JPH0668669B2 - Liquid crystal display manufacturing method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal display device, particularly to a method for pressing two substrates and a method for curing a seal.

2. Description of the Related Art In a method of manufacturing a liquid crystal display device in which a liquid crystal is sealed between two substrates with electrodes, a method of pressurizing the two substrates and a general method of curing the seal are a heat-curing adhesive. A method is known in which a substrate on which a material is applied in a seal pattern and another substrate are superposed on each other via a spacer and the seal adhesive state is heat-cured while the two substrates are pressed by a weight.

In the method using a weight as a method of pressing the substrate, since the contact state with the weight substrate is biased, it is difficult to apply pressure uniformly over the entire surface of the substrate, resulting in variations in cell thickness or unevenness in the cell thickness. There was a drawback that was difficult to obtain. This is a major drawback particularly in the case of a large-area liquid crystal display device or an active matrix liquid crystal display device in which the substrate is largely warped due to internal stress due to a multi-layer thin film process.

On the other hand, a method has been proposed in which an ultraviolet curable adhesive is used as the seal adhesive instead of the heat curable adhesive, and the seal is cured by irradiating ultraviolet rays.

The sealing method using the UV-curable adhesive has the advantages that the curing can be completed in a short time and that thermal strain due to heating does not occur, but the method of pressing the substrate with a weight as described above was adopted. In this case, there is a problem that the structure of the ultraviolet irradiation process becomes difficult, and the above-mentioned drawbacks remain even if this is devised.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In contrast to the prior art, the present invention provides a novel method for pressing two substrates with electrodes and a method for curing a seal, which is highly accurate with little variation in cell thickness and non-uniformity. Cells can be manufactured,
Further, the present invention provides a method for manufacturing a liquid crystal display device, which has a simple manufacturing method and is excellent in sealing reliability.

The drawbacks of the method of applying weight as the method of pressing the two substrates and the method of irradiating the ultraviolet rays as the method of curing the seal are as described above. However, the present invention is particularly suitable for displaying a large area and high definition image. It is particularly effective in a method of manufacturing a simple matrix or active matrix liquid crystal display device, solves the above problems, and necessitates drawing out a large number of extraction electrodes around the display device, which complicates the structure of the seal portion. The present invention also provides a method of manufacturing a liquid crystal display device having excellent sealing reliability even in the display device of the above field.

Means for Solving the Problems The present invention has the following configurations to solve the above problems. That is, in a method for manufacturing a liquid crystal display device in which liquid crystal is sealed between two substrates with electrodes, at least one substrate with electrodes has a structure in which a plurality of extraction electrodes are pulled out from a seal portion around the substrates, and an ultraviolet curing adhesive is used. A heat-curable adhesive containing a material, and a step of applying to one of the substrates in a seal pattern part of which is opened as an injection port,
The step of stacking the two electrode-attached substrates via a spacer means, and vacuum-packing the overlapped cells in a bag that is transparent to ultraviolet rays and is flexible, so that the two electrode-attached substrates are kept under atmospheric pressure. The step of pressing, the step of increasing the viscosity of the adhesive by irradiating the sealed portion of the vacuum-packaged cell with ultraviolet rays from the outside of the bag, and then heating the vacuum-packaged cell It is characterized by including a step of thermally curing the adhesive material.

As described above, as a method of pressing two substrates with electrodes, by vacuum packaging them, ideally uniform atmospheric pressure is applied over the entire surface of the substrates with electrodes, and at the same time, the substrates are vacuum packaged. A bag transparent to ultraviolet rays is used as a bag, and by irradiating ultraviolet rays from the outside of the bag in a vacuum-packed state, the ultraviolet curable adhesive component of a seal made of a thermosetting adhesive containing an ultraviolet curable adhesive is cured. , Thicken the seal. Thereafter, the seal is fully cured by heating the vacuum-packaged cell. At this time, since the seal is thickened in advance, it is possible to prevent the disadvantage that the seal flows and the seal is broken at the time of heat curing. Conventionally, a structure in which a weight is used as a pressurizing method and ultraviolet rays are irradiated to the seal portion has been complicated, but by adopting the above structure, ideally uniform pressing can be realized and ultraviolet rays can be easily irradiated. Became possible.

EXAMPLE Next, the present invention will be described in detail according to an example of the present invention. FIG. 1 is a perspective view showing a pressed state of a substrate by vacuum packaging showing an example of the present invention, and FIG. 2 is related to the present invention. 2 shows two electrode-attached substrates (a and b) and a liquid crystal cell c in which they are combined to show a part of a method for manufacturing a liquid crystal display device. As shown in FIG. 2A, a screen 2 is formed on the surface of one of the substrates 1 by a vapor deposition and photofabrication technique, on which image display elements for image display and thin film transistor elements serving as switching elements are built. Scanning and signal extraction electrodes 3 are formed around the screen 3 on three sides, and an alignment film 4 is applied to cover the screen. As shown in FIG. 2b, the other electrode-attached substrate 5 is coated with an alignment film 6 covering the same transparent electrode, and a heat-curable adhesive 7 containing an ultraviolet-curable adhesive is provided around the alignment film 6. A part of the filler is applied as the injection port 8 in a seal pattern. Glass fiber was mixed with the adhesive as a spacer of the seal portion.

The above-mentioned two substrates 1 and 5 with electrodes are stacked with the alignment film inside to form a liquid crystal cell 9 shown in FIG. 2c via a spacer such as glass fiber. FIG. 1 shows a liquid crystal cell 9 assembled in this way, which is transparent and flexible to ultraviolet rays.
10 shows the state of vacuum packaging. The bag 10 has a vacuum inside the liquid crystal cell 9 placed in the bag by sealing one open end 11 in vacuum, so that atmospheric pressure is applied to the two substrates 1 and 5 through the bag. Therefore, an ideally uniform pressure state can be obtained.

By irradiating the liquid crystal cell vacuum-packed as shown in FIG. 1 with ultraviolet rays from the outside of the bag, the ultraviolet-curable adhesive component in the seal adhesive 7 is cured and the seal adhesive 7 is thickened. . Thereafter, by heating the vacuum-packaged cells, the seal adhesive 7 is fully cured. Especially for the purpose of ensuring the reliability of the seal in a high temperature or high temperature and high humidity atmosphere, it is better to use UV curing as the pre-curing of the seal, and main curing by heating in addition to this in two steps for pre-curing the UV curing. Good results were obtained because the adhesive thickens by curing and prevents a step due to the extraction electrode or seal breakage due to wetting or repellency between the extraction electrode and the insulating substrate.

After the cell 9 which has been hardened is opened, the bag is opened and then the injection port 8
The liquid crystal is injected in a more vacuum and sealed, and then polarizing plates are attached to the front and back surfaces to complete the liquid crystal cell.

3 and 4 compare the details of the seal portion between the conventional example and the manufacturing method according to the present invention, and therefore, the other substrate 5 overlaps in close proximity to the extraction electrode 3 arranged around the substrate 1. The conductor of the extraction electrode 10 to the extraction electrode has a structure in which the conductor is drawn on the edge green body 11 with a step, and the seal 12 is present at this portion. FIG. 3 shows a conventional heat-curing seal, which includes a conductor 10
Due to the difference in the wettability of the edge body 11 and the difference in the level difference between them, the seal adhesive has a low viscosity during heating, and thus the seal 12
It shows that a part 13 is cut off. FIG. 4 shows a state of sealing by ultraviolet curing according to the present invention. As shown in the figure, the seal 14 is in an uncured state due to heating, and the adhesive material is reduced in level. Since there is no movement due to wetting or repellency, there is no risk of seal breakage.

Further, even in the case of a heat-curable adhesive containing an ultraviolet-curable adhesive, the ultraviolet-curable adhesive is cured by irradiation of ultraviolet rays, so that the adhesive itself acts as a pre-curing to increase its viscosity. There is similar curing, and when it is completely cured by heating after that, thickening and curing by pre-curing works effectively, and even if it is heated, the viscosity does not decrease.

EFFECTS OF THE INVENTION As described above, according to the manufacturing method of the present invention, it is possible to obtain a highly accurate cell with extremely few variations in cell thickness and non-uniformity, and the manufacturing method is simple, and the reliability of the seal is excellent. A liquid crystal display device is obtained, which is of great industrial value.

[Brief description of drawings]

FIG. 1 is a perspective view showing a pressed state of a substrate by vacuum packaging showing an embodiment of the present invention, and FIGS. 2a to 2c are two electrodes for showing a manufacturing method of a liquid crystal display device according to the present invention. A perspective view of a substrate and a liquid crystal cell in which these are combined, FIG. 3 and FIG.
The figures are explanatory views of the sealed state according to the conventional and the present invention, respectively. 1 ... Substrate with electrodes, 5 ... Substrate with electrodes, 7 ... Seal,
8 ... injection port, 9 ... liquid crystal cell, 10 ... bag, 12,14 ...
sticker.

Claims (1)

[Claims] 1. A method of manufacturing a liquid crystal display device, comprising a liquid crystal sealed between two substrates with electrodes, wherein at least one substrate with electrodes draws out a plurality of extraction electrodes from a sealing portion around the substrates with electrodes. A step of applying a heat-curable adhesive material containing an ultraviolet-curable adhesive material to one of the substrates in the form of a seal pattern with a part of the substrate opened as an injection port; A step of stacking the stacked cells via a means, and a step of vacuum-packing the stacked cells in a flexible bag transparent to ultraviolet rays to press the two electrode-attached substrates at atmospheric pressure; A step of increasing the viscosity of the adhesive by irradiating the sealed portion of the vacuum-packaged cell with ultraviolet rays from the outside of the bag, and then heating the vacuum-packaged cell to thermoset the adhesive. Method of manufacturing a liquid crystal display device characterized by comprising the step of.