JPH08127860A - Treatment solution for forming transparent conductive film, production of transparent conductive film by using the treatment solution, and the resulting transparent conductive film - Google Patents

Abstract

PURPOSE: To produce a transparent conductive film capable of low temp. burning, used for electric field shielding for cathode ray tube(CRT), and having high electric conductivity. CONSTITUTION: A treatment solution for forming transparent conductive film, practically constituted of either or both of pulverized powders of tin-added indium oxide and antimony-added tin oxide, pulverized powder of rhenium trioxide, silicate type binder composed essentially of alkylsilicate partially hydrolyzed polymer, and organic solvent, is used. Burning is done at 100-450 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 producing a transparent conductive film for shielding an electric field generated from a cathode ray tube such as a display of an OA device or a cathode ray tube of a TV, and a transparent conductive film.

[0002]

2. Description of the Related Art In video game machines, personal computers, word processors, etc., the display screen is easy to see and does not cause visual fatigue.
T) It is required that there be no dust adhesion due to surface charging and no electric shock when touched. In addition to this, recently, there is a concern that a low-frequency electromagnetic wave generated from a CRT may adversely affect the human body, and a CRT in which such an electromagnetic wave does not leak outside is desired.

Electromagnetic waves are generated from the deflection coil and the flyback transformer, and as the TV becomes larger, an increasingly large electromagnetic wave tends to leak to the surroundings. Most of the magnetic field leakage can be prevented by changing the shape of the deflection coil. On the other hand, leakage of an electric field can be prevented by forming a conductive transparent film on the surface of the CRT front glass. This method is in principle the same as the measures taken in recent years to prevent static electricity. However, the conductivity of the conductive film in this case is required to be much higher than the conductivity of the conductive film formed for the antistatic purpose, and the surface resistance is about 10 ⁸ Ω / □ for the antistatic property. However, in order to prevent a leakage electric field, it is necessary to form a low resistance transparent film of at least 10 ⁶ Ω / □ or less, preferably 10 ² to 10 ³ Ω / □.

In forming such a transparent film, antimony-added tin oxide (ATO) or tin-added indium oxide (ITO) is used as a material, and in terms of process, 4
Film formation is required at a temperature of 50 ° C. or lower, preferably about 200 ° C. or lower. This is because the temperature condition needs to be lower than the temperature near the glass softening point, and in consideration of cost and yield, it is preferable to form the transparent conductive film on the CRT completed sphere after vacuum sealing the face panel. by.

In order to meet the above requirements, several methods such as a method of forming a film of ATO or ITO by a sputtering method or a vapor deposition method have been conventionally known, but as a method that can realize a low surface resistance at a lower cost, An average particle size of 1 to 10% by weight of tin contained in a polar solvent containing an alkyl silicate binder and N-methyl-2-pyrrolidone as main components 5
1 nm of tin-doped indium oxide (ITO) powder of 0 nm or less
An ink coating method using an electric field shielding treatment liquid dispersed in an amount of up to 15% by weight has been proposed (JP-A-6-23455).
No. 2). According to this method, the treatment liquid is treated with C
A surface resistance value of 10 ³ to 10 ⁶ Ω / □ can be obtained by applying the composition on the RT front glass, drying it, and baking it at a temperature of 200 ° C. or lower. This treatment liquid contains I as conductive fine powder.
Although TO is used as a main component, ATO or aluminum-added zinc oxide (AZO) can be partially substituted or substituted.

[0006]

The above-mentioned ink coating method is much simpler and has a lower manufacturing cost than transparent conductive film forming methods such as vacuum vapor deposition and sputtering, and is suitable as a CRT electric field shield. Is a very advantageous method. However, this method is disadvantageous in that the obtained surface resistance value is slightly inferior to the sputtering method, the vapor deposition method, and the like. When using the processing liquid, although the thickness can be also thickened them if 10 ³ Ω / □ pedestal low surface resistance, since when increasing the thickness cloudy film (haze) is arise unfavorably. Therefore, in order to enhance the electric field shielding effect without increasing the film thickness, it is desired to form a film having a resistivity as small as possible by the ink method.

The present invention has been made in view of such a conventional situation, and provides a method for producing a transparent conductive film which can be fired at a low temperature and which can form a film having high conductivity for an electric field shield of a CRT. It is a proposal.

[0008]

The gist of the present invention is to use ITO as a treatment liquid for forming a transparent conductive film in an ink coating method.
And one or more of ATO and rhenium trioxide fine powder (R
eO ₃ ) and an organic solvent, or a silicate binder mainly composed of one or more of ITO and ATO powder, a fine powder of rhenium trioxide, and an alkyl silicate partially hydrolyzed polymer. , And an organic solvent, which is substantially composed of
As a method for producing a transparent conductive film using the transparent conductive film forming treatment liquid, a coating liquid containing the transparent conductive film forming treatment liquid is applied to a substrate and then baked at a temperature of 100 ° C. or higher and 450 ° C. or lower. In addition, after applying a coating liquid containing the same treatment liquid to a substrate, a silicate-based overcoat liquid containing an alkyl silicate partially hydrolyzed polymer as a main component is applied and baked at a temperature of 100 ° C. or higher and 450 ° C. or lower. And a transparent conductive film obtained by such a method.

[0009]

In the treatment liquid of the present invention, a part of oxygen of ITO or ATO used as a main component of fine particles giving transparent conductivity may be replaced by fluorine, and in addition to ITO and ATO, AZO, Fluorine-added indium oxide, fluorine-added tin oxide, fluorine-added zinc oxide, or the like may be partially substituted.

In the present invention, the rhenium trioxide fine powder is added in addition to the above transparent conductive fine particles because rhenium trioxide has a specific resistance of 2 to 2 more than that of ITO or ATO.
This is because it is four orders of magnitude smaller, and by mixing rhenium trioxide in addition to ITO and ATO, the conductivity of the film remarkably increases. Rhenium trioxide fine powder, the conductivity is greatly improved in the size of the sub-micron size usually obtained, in order to further maintain the transparency as a film, the particle size of rhenium trioxide is preferably small, Average particle size 50
ReO of a size sufficiently smaller than the visible light wavelength of nm or less
_{When 3} fine particles are used, even if the crystal itself is not transparent, visible light is hardly scattered, and transparency and haze characteristics are greatly improved.

The partially hydrolyzed alkyl silicate polymer is a form in which water and an acid catalyst are added to orthoalkyl silicate to allow hydrolysis and dehydration polycondensation to proceed to some extent, or hydrolysis to a tetramer to a pentamer is already carried out. It is possible to use a commercially available alkyl silicate solution which has been subjected to polycondensation and which has been further hydrolyzed and dehydrated and polycondensed. In this case, the alkyl group is preferably a lower alkyl group such as methyl and ethyl. As the polycondensation proceeds, the solution viscosity increases and finally solidifies. Therefore, the degree of polycondensation of the alkyl silicate is used within the range of the viscosity at which the solution can be applied to the substrate.

Such an alkyl silicate partially hydrolyzed polymer becomes a hard silicate because the polycondensation reaction is almost completed at the time of baking and heating after coating the treatment liquid. It is possible to add silica fine particles such as colloidal silica to the binder solution containing the partially hydrolyzed polymer of alkyl silicate. Further, in order to adjust the refractive index and reinforce the strength, it is possible to replace a part of Si in the polysiloxane with Ti, Zr or Al. The treatment liquid for forming a transparent conductive film can be used without including the silicate-based binder containing the partially hydrolyzed alkyl silicate polymer as a main component, but it becomes poorly compatible with the substrate glass and is used as a coating liquid component. A treatment liquid containing a silicate-based binder is preferable because it requires some ingenuity.

As a coating method of the treatment liquid, a spin coating method is generally used, but any method such as a spray coating method or a dip coating method can be used as long as the treatment liquid can be applied flatly and thinly.

In the present invention, the firing temperature after coating the treatment liquid is limited to a temperature of 100 ° C. to 450 ° C. for the following reason. The treatment liquid of the present invention can form a film having a sufficiently low resistance even at a low temperature of 200 ° C. or lower, but if the baking temperature is as high as possible, the film tends to be dense and the resistance value tends to decrease. However, when the firing temperature exceeds 450 ° C, ReO
₃ particles tend to decompose into Re ₂ O ₇ and the resistance increases,
In addition, since the deficient oxygen in the ITO is replenished and the resistance value of the ITO itself increases, the resistance of the film increases and the haze also increases. On the contrary, if the baking temperature is lower than 100 ° C., the polycondensation reaction often remains unfinished, and the organic solvent adsorbed on the particles and left remains to form an extremely fragile film. For this reason, in the present invention, the firing temperature after coating the treatment liquid is limited to 100 ° C or higher and 450 ° C or lower.
However, it is not preferable that the temperature exceeds 200 ° C. in heating after completion of CRT.

The transparent conductive film by the treatment liquid of the present invention is used in a two-layer structure in which a silicate-based overcoat glass is covered on the transparent conductive film in order to reinforce the film strength and impart a low reflection effect. Is also possible. This two-layer film can be formed by applying the treatment liquid and drying, then applying the silicate solution containing the above-mentioned alkyl silicate partially hydrolyzed polymer as the main component, and then baking. The reason why silicate is used as an overcoat is that it has excellent strength and weather resistance, high transparency and low haze, and C
That is, it can be fired at a low temperature suitable for RT. The low reflection effect is due to destructive interference between the reflected waves of the first layer and the reflected waves of the second layer. Such a two-layer transparent conductive film using the treatment liquid and the silicate solution can supply a low-cost and high-value-added CRT having an electric field shielding effect and a low reflection effect of an easily visible screen.

Further, such a transparent conductive film is a CRT.
Not only the front glass but also a window covering measuring instruments, an observation window of an electron microscope, a transparent container such as an IC or an LSI for shielding an external electromagnetic field can be formed as a substrate.

The organic solvent contained in the treatment liquid for forming a transparent conductive film or the overcoat liquid of the present invention has an appropriate boiling point not higher than the baking temperature and can disperse conductive particles or silica fine particles efficiently. Preferred examples include ethanol, isopropyl alcohol, n-butanol, dimethylformamide, dimethylacetamide, methyl cellosolve, N-methyl-2-pentanone (DAA), acetone, tetrahydroxyfuran (THF) and the like. As the solvent in the treatment liquid, a solvent other than the above may be appropriately used so as to give an appropriate viscosity and surface tension according to the method of coating on the substrate glass.

[0018]

【Example】

 Example 1 ITO ultrafine powder (average particle size 20 nm, Sumitomo Metal Mining Co., Ltd.
15g, ReO _ThreeUltra fine powder (average particle size 35nm, housing
Made by Tomo Metal Mining Co., Ltd.) 15g, NMP 20g, DAA
Mix 50g and use zirconia balls with a diameter of 5mm
For 72 hours in a ball mill and mix with ITO and ReO_ThreeDispersion of
100 g of liquid was prepared. The average degree of polymerization is 4-5
Ethyl silicate 40 (Tama Chemical Industry Co., Ltd.
3 g, ethanol 34 g, 5% hydrochloric acid aqueous solution 8 g,
50 g of ethyl silicate solution prepared with 5 g of distilled water,
Well mixed with 1100 g of ethanol and ITO, Re
O_ThreeAnd 1250 g of a mixed dispersion of silicate and
Was. Rotate 15 g of this solution at 150 rpm 200 ×
Bee on 200 x 3 mm soda lime plate glass substrate
The solution was dropped from the mosquito, shaken for 3 minutes and then stopped rotating.
This is put in an electric furnace at 200 ° C and baked for 30 minutes to form a baked film.
Got

Example 2 The mixing ratio of ReO ₃ was 5% by weight in the total solid content, and the mixing ratio of binder silicate was 10% by weight in the total solid content.
%, And a single layer film was prepared under the same conditions as in Example 1 except that the firing temperature was 250 ° C.

Example 3 The mixing ratio of ReO ₃ was 10% by weight in the total solid content, and the mixing ratio of binder silicate was 1 by weight in the total solid content.
A single-layer film was produced under the same conditions as in Example 1 except that the content was 0%.

Example 4 The mixing ratio of ReO ₃ was 30% by weight in total solids, and the mixing ratio of binder silicate was 1 by weight in total solids.
A single layer film was produced under the same conditions as in Example 1 except that the baking temperature was 0% and the firing temperature was 420 ° C.

Example 5 The mixing ratio of ReO ₃ was 70% by weight in the total solid content, and the mixing ratio of binder silicate was 5% by weight in the total solid content.
A single layer film was prepared under the same conditions as in Example 1 except that the percentage was changed to%.

Example 6 The mixing ratio of ReO ₃ was 85% by weight in the total solid content, and the mixing ratio of binder silicate was 5% by weight in the total solid content.
%, And a single layer film was prepared under the same conditions as in Example 1 except that the firing temperature was 150 ° C.

Example 7 15 g of a solution containing ITO, ReO ₃ and SiO ₂ prepared under the same conditions as in Example 3 was dropped on a plate glass rotating at 150 rpm and shaken off for 3 minutes, followed by ethyl silicate 40 (Tama). Chemical Industry Co., Ltd.) 3 g, ethanol 34 g, 5% hydrochloric acid aqueous solution 8 g, 15 g of ethyl silicate solution 50 g prepared with distilled water 5 g was added dropwise.
After shaking for a minute, the rotation was stopped. This was placed in an electric furnace at 120 ° C. and baked for 30 minutes to obtain a baked film.

Example 8 A fired film was prepared under the same conditions as in Example 1 except that the substrate was a 15-inch face panel for CRT.

Example 9 15 g of ITO ultrafine powder (average particle size 20 nm, manufactured by Sumitomo Metal Mining Co., Ltd.), 15 g of ReO ₃ ultrafine powder (average particle size 35 nm, manufactured by Sumitomo Metal Mining Co., Ltd.), 30 g of NMP, diacetone alcohol 40 g and ethanol 50 g are mixed,
A zirconia ball having a diameter of 5 mm was used for ball mill mixing for 240 hours, and 1350 g of ethanol was mixed therewith to prepare 1500 g of a mixed dispersion solution of ITO and ReO ₃ . Rotate 15 g of this solution at 150 rpm 200 ×
After dropping on a 200 × 3 mm soda lime plate glass substrate from a beaker and shaking for 3 minutes as it is, 3 g of ethyl silicate 40 (manufactured by Tama Chemical Industry Co., Ltd.), 34 g of ethanol, 8 g of 5% hydrochloric acid aqueous solution, 5 g of distilled water 15 g of 50 g of the ethyl silicate solution prepared in step 1 was dropped,
After shaking for a minute, the rotation was stopped. This was placed in an electric furnace at 120 ° C. and baked for 30 minutes to obtain a baked film.

Example 10 Instead of ITO ultrafine powder, ATO ultrafine powder (average particle size 14n
m, except for using Sumitomo Metal Mining Co., Ltd.) to prepare a single layer film of ATO over ReO ₃ over SiO ₂ under the same conditions as in Example 1.

Example 11 A single layer film of ATO-ReO ₃ -SiO ₂ was prepared under the same conditions as in Example 10 except that the film-forming substrate was replaced with a plate glass and a 15-inch CRT face panel glass was used.

Example 12 ITO ultrafine powder (average particle size 20 nm, Sumitomo Metal Mining Co., Ltd.) and ATO ultrafine powder (average particle size 20 nm, Sumitomo Metal Mining Co., Ltd.) were combined at a weight ratio of 1: 1. 15 g
A fired film was produced under the same conditions as in Example 1 except for the above.

Comparative Example 1 15 g of ITO ultrafine powder (average particle size 20 nm, manufactured by Sumitomo Metal Mining Co., Ltd.), NMP 20 g, diacetone alcohol 6
Ball dispersion was mixed for 5 hours with 5 g of ITO dispersion 100.
g was produced. 4.2 g of ethyl silicate 40 (manufactured by Tama Chemical Industry Co., Ltd.), 48 g of ethanol, 5%
An aqueous solution of hydrochloric acid (11 g), an ethyl silicate solution (70 g) prepared with distilled water (6.8 g) and ethanol (630 g) were mixed to prepare a mixed dispersion (800 g) of ITO and silicate. Rotate 15 g of this solution at 150 rpm 200 ×
The solution was dropped from a beaker on a 200 × 3 mm soda lime-based plate glass substrate, shaken for 3 minutes and then stopped rotating.
This was put in an electric furnace at 200 ° C. and baked for 30 minutes to obtain a baked film.

Comparative Example 2 A single layer film was obtained under the same conditions as in Example 4 except that the baking temperature of the film was 500 ° C.

Comparative Example 3 A single layer film was obtained under the same conditions as in Example 9 except that the baking temperature of the film was 500 ° C.

Comparative Example 4 In Example 10, A was mixed with the ReO ₃ fine powder without mixing.
A single layer film of TO-SiO ₂ was prepared.

Comparative Example 5 A single layer film was obtained under the same conditions as in Example 10 except that the baking temperature of the film was 500 ° C.

Table 1 shows the measurement results of the surface resistance value, haze value and transmittance of the films obtained in Examples 1 to 12 and Comparative Examples 1 to 6 above. The surface resistance of the film was measured using a surface resistance meter MCP-T200 manufactured by Mitsubishi Petrochemical Co., Ltd. Moreover, the haze value and the transmittance were measured using a haze meter HR-200 manufactured by Murakami Color Research Laboratory.

As is clear from the results shown in Table 1, when ReO ₃ was added in addition to the transparent conductive particles, it was about 10%.
A low surface resistance on the order of ³ Ω / □ is obtained. Further, it can be seen that the firing temperature of 200 ° C. or lower, which is suitable for forming a film on a CRT finished sphere, is sufficient. On the other hand, for those containing no ReO ₃ and those having a firing temperature of higher than 450 ° C., sufficient conductivity was not obtained.

[0037]

[Table 1]

[0038]

As described above, according to the present invention,
Since a surface resistance value lower than that of a transparent conductive film using a conventional treatment liquid for electric field shielding is obtained and baking at a low temperature is possible, a highly conductive film for electric field shielding of a CRT can be produced at low cost. It has an excellent effect that it can.

Claims (6)

[Claims] 1. A treatment liquid for forming a transparent conductive film, which is substantially composed of at least one of tin-doped indium oxide and antimony-doped tin oxide fine powder, rhenium trioxide fine powder and an organic solvent. 2. One or more of tin-added indium oxide and antimony-added tin oxide fine powder, rhenium trioxide fine powder, a silicate-based binder containing an alkyl silicate partially hydrolyzed polymer as a main component, and an organic solvent. A treatment liquid for forming a transparent conductive film, which is substantially composed of: 3. A transparent conductive film characterized by being baked at a temperature of 100 ° C. or higher and 450 ° C. or lower after applying a coating liquid containing the treatment liquid for forming a transparent conductive film according to claim 1 or 2 to a substrate. Manufacturing method. 4. A coating liquid containing the treatment liquid for forming a transparent conductive film according to claim 1 or 2 is applied to a substrate, and then a silicate-based overcoat liquid containing an alkyl silicate partially hydrolyzed polymer as a main component is applied. A method for producing a transparent conductive film, which comprises firing at a temperature of 100 ° C. or higher and 450 ° C. or lower. 5. A transparent conductive film obtained by the manufacturing method according to claim 3. 6. A method for manufacturing a transparent conductive film, which is obtained by the manufacturing direction according to claim 4.