JPH11227740A - Conductive plate having transparent conductive film, and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method requiring no complicated processes for conductive plates each having transparent conductive film while being low in surface resistance and to provide a conductive plate manufactured therewith. SOLUTION: The manufacturing method is for conductive plates each having transparent conductive film that is made up by heat treating a paint film formed by applying a paint containing tin-doped indium oxide powder in average particle size of 0.1 μm or finer and thermoplastic resin onto a base at a temperature higher than the softening point for thermoplastic resin. Furthermore, it is desirable that a paint film formed by applying a paint containing tin-doped indium oxide powder in average particle size of 0.1 μm or finer and thermoplastic resin onto a base made of polyethylene terephthalate is heat-treated at a temperature of 150 deg.C-210 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a conductive plate having a transparent conductive film and having excellent transparency and conductivity, and a conductive plate.

[0002]

2. Description of the Related Art JP-A-63-158709 discloses that
(A) an aqueous solution of a tin compound or an indium compound,
After maintaining the pH condition of 8 to 12 and gradually hydrolyzing the compound in the liquid to form a sol containing colloidal particles, the sol is dried and calcined to obtain a conductive fine powder. And (b) a conductive plate having on its surface a transparent conductive film formed from a conductive paint obtained by dispersing a binder resin in a solvent. The average particle size of the conductive fine powder in the paint is about 0.2 to 0.4 μm, and the drying temperature of the paint is 110 ° C. or the like.

[0003]

However, according to the above-mentioned method, it is not easy to obtain a conductive plate having a surface resistance Rs of 10 ² to 10 ⁴ Ω / b required for a transparent electrode, electromagnetic wave shielding and the like. Did not.

Accordingly, an object of the present invention is to provide a method of manufacturing a conductive plate having a transparent conductive film, which has a low surface resistance and does not require complicated steps, and to provide a conductive plate.

[0005]

The object of the present invention is to provide a coating film formed by applying a coating containing a tin-doped indium oxide fine powder having an average particle diameter of 0.1 μm or less and a thermoplastic resin on a substrate. The problem can be solved by performing heat treatment at a temperature equal to or higher than the softening point of the thermoplastic resin. The average particle size is 0.1μ
m or less of a tin-doped indium oxide fine powder and a thermoplastic resin, on a substrate made of polyethylene terephthalate.
The heat treatment is preferably performed at 210 ° C.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Tin-doped indium oxide fine powder refers to fine powder of tin-doped indium oxide (ITO) having an average particle diameter of 0.1 μm or less. When ITO fine powder having an average particle size of more than 0.1 μm is used, the light transmittance and haze of the transparent conductive film become insufficient, and the transparency tends to be reduced. The average particle size is 0.
ITO fine powder of 1 μm or less can be produced by a generally known method. Tin amount in the tin-doped indium oxide fine powder,
It is about 1 to 10% by weight Sn0 _2, the transparent conductive film exhibits high conductivity.

[0007] Since the thermoplastic resin has various softening points depending on its type and structure, it is preferable to appropriately select it according to the heat resistance of the substrate. As the thermoplastic resin, a generally known thermoplastic resin can be used, but a resin having a large volume shrinkage by cooling from a temperature higher than the softening point to room temperature and having a high softening point is preferable. As thermoplastic resins, alkyd resins, unsaturated polyesters,
Particularly preferred are polyester resins such as linear polyester and saturated polyester, acrylic resins such as methacrylic resin, and fluororesins. The polyester resin preferably has a molecular weight of 5,000 to 50,000 and a softening point of 100 to 180 ° C.

The mixing ratio of the fine ITO powder and the thermoplastic resin is 100% of the total amount of the fine ITO powder and the thermoplastic resin.
It is preferable that the ITO fine powder has a ratio of 70 to 85 parts by weight and the thermoplastic resin has a ratio of 30 to 15 parts by weight with respect to parts by weight. IT
When the amount of the O fine powder exceeds 85 parts by weight, the strength of the transparent conductive film is not sufficient, and when it is less than 70 parts by weight, the conductivity of the transparent conductive film is not sufficient.

[0009] The ITO fine powder and the thermoplastic resin are dispersed or dissolved in a solvent to form a paint. By applying the coating material on a substrate and subjecting the coating film to heat treatment, a conductive plate having a transparent conductive film formed on the substrate can be obtained. Examples of such a solvent include benzenes such as benzene and toluene, halogenated hydrocarbons such as methylene chloride, trichlene and propylene chloride, ketones such as methyl ethyl ketone (MEK) and cyclohexanone, and ethers such as cellosolve acetate, dioxane, and tetrahydrofuran. , An ester such as ethyl acetate, 21-nitropropane, a styrene monomer, or the like, or a mixed solvent of a mixture of two or more thereof. The solvent is appropriately selected depending on the type of the thermoplastic resin to be used. About 30% by weight or more of the solvent is at normal pressure (1
atm), the solvent having a boiling point of 100 to 200 ° C.
The paint is easily applied on the substrate at room temperature, and the thickness and the like of the transparent conductive film tend to be uniform.

In order to improve the dispersibility, stability, etc. of the paint or the film-forming properties of the transparent conductive film, generally used surfactants, dispersants and the like can be further added to the paint.

The coating material is applied on a substrate by a usual thin film forming method such as a spin coating method, a roll coating method, a spray method, a bar coating method, a dip method, a menis coat method, a gravure printing method and the like.

The substrate is preferably a transparent plate, and the substrate may be a plastic plate or film such as polyethylene terephthalate (PET), acrylic resin, polycarbonate, cellulose acetate (tack), or an inorganic glass plate. In particular, it is preferable that the substrate is made of PET or inorganic glass from the viewpoint of heat resistance. When the substrate is made of plastic such as PET, a conductive plate having excellent workability such as cutting can be obtained as compared with the case where the substrate is made of inorganic glass. PET is obtained by using terephthalic acid or a derivative thereof and ethylene glycol as main components and polycondensing them.

Next, the effect of heat-treating the coating film formed on the substrate at a high temperature will be described. Generally, the rate of volume increase of a thermoplastic resin increases at a temperature higher than the glass transition point (Tg), and decreases at a temperature higher than the softening point (Tm). For this reason, if the coating film is heat-treated at a high temperature as in the present invention, the reason that the solvent in the coating film is completely volatilized by the heat treatment, and the temperature is reduced from the heating temperature higher than the softening point of the thermoplastic resin to room temperature It is presumed that the contact between the ITO fine powders is strengthened and the conductivity of the transparent conductive film can be improved because the volume shrinkage is caused by doing so.

It is preferable to appropriately select the heat treatment temperature in consideration of the heat resistance of the substrate, the softening point of the thermoplastic resin, the boiling point of the solvent, and the like. For example, when the paint has a boiling point of 100 to 2 under normal pressure.
When the substrate contains PET and contains a compound of 00 ° C as a solvent, it is preferable to heat the coating film at a high temperature of 150 ° C to 210 ° C. If the temperature is lower than 150 ° C., the surface resistance of the conductive plate is hardly reduced, and if it exceeds 210 ° C.,
The thermal deformation of the PET substrate becomes too large, and the conductive plate becomes defective. If the substrate is made of PET, 1
Even if heated to 50 ° C. to 210 ° C., a conductive plate with almost no thermal deformation can be obtained. If the PET substrate is subjected to heat treatment by applying a slight external force, thermal deformation of the PET substrate can be prevented.

A preferred example of the conductive plate of the present invention will be described with reference to FIG. 2. A coating containing a tin-doped indium oxide fine powder having an average particle diameter of 0.1 μm or less and a thermoplastic resin is applied to the substrate 1. A conductive plate 10 obtained by a method for manufacturing a conductive plate, in which a coating film formed by applying the above is heated at a temperature not lower than the softening point of the thermoplastic resin, the tin-doped indium oxide fine powder 5 Is a conductive plate in which the thermoplastic resin, which is one component of the binder 3 that binds, is any one of a polyester resin, an acrylic resin, and a fluororesin.

[0016]

EXAMPLE A conductive plate 1 shown in FIG. 2 in which a PET film was used as a substrate 1 and a transparent conductive film 7 was adhered to one surface of the substrate 1 was used.
0 was made as follows. Then, the relationship between the heat treatment temperature of the coating film and the surface resistance value of the conductive plate 10 was examined. Method for producing conductive plate 10: dissolving linear saturated polyester resin (softening point: 155 ° C.) in a solvent, adding a dispersant thereto,
Further, a tin-doped indium oxide fine powder was added and dispersed to prepare a coating for forming the transparent conductive film 7. This paint is applied on a PET film by a bar coating method to form a coating film, and the coating film is applied at 100 ° C. to 2 ° C. for 10 minutes.
By heating at 00 ° C., the conductive plate 10 shown in FIG. 2 was obtained. Note that the thickness of the transparent conductive film 7 was 1 μm.

The composition of the paint is shown below. Tin-doped indium oxide fine powder: average particle size 0.08 μm
ITO fine powder, 24 parts by weight Thermoplastic resin: polyester resin, softening point 155 ° C
Solvent, cyclohexanone (boiling point, 155 ° C./1at)
m): MEK (boiling point, 79.6 ° C./1 atm) = 1:
1 mixed solvent, 70 parts by weight Dispersant: fluororesin-based dispersant, 1 part by weight

The average particle size of the ITO fine powder was measured at 20 ° C. by a dynamic light scattering method using a laser particle size analysis system (manufactured by Otsuka Electronics Co., Ltd.) to determine the translational diffusion coefficient. ,
It was calculated from the Einstein-Stokes equation (Einstein-Stokes equation). The softening point of the polyester resin was measured according to JIS K2531 (ring and ball method). The surface resistance Rs of the conductive plate 10 was measured at 20 ° C. using Resta (manufactured by Mitsubishi Chemical Corporation).

FIG. 1 shows the relationship between the measurement result of the surface resistance Rs of the conductive plate 10 measured as described above and the heat treatment temperature. As shown in FIG.
When the polyester resin having a softening point of 155 ° C. is used as the thermoplastic resin,
If heat treatment is performed at 0 ° C., about (2-3) × 10 ³ Ω / □
Conductive plate 10 (with a thickness of about 1 μm
Having a transparent conductive film 7).
When the heat treatment was performed at 0 ° C. or less, it was found that the surface resistance Rs of the conductive plate 10 exceeded 10 ⁴ Ω / □. That is,
It was found that the conductive plate 10 having a low surface resistance value Rs can be easily manufactured by subjecting the coating film to heat treatment at a high temperature of 160 ° C. to 200 ° C.

Next, the thickness of the transparent conductive film 7 and the conductive plate 1
The relationship between the surface resistance Rs of 0, the total light transmittance Tt, and the haze H was examined. As a sample for this, a conductive plate having a transparent conductive film 7 having a film thickness of 2 μm or 4 μm was prepared in the same manner as described above, except that the heat treatment temperature of the coating film was kept at 180 ° C. and the coating thickness of the coating material was changed. 10 was produced. The total light transmittance Tt and haze H of the conductive plate 10 were measured using a haze computer (manufactured by Suga Test Instruments Co., Ltd.). Table 1 shows the above measurement results.

[0021]

[Table 1]

If the heat treatment temperature of the coating film is 180 ° C.,
The surface resistance Rs of the conductive plate 10 having the transparent conductive film 7 having a thickness of 1 to 4 μm is 2 × 10 ³ Ω / □ or less, and
Table 1 shows that the conductive plate 10 is excellent in transparency. Further, the PET film was heated to 180 ° C. together with the coating film, but no warpage or the like was observed on the conductive plate 10.

[0023]

As described above, according to the present invention,
A conductive plate having a surface resistance of 10 ² to 10 ⁴ Ω / b and excellent transparency can be easily manufactured. Such a conductive plate is useful as an electroluminescent (EL) display, a liquid crystal display, a touch panel, a transparent electrode such as a solar cell, a window material for a hospital or the like, an electromagnetic wave shielding material for a front panel of a cathode ray tube, and the like. .

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a heat treatment temperature of a coating film and a surface resistance value of a conductive plate.

FIG. 2 is a cross-sectional view illustrating an example of a conductive plate.

[Explanation of symbols]

1. substrate, 3. binder, 5. fine ITO powder,
7. Transparent conductive film, 10 Conductive plate

Claims (4)

[Claims] 1. A coating film formed by applying a coating material containing tin-doped indium oxide fine powder having an average particle size of 0.1 μm or less and a thermoplastic resin on a substrate, and forming a coating film having a softening point of the thermoplastic resin. A method for producing a conductive plate having a transparent conductive film, characterized by performing a heat treatment at the above temperature. 2. The method for producing a conductive plate having a transparent conductive film according to claim 1, wherein the thermoplastic resin is any one of a polyester resin, an acrylic resin, and a fluororesin. 3. A coating film formed by applying a coating material containing fine particles of tin-doped indium oxide having an average particle size of 0.1 μm or less and a thermoplastic resin on a substrate made of polyethylene terephthalate to form a coating film having a thickness of 150 °. A method for producing a conductive plate having a transparent conductive film, wherein a heat treatment is performed at C to 210 ° C. 4. A conductive plate having a transparent conductive film manufactured by the method for manufacturing a conductive plate having a transparent conductive film according to claim 1.