JP5562174B2 - Transparent conductive tin oxide powder, method for producing the same, and film composition using the same - Google Patents

Description

  The present invention relates to a transparent tin oxide powder having high safety and conductivity without containing harmful components such as antimony, a method for producing the same, and a dispersion and a film composition containing the tin oxide powder. .

  Conductive tin oxide powders are used in printers, copier-related charging rollers, photosensitive drums, toners, carriers, electrostatic brushes, etc., charge control materials, dust adhesion prevention display filters, electromagnetic shielding films, It is widely used for internal electrodes and transparent conductive films for infrared reflection films, dye-sensitized solar cells, liquid crystal displays and plasma displays.

  In the conventional conductive tin oxide powder market, antimony-doped tin oxide (ATO) containing antimony having excellent conductivity has been used, but antimony toxicity has become a problem in Europe, and antimony Instead of niobium, tin oxide doped with niobium (NbTO), fluorine doped tin oxide (FTO), and the like have been developed. As conductive metal oxide powders other than tin oxide, tin-doped indium oxide (ITO), zinc oxide-based aluminum-doped zinc oxide (AZO), and the like have been developed. However, ITO is concerned about the unusually high price of indium, which is the main raw material, and the depletion of raw materials, and NbTO, FTO, AZO, etc. have problems such as limited conductivity and limited use. There is a need for a conductive material that is inexpensive, has excellent conductivity, is harmless, and has a low environmental impact. Therefore, the present inventors paid attention to phosphorus-containing tin oxide (PTO) from the viewpoint of obtaining a highly safe tin oxide powder having high conductivity without containing antimony.

  The conventional PTO conductive powder has (1) a large volume resistance of powder compared to ATO and poor transparency and surface resistance when blended in a transparent resin film; (2) Storage period of powder When the length is long, the volume resistance of the powder increases due to oxidation; (3) the transparent conductive film is deteriorated by the catalytic activity of phosphorus; In order to solve these problems, phosphorous is adsorbed on the surface of tin oxide to suppress grain growth, and the volume resistance is reduced by firing in a nitrogen atmosphere (Patent Document 1). The surface of tin oxide particles is coated with an organic compound. A method for improving the stability over time of electrical conductivity (Patent Document 2), a method for suppressing the catalytic action of phosphorus by surface treatment with an acrylic ester to PTO powder and suppressing deterioration of the coating film or film by phosphorus (Patent Document 2) 3) etc. have been studied. However, the PTO conductive powder obtained by these methods has a volume resistance equivalent or inferior to that of ATO, and has excellent transparency and good surface resistance when blended in a transparent resin film. It wasn't.

JP 2006-172916 A JP 2006-202704 A JP 2009-018979 A

  Although ATO, which is widely used even today, has a small volume resistance, antimony is a toxic component, so its use is restricted from the viewpoint of safety and environment, and antimony-free conductive powder is required. . The present invention provides a tin oxide conductive powder having excellent conductivity without containing harmful components such as antimony and having a volume resistance superior to that of an antimony-containing tin oxide conductive powder at a low cost. It aims at obtaining the transparent conductive film which has the outstanding transparency and favorable surface resistance by mixing | blending.

As a result of examining PTO, the present inventors have produced tin hydroxide containing phosphorus, adsorbed a water-soluble polymer to the product, and then subjected to a firing treatment while controlling the specific atmosphere. The inventors have found that a conductive tin oxide powder having a specific surface area of 30 to 90 m ² / g and a volume resistance of 0.5 to 10 Ω · cm can be obtained, and the present invention has been completed.

As a mechanism for causing the tin oxide to exhibit conductivity, an oxygen defect is generated in the tin oxide particle SnO 2 _(2-x) by adding a dopant to the tin oxide particle, and transmission electrons move through the oxygen defect. It is known that electrical conductivity can be obtained. The degree of conductivity is determined by the effect of the type and amount of dopant added to the tin oxide particles and the amount of oxygen defects in the tin oxide particles SnO 2 _(2-x) . In the case of ATO, since the dopant effect of antimony is high, conductivity is exhibited even in the baking treatment in the atmosphere. In contrast, phosphorus has a weaker dopant effect than antimony element, and rather than penetrating into the inside of tin oxide, it stays near the grain boundaries and the surface of the grains, causing oxygen defects to form in the surface layer of tin oxide that has grown. In the case of PTO, good conductivity is not exhibited unless it is fired at a high temperature of 900 ° C. or higher where the oxygen partial pressure is low. However, firing at a high temperature promotes the growth of tin oxide grains, increases the reflectance of light by the particles, and is disadvantageous for transparent conductive film applications. Therefore, in the case where baking is performed while emphasizing transparency and suppressing the grain growth of tin oxide, it is necessary to generate oxygen defects by baking in an inert gas. However, no detailed examination has been made on a specific method for controlling the atmosphere of an inert gas.

In the firing treatment, the present inventors consider that if an organic substance other than an inert gas is present in the vicinity of tin oxide, oxygen is consumed for the oxidation of the organic substance, which contributes to the generation of oxygen defects in tin oxide. I found a phenomenon. That is, by adsorbing a water-soluble polymer as a reduction accelerator and then firing in an inert gas in order to generate oxygen defects, the atmosphere is controlled with a reduced flow rate of the inert gas. It has been found that the intended conductive powder can be obtained. Specifically, when washing the tin hydroxide containing phosphorus obtained by the hydrolysis reaction, after adsorbing the water-soluble polymer, filtering and drying, in the firing treatment step, an inert gas is used before the temperature rise. After the atmosphere is replaced, the inert gas is allowed to flow during cooling without flowing the inert gas while the temperature is raised to the target temperature and maintained at the target temperature. By not allowing an inert gas to flow during the firing process, the efficiency of the reducing gas that contributes to the development of conductivity generated from the added organic matter was increased. By applying these firing methods, a phosphorus-containing oxygen-deficient conductive tin oxide powder having a specific surface area of 30 to 90 m ² / g and a volume resistance of 0.5 to 10 Ω · cm can be obtained.

  The present invention is relatively easy to produce highly conductive conductive powder with excellent conductivity that can be used in various fields without using antimony that has toxic problems, and has high industrial advantages. There is.

Hereinafter, the phosphorus-containing oxygen-deficient conductive tin oxide powder of the present invention will be described in detail.
(Production method)
The conductive powder according to the present invention produces tin hydroxide in which 0.1 to 5% by weight of phosphorus is added to tin oxide, and is washed while adsorbing a water-soluble polymer to the product, while controlling the atmosphere. It can be manufactured by firing treatment. The firing treatment typically includes the steps of replacement of atmospheric air with an inert gas, temperature rise to the firing temperature, firing at the firing temperature, and cooling from the firing temperature to room temperature. During the firing treatment, an inert gas is allowed to flow in the atmospheric air replacement step before the temperature rise and the cooling step after the firing, but the inflow of the inert gas is stopped in the temperature rise step and the firing step that generate oxygen defects. To control the atmosphere. Phosphorus-containing oxygen-deficient conductive tin oxide powder having a specific surface area of 30 to 90 m ² / g and a volume resistance of 0.5 to 10 Ω · cm by firing at a firing temperature of 400 to 800 ° C. Is obtained.
(Hydrolysis reaction)
The phosphorus-containing tin hydroxide is obtained by a known hydrolysis method, and is obtained by dissolving a phosphorus compound in a tin salt or a stannate solution and simultaneously adding an alkali or an acid. At this time, the reaction temperature is preferably 50 to 90 ° C. and the pH is preferably 2 to 9.

  As the tin salt, for example, tin chloride, tin sulfate, tin nitrate or the like can be used. Moreover, as a stannate, sodium stannate, potassium stannate, etc. can be used, for example.

  Examples of the alkali include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, ammonia water, and ammonia gas. Examples of the acid include hydrochloric acid, sulfuric acid, nitric acid, acetic acid, and the like. .

  Examples of phosphorus compounds include halides such as phosphorus trichloride and phosphorus pentachloride, orthophosphoric acid, sodium hydrogen phosphate, trisodium phosphate, ammonium hydrogen phosphate, phosphorous acid, sodium dihydrogen phosphite, phosphorus phosphite Phosphoric acid such as trisodium acid, pyrophosphoric acid, hexametaphosphoric acid, triphosphoric acid, polyphosphoric acid, or a salt thereof can be used.

  It is preferable to add phosphorus in advance by dissolving it in a tin salt or a solution of stannate and forming a phosphorus product during the hydrolysis of tin. In the method of adding a phosphorus compound after producing tin hydroxide, grain growth tends to proceed in the firing treatment step, and transparency tends to decrease.

The addition amount of the phosphorus compound is 0.1 to 5% by weight, preferably 0.5 to 4% by weight as P with respect to SnO ₂ . If the amount of phosphorus added is less than 0.1% by weight, the effect of preventing the sintering of phosphorus will be reduced, and the transparency will deteriorate due to grain growth in the firing step. _{Since the 2} O ₅ layer is formed and the volatilization of oxygen is suppressed, the amount of oxygen defects is reduced.
(Addition of third element)
By adding a third element other than phosphorus to the hydrolysis reaction product, the conductive powder particles can be refined, and particles having a good particle size distribution can be obtained. The compound of the third element is preferably dissolved in a tin solution, an alkali or an acid during the hydrolysis reaction. As the third element, one or more of silicon, zirconium, and titanium can be added. Of these elements, silicon is more preferably used. The addition amount of silicon is 0.5 to 10% by weight, preferably 1.0 to 3% by weight as Si with respect to SnO ₂ . If the amount of silicon added is less than 0.5% by weight, the effect of suppressing particle growth is reduced, and a sufficiently fine conductive powder cannot be obtained. If it exceeds 5% by weight, a thick SiO ₂ layer is formed at the grain boundary or the particle surface. As a result, sufficient conductivity cannot be obtained.
(Addition of water-soluble polymer compound)
The method for producing a conductive powder of the present invention includes a washing step of phosphorus-containing tin hydroxide obtained by a hydrolysis reaction. Washing is performed by diluting the treated suspension with pure water, adding a water-soluble polymer compound to agglomerate, and then decanting to wash, thereby reducing the electrolyte concentration in the suspension and water-soluble. A method in which a polymer compound is adsorbed on an aggregate of tin hydroxide is preferred. After the washed product is filtered and dried, an optimum amount of oxygen is contained in the phosphorus-containing tin oxide particles SnO 2 _(2-x) by the reducing gas generated by decomposition of the adsorbed polymer compound in the next firing step. A defect is produced | generated and favorable electroconductivity can be expressed. Such a water-soluble polymer compound can be produced by a conventionally known method, and can also be obtained from the market.

Examples of the water-soluble polymer compound include a cationized water-soluble polymer and an anionized water-soluble polymer.
Examples of cationized water-soluble polymers include cationized starch such as Hymo Co., Ltd. Himax NC-10, PC-6500; cationized guar gum as Sanki Co., Ltd. Maypro Bond 9806; Amaragawa Chemical Industries Co., Ltd. Polymaron 351, 360, Polystron 311, 619, Arafix 251; As cationized polyacrylic acid ester, Hymo Lock MP-184, MP-284, MP-384 , MP-484, MP-584, MP-684, MP-784, MP-984, MP-173H, MP-373H, MP-373L, MP-473H, MP-405, MP-180, MP-380, MP -558, MS-882, MS-884, MX-0120, MX-0210, M -8170, MX-8130, MX-6170, MX-6144, MX-4173, MX-2100, MX-4054, MX-3310, MX-2050, E-305, E-315, E-195, E-395 E-775, E-755, E-555, E-950, E-513, E-515, E-510; As cationized vinylformamide, Hymolock ZP-700 of Hymo Co., Ltd .; Hymo Neo-600 from Hymo Co., Ltd .; Hymolock Q-101, Q-311, Q-501 (above trade names) from Hymo Co., Ltd. and the like as cationized polyamines.

  As an example of the anionized water-soluble polymer, anionized polyacrylamides include Hymo Lock SS-200H, SS-200, SS-300, SS-500, SS-100, SS-120, SS-130 of Hymo Co., Ltd. SS-140, AP-105, AP-107, AP-115, AP-120, V-330, V-320, V-310, OK-107, OK-307, OK-507, L-113, Neo -200; Examples of the anionized sodium polyacrylate include Hymo Lock SS-190 (trade name) from Hymo Co., Ltd.

  Further, these polymer compounds may be added immediately before, during or immediately after the firing step, instead of being added at the time of washing. For example, polyvinyl alcohol can also be used. Polyvinyl alcohol can be produced by a conventionally known method, and can also be obtained from the market. Examples of polyvinyl alcohol include Poval C-05GP, C-10GP, C-25GP, PA-10GP, PA-15GP from Shin-Etsu Chemical Co., Ltd .; PVA-217, PVA-224 from Kuraray Co., Ltd. Name).

The addition amount of these polymer compounds is preferably 0.02 to 0.5% by weight in terms of carbon based on the hydrolysis reaction product of tin. Small, no improvement in conductivity is observed, and when it is higher than 0.5% by weight, the optimum amount of oxygen defects cannot be obtained, so that the conductivity is lowered.
(Baking process)
As described above, the firing treatment typically includes the steps of replacing atmospheric air with an inert gas, raising the temperature to the firing temperature, firing at the firing temperature, and cooling from the firing temperature to room temperature. Firing needs to be performed in a non-oxidizing atmosphere.

Therefore, in the firing process, first, an inert gas is sufficiently blown before the temperature is raised to replace the air in the atmosphere with the inert gas. Next, by stopping the blowing of inert gas at the time of temperature rise and firing, it is a method of extending the retention time of the reducing gas so as not to let the reducing gas contributing to the expression of conductivity generated from the added organic matter escape. Firing is performed. When the firing process is completed and the cooling process is performed, an inert gas is flowed again to prevent air from entering. By controlling the amount of the inert gas by the above method, it is estimated that oxygen defects in the phosphorus-containing tin oxide particles SnO 2 _(2-x) can be made the optimum amount, and good conductivity can be obtained. .

  The temperature at the time of firing is preferably 500 to 700 ° C. When the temperature is lower than 500 ° C, the improvement in conductivity is not observed, and when it is higher than 700 ° C, sintering and grain growth occur, and the transparency may be lowered. There is.

An inert gas can be used to create a non-oxidizing atmosphere. As the inert gas, for example, nitrogen, helium, argon, carbon dioxide gas or the like can be used. By adjusting the amount of inert gas such as nitrogen gas and controlling the atmosphere to perform the firing treatment, tin oxide particles having stable conductivity can be obtained.
(Organic surface treatment)
When the phosphorus-containing oxygen-deficient conductive tin oxide powder of the present invention is dispersed in the resin, it is preferable to treat the surface of the conductive powder with an organic material in order to improve dispersion in the resin. In addition, by treating the surface with an organic substance, oxygen in the air, which is a factor that degrades volume resistance, is blocked, which contributes to stabilization of volume resistance over time. As the organic surface treatment method, a known method can be applied. For example, a tin oxide powder can be coated with an organic compound such as a coupling agent or a polyhydric alcohol. The type of coupling agent used for the surface treatment can be appropriately selected according to the purpose of use of the conductive powder, but is selected from the group consisting of silane, titanate, zirconate, aluminate and zircoaluminate. More than one kind can be used. The addition amount of the coupling agent is preferably 0.05 to 10% by weight, more preferably 0.1 to 8% by weight. If the amount added is less than 0.05% by weight, the effect of improving the stability with time and dispersibility cannot be obtained. This will cause a decrease and further increase in cost. Further, the polyhydric alcohol used for the surface treatment can be appropriately selected similarly to the coupling agent, but one or more selected from trimethylolethane, trimethylolpropane, pentaerythritol, mannitol and sorbitol can be selected. . The addition amount of the polyhydric alcohol is preferably 0.05 to 20% by weight, more preferably 0.1 to 15% by weight, and if it is out of the range, it is not preferable for the same reason as the coupling agent.

As a surface treatment method using an organic substance, a known method can be applied. For example, a dry treatment method in a high-speed stirring mixer such as a Henschel mixer, or a suspension obtained by dispersing the tin oxide powder in an organic solvent or water. And a method of performing treatment by adding an organic substance to the solution. In the case of treating organic matter uniformly on the surface, the latter treatment is suitable, but in the case of an organic solvent system, distillation operation, pulverization, etc., in the case of an aqueous system, solid-liquid separation, drying, pulverization, etc. In view of ease of production and cost, a method using a high-speed stirring mixer such as a Henschel mixer is preferable.
(Inorganic surface treatment)
For the purpose of improving dispersibility, the surface of the phosphorus-containing oxygen-deficient conductive tin oxide powder of the present invention may be treated with an inorganic substance. As an inorganic substance which coat | covers the particle | grain surface, 1 type, or 2 or more types in aluminum, silicon, zirconium, titanium, phosphorus, etc. are mentioned. The addition amount of the inorganic substance is preferably 0.05 to 2% by weight, and if it is more than 2% by weight, the conductive performance is lowered.
(Membrane composition)
By incorporating the phosphorus-containing oxygen-deficient conductive tin oxide powder of the present invention into a paint, ink, emulsion, or fiber, a conductive paint, conductive ink, conductive emulsion, or conductive fiber can be produced. Also, a resin paint containing conductive tin oxide powder can be prepared using a sand grinder or the like, and applied to a base material to which conductivity or antistatic property is to be imparted, and used as a coating film. As the coating film component, a thermosetting resin or an ultraviolet curable resin is preferable. The concentration of the conductive tin oxide to be blended needs to be appropriately adjusted according to the intended conductive performance, but the preferable concentration range is 20 to 80% by weight with respect to the coating film component, and the more preferable concentration range is 30 to 75% by weight. If the amount of the conductive tin oxide powder to be blended is too small, the desired surface resistance cannot be obtained, and if it is too large, the strength of the coating film is lowered and the cost is further increased, which is not preferable.

The phosphorus-containing oxygen-deficient conductive tin oxide powder of the present invention is a transparent thin film having a content of 50 to 80% by weight and a film thickness of 2 μm with respect to the coating film component. A good conductive film having a resistance of 1 × 10 ⁷ to 1 × 10 ⁸ Ω / □ or less is obtained.

EXAMPLES Hereinafter, the present invention will be specifically described by way of examples. However, the following examples are merely shown for illustration, and the scope of the invention is not limited thereby.
[Example 1]
Preparation of tin hydrolysis reaction product: 1.0 liter of water was kept warm at 70 ° C. Separately prepared 1628.4 g of stannic chloride (SnCl ₄ .5H ₂ O 98 wt%) was dissolved in 1.5 liters of 12N hydrochloric acid, and 26.3 g of orthophosphoric acid was dissolved in 10N sodium hydroxide solution. The suspensions were added dropwise simultaneously over about 2 hours so as to maintain the pH of the suspension at 2-3. Thereafter, the mixture was kept stirring for 30 minutes.

  Washing step: The treated suspension was diluted with pure water, and 7.0 L of a 0.5 g / L aqueous solution of SS-120 manufactured by Anion Water-soluble Compound Hymo Co., Ltd. was added to cause aggregation. The amount added is equivalent to 0.5% by weight with respect to the hydrolyzed product. The aggregated slurry was decanted several times, washed and filtered.

Drying step: The obtained washed cake was dried at 110 ° C.
Firing treatment: 1.2 kg of the obtained dry powder was charged into an advantech Toyo batch type rotary kiln furnace having an internal volume of 15 L, and firing treatment was performed in the following atmospheric conditions a in each step to obtain a fired product.

Atmosphere condition a
Step A: Flow in nitrogen gas at a rate of 1 liter / min for 30 minutes.
Step B: The temperature is raised to 600 ° C. at a rate of 6.5 ° C./min. Nitrogen gas flow rate is 0 liter / min.

Step C: Hold at 600 ° C. for 60 minutes. Nitrogen gas flow rate is 0 liter / min.
Step D: Cool to room temperature at a rate of 5 ° C./min. Nitrogen gas flow rate is 1 liter / min.
Crushing step: 0.5% by weight of trimethylolethane as a grinding aid was added to the fired product and pulverized by an air flow method to obtain the desired conductive powder.
[Example 2]
In Example 1, it processed similarly to the case of the example except having made baking processing temperature into 400 degreeC, and obtained the electroconductive powder made into the objective.
[Example 3]
In Example 1, it processed similarly to the case of the example except having made baking process temperature 700 degreeC, and obtained the target electroconductive powder.
[Example 4]
In Example 1, it processed similarly to the case of the example except having made baking processing temperature into 800 degreeC, and obtained the target electroconductive powder.
[Example 5]
In Example 1, 7.0 L of a 0.5 g / L aqueous solution of MP-173H produced by Cationized Water-soluble Compound Hymo Co., Ltd. was added as the water-soluble polymer compound added in the washing step.
[Example 6]
In Example 1, instead of adding an anionized water-soluble compound Hymo Co., Ltd. SS-120 in the washing step, 0% of Shin-Etsu Chemical Co., Ltd. Poval C-05GP was added to the dried product before the baking treatment step. .5% by weight was added and the baking treatment was performed.
[Example 7]
In Example 1, the amount of orthophosphoric acid added at the stage of adjusting the tin hydrolysis reaction product was 78.9 g. This is (P is 3 wt% with respect to SnO ₂ )
[Example 8]
In Example 1, 1.0 wt% sodium silicate as Si was added to SnO ₂ in the 10N sodium hydroxide solution added in preparation of the tin hydrolysis reaction product.
[Comparative Example 1]
The treatment was performed in the same manner as in Example 1 except that air was constantly blown at 1 liter / min during the firing treatment to make the atmosphere in the air (atmosphere condition b).
[Comparative Example 2]
The treatment was performed in the same manner as in Example 1 except that nitrogen gas was constantly blown at 1 liter / min during the firing treatment (atmosphere condition c).

The processing conditions, powder and thin film properties are shown in Table 1. The volume resistance, specific surface area, light transmittance and surface resistance of the thin film were measured by the following methods.
(Measurement method of volume resistance)
In a state where the sample is pressure-molded at 230 kgf / cm ² (diameter 25.4 mm), a Keisei LCR meter AR-480D type is connected, and the resistance value is measured. The thickness of the sample at that time was measured, and the volume resistivity value was calculated.
(Measurement method of specific surface area)
The sample was degassed at 150 ° C. for 30 minutes in nitrogen, and then the specific surface area was measured by a BET 1-point method using Gemini 2360 manufactured by Micrometrics.
(Preparation of conductive coating)
A conductive powder was added to a mixed solution of xylene-toluene together with a transparent acrylic resin Acrydic A-168 (resin content: 50% by weight) made by Dainippon Paint, and a dispersion was prepared by dispersing the beads for 60 minutes using a paint shaker. . This dispersion was applied to a PET film using a doctor blade and air-dried for 1 hour to form a transparent coating film having a tin oxide content of 70% and a film thickness of 2 μm.
(Measurement of light transmittance)
About this thin film, the visible light transmittance | permeability was measured using the Suga Test Instruments direct reading haze computer spectrophotometer HGM-2DP type | mold. The results are shown in Table 1.
(Measurement method of surface resistance)
The surface resistance of a thin film having a tin oxide content of 70% by weight and a film thickness of 2 μm was measured using a surface resistance measuring device HP4339A manufactured by Yokogawa Hewlett-Packard Company.

* 1: For a, after nitrogen gas is introduced, nitrogen gas is stopped at the time of heating and firing, and nitrogen gas is introduced at 1 liter / minute during cooling. b flows in air at 1 liter / min. c always flows in nitrogen gas at 1 liter / min.

  From this result, according to the Example of this invention, what has a favorable volume resistance is obtained, and it turns out that the coating film which has a favorable light transmittance and surface resistance is obtained.

Claims (5)

It is obtained by producing a tin hydroxide containing phosphorus, adsorbing a water-soluble polymer to the product, and then firing it at a temperature of 400 to 800 ° C. in an inert gas atmosphere. A phosphorus-containing oxygen-deficient conductive tin oxide powder containing 0.1 to 5% by weight of phosphorus, having a specific surface area of 30 to 90 m ² / g and a volume resistance of 0.5 to 10 Ω · cm. After adsorbing 0.02 to 0.5% by weight of water-soluble polymer compound in terms of carbon to tin hydroxide containing phosphorus, it is in an inert gas atmosphere and does not allow inert gas to flow in. The method for producing a phosphorus-containing oxygen-deficient conductive tin oxide powder according to claim 1, wherein firing is performed at a temperature of 400 to 800 ° C while controlling the atmosphere.   As an atmospheric control method, an inert gas is allowed to flow when replacing atmospheric air before raising the temperature and cooling after firing, but inflow of inert gas when raising the temperature to the firing temperature after substitution and when firing after raising the temperature. The manufacturing method according to claim 2, wherein the process is stopped.   The phosphorus-containing oxygen-deficient conductive tin oxide powder according to claim 1, containing 0.1 to 5% by weight of silicon. In a transparent thin film having a conductive tin oxide powder content of 50 to 80% by weight and a film thickness of 2 μm with respect to the coating film component, the thin film has a visible light transmittance of 80% or more and a surface resistance of 1 × 10 ⁷ to × 10. ^The film composition in which the phosphorus-containing oxygen-deficient conductive tin oxide powder according to claim 1 is dispersed to ⁸ Ω / □.