JP2005148523A - Manufacturing method of liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing liquid crystal display device which more efficiently prevents cavitation without requiring preliminary curing a sealing material by irradiation with UV rays. <P>SOLUTION: The method for manufacturing the liquid crystal display device by sticking a pair of substrates 2 and 3 through the sealing material 4 comprises: a drawing process of drawing the sealing material 4 on both the upper and lower substrates 2 and 3; a liquid crystal arranging process of arranging a liquid crystal 5 in a region surrounded by the sealing material 4 of the upper substrate 2 or the lower substrate 3; a sticking process of sticking the upper and lower substrates 2 and 3 by integrating the sealing material 4 of the upper substrate 2 and the sealing material 4 of the lower substrate 3; and a sealing material curing process of curing the sealing material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a liquid crystal display device.

One method for bonding substrates of a liquid crystal display device is a sealingless (ODF) method. This sealing-less method places a sealant on either one of the upper and lower substrates, and a liquid crystal layer can be formed on the area surrounded by the sealant when the upper and lower substrates are bonded together. In this state, the upper and lower substrates are bonded via a sealing material in a state where a certain amount of liquid crystal is applied. Moreover, after bonding, the sealing material part is hardened by ultraviolet irradiation or the like.
In such a sealing-less method, if the upper and lower substrates are bonded together with as much liquid crystal as possible applied to the cell volume, pressure from the excess liquid crystal is applied to the sealing material from the inside of the cell. Occurs. At present, it is difficult to control the amount of liquid crystal applied without any error. For this reason, as a countermeasure against the above-described phenomenon of voiding, before sealing the upper and lower substrates, a sealing material is applied to some extent by ultraviolet irradiation or the like. Is cured (preliminary curing) (see, for example, Patent Document 1).
JP-A-4-107523

However, as described above, the method of precuring the sealing material with ultraviolet irradiation before the upper and lower substrates are bonded together is difficult to control the amount of ultraviolet irradiation to cure the sealing material to the extent that it is not hardened. If the material is hardened too much, there is a problem that the adhesive strength is reduced.
Therefore, the present invention provides a method for manufacturing a liquid crystal display device that does not require pre-curing of the sealing material by ultraviolet irradiation and more effectively prevents the entry phenomenon.

As a result of intensive studies by the present inventors to solve the above-mentioned problems, it has been found that the initial stage of the voiding phenomenon occurs particularly at the interface between the sealing material and the substrate. It came to. More specifically, it has been found that it is likely to occur at the interface between the substrate and the sealing material on the side where the sealing material is not first drawn, and is unlikely to occur at the sealing material other than the interface.
That is, the manufacturing method of the liquid crystal display device of the present invention is a manufacturing method of a liquid crystal display device in which a pair of substrates is bonded via a sealing material, and a drawing process for drawing the sealing material on both the upper and lower substrates, A liquid crystal disposing step of disposing a liquid crystal in a region surrounded by a sealing material of the lower substrate, a bonding step of bonding the upper and lower substrates by bonding the sealing material of the upper substrate and the sealing material of the lower substrate, and a seal And a sealing material curing step for curing the material. By drawing the sealing material on both the upper and lower substrates in advance, bonding the sealing materials on the upper and lower substrates, and bonding the upper and lower substrates together, the adhesion at the interface between the substrate and the sealing material is increased all around the liquid crystal cell, and the liquid crystal is sealed. Even if the sealing material is pressed from the inner circumferential direction, it is possible to suppress the occurrence of a voiding phenomenon.

  In the drawing step, it is preferable that a sealing material is disposed at a corresponding position on the upper and lower substrates. The manufacturing method of the liquid crystal display device of the present invention is characterized in that the sealing material is drawn on both the upper and lower substrates, and the sealing materials on the upper and lower substrates are integrated in the substrate bonding step described later. That is, if an annular sealing material that is closed around the entire periphery of the liquid crystal cell is arranged to improve the adhesion at the interface between the substrate and the sealing material, the positions of the sealing materials arranged on the upper substrate and the lower substrate correspond exactly. In addition, half of the total amount of the sealing material does not have to be drawn on each substrate. More preferably, if each half of the total amount of the sealing material is drawn evenly at the corresponding positions around the upper and lower substrates, the interface between the substrate and the sealing material is strongest around the entire cell, and a simple method is used to enter the void. The phenomenon can be effectively prevented.

  Moreover, it is preferable to provide the preliminary hardening process of the said sealing material after the said drawing process. By providing the pre-curing step, the strength of the sealing material is increased before the upper and lower substrates are bonded together. Therefore, when the upper and lower substrates are bonded together, the durability against the pressure by the liquid crystal is increased. The sealing material may be an ultraviolet curable resin or a thermosetting resin, and in either case, the preliminary curing step is preferably performed by heating. In pre-curing, it is necessary to cure the sealing material properly without over-hardening, but pre-curing by heating is easier to control by temperature, time, etc. compared to controlling the amount of UV irradiation. It can be used more suitably than curing.

Hereinafter, a method for producing a liquid crystal according to the present invention will be described with reference to the drawings. In each drawing used in the following description, the scale is different for each layer and each member so that each layer and each member can be recognized on the drawing.
First, the liquid crystal display device obtained by the manufacturing method of the liquid crystal display device of this embodiment will be described.
FIG. 1 is a plan view of components of the liquid crystal display device according to the present invention as viewed from the counter substrate side. 1, in the liquid crystal display device 100 of this embodiment, a pair of TFT array substrate 110 and counter substrate 120 are bonded together by a sealing material 52 which is a UV curable & thermosetting sealing material. A liquid crystal layer is enclosed and held in the region partitioned by. The sealing material 52 is formed in a frame shape (annular) closed in a region in the substrate surface, and does not include a liquid crystal injection port.

  A peripheral parting 53 made of a light shielding material is formed in a region inside the region where the sealing material 52 is formed. A data line driving circuit 201 and a mounting terminal 202 are formed along one side of the TFT array substrate 110 in a region outside the sealing material 52, and the scanning line driving circuit 204 is formed along two sides adjacent to the one side. Is formed. On the remaining one side of the TFT array substrate 110, a plurality of wirings 205 are provided for connecting between the scanning line driving circuits 204 provided on both sides of the image display area. Further, at least one corner of the counter substrate 120 is provided with an inter-substrate conductive material 206 for establishing electrical continuity between the TFT array substrate 110 and the counter substrate 120.

  Instead of forming the data line driving circuit 201 and the scanning line driving circuit 204 on the TFT array substrate 110, for example, a TAB (Tape Automated Bonding) substrate on which a driving LSI is mounted and a peripheral portion of the TFT array substrate 110 The terminal group formed in the above may be electrically and mechanically connected via an anisotropic conductive film. Further, depending on the type of liquid crystal to be used, that is, the operation mode such as TN (Twisted Nematic) mode, STN (Super Twisted Nematic) mode, and the normally white mode / normally black mode, a retardation plate and a polarizing plate Are arranged in a predetermined direction, but the illustration is omitted here. In the image display region of the liquid crystal display device 100 having such a structure, a plurality of pixels are configured in a matrix, and each of these pixels has a pixel switching TFT (switching element). Although they are formed, illustration of these is also omitted.

FIG. 2 is a flowchart showing a part of the manufacturing method of the liquid crystal display device of the present embodiment.
As shown in FIG. 2, the manufacturing method of the liquid crystal display device according to this embodiment includes a drawing process of a sealing material for drawing a sealing material for sealing liquid crystal on the TFT array substrate and the counter substrate, A pre-curing step, a liquid crystal arranging step of arranging liquid crystal in a region surrounded by the sealing material on the substrate, and a bonding step of bonding the substrates having undergone these steps so that the sealing material is integrated by bonding. And a sealing material curing step for curing the sealing material by ultraviolet irradiation.
In addition, before the sealing material drawing process, an alignment mark is formed so that the sealing material and liquid crystal can be drawn and applied at a predetermined position, and an alignment process is performed to position the substrate according to the alignment mark. Here, description of the alignment step is omitted.

  3 and 4 are cross-sectional views schematically showing the liquid crystal display device 1 according to the present embodiment. 3 shows a state after the liquid crystal arranging step and before the substrate bonding step, and FIG. 4 shows a state after the substrate bonding step. The capacity of the liquid crystal display device 1, that is, after the substrates 2 and 3 are bonded together as shown in FIG. 4, the space formed by the sealing material 4 and both the substrates 2 and 3 is (seal inner area) × (gap The liquid crystal 5 having a control material diameter) is accommodated.

As shown in FIGS. 3 and 4, in the liquid crystal display device 1, a sealing material 4 is disposed around the TFT substrate 3 and the counter substrate 2, and is surrounded by the sealing material on the TFT substrate 3. A liquid crystal 5 is arranged in the region. In the TFT substrate 3 and the counter substrate 2, TFT elements, peripheral parting, and the like are omitted.
3 and 4, the gap control material is omitted. The gap control material is for controlling the thickness of the liquid crystal cell. For example, a substantially sharp substance having the same diameter as that of the cell gap can be mixed with the sealing material. Further, various materials such as those that are not included in the sealing material and that protrude from the substrate in a columnar shape can be used.

<Drawing process of sealing material>
The TFT substrate 3 and the counter substrate 2 are substrates made of quartz glass. First, the sealing material 4 is drawn on these substrates 2 and 3.
As shown in FIG. 3, the sealing material 4 is arranged at positions corresponding to each other on the substrates 2 and 3, and is drawn so as to be integrated when the substrates are bonded together.
The sealing material 4 uses a viscous epoxy-based or acrylic-based resin, and is a UV curing & thermosetting type or a UV curing process that cures by using a combination of ultraviolet curing (UV curing) and thermal curing. There is a 100% UV curable type for curing, but in this embodiment, a UV curable & heat curable type is used. In order to draw the sealing material 4 on the substrates 2 and 3, when the substrates 2 and 3 are bonded, the sealing material is drawn on the surface in contact with the inside of the cell by various dispensing methods. At this time, a width of 0.1 to 0.4 mm and a thickness of 0.01 to 0.04 mm are drawn at predetermined positions around the substrates 2 and 3.

  By drawing the sealing material on the upper and lower substrates 2 and 3 in this manner, the adhesion between the sealing material and the substrate interfaces 21 and 31 on the entire circumference of the liquid crystal display device 1 increases until the substrates are bonded together. Therefore, even if the liquid crystal 5 presses the sealing material 4 from the center side of the substrate after the substrates are bonded together, the phenomenon of entering voids can be suppressed. In this embodiment, the upper and lower substrates are made of the same material as the sealing material.

<Precuring process of sealing material>
After drawing the sealing material, after 10 seconds to 120 seconds (time), a preliminary curing step of the sealing material is performed.
In the preliminary curing step, various heating means such as a hot plate are used, for example, the sealing material is heated at a temperature of 80 to 120 ° C. for 15 to 60 seconds. Although the sealing material can be cured also by ultraviolet irradiation, in the preliminary curing step, the sealing material needs to be appropriately cured while maintaining elasticity and adhesion. It is preferable to heat in the pre-curing step, because fine adjustment to the degree of curing of the sealing material is more effective when the sealing material is cured by heating.

<Liquid crystal placement process>
Next, a liquid crystal arrangement step is performed.
As the liquid crystal material, a TN type or STN type can be used. An appropriate amount of such a liquid crystal material is applied to a region surrounded by the sealing material 4 on the substrate 3 using a known technique such as a droplet discharge method. At this time, it is better to make the height after dropping as low as possible at a position as far as possible from the seal.
When the liquid crystal 5 is applied, some errors may occur and the total amount of the liquid crystal 5 may exceed the capacity of the liquid crystal cell. However, as described above, the sealing material 4 is drawn on both the upper and lower substrates 2 and 3 in advance, and is pre-cured by heating, so that even if excessive liquid crystal component presses the sealing material, a voiding phenomenon occurs. It is difficult to do.

<Board bonding process>
After the liquid crystal arrangement step, the substrates 2 and 3 are bonded together so that the sealing material 4 on the upper and lower substrates 2 and 3 is integrated. The pressure applied at the time of bonding is, for example, about 10 ⁵ Pa. In the above-described pre-curing step, the sealing material 4 is maintained in a state in which elasticity and adhesiveness are maintained, so that the upper substrate side sealing material and the lower substrate side sealing material can be integrated. Further, the interface 41 between the sealing material on the upper substrate side and the sealing material on the lower substrate side is the same material compared to the interfaces 21 and 31 between the substrate and the sealing material, so that the adhesion is much higher.

  As described above, when the substrate bonding process is performed, the excessive liquid crystal component applies pressure to the sealing material 4 from the center side of the substrate, and a conventional voiding phenomenon occurs, leading to deterioration of the quality of the liquid crystal display device. In the present embodiment, in the sealing material drawing step, the sealing materials are arranged on both the upper and lower substrates 2 and 3, and these sealing materials are integrated to seal the liquid crystal. In the entire circumference of the liquid crystal cell, the adhesion of all the interfaces between the substrate and the sealing material is high, and the phenomenon of entering voids is prevented. Furthermore, since the sealing material is precured, the phenomenon of entering voids can be further suppressed.

<Sealing material curing process>
After bonding the substrates, a sealing material curing step is performed. In this sealing material curing step, a method using various devices such as a UV lamp, a heating device, and a visible light irradiation device can be used. In this embodiment, the sealing material 4 is removed by ultraviolet irradiation using a UV lamp. Harden. Ultraviolet irradiation is performed, for example, under irradiation conditions of about 2000 to 10000 mJ / cm ² .
The liquid crystal display device 1 obtained in this way has a good display quality with suppressed voiding phenomenon.

The preferred embodiment of the present invention has been described above. However, it goes without saying that the present invention is not limited to this embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the passage of time in each step should be determined as appropriate according to conditions such as a sealing material, a liquid crystal material, and a cell thickness, and is not limited to this embodiment.
Further, the method for manufacturing a liquid crystal display device of the present invention can be applied to a passive matrix substrate in addition to an active matrix substrate. Furthermore, in the present embodiment, after the sealing material is drawn, a preliminary curing step for the sealing material is provided. However, the present invention may not include this preliminary curing step, and the preliminary curing may be performed on either the upper or lower substrate. It is possible to do only one.
In the liquid crystal arranging step, the liquid crystal 5 is arranged on the lower substrate (TFT array substrate) 3 side, but the liquid crystal 5 may be arranged on the upper substrate (counter substrate) 2 side, for example. In the above description, a UV curable & thermosetting material is used as the material of the sealing material 5. However, the liquid crystal display device manufacturing method of the present invention can also be applied to a 100% UV curable sealing material. . Even when a 100% UV curable sealant is used, heat treatment can be performed in the preliminary curing step.

It is the top view which showed the structure of the liquid crystal display device which concerns on this embodiment. It is the flowchart which showed the process of the manufacturing method of the liquid crystal of this embodiment. It is sectional drawing which showed the liquid crystal cell before the bonding process of a board | substrate. It is sectional drawing which showed the liquid crystal cell after the bonding process of a board | substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,100 ... Liquid crystal display device, 2, 3 ... Upper and lower substrates, 4,52 ... Sealing material, 5, 50 ... Liquid crystal.

Claims (7)

A method of manufacturing a liquid crystal display device in which a pair of substrates are bonded together through a sealing material,
A drawing process for drawing the sealing material on the upper and lower substrates;
A liquid crystal disposing step of disposing liquid crystal in a region surrounded by the sealing material of the upper substrate or the lower substrate;
A bonding step of bonding the upper and lower substrates by bonding the sealing material of the upper substrate and the sealing material of the lower substrate;
A method for manufacturing a liquid crystal display device, comprising: a sealing material curing step for curing the sealing material.   2. The method of manufacturing a liquid crystal display device according to claim 1, wherein in the drawing step, the sealing material is drawn in a closed ring shape on both the upper and lower substrates.   3. The method of manufacturing a liquid crystal display device according to claim 1, wherein a sealing material is disposed at a corresponding position on the upper and lower substrates in the drawing step.   The method for manufacturing a liquid crystal display device according to any one of claims 1 to 3, further comprising a preliminary curing step of the sealing material after the drawing step.   The method for manufacturing a liquid crystal display device according to claim 1, wherein the sealing material is an ultraviolet curable resin.   The method for manufacturing a liquid crystal display device according to claim 1, wherein the sealing material is a thermosetting resin. The method for manufacturing a liquid crystal display device according to claim 4, wherein the preliminary curing step is performed by heating.

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