JPH10268310A - Liquid crystal display device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the structure of a liquid crystal display device and the manufacture method there for which can reduce a cell thickness defect of a liquid crystal display cell and variance in cell shape due to thickness unevenness of an alignment layer. SOLUTION: An alignment layer 36 slightly overlaps with the formation area of seal material 40, but the external edge part 36a of the oriented film 36 is arranged a little inside the external edge 40a of the formation area of the seal material 40. Consequently, a swell part of orientation resin is not formed in the formation area of the seal material 40 and even if a swell part is formed, it is formed inside the formation area P of the seal material 40, so a defect in cell thickness, a sealing defect, and a defect in the cell shape of the liquid crystal cell due to unevenness of the contact surface of the seal material 40 which comes into contact with the substrate can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a liquid crystal display device and a method for manufacturing the same, and more particularly, to a technique for manufacturing a liquid crystal cell.

[0002]

2. Description of the Related Art Conventionally, as a liquid crystal display device, an empty cell is formed by joining two substrates made of glass or the like via a sealing material, and a liquid crystal layer is formed inside the sealing material inside the empty cell. Most have a liquid crystal display cell formed by injection.

In such a liquid crystal cell, a wiring layer, a pixel electrode, an active element, a color filter and the like are formed on the inner surface of a substrate, and an alignment film for aligning liquid crystal molecules in a predetermined direction is formed on the surface. I do. As the alignment film, an insulating film of a synthetic resin such as polyimide or polyvinyl alcohol is used. This type of alignment film is formed by applying an alignment resin on the inner surface of the substrate and then performing a drying or curing treatment. The surface of the alignment film is subjected to a rubbing treatment, and is formed so that the liquid crystal molecules in contact with the surface are aligned in a predetermined direction.

FIG. 6A schematically shows a process of applying the alignment resin on the surface of the substrate 10 by flexographic printing. In this step, the alignment resin 11 is transferred from the surface of the printing roller 12 onto the surface of the substrate 10 so that the alignment resin 11 is transferred to the substrate 1 as shown in FIG.
0 is applied on almost the entire surface.

[0005]

However, when the orientation resin 11 is applied by flexographic printing, if the printing pressure of the printing roller 12 is increased, the orientation resin 1
1, the accumulation of the alignment resin at the outer edge of the application area, that is, the periphery of the print area, and the entanglement or carry-in of dust into the alignment resin 11 become remarkable. Raised part 11 on the part
In some cases, a and 11b may be formed, causing a problem of uneven alignment of the liquid crystal layer.

Conversely, if the printing pressure of the printing roller 12 is reduced to prevent the occurrence of such a raised portion, uneven coating or streaks may occur on the entire application surface.

Further, as described above, the raised portions 11a,
If 11b is formed or the coating unevenness occurs near the outer edge of the substrate, the portion where the thickness of the alignment resin 11 fluctuates may overlap with the formation region of the sealing material.
In particular, when a cell thickness defect occurs at the peripheral portion of the liquid crystal display cell, or when the substrate is press-bonded via a sealing material, the cell shape varies greatly, and the cell gap of the liquid crystal display cell becomes non-uniform. There is a problem that the reproducibility of the cell shape is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a liquid crystal display device and a method of manufacturing the same in which a cell thickness defect or a cell shape of a liquid crystal display cell caused by uneven thickness of an alignment film is caused. It is an object of the present invention to provide a structure of a liquid crystal display device capable of reducing variations in the size and a method of manufacturing the same.

[0009]

Means taken by the present invention to solve the above-mentioned problems is to form a cell by joining two substrates via a sealing material, and to form the sealing material inside the cell. In a liquid crystal display device containing a liquid crystal layer inside, an alignment film is provided on at least one inner surface of the substrate, and an outer edge of the alignment film is located inside an outer edge of a formation region of the sealant. It is characterized by being arranged.

According to this means, since the outer edge of the alignment film is located inside the outer edge of the sealing material forming region, when the alignment film is applied, it is generated in a portion near the outer edge of the alignment film. Raised portions are less likely to occur in the sealing material forming region, and as a result, the contact surface of the substrate with the sealing material is almost flat, so that it is possible to suppress the cell thickness defect and the variation in the cell shape of the liquid crystal display cell. it can.

Here, it is preferable that an outer edge of the alignment film is disposed inside a region where the sealing material is formed.

According to this means, since the outer edge of the alignment film is arranged inside the formation region of the sealing material, the alignment film itself is not formed in the formation region of the sealing material. Since the contact surface of the substrate can be flattened, it is possible to further reduce poor cell thickness maintenance and cell shape variations of the liquid crystal display cell.

Next, in a method of manufacturing a liquid crystal display device, a cell is formed by joining two substrates via a sealing material, and a liquid crystal layer is accommodated inside the sealing material inside the cell. On at least one inner surface of the substrate,
The alignment film may be formed so that an outer edge of the alignment film is disposed inside an outer edge of a region where the sealing material is to be formed.

Here, it is preferable that the alignment film is formed such that an outer edge portion of the alignment film is disposed inside a formation region of the sealing material.

In each of the above means, it is preferable that the step of forming the alignment film includes a step of applying an alignment resin by flexographic printing.

According to this means, when the alignment resin is applied by the flexographic printing method, even if a raised portion is formed in a region near the outer edge portion of the applied alignment resin, it is arranged in the formation region of the sealing material. Therefore, the degree of freedom in printing conditions such as printing pressure is increased, and an alignment film can be easily formed.

Further, after the formation of the alignment film, the two substrates are overlapped with each other via the sealing material and pressurized, and in this state, a temporary curing step of incompletely curing the sealing material is provided. After that, it is preferable to have a main curing step of releasing the pressing force to completely cure the sealing material.

According to this means, it is possible to release the pressing force in a state where the sealing material is incompletely cured in the temporary curing step, and to realize a substantially flat cell shape by the restoring force at that time. The cell shape can be fixed in the main curing step. In this case, in particular, since the contact surface of the substrate with respect to the sealing material is formed almost flat, it is possible to reduce the variation in the cell shape and improve the uniformity of the cell gap and the reproducibility of the cell shape of the liquid crystal display cell. Can be done.

[0019]

Next, an embodiment according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a plan view showing a planar structure of a liquid crystal display cell in an embodiment of a liquid crystal display device according to the present invention. FIG. 2 schematically shows a cross-sectional structure of the liquid crystal display cell shown in FIG.

On the inner surface of the element substrate 20, a wiring layer (not shown), a TFT (thin film transistor) element, a pixel electrode and the like are formed in the liquid crystal display area 21, and an alignment film is formed thereon via an insulating film. It is formed almost entirely. A sealing material 40 is applied on the element substrate 20 so as to surround the liquid crystal display area 21, and the opposing substrate 30 is pressed through the sealing material 40.

On the inner surface of the counter substrate 30, a wiring layer, a pixel electrode and the like (not shown) are formed in the liquid crystal display area 31, and a color filter is formed thereon.
A black matrix layer 3 is provided on the outer edge of the color filter.
2 is formed so as to surround the liquid crystal display area 31, and the above-mentioned sealing material 40 is arranged outside the liquid crystal display area 31.

The element substrate 20 and the counter substrate 30 overlap each other in the liquid crystal display regions 21 and 31 and the formation region of the sealing material 40 disposed outside the liquid crystal display regions 21 and 31. The external connection portion 22 formed outside the sealing material 40 and extending so as not to overlap the counter substrate 30 is formed on the element substrate 20.
On the other hand, on the counter substrate 30, an external connection portion 33 formed outside the sealing material 40 and protruding so as not to overlap the element substrate 20 is provided.

On the surfaces of the external connection portions 22 and 33, a number of wiring layers formed in the liquid crystal display regions 21 and 31 are led out as they are, and external terminals (not shown) are formed at their ends. These external terminals are for transmitting a drive voltage supplied from a liquid crystal drive circuit to a wiring layer in a liquid crystal display cell. The external terminals may be connected to the liquid crystal drive circuit via a flexible circuit board or the like, and constitute at least a part of the liquid crystal drive circuit directly mounted on the external connection portions 22 and 33 as shown. In some cases, external terminals are connected to the integrated circuits 23 and 34 to be connected to an external signal circuit or the like via the integrated circuits 23 and 34.

The alignment film formed on the element substrate 20 covers almost the entire surface of the element substrate 20 as shown in FIG. As shown in FIG. 2B, is formed by application in a limited area such that the outer edge portion comes inside the outer edge of the formation area of the sealing material 40.

FIG. 3 is an enlarged sectional view showing the vicinity of the area where the sealing material 40 is formed in the liquid crystal display cell. Element substrate 2
A plurality of wiring layers 24 are formed on the surface of the “0”, and are drawn out from the liquid crystal display area 21 onto the external connection section 22. An insulating film 25 is deposited on the wiring layer 24, and an alignment film 26 is formed thereon.

A wiring layer and a pixel electrode (not shown) are also formed on the inner surface of the counter substrate 30. A color filter 35 is formed thereon, and a black matrix layer 32 is formed on the outer edge thereof. . A transparent protective film 35a is formed on the surface of the color filter 35, and an alignment film 36 is further formed thereon.

The alignment film 36 has a region P where the sealing material 40 is formed.
Although slightly overlapping, the outer edge 36a of the alignment film 36 is disposed inside the outer edge 40a of the formation region P of the sealing material 40. As a result, the sealing material 4
6B, the raised portions 11a and 11b as shown in FIG. 6B are not formed. Even if the raised portions 11a and 11b are formed, the sealing material 40 is not formed.
Is formed inside the formation region P of
It is possible to suppress occurrence of defective cell thickness, defective sealing, and defective cell shape of the liquid crystal display cell due to unevenness of the contact surface of the substrate with the sealing material 40.

The outer edge 36a of the alignment film 36 is
It is preferable to be located on the inner side of 1/3 of the width of the 0 forming region P. Even if there is no raised portion of the alignment film 36 in the region where the sealing material 40 is formed, the presence of the alignment film 36 itself on the adhesion surface may cause poor adhesion or poor sealing. It is better to be inside as much as possible. In particular, it is most preferable that the outer edge portion 36a of the alignment film 36 is disposed further inside than the formation region P of the sealing material 40. This is because the alignment film 36 is not formed in the formation region P of the seal material 40, so that the influence of the alignment film on the seal material 40 can be completely eliminated.

FIG. 4 shows an alignment film 3 on the inner surface of a counter substrate 30.
6 schematically shows a step of applying an alignment resin for forming the resin layer 6 by flexographic printing. As shown in FIG. 4A, a pallet 50 having a plurality of accommodation recesses capable of accommodating the opposite substrate 30 is prepared, and the opposite substrate 30 is accommodated in each of the accommodation recesses. This pallet 50
Is pressed while the peripheral surface of the print roller 12 is pressed at a predetermined pressure, and the print pattern 12 a of the oriented resin applied on the peripheral surface of the print roller 12 is transferred onto the inner surface of the counter substrate 30. .

Here, the print pattern 12a is formed on the inner surface of the counter substrate 30 in a print area 39 (FIG. 3) defined inside the outer edge of the seal material 40 forming area shown in FIG.
And FIG. 4A).

The alignment resin applied by the above-described flexographic printing is subjected to a drying process or a curing process to obtain an alignment film 36.
Becomes Rubbing is performed on the alignment film 36 in a predetermined direction.

Similar to the above, the alignment film 26 is formed almost entirely on the inner surface of the element substrate 20, and when individual processing steps for the element substrate 20 and the counter substrate 30 are completed, the substrate shown in FIG. Proceed to the sticking step. In this substrate attaching step, first, a sealing material 40 made of an uncured photocurable resin is applied on the surface of the element substrate 20 in a plane pattern as shown in FIG. 1 by a dispenser or the like.
As shown in FIG. 5A, the opposing substrate 3 is placed on the element substrate 20.
The element substrate 20 and the opposing substrate 30 are press-bonded with a predetermined pressing force via a sealing material by a press-fitting head or the like (not shown). Here, both substrates are bent as shown in the figure due to the pressing force.

Here, the manner of bending of the substrate varies depending on the state of the pressure bonding step. The case shown in FIG. 5A occurs in the following situation. First, the formation of an alignment film is performed while the element substrate 20 is still a large-sized original substrate including a plurality of liquid crystal display areas 21, and the original substrate is placed on a base plate on which a cushioning material is laid. In this state, a sealing material is applied around each liquid crystal display area 21. Next, the opposing substrate 30 is supplied onto the original substrate in the form of a small substrate including only a single liquid crystal display area 31, and one of the opposing substrates 30 is pressed by a pressure bonding head via a sealing material 40 to be pressed. Press on top.
At this time, if the pressing force of the pressure bonding head is somewhat large, the original substrate placed on the buffer material is more curved than the counter substrate 30, and as shown in FIG. The cell gap is large at the portion and the cell gap is small at the periphery of the cell.

In this crimped state, the sealing material 4
A temporary curing step of irradiating light such as ultraviolet rays to 0 to incompletely cure the sealing material 40 is performed. The degree of this curing
It is determined according to the cell shape at the time of releasing the pressing force described later.

When the pre-curing of the sealing material is completed, FIG.
As shown in (b), the pressure of the pressure bonding head is released. When the pressing force disappears, the element substrate 20 and the counter substrate 30
Attempts to eliminate the deformation at the time of pressurization and return to the original shape, but to some extent due to incompletely hardened sealing material, the restored shape is limited to some extent by the binding force of the sealing material Is done.

The restored shape of the cell when the pressure is released is:
It depends on the pressure applied by the pressure bonding head and the degree of hardening of the sealing material. The pressing force and the degree of hardening are set such that the element substrate 20 and the opposing substrate 30 are substantially flat in the restored shape of the cell, or the cell gap at the center of the cell is so large that variations in the cell gap do not become a significant problem in display. It is adjusted appropriately so as to be slightly larger than the cell gap at the peripheral portion.

The reason why the cell gap at the center of the cell is adjusted to be slightly large is that when liquid crystal is injected from the outside into the reduced-pressure cell based on the pressure difference between inside and outside in the liquid crystal injection step. This is because it is necessary to ensure that the liquid crystal is sufficiently injected, and that the cell gap at the center may be slightly reduced after the injection of the liquid crystal.

Finally, as shown in FIG. 5 (c), a main curing step of completely curing the sealing material is performed by irradiating the cell with light without applying pressure. In this main curing step, the shape of the empty cell is fixed with the restored shape shown in FIG. 5B.

According to the present embodiment, since the alignment resin is applied so that the outer edge of the alignment film is disposed inside the outer edge of the formation region of the sealing material 40, the ridge rises at the outer edge of the application region of the alignment resin. Even when the portion is formed, the raised portion is less likely to be generated on the seal material forming region, so that a defective cell gap near the seal material can be prevented.

Further, as shown in FIG. 5, a temporary curing step of incompletely curing the sealing material in a state where the two substrates are pressed and pressed to each other via the sealing material, and thereafter, the pressing force is reduced. When the main curing step of completely curing the sealing material after release is provided, as in the related art, if there is a raised portion of the alignment film in the application forming region of the sealing material, the empty cell at the time of releasing the pressing force. However, there is a problem that the cell shape becomes uneven, the cell shape becomes non-reproducible, and a good shape of the liquid crystal display cell cannot be obtained. On the other hand, in the present embodiment, since the raised portion of the alignment film is not formed in the formation region of the sealing material, the uniformity of the cell gap of the empty cell and the reproducibility of the cross-sectional shape as described above can be obtained. The shape of the liquid crystal display cell can be improved.

In the above embodiment, the application range of the alignment resin is limited only on the inner surface of the counter substrate 30 so that the outer edge of the alignment film is inside the outer edge of the sealing material forming region. However, also in the element substrate 20,
Similarly, the orientation resin may be printed and applied in a limited application range.

In both the element substrate 20 and the opposing substrate 30, the outer edge of the sealing material forming region on the side where the external connection portions 22 and 33 are extended is oriented outward from the outer edge. In some cases, no problem occurs even if the outer edge of the film is located. This is the case where the outer edge of the alignment film is located inside the external connection portions 22 and 33, and the outer edge is sufficiently away from the seal material forming region to the outside. As described above, when the inner surface of the substrate is formed to extend sufficiently outside the seal material forming region, on the contrary, the outer edge of the alignment film is positioned outside the seal material forming region. The formation can prevent the raised portion from being located in the formation region of the sealing material.

[0043]

As described above, according to the present invention, the following effects can be obtained.

According to the first or third aspect, since the outer edge of the alignment film is located inside the outer edge of the sealing material forming region, when the alignment film is applied, the outer edge of the alignment film is formed. The bulges that occur in the close part are less likely to occur in the seal material forming region, and as a result, the contact surface of the substrate with the seal material becomes almost flat, so that the cell thickness of the liquid crystal display cell is poor and the cell shape is uneven. Can be suppressed.

According to the second or fourth aspect, since the outer edge of the alignment film is disposed inside the formation region of the sealing material, the alignment film itself is not formed in the formation region of the sealing material.
As a result, the contact surface of the substrate with respect to the sealing material can be flattened, so that it is possible to further reduce the failure in maintaining the thickness of the liquid crystal display cell and the variation in the cell shape.

According to the fifth aspect, when the alignment resin is applied by the flexographic printing method, even if a raised portion is formed in a region near the outer edge portion of the applied alignment resin, the sealing material formation region is not formed. Since it is difficult to dispose them, the degree of freedom in printing conditions such as printing pressure is increased, and an alignment film can be easily formed.

According to the sixth aspect, it is possible to release the pressing force in a state where the sealing material is incompletely cured in the temporary curing step, and to realize a substantially flat cell shape by the restoring force at that time. The cell shape can be fixed in the main curing step. In this case, in particular, since the contact surface of the substrate with respect to the sealing material is formed almost flat, it is possible to reduce the variation in the cell shape and improve the uniformity of the cell gap and the reproducibility of the cell shape of the liquid crystal display cell. Can be done.

[Brief description of the drawings]

FIG. 1 is a plan view of a liquid crystal cell for showing an embodiment according to the present invention.

FIG. 2 is a schematic schematic longitudinal sectional view of the liquid crystal cell in the embodiment.

FIG. 3 is an enlarged vertical cross-sectional view showing the vicinity of a formation region of a sealing material of the liquid crystal cell in the same embodiment.

FIG. 4 is a schematic plan view (a) and a schematic side view (b) showing an application process of the alignment resin according to the flexographic printing method in the same embodiment.

FIG. 5 is a schematic process diagram showing a substrate pressure bonding step (a), a sealing material temporary curing step (b), and a sealing material main curing step (c) in the same embodiment.

FIG. 6A is a schematic cross-sectional view showing a coating process of a conventional alignment resin by flexographic printing, and FIG. 6B is a schematic cross-sectional view showing a coating state of the alignment resin.

[Explanation of symbols]

 Reference Signs List 20 element substrate 21, 31 liquid crystal display area 22, 33 external connection part 23, 34 integrated circuit 26, 36 alignment film 36a outer edge 39 coating area 40 sealing material 40a outer edge 50 pallet P sealing material forming area

Claims (6)

[Claims] 1. A liquid crystal display device comprising two substrates joined together via a sealing material to form a cell, and a liquid crystal layer contained inside the sealing material inside the cell. A liquid crystal display device having an alignment film on at least one inner surface, wherein an outer edge of the alignment film is disposed inside an outer edge of a region where the sealant is formed. 2. The liquid crystal display device according to claim 1, wherein an outer edge of the alignment film is disposed inside a region where the sealing material is formed. 3. A method for manufacturing a liquid crystal display device, comprising: joining two substrates via a sealing material to form a cell; and accommodating a liquid crystal layer inside the sealing material inside the cell. Liquid crystal, wherein the alignment film is formed on at least one inner surface of the substrate so that an outer edge of the alignment film is disposed inside an outer edge of a region where the sealing material is to be formed. A method for manufacturing a display device. 4. The method for manufacturing a liquid crystal display device according to claim 3, wherein the alignment film is formed such that an outer edge of the alignment film is arranged inside a region where the sealant is to be formed. 5. The method for manufacturing a liquid crystal display device according to claim 3, wherein the step of forming the alignment film includes a step of applying an alignment resin by flexographic printing. 6. The method according to claim 3, wherein after the alignment film is formed, the two substrates are superimposed on each other with the sealing material interposed therebetween and pressurized. A method for manufacturing a liquid crystal display device, comprising: a temporary curing step of incompletely curing; and a main curing step of releasing the pressing force to completely cure the sealing material.