Liquid crystal display device

A liquid crystal display device includes a TFT substrate having a first alignment film formed on part of an inorganic insulating film, an overcoat film formed on a black matrix, a counter substrate having a second alignment film formed on the overcoat film, and a seal portion including a sealant. The TFT substrate is bonded to the counter substrate by the sealant. The sealant is bonded to the inorganic insulating film at the seal portion on the side where the TFT substrate is formed, with the first alignment film not being provided on the side, and, in the seal portion on the side where the counter substrate is formed, the sealant is bonded to the second alignment film but, is not bonded to the overcoat film.

CLAIM OF PRIORITY

The present application claims priority from Japanese Patent Application JP 2010-217063 filed on Sep. 28, 2010, the content of which is hereby incorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display device. The invention particularly relates to an IPS liquid crystal display device in which the reliability of a seal portion is improved.

2. Description of the Related Art

A liquid crystal display device includes a TFT substrate having pixel electrodes, thin film transistors (TFT), or the like formed thereon in a matrix form, and a counter electrode opposing the TFT substrate and having color filters, or the like formed at positions corresponding to the pixel electrodes of the TFT substrate. Liquid crystal is put between the TFT substrate and the counter substrate. The liquid crystal display device controls light transmittance for each pixel by using liquid crystal molecules to form images.

Since the liquid crystal display devices are flat and light in weight, their application has been generalized in various fields including large-sized display devices such as television sets, mobile phones, DSCs (Digital Still Cameras), or the like. In contrast, the liquid crystal display devices involve a problem in terms of viewing angle characteristics. The viewing angle characteristics are a phenomenon that the brightness or chromaticity changes between when a screen is observed from the front and when the screen is observed in the oblique direction. The IPS (In Plane Switching) mode of operating liquid crystal molecules by a horizontal electric field has satisfactory viewing angle characteristics.

In the IPS mode, preferred characteristics are obtained when a pre-tilt angle is not formed with respect to liquid crystal molecules near an alignment film. Accordingly, it is advantageous to form the axis of orientation for the alignment film not by a rubbing method but by an optical alignment method. The optical alignment method also has an advantage over the rubbing method in that static electricity is not generated.

In optical alignment method, a polarized UV light is radiated to an alignment film, and thereby, such anisotropy that liquid crystal molecules are aligned in a predetermined direction, is provided to the alignment film. JP-A-2005-351924 describes a technique relating to such optical alignment.

SUMMARY OF THE INVENTION

Optical alignment is performed by radiating ultraviolet light polarized in a predetermined direction to an alignment film formed of a polymer. For example, when a polarized UV light is radiated to a polymer formed in a network shape, polymer formed in a predetermined direction relative to the direction in which the ultraviolet light is polarized, is destroyed. Then, anisotropy is formed in the alignment film for aligning liquid crystal molecules. No problem occurs so long as the polarized ultraviolet light for optical alignment is radiated only to the alignment film. However, if the ultraviolet light is radiated to a portion other than the alignment film, the radiated portion is deteriorated by the ultraviolet light to result in a problem. Such a problem is particularly significant when the material radiated by the ultraviolet light is an organic material.

FIG. 8is a cross sectional view of a seal portion that is included in a liquid crystal display panel having a conventional structure, which shows a problem occurring when optical alignment is performed on an alignment film113. The configuration shown inFIG. 8is hereinafter referred to as Comparative Example 1. InFIG. 8, a liquid crystal layer300is put between a TFT substrate100formed with TFTs, etc. and a counter substrate200formed with a color filter201, etc., and the liquid crystal layer300is sealed by a sealant150. In the seal portion, a gate insulating film102, an inorganic passivation film106, and an interlayer insulating film109are formed above the TFT substrate100. A detailed cross sectional structure is to be described later. A black matrix202and an overcoat film203are formed above the counter substrate200. The sealant150is formed between the interlayer insulating film109of the TFT substrate100and the overcoat film203. The alignment film113for aligning liquid crystals is not formed at a portion of the sealant150.

FIG. 9is a schematic view when optical alignment is performed on the alignment film113of the counter substrate200. InFIG. 9, optical alignment is performed on the alignment film113by radiating a polarized UV light to the counter substrate200formed with the alignment film113. Since the alignment film113is not formed at the seal portion, the ultraviolet light is radiated directly to the overcoat film203. Then, the overcoat film203is deteriorated by the ultraviolet light to form a deteriorated portion2031of the overcoat film on the surface of the overcoat film203. The deteriorated portion2031of the overcoat film tends to allow moisture to permeate therethrough.

In contrast, on the side where the TFT substrate100is formed, while the interlayer insulation film109is exposed at a portion where the alignment film113is not formed, the interlayer insulating film109is formed of SiN and not deteriorated by the ultraviolet light. Accordingly, even when optical alignment is performed by the ultraviolet light, problem as shown inFIG. 9does not occur on the side of the TFT substrate100.

When a liquid crystal panel is formed by using the thus formed counter substrate200and TFT substrate100, the deteriorated portion2031of the overcoat film is present in the seal portion of the counter substrate200as show inFIG. 8. Therefore, moisture permeates through the portion to thereby deteriorate the life characteristic of the liquid crystal display panel. As a specific problem, moisture that has intruded into the liquid crystal display panel may swell to cause peeling of the seal portion.

FIG. 10shows an example in which an alignment film113is formed on each of the TFT substrate100and the counter substrate200as far as the seal portion so that the deteriorated portion2031of the overcoat film on the side of the counter substrate200is not formed as shown inFIG. 8. The configuration shown inFIG. 10is hereinafter also referred to as Comparative Example 2. When optical alignment is performed on the side of the counter substrate200as shown inFIG. 10, since the alignment film113is formed as far as the seal portion, the overcoat film203is not deteriorated by the ultraviolet light.

However, the configuration shown inFIG. 10results in a problem of adhesion between the alignment film113and the interlayer insulating film109on the side of the TFT substrate100as shown inFIG. 11. The liquid crystal display panel undergoes various vibrations and impact shocks during use. Accordingly, when the adhesion between each of the films is weak, inter-film peeling occurs when vibrations, or the like are exerted.

InFIG. 10orFIG. 11, the alignment film113is an organic film formed of polyimide, etc. and the interlayer insulating film109is an inorganic film formed of SiN, etc. Generally, adhesion between an organic film and an inorganic film is weak. In contrast, since the sealant150is an adhesive material, adhesion between the sealant150and the alignment film113is strong. Further, on the side of the counter substrate200, both of the overcoat film203and the alignment film113are organic films. Adhesion between the organic films is also strong.

When vibrations, or the like are exerted on the liquid crystal display panel having such a configuration, the stress is caused in the seal portion. Thus, peeling occurs between the alignment film113and the interlayer insulating film109in the seal portion on the side of the TFT substrate100. This is because the alignment film113is an organic film and the interlayer insulating film109is an inorganic film formed of SiN, etc., and adhesion between them is weak.

As described above, it is not easy to attain compatibility between the arrangement for moisture penetration prevention and the arrangement for withstanding vibrations and impact shocks. The present invention intends to attain a liquid crystal display panel capable of preventing moisture from penetrating and having sufficient mechanical margin also for vibrations, etc.

The present invention intends to solve the problems describe above and has a specific constitution as described below.

(1) A liquid crystal display panel includes: a TFT substrate having a first alignment film formed on part of an inorganic insulating film; an overcoat film formed on a black matrix; a counter substrate having a second alignment film formed on the overcoat film; and a seal portion including a sealant; the TFT substrate being bonded to the counter substrate by the sealant, wherein the sealant is bonded to the inorganic insulating film at the seal portion on the side where the TFT substrate is formed, with the first alignment film being not provided on the side, and wherein, in the seal portion on the side where the counter substrate is formed, the sealant is bonded to the second alignment film but is not bonded to the overcoat film.

(2) A liquid crystal display panel includes: a TFT substrate having a first alignment film formed on part of an inorganic insulating film; an overcoat film formed on a black matrix; a counter substrate having a second alignment film formed on the overcoat film; and a seal portion including a sealant; the TFT substrate being bonded to the counter substrate by the sealant, wherein the sealant is bonded to the inorganic insulating film at the seal portion on the side where the TFT substrate is formed, with the first alignment film being not provided on the side, and wherein, in the seal portion on the side where the counter substrate is formed, the sealant is bonded to the second alignment film at part of the seal portion, the part of the seal portion being on the side of the end of the counter substrate with respect to the center of the seal portion, and the sealant at another part of the seal portion is bonded to the overcoat film.

As another means, in the seal portion on the side where the counter substrate is formed, the sealant is bonded to the second alignment film at first part of the seal portion, the first part of the seal portion being on the side of the end of the counter substrate with respect to the center of the seal portion, the sealant is bonded to the second alignment film at second part of the seal portion, the second part of the seal portion being on the center side of the counter substrate with respect to the center of the seal portion, and the sealant is bonded to the overcoat film at part other than the first part and the second part of the seal portion.

(3) A liquid crystal display panel includes: a TFT substrate having a first alignment film formed on part of an inorganic insulating film; an overcoat film formed on a black matrix; a counter substrate having a second alignment film formed on the overcoat film; and a seal portion including a sealant; the TFT substrate being bonded to the counter substrate by the sealant, wherein, in the seal portion on the side where the TFT substrate is formed, the sealant is bonded to the first alignment film at part of the seal portion, the part of the seal portion being on the side of the end of the TFT substrate with respect to the center of the seal portion, and the sealant at another part of the seal portion is bonded to the inorganic insulating film, and wherein, in the seal portion on the side where the counter substrate is formed, the sealant is bonded to the second alignment film at part of the seal portion, the part of the seal portion being on the side of the end of the counter substrate with respect to the center of the seal portion, and the sealant at another part of the seal portion is bonded to the overcoat film. That is, in the third means, the pattern of the first alignment film on the side of the TFT substrate is identical with the pattern of the second alignment film.

According to the first means of the invention, when optical alignment is performed using ultraviolet light, the ultraviolet light is not radiated directly to the overcoat film so that the overcoat film is not deteriorated, which can prevent intrusion of moisture from the deteriorated portion of the overcoat film.

According to the second means of the invention, in the seal portion on the side where the counter substrate is formed, the sealant is bonded to the alignment film at part of the seal portion, and the sealant at another part of the seal portion is bonded to the overcoat film. When optical alignment is performed, the overcoat film is deteriorated at the portion where the sealant is in direct contact with the overcoat film. However, since the moisture is blocked at a portion where the sealant is bonded to the alignment film, intrusion of the moisture can be prevented. In contrast, since a portion where the sealant is bonded to the overcoat film is also present, the bonding strength of the sealant can also be ensured sufficiently.

According to the third means of the invention, since, also on the side of the TFT substrate, a portion of the sealant is in contact with the alignment film and other portion thereof is in contact with the inorganic insulating film, prevention for the moisture intrusion and reliability for the seal portion can be attained simultaneously. At the same time, since an identical printing plate can be used for the counter substrate and the TFT substrate when the alignment film is printed, manufacturing cost of the liquid crystal display panel can be decreased.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Before examples of the invention are explained, a configuration of an IPS liquid crystal display panel to which the invention is applied is to be described.FIG. 1is a cross sectional view showing a structure in a display region of the IPS liquid crystal display device. Various electrode structures have been proposed for the IPS liquid crystal display device and put to practical use. The structure inFIG. 1is a structure used generally at present. To put it simply, a comb-shape pixel electrode110is formed above a counter electrode108formed in a planar solid pattern so that an insulating film is put between the comb-shape pixel electrode110and the counter electrode108. Then, the light transmittance of a liquid crystal layer300is controlled for each pixel by rotation of liquid crystal molecules301by a voltage between the pixel electrode110and the counter electrode108so that images are formed.

The structure shown inFIG. 1is to be described specifically. While the invention is to be described with reference to the configuration inFIG. 1as an example, the invention is also applicable to IPS liquid crystal display devices other than that shown inFIG. 1.

InFIG. 1, a gate electrode101is formed on a TFT substrate100formed of glass. The gate electrode101is formed in a layer identical with that on which a scanning line is formed. The gate electrode101comprises an MoCr alloy laminated on an AlNd alloy.

A gate insulating film102is formed of SiN and covers the gate electrode101. A semiconductor layer103is formed on the gate insulating film102so that the semiconductor layer103faces the gate electrode101. The semiconductor layer103is formed of an a-Si film. The a-Si film is formed by plasma CVD. The a-Si film forms a channel of TFT, and a source electrode104and a drain electrode105are formed on the a-Si film putting the channel therebetween. A n+Si layer not illustrated is formed between the a-Si film and the source electrode104or the drain electrode105. This is for establishing ohmic contact between the semiconductor layer and the source electrode104or the drain electrode105.

The source electrode104also serves as a video signal line, and the drain electrode105is connected with a pixel electrode110. Both the source electrode104and the drain electrode105are formed simultaneously in one identical layer. An inorganic passivation film106is formed of SiN and covers TFT. The inorganic passivation film106protects the TFT, particularly, the channel against impurity. An organic passivation film107is formed on the inorganic passivation film106. Since the organic passivation film107also has a function of protecting the TFT and planarizing the surface of TFT, it is formed to have a large thickness. The thickness is from 1 μm to 4 μm. A through hole is formed in the organic passivation film.

A counter electrode108is formed on the organic passivation film107. The counter electrode108is formed of ITO (Indium Tin Oxide) as a transparent conductive film. An interlayer insulating film109is formed of SiN and covers the counter electrode108. A through hole111is formed by etching the interlayer insulating film109and the inorganic passivation film106in this step. Subsequently, ITO as the pixel electrode110is deposited covering the interlayer insulating film109and the through hole111and then patterned.

The pixel electrode110is a so-called comb-shape electrode. A slit112is formed between comb-shape electrodes adjacent to each other. A predetermined voltage is applied to the counter electrode108, and a voltage due to video signals is applied to the pixel electrode110. When the voltage is applied to the pixel electrode110, a line of electric force is generated as shown inFIG. 1, and a liquid crystal molecule301is rotated in the direction of the line of electric force to control the transmission of light from a back light. Since the transmission of light from the back light is controlled for each pixel, and then, images are formed. An alignment film113on the side of the TFT substrate is formed on the pixel electrode110for aligning the liquid crystal molecule301. Alignment to be performed on the alignment film113is optical alignment by a polarized UV light.

In the example ofFIG. 1, a counter electrode108formed in a planar shape is disposed over the organic passivation film107, and the comb-shape electrode110is disposed on the interlayer insulating film109. In contrast, the pixel electrode110formed in a planar shape may sometimes be disposed on the organic passivation film107and the comb-shape counter electrode108may be disposed on the interlayer insulating film109.

InFIG. 1, a counter substrate200is disposed with the liquid crystal layer300put between the counter substrate200and the TFT substrate. A color filter201is formed on the inside of the counter substrate200. A black matrix202has a function of improving the contrast of the images and also acts as a light shielding film for the TFT to prevent photo-current from flowing to the TFT.

An overcoat film203is formed covering a color filter201and the black matrix202. Since the surface of the color filter201and the black matrix202is uneven, the surface thereof is planarized by the overcoat film203. An alignment film113for determining the initial alignment of the liquid crystal molecule301is formed on the overcoat film203. The alignment film113is subjected to optical alignment.

An outer conductive film210is formed to the outside of the counter substrate200by the sputtering of ITO. The outer conductive film210is formed to stabilize the inner electric field of the liquid crystal display panel.

FIG. 2is a cross sectional view of a seal portion of the liquid crystal display panel in this example and this is a cross sectional view of the seal portion of the IPS liquid crystal display panel described with reference toFIG. 1. InFIG. 2, the external conductive film formed on the side of the counter substrate200is not illustrated.

InFIG. 2, a gate insulating film102, an inorganic passivation film106, an organic passivation film107, an interlayer insulating film109, and an alignment film113are stacked on a TFT substrate100. The organic passivation film107is for planarizing the display region and not extended as far as the seal portion. The interlayer insulating film109formed on the organic passivation film107extends as far as the end of the TFT substrate100. The alignment film113is formed covering the interlayer insulating film109.

A color filter201and a black matrix202and an over coat film203are formed on the side where the counter substrate200inFIG. 2is formed and the overcoat film203covers the color filter201and black matrix202. A columnar spacer160defining the distance between the TFT substrate100and the counter substrate200is formed on the overcoat film203. An alignment film113is formed covering the overcoat film203and the columnar spacer160. The TFT substrate100and the counter substrate200are sealed by a sealant150, and liquid crystals are filled in the inside of the liquid crystal display panel. For example, an epoxy resin is used for the sealant150.

The alignment film113is subjected to optical alignment both on the side of the TFT substrate100and on the side of the counter substrate200. This example has a feature that the alignment film113on the side of the counter substrate200is formed as far as the end of the counter substrate200but the alignment film113on the side of the TFT substrate is not formed as far as the portion below the sealant150. InFIG. 2, when the alignment film113on the side of the counter substrate200is subjected to optical alignment by ultraviolet light, since the overcoat film203is entirely covered with the alignment film113, the overcoat film203is not deteriorated. Accordingly, there is no problem that the moisture intrudes from the deteriorated portion of the overcoat film203to deteriorate the reliability of the liquid crystal display panel.

In contrast, on the side of the TFT substrate100, while the alignment film113is formed in the display region, it is not formed as far as the seal portion. In this case, the interlayer insulating film109in the seal portion, which is not covered with the alignment film113, undergoes the radiation of the ultraviolet light during optical alignment. However, since the interlayer insulating film109is formed of an inorganic film such as SiN, it is not deteriorated by the ultraviolet light.

According to the structure inFIG. 2, since no portions present both on the side of the TFT substrate100and on the side of the counter substrate200are deteriorated by the ultraviolet light upon optical alignment, intrusion of moisture from the seal portion can be prevented. Further, in the structure ofFIG. 2, film peeling in the seal portion due to mechanical vibrations, or the like is not caused. That is, all of the insulating layers in the seal portion are inorganic films on the side of the TFT substrate100and bonding strength between each of them is strong. Further, on the side of the counter substrate200, all of the layer structures in the seal portion are organic films and bonding strength between each of them is strong. Further, the sealant150is an adhesive material and has a strong bonding strength both with the alignment film113on the side of the counter substrate200and the SiN film on the side of the TFT substrate100.

As described above, according to Example 1, intrusion of moisture due to the deterioration of the overcoat film203can be prevented and film peeling due to mechanical vibrations, or the like is not caused.

FIG. 3is a cross sectional view showing a second example according to the invention. InFIG. 3, description for the structure identical with that inFIG. 2is omitted. In the counter substrate200ofFIG. 3, while the alignment film113is formed for the display region and at the end of the counter substrate200, the alignment film113is not formed at the portion where the sealant150is formed except for the end of the counter substrate200.

When optical alignment is performed on the counter substrate200as described above, the overcoat film203at the portion not covered with the alignment film113is deteriorated by the ultraviolet light. However, since a portion A where the alignment film113is formed overlapping the portion formed with the sealant150is present, deterioration of the overcoat film203is not caused in the portion A. Accordingly, since moisture from the outside is blocked at the portion A, the inside of the liquid crystal display panel is protected against intrusion of the moisture.

The bonding strength between the sealant150and the alignment film113is lower than the bonding strength between the sealant150and the overcoat film203. In this example, since the sealant150and the overcoat film203are in contact over a wide range, the mechanical strength against vibrations, or the like is stronger compared with Example 1

FIG. 4is a cross sectional view showing another embodiment of Example 2.FIG. 4is different fromFIG. 3in the structure in the seal portion of the counter substrate200. InFIG. 4, the alignment film113overlaps the sealant150at the inside and the outside thereof. When the counter substrate200shown inFIG. 4is subjected to optical alignment, the overcoat film203at a portion not covered with the alignment film113is deteriorated by the ultraviolet light.

However, since portions A and B where the sealant150overlaps the alignment film113are present at the inside and the outside of the sealant150, the overcoat film203is not deteriorated at the portions A and B and intrusion of moisture from the outside can be prevented at the portions A and B. Further, at the portion where the alignment film113does not overlap the sealant150, since the sealant150and the overcoat film203are in direct contact with each other, the bonding strength between the sealant150and the overcoat film203is strong.

As described above, also this embodiment can provide a liquid crystal display panel capable of preventing intrusion of the moisture from the outside and having high mechanical strength against vibrations, or the like. While this embodiment has higher blocking performance against intrusion of the moisture compared with the first embodiment, the strength against mechanical vibrations, or the like is inferior to that of the first embodiment. However, any of the embodiments is within a range of practical use.

FIG. 5is a cross sectional view showing a third example according to the invention.FIG. 5is different fromFIG. 3in the structure of the TFT substrate100in the seal portion. In the TFT substrate100ofFIG. 5, while the alignment films113is formed in the display region and at the end of the counter substrate200, the alignment film113is not formed at the portion where the sealant150is formed except for the outer side. That is, inFIG. 5, the range over which the alignment film113extends on the side of the TFT substrate100is identical with that on the side of the counter substrate200.

The alignment film113is generally formed by flexographic printing. When the range over which the alignment film113extends on the side of the counter substrate200is identical with that on the side of the TFT substrate100, one printing plate will suffice. In contrast, in Example 1 and Example 2, two flexographic printing plates are necessary for the TFT substrate100and for the counter substrate200. In this regard, this example is superior to Example 1 and Example 2 in mass productivity.

InFIG. 5, the function on the side of the counter substrate200is identical with that described in Example 2. On the side of the TFT substrate100, a portion where the sealant150overlaps the alignment film113is present on the outer side of the TFT substrate100. In contrast, the sealant150and the interlayer insulating film109formed of SiN are in direct contact with each other at other portion. Accordingly, the bonding strength between the sealant150and the TFT substrate100is also strong enough.

FIG. 6is a cross sectional view showing a second embodiment of this example. InFIG. 6, the structure on the side of the counter substrate200is identical with that inFIG. 4according to the second embodiment of Example 2. Accordingly, the function on the side of the counter substrate200is identical with that described in the second embodiment of Example 2. In contrast, the range over which the alignment film113extends on the side of the TFT substrate100inFIG. 6is identical with the range over which the alignment film113extends on the side of the counter substrate200.

On the side of the counter substrate200inFIG. 6, intrusion of the moisture from the outside is blocked at a portion where the alignment film113overlaps the overcoat film203, that is, at the portion A and the portion B in the seal portion. Further, the bonding strength between the counter substrate200and the sealant150is ensured at the portion where the sealant150and the overcoat film203are in direct contact with each other. On the side of the TFT substrate100inFIG. 6, the bonding strength is ensured at a portion where the sealant150and the interlayer insulating film109formed of SiN are in direct contact with each other.

As described above, in any of the embodiments of this example, intrusion of the moisture into the liquid crystal display panel can be prevented and the strength against mechanical vibrations, or the like can be ensured.

FIG. 7is a table showing comparison of structure between each of the examples of the invention described above and the comparative example described in the paragraph for the summary of the invention. The structure shown inFIG. 8is Comparative Example 1 and the structure shown inFIG. 10is Comparative Example 2, which have been explained in the summary of the invention. Example 2 inFIG. 7has a structure shown inFIG. 3and the Example 3 has a structure shown inFIG. 5.

InFIG. 7, PCT (Pressure Cooker Test) was performed as a test for evaluating the durability against moisture and a vibrational test was performed as a test for evaluating the mechanical strength of the liquid crystal display panel. The PCT test is performed to evaluate failure occurring along with lapse of time (hours) under the circumstances at a temperature of 120° C., at 2 atmospheres, and at a humidity of 100%. The vibrational test is performed to evaluate film peeling occurring when vibrations are applied as impact shocks corresponding to the multiples of the gravitational force, to the liquid crystal display panel by a vibrational tester. InFIG. 7, pass or failure is judged at the measure of 20 hours in the PCT test and 1.5 G for mechanical strength. In the judgment, “o” represents pass and “x” represents failure.

For Comparative Example 1 inFIG. 7, while 2.5 G is ensured for the mechanical strength, the PCT durability is 10 hours and not sufficient. That is, it is considered that moisture intruded through a portion of the overcoat film203, the portion being deteriorated by the ultraviolet light radiation. In Comparative Example 2, while 50 hours are ensured for the PCT durability, the mechanical strength is 1.5 G which is at a boundary between pass and failure, which is judged to be insufficient. This is considered that the bonding strength between the alignment film113and the interlayer insulating film109on the side of TFT substrate is not sufficient in the seal portion.

Example 1 ensures 50 hours for the PCT durability, which is within a range of pass. It is considered that the overcoat film203is not deteriorated in the structure of Example 1. The mechanical strength is ensured as 2 G, which is within a range of pass. However, the mechanical strength is inferior to other examples. It is considered to be attributable to that the sealant150is in contact only with the alignment film113on the side of the counter substrate200.

Example 2 ensures the PCT durability of 50 hours and the mechanical strength of 2.5 G, each of which is within a range of pass.FIG. 3according to Example 2 shows that moisture from the outside is blocked sufficiently at the portion A where the overcoat film203, the alignment film113, and the sealant150overlap each other. Further, it shows that the bonding strength of the sealant150is ensured sufficiently since the sealant150and the overcoat film203are in direct contact with each other.

Also Example 3 ensures the PCT durability of 50 hours and the mechanical strength of 2.5 G, each of which is within a range of pass.FIG. 5according to Example 3 shows that the moisture from the outside is blocked sufficiently at the portion A where the overcoat film203, the alignment film113, and the sealant150overlap each other. The sealant150partially overlaps the alignment film113on the side of the TFT substrate100, which, however, scarcely gives undesired effect on the mechanical strength.

As described above, in the structure of any of Examples 1 to 3, the PCT durability, the mechanical strength, or the like are within a range of pass and the reliability of the liquid crystal display panel can be ensured.