JP2001356354A - Manufacturing method of liquid crystal display element - Google Patents

Abstract

(57) [Problem] To provide a method of manufacturing a liquid crystal display element capable of suppressing display unevenness and improving display uniformity. A sealing material is applied to a peripheral portion of at least one of a pair of substrates having an alignment-treated electrode layer to form a sealing portion, and a predetermined amount of liquid crystal is dropped inside the sealing portion of the substrate. In a method of manufacturing a liquid crystal display element in which a spacer material is fixed on the other substrate, the substrates are bonded to each other, and the sealing material is cured to form a panel, at least one of a pair of substrates is bonded to each other. Before that, the substrate is housed in a vacuum container, and the vacuum container is depressurized to remove unnecessary deposits attached to the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal display device which exhibits good characteristics in display uniformity and device reliability.

[0002]

2. Description of the Related Art A liquid crystal display device is a display device in which the initial alignment direction of a liquid crystal is changed to another alignment state by an action utilizing the anisotropy of the liquid crystal, and the resulting change in optical characteristics is used. Compared to conventional display elements, it can be driven at a lower voltage, is suitable for LSI drive, is of a low power consumption type, and can be made thinner and lighter. Developed to be mounted on AV equipment. Currently, the STN display of the simple matrix type and the active matrix type TFT display using the change of the alignment state by the application of the electric field of the liquid crystal, that is, the electro-optical characteristics, have the respective characteristics. It is also installed on each product.

A liquid crystal display element has a sandwich structure in which a liquid crystal is sandwiched between two glass substrates on which a transparent electrode film is formed, and has an alignment film for aligning the liquid crystal on the transparent electrode. For example, in the STN mode, the cell thickness between the substrates is 5 to 7 μm, and the alignment of the liquid crystal is controlled by the alignment film so as to obtain a pretilt angle of 3 to 8 degrees. ST
In the N mode, the orientation direction of the liquid crystal between two substrates is 180 to
Twisting 270 degrees makes it possible to obtain a steep voltage-transmittance characteristic. Therefore, accurate control of the cell thickness is required, and a cell thickness accuracy of 0.05 to 0.1 μm is required to suppress display unevenness due to variations in threshold voltage.

A conventional method of manufacturing a liquid crystal display element using a dropping method will be described below, taking the case of the STN method as an example. First, a glass substrate having a transparent electrode film such as ITO on one main surface is washed. Next, for example, a coating liquid containing a thermosetting polyimide is applied to the electrode film by printing, and after removing the solvent, polymerization and curing are performed to form an alignment film. Next, a rubbing treatment of the alignment film is performed.

[0005] Then, a UV-curable sealing material is applied by printing on the peripheral portion of one of the substrates. A granular spacer material is sprayed on the other substrate, and heat treatment is performed to fix the spacer material to the substrate. Here, in order to control the cell thickness uniformly,
A spacer material having good particle diameter uniformity is used. Next, after a necessary amount of liquid crystal is dropped using a liquid ejection device on the inside of the seal material of the substrate on which the seal material is printed, the substrate and the substrate to which the granular spacer material is fixed are attached using an alignment device. .

Then, in order to prevent the liquid crystal from being deteriorated by ultraviolet rays, the display portion is hidden by a mask, and only the sealing portion is irradiated with ultraviolet rays to cure the sealing material. Next, heat treatment is performed to stabilize the orientation of the liquid crystal. Thereafter, a polarizing plate is attached to both outer surfaces of the substrate, whereby a liquid crystal display device is manufactured.

In the dropping method, the required amount of liquid crystal is directly supplied onto the substrate by the liquid discharge device, so that the injection time can be greatly reduced and the injection time can be kept constant regardless of the panel size. There is a feature that it is easy to respond to the change.

[0008]

However, in the conventional manufacturing method, the uniformity of the cell thickness is not always sufficiently controlled, and a manufacturing method capable of controlling the cell thickness more uniformly is required. ing.

Accordingly, an object of the present invention is to provide a method of manufacturing a liquid crystal display element capable of suppressing display unevenness and improving display uniformity.

[0010]

In order to solve the above-mentioned problems, a method of manufacturing a liquid crystal display device according to the present invention comprises providing a sealing material on a peripheral portion of at least one of a pair of substrates having an alignment-treated electrode layer. Applying to form a seal part, a predetermined amount of liquid crystal is dropped inside the seal part of the substrate, a spacer material is fixed on the other substrate, the substrates are bonded together, the seal material is cured, and the panel is formed. In the method for manufacturing a liquid crystal display element to be formed, at least one of the pair of substrates,
Before the substrates are bonded to each other, the substrates are housed in a vacuum container, and the vacuum container is depressurized to remove unnecessary deposits attached to the substrate.

According to the present invention, at least one of the pair of substrates is housed in a vacuum container before the substrates are bonded to each other, and the vacuum container is depressurized to reduce the amount of waste material adhering to the substrate and adhering to the substrate. Kimono can be removed. Thereby, the substrates can be bonded to each other in a state where the unnecessary deposits are removed. Therefore, the cell thickness can be made more uniform and the variation in the pretilt angle can be suppressed.
It is possible to prevent display unevenness and improve display uniformity. Here, the unnecessary deposits include dust and moisture mixed during the manufacturing process, impurities contained in the alignment film and the like, and a spacer material having a weak adhesion to the substrate.

It is preferable that the substrate on which the sealing material is applied is housed in a vacuum container and reduced in pressure before the liquid crystal is dropped. After the liquid crystal is dropped on the substrate, dust, moisture, and impurities adhering to the substrate are covered with the liquid crystal, and thus are not easily removed. However, by keeping the substrate coated with the sealant under reduced pressure before the liquid crystal is dropped on the substrate, dust, moisture, and impurities can be easily removed.

It is preferable that the substrate to which the spacer material is fixed is housed in a vacuum container and reduced in pressure. The spacer fixed to the substrate has a different fixing force to the substrate depending on the particle shape and particle diameter. The spacer having a weak fixing force easily moves when the dropped liquid crystal spreads in the cell, and causes a non-uniform cell thickness. Therefore, by holding the substrate to which the spacer material is fixed under reduced pressure,
Before laminating the substrates, the spacer having a weak fixing force is removed in advance. Thereby, the cell thickness can be made more uniform.

It is preferable that the pressure in the vacuum vessel is reduced to 133.3 Pa or less. By holding the substrate under a pressure of 133.3 Pa or less, unnecessary deposits can be removed in a shorter time.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. FIG. 1 is a flowchart showing a manufacturing process in a method for manufacturing a liquid crystal display element according to the present embodiment. First, in a substrate cleaning step, a glass substrate having a transparent electrode film such as ITO on one main surface is cleaned. Next, in the alignment film printing step, for example, a coating liquid containing a thermosetting polyimide is applied to the electrode film by printing, and the solvent is temporarily cured and removed in the temporary curing step, and polymerized in the main curing step to form an alignment film. . Next, a rubbing process of the alignment film is performed in a rubbing process, and thereafter, the substrate subjected to the rubbing process is cleaned in a substrate cleaning process.

Next, in a seal printing step, a seal portion is formed by printing and applying an ultraviolet-curable seal material on the peripheral portion of one of the substrates. Then, in the depressurizing step, the substrate on which the seal portion is formed is placed in a vacuum container such as a glove box and the pressure is reduced, and the pressure is maintained at a predetermined pressure for a predetermined time. Next, after returning to the atmospheric pressure, in a liquid crystal dropping step, a required amount of liquid crystal is dropped inside the seal portion on the substrate by using a liquid discharge device.

On the other hand, in the spacer dispersing step, a granular spacer material is dispersed on the other substrate, and then, in the spacer fixing step, heat treatment is performed to fix the spacer material to the substrate. Then, in the decompression step, the substrate to which the spacer material is fixed is placed in a vacuum container such as a glove box and the pressure is reduced, and the pressure is maintained at a predetermined pressure for a predetermined time. Next, after returning to atmospheric pressure, in a substrate bonding step, the substrate and the substrate on which the liquid crystal is dropped are bonded using an alignment device.

Next, in the seal hardening step, in order to prevent the liquid crystal from deteriorating by ultraviolet rays, the display portion is hidden by a mask, and only the seal portion is irradiated with ultraviolet rays to harden the seal portion. Then, a liquid crystal display element is manufactured through a heat treatment step and a polarizing plate attaching step.

FIG. 2 is a schematic sectional view showing the structure of a liquid crystal display device manufactured by using the above method. The liquid crystal display element A includes a segment glass substrate 1 and a common glass substrate 2
And a liquid crystal 10 held in a predetermined gap defined by the thickness of the spacer material 9 in the panel surface and the thickness of the sealing material 8 containing the spacer material.
And polarizing plates 11 and 12 attached to both outer surfaces of the substrate. Further, RG is provided on the inner surface of the common glass substrate 2.
A color filter 7 composed of fine strip-shaped dots of B;
A common electrode 6 and a polyimide alignment film 4 are sequentially formed. Also, on the inner surface of the segment glass substrate 1,
A segment electrode 5 and a polyimide alignment film 3 are sequentially formed.

According to the present embodiment, before the liquid crystal is dropped, the substrate coated with the sealing material is accommodated in a vacuum container, and the vacuum container is depressurized and held under a predetermined pressure for a predetermined time, whereby the substrate is Adhered dust, moisture and impurities can be easily removed. Since there is no dust, moisture or impurities on the substrate, the uniformity of the cell thickness can be improved. It also has the effect of suppressing variations in pretilt angle. Further, by holding the substrate on which the spacer material has been sprayed under a reduced pressure for a predetermined time, the spacer having a weak adhesive force to the substrate can be scattered and removed.
The movement of the spacer accompanying the flow of the liquid crystal sealed between the substrates can be suppressed, and the uniformity of the cell thickness can be improved.

Here, the pressure at the time of pressure reduction is 133.3 Pa
The pressure is preferably 133.3 Pa or less, and more preferably 66.6 Pa or more. If the pressure is 133.3 Pa or more, it takes a long time to remove unnecessary deposits. Further, unnecessary deposits adhering to the substrate can be sufficiently removed at 66.6 Pa or more.

It is preferable that the time from the holding of the substrate under reduced pressure to the dropping of the liquid crystal is short. When maintained at a pressure of 133.3 Pa or less, the pressure is preferably within 5 minutes, more preferably within 2 minutes. This is because the amount of dust and moisture adhering to the substrate over time can be suppressed by shortening the time until the liquid crystal is dropped.

In this embodiment, the example in which the substrate on which the sealing material is applied and the substrate on which the spacers are scattered is held under reduced pressure is shown. However, it is preferable that the substrate is kept under reduced pressure even after the alignment treatment. This is because dust taken in the alignment film may appear on the inner surface of the substrate and come into contact with the liquid crystal even in a portion not in contact with the liquid crystal.

[0024]

Hereinafter, the present invention will be described in more detail with reference to examples. Example 1 Using a glass substrate (300 mm × 400 mm) having an ITO electrode film subjected to orientation treatment, a glass substrate coated with a sealing material to form a seal portion was housed in a glove box, and the glove box was depressurized. After holding the glass substrate under a pressure in the range of 533.2 to 66.6 Pa for 30 seconds or 90 seconds, the pressure was returned to the atmospheric pressure, and 2 minutes later, liquid crystal was dropped inside the seal portion. Further, the glass substrate to which the spacer material was fixed was held for 30 seconds or 90 seconds under the same pressure as the glass substrate to which the sealing material was applied. Then, the glass substrate on which the spacer material has been sprayed is returned to the atmospheric pressure, and two minutes later,
The liquid crystal display devices (Nos. 1 to 6) having the structure shown in FIG.

With respect to the manufactured display element, the panel transmittance difference when 1/300 duty drive and 100 Hz multiplex drive were performed was measured. In particular,
The panel transmittance difference was measured when the transmittance of the portion not in contact with the liquid crystal at the time of bonding was fixed at a driving voltage that reached 50% of the maximum transmittance in static driving.
FIG. 3 shows the relationship between the panel transmittance difference and the holding pressure of a liquid crystal display element manufactured by holding the predetermined pressure for 30 seconds or 90 seconds.

From this, it was found that the transmittance difference can be reduced by keeping the substrate under reduced pressure. In particular, it was found that by maintaining the pressure at 133.3 Pa or less for about 90 seconds, the difference in transmittance could be substantially eliminated, and display unevenness could be suppressed.

The change in the number of spacer materials at the same point when the glass substrate to which the spacer material was fixed was held under reduced pressure was examined by microscopic observation. FIG. 4 shows the relationship between the holding pressure and the residual ratio of the spacer material.

Thus, it was found that by holding the substrate to which the spacer material was fixed under reduced pressure, it was possible to remove the spacer material having a low fixing force to the substrate.

[0029]

As described above, according to the method of manufacturing a liquid crystal display element of the present invention, at least one of a pair of substrates having an alignment-treated electrode film is subjected to reduced pressure before bonding the substrates together. , It is possible to remove unnecessary deposits adhered to the substrate and to improve the uniformity of the cell thickness. Therefore, it is possible to provide a method for manufacturing a liquid crystal display element in which display unevenness is prevented and display uniformity is improved.

Further, in the manufacturing method of the present invention, the substrate coated with the sealing material is kept under reduced pressure before the liquid crystal is dropped, so that dust, moisture and impurities adhering to the substrate can be easily removed. As a result, the uniformity of the cell thickness can be further improved.

Further, in the manufacturing method of the present invention, since the substrate to which the spacer material is fixed is held under reduced pressure, the spacer having a low fixing force can be removed before bonding the substrates together. The uniformity of the cell thickness can be further improved.

Further, the production method of the present invention relates to the method of 133.3P
Since the substrate is held under a reduced pressure equal to or lower than a, unnecessary deposits can be removed in a shorter time, and the manufacturing time of the liquid crystal display element can be further reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart showing steps of a manufacturing method according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a structure of a liquid crystal display element obtained by a manufacturing method according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a holding pressure and a panel transmittance difference in an example of the present invention.

FIG. 4 is a diagram showing a relationship between a holding pressure and a spacer remaining rate in the example of the present invention.

[Explanation of symbols]

1 segment glass substrate, 2 common glass substrates,
3,4 polyimide alignment film, 5 segment electrode, 6
Common electrode, 7 color filter, 8 sealant with spacer, 9 spacer material in panel surface, 10
Liquid crystal, 11,12 polarizing plate, A liquid crystal display element.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H089 NA09 NA22 NA27 NA44 NA45 NA53 QA12 QA14 5G435 AA01 AA11 AA17 BB12 EE09 KK05 KK10

Claims (4)

[Claims] 1. A sealing material is applied to the periphery of at least one of a pair of substrates having an alignment-treated electrode layer to form a sealing portion, and a predetermined amount of liquid crystal is dropped inside the sealing portion of the substrate. Then, a spacer material is fixed on the other substrate, the substrates are bonded to each other, and the sealing material is cured to form a panel. In the method for manufacturing a liquid crystal display element, at least one of the pair of substrates may be bonded to each other. A method for manufacturing a liquid crystal display device, comprising: housing the substrate in a vacuum container before bonding; and depressurizing the vacuum container to remove unnecessary deposits on the substrate. 2. The manufacturing method according to claim 1, wherein the substrate coated with the sealing material is housed in a vacuum vessel and reduced in pressure before the liquid crystal is dropped. 3. The manufacturing method according to claim 1, wherein the substrate to which the spacer material is fixed is housed in a vacuum vessel to reduce the pressure. 4. The production method according to claim 1, wherein the pressure in the vacuum vessel is reduced to 133.3 Pa or less.