JP2706702B2 - Electrodeposition coating bath - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrodeposition coating, and in particular, to a high-definition liquid crystal display device using a color filter.
The present invention relates to an electrodeposition coating bath suitable for fields requiring high transparency and high smoothness.

[Conventional technology]

Here, the principle and method of electrodeposition used in the present invention will be described below.

This electrodeposition is a method of insolubilizing and precipitating a polymer on an electrode with a polymer solution, and is called a polymer electrodeposition method. As an example of this, a method called electrodeposition coating in which a pigment is dispersed in an aqueous polymer solution, a metal is immersed and used as an electrode, and a colored layer is electrodeposited on the metal is industrially known. And so on. The principle of this method is to use a polymer in which a hydrophilic group, for example, a carboxyl group is introduced into a polymer, and the carboxyl group is neutralized and made water-soluble with an inorganic alkali, an organic amine or the like. When the electrode is immersed in a water-soluble polymer aqueous solution and a voltage is applied, the dissociated carboxy anions in the aqueous solution electrophores toward the anode, reacting with the protons generated by the electrolysis of water on the electrode. The polymer becomes insoluble and precipitates. That is, the reaction represented by the following formula occurs on the anode, and deposition of the polymer is observed.

When a basic group such as a polyamine is used as the hydrophilic group and neutralized with an acid and made water-soluble, a polymer is precipitated on the cathode.

When the electrodeposited polymer is electrically insulating, it is thought that the electrode is coated and the current decreases, preventing further coating. Due to the generated oxygen bubbles, the initial complete coating is avoided, and a certain thickness is obtained before the insulating layer is formed. Usually, in electrodeposition coating, a film thickness of 10 to 20 microns is obtained by applying a voltage of 100 V to 200 V, but in the case of a color filter application requiring high definition and high definition according to the present invention, the film thickness is If it is too thick, high definition, high transparency and high clarity will be lost. Therefore, the colored layer is preferably thinner and preferably about 1 micron. Therefore, it is necessary to optimally design the polymer resin concentration, applied voltage, and solvent composition.

The polymer film thus obtained has a low water content due to the effect of electroosmosis, and is a uniform film having better adhesion than a film produced by a coating method or the like.

Examples of the polymer for anion electrodeposition include an adduct of natural drying oil and maleic acid, an alkyd resin having a carboxyl group introduced, an adduct of an epoxy resin and maleic acid, a polybutadiene resin having a carboxyl group introduced, acrylic acid or methacrylic acid. A copolymer with the ester is used,
Depending on the characteristics of the electrodeposition film, another polymer or an organic compound having a functional group may be introduced into the polymer skeleton. When importance is placed on the appearance such as transparency and gloss, acrylic or polyester polymers are suitable. In addition, the amount of the hydrophilic functional groups such as carboxyl groups and hydroxyl groups in the polymer is important. If the amount of the hydrophilic groups is too large, the electrodeposition layer is not sufficiently insolubilized, resulting in a nonuniform film. The water solubility at the time becomes insufficient.

As a polymer solvent, water is a main component, but hydrophilic such as isopropanol, n-butyl alcohol, t-butyl alcohol, methyl cellosolve, ethyl cellosolve, isopropyl cellosolve, butyl cellosolve, diethylene glycol methyl ether, diethylene glycol ethyl ether, diacet alcohol, etc. A non-ionic solvent may be included as a solvent for polymerizing a polymer. The kind and amount of the hydrophilic solvent contained also has a large effect on the film thickness and the uniformity of the electrodeposited layer. And electrophoresis together with the membrane. As the pigment used, titanium oxide, precipitated barium sulfate, talc, asbestin, china clay, red iron oxide, yellow oxidized carbon, strontium chromate, basic lead silicate, phthalocyanine blue, phthalocyanine green, hansa yellow, carbon black, etc. is there.

As the high dielectric fine particles to be used for the purpose of requesting a high _{dielectric, TiO 2, BaTiO 3, MgTiO} 3, CaTiSiO 5, SrTiO 3, BaZr
O ₃ -PbZrO ₃ , BaZrO ₃ -PbSnO ₃ , BaTiO ₃ -Bi ₂ (Sn
_{O 3) 3, BaTiO 3 -NiSnO} 3, BaTiO 3 -SrSb 2 O 6, BaTiO 3 -B
aSb ₂ O ₆ , BaTiO ₃ -PbSb ₂ O ₆ , (LaNa) FeO ₃ -Bi ₂ O ₃ , MgO
・ SiO ₂ , 2MgO ・ SiO ₂ , 2MgO ・ 2Al ₂ O ₃・ 5SiO ₂ , ZrO ₂・ SiO
₂ , Be.O, Al ₂ O ₃ , BN and the like.

Examples of the conductive material include fine particles of an oxide semiconductor such as tin oxide, indium oxide, antimony oxide, zinc oxide, and cadmium oxide, and fine particles of a chemically stable metal such as gold, silver, and nickel. In general, coatings electrodeposited from an electrodeposition coating bath, in which fine particles and polymers are dispersed in water due to problems such as irregularity, inclusion of large particles, and difficulty in dispersing in primary particles, are generally Many materials have poor transparency and smoothness due to particle size problems, and materials that can be practically used for color filters are limited, and there is a clear coating film with transparency and transparency utilizing the base such as ITO. At present, a coating film cannot be obtained, and the function of the material cannot be sufficiently utilized, and a method for obtaining a clear, transparent, and smooth coating film having hue and functionality is desired.

[Problems to be solved by the invention]

Therefore, the present invention has devised a method of classifying particles by a stationary method of an electrodeposition bath, and makes use of the functions of various materials by performing electrodeposition in the bath, and furthermore, has a clear, smooth and transparent color filter. To obtain an electrodeposition coating film for use.

[Means for solving the problem]

That is, the present invention is a bath in which an electrodepositable polymer having solubility or dispersibility in water and a dye, a conductive material, a high-induction material, and other functional particles are mixed. By allowing the electrodeposition coating bath used for electrodepositing the coating layer on the electrode to stand,
An object of the present invention is to provide an electrodeposition coating bath for a color filter obtained by classifying particles in the bath.

In the present invention, in order not to impair the transparency of the coating film, the average particle diameter of the particles is preferably 0.4μ, which is half the 0.8μ which is the upper limit of the visible light wavelength, or less, more preferably the visible light wavelength. It is 0.2 μ, which is half the lower limit of 0.4 μ, or less.

Needless to say, the smaller the particle size, the better the smoothness of the coating film.

If the particle diameter is about 0.1μ in water, the particles hardly settle due to Brownian motion of the particles, and those that do not settle almost semi-permanently can be made.

Due to the above facts, the electrodeposition bath solution is allowed to stand under a certain condition, and large particles which are not related to the effect of the Brownian motion are settled,
By separating and using, an electrodeposition bath solution for a color filter containing only an ideal particle size can be prepared.

The coating film electrodeposited using the electrodeposition bath solution prepared by this method was excellent in transparency, clarity, and smoothness, and exhibited the intended function.

In this way, the range of usable functional particles can be expanded, and applications in a wide range of fields for color filters can be made possible.

〔Example〕

Hereinafter, the contents of the present invention will be specifically described with reference to examples.
The middle part of the examples is parts by weight unless otherwise specified.

Example 1 The following anionic electrodeposition bath was prepared.

[For photodielectric coating] Green polyester resin (manufactured by Shinto Paint Co., Ltd.) 60 parts Melamine resin (manufactured by Niclac MX-40 Sanwa Chemical Co., Ltd.) 15 butyl cellosolve 45 n-butanol 4 triethylamine 5 ion-exchanged water 841 barium titanate (ratio Dielectric constant 1500) 22 Phthalocyanine green (manufactured by SAX Sanyo Dyeing Co., Ltd.) 8 Total 1000 Non-volatile content 75%, acid value 50 (acid value is the number of mg of KOH required to neutralize 1 g of resin solids), viscosity 60 boise (25 ° C) 40 parts of 60 parts of polyester resin and methyl cellosolve
45 parts, barium titanate and phthalocyanine green were dispersed in a laboratory dispersing machine Sand Grind Mill (manufactured by Asada Iron Works) for 20 hours.

After adding the remaining polyester resin, melamine resin, and n-butanol to the dispersed composition and thoroughly mixing the mixture, neutralize with triethylamine and dilute with ion-exchanged water to obtain a highly inducible polymer resin electrodeposition composition. I made an electrodeposition bath. The MEQ of the resulting bath was 55.

 The acid value and MEQ were measured by the following methods.

Measurement method of acid value A certain amount of resin is dissolved in a certain amount of alcohol or ether, and phenolphthalein is used as an indicator, and the solution is titrated with 1 / 2N potassium hydroxide.

The number of mg of potassium hydroxide required for the titration is converted into 1 g of resin solid content, and the value is defined as the acid value.

MEQ measurement (milli-equivalent of the basic component contained in 100 g of solid content) A 20 ml sample of the bath solution was precisely weighed, 100 ml of ethylene glycol monobutyl ether was added, and the mixture was placed under stirring. Measure the PH value with and draw a titration curve. From the two inflection points of the titration curve, the midpoint is determined, and the titer of 1 / 10N hydrochloric acid required up to the midpoint is determined.

 Next, the base concentration is calculated by the calculation formula of MEQ.

MEQ = (v × f / c) × 50 where v: titration of 1 / 10N hydrochloric acid required up to the midpoint (ml) f: titer of 1 / 10N hydrochloric acid c: heating residue of sample (%) This solution contains 25% by weight of barium titanate in solids in MEQ55 as highly dielectric particles.

The electrodeposition bath prepared as described above was allowed to stand by the following method to classify large particles.

Prepare 1 liter and 3 tall beakers, take 1 liter of the above bath solution for each, set it as A, B, C, and let each stand still for the following time. Was done.

(1) Measurement of average particle size of bath (2) Evaluation of electrodeposition coating Stirring at 20 ° C, using glass as a substrate, and using a transparent substrate having an indium oxide conductive film formed thereon by a spray coating method as an anode, A voltage of 20 V was applied between both electrodes for 30 seconds using a platinum plate as an opposite electrode as a cathode.

Next, the polyester resin and the melamine resin in the colored layer formed by electrodeposition were cured by baking to cause a condensation reaction. Baking was performed in air at 175 ° C. for 30 minutes.

The bath standing time, average particle size, and coating characteristics are as shown in Table 1. In the case of standing compared to A-1 (blank), the relative permittivity hardly changed, and other items were not changed. All were improved, and a practical transparent coating film was obtained.

Example 2 The following anionic electrodeposition bath was prepared.

[For dielectric coating] Blue polyester resin (manufactured by Shinto Paint Co., Ltd.) 60 parts Melamine resin (manufactured by Nikalac MX-40 Sanwa Chemical Co., Ltd.) 15 butyl cellosolve 45 n-butanol 5 triethylamine 4 ion-exchanged water 851 tin oxide (conductive) Fine powder T-1 manufactured by Mitsubishi Metals Corporation) 12 Phthalocyanine blue (SR-150C manufactured by Sanyo Dyeing Co., Ltd.) 8 A total of 1000 baths were prepared in the same manner as in Example 1 and the bath was allowed to stand and the average particle size was measured. Evaluation of the coating film by electrodeposition was performed in the same manner as in Example 1.

As shown in Table 2, the conductivity was not changed by standing the bath solution, and a coating film having good transparency and uniformity was obtained.

[Measurement equipment] Average particle size: Coulter counter No. 4 (Coulter counter) Surface roughness: Dick Tack II (manufactured by Nippon Vacuum Co., Ltd.) Peak transmittance: Color Aralizer TC1800M (Tokyo Denshoku) Haze: Haze Meter (Suga Test Machine) Volume resistivity: High Meg Ohm Meter (Takeda Riken) [Effect of the Invention] The electrodeposition coating bath according to the present invention has the same stability and operability as the conventional electrodeposition bath. The wide application of the functional particles greatly expands the application of the electrodeposition coating to not only a transparent processed product but also a wide range of high definition products.

Claims (2)

(57) [Claims] 1. A bath in which an electrodepositable polymer having solubility or dispersibility in water is mixed with a dye, a conductive material, a high dielectric material and other functional particles, and an electrode is immersed in the bath to apply a voltage. An electrodeposition coating bath for a color filter, wherein the particles in the bath are classified by leaving the electrodeposition coating bath used for electrodepositing a coating layer on the electrode. 2. The electrodeposition coating bath for a color filter according to claim 1, wherein the average particle diameter of the particles contained in the bath after classification is 0.2 μm or less.