Light-transmitting substrate provided with a light-absorbing coating, light absorbing coating as well as method of preparing a light-absorbing coating
View Patent ↗The present invention relates to a light-transmitting substrate ( 1 ) which is at least provided with a light-absorbing coating ( 3 ). The light-absorbing coating comprises stabilized pigments which are incorporated in a sol-gel matrix. The light absorbing coating comprises silica particles having a size between 5 and 100 nanometers and alumina particles having a size between 5 and 50 nanometers. The total volume concentration of pigments, silica and alumina particles in the light-absorbing coating is between 20 and 65 percent. The volume concentration of silica particles is between 5 and 40 percent and the volume concentration of alumina particles between 1 and 15 percent.
1. A light-transmitting substrate ( 1 ) which is at least provided with a light-absorbing coating ( 3 ), said light-absorbing coating comprising stabilized pigments which are incorporated in a sol-gel matrix, said light absorbing coating comprising silica particles having a size between 5 and 100 nanometers and alumina particles having a size between 5 and 50 nanometers, wherein the total volume concentration of pigments, silica and alumina particles in the light-absorbing coating is between 20 and 65 per cent, the volume concentration of silica particles between 5 and 40 per cent and the volume concentration of alumina particles between 1 and 15 per cent.
2. A light-transmitting substrate as claimed in claim 1 , wherein the size of the silica particles is between 10 and 30 nanometers.
3. A light-transmitting substrate as claimed in claim 1 , wherein the size of the alumina particles is between 10 and 30 nanometers.
4. A light-transmitting substrate as claimed in claim 1 , wherein the total volume concentration of pigments, silica and alumina particles in the light-absorbing coating is between 35 and 55 per cent.
5. A light-transmitting substrate as claimed in claim 1 , wherein the volume concentration of silica particles in the light-absorbing coating is between 10 and 20 per cent.
6. A light-transmitting substrate as claimed in claim 1 , wherein the volume concentration of alumina particles in the light-absorbing coating is between 5 and 10 per cent.
7. A light-transmitting substrate as claimed in claim 1 , wherein the silica particles are hydrophobic silica particles.
8. A light-absorbing coating comprising stabilized pigments which are incorporated in a sol-gel matrix, said light absorbing coating comprising silica particles having a size between 5 and 100 nanometers and alumina particles having a size between 5 and 50 nanometers, wherein the total volume concentration of pigments, silica and alumina particles in the light-absorbing coating is between 20 and 65 per cent, the volume concentration of silica particles between 5 and 40 per cent and the volume concentration of alumina particles between 1 and 15 per cent.
9. An electric lamp comprising a light-transmitting lamp vessel ( 1 ) that accommodates a light source ( 2 ), said lamp vessel comprising a light-transmitting substrate according to claim 1 .
10. A lamp vessel provided with a light-absorbing coating as claimed in claim 8 .
11. A method of preparing a light absorbing coating, said method at least comprising the steps of
preparing a pigment dispersion by mixing a pigment with an alcohol-comprising liquid
preparing a hydrolysis mixture comprising a silane wich is subjected to a sol-gel process, said hydrolysis mixture further comprising silica particles having a size between 5 and 100 nanometers and alumina particles having a size between 5 and 50 nanometers
mixing the pigment dispersion and the hydrolysis mixture in such a way that the total volume concentration of pigments, silica and alumina particles in the light-absorbing coating is between 20 and 65 per cent, the volume concentration of silica particles between 5 and 40 per cent and the volume concentration of alumina particles between 1 and 15 per cent.
12. A method as claimed in claim 11 , wherein the silica particles are incorporated in the hydrolysis mixture in the form of a silica sol.