JPH10134638A - Transparent conductive film, method for manufacturing the same, substrate with transparent conductive film, and transparent touch panel using the same - Google Patents

Abstract

(57) Abstract: The present invention relates to a transparent conductive film and a substrate with a transparent conductive film obtained by firing a metal compound, and relates to a transparent conductive film and a substrate with a transparent conductive film which are high in resistance and excellent in reliability. It is an object of the present invention to provide a transparent touch panel with excellent visibility and low power consumption without using complicated processes. SOLUTION: On a glass substrate 11, a composition solution for forming a transparent conductive film comprising at least an indium compound, a tin compound, a silicon compound and a solvent is applied to form a coating film 12, which is dried and fired. Then, a transparent conductive film 13 having a thickness of less than 30 nm is obtained by thermal decomposition of an indium compound, a tin compound and a silicon compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent conductive film composed of a conductive metal compound obtained by firing a metal compound, a method for producing the same, a substrate with a transparent conductive film, and a transparent touch panel using the same. .

[0002]

2. Description of the Related Art With the recent spread of portable information terminals and the like, the demand for (analog type) transparent touch panels capable of handwriting input has been increasing. According to the principle shown in FIG. 3, a voltage is applied to both ends of the transparent electrodes 1 and 2 which are uniform over the entire surface to form a potential distribution on the electrode surface, and the voltage when the two electrodes come into contact is detected. This is a mechanism for calculating the input position.

[0003] In the case of a portable device, in order to arrange a transparent touch panel on a liquid crystal screen without a backlight, a device having a higher total light transmittance is required. Further, in order to reduce the power consumption of the device, a transparent conductive film having a higher resistance than now is required.In addition, since the resistance of the film becomes higher, there is an advantage that a detection shift of an input position is reduced. There is a demand for a high-resistance transparent conductive film. In addition, because it is often exposed to high temperature and high humidity environment,
Further durability is also required.

As a transparent electrode of such a transparent touch panel, a transparent conductive material such as indium oxide / tin oxide (hereinafter, referred to as ITO) or tin oxide / antimony oxide (hereinafter, referred to as ATO) is formed on a glass substrate. Those having a film are widely used. The manufacturing process is evaporation,
A so-called thin film process such as a sputtering method and a CVD method has been mainly used.

[0005]

However, these methods have complicated manufacturing steps and a large-scale apparatus, so that the manufacturing cost is high. In addition, the manufacturing conditions were severe and were not suitable for mass production.

In order to solve the above-mentioned problems, the present invention provides a substrate with a transparent conductive film having high total light transmittance, high resistance, and little change in transmittance and resistance in a high-temperature and high-humidity environment. It is an object of the present invention to provide a transparent touch panel with excellent visibility and low power consumption, while providing the same at low cost without using a complicated process.

[0007]

In order to solve the above-mentioned problems, a transparent conductive film according to the present invention is characterized in that it contains indium oxide and tin oxide as main components and contains silica. According to this configuration, a transparent conductive film having high total light transmittance, high resistance, and excellent reliability can be obtained.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention contains indium oxide and tin oxide as main components and contains silica. By including silica, the transparent conductive film becomes denser, and a highly reliable transparent conductive film having a small change in resistance in a high-temperature and high-humidity environment is obtained. Further, the sheet resistance can be increased.

According to a second aspect of the present invention, the transparent conductive film is formed on a glass substrate to a thickness of less than 30 nm, has a sheet resistance of 1 to 20 kΩ / □, and has a total light transmittance. Is 90% or more. Film thickness is 30n
m, the reflection of light due to the difference in the refractive index between the glass substrate and the transparent conductive film becomes very small,
Light absorbed by the film itself is reduced, resulting in a substrate with a transparent conductive film having a high total light transmittance. Further, sheet resistance can be increased by making the film thinner.

According to a third aspect of the present invention, the substrate with a transparent conductive film is used as a lower panel. Thus, a transparent touch panel that is bright, consumes little power, and has excellent reliability can be realized.

According to a fourth aspect of the present invention, a composition for forming a transparent conductive film comprising at least an indium compound, a tin compound, a silicon compound and a solvent is applied on a glass substrate,
This is a method for producing a transparent conductive film, characterized by firing after drying. As a result, thermal decomposition of the metal compound and deposition of the oxide proceed simultaneously, so that an oxide film having good film quality is formed on the substrate. Silicon becomes silica and is in a state of being mixed with indium oxide and tin oxide. The transparent conductive film thus obtained has high resistance, excellent reliability with little environmental change.

In the method for producing a transparent conductive film according to the present invention, the proportion of the silicon compound to the indium compound is not more than 10 parts by weight of silicon with respect to 100 parts by weight of indium in terms of the weight of indium and silicon. Desirably.

Preferably, the mixing ratio of the tin compound to the indium compound is 5 to 20 parts by weight of tin with respect to 100 parts by weight of indium in terms of the weight of indium and tin.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. (Embodiment 1) FIG. 1 is a schematic sectional view showing an embodiment of a substrate with a transparent conductive film of the present invention. Glass substrate 11
A transparent conductive film 13 mainly containing an indium compound and a tin compound and containing silica is formed thereon with a thickness of less than 30 nm.

Hereinafter, a method for manufacturing a substrate with a transparent conductive film according to the present invention will be described. First, as shown in FIG. 1 (a), a composition for forming a transparent conductive film composed of at least an indium compound, a tin compound, a silicon compound and a solvent is applied on a cleaned glass substrate 11 to form a coating film 12. . Next, as shown in FIG. 1 (b), the coating film 12 is dried and baked to form a transparent conductive film 13 having a thickness of less than 30 nm by thermal decomposition of an indium compound, a tin compound, and a silicon compound.

Most glass such as borosilicate glass and soda glass can be used as the glass substrate 11, but inexpensive soda glass is often used as a substrate with a transparent conductive film for a transparent touch panel. In the case of using soda glass, since the eluted sodium component adversely affects the characteristics of the transparent conductive film, it is preferable to use a soda glass coated with silica to prevent sodium elution. The thickness of the glass substrate 11 can be any thickness, but is preferably about 1 to 2 mm from the viewpoint of strength, weight reduction, and price.

As the indium compound and the tin compound,
Chloride, bromide, fluoride, iodide, nitrate, sulfate, etc., which are inorganic compounds, or organic acid salts, which are organic compounds containing indium or tin in the structure, organic complexes,
Alkoxides and the like can be used. As the solvent,
What is necessary is just to dissolve the indium compound and the tin compound used. Examples thereof include alcohols such as ethanol and butanol, ketones such as acetone and methyl ethyl ketone, ethers such as ethoxyethanol, acetates such as ethyl acetate, and aromatic hydrocarbons such as xylene and toluene. These solvents are used alone or as a mixture.

The silicon compound is soluble in the above-mentioned solvent, and includes monomers such as silanol, tetraethoxysilane, methyltriethoxysilane and dimethyldiethoxysilane represented by the following general formula, and dimers and tetramers of these compounds. Alternatively, an oligomer or the like, or a hydrolysis product or a condensate of the above compounds can be used.

[0019]

Embedded image

The method for applying the composition for forming a transparent conductive film includes a spin coating method, a dipping method, a roll coating method, and a spraying method. In either method, the thickness of the transparent conductive film after firing is controlled to be less than 30 nm by controlling the concentration of the solution and the amount of application.

The firing temperature may be selected within a range not lower than the temperature at which the indium compound, tin compound and silicon compound are sufficiently thermally decomposed to grow oxide crystals, and the glass substrate is not softened. For example, in the case of soda glass coated with silica, the temperature is preferably 400 to 550 ° C.

In the substrate with a transparent conductive film obtained as described above, since the thickness of the transparent conductive film 13 is less than 30 nm, a high total light transmittance and a high sheet resistance can be obtained. More preferably, the thickness of the transparent conductive film 13 should be 10 to 25 nm.

Since the transparent conductive film 13 contains silica, the transparent conductive film 13 has high resistance, has little characteristic change with respect to high temperature and high humidity, and has excellent reliability. In particular, it is desirable that the compounding ratio of the silicon compound to the indium compound is 1 to 30 parts by weight of silicon with respect to 100 parts by weight of indium in terms of the weight of indium and silicon.

Further, the mixing ratio of the tin compound to the indium compound is calculated by converting the weight of indium and tin into
From 5 to 20 parts by weight of tin relative to 100 parts by weight of indium, it is desirable from the viewpoint of reliability.

At this time, the sheet resistance of the transparent conductive film is 1 k to
It is 20 kΩ / □, which is suitable as an analog input type transparent touch panel with low power consumption and little deviation in position detection.

(Embodiment 2) FIG. 2 is a sectional view schematically showing a part of an embodiment of the transparent touch panel of the present invention. The glass substrate 21 with the transparent conductive film 22 of the present invention is referred to as a lower panel 23. Further, a transparent conductive film 25 is provided on the plastic film 24 by a method such as vapor deposition or sputtering to form an upper panel 26, and these are overlapped via a spacer 27 so that the transparent conductive films 22 and 25 face each other.

As described above, the substrate with a transparent conductive film of the present invention has high total light transmittance and high sheet resistance. As a result, the transparent touch panel of the present invention is bright and has excellent visibility. In addition, there is an advantage that power consumption is small and displacement of position detection is small. Further, the characteristics are small and the reliability is excellent with respect to high temperature and high humidity.

[0028]

Next, the present invention will be described with reference to specific examples.

(Examples 1 to 4) 10 g of indium nitrate trihydrate was dissolved in 10 g of acetylacetone and then diluted with 180 g of ethanol. Add tin oxalate 0.4
1 g was dissolved while heating, and after cooling, tetraethoxysilane was added to obtain a composition for forming a transparent conductive film. The amount of tetraethoxysilane added was 0.24 g (Example 1), 0.74 g (Example 2), 1.27 g (Example 3), 2.66 g (Example 4), and the proportion of silicon was Si. / (In + Si) = 1, 3, 5, 10%. This composition liquid was applied to a soda glass substrate (thickness: 1.1 mm) having a surface coated with silica by spin coating (at 1,000 rpm). The substrate was left at room temperature for 10 minutes, dried at 70 ° C. for 10 minutes, and baked at 530 ° C. in the air for 30 minutes to form a film having a thickness of about 20 μm.
A transparent conductive film containing silica having ITO as a main component was formed.

Example 5 A solution containing a commercially available silicon alkoxide instead of tetraethoxysilane of Examples 1 to 4 (trade name: MOF P-5931, Tokyo Ohka Kogyo Co., Ltd.)
0) was used. The addition ratio of silicon is set to Si / (In + S
i) = 3%, and a transparent conductive film containing silica containing ITO as a main component was formed in the same manner as in Example 1.

Comparative Example 1 Indium nitrate trihydrate 10
g was dissolved in 10 g of acetylacetone and then diluted with 180 g of ethanol. 0.41 g of tin oxalate
Was dissolved while heating to obtain a composition liquid for forming a transparent conductive film. Under the same coating and baking conditions as in Examples 1 to 5, an ITO transparent conductive film having a thickness of about 20 nm was formed.

For the substrate with a transparent conductive film of the above embodiment, the total light transmittance and the sheet resistance were measured, and a humidity resistance test (60 ° C., 90% RH) was performed for 240 hours, and the change in the sheet resistance at that time was measured. It was measured. The results are summarized in (Table 1). The total light transmittance was measured using a haze meter (NDH-300A, manufactured by Nippon Denshoku Industries Co., Ltd.). A four-probe resistivity meter (Loresta, manufactured by Yuka Denshi Co., Ltd.) was used to measure the sheet resistance.

[0033]

[Table 1]

From Table 1, it can be seen that the sheet resistance of the ITO film of Comparative Example 1 increased by 60% after the moisture resistance test, but the ITO film containing silica of the present invention showed a very small change in the sheet resistance value. It turns out that it is small. As described above, by appropriately selecting the ratio containing silica, the moisture resistance can be greatly improved.

It should be noted that there is no difference in the total light transmittance between the substrates with the transparent conductive film of the example and the comparative example, and the inclusion of silica does not reduce the total light transmittance. Also,
The sheet resistance is 1 k to 20 k in each of the embodiments.
Ω / □.

Next, transparent touch panels were produced using the substrates with a transparent conductive film of the example and the comparative example, and they were compared.

(Examples 6 to 10) Each of the substrates with an ITO transparent conductive film containing silica prepared in Examples 1 to 5 was placed on a lower panel and placed on a 175 μm-thick PET film.
A transparent touch panel of 7 cm × 8 cm of an analog input type was manufactured by using an O film formed by sputtering as an upper panel.

Comparative Example 2 A transparent touch panel was manufactured in the same manner as in Example 6, except that the substrate with the ITO transparent conductive film manufactured in Comparative Example 1 was used for the lower panel.

The results of evaluating the transparent touch panels manufactured in Examples 6 to 10 and Comparative Example 2 are shown in Table 2.

[0040]

[Table 2]

In Table 2, the total light transmittance is a value of the entire transparent touch panel, that is, the combined value of the upper and lower panels. The power consumption is the power consumed when the same control circuit and software are used.
It is expressed as a ratio as 0%. It is clear from Table 2 that the transparent touch panel of the example consumes less power.

[0042]

As described above, according to the present invention, a composition for forming a transparent conductive film comprising an indium compound, a tin compound, a silicon compound and a solvent is applied on a glass substrate, dried,
By firing, a transparent conductive film containing indium oxide and tin oxide as main components and containing silica, which is high in resistance and excellent in reliability, is obtained.

Further, by using the glass substrate on which the transparent conductive film is formed as the lower panel, the visibility is excellent and the power consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing an embodiment of the present invention.

FIG. 2 is a sectional view schematically showing one embodiment of the present invention.

FIG. 3 is a conceptual diagram showing an input method of a transparent touch panel.

[Explanation of symbols]

 11, 21 Glass substrate 12 Coating 13, 22, 25 Transparent conductive film 23 Lower panel 24 Plastic film 26 Upper panel 27 Spacer

Claims (6)

[Claims] 1. A transparent conductive film comprising indium oxide and tin oxide as main components and silica. 2. The transparent conductive film according to claim 1, which is formed on a glass substrate to a thickness of less than 30 nm, has a sheet resistance of 1 to 20 kΩ / □ and a total light transmittance of 90.
% With transparent conductive film. 3. A transparent touch panel using the substrate with a transparent conductive film according to claim 2 as a lower panel. 4. A method for producing a transparent conductive film, comprising applying a composition for forming a transparent conductive film comprising at least an indium compound, a tin compound, a silicon compound and a solvent onto a glass substrate, drying and firing. Method. 5. The production of a transparent conductive film according to claim 4, wherein the compounding ratio of the silicon compound to the indium compound is 10 parts by weight or less of silicon with respect to 100 parts by weight of indium in terms of the weight of indium and silicon. Method. 6. The mixing ratio of the tin compound to the indium compound is calculated in terms of the weight of indium and tin,
The method for producing a transparent conductive film according to claim 4, wherein the amount of tin is 5 to 20 parts by weight with respect to 100 parts by weight of indium.