JP2003013008A - Aqueous light-shielding coating composition for display device and insulating light-shielding film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulating light-shielding film for a display device having a high light-shielding property and a high surface electric resistance value at the same time, and an aqueous light-shielding paint composition for a display device for forming the same. The oxidized carbon black has a degree of polymerization of 100.
A water-based light-shielding coating composition for a display device, comprising 0 to 3000 water-soluble resin and water, wherein the content ratio of the oxidized carbon black and the water-soluble resin is in the range of 1: 2 to 1: 3 by mass ratio. And an insulating light-shielding film for a display device formed using the water-based light-shielding coating composition for a display device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous light-shielding coating composition for electric field-driven display devices and an insulating light-shielding film formed by using the aqueous light-shielding coating composition for display devices. Specifically, an aqueous light-shielding coating composition used in the field of a black matrix member for a color filter used in a liquid crystal display, an insulating member for a reflective display device utilizing a spatial light modulator or selective reflection, and the like. The present invention relates to an insulating light-shielding film.

[0002]

2. Description of the Related Art In a display device such as an electric field drive type, as represented by a black matrix, it is possible to simultaneously impart a large light-shielding property (blackness) and a high surface electric resistance value to a finally obtained film. Materials are often required. Until now, organic solvent-based printing inks and pastes have been used as materials for light-shielding films that satisfy the required characteristics, but in recent years, there is a general tendency to limit the use of these organic solvents that adversely affect the environment and the human body. Becomes a target,
Water-based materials have also been demanded for the materials.

However, when a water-soluble black dye is used as a colorant to prepare an aqueous light-shielding coating composition, the light-shielding film to be obtained has a high surface electric resistance value, but has a high light-shielding property. Was difficult. In addition, a single dye has a narrow light absorption wavelength range, and even if a plurality of dyes having different absorption peak wavelengths are mixed to widen the absorption wavelength range, the solubility of the dye in water is not so high. However, there is a problem that it is difficult to give a large light-shielding property to the obtained light-shielding film. In addition, since dyes generally have poor light resistance, particularly ultraviolet resistance, they are not suitable as materials for display devices. On the other hand, when a carbon black pigment having a large absorption in the visible light wavelength region and excellent in light resistance is used, on the contrary, the light-shielding property of the obtained film is increased, but the conductivity mainly possessed by the carbon particles is increased. Due to the above, there is a problem that the surface electric resistance value of the light shielding film becomes low.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an insulating light-shielding film for a display device having a high light-shielding property (blackness) and a high surface electric resistance value at the same time, and a water-based display device for forming the same. It is intended to provide a light-shielding coating composition.

[0005]

Means for Solving the Problems The present inventor contains oxidized carbon black, a water-soluble resin having a degree of polymerization of 1000 to 3000, and water, and the content ratio of the oxidized carbon black and the water-soluble resin is mass. Provided is a water-based light-shielding coating composition for a display device having a ratio of 1: 2 to 1: 3, further comprising oxidized carbon black and a polymerization degree of 1000 to 3.
000 water-soluble resin, and the content ratio of the oxidized carbon black and the water-soluble resin is 1: 2 to 1: 3 by mass ratio.
The above problems have been solved by providing an insulating light-shielding film for a display device in the range of.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. Water-based light-shielding coating composition for display devices (hereinafter, "water-based light-shielding coating composition for display devices" unless otherwise specified)
Is simply referred to as a "light-shielding coating composition"), and when conductive carbon black, which has been widely used as a light-shielding pigment, is used, an insulating light-shielding film for display devices having a high surface electric resistance value (hereinafter referred to as "light-shielding coating composition") Unless otherwise specified, the "insulating light-shielding film for display device" cannot be simply referred to as "insulating light-shielding film". Therefore, in the present invention, an insulating light-shielding film satisfying the following required characteristics is provided by using a light-shielding coating composition using oxidized carbon black having a high electric resistance value in place of carbon black. 1. The light transmittance of the insulating light-shielding film having a thickness of 2 μm is 400 n
1% or less in the wavelength range of m to 800 nm. 2. The surface electric resistance value of the insulating light-shielding film having a thickness of 2 μm is 1
Must be 0 ¹³ (Ω / □) or more.

[0007] The higher the degree of oxidation of oxidized carbon black, the lower the electric conductivity. The degree of oxidation of oxidized carbon black is determined by the inert gas melting-infrared absorption method (JIS Z261).
3-1976). The oxidized carbon black used in the present invention preferably has an oxygen content in the oxidized carbon calculated by the above measurement of 3% by mass or more, and particularly preferably 8% by mass or more. Oxidized carbon black having an oxygen content of about 3 to 5% by mass can be obtained by an electric field oxidation method, an ultraviolet irradiation method, or the like. However, in order to obtain an oxidized carbon black having a high degree of oxidation of 8% by mass, carbon black is used. It is better to oxidize with hypohalous acid or its salts. It is also possible to mix hypohalous acid and its salt and use them for the oxidation of carbon black.

Carbon black, which is a raw material for oxidized carbon black, is generally carbon powder obtained by thermal decomposition or incomplete combustion of natural gas or liquid hydrocarbons (heavy oil, tar, etc.). These are commercially available after being classified into channel black, furnace black, lamp black and the like according to the manufacturing method. The kind of carbon black used as a raw material is not particularly limited, and any of acidic carbon black, neutral carbon black and alkaline carbon black can be used.

Oxidized carbon black having an oxygen content of 8% by mass or more, which is obtained by an oxidation reaction using hypohalous acid or a salt thereof, comprises at least (a) a step of finely dispersing carbon black in water, and (b) ) A step of oxidizing with a hypohalous acid or a salt thereof, and (c) adjusting the oxidized carbon black concentration to 10 to 30% by mass after purifying the obtained oxidized carbon black dispersion. It can be manufactured.

Specific examples of the hypohalous acid or its salt include sodium hypochlorite and potassium hypochlorite, and sodium hypochlorite has a higher reactivity with carbon black. Are particularly preferred. In the oxidation reaction, carbon black and a hypohalite (for example, sodium hypochlorite) are charged in an appropriate amount of water, and the time is 5 hours or more, preferably about 10 to 15 hours, 50 ° C. or more, preferably 95 to 105 ° C. By stirring at. At that time, the carbon black is preferably subjected to an oxidation treatment in a finely dispersed state. The term “finely dispersed” means that the secondary particles of carbon black are finely crushed in water to be finely divided into primary particles or particles close to the primary particles. The average particle size of the finely dispersed carbon black is preferably 300 nm or less, more preferably 150 nm or less, most preferably 10 nm.
It is 0 nm or less.

Generally, fine dispersion is carried out by wet milling for 3 to 10 hours in an aqueous medium using a mill medium and a milling device. Glass beads, zirconia beads, magnetic beads, stainless beads, etc. are used as the mill medium.
Ball mills, attritors, fluo jet mixers, impeller mills, colloidal mills, sand mills [for example, bead mills, sand gliders, super mills, agitator mills, dyno mills (trade name)]
Etc.

However, depending on the kind of carbon black used as a raw material, it may be finely dispersed in a water solvent only by high-speed stirring using a homogenizer (homomixer). The fine dispersion does not necessarily have to be performed before the oxidation treatment, and the fine dispersion treatment may be performed simultaneously with the oxidation treatment by stirring or pulverizing in a water solvent such as hypohalite. The amount of hypohalite used varies depending on the type, but when converted to 100% sodium hypochlorite, 1.5 to 150% by mass, preferably 4 to 75% by mass, based on the mass of carbon black. %
Is.

The oxidized carbon black having an oxygen content of 8% by mass or more obtained in this manner is available as an aqueous dispersion that is stably dispersed in water, and specifically, "BONJET BLACK" manufactured by Orient Chemical Industry Co., Ltd. CW-1
(Average particle size of 100 nm or less) "and" BONJET BL
ACK CW-2 (average particle size of 200 nm or less) "and the like.

Further, a water-soluble resin is added to the light-shielding coating composition so that the coating film has a film-forming ability when it is coated on a support. The water-soluble resin is soluble in water, does not adversely affect the dispersibility of the oxidized carbon black, and can impart high insulation and chemical resistance to the insulating light-shielding film obtained by coating and drying the support. Those are preferable.

Examples of such water-soluble resins include completely saponified or partially saponified polyvinyl alcohol, water-soluble polyvinyl acetal, water-soluble polyvinyl formal, polyacrylamide, polyvinyl pyrrolidone,
Examples thereof include poly (meth) acrylic acid, water-soluble poly (meth) acrylic acid copolymer, polyalkylene oxide, water-soluble polyester, water-soluble maleic acid resin, and the like. Among them, polyvinyl alcohol, water-soluble polyvinyl acetal, water-soluble A polyvinyl alcohol derivative such as a poly (vinyl formal) is particularly preferable from the viewpoint of excellent film-forming ability, chemical resistance, and low cost.

On the other hand, there is a correlation between the degree of polymerization of the resin and the electric resistance value of the resin, and the higher the degree of polymerization, the higher the electric resistance value. Particularly in the present invention, in order to obtain an insulating light-shielding film having a high surface electric resistance value, the degree of polymerization of the water-soluble resin used is preferably 1000 to 3000, and more preferably 1300 to 2000. If the degree of polymerization is less than 1000, the surface resistance value will decrease, and if it exceeds 3000, the viscosity of the light-shielding coating composition will be high, making it difficult to apply it to the support.

Examples of the water-soluble resin used in the present invention include "Kuraray Poval PVA-HC" manufactured by Kuraray Co., Ltd.
W "," Kuraray Poval PVA-217C "," Exeval RS-2617 "and" Exeval RS-271 "
3 ”and the like, and examples of the polyvinyl acetal include“ S-REC KW-1 ”manufactured by Sekisui Chemical Co., Ltd. In the present invention, these water-soluble resins may be used alone or in combination of two or more.

When the insulating light-shielding film formed by using the light-shielding coating composition is used as a black matrix of a liquid crystal display device, the insulating light-shielding film is in direct contact with the liquid crystal material. When an insulating light-shielding film is formed on an electric field drive type display device such as a liquid crystal display device using the light-shielding coating composition of the present invention, if impurities are contained in the light-shielding coating composition, display characteristics of the display device are impaired. Sometimes. In particular, in the case of a liquid crystal display device in which the insulating light-shielding film and the display material are in direct contact with each other, it is preferable to minimize the content of ionic compounds such as metal ions and organic ions.

Further, it is necessary to increase the surface electric resistance value of the insulating light-shielding film so as not to affect the electric characteristics of the display device. In addition to the above-mentioned ionic impurities, the conductivity of carbon black can be cited as a factor that lowers the electric resistance value of the insulating light-shielding film. Generally, when highly conductive carbon black is used as the light-shielding pigment contained in the insulating light-shielding film, the content of carbon black must be reduced in order to obtain a desired surface electric resistance value. It is difficult to obtain performance.

In the present invention, by setting the content ratio of the oxidized carbon black and the water-soluble resin to be 1: 2 to 1: 3 by mass ratio, the resulting insulating light-shielding film has a high light-shielding property and a high anti-light-shielding property. It has become possible to give the surface electric resistance value at the same time. When the content ratio of the oxidized carbon black and the water-soluble resin exceeds 1: 2, that is, when the content ratio of the oxidized carbon black is high, the light-shielding property of the obtained insulating light-shielding film is improved, but the surface electric resistance value is decreased. When the ratio is less than 1: 3, that is, when the content of oxidized carbon black is low, the surface electric resistance value of the obtained insulating light-shielding film is improved but the light-shielding property is deteriorated.

Although water is mainly used as a solvent in the light-shielding coating composition of the present invention, an organic solvent having compatibility with water may be added within a range in which a water-soluble resin is not deposited.
Examples of such organic solvents include lower alcohols such as methanol and ethanol, acetone, dioxane and the like. The concentration of nonvolatile components in the light-shielding coating composition is 5 to 20.
It is preferably set to mass%.

The light-shielding coating composition of the present invention contains a general water-based coating composition as long as an insulating light-shielding film is formed on a display device using the composition so long as its electrical characteristics and display characteristics are not impaired. Various additives such as defoaming agents and dispersants used in the above may be added. Particularly, when ethanol is added, a good defoaming effect can be obtained.

The light-shielding coating composition is prepared by adding the above-mentioned aqueous dispersion of oxidized carbon and an aqueous solution of a water-soluble resin and, if necessary, an additive such as a defoaming agent, an ultrasonic dispersion method, a homogenizer method, a ball mill method, Mixing is carried out by a known and commonly used dispersion mixing method such as a mixer method, a sand mill method, a kneader method,
Prepare.

The insulating light-shielding film is formed by applying a light-shielding coating composition on a support and then drying it. The coating method includes spin coating method, pull-up coating method, air doctor coating method, blade coating method, rod coating method, knife coating method, squeeze coating method, impregnation coating method, reverse roll coating method, transfer coating method, gravure coating method, Kiss roll coating method, cast coating method, spray coating method, curtain coating method, calendar coating method, extrusion coating method, electrostatic coating method,
The method can be appropriately selected from known and commonly used methods such as the bar coat method. As the support, a plastic film, a glass plate or the like is generally used, but the support is not limited thereto.

[0025]

EXAMPLES The present invention will be described in more detail below with reference to examples. In the examples, “parts” and “%” represent “parts by mass” and “mass%”, respectively, unless otherwise specified.

(Example 1) Polyvinyl alcohol having a degree of polymerization of 1300 ("Exeval RS-271" manufactured by Kuraray Co., Ltd.
3 ") 8 parts of pure water 9 having a specific resistance value of 17.2 MΩ · cm
It was heated and dissolved in 2 parts to obtain an 8% aqueous solution of polyvinyl alcohol. 20 parts of 8% aqueous solution of polyvinyl alcohol, 4 parts of 20% carbon dioxide aqueous dispersion ("BONJET BLACK CW-1" manufactured by Orient Chemical Industry Co., Ltd.), and 1.2 parts of ethanol are mixed using an ultrasonic disperser. Then, a light-shielding coating composition was prepared. The light-shielding coating composition,
A general-purpose transparent polyester film was coated using a wire bar so that the film thickness after drying was 2 μm, and dried to obtain an insulating light-shielding film.

(Example 2) Polyvinyl alcohol having a degree of polymerization of 1300 ("Exeval RS-271" manufactured by Kuraray Co., Ltd.
3 ”), a polyvinyl alcohol having a degree of polymerization of 1700 (“ EXCEVAL RS-2617 ”manufactured by Kuraray Co., Ltd.)
An insulating light-shielding film was obtained in the same manner as in Example 1 except that was used.

(Example 3) Insulating light shielding was carried out in the same manner as in Example 1 except that the compounding amount of the 8% aqueous solution of polyvinyl alcohol prepared in Example 1 was 30 parts and the compounding amount of ethanol was 1.7 parts. A film was obtained.

(Example 4) Instead of 20 parts of 8% aqueous solution of polyvinyl alcohol prepared in Example 1, the polymerization degree was 1
300 polyvinyl alcohol (Kuraray's "Exceval RS-2113UC") has a specific resistance value of 17.2 MΩ.
An insulating light-shielding film was prepared in the same manner as in Example 1 except that 23 parts of an 8% aqueous solution of polyvinyl alcohol obtained by heating and dissolving in cm of pure water was used, and the compounding amount of ethanol was 1.4 parts. Obtained.

(Example 5) Instead of 20 parts of 8% aqueous solution of polyvinyl alcohol prepared in Example 1, the polymerization degree was 1
A polyvinyl acetal 20% aqueous solution of 500 (“S-REC KW-1” manufactured by Sekisui Chemical Co., Ltd.) has a specific resistance value of 17.
An insulating light-shielding film was prepared in the same manner as in Example 1 except that 24 parts of a 10% aqueous solution of polyvinyl acetal obtained by diluting with 2 MΩ · cm pure water was used and the compounding amount of ethanol was 1.4 parts. Obtained.

Comparative Example 1 Polyvinyl alcohol having a degree of polymerization of 400 (“Exeval RS-4104” manufactured by Kuraray Co., Ltd.
8 parts of UC ") was heated and dissolved in 92 parts of pure water having a specific resistance value of 17.2 MΩ · cm to obtain a polyvinyl alcohol 8% aqueous solution. 23 parts of 8% aqueous solution of polyvinyl alcohol, 20% carbon dioxide aqueous dispersion ("BONJET BLACK CW-" manufactured by Orient Chemical Industry Co., Ltd.
1 ”) and 1.4 parts of ethanol were mixed using an ultrasonic disperser to prepare a light-shielding coating composition. The light-shielding coating composition was applied to a general-purpose transparent polyester film using a wire bar so that the film thickness after drying was 2 μm, and dried to obtain an insulating light-shielding film.

(Comparative Example 2) Polyvinyl alcohol having a degree of polymerization of 1300 ("EXCEVAL RS-271" manufactured by Kuraray Co., Ltd.
3 ") 8 parts of pure water 9 having a specific resistance value of 17.2 MΩ · cm
By heating and dissolving in 2 parts, an 8% aqueous solution of polyvinyl alcohol was obtained. 15 parts of 8% aqueous solution of the above polyvinyl alcohol, 20% oxidized carbon water dispersion ("BONJET BLACK CW-1" manufactured by Orient Chemical Industry Co., Ltd.)
4 parts and 1 part of ethanol were dispersed and mixed in the same manner as in Comparative Example 1 to prepare a light-shielding coating composition, and an insulating light-shielding film was obtained in the same manner as in Comparative Example.

(Comparative Example 3) An insulating light-shielding film was prepared in the same manner as in Comparative Example 2 except that the compounding amount of the 8% aqueous solution of polyvinyl alcohol prepared in Comparative Example 2 was 35 parts and the compounding amount of ethanol was 2 parts. Obtained.

With respect to each of the insulating light-shielding films produced in Examples and Comparative Examples, the light transmittance and the surface electric resistance value in the wavelength region of 400 to 800 nm were measured. A "U-3410 type self-recording spectrophotometer" manufactured by Hitachi, Ltd. was used for measuring the light transmittance, and a "surface high resistance meter Hiresta" manufactured by Mitsubishi Petrochemical Co., Ltd. was used for measuring the surface electric resistance value. The surface electric resistance value is 500 V using a two-point probe.
The value averaged for 10 seconds under voltage application was used.

Table 1 shows the measurement results of the insulating light-shielding film produced in Examples and Comparative Examples. The value of light transmittance is
The upper limit of the light transmittance in the wavelength range of 400 to 800 nm is shown. In addition, the surface electric resistance value of "10 ¹³ ≤"
Means that the measurement limit under the above measurement conditions is exceeded.

[0036]

[Table 1]

From the results shown in Table 1, the insulating light-shielding film for a display device formed by using the aqueous light-shielding coating composition for a display device of the present invention has a high light-shielding property and a high surface electric resistance value.
That is, it is understood that it has a high insulating property at the same time.

[0038]

EFFECT OF THE INVENTION Oxidized carbon black having a degree of polymerization of 100.
A water-based light-shielding material for a display device according to the present invention, which contains 0 to 3000 of a water-soluble resin and water, and the content ratio of the oxidized carbon black and the water-soluble resin is in the range of 1: 2 to 1: 3 by mass ratio. Insulating light-shielding for display devices, which uses a coating composition and has the contradictory performance of large light-shielding property (blackness) and high surface electric resistance value, which could not be realized with conventional light-shielding paints using carbon black. A film can be formed.

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Claims (4)

[Claims] 1. An oxidized carbon black having a degree of polymerization of 100.
A display device containing 0 to 3000 of a water-soluble resin and water, wherein the content ratio of the oxidized carbon black and the water-soluble resin is in the range of 1: 2 to 1: 3 by mass ratio. Aqueous light-shielding coating composition. 2. The aqueous light-shielding coating composition for a display device according to claim 1, wherein the oxidized carbon black is one obtained by oxidizing carbon black with hypohalous acid or a salt thereof. 3. The water-based light-shielding coating composition for a display device according to claim 1, wherein the water-soluble resin is polyvinyl alcohol or a derivative thereof. 4. An oxidized carbon black having a degree of polymerization of 10
The water-soluble resin is contained in an amount of 0.002 to 3000, and the content ratio of the oxidized carbon black and the water-soluble resin is 1: 2 by mass.
An insulating light-shielding film for a display device, which is in the range of 1: 3.