JPS61112128A - liquid crystal display device - Google Patents

Abstract

PURPOSE:To cure instantaneously a UV-curing adhesive agent and to prevent the generation of camber by adhering two sheets of substrates having extremely different coeffts. of thermal expansion to each other via said adhesive agent. CONSTITUTION:The opposite surfaces of the active substrate 1 formed by integrating thin film transistors on quartz glass and forming picture element electrodes 7 and the counter glass electrode made of 'Pyrex(R)' glass having an electrode 6 over the entire surface are first subjected to an orientation treatment. The UV-curing adhesive agent 5 is then formed on the substrate 1 by, for example, screen printing and the substrate is mated in position with the glass substrate 2. UV rays are irradiated to the substrates while specified load is kept loaded thereto to cure the adhesive agent 5. The curing is completed within about 1min, by which the surface temp. of the substrates can be kept within about <=50 deg.C.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing a liquid crystal display device.

In particular, it relates to the bonding structure between two substrates of the liquid crystal display device.

[Conventional technology]

A method of manufacturing a conventional liquid crystal display device and its structure will be described in detail with reference to FIGS. 3 and 4. FIG. 8 shows a general method for manufacturing a liquid crystal display device. That is, the process (α
), an active substrate 1 made of quartz with a small thermal expansion coefficient (6, OX 10-7 cm/°C) on which thin film transistors are integrated and an inexpensive active substrate 1 with a large thermal expansion coefficient (approximately 33 x 10-' crn/° C.) The mutually facing surfaces of the opposing glass substrates 2 made of Pyrex glass are subjected to alignment treatment in order to control the alignment of liquid crystal molecules. Usually, processing is often carried out by activating the surface of an organic polymer film formed on a substrate. In step (b), the active substrate 1
A thermosetting adhesive 3 is applied to the inner surface of at least one of the substrates, here the active substrate 1, in order to bond the opposite glass substrate 2 and form a space for sealing the liquid crystal. Process (
In c), the required alignment of the upper and lower substrates is performed. In the process, a certain load is applied and heated to harden the thermosetting adhesive 8. Thus far, the active substrate 1 and the opposing glass substrate 2 are bonded with the thermosetting adhesive with a certain gap between them. 3, and the liquid crystal display device is manufactured up to the stage before liquid crystal encapsulation. Figure 4 shows the cross-sectional structure of the completed liquid crystal display device with liquid crystal 4 encapsulated. It is oriented and confined between two substrates glued together according to the display mode.In the liquid crystal display bag fitFi made as described above, on the other hand, since the active substrate 1 is used, the drive duty ratio is The goal was to achieve a clear pixel display that could achieve almost 100% display and display over a large area.

Furthermore, if a color filter is used as the counter glass substrate 2, it is possible to display a full color image.

[Problem that the invention seeks to solve]

However, when a thermosetting adhesive 8 is used as in the conventional example, it must be kept at a high temperature of approximately 100'C or higher for a long time in order to cure.

Now, since a high temperature process is required to integrate thin film transistors, an active substrate 1 with a high softening point and a small coefficient of thermal expansion is used as one substrate, and an inexpensive counter glass with a large coefficient of thermal expansion is used as the other substrate. Board 2t-
When the adhesive is cured at high temperature, assuming that the coefficient of thermal expansion of the facing glass substrate 2 is positive and large, the cross-sectional structure will be like that of a whistle. It will look like Figure 5. When this is taken out to room temperature in the next process, the opposing glass substrate shrinks, and the cross-sectional structure of the manufactured liquid crystal display device becomes as shown in Figure 6. As a result, the liquid crystal display device has a large glue. shape, and furthermore,
As shown in Figure 6, the gap between the two substrates where the liquid crystal is injected is not constant, and the liquid crystal display device obtained by injecting the liquid crystal here is because the thickness of the liquid crystal 4 is not uniform. The display becomes uneven and the display quality deteriorates. Specifically, differences in electro-optical characteristics occur depending on the location due to coloring of the display device and uneven thickness at various parts.

Further, when the liquid crystal display device is assembled as components, warping occurs in high-density packaging, which makes positioning and the supporting structure of the liquid crystal display device complicated.

Furthermore, as heat curing is not completed instantaneously as mentioned above,
If there is an imbalance in the load being applied during curing, the two substrates will shift from the required position and will continue to cure. If this phenomenon is significant, one of the substrates will separate from the adhesive and will not function as a liquid crystal display device. It doesn't work.

[Means for solving problems]

The liquid crystal display device of the present invention is a liquid crystal display device configured by sealing a liquid crystal in a space created by bonding two substrates having different coefficients of thermal expansion at a constant interval. It is characterized by being bonded together using an ultraviolet curing adhesive.

[Effect]

According to the above configuration of the present invention, since the adhesive is instantly cured by light energy, the thermosetting adhesive 8
f: When used, both of the two substrates are heated to the curing temperature, but in other words, only the adhesive can be selectively cured without causing the temperature of the substrate to rise. It becomes possible.

〔Example〕

Embodiment 1 FIG. 1 shows a method for manufacturing a liquid crystal display device in an embodiment of the present invention. In step (α), thin film transistors are integrated on quartz glass, and a pixel electrode 7 is formed on an active substrate. 1 and a facing glass substrate 2 made of Pyrex glass having electrodes 6 on the entire surface are subjected to alignment treatment, and then in step (b), an ultraviolet curable adhesive 5 is activated by, for example, screen printing. It is formed on the substrate 1. In step (C), after performing the necessary positioning, the ultraviolet curable adhesive 5 is cured by irradiating ultraviolet rays with force and a constant load. Proceeds quickly through the action of ultraviolet light,
The curing process was completed within about 1 minute, and the substrate surface temperature during curing was able to be kept below about 30°F.

In order to be more thorough, in the ultraviolet ray irradiation process U), for example, by masking with an ultraviolet cut filter so that only the part of the ultraviolet curable adhesive 5 is irradiated, the temperature rise on the substrate surface can be prevented. It is possible to suppress the temperature to a lower temperature.

A cross-sectional structural diagram of the liquid crystal display device according to the present invention constructed as described above is shown in FIG. 2 (α). While using two substrates 1.2 with significantly different coefficients of thermal expansion, the thermosetting adhesive 8
The amount of warpage is less than that of the conventional example using liquid crystal 4
A liquid crystal display device with a uniform thickness was obtained.

Example 2 Cross-sectional structural diagram fc of a liquid crystal display device according to an example in which colored layers 8 of red (G), lines (G), and blue (B) are formed on the inner surface of a counter glass substrate 2 according to the present invention. Figure 2 (b
)It was shown to. Each colored layer is connected to the active substrate 1.
It is required to align the pixel electrode 7 so that it overlaps with the pixel electrode 7 formed on the pixel electrode 7 . According to this example, a bright full-color liquid crystal display device can be obtained, but in particular, by using the ultraviolet curing anti-adhesive 5, even though the coefficients of thermal expansion of the two substrates 1 and 2 are greatly different, By suppressing misalignment during curing and eliminating discoloration caused by uneven thickness of the liquid crystal 4, a full-color liquid crystal display device with excellent color reproducibility was realized.

Example 8 According to the present invention, even when a plastic film is used as one of the substrates, the effect is significant because the two substrates have different coefficients of thermal expansion.

〔Effect of the invention〕

As described above, according to the present invention, by adopting a structure in which two substrates having significantly different coefficients of thermal expansion are bonded together via the ultraviolet curing adhesive 5, the curing of the adhesive is performed using light energy. Since the process is completed instantly, the liquid crystal display device can be constructed without applying unnecessary temperature to the substrate, thereby preventing warping caused by differences in expansion coefficients. In addition, since the thickness of the liquid crystal layer between the two substrates is made uniform, it is possible to obtain a good display with little change in optical characteristics depending on the location even on a large screen. It is effective and does not cause coloring, which is a problem in color display. Furthermore, because there is less glue, it is now possible to manufacture completed liquid crystal display devices with high and stable external precision. In addition, according to the present invention, since it is possible to prevent the occurrence of glue, there is no displacement of the substrate due to unbalanced load during curing, making it possible to achieve a high degree of alignment.

[Brief explanation of drawings]

FIG. 1 is a diagram (α) to (d) showing an example of a method for manufacturing a liquid crystal display device according to the present invention. FIG. 2(cL) is a cross-sectional structural diagram of a liquid crystal display device showing one embodiment of the present invention. FIG. 2(6) is a cross-sectional structural diagram of a full-color liquid crystal display device showing one embodiment of the present invention. Figures 3 (α) to (forces are diagrams showing an example of a typical manufacturing method of a conventional liquid crystal display device. Figure 4 is a cross-sectional structural diagram of a conventional liquid crystal display device. Figure 5 is a diagram of a conventional liquid crystal display device. A cross-sectional structural diagram during the adhesive curing process. Figure 6 is a cross-sectional structural diagram of a completed conventional liquid crystal display device.・Liquid crystal 5...Ultraviolet curing adhesive 6...Full surface PiIL pole of opposing glass substrate 7--Pixel electrode 8...Fixed colored layer and above

Claims (1)

[Claims] In a liquid crystal display device that is constructed by sealing a liquid crystal in the space created by bonding two substrates with different coefficients of thermal expansion at a certain distance, the two substrates are bonded together with an ultraviolet curing adhesive. A liquid crystal display device characterized by being laminated together.