JPH04242720A - Manufacture of liquid crystal display unit - Google Patents

Abstract

PURPOSE:To bond a pair of substrates having different thermal expansion coefficients to each other without generating warping. CONSTITUTION:UV-setting resin which is not necessary to be heated is applied on a glass substrate 10 by a predetermined seal pattern 12 and a binding pattern 13, and a counter substrate is layered on the glass substrate 10. By hardening part of the seal pattern 12 and the binding pattern 13 comprising the UV-setting resin with both pressing and irradiating with UV-ray for stopping them temporarily, and a UV ray is irradiated to unhardened part of the seal pattern 12 to harden the whole of the seal pattern 12. Both substrates are thus bound to each other.

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, in which a pair of transparent substrates are bonded together with an appropriate distance between them, and liquid crystal is injected between them.

0002

[Prior Art] In a liquid crystal display device, a transparent substrate provided with a drive circuit and a transparent substrate provided with a color filter are pasted together with a sealant with an appropriate gap between them, and a liquid crystal is placed in the gap. Manufactured by injection. As a driving circuit for the liquid crystal layer, an amorphous Si thin film transistor (hereinafter abbreviated as a-SiTFT) or a polycrystalline Si thin film transistor (hereinafter abbreviated as p-SiTFT) is used to drive a simple matrix type or active matrix type liquid crystal layer. Used in display devices. With current mass production technology, drive circuits using such TFTs are
A large number of drive circuit units for each liquid crystal display device are formed on one transparent substrate. Such a TFT substrate is bonded to a counter substrate in which each color filter is formed on a single transparent substrate corresponding to each drive circuit unit, and the drive circuit units on each substrate are aligned and bonded to each other. After liquid crystal is injected between the color filter and the liquid crystal, it is divided into individual liquid crystal cells.

In the manufacturing method of such a liquid crystal display device, for example, when forming a large number of p-SiTFT drive circuit units on one transparent substrate, the process temperature reaches a maximum of about 1000°C. For this reason, a normal glass substrate cannot be used as the transparent substrate on which the drive circuit is provided, and quartz glass or the like with excellent heat resistance is used as the transparent substrate. On the other hand, as a transparent substrate on which a color filter is provided as a counter substrate, a normal glass substrate is used because it is not exposed to high temperatures. The TFT substrate and the counter substrate are bonded to each other with an appropriate interval and the peripheral edges of each drive circuit unit and each color filter are sealed with an annular sealing material. Then, liquid crystal is injected into the area surrounded by the sealant. As the sealing material, whether it is a simple matrix type or an active matrix type, a thermosetting adhesive such as an epoxy adhesive having excellent screen printability is usually used.

When bonding the driving circuit board and the counter substrate, a thermosetting adhesive mixed with glass fiber or plastic beads of about 5 to 10 μm is applied to each color filter of the counter substrate, for example. The periphery of the film is applied by screen printing. and,
An ultraviolet curing adhesive for temporary fixing is applied intermittently and linearly to the peripheral edge of the opposing substrate using a dispenser. Spacers made of glass fiber or plastic beads for forming cell gaps are uniformly scattered on the other drive circuit board. Then, both substrates are superimposed on each other in a highly precisely aligned state, and ultraviolet rays are irradiated to the ultraviolet curing adhesive for temporary fixing located at the peripheral edge between the two substrates. As a result, the ultraviolet curable adhesive is cured, and both substrates are temporarily attached to each other. In this state, both substrates are heated and pressurized to cure a large number of annular thermosetting adhesives between the two substrates, and the two substrates are bonded together. In this bonding process, a pressing force of approximately 1 kgf is applied per 1 cm2 of substrate area, while applying pressure of 2 kgf to harden the thermosetting adhesive.
It is heated to a temperature of 00°C.

[0005]

[Problem to be Solved by the Invention] As mentioned above, TFT
The transparent substrate used for the substrate is a quartz substrate with excellent heat resistance, while the transparent substrate used for the counter substrate is a regular glass substrate because heat resistance is not required. has been done. For this reason, the coefficient of thermal expansion of a quartz substrate is relatively small at 4 to 5 x 10-7/°C, whereas the coefficient of thermal expansion of a glass substrate is 40 to 50 x 1
It is as large as 0-7/℃. Therefore, in the bonding process, after both substrates are heated under pressure to harden the thermosetting adhesive, when both substrates return to room temperature,
There is a problem in that the bonded substrates become warped due to the difference in their thermal expansion coefficients. The warpage of both substrates becomes more pronounced as the size of both substrates increases, and in a square substrate with sides of 150 mm, the overlay error due to warpage of both substrates reaches 135 μm when heated at 200° C. Therefore, there is a possibility that the substrate cannot be held by suction in the subsequent process.

The present invention solves these problems, and its purpose is to provide a liquid crystal display device that can bond substrates with different coefficients of thermal expansion together without warping, and has excellent flatness. An object of the present invention is to provide a method for manufacturing a liquid crystal display device that can be manufactured easily.

[0007]

[Means for Solving the Problems] A method for manufacturing a liquid crystal display device according to the present invention is a method for manufacturing a liquid crystal display device in which a pair of substrates are bonded together with an appropriate interval, and liquid crystal is injected between them. , a step of applying ultraviolet curable resin to one of a pair of substrates having different thermal expansion coefficients in a predetermined pattern, and stacking both substrates under pressure via the ultraviolet curable resin. , a step of temporarily fixing both substrates by irradiating and curing a part of the ultraviolet curable resin, and a step of irradiating ultraviolet rays to cure the uncured ultraviolet curable resin of both temporarily attached substrates. and,
The above object is thereby achieved.

[0008]

[Operation] In the method for manufacturing a liquid crystal display device of the present invention, an ultraviolet curable resin is applied to a portion where the liquid crystal is to be sealed and a predetermined position where the liquid crystal is to be temporarily fixed, and substrates having different coefficients of thermal expansion are bonded together. Then, a portion of the ultraviolet curable resin is irradiated with ultraviolet light to temporarily bond the two together. Therefore,
At this time, the positions of both substrates are adjusted again. and,
In order to cure the uncured ultraviolet curable resin, ultraviolet rays are irradiated and the two substrates are bonded together.

[0009]

[Examples] Examples of the present invention will be described below.

In the method for manufacturing a liquid crystal display device of the present invention, 1
For example, a TFT substrate in which a large number of drive circuit units including p-Si TFTs are formed on a single transparent substrate, and a counter substrate in which a large number of color filters corresponding to each drive circuit unit are provided on a single transparent substrate. It includes a step in which the two are bonded together. Both substrates are pasted with the drive circuit unit and color filter facing each other with an appropriate distance between them using an annular sealant surrounding the drive circuit unit. Liquid crystal is injected into the enclosed area. Then, after the liquid crystal is injected, it is divided into each drive circuit unit and color filter, each forming a liquid crystal display device.

TF in which a large number of drive circuit units are provided
A quartz substrate made of quartz glass is used as the transparent substrate of the T substrate. On the other hand, as a transparent substrate for the counter substrate, for example, low-temperature transparent substrates such as "Neoceram" manufactured by Nippon Electric Glass Co., Ltd., "NA35" manufactured by HOYA Corporation, and "1724" manufactured by Corning Corporation are used. A glass substrate with a coefficient of expansion is used.

[0012] The size of each substrate is that the quartz substrate is a wafer with a diameter of 6 inches, and the glass substrate is a wafer with a diameter of 150 m.
The wafer specifications are m square or 6 inches in diameter.

As shown in FIG. 1, the glass substrate 10 for the counter substrate has, for example, a 6-inch wafer specification, and four color filters 11, . . . are arranged in parallel in a square shape in the center thereof. , two color filters 11 are provided around them so as to form a row. Therefore, a total of 12 color filters 11, . . . are provided on the glass substrate 10. A rectangular annular seal pattern 12 surrounding each color filter 11 is applied to the peripheral edge of each color filter 11 using a sealing material made of ultraviolet curable resin by screen printing. Each seal pattern 12 has an opening so that liquid crystal can be injected after the two substrates are bonded together. Further, on the peripheral edge of the glass substrate 10, an adhesive pattern 13 made of ultraviolet curable resin is similarly applied by screen printing using intermittent straight lines so as to form a square shape surrounding all the seal patterns 12. There is.

Each seal pattern 12 and each adhesive pattern 13 are made of, for example, an ultraviolet curing resin such as "LID-1331" manufactured by Nippon Loctite Co., Ltd., and form a predetermined cell gap between the substrates to be bonded. Glass fiber beads with a diameter of 6.0 μm are mixed in to achieve this. The seal pattern 12 and adhesive pattern 13 made of ultraviolet curable resin are
For example, it is applied onto the glass substrate 10 by a screen printing method using a 300 mesh screen plate. Each seal pattern 12 and adhesive pattern 13 has a width of 0.5 mm and a film thickness of 20 to 30 μm, for example. An overlay marker (not shown) is further formed at a predetermined position on the glass substrate 10 by a photo process.

On the other hand, on the TFT substrate on which the same number of drive circuit units as each color filter 11 are provided, plastic beads having a diameter of 5.0 μm are placed.
Sprayed almost uniformly over the entire surface using dry or wet methods,
For common transfer, a conductive resin such as carbon or metal is coated. and,
Similar to the glass substrate 10, overlay markers are formed at predetermined positions by a photo process.

[0016] Such a TFT substrate and the above-mentioned counter substrate are vacuum-adsorbed to upper and lower surface plates of a bonding device, and the two substrates are bonded together. A plurality of through holes are provided in one of the surface plates for irradiating ultraviolet rays to a part of each seal pattern 12 and adhesive pattern 13.
An optical fiber of about mm is inserted. The respective substrates vacuum-adsorbed to the upper and lower surface plates of the bonding device are adjusted in position and placed in a predetermined overlapping state. This position adjustment involves photographing the overlay markers formed on both substrates using an optical system or CCD camera installed in the bonding device, processing the image using an image processing computer, and then displaying the image on a television monitor. Then, both substrates are shifted in the X-axis, Y-axis, and rotational axis directions so that the bonding accuracy is within a predetermined range of ±2 to 3 μm.

Both substrates whose positions have been adjusted in this way are
They are superimposed by bringing each surface plate close to each other.

[0018] After the two substrates are overlaid, for example,
The upper surface plate of the bonding device is pressurized to press both substrates together. The pressing force at this time is approximately 1 kgf/
cm2, and pressure is applied until the cell gap between both substrates corresponds to the diameter of the glass fiber mixed in the seal pattern 12. In this pressurizing process, due to the viscosity and film thickness of the seal pattern 12, there is a risk that a shift of several micrometers will occur between the two overlapping substrates during pressurization. X axis again, Y
By adjusting the position of both boards in the direction of the axis and rotation axis,
The predetermined overlay accuracy is within ±2 to 3 μm.

Next, while maintaining the pressurized state by the bonding device, a portion of each of the seal patterns 12 and adhesive patterns 13 is irradiated with ultraviolet rays, and each of the seal patterns 1
2 and a part of the adhesive pattern 13 are cured, and both substrates are temporarily attached. This temporary fixing step is performed to maintain a predetermined cell gap between both substrates, and a surface plate formed to irradiate a portion of each seal pattern 12 and adhesive pattern 13 with ultraviolet rays penetrates through the surface plate. From the optical fiber inside the hole, for example, the product name "NUX" manufactured by Matsushita Electric Works Co., Ltd.
-7324", approximately 30~
Ultraviolet light is irradiated for 60 seconds. There are 28 through holes in total, 12 in total, 1 in each seal pattern 12, and 4 in each side of each square adhesive pattern 13 on the periphery of the substrate.
It is said to be a place. Alternatively, two locations may be formed for each seal pattern 12, and two locations may be formed for each side of the adhesive pattern 13.

After this temporary fixing step, both substrates are bonded together. In this bonding step, first, the adsorption of both substrates by the bonding device is released, and both temporarily bonded substrates are removed from the bonding device. Then, metal masks exposing only the portions of the seal patterns 12 are superimposed on both surfaces of the temporarily bonded substrates, and the entire surface of both substrates is irradiated with ultraviolet rays. By this ultraviolet irradiation, the portions of each seal pattern 12 that were not cured in the temporary fixing step are cured,
Both substrates are glued together. Between the two substrates bonded in this bonding process, the cell gap maintained in the temporary fixing process is
For example, the cell gap was maintained over the entire surface with a high accuracy of 5.0 μm±10%. Moreover, in all processes including the temporary fixing process and the bonding process, each seal pattern 12 is cured by ultraviolet irradiation and the two substrates are bonded together without heating both substrates. Thus, substrates with different coefficients of thermal expansion can be bonded together without warping.

Next, a method for manufacturing a liquid crystal display device according to a second embodiment of the present invention will be described. In this second embodiment, the steps up to the temporary fixing step are the same as those in the first embodiment, and only the bonding step is different, so only the bonding step will be described.

[0022] In this bonding step, a bonding device for the bonding step that is different from the bonding device for the temporary fixing step is used. This bonding device for the bonding process has a pair of upper and lower surface plates that can be moved toward and away from each other, and at least one or both of the surface plates are made of ultraviolet rays such as quartz glass with a thickness of about 30 to 40 mm. Made of a material with good transparency. In the bonding step, the temporarily bonded substrates and the metal mask exposing each seal pattern 12 are overlapped and pressed between the upper and lower surface plates of this bonding device. The pressing force at this time is 0.5 to 1 kgf/c
The pressure is relatively low, on the order of m2, and the overlapping positions of the two temporarily fixed substrates as described above will not shift. Next, while holding both substrates in a pressurized state, ultraviolet rays are irradiated through a quartz glass surface plate to harden the uncured portions of each seal pattern 12, thereby bonding both substrates together.

Also in the bonding process of the second embodiment as described above, warping of both substrates is prevented.

[0024]

[Effects of the Invention] In the method for manufacturing a liquid crystal display device of the present invention,
In this way, since the substrates having different coefficients of thermal expansion are bonded together using the ultraviolet curable resin, each substrate is not heated, and there is no possibility of warpage occurring due to the difference in the coefficients of thermal expansion between the two substrates. Therefore, a liquid crystal display device with good flatness is manufactured.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a counter substrate used in the method of manufacturing a liquid crystal display device of the present invention.

[Explanation of symbols]

10 Glass substrate 11 Color filter 12 Seal pattern 13 Adhesive pattern

Claims (1)

[Claims] Claim 1: A method for manufacturing a liquid crystal display device, in which a pair of substrates are bonded together with an appropriate distance between them, and liquid crystal is injected between the two substrates, the method comprising: bonding a pair of substrates together with a suitable interval, and injecting liquid crystal between the substrates, the method comprising: , the process of applying ultraviolet curable resin in a predetermined pattern, overlapping both substrates under pressure via the ultraviolet curable resin, and curing by irradiating part of the ultraviolet curable resin with ultraviolet rays. A method for manufacturing a liquid crystal display device, comprising the steps of: temporarily fixing both substrates by holding the substrates together; and irradiating ultraviolet rays to cure uncured ultraviolet curable resin on the temporarily attached substrates.