Tin-containing indium oxides, a process for producing them, a coating solution using them and electrically conductive coatings formed of them

• US 20030030036A1
• Filed: 03/28/2002
• Published: 02/13/2003
• Est. Priority Date: 08/13/2001
• Status: Active Grant

• Current Assignee: Dowa Mining Company Limited
• Original Assignee: Dowa Mining Company Limited
• Inventors: Horikawa, Yoshichika, Eshima, Kohichiro, Moteki, Yoshio, Inamura, Tatsumi
• Granted Patent: US 6,908,574 B2
• Time in Patent Office: Days
• US Class Current: 252/500
• CPC Class Codes: C01G 19/00 Compounds of tin
• CPC Class Codes: C01P 2004/04 obtained by TEM, STEM, STM or AFM
• CPC Class Codes: C01P 2004/54 Particles characterised by their aspect ratio, i.e. the ratio of sizes in the longest to the shortest dimension
• CPC Class Codes: C01P 2006/12 Surface area
• CPC Class Codes: H01B 1/08 oxides

Abstract

To a hydrochloric acid solution containing In and Sn and which is held at 20° C., an alkali solution is added to adjust pH to 3; the temperature of the mixed solution is raised to 90° C. and the alkali solution is further added to adjust pH to 7.5. The resulting precipitate is recovered by filtration, dehydrated and dried to yield a Sn-containing In hydroxide; the hydroxide is put into a tubular furnace and fired in a nitrogen gas atmosphere containing water vapor and NH₃ gas at 600°C. for 2 hours to produce a Sn-containing In oxide in the form of plates having a major axis of 0.041 μm, a minor axis of 0.025 μm and a major-to-minor axis ratio of 1.64.

An ITO powder having a SnO₂ content of 2-20 wt % is provided by mixing acicular and granular ITO particles in proportions within the range of from 2:98 to 98:2. A coating solution prepared from this mixed ITO powder is applied to provide a transparent conductive film having a sheet resistance of 10 kΩ/□ or less, a light transmittance of at least 80%, and a haze value of no more than 2%.

Claims

1. A Sn-containing In oxide in the form of needles or plates that have a major axis of 0.2 μ

m or less and a minor axis of 0.1 μ

m or less.

2. The Sn-containing In oxide according to claim 1, wherein the major axis is 0.1 μ

m or less and the minor axis is 0.05 μ

m or less.

3. The Sn-containing In oxide according to claim 1 or 2, which has a major-to-minor axis ratio of 1.5-10.

4. A coating solution having the particles of the Sn-containing In oxide according to claim 1 or 2 dispersed in a solvent or a resin-containing solvent.

5. A coating solution having the particles of the Sn-containing In oxide according to claim 3 dispersed in a solvent or a resin-containing solvent.

6. An electrically conductive coating containing the particles of the Sn-containing In oxide according to claim 1 or 2 as a conductive material.

7. An electrically conductive coating containing the particles of the Sn-containing In oxide according to claim 3 as a conductive material.

8. A process for producing the Sn-containing In oxide according to claim 1 or 2 which comprises the steps of preparing an acidic aqueous solution containing Sn and In, adding an alkali to the acidic aqueous solution to effect preliminary neutralization, raising the temperature of the preliminarily neutralized aqueous solution, adding the alkali to the aqueous solution to fully neutralize it, and firing the resulting Sn-containing In hydroxide.

9. A process for producing the Sn-containing In oxide according to claim 3 which comprises the steps of preparing an acidic aqueous solution containing Sn and In, adding an alkali to the acidic aqueous solution to effect preliminary neutralization, raising the temperature of the preliminarily neutralized aqueous solution, adding the alkali to the aqueous solution to fully neutralize it, and firing the resulting Sn-containing In hydroxide.

10. The process according to claim 8, wherein the acid in said acidic aqueous solution is HCl, HNO₃ or H₂SO₄ and said alkali is NH₄OH, NaOH or KOH.

11. The process according to claim 8, wherein the preliminarily neutralized solution has a pH of 2-4 and the fully neutralized solution has a pH of 7-8.

12. The process according to claim 8, wherein said preliminary neutralization is performed at a solution'"'"'s temperature of 45°

C. or below and said full neutralization is performed at a solution'"'"'s temperature of 50°

C. or above.

13. The process according to claim 8, wherein said firing is performed in an inert gas containing water vapor or both water vapor and a reducing gas at 300-1,000°

C. while maintaining the shape anisotropy of the particles of said Sn-containing In hydroxide.

14. A transparent conductive film forming ITO powder comprising at least acicular ITO particles and granular ITO particles.

15. The transparent conductive film forming ITO powder according to claim 14, wherein the weight ratio of said acicular ITO particles to said granular ITO particles is in the range of from 2:

98 to 98;

2.

16. The transparent conductive film forming ITO powder according to claim 14 or 15, wherein said acicular ITO particles have a major axis of 0.5 μ

m or less, a minor axis of 0.1 μ

m or less, a major-to-minor axis ratio of 1.5-10 and a SnO₂ content of 2-20 wt % whereas said granular ITO particles have a grain size of 0.05 μ

m or less and a SnO₂ content of 2-20 wt %.

17. A transparent conductive film comprising an ITO powder comprising at least acicular ITO particles and granular ITO particles.

18. The transparent conductive film according to claim 17, wherein the weight ratio of said acicular ITO particles to said granular ITO particles is in the range of from 2:

98 to 98;

2.

19. The transparent conductive film according to claim 17 or 18, wherein said acicular ITO particles have a major axis of 0.5 μ

m or less, a minor axis of 0.1 μ

m or less, a major-to-minor axis ratio of 1.5-10 and a SnO₂ content of 2-20 wt % whereas said granular ITO particles have a grain size of 0.05 μ

m or less and a SnO₂ content of 2-20 wt %.

20. The transparent conductive film according to claim 17 or 18 which has a sheet resistance of 10 kΩ

/□

or less.

21. The transparent conductive film according to claim 19 which has a sheet resistance of 10 kΩ

/□

or less.

22. The transparent conductive film according to claim 17 or 18 which has a light transmittance of 80% or more and a haze value of 2% or less in haze measurement.

23. The transparent conductive film according to claim 19 which has a light transmittance of 80% or more and a haze value of 2% or less in haze measurement.

24. A process for forming the transparent conductive film of claim 17 or 18 which comprises the steps of mixing said acicular ITO particles with said granular ITO particles in a solvent, dispersing the mixed particles to form a slurry and applying the slurry to a transparent substrate.

25. A process for forming the transparent conductive film of claim 19 which comprises the steps of mixing said acicular ITO particles with said granular ITO particles in a solvent, dispersing the mixed particles to form a slurry and applying the slurry to a transparent substrate.