Infrared absorbing thin film containing rutile-type titanium oxide crystal and method for producing the same

1. A method for producing an infrared absorbing thin film containing a rutile-type titanium oxide crystal doped with a transition metal ion selected from the group consisting of iron, zinc, manganese, copper, cobalt, vanadium, tungsten, and nickel, the method comprising:

a step (I) of dispersing or dissolving a complex (y) of an amino group-containing basic polymer (x) and a transition metal ion selected from the group consisting of iron, zinc, manganese, copper, cobalt, vanadium, tungsten, and nickel in an aqueous medium;

a step (II) of obtaining a composite having a polymer/titania layered structure in which the complex (y) of the amino group-containing basic polymer (x) and the transition metal ion is sandwiched between layers of titania with a distance of 1 to 3 nm, by mixing the aqueous dispersion or aqueous solution prepared in the step (I) with a water-soluble titanium compound (z) in the aqueous medium at a temperature of 50° C. or lower to cause a hydrolysis reaction;

a step (III) of calcining the composite having the layered structure in an air atmosphere at a temperature of 650° C. or higher to dope a surface of a titanium oxide crystal with the transition metal ion confined in the layered structure and simultaneously to cause growth into a rutile-type crystal phase;

a step (IV) of pulverizing the obtained crystal into a powder;

a step (V) of mixing the obtained powder with a sol of a metal alkoxide and/or a dispersion liquid of metal oxide nanoparticles to prepare a fluid liquid composition;

a step (VI) of coating a surface of a substrate with the obtained fluid liquid composition; and

a step (VII) of aging the coating film.

2. The method for producing an infrared absorbing thin film according to claim 1 , wherein the content of the transition metal ion with which the rutile-type titanium oxide crystal is doped is 0.1 to 20% by mass.

3. The method for producing an infrared absorbing thin film according to claim 1 , wherein, in the step (IV), the rutile-type titanium oxide crystal doped with the transition metal ion is pulverized into a powder having a particle size of 100 nm or less.

4. The method for producing an infrared absorbing thin film according to claim 1 , wherein the metal alkoxide used in the step (V) is an alkoxide of at least one metal selected from the group consisting of titanium, zirconium, and silicon.

5. The method for producing an infrared absorbing thin film according to claim 1 , wherein, in the step (V), the mixing ratio of the powder composed of the rutile-type titanium oxide crystal doped with the transition metal ion relative to the sol of a metal alkoxide and/or the dispersion liquid of metal oxide nanoparticles ((powder composed of rutile-type titanium oxide crystal)/(metal oxide formed of metal alkoxide and/or metal oxide in the form of nanoparticles)) is 95/5 to 98/2 on a mass basis.

6. The method for producing an infrared absorbing thin film according to claim 1 , wherein, in the step (V), the fluid liquid composition is prepared so as to have a solid content of 30 to 90% by mass.

7. An infrared absorbing thin film which is an infrared absorbing film obtained by the production method according to claim 1 ,

wherein the infrared absorbing film contains 90% or more by mass of the rutile-type titanium oxide crystal doped with the transition metal ion.

8. The infrared absorbing thin film according to claim 7 , wherein the infrared absorbing film absorbs infrared rays and then a surface of the infrared absorbing film generates heat.

9. The method for producing an infrared absorbing thin film according to claim 1 , wherein, in the step (V), the fluid liquid composition is prepared so as to have a solid content of 30 to 90% by mass.

10. The method for producing an infrared absorbing thin film according to claim 2 , wherein, in the step (V), the fluid liquid composition is prepared so as to have a solid content of 30 to 90% by mass.

11. The method for producing an infrared absorbing thin film according to claim 3 , wherein, in the step (V), the fluid liquid composition is prepared so as to have a solid content of 30 to 90% by mass.

12. The method for producing an infrared absorbing thin film according to claim 4 , wherein, in the step (V), the fluid liquid composition is prepared so as to have a solid content of 30 to 90% by mass.

13. The method for producing an infrared absorbing thin film according to claim 5 , wherein, in the step (V), the fluid liquid composition is prepared so as to have a solid content of 30 to 90% by mass.

14. An infrared absorbing thin film which is an infrared absorbing film obtained by the production method according to claim 1 ,

wherein the infrared absorbing film contains 90% or more by mass of the rutile-type titanium oxide crystal doped with the transition metal ion.

15. An infrared absorbing thin film which is an infrared absorbing film obtained by the production method according to claim 2 ,

wherein the infrared absorbing film contains 90% or more by mass of the rutile-type titanium oxide crystal doped with the transition metal ion.

16. An infrared absorbing thin film which is an infrared absorbing film obtained by the production method according to claim 3 ,

wherein the infrared absorbing film contains 90% or more by mass of the rutile-type titanium oxide crystal doped with the transition metal ion.

17. An infrared absorbing thin film which is an infrared absorbing film obtained by the production method according to claim 4 ,

wherein the infrared absorbing film contains 90% or more by mass of the rutile-type titanium oxide crystal doped with the transition metal ion.

18. An infrared absorbing thin film which is an infrared absorbing film obtained by the production method according to claim 5 ,

wherein the infrared absorbing film contains 90% or more by mass of the rutile-type titanium oxide crystal doped with the transition metal ion.

19. The infrared absorbing thin film according to claim 14 , wherein the infrared absorbing film absorbs infrared rays and then a surface of the infrared absorbing film generates heat.