layer. It is characterized in that it is adhered to the alignment film in contact therewith.

[0006]

In the present invention, the spacer dispersion number is 10
By setting the number to be 2000 to 2000 pieces / mm ² , it is possible to improve the uniformity of the gap between the transparent transparent substrates. Further, when the number of dispersed spacers is within the above range, good display characteristics can be secured without reducing the space where liquid crystal exists. In particular, even when the entire transparent substrate is bent, setting the dispersion number within the above range has the effect of preventing the gap between adjacent spacers from changing. Further, the spacer is configured to have an adhesive layer formed on the surface of a core member having a predetermined diameter dimension, and after dispersing the spacer on the surface of the alignment film of one transparent substrate,
By performing heat treatment when the alignment films of the other transparent substrate are superposed, the adhesive layer is melted by heat, and the distance between the alignment films becomes the diameter of the core member. Then, the core member and the alignment film are bonded by the action of the adhesive layer.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the liquid crystal display device and the manufacturing method thereof according to the present invention will be described below with reference to the embodiments shown in the drawings. 1 to 4 are cross-sectional explanatory views showing a manufacturing process of the liquid crystal display device of the present embodiment. First, in the present embodiment, as shown in FIG. 1, a well-known technique is used on one side surface of a flexible lower substrate 1 made of a resin such as polyethylene terephthalate, polyether sulfone, or polyimide. IT
A display electrode 2 made of O or the like and an alignment film 3 made of polyimide or the like are formed, and the alignment film 3 is subjected to an alignment treatment (rubbing treatment).

Next, as shown in FIG. 2, a large number of spacers 4 are dispersed on the alignment film 3. The spacers 4 are coated with an adhesive layer 6 made of thermosetting resin or thermoplastic resin having a film thickness of 0.05 to 0.1 μm on the surface of a core member 5 made of, for example, SiO _{2 and} having a diameter of 7 μm. It will be done.
In this embodiment, the number of dispersions of the spacers 4 is 1000
It is sprayed at a rate of up to 2000 pieces / mm ² . As a spacer spraying method, a predetermined number of spacers are mixed with an alcohol-based solution such as isopropyl alcohol, and this solution is sprayed onto the surface of the alignment film 3. At this time, the alcohol solution, which is a solvent, evaporates before reaching the alignment film 3, and only the spacers 4 reach the surface of the alignment film 3 and are dispersed. The dispersion number of the spacers 4 can be set within the above range by controlling the mixing amount of the spacers 4 in the solvent, the spraying amount, and the like.

Next, as shown in FIG. 3, ITO is formed on one side surface.
An upper substrate 7 having a display electrode 8 and an alignment film 9 made of, for example, is prepared. The upper substrate 7 is also the lower substrate 1.
It is made of the same material as and has flexibility. Then, the alignment film 9 and alignment grooves (not shown) formed by alignment treatment on the alignment film 3 of the lower substrate 1 and 200 to 270 are arranged to face the alignment film 3 of the lower substrate 1. An alignment groove (not shown) having an angle of degrees is similarly formed by the alignment process. Further, a sealing material 10 made of a thermosetting resin is formed by printing or the like on the periphery of the surface facing the lower substrate 1 of the upper substrate 7 so as to surround the display area. A liquid crystal injection port (not shown) for injecting liquid crystal is formed in the sealing material 10. Then, the upper substrate 7 and the lower substrate 1 having such a configuration are overlapped so that the alignment films 3 and 9 sandwich the spacer 4. At this time, the sealing material 10 is thermoset by thermocompression bonding from both the upper and lower surfaces, and the two substrates 1 and 7 are bonded together via the sealing material 10. In addition, the adhesive layer 6 of the spacer 4 that comes into contact with the alignment films 3 and 9 of both substrates 1 and 7 is
By flowing and escaping, the core member 5 in these portions is exposed and brought into contact with the surfaces of both alignment films 3 and 9,
After that, the contact material layer that has flowed and escaped is cooled and solidified, so that the core member 5 is attached to both substrates 1 and 7 via the adhesive layer 6.
Are fixed to the surfaces of the alignment films 3 and 9.

Next, the liquid crystal 11 is injected from the liquid crystal injection port formed in the sealing material 10, and then the liquid crystal injection port is sealed with a sealing material (not shown). In this way, the liquid crystal display device of this embodiment as shown in FIG. 4 is manufactured. In the present embodiment, for convenience of explanation, the lower substrate 1 is described as the upper substrate 7 alone. However, a long base film is prepared as a transparent substrate, and a plurality of liquid crystal display regions are formed in this. It may be cut to form individual liquid crystal display devices.

In the liquid crystal display device formed in this embodiment, as shown in FIG. 4, between the upper and lower substrates 1 and 7 as two transparent substrates provided with alignment films 3 and 9 on opposite surfaces. And a spacer 4 made of particles having a constant diameter size is interposed between the spacers, and the spacers are arranged on the alignment film at a dispersion number of 1000 to 2000 particles / mm ² . The distance between the two alignment films 3 and 9 is the same as the diameter of the core member 5 forming the spacer 4. Further, both the upper and lower substrates 1 and 7 are made of resin and have flexibility, but since the spacers 4 are arranged in a distributed number within the above range and the individual spacers 4 are fixed to both the alignment films 3 and 9, Even if the substrates are bent, the two substrates can be held at a constant distance. Therefore, in the liquid crystal display device of the present embodiment, it is possible to prevent the display quality from deteriorating due to the curvature of the substrate. In particular, in the case of the STN method, the twist angle of the liquid crystal is 200 to 270 degrees, and the twist of the liquid crystal is deviated only by subtly changing the distance between the alignment films. , The fluctuation can be prevented.

In Table 1 below, spacers are used, in which a spherical core made of SiO ₂ having a diameter of 7 μm is coated with an adhesive layer having a thickness of 0.05 to 0.1 μm on the surface thereof, and the number of dispersions thereof is used. The result of measuring the variation amount of the distance between the alignment films by changing (pieces / mm ² ) is shown. The set interval in this measurement was 7 μm.

[Table 1] As can be seen from Table 1 above, the number of dispersed spacers is 1000.
± 0.1 μm variation in the distance between the alignment films at the number of pieces / mm ²
And the allowable value of gap variation is satisfied. However, if the number of dispersions exceeds 2000 / mm ² , the existing space of the liquid crystal is excessively reduced, so that the amount of light transmission is reduced, thereby deteriorating the characteristics of the liquid crystal display. Therefore, the spacer dispersion number is in the appropriate range of 1000 to 2000 pieces / mm ² . Although the embodiment has been described above, the present invention is not limited to this, and various design changes accompanied by the gist of the configuration are possible. For example, in the above embodiment, the spacers 4 are scattered on the alignment film 3 on the lower substrate 1, but the spacers 4 are scattered on the upper and lower substrates, and the spacers are formed when the two substrates are superposed. The dispersion number of 4 is 1000 to 200
The number may be 0 / mm ² .

[0013]

As is clear from the above description, according to the present invention, the distance between the transparent substrates can be kept uniform, and an STN type liquid crystal display device having good display characteristics can be realized. Further, even if a flexible transparent substrate is used, the distance between the substrates does not change, and therefore, an effect of enabling good liquid crystal display is obtained.

[0014]

[Brief description of drawings]

FIG. 1 is an explanatory sectional view showing a process of an embodiment of the present invention.

FIG. 2 is a sectional explanatory view showing a process of an example of the present invention.

FIG. 3 is a cross-sectional explanatory view showing a process of an example of the present invention.

FIG. 4 is a sectional explanatory view showing a process of an example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Lower substrate 2 ... Display electrode 3 ... Alignment film 4 ... Spacer 5 ... Core member 6 ... Adhesive layer 7 ... Upper substrate 8 ... Display electrode 9 ... Alignment film 10 ... Sealing material 11 ... Liquid crystal

Claims (5)

[Claims] 1. An STN method in which a spacer made of particles having a certain diameter is interposed between two transparent substrates having alignment films provided on opposite surfaces, and liquid crystal is sealed between these transparent substrates. 2. The liquid crystal display device according to item 1, wherein the spacers are arranged on the alignment film at a dispersion number of 1000 to 2000 pieces / mm ² . 2. The liquid crystal display device according to claim 1, wherein the transparent substrate has flexibility. 3. The liquid crystal display device according to claim 1, wherein the spacer has an adhesive layer formed on a surface of a particulate core member. 4. A transparent substrate having flexibility after dispersing spacers made of particles having a certain diameter size on an alignment film provided on the surface of at least one flexible substrate having flexibility. In a method for manufacturing an STN liquid crystal display device, by stacking both transparent substrates so that the alignment film provided on the surface of the substrate abuts on the spacers, and enclosing a liquid crystal between the transparent substrates, the dispersion of the spacers is performed. Number of 1000-2000 / mm ²
A method for manufacturing a liquid crystal display device, which comprises: 5. The spacer has an adhesive layer formed on the surface of a particulate core member, and heat treatment is performed when the transparent substrates are superposed to bond the adhesive layer to an abutting alignment film. The method for manufacturing a liquid crystal display device according to claim 4, wherein the alignment films facing each other are separated by the diameter of the core member.