Light-transmitting, thermal-radiation reflecting filter

• US 3,949,259 A
• Filed: 08/09/1974
• Issued: 04/06/1976
• Est. Priority Date: 08/17/1973
• Status: Expired due to Term

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Jost, Rudiger, Kostlin, Heiner
• Primary Examiner(s): Newsome, John H.
• Application Number:
  US05/496,143
• Time in Patent Office: 606 Days
• Field of Search: 117/33.3, 117/124 B, 117/124 A, 350/1, 350/288, 350/311, 313/112, 427/165, 427/166, 427/168, 427/337, 427/343, 427/377, 428/432, 428/410
• US Class Current: 313/112
• CPC Class Codes: G02B 5/208 for use with infrared or ultraviolet radiation, e.g. for separating visible light from infrared and/or ultraviolet radiation
• CPC Class Codes: H01J 61/40 by light filters; by coloured coatings in or on the envelope

Abstract

A light-transmitting, thermal-radiation reflecting filter which comprises a transparent support coated with indium oxide which is doped with more than 7 atomic percent of tin, calculated with respect to the number of indium atoms, has a free-electron density between 10²¹ and 3 times 10²¹ per cm³ and a plasma wavelength of less than 1.2μm. The filter can be manufactured so as to have a stress-free support by heating a support, which is coated in known manner with tin-doped indium oxide, at a temperature between 300°C and the softening temperature of the support material in a gas having an oxygen partial pressure of less than 10.sup.^-7 atmosphere.

Claims

1. In a light-transmitting, thermal-radiation reflecting filter of the type comprising a light-transmitting support which is coated with tin-doped indium oxide, the improvement wherein the indium oxide contains more than 7 atomic per cent of tin, calculated with respect to the number of indium atoms, has a free-electron density between 10²¹ and 3 times 10²¹ per cm³ and a plasma wavelength of less than 1.2 μ

m.

2. The filter as claimed in claim 1, wherein the indium oxide contains between 7 atomic percent and 20 atomic per cent of tin, calculated with respect to the number of indium atoms.

8. An electric lamp provided with a filter as claimed in claim 1.

9. An electric lamp provided with a filter as claimed in claim 2.

3. A method of manufacturing a light-transmitting, heat-radiation reflecting filter comprising coating a light-transmitting support with indium oxide doped with more than 7 atomic per cent of tin, calculated with respect to the number of indium atoms, heating the coated support in a gas containing an oxygen partial pressure of less than 10⁷ atmosphere and at a temperature between 300°

C and the softening temperature of the support, whereby a heat filter having a plasma wavelength of less than 1.2 μ

m and a free-electron density between 10²¹ and 3 times 10²¹ per cm³ on the support is obtained.

4. The method as claimed in claim 3, wherein the gas contains CO, H₂ or CO and H₂ having a partial pressure of from 5 torr to 50 torr per component.

5. The method as claimed in claim 3, wherein the gas has an oxygen partial pressure between 10^-7 atmosphere and the equilibrium pressure of indium-oxide.

6. The method as claimed in claim 5, wherein the gas contains CO and CO₂ or H₂ and H₂ O.

7. The method as claimed in claim 3 wherein the gas has a temperature between 380°

C and 500°

C.

10. The method as claimed in claim 4, wherein the gas has a temperature between 380°

C and 500°

C.

11. The method as claimed in claim 5, wherein the gas has a temperature between 380°

C and 500°

C.