JP3976210B2 - Coating liquid for protective film formation - Google Patents

Description

★１：得られた塗布液に、ジプロピレングリコール４５０ｇ、ジプロピレングリコールモノメチルエーテル２００ｇを加え、マントルヒーター で加温し、低沸点物を留去したものを最終塗布液として使用したもので、ソーダガラス上への塗布手段として印刷法を使用した。
【００３９】
（ｉｉ）保護膜の形成
上記保護膜形成用塗布液をスピンナーにて、ソーダガラス上に塗布し、オーブン中で１００℃、１５分間乾燥したのち、さらに電気炉により３５０℃で３０分間焼成してソーダガラス上に保護膜を形成し、その保護膜の膜厚、屈折率、曇り度合及び均質性を調べた。その結果を表２に示す。また、それぞれの塗布液を調製後、２週間室温で静置したときの塗布液の濁りを観察した結果を保存安定性として表２に示した。
【００４０】
【表２】

曇り度合※：全自動直読ヘーズコンピューター（スガ試験機社製；ＨＧＭ− ２ＤＰ）を使用して測定。
【００４１】
評価法
均質性；○：表面の荒れ、クラックが確認できないもの。
×：表面の荒れ、クラックが発生したもの。
保存安定性；○：調製後、２週間室温で静置した状態で塗布液中に濁りが発生しなかったもの。
×：調製後、２週間室温で静置した状態で塗布液中に濁りの発生が確認できたもの。
【００３９】
【発明の効果】
本発明の保護膜形成用塗布液は、低温で焼成でき、得られた保護膜は配向膜に静電気を帯電させることがなく、しかも保護膜表面に荒れや曇りがないところから輝度に優れた液晶素子を製造でき、かつ保存安定性にも優れている上に、取扱が容易で工業的にも有用な塗布液である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coating solution for forming a protective film, and more particularly to a coating solution having a low storage degree and a high degree of storage stability while being able to form a protective film having excellent homogeneity.
[0002]
[Prior art]
Conventionally, liquid crystal display elements are sequentially formed of a transparent electrode film made of an inorganic material such as ITO and an alignment film made of an organic polymer material such as polyimide on a substrate made of transparent glass, acrylic, polyethylene terephthalate (PET) or the like. It is manufactured by laminating, arranging the substrates with laminated electrodes almost in parallel at predetermined intervals, sealing the periphery with frit glass or organic adhesive, etc. to form a cell, and encapsulating liquid crystal in the cell ing.
[0003]
[Problems to be solved by the invention]
However, in the manufacture of the conventional liquid crystal display element, the alignment film is rubbed, but static electricity is generated when the alignment film is rubbed, and the alignment film is charged. Due to the charged static electricity, discharge occurs through the transparent electrode film, and there is a problem that the alignment characteristics change due to heat generated in the alignment film. Therefore, it has been proposed to interpose a protective film between the transparent electrode film and the alignment film, and some protective film forming materials have been proposed. One of the protective film forming materials is a coating solution containing a silanol compound, and the coating solution is applied and baked at 400 ° C. or higher to form a film mainly composed of silicon dioxide. In order to achieve this, it is necessary to increase the firing temperature. At this time, the transparent electrode is also exposed to a high temperature, so that the electrode is deteriorated and the surface resistance value of the film is increased. Further, the high baking temperature is not only deteriorated by electrodes, but also has a problem that it cannot be used for recently developed plastic liquid crystal display elements using a resin such as acrylic or PET as a substrate.
[0004]
Accordingly, a coating liquid containing conductive fine particles having an average particle diameter of 200 mm or more and a hydrolyzate of an alkoxysilane compound or a metal alkoxy compound has been developed as a protective film forming material for solving the above problems, and a liquid crystal display cell using the same Has been proposed (Japanese Patent Laid-Open No. 5-232459). When the coating liquid for forming the protective film is used, a film having a practical hardness is formed at about 350 ° C., and the alignment film is difficult to be charged. However, the degree of cloudiness of the formed protective film is high, and Since the homogeneity is also poor, there is a problem that a liquid crystal display element having practical luminance cannot be obtained, and there is also a drawback that the storage stability of the coating solution is poor.
[0005]
As described above, in the field of manufacturing liquid crystal display elements, a practical hardness can be obtained at a low temperature as a protective film-forming coating solution interposed between the alignment film and the transparent electrode film, and the alignment film can be charged. In addition, there has been an urgent need to develop a coating solution that has a low haze level, can form a film with excellent homogeneity, and has high storage stability.
[0006]
In view of the above situation, the present inventors have conducted extensive research and as a result, in the coating liquid for forming a protective film containing conductive fine particles and a hydrolyzate of an alkoxysilane compound or a metal alkoxy compound, the conductive fine particles The present invention has been completed by finding out that a coating solution having the above-mentioned problems can be obtained by containing an organic carboxylic acid compound in the coating solution while being specified in a specific range. That is, [0007]
An object of the present invention is to provide a coating liquid for forming a protective film that can obtain a practical hardness at a low temperature and that does not cause charging in an alignment film.
[0008]
Another object of the present invention is to provide a coating solution for forming a protective film that has a low haze level, can form a uniform film, and is excellent in storage stability.
[0009]
[Means for Solving the Problems]
The present invention that achieves the above object provides (a) a hydrolyzate of at least one alkoxy compound selected from an alkoxysilane compound and a metal alkoxy compound, and (b) 20 to 70% by weight of conductive fine particles having an average particle size of 50 mm or less , and (c) at least one organic carboxyl selected from oxalic acid, tartaric acid, succinic acid, malic acid, citric acid, lactic acid, glycolic acid, acetic acid or formic acid The present invention relates to a coating liquid for forming a protective film for a liquid crystal display element, which contains an acid .
[0010]
Hereinafter, the present invention will be described in detail.
The component (a) used in the coating liquid for forming a protective film for a liquid crystal display element of the present invention is a hydrolyzate of at least one alkoxy compound selected from an alkoxysilane compound and a metal alkoxy compound. Examples thereof include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, monomethyltrimethoxysilane, monoethyltriethoxysilane, monoethyltrimethoxysilane, and monomethyltriethoxysilane. Examples of the metal alkoxy compound include tetraisopropoxy titanium, tetrabutoxy titanium, tetraethoxy zirconium, tetrapropoxy zirconium, tetrabutoxy zirconium, pentaethoxy tantalum, pentapropoxy tantalum, and pentaboxy tantalum. These alkoxysilane compounds and metal alkoxy compounds may be used alone or in combination of two or more. When the alkoxysilane compound and the metal alkoxy compound are used in combination, the mixing ratio is preferably in the range of 10:90 to 90:10 in terms of oxide-converted weight ratio.
[0011]
Moreover, as an alkoxy compound used by (a) component, the complex compound obtained by making said alkoxysilane compound, a metal alkoxy compound, or mixtures thereof react with (beta) -diketone compounds, such as acetylacetone, can also be used.
[0012]
The component (a) is a hydrolyzate of an alkoxy compound. The hydrolyzate dissolves the alkoxy compound in an organic solvent, and in the presence of water, preferably an acid catalyst such as hydrochloric acid, nitric acid, phosphoric acid or the like. And can be produced by a conventional hydrolysis method. The amount of water used in the hydrolysis reaction is in the range of 0.1 to 10 times the mole of the alkoxy compound. Moreover, the usage-amount of an acid catalyst has the preferable range of 0.001 to 5 weight% with respect to (a) component.
[0013]
Specific examples of the organic solvent for dissolving the alkoxy compound include monohydric alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, and butyl alcohol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, hexylene glycol, Polyhydric alcohols such as octylene glycol, ethylene glycol monomethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene Glycol monopropyl ether, propylene glycol monobutyl ether, Tylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol Ethers such as monopropyl ether, dipropylene glycol monobutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, propion Methyl, ethyl propionate, ethyl lactate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether Examples thereof include esters such as acetate, propylene glycol monoethyl ether acetate, propylene glycol monobutyl ether acetate and dipropylene glycol monomethyl ether acetate. These organic solvents may be used alone or in combination of two or more. Good.
[0014]
(B) component of the liquid crystal display element for forming a protective film coating liquid of the present invention has an average particle size of 50Å or less of the conductive fine particles is not particularly limited as long as the average particle diameter 50Å or less of the fine particles in particulate exhibits conductivity . Specific examples of the conductive fine particles include inorganic oxide fine particles such as zinc oxide, tin oxide, antimony oxide, and indium oxide, and composite inorganic oxide fine particles such as tin oxide-antimony oxide, indium oxide-tin oxide, and titanium oxide-tin oxide. These conductive fine particles may be used alone or in combination of two or more. The conductive fine particles need to have an average particle size of 50 mm or less . By setting the thickness to 50 mm or less, a practical protective film having a low haze degree and excellent homogeneity can be formed, and a liquid crystal display element having particularly good luminance can be obtained. The conductive fine particles are preferably blended in the form of a sol in which powdery or colloidal particles are dispersed in the preparation of a coating liquid for forming a protective film for a liquid crystal display element .
[0015]
The blending amount of the conductive fine particles is in the range of 20 to 70% by weight with respect to the oxide equivalent amount of the component (a). If this blending amount exceeds 70% by weight, a stable coating solution cannot be obtained. Further, it is not preferable because it becomes a film having a high haze, and if it is less than 20% by weight, it is not preferable because the film has a reduced strength.
[0016]
The organic carboxylic acid which is the component (c) of the present invention is blended in order to improve the storage stability of the coating solution. As a blending method thereof, a method of blending as one component of the coating solution, or ( There is a method of blending the organic carboxylic acid as the component c) as a solution in which the conductive fine particles of the component (b) are dispersed. Examples of the organic carboxylic acid include lactic acid, glycolic acid, acetic acid, formic acid, oxalic acid, tartaric acid, succinic acid, malic acid, and citric acid.
[0017]
The amount of the organic carboxylic acid is 0.1 to 50% by weight in the coating solution, preferably 0.3 to 40% by weight. This is not preferable because the properties deteriorate.
[0018]
The coating liquid of the present invention is preferably used in the form of mixing the above components (a), (b) and (c) with water and / or an organic solvent as a solvent or dispersion medium. Examples of the solvent include ethers such as monohydric alcohols, polyhydric alcohols and polyhydric alcohol ethers, ketones such as acetone, methyl ethyl ketone, acetylacetone, methyl isobutyl ketone and dibutyl ketone, methyl acetate, butyl acetate and acetic acid. Examples thereof include esters such as propyl, isobutyl acetate and isoamyl acetate. Preferred are ethers such as monohydric alcohols, polyhydric alcohols, and polyhydric alcohol ethers.
[0019]
In addition, inorganic oxide fine particles having no electrical conductivity can be blended in the coating solution of the present invention within the range not impairing the object of the invention. Examples of the fine particles include silicon oxide, titanium oxide, zirconium oxide, and tantalum oxide, and these can be used alone or in combination of two or more. By arbitrarily selecting and blending the inorganic oxide fine particles, the refractive index of the protective film can be adjusted, and the adhesion to the alignment film can be improved.
[0019]
The coating liquid of the present invention comprises a method of mixing all of the components (a), (b) and (c) with a solvent, a solution containing the component (a) and a solution containing the component (b). It can be prepared by a method of adding the component (c) to the mixture or a method of blending a solution containing the component (a) with a solution in which the component (b) is dispersed in the component (c). The thus-prepared coating solution for forming a protective film is applied to the electrode surface formed on the substrate by a dipping method, spin coating method, spray method, roll coater method, printing method, or the like, and then the formed coating The film is dried under heating and / or reduced pressure or aeration, and further cured at 120 to 400 ° C., preferably 140 to 350 ° C., to form a protective film.
[0020]
After the coating step or the drying step, the coating curing reaction is accelerated by, for example, electromagnetic wave irradiation or curing accelerating gas treatment, the polymerization reaction of the hydrolyzate of the alkoxysilane compound is accelerated, the water or solvent present in the coating It is also possible to promote the evaporation of.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention in detail, this invention is not limited by these examples.
[0022]
【Example】
Examples 1-9 and Comparative Examples 1-2
(I) Preparation of coating solution for forming protective film (A) Manufacturing solution A- (1)
To a mixed solution of 284 g of tetraisopropoxytitanium and 547 g of ethyl alcohol, while adding 100 g of acetic acid and 300 g of acetylacetone and stirring, a mixed solution of 100 g of N-methyl-2-pyrrolidone and 1.8 g of pure water was further added. Obtained solution.
[0023]
Solution A- (2)
A solution obtained by adding 100 g of acetic acid and 300 g of acetylacetone to a mixed solution of 284 g of tetraisopropoxytitanium and 547 g of ethyl alcohol, and further adding a mixed solution of 100 g of ethyl alcohol and 1.8 g of pure water.
[0024]
Solution A- (3)
While adding 90 g of acetic acid and 325 g of ethyl 3-hydroxybutanoate to a mixed solution of 340 g of tetrabutoxytitanium and 474 g of ethyl alcohol, stirring, a mixed solution of 100 g of N-methyl-2-pyrrolidone and 3.6 g of pure water was added. Solution obtained by addition.
[0025]
Solution B- (1)
A solution obtained by adding 240 g of acetic acid to a mixed solution of 208 g of tetraethoxysilane and 450 g of ethyl alcohol and stirring, and further adding a mixed solution of 100 g of ethyl alcohol and 1 g of 35 wt% hydrochloric acid.
[0026]
Solution B- (2)
A solution obtained by adding 210 g of acetic acid and 200 g of acetylacetone to a mixed solution of 208 g of tetraethoxysilane and 300 g of ethyl alcohol, and further adding a mixed solution of 1 g of phosphorus pentoxide and 80 g of methyl alcohol.
[0027]
Solution B- (3)
A solution obtained by adding 210 g of acetic acid and 200 g of acetylacetone to a mixed solution of 152 g of tetramethoxysilane and 350 g of ethyl alcohol and stirring, and further adding a mixed solution of 100 g of methyl alcohol and 1 g of 60 wt% nitric acid.
[0028]
Solution B- (4)
To a mixed solution of 208 g of tetraethoxysilane, 200 g of ethyl alcohol, 250 g of acetylacetone and 100 g of N-methyl-2-pyrrolidone, a mixed solution of 0.7 g of 35% by weight hydrochloric acid and 72 g of pure water is added, and further N-methyl-2- A solution obtained by adding 170 g of pyrrolidone.
[0029]
Solution C- (1)
A 6 wt% solution of tin oxide sol obtained by adding tin oxide having an average particle size of 30 mm to a mixed solvent of lactic acid: acetic acid: water = 10: 45: 45 by weight ratio.
[0030]
Solution C- (2)
A 6 wt% solution of tin oxide sol obtained by adding tin oxide having an average particle size of 30 mm to a mixed solvent of lactic acid: acetic acid: water = 2: 50: 48 by weight ratio.
[0031]
Solution C- (3)
A 6% by weight solution of a tin oxide sol obtained by adding tin oxide having an average particle size of 30 mm to a mixed solvent of lactic acid: acetic acid: N-methyl-2-pyrrolidone: water = 10: 30: 30: 30 in a weight ratio.
[0032]
Solution C- (4)
Obtained by adding tin oxide having an average particle size of 30 mm to a mixed solvent of citric acid: N-methyl-2-pyrrolidone: diethylene glycol monobutyl ether: dipropylene glycol: water = 30: 15: 15: 35: 5 by weight ratio 6 wt% solution of tin oxide sol.
[0033]
Solution C- (5)
A 6% by weight solution of a tin oxide sol obtained by adding tin oxide having an average particle diameter of 30 mm to a mixed solvent of ammonia: water = 1.2: 98.8 in a weight ratio.
[0034]
Solution C- (6)
A 6% by weight solution of a tin oxide sol obtained by adding tin oxide having an average particle size of 200 kg to a mixed solvent of lactic acid: acetic acid: water = 10: 45: 45 by weight ratio.
[0035]
Solution D- (1)
Add 666 g of acetylacetone to a mixed solution of 340 g of tetrabutoxytitanium, 152 g of tetramethoxysilane, 650 g of butyl alcohol, and 466 g of ethyl alcohol, and then add a mixed solution of 1.9 g of 60% by weight nitric acid and 54 g of pure water. Solution obtained.
[0036]
Solution D- (2)
After adding 666 g of acetylacetone to a mixed solution of 170 g of tetrabutoxytitanium, 152 g of tetramethoxysilane, 125 g of tetrabutoxyzirconium, 628 g of butyl alcohol and 533 g of ethyl alcohol, and stirring, 1.9 g of 60 wt% nitric acid and 54 g of pure water A solution obtained by adding a mixed solution of
[0037]
(B) Preparation of coating solution A coating solution for forming a protective film having the composition shown in Table 1 was prepared using each of the above solutions.
[0038]
[Table 1]

* 1: 450 g of dipropylene glycol and 200 g of dipropylene glycol monomethyl ether are added to the obtained coating solution, heated with a mantle heater, and the low boiling point product is distilled off as the final coating solution. A printing method was used as a coating means on glass.
[0039]
(Ii) at the forming the protective layer coating solution for forming the protective film spin toner was applied onto a soda glass, 100 ° C. in an oven, after drying for 15 minutes, fired for a further 30 minutes at 350 ° C. in an electric furnace Then, a protective film was formed on soda glass, and the film thickness, refractive index, haze degree and homogeneity of the protective film were examined. The results are shown in Table 2. In addition, Table 2 shows the results of observing the turbidity of the coating liquid when the coating liquid was prepared and allowed to stand at room temperature for 2 weeks after preparation.
[0040]
[Table 2]

Cloudiness degree *: Measured using a fully automatic direct reading haze computer (manufactured by Suga Test Instruments Co., Ltd .; HGM-2DP).
[0041]
Evaluation method homogeneity: ○: Surface roughness and cracks cannot be confirmed.
X: Surface roughness and cracks occurred.
Storage stability: ◯: No turbidity occurred in the coating solution after standing for 2 weeks at room temperature.
X: The thing which has confirmed generation | occurrence | production of turbidity in a coating liquid in the state left still at room temperature for 2 weeks after preparation.
[0039]
【The invention's effect】
The coating liquid for forming a protective film of the present invention can be baked at a low temperature, and the obtained protective film does not charge the alignment film with static electricity, and the liquid crystal is excellent in luminance because the surface of the protective film is not rough or cloudy. It is a coating solution that can be used to produce an element and has excellent storage stability, is easy to handle, and is industrially useful.

Claims (2)

(a) hydrolyzate of at least one alkoxy compound selected from an alkoxysilane compound and a metal alkoxy compound, (b) an average particle size of 50 to 70% by weight with respect to the oxide equivalent of component (a) And (c) at least one organic carboxylic acid selected from oxalic acid, tartaric acid, succinic acid, malic acid, citric acid, lactic acid, glycolic acid, acetic acid, or formic acid. Coating liquid for forming a protective film for liquid crystal display elements . 2. The protective film-forming coating solution for a liquid crystal display element according to claim 1, wherein the organic carboxylic acid is contained in the coating solution in an amount of 0.1 to 50% by weight.