JP2948927B2 - Conductive paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention forms a coating film on a substrate and uses it as a heating element for preventing icing or defogging of electrodes such as liquid crystal display elements and optical semiconductors, and window glasses of aircraft and automobiles. The present invention relates to a conductive paint suitable for:

[0002]

2. Description of the Related Art The above-mentioned conductive paint is usually prepared by mixing a conductive metal oxide powder and a resin binder with a solvent. Conventional paints of this type include, for example,
Japanese Patent Application Laid-Open No. 2-4761 discloses a method in which a vinyl chloride resin having an ester bond is used as a resin binder, and fine powder of conductive tin oxide or conductive indium oxide is dispersed in a coating material. JP-A-63-66267 discloses an electroconductive fine powder dispersed in a form of secondary aggregate having a particle size of 0.2 to 0.6 μm.

[0003] Such a conductive paint is used in the above-mentioned fields by forming a coating film on the surface of a substrate by a method such as vacuum deposition, spray, CVD, bar coating, and screen printing. Among them, screen printing has the advantages that an etching process is unnecessary and expensive equipment is not required because a conductive paint can be applied to a substrate in a pattern to form a coating film. An attractive way.

However, when a conventional conductive paint is used for screen printing, clogging of the screen tends to occur, resulting in poor printability, poor adhesion of the obtained coating film to the substrate, and extremely high surface resistance. And so on, and the advantages of screen printing could not be fully utilized.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, makes use of the features of screen printing, hardly causes clogging of a screen, has high adhesion of a coating film to a substrate, and has a high coating ability. It is an object of the present invention to provide a conductive paint having a low surface resistance of a film and having well-balanced properties as a whole.

[0006]

The present inventors have conducted various studies on the composition of the conductive paint in order to achieve the above object.
The specific surface area of the metal oxide powder contained in the conductive paint, the weight ratio of the metal oxide powder contained in the paint, and the mixing ratio of the solvent to the resin binder, etc., are suitable for screen printing and the obtained coating. The inventors have found that the properties of the film are greatly affected, and have completed the present invention.

That is, as a means for solving the above-mentioned problems, the present invention provides a metal oxide powder of 30 to 70% by weight,
The metal oxide powder contains a resin binder and 2 to 4 parts by weight of a solvent with respect to 1 part by weight of the resin binder, and has a specific surface area of 25 to 150 m ² / g. A conductive paint is provided.

[0008]

The present invention will be described in more detail.

The metal oxide powder used in the present invention includes a conductive metal oxide powder itself, a powder obtained by adding an inorganic compound or element to a conductive metal oxide, or a mixed powder thereof. For example,
Powder added Sb, P, F and the SnO _2, Cd in ZnO, Gd, powder added and SnO _2, In, In
₂ O ₃ —SnO ₂ powder (hereinafter referred to as ITO) and the like. Among these, ITO is preferred because it has high conductivity, has good affinity for resins and organic solvents, has excellent coatability, and is easy to obtain a uniform and stable conductive coating film having good conductivity and transparency.

In the present invention, the specific surface area of the metal oxide powder is adjusted to 25 to 150 m ² / g, preferably 50 to 130 m ² / g. When the specific surface area is less than 25 m ² / g, the haze value of the coating film increases, and when the specific surface area exceeds 150 m ² / g, the powder agglomerates, it is difficult to uniformly disperse, and the transparency and the like of the coating film decrease. . The specific surface area referred to in the present invention is a value measured by the BET method.

The metal oxide powder thus prepared is contained in the coating material in an amount of 30 to 70% by weight, preferably 40 to 60% by weight. Metal oxide powder in paint 3
When the content is less than 0% by weight, the conductivity of the obtained coating film is deteriorated. It is considered that the distance between the metal oxide particles in the coating film was too large. Conversely, if it exceeds 70% by weight, the adhesion to the substrate will be poor and the transparency will also be reduced. This is presumably because the amount of the resin binder is relatively reduced to deteriorate the adhesion, and because the particles themselves are not transparent, visible light is scattered and the transparency is reduced.

In the present invention, various organic polymers can be used as the resin binder. Considering the adaptability to screen printing, and the properties of the obtained coating film, a polymer having high affinity with the metal oxide powder, excellent dispersion and stable dispersion can be obtained, and having high transparency,
For example, polyesters, polyurethanes, acrylic polymers and the like, or a mixture of these polymers are preferable.

Of these, polyesters synthesized from glycols and dibasic acids are preferred.

As the glycol, aliphatic glycol,
For example, ethylene glycol, propylene glycol,
1,4-butanediol, 1,5-pentanediol,
1,6-hexanediol, diethylene glycol, neopentyl glycol and the like; alicyclic glycols such as 1,4-cyclohexane dimethanol, tricyclodecane dimethylol and the like; and aromatic glycols such as bisphenol A ethylene oxide or propylene oxide addition Products, ethylene oxide or propylene oxide adducts of bisphenol S, and the like, and combinations thereof. Among them, it is preferable to use a combination of ethylene glycol, neopentyl glycol, 1,4-butanediol, tricyclodecane dimethylol, and an adduct of bisphenol S with ethylene oxide or propylene oxide.

The dibasic acids include aromatic dibasic acids such as terephthalic acid, isophthalic acid, orthophthalic acid,
2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, etc .; alicyclic dibasic acids, such as hydrogenated terephthalic acid; and aliphatic dibasic acids, such as succinic acid, glutaric acid, adipic acid, pimerin Acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, α
-Ω-octadecanedicarboxylic acid, dimer acid, and the like, and combinations thereof. Especially, it is preferable to add terephthalic acid and / or isophthalic acid. Also, lower alkyl ester compounds of these dibasic acids can be used.

In the present invention, the above-mentioned glycols and / or dibasic acids may be polymerized alone or in combination of two or more, or the obtained polyesters may be used alone or in combination of two or more. Depending on the purpose, a small amount of a trivalent or higher polyol or polycarboxylic acid may be copolymerized.

By adjusting the copolymer composition ratio of the resin binder, the glass transition point (Tg) can be changed, and the solubility in a solvent and the flexibility of the resin can be adjusted. Generally, it is preferable to adjust the glass transition point to be about 40 to about 100 ° C. When the Tg is lowered, the solubility in the solvent is improved, but the obtained coating film becomes flexible, and when the Tg is increased, the reverse is true.

In the present invention, hydrocarbons, carboxylic esters, phenols, ethers, carbonyl compounds such as aldehydes and ketones, amines, and various other organic solvents are used alone or in combination. can do.

The amount of the solvent used is in the range of 2 to 4 parts by weight per 1 part by weight of the resin binder. That is, 4
When used in a large amount exceeding the weight part, the adhesion of the coating film to the substrate and the strength of the coating film itself decrease, and when it is less than 2 parts by weight, the conductivity, transparency and the like decrease. The amount used depends on the type of metal oxide powder, resin binder and solvent,
More preferably, it is in the range of 2.5 to 3.5 parts by weight.

In addition, a dispersant, a stabilizer, a weathering agent, an ozone-resistant agent, an ultraviolet absorber and the like can be added to the conductive paint of the present invention according to the purpose.

[0021]

Next, an embodiment will be described.

Examples 1 to 3 First, the effect of the mixing ratio of the solvent to the resin binder in the conductive paint component was examined.

A conductive paint was prepared by adding a metal oxide powder having a constant specific surface area so as to have a constant weight ratio in the paint, and changing the mixing ratio of the solvent to the resin binder in various manners, and actually screen printing.

That is, using an alumina ball mill, an ITO powder having a specific surface area of 100 m ² / g (F-IT
O: Dowa Chemical Co., Ltd.) and a polyester resin as a resin binder (Chemit K-1294: Toray Industries, Inc.)
) And isophorone, a ketone, as a solvent at a mixing ratio shown in Table 1 for about 3 hours and dispersed to prepare transparent conductive paints of Examples 1 to 3. These conductive paints are
Using a 5-mesh polyester screen, screen printing was performed on a glass plate, and the state of clogging of the screen was observed. As a result, those which did not cause clogging even after printing 10 times or more were evaluated as ○, and those which became clogged after 4 to 10 times and became difficult to print were shown as Table 1.

Next, the printed glass plate was dried at 110 ° C. for about 1 hour, and the characteristics of the obtained coating film were measured by the methods described below.

The adhesion of the coating film was determined by rubbing the surface of the coating film after drying with a pencil having a pointed hardness H, and observing the state of scratches remaining on the coating film. Observation results, ○ indicates that no scratches remain on the surface,
In Table 1, "△" indicates a state in which a part of the wound remains, and "x" indicates a state in which the part is damaged after rubbing.

The surface resistance was measured using a surface resistance meter (manufactured by Mitsubishi Yuka Co., Ltd.) according to the method described in JIS K6911. The total light transmittance and haze value of the coating film were measured using a haze computer (Suga Test). JI Co., Ltd.)
The measurement was performed by the method described in SK7105, and all the results are shown in Table 1.

Comparative Examples 1-2 For comparison with the conductive paints prepared in Examples 1-3,
A transparent conductive coating material in which the mixing ratio of the solvent to the resin binder was further changed was prepared using the same raw materials and methods as those used in Examples 1 to 3, and screen printing was performed. Observed the printing state, the characteristics of the obtained coating film in the same manner as in the examples,
It was measured. Table 1 shows the results.

[0029]

[Table 1] Examples 4 to 5 Next, the influence of the weight ratio of the metal oxide powder contained in the paint was examined.

The conductive paint was prepared using the same raw materials and method as in Examples 1 to 3, except that the weight ratio of the solvent to the resin binder was 3.2 and the weight ratio of the metal oxide powder contained in the paint was changed. Compounded and screen-printed using the obtained paint, the characteristics were observed and measured. Table 2 shows the results.

Comparative Examples 3 and 4 In the same manner as in Examples 4 and 5, the weight ratio of the metal oxide contained in the conductive paint was further changed, and the effect was observed and measured. Table 2 shows the results.

[0032]

[Table 2] Examples 6 to 8 Further, the influence of the specific surface area of the metal oxide powder prepared in the coating material was examined.

The weight ratio of the solvent to the resin binder was 3.2, the weight ratio of the metal oxide powder contained in the paint was 50% by weight, and the specific surface area of the metal oxide powder was variously changed. Prepare a conductive paint in the same manner as 1-3, screen-print using the obtained paint,
The characteristics were observed and measured. Table 3 shows the results.

Comparative Examples 5 to 6 In the same manner as in Examples 6 to 8, the specific surface area of the metal oxide contained in the conductive paint was further changed, and the effect was observed and measured. Table 3 shows the results.

[0035]

[Table 3]

[0036]

According to the conductive coating material of the present invention, it is possible to form a coating film which is strong, has excellent adhesion to a substrate, has a high total light transmittance, and has a low surface resistance value and a low haze value. In particular, since clogging hardly occurs, it is suitable for screen printing, and an excellent coating film can be economically obtained by utilizing its advantages.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Norio Noda 1-1-1, Sonoyama, Otsu, Shiga Prefecture Toray Shiga Works (72) Inventor Yoko Furuta 9-1, Oecho, Minato-ku, Nagoya-shi, Aichi Prefecture Toray Industries, Inc. Nagoya Office (72) Inventor Akio Harada 2-7-19-1 Emission West, Joto-ku, Osaka, Osaka Prefecture Daiken Chemical Industry Co., Ltd. (72) Kunikazu Enohara, Emission West 2, Joto-ku, Osaka, Osaka No.7-19, Daiken Chemical Industry Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) C09D 5/24 C09D 11/02

Claims (1)

(57) [Claims] 1. A resin composition comprising 30 to 70% by weight of a metal oxide powder, a resin binder, and 2 to 4 parts by weight of a solvent with respect to 1 part by weight of the resin binder. 25 to 150 m ² /
g. A conductive paint which is in the range of g.