JP3468576B2 - Liquid crystal display cell and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a liquid crystal display cell and a method for manufacturing the same.

[0002]

BACKGROUND OF THE INVENTION Conventionally, I has been formed on the surface of a glass substrate.
A transparent electrode made of a film such as TO (Indium Tin Oxide),
A pair of substrates with transparent electrodes, in which alignment films made of a polymer such as polyimide are sequentially laminated, are arranged via spacers so that the respective transparent electrode films face each other, and the spacers are provided at predetermined intervals. A liquid crystal display cell in which a liquid crystal is sealed in a gap is known.

In this type of liquid crystal display cell, the alignment film may be damaged by foreign matter or spacers mixed in the liquid crystal, and as a result, the upper and lower electrodes may be electrically connected to each other to cause a display defect.

Further, in the process of preparing the alignment film, static electricity is generated during the rubbing treatment on the surface of the coating film made of a polymer such as polyimide, and this static electricity is instantaneously discharged in large quantities through the transparent electrode. The alignment film sometimes generated heat and was destroyed.

Therefore, conventionally, it has been proposed to form an insulating protective film (insulating film) between the transparent electrode and the alignment film on the substrate with a transparent electrode of the above liquid crystal display cell. (JP-A-60-260021, JP-A-1-
150116, JP-A-2-221923, etc.).

However, when such an insulating film is formed between the transparent electrode and the alignment film, the static electricity charged in the alignment film cannot be removed during rubbing, and the static electricity remains in the alignment film. Therefore, a liquid crystal display cell including a substrate with a transparent electrode in which a transparent electrode, an insulating film, and an alignment film are sequentially laminated on the substrate has a problem that a display defect occurs.

Further, when forming a conventional transparent electrode protective film, a film curing temperature of 300 to 500 ° C. is required. Therefore, when forming this protective film, the transparent electrode is heated to a high temperature, and as a result, the resistance value of the transparent electrode made of a film such as ITO increases, and power consumption increases. there were. Recently, the definition of large-sized super twisted nematic (STN) type liquid crystal panels has been improved, and ITO films having a resistance value of several Ω have been used for transparent electrodes. Will increase and lead to higher power consumption.

Therefore, there has been desired a liquid crystal display cell and a method of manufacturing the same which prevent a display defect due to damage of an alignment film due to a spacer or the like and an increase in resistance value of a transparent electrode.

[0009]

SUMMARY OF THE INVENTION The present invention is intended to solve the problems associated with the prior art as described above, and replaces the conventional protective film requiring a high curing temperature with inorganic compound fine particles. An object of the present invention is to provide a liquid crystal display cell having an alignment film that also functions as a protective film by forming an alignment film containing the same on the surface of a transparent electrode, and a method for manufacturing the same.

[0010]

SUMMARY OF THE INVENTION A liquid crystal display cell according to the present invention is a liquid crystal display cell having a substrate with a transparent electrode in which a transparent electrode and an alignment film are sequentially laminated on the substrate, wherein the alignment film contains fine particles of an inorganic compound, And the inorganic compound fine particles have a concentration gradient in the thickness direction of the alignment film, the concentration of the inorganic compound fine particles is increased toward the transparent electrode side, and a part of the alignment film forming resin is directly bonded to the transparent electrode. It is characterized by being.

Further, according to the method of manufacturing a liquid crystal display cell of the present invention, when a liquid crystal display cell having a transparent electrode substrate in which a transparent electrode and an alignment film are sequentially laminated on the substrate is manufactured, the liquid crystal display cell is formed on the substrate. On the surface of the transparent electrode, the dispersion liquid in which the inorganic compound fine particles are dispersed in the dispersion medium is applied, and then the dispersion medium is removed to form a layer composed of the inorganic compound fine particles, and then on the inorganic compound fine particle layer. To form an alignment film containing fine particles of an inorganic compound on the surface of the transparent electrode by applying a coating liquid containing a resin for forming an alignment film so that a part of the resin for forming an alignment film is directly bonded to the transparent electrode. Is characterized by.

In the present invention, the inorganic compound fine particle layer is preferably formed by applying a coating liquid for forming an inorganic compound fine particle layer in which inorganic compound fine particles are dispersed on the surface of a transparent electrode formed on a substrate. .

According to the present invention, it is possible to obtain a liquid crystal display cell of low power consumption which prevents a display failure due to damage of an alignment film due to a spacer or the like and an increase in resistance value of a transparent electrode.

[0014]

DETAILED DESCRIPTION OF THE INVENTION The liquid crystal display cell and the method for producing the same according to the present invention will be specifically described below.

First, the liquid crystal display cell according to the present invention will be specifically described with reference to the drawings. FIG. 1 is a sectional view schematically showing an example of a liquid crystal display cell according to the present invention. The liquid crystal display cell 1 includes a transparent electrode 22 made of a thin film of ITO or the like on a transparent substrate 21 such as glass or plastic.
And a pair of transparent electrode-attached substrates 2 and 2 in which an alignment film 24 made of a polymer such as polyimide containing inorganic compound fine particles 23 is sequentially laminated. The pair of transparent electrode-attached substrates 2 and 2 are arranged by a plurality of spacer particles 3 with a predetermined gap d so that the transparent electrodes 22 and 22 face each other. Further, in the gap d, the liquid crystal 4
Is enclosed.

Specific examples of the inorganic compound fine particles 23 include SiO ₂ , Al ₂ O ₃ , TiO ₂ , ZrO ₂ and S.
One of inorganic oxide fine particles such as b ₂ O ₅ , SnO ₂ and In ₂ O ₃ or composite oxide fine particles thereof, or conductivity of Sb-doped SnO ₂ and Sn-doped In ₂ O ₃ Oxide particles may be mentioned. Examples of the composite oxide fine particles include SiO ₂ —Al ₂ O ₃ and TiO ₂ —CeO.
Examples include fine particles such as ₂ .

Depending on the type of the inorganic compound fine particles 23, various functions can be given to the alignment film in addition to the function as a hard coat film (protective film for the transparent electrode). For example, when conductive particles such as Sb ₂ O ₅ and Sb-doped SnO ₂ are used, the resulting alignment film 24 also has a function as an antistatic coating. Further, when the inorganic compound particles 23 having a high refractive index such as TiO ₂ and ZrO ₂ are used, the transparent electrode 2
The alignment film 24 having a refractive index distribution can be formed from the 2 side toward the layer of the liquid crystal 4. The refractive index of these fine particle-containing alignment film portions becomes as high as the refractive index of ITO, making it difficult to see the ITO transparent electrode from the outside of the liquid crystal display cell.

The average particle size of the inorganic compound fine particles 23 depends on the thickness of the alignment film 24, but is preferably in the range of 5 to 100 nm. Further, it is preferable that the inorganic compound fine particles 23 have a spherical shape or a shape close to a spherical shape.

The thickness of the alignment film 24 used in the present invention is
The range of about 60 to 180 nm is preferable, and it is desirable that most of the portion of about 10 to 80 nm from the layer surface of the liquid crystal 4 is made of the alignment film forming resin.

In the alignment film 24 used in the present invention, most of the inorganic compound fine particles 23 are present on the transparent electrode 22 side, and most of the alignment film 24 near the layer of the liquid crystal 4 is an alignment film forming resin. For example, it is composed only of a polymer such as polyimide. Therefore, the alignment film 2 near the layer of the liquid crystal 4
The 4th portion has the same alignment ability as the conventional liquid crystal display cell, and the alignment film 24 portion on the transparent electrode 22 side has a film strength higher than that of the alignment film formed only of the alignment film forming resin. It is getting bigger. Therefore, even if the alignment film 24 near the layer of the liquid crystal 4 is damaged, the transparent electrode 22 side of the alignment film 24 is not damaged, and the alignment film 24 has a function as a transparent electrode protective film. There is.

In the liquid crystal display cell according to the present invention, an alkali passivation film such as a SiO ₂ film may be further formed between the transparent substrate 21 and the transparent electrode 22. Next, a method for manufacturing a liquid crystal display cell having an alignment film containing the above-described inorganic compound fine particles will be specifically described with reference to the drawings.

FIG. 2 is a drawing for explaining an example of a process of forming an alignment film containing fine particles of an inorganic compound according to the present invention, and FIG. 2 (1) shows a transparent substrate having a transparent electrode on the surface. 2 is a cross-sectional view schematically showing an example of FIG.
(2) is a schematic cross-sectional view showing a state in which a coating liquid for forming a fine particle layer in which inorganic compound fine particles are dispersed is applied to the surface of a transparent electrode provided on a transparent substrate, and (3) in FIG. FIG. 4 is a schematic cross-sectional view showing a state after the dispersion liquid is removed by drying the coating liquid for forming an inorganic compound fine particle layer applied on the surface of the transparent electrode, and (4) in FIG. FIG. 3 is a schematic cross-sectional view showing a substrate with a transparent electrode, in which an alignment film containing fine particles of an inorganic compound is provided.

First, as shown in FIG. 2A, a transparent electrode 22 made of a film such as ITO is formed on a transparent substrate 21 such as a glass substrate by a conventionally known method. Then
As shown in (3) of FIG. 2, a layer made of inorganic compound fine particles 23 is formed on the surface of the transparent electrode 22 formed on the transparent substrate 21.

The layer composed of the inorganic compound fine particles 23 is
For example, it can be formed as follows. As shown in (2) of FIG. 2, after applying the coating liquid 26 in which the fine particles of the inorganic compound are dispersed onto the surface of the transparent electrode 22 formed on the transparent substrate 21, the dispersion liquid is heated to 50 to 200 ° C. and dispersed. The medium is removed by evaporation, and a layer of the inorganic compound fine particles 23 as shown in (3) of FIG. 2 is formed on the transparent electrode 22.

As the coating liquid 26 for forming the inorganic compound fine particle layer, a dispersion liquid in which the powder of the above-mentioned inorganic compound fine particles 23 is dispersed in water and / or organic solvent 25, or an inorganic compound in water and / or organic solvent 25 is used. Compound fine particles 23
A dispersion obtained by diluting a sol dispersed as colloidal particles with an appropriate solvent is used.

The concentration of the inorganic compound fine particles 23 in the coating liquid 26 is not particularly limited as long as it does not hinder the coating of the coating liquid 26. Specific examples of the organic solvent 25 used in the coating liquid 26 include alcohols such as methanol, ethanol and isopropanol; glycols such as ethylene glycol, propylene glycol, hexylene glycol and octylene glycol; methyl cellosolve and ethyl. Cellosolves such as cellosolve and butyl cellosolve; pyrrolidones such as N-methylpyrrolidone; carbitols such as methylcarbitol and ethylcarbitol; ketones such as acetone, methylethylketone and acetylacetone.

In order to improve the dispersibility of the inorganic compound fine particles 23 in the dispersion medium, the inorganic compound fine particles 23 immediately after the coating liquid 26 is applied onto the transparent electrode 22 and heated to remove the dispersion medium. It is preferable to add a small amount of a stabilizer to the coating liquid 26 in order to maintain a certain binding force in the layer.

The amount of the stabilizer added is preferably 20 parts by weight or less with respect to 100 parts by weight of the inorganic compound fine particles in the inorganic compound fine particle layer after curing. When the amount of the stabilizer exceeds 20 parts by weight, the permeation of the alignment film forming resin into the inorganic compound fine particle layer becomes insufficient during the formation of the alignment film. Further, the curing of the stabilizer is insufficient, so that the alignment film becomes white.

Specific examples of such a stabilizer include:
Tetraalkoxysilane, monoalkyltrialkoxysilane, dialkyldialkoxysilane or derivatives thereof (including partial hydrolysates); acetylacetone metal complex such as Zr, Ti, Al; silane coupling agent,
Titanium coupling agent, zirconium coupling agent,
Surfactants such as dodecylbenzene sulfonic acid may be mentioned.

Coating liquid 26 for forming the inorganic compound fine particle layer
Examples of the coating method include a spinner method and a flexographic printing method. The layer of the inorganic compound fine particles 23 has a thickness of about 50 to 100 nm.

Next, a coating liquid containing an alignment film forming resin 27 such as a polyimide resin is applied onto the layer of the inorganic compound fine particles 23 formed as described above by, for example, flexographic printing.

When the coating liquid containing the alignment film forming resin 27 is applied on the layer of the inorganic compound fine particles 23, the alignment film forming resin 27 fills the gaps between the layers of the inorganic compound fine particles 23.
Some of the alignment film forming resin 27 is directly bonded to the transparent electrode 22 or the transparent substrate 21.

The coating liquid containing the alignment film forming resin 27 has a thickness of about 10 to 80 on the layer of the inorganic compound fine particles 23.
The film thickness is adjusted so as to form a layer composed only of the resin 27 for forming the alignment film having a thickness of nm.

Next, the coating liquid containing the alignment film forming resin 27 is applied as described above and dried, and then 1
An alignment film 24 containing the inorganic compound fine particles 23 as shown in (4) of FIG. 2 is formed through a step of heating at 70 to 250 ° C.

The alignment film is usually obtained by subjecting the coating film surface of the alignment film forming resin 27 obtained by the above-mentioned heat curing to a predetermined rubbing treatment. In the alignment film 24 prepared as described above, the inorganic compound fine particles 23 are denser as they approach the transparent electrode 22. That is, the alignment film 24
The inorganic compound fine particles 23 therein have a concentration gradient in the thickness direction of the alignment film 24, and the concentration is higher toward the transparent electrode 22 side.

A pair of substrates as shown in (4) of FIG. 2 in which the alignment film 24 containing the inorganic compound fine particles 23 is formed on the transparent electrode 22 formed on the transparent substrate 21 will be described below. A liquid crystal display cell as shown in FIG. 1, for example, can be prepared by using a conventionally known method.

[0037]

The liquid crystal display cell according to the present invention comprises a substrate with a transparent electrode in which a transparent electrode and an alignment film are sequentially laminated on the substrate, and the alignment film contains fine particles of an inorganic compound, The inorganic compound fine particles in the film have a concentration gradient in the thickness direction of the alignment film, and since the concentration of the inorganic compound fine particles is higher on the transparent electrode side, it has a function as a conventional alignment film and at the same time as a hard coat film. It also has a protective film function.

Therefore, even if the alignment film is damaged by the spacers or the like, the damage does not extend to the inside of the film, and the conventional display defect does not occur. Further, according to the method for manufacturing a liquid crystal display cell of the present invention, since the step of forming the protective film for the transparent electrode is not required, the manufacturing process for the liquid crystal display cell can be simplified, and the conventional transparent electrode protective film can be formed. Since the high temperature heat treatment of 300 to 500 ° C. necessary for the formation is not performed, it is possible to prevent the resistance value of the transparent electrode made of a thin film such as ITO from increasing and to suppress the increase in power consumption.

Since the liquid crystal display cell according to the present invention is not subjected to the above high temperature heat treatment in the manufacturing process, it is a liquid crystal display cell with a color filter having a color filter having a heat resistant temperature of about 150 to 200 ° C. Can be used.

The present invention will be described below with reference to examples.
The present invention is not limited to these examples.

[0041]

Examples 1 to 7 and Comparative Examples 1 and 2 [Preparation of Stabilizers (M-1 to M-3)] (1) 100 g of ethyl silicate 28 (SiO ₂ concentration 28% by weight) and 421 g of hexylene glycol. HNO ₃ aqueous solution (61% HNO ₃ 5 g diluted with pure 34 g) was gradually added to the mixed solution, and the mixture was stirred for 1 hour to obtain Si.
A stabilizer having an O ₂ concentration of 5% by weight (hereinafter referred to as M-1) was prepared. (2) 100 g of butanol solution of dibutoxybis acetylacetonato zirconium (ZrO ₂ concentration 10% by weight)
0.1 g of acetic anhydride was added to a mixed solution of 99.1 g of N-methylpyrrolidone and stirred for 1 hour to prepare a stabilizer having a ZrO ₂ concentration of 5% by weight (hereinafter referred to as M-2). . (3) 0.1 g of acetic anhydride was added to a mixed solution of 100 g of titanium tetraisopropoxide in isopropanol (TiO ₂ concentration: 10% by weight) and 99.1 g of isopropanol.
Was added and stirred for 1 hour to prepare a stabilizer (hereinafter referred to as M-3) having a TiO ₂ concentration of 5% by weight.

[Preparation of Coating Liquid for Forming Fine Particle Layer of Inorganic Compound] The inorganic oxide sol shown in Table 1 or a mixed liquid of the inorganic oxide sol and the stabilizer was diluted with an organic solvent to give a liquid as shown in Table 2. Inorganic compound fine particle layer forming coating solution (C-1 to C
-9) was prepared.

[Formation of Alignment Film] On the electrode surface of a transparent electrode-equipped substrate [Asahi Glass Co., Ltd., 30 Ω type] in which electrodes made of ITO are formed in a pattern on a glass substrate, the coating solution shown in Table 2 is flexographically applied. After applying by a printing method and drying at 90 ° C. for 5 minutes, the inorganic compound fine particle layer was formed by heating at 180 ° C. for 30 minutes except for Example 7.

In the case of Example 7, the spinner method (2,000 rpm, 10 seconds) was applied and 90 ° C.
Only drying for 5 minutes was performed. Then, on the inorganic compound fine particle layer obtained as described above, a coating liquid for forming an alignment film [manufactured by Nissan Chemical Industries, Ltd., San Ever SE-411]
0] was applied by a flexographic printing method, dried at 90 ° C. for 5 minutes, and then baked at 200 ° C. for 30 minutes to form an alignment film on the electrode surface. [Evaluation of Alignment Film] The alignment film formed as described above was evaluated as follows. The results are shown in Table 3. (1) Film Thickness The thickness of the inorganic compound fine particle layer was measured by cutting the substrate after forming only the fine particle layer and by taking an electron micrograph of the cut surface.

The total thickness of the alignment film including the inorganic compound fine particle layer was measured by a contact type film thickness meter (manufactured by Taylor Hobson Co.). (2) Presence or absence of concentration gradient of fine particles of inorganic compound in the alignment film The substrate after the alignment film is formed is cut, and the cut surface is observed by an electron microscope to check the presence or absence of fine particles on the top of the alignment film (shading of the electron micrograph). evaluated. (3) Pencil hardness A pencil having a predetermined hardness was used to draw a line on the orientation film with a load of 1 kg, and then the presence or absence of scratches on the film was observed, and the hardness of the scratched pencil was evaluated. (4) Scratch resistance Bencotton was slid on the surface of the film 50 times with a load of 500 g, and it was observed whether the scratches reached the electrode surface of the substrate. (5) Appearance The presence or absence of turbidity and whitening of the alignment film was observed. (6) The charge decay time was measured with a Honest meter [produced by Kasuga Electric Co., Ltd.] to evaluate the antistatic performance.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

[Table 3]

From Table 3, the following can be understood. (1) The pencil hardness of each of the alignment films of Examples 1 to 7 is 2
It is H or higher, has excellent scratch resistance, and has a function as a hard coat film. (2) Alignment film of Example 4 using the coating liquid (C-4) for forming an inorganic compound fine particle layer made of conductive Sb ₂ O ₅ and formation of an inorganic compound fine particle layer made of conductive antimony-containing SnO ₂ The alignment film of Example 5 using the coating liquid (C-5) for coating has a short charge decay time and has an antistatic function. (3) The alignment film of Comparative Example 1 using the coating liquid (C-8) for forming an inorganic compound fine particle layer containing silica particles having an average particle diameter of more than 100 nm has a hardness because the particle diameter of the inorganic compound fine particles is too large. Was slightly inferior, and the film was slightly whitened. (4) The amount of the stabilizer in the inorganic compound fine particle layer after curing is
The alignment film of Comparative Example 2 using 100 parts by weight of the inorganic compound fine particles and 100 parts by weight of the coating liquid (C-9) had an insufficient curing temperature and was whitened.

[0050]

Example 8 With respect to the transparent electrode substrate having an alignment film formed thereon in Example 1, the resistance value after forming the alignment film was measured. As a result, 1c
The line resistance value per m was as follows.

[0051] Line resistance before alignment film formation 10Ω Line resistance after alignment film formation 11Ω

[0052]

[Comparative Example 3] Except that the heat curing conditions after drying with the coating liquid (C-9) on the electrode surface of the same substrate with the transparent electrode used in Examples 1 to 7 were 300 ° C and 30 minutes. Formed a fully protective transparent protective film under the same conditions as in Comparative Example 2. An alignment film was formed thereon under the same conditions as in Examples 1-7. The resistance value of this alignment film-formed transparent electrode substrate was determined as in Example 8.
As a result of the same measurement as above, the line resistance value per cm is 2
It was 5Ω.

[0053]

Example 9 and Comparative Example 4 Using the alignment film-formed transparent electrode substrates of Examples 1 to 7 and the transparent electrode substrate having the alignment film directly formed on the ITO electrode by the alignment film-forming resin as Comparative Example 4 were used. , 10 sets of STN liquid crystal cells each having a cell gap of 6.5 μm were prepared, and the number of cells in which the upper and lower substrates were short-circuited was measured.

As a result, regarding the STN liquid crystal cells produced using the alignment film forming transparent electrode substrates of Examples 1 to 7,
I didn't short all. On the other hand, in the STN liquid crystal cell manufactured using the alignment film-formed transparent electrode substrate of Comparative Example 4, 2 out of 10 sets were short-circuited.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing an example of a liquid crystal display cell according to the present invention.

FIG. 2 is a drawing for explaining an example of a process of forming an alignment film containing fine particles of an inorganic compound according to the present invention. (1) of FIG. 2 shows a transparent surface having a transparent electrode. FIG. 2 is a cross-sectional view schematically showing an example of a substrate, and FIG. 2 (2) shows a state in which a coating liquid for forming a fine particle layer in which fine particles of an inorganic compound are dispersed is applied to the surface of a transparent electrode provided on a transparent substrate. FIG. 3 is a schematic cross-sectional view showing (3) in FIG.
FIG. 4 is a schematic cross-sectional view showing a state after the dispersion liquid is removed by drying the coating liquid for forming an inorganic compound fine particle layer applied on the surface of the transparent electrode, and (4) in FIG. FIG. 3 is a schematic cross-sectional view showing a substrate with a transparent electrode, in which an alignment film containing fine particles of an inorganic compound is provided.

[Explanation of symbols]

1 ... Liquid crystal display cell 2 ... substrate with transparent electrode 3 ... Spacer 4 ... Liquid crystal 21 ··· Transparent substrate 22 ··· Transparent electrode 23 ... Inorganic compound fine particles 24 ... Alignment film 25 ··· Water and / or organic solvent 26 ... Coating liquid for forming inorganic compound fine particle layer 27 ··· Alignment film forming resin d ・ ・ ・ ・ ・ Gap between a pair of alignment films (thickness of liquid crystal layer)

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-1-113733 (JP, A) JP-A-3-55520 (JP, A) JP-A-3-55521 (JP, A) JP-A-3- 233428 (JP, A) JP 4-247427 (JP, A) JP 6-148617 (JP, A) JP 6-289379 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02F 1/13-1/141

Claims (2)

(57) [Claims] 1. A liquid crystal display cell comprising a substrate with a transparent electrode, in which a transparent electrode and an alignment film are sequentially laminated on a substrate, wherein the alignment film contains inorganic compound fine particles, and the inorganic compound fine particles are an alignment film. A liquid crystal display having a concentration gradient in the thickness direction, in which the concentration of the inorganic compound fine particles increases toward the transparent electrode side, and a part of the resin forming the alignment film is directly bonded to the transparent electrode. cell. 2. When manufacturing a liquid crystal display cell comprising a transparent electrode substrate in which a transparent electrode and an alignment film are sequentially laminated on a substrate, inorganic compound fine particles are dispersed on the surface of the transparent electrode formed on the substrate. After applying a dispersion liquid dispersed in a medium, the dispersion medium is removed to form a layer composed of inorganic compound fine particles,
Then, a coating liquid containing a resin for forming an alignment film is applied on the inorganic compound fine particle layer so that a part of the resin for forming an alignment film is directly bonded to the transparent electrode, thereby forming an inorganic compound on the surface of the transparent electrode. A method for manufacturing a liquid crystal display cell, which comprises forming an alignment film containing fine particles.