JP2000267115A - Liquid crystal display device and sealing material for liquid crystal display device - Google Patents

Abstract

(57) [Problem] To provide a liquid crystal display element which has high reliability and realizes high-quality image display. SOLUTION: On a main surface, a first substrate having a scanning line and a signal line formed in a matrix, a switching element, and a pixel electrode connected to the switching element,
A second substrate disposed opposite to the first substrate, a liquid crystal interposed between the first and second substrates, a spacer for maintaining an interval between the first and second substrates, And a sealing material for bonding between the second substrate and a sealing material that is not provided with the sealing material and seals an injection port for injecting the liquid crystal. One of the members formed contains an organic substance having an impurity-adsorbing ability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display device and a sealing material for the liquid crystal display device, and more particularly to a liquid crystal display device having good display performance, high yield and high reliability.

[0002]

2. Description of the Related Art In a liquid crystal display device generally used at present, a liquid crystal is sandwiched between a pair of glass substrates having electrodes, and the periphery of the pair of substrates is fixed with a sealing material except for a liquid crystal filling port. It has a structure in which the liquid crystal sealing port is sealed with a sealing agent. In a liquid crystal display element for color display, a color filter including R, G, and B colored layers is formed on one of a pair of glass substrates.

For example, in a color dot matrix liquid crystal display element driven by a simple matrix, a Y substrate having Y electrodes patterned in a band shape in the horizontal (Y) direction is provided.
A configuration in which an X substrate having a colored layer below an X electrode patterned in a strip shape in the vertical (X) direction is opposed to the Y electrode so that the X electrode is almost perpendicular to the substrate, and a liquid crystal composition is sandwiched therebetween. Have.

As a display system of the liquid crystal display element, for example, a TN mode, an ST mode, a GH mode, an FCB mode, or a mode using a ferroelectric liquid crystal is used. As the sealant, for example, a heat- or ultraviolet-curable acrylic or epoxy adhesive is used.

In a color active matrix drive liquid crystal display device, for example, amorphous silicon (a
-Si) as a semiconductor layer
, A display electrode and a signal line electrode connected to the TFT array substrate, a TFT array substrate as an active matrix substrate on which a gate electrode is formed, and a counter substrate disposed opposite to the TFT array substrate. And a liquid crystal composition is sandwiched between the pair of substrates.

A color image is displayed by disposing polarizing plates on both sides of the pair of substrates and functioning as an optical shutter.

In addition to bonding a pair of substrates, the sealing material for a liquid crystal display element has a role of enclosing a liquid crystal composition and preventing invasion of moisture and the like from the outside. In addition, since the sealing material surrounds the periphery of the glass substrate,
It has interfaces with many substances such as electrodes, liquid crystals, alignment films, sealing materials, and the like.

[0008] For this reason, it is an important requirement for the sealing material to have good compatibility with each substance as well as strong adhesive strength and sealing property. In addition, in order to obtain a highly reliable liquid crystal display element, it is necessary not to contaminate the liquid crystal composition and the alignment film, and if the sealing material contains impurities, it may cause display defects, Or reduce reliability.

If the adhesive strength of the sealing material is weak, when a vacuum is applied between the glass substrates in the liquid crystal injection process after bonding a pair of glass substrates, peeling of the seal is likely to occur, and the yield is reduced. Further, since the sealing property of the liquid crystal display element is deteriorated, the reliability is reduced due to the invasion of moisture from the outside.

In the case of a sealing material that is incompatible with a sealing material for sealing the liquid crystal injection port, a gap is easily formed between the sealing material and the sealing material at the liquid crystal injection port, and moisture and impurities enter from the outside. Fear arises. In the case of a sealing material having poor compatibility with the liquid crystal, poor alignment may occur near the sealing material, which may cause light leakage.

On the other hand, a coloring material for a color filter used for a liquid crystal display element for color display is generally formed using a material obtained by adding an organic pigment to an organic polymer such as an acrylic resin or a polyimide resin. Examples of pigments include Pigment No. 7, 15: 6, 83, 138, 1
39, 177 and the like. Examples of the organic polymer include methacrylic acid / benzis methacrylate copolymer, pentaerythritol tetraacrylate, and 2-methyl [4- (methylthio) phenyl as an ultraviolet-curable acrylic resin. ] -2-morpholino-1-propanone diethylthiochitosan, 2- (o-chlorophenyl)
A mixture of -4,5-diphenylimidazolyl dimer, 3-methoxybutyl acetate, ethylene glycol monomethyl ether and the like are used.

Further, the color filter substrate is formed by processing and forming the above-mentioned coloring material into a predetermined shape on the substrate, forming an overcoat material as required, and forming a transparent electrode thereon. You.

Further, a color filter is formed directly on an active matrix substrate on which a switching element made of a-Si or poly-Si and the like are formed, in correspondence with each display pixel, and a color filter layer is formed on a counter substrate. A configuration of a liquid crystal display element not provided is also proposed.

In such a liquid crystal display device, a problem of reliability often occurs. According to the study of the present inventors, impurities such as acids and amines from a color filter material, or chemicals used when processing a color filter layer and an electrode, an alignment film or a liquid crystal layer, or a liquid crystal layer or a liquid crystal layer, It was found that these impurities eluted at the interface, and these impurities were partially collected on the alignment film with the operation of the liquid crystal display element, causing display unevenness and image sticking. in this way,
Conventional liquid crystal display elements for color display have low reliability.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a liquid crystal display element which has high reliability and realizes high quality image display.

Another object of the present invention is to provide a sealing material for a liquid crystal display element which can provide a liquid crystal display element which has high reliability and realizes high-quality image display.

[0017]

In order to solve the above-mentioned problems, the present invention is directed to a method in which a scanning line and a signal line formed in a matrix on one main surface, a switching element, and the switching element are connected. A first substrate having a pixel electrode,
A second substrate disposed opposite to the first substrate, a liquid crystal interposed between the first and second substrates, a spacer for maintaining an interval between the first and second substrates, And a sealing material for bonding between the second substrate and a sealing material that is not provided with the sealing material and seals an injection port for injecting the liquid crystal. Provided is a liquid crystal display element, wherein any one of the members formed contains an organic substance having an impurity adsorption ability.

In such a liquid crystal display element, the spacer is a columnar spacer, and examples of the non-pixel portion member containing an organic substance having an impurity-adsorbing ability include a columnar spacer, a sealing agent, and a sealing material. In addition, as the organic substance having the ability to adsorb impurities, polyimide can be given.

The present invention also provides a liquid crystal display device as described above,
A sealing material for a liquid crystal display element, which is a sealing material for bonding between the first and second substrates, wherein the sealing material contains polyimide. In this case, an acid anhydride and a diamine may be contained instead of or together with the polyimide.

In the above-mentioned liquid crystal display device and the sealing material for a liquid crystal display device of the present invention, the polyimide is obtained by reacting an acid anhydride with a diamine, particularly 2,3,5-.
Those obtained by reacting tricarboxycyclopentylic acid dianhydride with a diamine are preferred.

In the case where a sealing material to which an acid anhydride and a diamine are added in place of the polyimide is used, it is considered that the acid anhydride and the diamine react to form polyimide when cured by heating. Can be

In general, a sealing material for a liquid crystal display element includes a base material, a curing agent, a filler, a curing accelerator, a solvent,
It contains a viscosity modifier and the like. The amount of the filler has a great influence on the adhesive strength. Generally, silica powder or alumina powder is often used as the filler.

According to an experiment by the present inventors, when polyimide powder was added to a sealing material for a liquid crystal display element, the amount of the addition increased the adhesive strength. This means that polyimide, which is stable as a substance, functions as a filler in the sealing material, like silica powder and alumina powder.

In another experiment of the present inventors, when a liquid crystal display element was manufactured using a sealing material to which these polyimides were added, a liquid crystal display element was compared with a device using a sealing material to which no polyimide was added. It was also found that the disorder of the orientation near the sealing material was reduced. This is because a part of the polyimide added to the sealing material was present on the surface, and the wettability of the sealing material surface to the liquid crystal material was improved.

According to still another experiment, it was found that when polyimide was added to the sealing material, the reliability of the liquid crystal display element was also improved. Many of the reliability problems in liquid crystal display elements are caused by acids (such as oxalic acid, benzoic acid, phthalic acid, or aliphatic acid) and amines (aniline, N, etc.) eluted from color filter materials, sealing materials and sealing materials.
Impurities such as methylaniline and aliphatic aniline) or chemicals (TMAH and surfactants added thereto) used for processing the color filter layer and the electrode. . These are
It elutes in the alignment film or the liquid crystal layer, or at the interface between them, and with the operation of the liquid crystal display element, these impurities partially collect on the alignment film or at the corners of the liquid crystal display element, causing display unevenness and image sticking. is there.

On the other hand, polyimide, which is generally used as an alignment film, especially polyimide comprising 2,3,5-tricarboxycyclopentylic acid dianhydride and diamine, has a strong polarity and a large polarity term of surface energy. It is known, and it can be explained that the helical structure has a high impurity capturing performance. Therefore, by adding these polyimides to the sealing material, impurities such as the above-described acids and amines can be easily captured, and the reliability can be improved.

On the other hand, a polyimide using an aromatic acid anhydride or a tetraphosphoric acid anhydride has a weak polarity, has a planar structure in structure, and as a result, has a somewhat low impurity trapping performance. In addition, polymers other than polyimide are thermally and chemically unstable, and when mixed into a color filter material, reliability is newly generated due to decomposition of the polymer itself, which is a problem. Further, if the molecular weight is too small, the substance itself elutes and poses a problem. Therefore, it is important to add a polyimide having a relatively large molecular weight.

It has been found that such effects can be exerted not only by the sealing material but also by adding polyimide to other members of the non-pixel portion, for example, a columnar spacer or a sealing material.

That is, impurities eluted from a color filter material, a sealing material and a sealing material, and chemicals used for processing a color filter layer and an electrode are eluted into an alignment film, a liquid crystal layer, or an interface between them. According to experiments performed by the inventors of the present invention, a phenomenon that causes display unevenness and image sticking is caused by including a predetermined organic substance such as polyimide in a non-pixel portion such as a sealing material, a sealing material, and a columnar spacer. It turns out that it can be resolved.

These impurities are adsorbed and captured by an organic substance having an ability to adsorb impurities contained in a non-pixel portion such as a sealing material, a sealing material, and a columnar spacer. Therefore, it has been found that impurities do not elute into the alignment film layer and the liquid crystal layer in the pixel portion or the interface between them, and as a result, reliability problems are suppressed.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically by showing embodiments as embodiments of the present invention.

Example 1 FIG. 1 is a sectional view showing an active matrix liquid crystal device according to one embodiment of the present invention. By repeating film formation and patterning on a glass substrate in the same manner as in the process for forming a normal TFT, an amorphous silicon TFT array substrate 11 having a total of 10,000 pixels in length and width in which thin film transistors and electrode wirings were formed was formed. . On the TFT array substrate 11, an alignment film material is applied over the entire surface, rubbed, and subjected to an alignment film 15a.
Are formed.

Next, as described below, a counter substrate 19 was formed by forming a coloring layer, an ITO film, and an alignment film on a glass substrate. That is, on a glass substrate,
A UV-effect acrylic resin resist in which a black pigment is dispersed is applied to the entire surface by a spinner, and a light mask is applied through a photomask such that light is applied to a portion where a mark or the like necessary at the time of assembling a cell is required. Irradiate 100 mJ / cm ² at a wavelength of 365 nm, and add 1% aqueous KOH
Development was carried out for 0 second to form a black colored layer on the portion.

Next, a UV-curable acrylic resin resist in which a red pigment is dispersed is applied over the entire surface by a spinner, and a photo layer is applied so that light is also applied to the colored layer on the light-shielding layer in the vicinity of the portion to be colored red. 365n through the mask
Irradiation at a wavelength of m was performed at 100 mJ / cm ² and development was performed with a 1% aqueous solution of KOH for 10 seconds to form a red colored layer 17 </ ^b > R on that portion.

Similarly, a green coloring layer 17G and a blue coloring layer 17B were formed and baked at 230 ° C. for 1 hour.
On these colored layers, an ITO film having a thickness of 1500 ° is formed as a transparent electrode 18 by a sputtering method, and then an alignment film material similar to the above is formed thereon. Was formed.

Next, using a sealing material in which polyimide powder was dispersed, a sealing material 16 was printed along the periphery of the alignment film 15b of the substrate 19 except for an injection port (not shown). Here, the polyimide dispersed in the sealing material is 2, 3,
It is a powder of polyimide obtained by polymerizing 5-tricarboxycyclopentylic acid dianhydride and diamine.
The total amount of the polyimide was set to 1 wt% as the content in the sealing material.

Thereafter, the spacer 20 is provided on the surface of the substrate 19.
And micropearl having a particle size of 6 μm was sprayed. Next, the substrates 11 and 19 are arranged so that the alignment films 15a and 15b face each other and the rubbing directions thereof are 90 degrees, and the sealing material is cured by heating. Were pasted together.

Next, a liquid crystal composition 21 to which 0.1% by weight of a chiral agent was added was injected into the liquid crystal composition 21 from an injection port, and the injection port was sealed with an ultraviolet curing resin.

The color display type active matrix liquid crystal display element thus formed has no light leakage from the peripheral portion where the sealing material is formed, no display failure,
High-quality display was obtained. Further, when a reliability test was performed in an atmosphere of 70 ° C., no display failure occurred even after 1000 hours.

Example 2 Instead of adding polyimide powder to the sealing material 16,
A color display type active matrix liquid crystal display device was formed in the same manner as in Example 1, except that 3,5-tricarboxycyclopentylic acid dianhydride and diamine were added.

In this color display type active matrix liquid crystal display element, there was no light leakage from the peripheral portion where the sealing material 16 was formed, no display failure, and a high quality display was obtained. Further, when a reliability test was performed in an atmosphere of 70 ° C., no display failure occurred even after 1000 hours.

Comparative Example 1 A color display type active matrix liquid crystal display element was formed in the same manner as in Example 1 except that no polyimide powder was added to the sealing material.

When a reliability test was performed on this color display type active matrix liquid crystal display device in an atmosphere of 70 ° C., white spot defects occurred near the sealing material after 100 hours.

Example 3 FIG. 2 is a sectional view showing an active matrix liquid crystal display device according to another embodiment of the present invention. By repeating film formation and patterning in the same manner as a general process for forming an active matrix liquid crystal display element, T
An FT element was formed, and a liquid crystal display element as shown in FIG. 2 was manufactured using a general process.

First, a molybdenum film having a thickness of about 0.3 μm is formed on the transparent substrate 31 by sputtering, and is patterned into a predetermined shape by photolithography.
A gate line 32 was formed. Then, a film thickness of 0.1
A gate insulating film line 33 of 5 μm silicon dioxide or silicon nitride was formed, and a TFT semiconductor layer 34 was further provided thereon.

Then, a 0.3 μm-thick ITO film was formed thereon.
Forming a signal line 35 and a source electrode 36 made of
Was formed. Then, by patterning the photosensitive resin containing the colorant by photolithography, red, blue,
A colored layer 37 made of green was formed. That is, a photomask in which a photosensitive resist in which a red pigment is dispersed is applied over the entire surface using a spinner, dried at 90 ° C. for 10 minutes, and then only a portion where a red colored layer is formed is irradiated with ultraviolet rays. Exposure was performed so that the exposure amount became 200 mJ / cm ² through.

Next, a 2 wt.
Developing was performed for 0 second, and baking was performed at 200 ° C. for 60 minutes to form a red colored layer. Similarly, by repeatedly forming green and blue colored layers, the thickness of each colored layer becomes 1.5 (μ).
m) was obtained.

Further, an ITO film having a thickness of 0.1 μm is formed and patterned to form a pixel electrode 38.
Was formed to obtain an array substrate. The source electrode 30
Is connected to the pixel electrode 23 in contact with the coloring layer 37 via a through hole 39 in the coloring layer 37.

Thereafter, a negative-type acrylic resist in which 1% by weight of a polyimide obtained by polymerizing 2,3,5-tricarboxycyclopentylic acid dianhydride and para-phenylenediamine is mixed and dispersed is applied using a spinner, and then coated with a spinner.
After drying at 10 ° C. for 10 minutes, ultraviolet rays were irradiated through a photomask at an exposure amount of 300 mJ / cm ² , and pH = 11.0.
By developing with an alkaline aqueous solution of No. 5 and baking at 200 ° C. for 60 minutes, the spacer 40 was formed in the non-pixel portion.

The counter substrate was manufactured by forming an ITO film 42 on a glass substrate 41 by a usual method. A liquid crystal display device as shown in FIG. 1 was manufactured using the array substrate and the counter substrate manufactured as described above. This liquid crystal display device was manufactured as follows. That is, the liquid crystal alignment film 43 is formed on the array substrate and the counter substrate.
Polyimide was applied and formed as a and 43b, and rubbing treatment was performed by a usual method. Then, an epoxy-based adhesive was applied to the peripheral portions of these substrates, and these substrates were oriented such that the alignment film surfaces faced each other. The assembly was heated and cured. Thereafter, a nematic liquid crystal material to which a chiral agent was added at 0.1 wt% was vacuum injected, and the injection port was sealed with an ultraviolet curable resin.

The liquid crystal display device thus formed can perform uniform display without unevenness or image sticking even after operation for 1000 hours at 70 ° C. and 80% humidity, and has high reliability. It was found to have

In this embodiment, the spacer 40
The alignment film 43a is formed so as to cover the spacer 40. In practice, however, the alignment film 43a may be formed thin on or near the slope of the spacer 40, or the alignment film 43a may not be provided and the surface of the spacer 40 may be exposed. Many. The present embodiment is particularly effective in such a case.

Comparative Example 2 As a negative type acrylic resist serving as a spacer,
An array substrate was prepared in the same manner as in Example 3, except that a polyimide obtained by polymerizing 3,5-tricarboxycyclopentylic acid dianhydride and para-phenylenediamine was not added. Was prepared. This liquid crystal element was subjected to an operation test at 70 ° C. and 80% humidity. As a result, in 72 hours, display unevenness accompanied by burn-in occurred at the periphery of the screen.

Comparative Example 3 Negative-type acrylic resists serving as spacers
4-dicarboxy-1,2,3,4, tetrahydro-1
-A color filter substrate was prepared in the same manner as in Example 3, except that a polyimide obtained by polymerizing naphthalene succinic anhydride and diphenyldiaminomethane was added in an amount of 1 wt%, and a liquid crystal display was formed in the same manner. An element was manufactured. This liquid crystal element was subjected to an operation test at 70 ° C. and 80% humidity. As a result, in 158 hours, display unevenness accompanied by image sticking occurred around the screen.

Comparative Example 4 The procedure of Example 3 was repeated, except that 1 wt% of a polyimide obtained by polymerizing pyromellitic anhydride and diphenyldiaminomethane was used as a negative-type acrylic resist serving as a spacer. Then, a color filter substrate was manufactured, and a liquid crystal display element was manufactured in the same manner. The liquid crystal element was subjected to an operation test at 70 ° C. and 80% humidity. As a result, display unevenness accompanied by image sticking occurred at the periphery of the screen in 200 hours.

Example 4 An epoxy-based adhesive for bonding a substrate using an array substrate without a spacer made of a negative type acrylic resist, a color filter substrate, and a spacer sphere made of a styrene resin having a diameter of about 5 μm. As 2,3,5-
After applying a polyimide to which tricarboxycyclopentylic acid dianhydride and para-phenylenediamine had been added to the periphery of the substrate, in the same manner as in Example 3,
A liquid crystal display device was manufactured.

The liquid crystal display device thus formed is:
It was found that even after operation for 1000 hours in a humidity of 70 ° C. and 80%, uniform display without unevenness or image sticking was possible and high reliability was obtained.

Example 5 An array substrate having no spacer made of a negative type acrylic resist, a color filter substrate, and a spacer sphere made of a styrene resin having a diameter of about 5 μm were used, and 2,3,5- The injection port after liquid crystal injection was sealed with an ultraviolet curable resin to which polyimide obtained by polymerizing tricarboxycyclopentylic acid dianhydride and para-phenylenediamine was added, to produce a liquid crystal display device. It can be seen that the liquid crystal display element thus formed can perform uniform display without unevenness or image sticking and has high reliability even after operation for 1000 hours at 70 ° C. and 80% humidity. Was.

Modifications (1) In Embodiment 3 described above, the spacers 3 were formed using a negative type acrylic resist. However, red, blue and green colored layers of a color filter may be used. Even if it is used, it may be formed in the non-pixel portion.

(2) In the above embodiment, the spacers 3 are arranged on the array substrate. However, they may be arranged on the opposite substrate, and the color filters may be arranged on the opposite substrate.

(3) In the above-described embodiment, the active matrix type liquid crystal display element has been described. However, the present invention can be similarly applied to a simple matrix type liquid crystal display element.

[0062]

As described above in detail, according to the present invention, since any member of the non-pixel portion contains an organic substance having an impurity-adsorbing ability, impurities or impurities in a liquid crystal display device can be obtained. The problem of reliability such as display unevenness and image sticking caused by chemicals can be solved, and a highly reliable liquid crystal display device can be provided at low cost.

It is another object of the present invention to provide a sealing material for a liquid crystal display device which has a high adhesive strength, is compatible with a liquid crystal or the like, and is capable of providing a highly reliable liquid crystal display element at a low cost with a good yield. Became possible.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a liquid crystal display device according to one embodiment of the present invention.

FIG. 2 is a sectional view showing a liquid crystal display device according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Array board | substrate 15a, 15b, 43a, 43b ... Alignment film layer 16 ... Sealing material 17R, 17G, 17B, 37 ... Colored layer 18, 38, 42 ... ITO layer 19 ... Counter substrate 20, 40 ... Spacer 21 ... Liquid crystal 31 41, a transparent substrate 32, a gate line 33, a 3 gate insulating film 34, a semiconductor layer 35, a signal line 36, a source electrode.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Jin Hato 1-9-2 Hara-cho, Fukaya-shi, Saitama F-term in Fukaya Electronics Factory, Toshiba Corporation (reference) 2H089 LA09 MA04X MA04Y MA04Z PA09 PA19 QA08

Claims (8)

[Claims] A first substrate having a scanning line and a signal line formed in a matrix on one main surface, a switching element, and a pixel electrode connected to the switching element; A second substrate disposed to face, a liquid crystal interposed between the first and second substrates, a spacer for maintaining an interval between the first and second substrates, In a liquid crystal display element provided with a sealing material for bonding between them, and a sealing material which is not provided with the sealing material and seals an injection port for injecting the liquid crystal, A liquid crystal display device, wherein the member contains an organic substance having an impurity adsorption ability. 2. The spacer according to claim 1, wherein the spacer is a columnar spacer, and any one of the columnar spacer, the sealing agent, and the sealing material contains an organic substance having an impurity adsorption ability. Liquid crystal display element. 3. The liquid crystal display device according to claim 1, wherein the organic substance having the ability to adsorb impurities is polyimide. 4. The liquid crystal display device according to claim 3, wherein the organic substance having an impurity-adsorbing ability is a polyimide obtained by reacting an acid anhydride with a diamine. 5. The organic substance having an impurity-adsorbing ability,
The liquid crystal display device according to claim 4, wherein the liquid crystal display device is a polyimide obtained by reacting 2,3,5-tricarboxycyclopentylic acid dianhydride with a diamine. 6. A first device having at least a scanning line and a signal line formed in a matrix on one main surface, a switching element, and a pixel electrode connected to the switching element.
A second substrate disposed opposite to the first substrate, a liquid crystal interposed between the first and second substrates, and a spacer for maintaining a distance between the first and second substrates A sealing material for bonding between the first and second substrates of a liquid crystal display device, comprising: polyimide, an acid anhydride, and a diamine. 7. The polyimide according to claim 6, wherein the polyimide is obtained by reacting an acid anhydride with a diamine.
3. A sealing material for a liquid crystal display element according to item 1. 8. The seal for a liquid crystal display device according to claim 7, wherein the polyimide is obtained by reacting 2,3,5-tricarboxycyclopentylic acid dianhydride with a diamine. Wood.