JPH11264985A - Manufacture of liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a liquid crystal display element which actualizes a bright display element capable of making high precision of a narrow cell gap and display of high quality by increasing uniformity in a cell gap surface so as to cope also with a large-sized liquid crystal display element and also having a large numerical aperture by improving alignment precision. SOLUTION: One of a couple of substrates 2a and 2b between which liquid crystal is sandwiched is coated with a seal material for sealing the liquid crystal and spacers for prescribing a cell gap are scattered over the other substrate or projections are provided, the substrate 2b is sucked to one surface plate 9 having suction holes or grooves between a couple of surface plates 9 and 10 which are provided in a variable pressure tank 8 so that one of them is freely displaced, the other substrate 2a is installed on the other surface plate 10 through a buffer material 12 and further, in the state that the pressure in the variable pressure tank 8 is made to a prescribed pressure, a pair of the substrates 2a and 2b are positioned, pressed and stuck together.

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 element used as an image display device such as a personal computer and a TV receiver.

[0002]

2. Description of the Related Art Conventionally, in a manufacturing process of a liquid crystal display element, an injection method and a dropping method have been considered as a method of enclosing liquid crystal in a liquid crystal cell. The former injection method is generally used as a method for mass production. It is treated and filled with liquid crystal from the opening of an empty cell by capillary action and pressure difference in a vacuum. On the other hand, the dropping method is a method in which liquid crystal is dropped on one substrate in advance and the other substrate is bonded in a vacuum. Each method goes through the process of bonding a pair of substrates,
The liquid crystal panel has been completed.

Hereinafter, a conventional method for manufacturing a liquid crystal display device will be described with reference to the drawings. FIG. 7 is a cross-sectional view of a main part showing a configuration of a liquid crystal display element manufactured by a conventional liquid crystal display element manufacturing method, and FIG. 8 is a flowchart of a manufacturing process in a conventional liquid crystal display element manufacturing method. It is based on the method. In FIG. 7, a liquid crystal display element 1 has a spacer 4 dispersed so as to form a predetermined cell gap between a pair of substrates 2a and 2b having internal display electrodes 5a and 5b, and a liquid crystal 3 so as to fill the cell gap. Is filled. On both sides of the pair of substrates 2a and 2b, a polarizing plate and other optical films (not shown) are provided at optimal locations. One polarizing plate, 2 depending on the principle mode
May be used or not used. In addition, 6 is a sealing material and 7 is an alignment film.

The liquid crystal display element 1 having such a structure is illuminated with light from a three-wavelength cold cathode tube or the like from the opposite side of the display surface in the case of the transmission type, and is displayed on the opposite side of the display surface in the reflection type. A reflector can be installed to make it brighter by using external light. In this manner, the liquid crystal display element 1 can be driven as a voltage and used as a display.
Hereinafter, a method for manufacturing the conventional liquid crystal display element shown in FIG. 7 will be described with reference to FIG. In the injection method, first, the substrates 2a and 2b on which the display electrodes 5a and 5b are provided are washed, and a liquid alignment material is applied by offset printing or the like, and then the alignment film 7 is formed through preliminary firing and main firing, and rubbing or the like is performed. Is performed. Generally, after rubbing, water cleaning is performed to remove foreign substances and dirt on the surface.

Next, one of the substrates, for example, the substrate 2
A sealing material 6 for sealing the liquid crystal 3 is applied to a by a drawing device or screen printing to form a seal pattern. Further, UV resin for temporary fixing is spot-printed outside the area of the liquid crystal display element 1 by a dispenser or the like. Then, a spacer 4 of a predetermined size is sprayed on the other substrate 2b to form a cell gap, and both substrates 2b are exposed to air.
a and 2b are stuck together. At the time of bonding, the alignment marks provided on the electrodes in advance on both substrates 2a and 2b are made to be optically recognizable. When the alignment marks match, the UV resin for temporary fixing is irradiated with ultraviolet rays. And cure.

Here, in order to control the gap of the liquid crystal display element 1, the whole of the pair of substrates 2a and 2b is pressurized by an air press or the like, and the seal material 6 is cured when an optimum gap is formed. At this time, when a thermosetting sealing material is used, the sealing material 6 is hardened by applying heat using a heater wire installed in a platen of an air press (not shown). U
In the case of a V-curing type sealing material, a transparent thick plate such as glass or acrylic material is used as a surface plate for air pressing, and ultraviolet light is irradiated from the outside of the surface plate when the optimum gap comes out. 6 is commonly used.

After that, the glass portion outside the substrate display area is cut, and in the injection method, a pool of the empty cells and the liquid crystal 3 thus formed is placed in a variable pressure tank.
At about 0.2 to 0.7 Torr, the injection portion of the empty cell is brought into contact with the liquid crystal, the inside of the variable pressure tank is opened to the atmosphere, and the liquid crystal 3 is introduced into the empty cell.
Fill. Then, the sealing portion is closed with a resin or the like, and the liquid crystal 3 adhered to the liquid crystal display element 1 is washed. After that, the entire liquid crystal display element is annealed, and the liquid crystal 3 is subjected to a reorientation process, thereby completing the operation.

[0008]

However, in such a manufacturing method, a heating press or a UV press for obtaining an optimum gap when an empty cell is formed is used. There is a problem that in-plane uniformity cannot be obtained. That is, in the method of bonding substrates, there are the following problems to optimize a pair of substrates with good alignment accuracy and gap accuracy. First, an appropriate empty cell is not formed because the alignment step and the pressing step for gap generation are separated. In other words, the UV resin temporarily fixed in the alignment process may come off due to the forced force of the pressure press in the next process, deviating from the width of the alignment accuracy of the markers on the pair of substrates, and failing to perform sufficient assembly. Yes, and even if a pair of substrates are pasted and temporarily fixed with high alignment accuracy, since the sealing material in the subsequent seal curing step is a thermosetting resin, it is added to the time of the heat press and the liquid crystal display element. Due to a change in temperature, a difference in linear expansion coefficient between the pair of substrates made of glass and the sealing material sandwiched between the substrates causes a shift in the alignment position, so that sufficient alignment accuracy cannot be obtained. This problem increases in proportion to the size of the substrate.

On the other hand, when a UV resin is used for the sealing material,
Ultraviolet rays are irradiated from the outside of the transparent platen while the cell gap is once formed by the pressure press, but as the number of work increases, the platen is heated by radiant heat due to ultraviolet irradiation, and the platen itself rises in temperature Therefore, the temperature is applied only to the side of the substrate that is in contact with the surface plate, and the other substrate has no temperature change. When the material is cured, the combined substrate is in a warped state, causing gap unevenness in the liquid crystal display element. This problem also becomes larger as the substrate size increases.

As described above, in the conventional manufacturing method, in order to achieve both sufficient alignment accuracy and gap accuracy,
There is a problem that it cannot cope with a substrate size that will become larger in the future.

The present invention solves the above-mentioned conventional problems, and has a high precision of a narrow cell gap so as to be applicable to a large liquid crystal display element of a 20-inch equivalent required for an LCD monitor or the like as a substitute for a CRT. The object of the present invention is to provide a method of manufacturing a liquid crystal display element which enables high-quality display by increasing the uniformity in the cell gap plane and improves the alignment accuracy and realizes a bright display element with a large aperture ratio. And

[0012]

According to the method of manufacturing a liquid crystal display device of the present invention, a seal material is applied to one of a pair of substrates sandwiching a liquid crystal to form a seal pattern for sealing the liquid crystal. Performing a step of spraying a spacer defining a cell gap or providing a projection defining a cell gap on the one substrate or the other substrate; and forming the pair of substrates in an atmosphere adjusted to an appropriate pressure. The surface on which the seal pattern is formed and the surface on which the spacers are scattered or the surface on which the protrusions are provided are opposed to each other and aligned, and the two are pressed and bonded via a buffer means.

According to the manufacturing method of the present invention, the alignment step and the gap control step can be performed in a series of steps in an atmosphere adjusted to an appropriate pressure without being divided as in the related art. The accuracy and the uniformity in the cell gap plane are improved, and the uniformity of the cell gap is further assured in the case where the waste seal pattern is formed.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that, in each embodiment, the same reference numerals are used for the same parts as those of the related art.

(Embodiment 1) FIG. 1 is a sectional view showing a main part of a configuration of a liquid crystal display element manufactured according to Embodiment 1 of a method of manufacturing a liquid crystal display element of the present invention. In this liquid crystal display element 1, spacers 4 are dispersed so as to form a predetermined cell gap between a pair of substrates 2a and 2b having display electrodes 5a and 5b therein, and a liquid crystal 3 is filled to fill the cell gap. doing. On both sides of the pair of substrates 2a and 2b, a polarizing plate and other optical films (not shown) are provided at optimal locations. The substrates 2a and 2b include a color filter substrate, an array substrate on which active elements are arranged, a substrate on which transparent electrodes are formed, and the like. The spacer 4 has a spherical shape made of a resin such as benzoquinamine or SiO ₂ .
There is a rod shape, and a spacer 4 is fixed to the substrates 2a and 2b to improve the cell gap uniformity. Further, instead of dispersing the spacers 4, a protrusion having the same height as the spacers 4 may be provided on one of the substrates. A sealing material 6 is applied and formed around the liquid crystal display element 1.
The sealing material 6 includes a thermosetting type made of an epoxy resin and an ultraviolet curable type such as a radical or cationic type. In addition,
Reference numeral 7 denotes an alignment film described later. This configuration is the same as the conventional one shown in FIG. 7, but is characterized by its manufacturing method. Hereinafter, a method of manufacturing a liquid crystal display element using an injection method will be described. FIG. 2 is a flowchart of a manufacturing process in the first embodiment of the method for manufacturing a liquid crystal display element according to the present invention. As shown in this flowchart, first, after cleaning, the substrates 2a and 2b (hereinafter, reference numerals refer to FIG. 1) 2), a liquid alignment material is offset-printed and dried at a high temperature to form an alignment film 7. Then, the surface of the alignment film on the substrate is rubbed with a buff, and if there is a foreign substance on the surface, a cleaning step is performed. One of the substrates 2a and 2b thus formed, for example, the sealing material 6
Is applied by drawing or printing to form a seal pattern, and the spacers 4 are uniformly spread on the substrate 2a or the other substrate 2b. Then, the conductive resin is applied in a spot manner with a dispenser.

FIG. 3 is a schematic diagram showing an outline of a substrate bonding apparatus which can carry out the method of manufacturing a liquid crystal display element of the present invention.
After applying the conductive resin to the substrate 2a or the substrate 2b,
This is an apparatus for loading and bonding these substrates 2a and 2b. This device has a pair of upper and lower platens 9, 10 at least one of which can be displaced in a variable pressure tank 8, and a recognition camera is provided in the device so that alignment can be performed. First, one of the substrates, for example, the substrate 2a is placed on a lower platen 10 via a buffer material 12 serving as a buffer means, and the other substrate 2b is placed on an upper platen having a suction hole (or groove) 9a. After the pressure inside the variable pressure tank 8 is adjusted to a predetermined pressure, the upper and lower substrates 2a and 2b are aligned with required accuracy while confirming the positional alignment of the markers. The two substrates 2a and 2b are attached to each other, and the inside of the variable pressure tank 8 is returned to the atmospheric pressure. At this time, the thickness variation of the two substrates 2a and 2b and the upper and lower plate
It is possible to form a cell gap with a value smaller than 0 flatness. Then, the liquid crystal display element 1 is formed by curing or temporarily curing the sealing material between the two substrates 2a and 2b.

To make an empty cell, cut around the substrate,
Prepare an empty cell and a liquid crystal reservoir in the variable pressure tank, and after the degree of vacuum in the variable pressure tank has stabilized to some extent, dip the sealing part of the empty cell into the liquid crystal reservoir and return the inside of the variable pressure tank to atmospheric pressure, and empty it. The liquid crystal is injected into the cell gap by the differential pressure inside and outside the cell and the capillary phenomenon. When the amount of liquid crystal reaches a certain amount, close the sealing part with resin,
Excess liquid crystal is washed away, and the entire liquid crystal display element is annealed to perform a liquid crystal reorientation process.

FIG. 4 is a plan view showing an example of a seal pattern applicable to the first embodiment of the method for manufacturing a liquid crystal display element according to the present invention. 11 is provided, and the waste sealing material 11 formed outside the sealing material 6 for sealing the liquid crystal is utilized for achieving uniformity of the gap. In the present embodiment, since the substrates are bonded in the variable pressure tank, the sealing material 11 as shown in FIG. Even if the inside of the variable pressure tank 8 of the assembling apparatus is returned from the vacuum state to the atmosphere, the empty cell portion can maintain the vacuum state, and the in-plane uniformity of the cell gap can be maintained. Improve. Then, the empty cell portion is kept in a vacuum state until the substrate is cut to form an empty cell by fully curing the sealing material.

As described above, according to the present embodiment, by performing the alignment step and the gap control step in the same continuous step without separating the alignment step and the gap control step as in the related art, a secondary This eliminates the drawbacks that have been caused, thereby preventing misalignment or departure due to gaps, and improving the productivity of the liquid crystal display without causing warpage of the liquid crystal display element.

(Embodiment 2) FIG. 5 is a flowchart of a manufacturing process in Embodiment 2 of a method of manufacturing a liquid crystal display element according to the present invention, which is based on the above-described dropping method. As shown in this flowchart, the procedure up to rubbing the substrates 2a and 2b on which the alignment film 7 has been formed is the same as that shown in FIG. 2. If there is a foreign substance on the surface, the cleaning step after rubbing is performed. . The sealing material 6 is applied to one of the substrates 2a thus formed by drawing or printing, and the spacers 4 are uniformly dispersed on the other substrate 2b. For the sealing material 6, a radical or cationic UV resin is used. The spacer 4 is formed by using a fixed type.
A certain degree of adhesion strength to the substrate 2b is required. Then, the conductive resin is applied in a spot manner with a dispenser.

Next, the liquid crystal 3 is dropped, but it is more suitable to drop it on the substrate 2a on which the sealing material 6 is applied. The amount of the liquid crystal 3 to be dropped can be calculated in advance from the display area of the liquid crystal display element 1 and the cell gap thickness. A pattern is prepared so that the liquid crystal 3 spreads uniformly, and the defoamed liquid crystal 3 is dropped. After this dropping, both substrates 2a and 2b are bonded by the substrate bonding device shown in FIG. First,
The substrate 2a on which the liquid crystal 3 is dropped is placed on the lower surface plate 10,
After adsorbing the other substrate 2b to the upper surface plate 9 and setting the inside of the variable pressure tank 8 to a predetermined pressure, while checking the positional alignment of the markers so that the upper and lower substrates 2a and 2b obtain the required alignment accuracy, The upper and lower platens 9 and 10 are pressurized to press the substrates 2a and 2b.
And the inside of the variable pressure tank 8 is returned to the atmospheric pressure. Then, the sealing material is cured by irradiating only the sealing material 6 between the two substrates 2a and 2b with ultraviolet rays. For this purpose, there are masking in the display area and laser light irradiation. Lastly, the liquid crystal 3 is subjected to a re-orientation process in an annealing step, and the substrates 2a and 2b are cut to produce the liquid crystal display element 1.
FIG. 6 shows a second embodiment of a method for manufacturing a liquid crystal display element according to the present invention.
FIG. 7 is a plan view showing an example of a sealing material pattern applicable to the liquid crystal display element 1 according to the above-described dropping method, in which a seamless sealing material 11 surrounding the alignment film 7 is formed as shown in FIG. The uniformity of the cell gap between the in-plane central portion and the peripheral portion of the sealing material 6 can be improved.

As described above, according to the present embodiment, the alignment step and the gap control step are performed in the same continuous step without separating the alignment step and the gap control step as in the related art. This eliminates the drawbacks that were previously encountered, thereby preventing misalignment and departure due to gaps, increasing the productivity of the liquid crystal display without causing warpage, and improving the bonding process in the variable pressure tank. Since a liquid crystal dropping step of a pre-calculated amount is performed, higher gap accuracy can be obtained, and thereby a larger size and a smaller cell gap required in the future can be realized. In addition, the liquid crystal dropping method is suitable for constructing an efficient line in tact and lead time, and the minimum amount of liquid crystal used is also minimized.

[0023]

As described above, according to the present invention, the uniformity in the cell gap plane, the cell gap accuracy,
An advantageous effect that alignment accuracy can be improved can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part showing a configuration of a liquid crystal display element manufactured according to a first embodiment of a method for manufacturing a liquid crystal display element of the present invention.

FIG. 2 is a flowchart of a manufacturing process in Embodiment 1 of the method for manufacturing a liquid crystal display element of the present invention.

FIG. 3 is a schematic view showing an outline of a substrate bonding apparatus that can carry out the method of manufacturing a liquid crystal display element of the present invention.

FIG. 4 is a plan view showing an example of a seal pattern applicable to the first embodiment of the method for manufacturing a liquid crystal display element of the present invention.

FIG. 5 is a flowchart of a manufacturing process in Embodiment 2 of the method for manufacturing a liquid crystal display element of the present invention.

FIG. 6 is a plan view showing an example of a seal pattern applicable to the second embodiment of the method for manufacturing a liquid crystal display element of the present invention.

FIG. 7 is a cross-sectional view of a main part showing a configuration of a liquid crystal display element manufactured by a conventional method of manufacturing a liquid crystal display element.

FIG. 8 is a flowchart of a manufacturing process in a conventional liquid crystal display element manufacturing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal display element 2a, 2b Substrate 3 Liquid crystal 4 Spacer 5a, 5b Display electrode 6 Sealing material 7 Alignment film 8 Pressure variable tank 9,10 Surface plate 11 Discarded sealing material 12 Buffer material

Claims (4)

[Claims] A step of applying a sealant to one of a pair of substrates sandwiching the liquid crystal to form a seal pattern for sealing the liquid crystal; and forming a cell gap between the one substrate and the other substrate. A step of spraying a spacer defining the step or a step of providing a protrusion defining the cell gap, and in an atmosphere adjusted to an appropriate pressure, the surface of the pair of substrates on which the seal pattern is formed and the surface on which the spacer is sprayed or A method for manufacturing a liquid crystal display element, comprising a joining step of aligning the surfaces provided with projections so as to face each other and pressing and bonding the two via a buffer means. 2. The bonding step is performed by adsorbing a substrate to one of a pair of movable platens, at least one of which has a suction hole or a groove for sucking air so that the pressure is lower than the pressure in the atmosphere. The method for manufacturing a liquid crystal display element according to claim 1, wherein 3. The method according to claim 1, further comprising a step of fixing the spacer when the spacers are scattered, and a step of dropping or applying an amount of liquid crystal to fill the cell gap on one or the other substrate. A method for manufacturing a liquid crystal display device according to claim 2. 4. The method according to claim 1, further comprising the step of forming an unbroken seal pattern surrounding the seal pattern for sealing the liquid crystal. Method for manufacturing a liquid crystal display element.