JPH10186377A - Production of liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate ununiformity and dispersion of spaces between substrates and thereby to obtain display of high grade by accurately weighing spacers and uniformly dispersing the spacers on the substrate in the manufacture of liquid crystal display element. SOLUTION: The spacers 9 are charged to excess in a weighing vessel 14 having an opened upper part at a weighing section, the spacers 9 are weighed in a state flush with the upper edge end of the weighing vessel 14 by a means such as vibration of the whole weighing vessel 14 in the horizontal direction and then the spacers together with the weighing vessel 14 are transported and the spacers are supplied to a spacer holding section 18. Here the spacers are blended with compressed air, etc., and are blown from a spreading nozzle 21 onto electrode substrates 4, 8 in a spreading tank 22. After a sealant is applied around the substrate on which the spacers 9 are spread, two sheets of substrates are arranged to face each other so that respective electrodes are orthogonally crossed, surrounding of the substrates are sealed and a liquid crystal composition is poured in a space between the substrates to form a liquid crystal display element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a liquid crystal display device, and more particularly to a method of manufacturing a liquid crystal display device in which spacers are accurately weighed and dispersed at a constant density on a substrate.

[0002]

2. Description of the Related Art In recent years, liquid crystal display elements have been used in various fields as displays for television or OA, taking advantage of their features of light weight and low power consumption. As the liquid crystal display element, there are a simple matrix type in which a liquid crystal composition is sandwiched between orthogonal electrode groups, an active matrix type in which a switching element is provided for each display pixel, and the like.

In such a liquid crystal display device,
In each case, granular spacers are uniformly arranged between the electrode substrates by a wet arrangement method or a dry arrangement method in order to keep the substrate interval constant.

The wet arrangement method is a method in which a glass-based or resin-based spacer material is uniformly dispersed in a low-boiling organic solvent such as ether or chlorofluorocarbon, and is sprayed onto an electrode substrate together with compressed air by a spray gun (nozzle). , Most commonly used. The type and concentration of the organic solvent in the spacer dispersion liquid are adjusted so that the organic solvent as a dispersion solvent is completely evaporated and dried before reaching the substrate.

However, in such a wet arrangement method of the spacer, use of an organic solvent such as chlorofluorocarbon has recently been regulated as one of the substances causing environmental pollution. As disclosed in the official gazette and Japanese Patent Application Laid-Open No. 1-225919, a dry arrangement method of spraying spacers without using a dispersion solvent has been developed.

[0006]

When monochrome display or gradation display is performed by a liquid crystal display element, uneven placement of spacer particles, which has not been a problem in the past, has become a serious problem.

That is, in such a liquid crystal display device,
Even a slight change in the distance between a pair of opposing electrode substrates may cause a change in the threshold voltage or a change in the lighting state, or may cause an interference phenomenon to significantly change the color and impair the stability of display quality. Therefore, a high precision is required for the substrate interval, with an error (variation from a specified value) within ± 0.05 μm. In order to meet such demands, it is necessary to control the density of distribution (distribution) of the spacers on the substrate with extremely high accuracy such that an error (a variation from a specified value) is within ± 5 / mm ² .

However, in the conventional method of weighing and dispersing spacers, it has been difficult to accurately adjust the dispersal density of the spacers and to stably obtain a liquid crystal display element having a uniform substrate gap (cell gap).

In other words, conventionally, a spacer is put into a weighing cup having a predetermined capacity with an open top, and weighing is performed. Since the spacer is piled up on the weighing cup,
Not only is it weighed beyond the capacity of the cup, but the weighing results also vary. For this reason, it has been difficult to control the amount and density of the spacers with high accuracy.

The present invention has been made in order to solve such a problem. By precisely weighing spacers and uniformly dispersing them on a substrate, there is no unevenness or variation in the distance between the substrates and high quality. It is an object of the present invention to provide a method for manufacturing a liquid crystal display element capable of obtaining display.

[0011]

According to the present invention, there is provided a method of manufacturing a liquid crystal display device, comprising: a first substrate provided with a first electrode;
After the spacers are scattered on the electrode forming surface of at least one of the second substrates on which the electrodes are provided, these substrates are arranged so that the first electrode and the second electrode face each other. In the method of manufacturing a liquid crystal display element in which the periphery is sealed, and then the liquid crystal composition is sealed in the gap between the substrates formed by the spacers, the spacers are dispersed in a weighing container having an opening at the top in dispersing the spacers. After the excess is charged, the inserted spacer is ground and weighed with reference to the upper edge of the opening of the weighing container, and then the weighed spacer is mixed with air and jetted.

In the present invention, weighing with a weighing container is performed a plurality of times until a spacer amount necessary for spraying is obtained. In particular, when a container having a storage volume equal to the necessary spacer amount is used as a weighing container. , The required amount can be supplied by a single weighing.

In the manufacturing method according to the present invention, when dispersing the spacers on the substrate, an excessive amount of the spacers is put into a weighing container having an open upper portion, and the spacers are cut off with reference to the opened upper edge of the weighing container. Because it is configured to weigh, the spacer is always stable and accurately weighed based on the volume of the weighing container. Then, the spacer accurately weighed by the volume in this way is mixed with compressed air or the like and sprayed onto the substrate surface, so that the amount and density of spraying are accurately controlled, and the spacers are uniformly arranged on the substrate. Therefore, by using such a substrate, it is possible to manufacture a liquid crystal display element which can obtain a high-quality display image without unevenness or variation in the distance between the substrates and without unevenness in color and display.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

First, prior to describing an embodiment of the present invention, a liquid crystal display device manufactured in the embodiment will be briefly described.

That is, as shown in FIG. 1, this liquid crystal display element includes a first electrode substrate 4 in which a first electrode 2 and an alignment film 3 in a stripe shape are sequentially laminated on an insulating substrate 1, and another A second electrode 6 having a stripe shape and an alignment film 7 on an insulating substrate 5
And the second electrode substrate 8 on which the electrodes 2,
6 are arranged so as to be orthogonal to each other, and a gap of 6.0 to 7.0 μm is held between the first electrode substrate 4 and the second electrode substrate 8 by the granular spacer 9. Then, a liquid crystal composition 10 is sealed between the electrode substrates 4 and 8, and a polarizing plate 1 is formed on the outer surfaces of these substrates.
1 and 12 are arranged. Note that reference numeral 13 in the drawing denotes a seal portion made of a sealing material.

In order to manufacture a liquid crystal display device having such a structure, first, a first electrode 2 and a second electrode 6 (ITO transparent electrode) are formed on insulating substrates 1 and 5 by a usual method. On the electrode forming surfaces of the first electrode substrate 4 and the second electrode substrate 8,
After applying an alignment agent and performing a rubbing treatment, a granular spacer 9 is sprayed on the surface of at least one of the electrode substrates as described below.

That is, as shown in FIG. 2, first, in the spacer weighing section, an excessive amount of the spacer 9 is charged from the spacer storage section 15 into the cup-shaped weighing container 14 having a predetermined capacity and having an open top. By vibrating in a horizontal direction the entire weighing container 14 on which the weighing containers 9 are piled up, the spacers 9 are cut off with reference to the open upper edge of the weighing container 14 to remove the excess piled up. The surplus cutting of the spacer 9 may be performed by moving a cutting plate 16 as shown in the figure along the upper edge of the weighing container 14.

Next, the spacer 9 thus ground and weighed into the weighing container 14 is transferred as it is to the supply port 1.
7 to the spacer holding unit 18, where the air is mixed with the compressed air supplied from the compressed air generation unit 19 or the normal pressure air supplied from the normal pressure air generation unit 20,
Is sprayed into the spraying tank (chamber) 22 from the inside. The inside of the spray tank 22 is kept in a clean atmosphere, and the first or second electrode substrate 4, 8 is arranged on a stage (not shown) below the spray nozzle 21. The spacer 9 sprayed from the spray nozzle 21 is sprayed.

Next, after a sealing material is applied to the periphery of the substrate on which the spacers 9 are scattered, the two substrates are opposed to each other so that the electrodes 2 and 6 are orthogonal to each other, and the periphery is sealed. Seal with material. Then, the liquid crystal composition 10 is injected into the gap between these substrates formed by the spacers 9 and the injection port is sealed to obtain a liquid crystal display element.

With respect to the liquid crystal display device manufactured according to the above embodiment, the change rate (error) of the actual spray density with respect to the standard of the spray density of the spacer was examined in accordance with the number of flowing products. The result is shown by a graph in FIG.

As is apparent from this figure, when the spacers are sprayed on the electrode substrate by the method of the embodiment, the change rate of the actual spray density with respect to the spacer spray density standard is 10%.
It becomes very small as follows. As a result of uniform distribution density of the spacers as described above, stable and high-quality display with very little display unevenness was realized.

On the other hand, as a comparative example, in the case where the spacer was weighed and sprayed as in the past, the change rate of the actual spray density with respect to the spacer spray density standard was similarly examined for each number of flow products, and is shown in FIG. Thus, the actual change rate of the spacer application density reached an average of 15% and a maximum of 30% within the same lot, and it was found that the application density was significantly varied. Then, as a result of such dispersion of the distribution density, when an image was displayed on the obtained liquid crystal display element, display unevenness became remarkably noticeable.

As described above, according to the embodiment, by stably and accurately weighing the spacers, it is possible to easily eliminate the dispersion of the scatter density, and to achieve the gradation required to make the gap uniform with high precision. It is very effective for manufacturing liquid crystal display elements for display and monochrome display.

Next, another embodiment of the present invention will be described.

In this embodiment, as shown in FIGS. 5 (a) and 5 (b), the spray tank 22 to which the spacer 9 is sprayed has a rectangular parallelepiped shape, and is placed on a stage (not shown). Electrode substrates 4 and 8 are arranged.
An electrostatic gun 23 for applying (charging) a voltage to the spacer 9 and spraying the spacer 9 is provided above the electrode substrates 4 and 8 in the spray tank 22. Here, the electrode substrate 4,
8 between the upper surface (electrode formation surface) of the nozzle 8 and the electrostatic gun 23
Is 1000 mm. The spray tank 22 has a square shape with a side length l of 1000 mm.
A predetermined distance is also ensured between each of the spray tanks 3 and the inner wall surface of the spray tank 22.

Then, the weighed spacer 9 is sprayed into the spray tank 22 as described below.
That is, similarly to the above-described embodiment, after the spacer 9 weighed by the weighing container 14 in the spacer weighing unit is supplied to the spacer holding unit 18, the spacer 9 is conveyed by compressed air and a voltage is applied by the electrostatic gun 23. Then, it is ejected from the tip of the electrostatic gun 23, and the electrode substrate 4,
8 is sprayed.

According to the manufacturing method of the present embodiment configured as described above, the spacer 9 is formed on the predetermined surface of the electrode substrates 4 and 8 in consideration of saving of the installation space of the spray tank 22, maintenance, and mass productivity. It is possible to efficiently and uniformly disperse and disperse, and in the liquid crystal display device having the spacers thus dispersed, an excellent display image without color unevenness or display unevenness can be obtained.

That is, generally, when spraying the spacer 9, a voltage is applied to the spacer 9 by the electrostatic gun 23,
By charging each spacer 9 to the same polarity, aggregation of the spacer particles can be prevented, and good dispersibility can be obtained. However, since the electrode patterns are formed on the surfaces of the electrode substrates 4 and 8, if this surface is affected by the electric field of the electrostatic gun 23, the state of the spacers 9 dispersed between the electrode portions and the non-electrode portions (scattering) Density), making it impossible to evenly distribute the spacers 9 on the substrate.

However, in this embodiment, a sufficient distance (1000 mm) is provided between the upper surfaces of the electrode substrates 4 and 8 and the electrostatic gun 23.
Are secured, the electrode substrates 4 and 8 face the electrostatic gun 2
The spacers 9 are uniformly dispersed and dispersed without being substantially affected by the electric field of the third embodiment. In addition, if the distance between the electrostatic gun 23 and the inner wall surface of the spray tank 22 is too short, the inner wall surface of the spray tank 22 is affected by the electric field of the electrostatic gun 23, and as a result, Electrodeposition of the spacer 9 on the wall surface occurs, but in the embodiment, since a sufficient distance is secured between them, the electrodeposition of the spacer 9 on the inner wall surface of the spray tank 22 does not occur, and the electrode substrate 4, Spacers 9 are sprayed on the surface 8 at a sufficient density.

Furthermore, from the viewpoint of the uniformity of the spacer spray density and the spray amount, it is necessary to provide a sufficient distance between the electrostatic gun 23 and the surfaces of the electrode substrates 4, 8 and the inner wall surface of the spray tank 22, respectively. Although it may be more than the above value,
In consideration of the space saving of the installation of the spraying tank 22 and the maintainability, etc., it is desirable to set the above values respectively.

[0032]

As is apparent from the above description, according to the present invention, the spacers weighed accurately without any variation based on the volume of the weighing container are evenly dispersed on the electrode substrate. The distance between the display element substrates can be controlled uniformly,
As a result, defects in gradation display and black-and-white display can be eliminated, and a high production yield can be secured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the structure of a liquid crystal display device manufactured according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing a method of distributing spacers in the embodiment of the present invention.

FIG. 3 is a graph showing a change rate of an actual spray density with respect to a standard of a spacer spray density for a liquid crystal display device manufactured according to an example.

FIG. 4 is a graph showing a change rate of an actual spray density with respect to a standard of a spacer spray density for a conventional liquid crystal display element.

FIGS. 5A and 5B schematically show a spray tank used in another embodiment of the present invention, wherein FIG. 5A is a front view and FIG.

[Explanation of symbols]

 4 First electrode substrate 8 Second electrode substrate 9 Spacer 10 Liquid crystal composition 14 Weighing container 16 Ground plate 18 Spacer holder 21 Spray nozzle 22 Spray tank 23 ... Electrostatic gun

Claims (1)

[Claims] A first substrate on which the first electrode is provided and a second substrate on which the second electrode is provided; Manufacture of a liquid crystal display device in which these substrates are arranged so that the first electrode and the second electrode face each other to seal the periphery, and then a liquid crystal composition is sealed in a substrate gap formed by the spacer. In the method, in sprinkling the spacer, after excessively adding the spacer to a weighing container having an opening at the top, the inserted spacer is weighed by rubbing with reference to the upper edge of the opening of the weighing container, A method for manufacturing a liquid crystal display device, comprising mixing the spacer weighed in this manner with air and jetting the mixture.