MXPA01002199A

MXPA01002199A - Coated ultraviolet absorbing glass

Info

Publication number: MXPA01002199A
Application number: MXPA/A/2001/002199A
Authority: MX
Inventors: David G Grossman; Ronald L Stewart
Original assignee: Corning Incorporated; David G Grossman; Ronald L Stewart
Priority date: 1998-08-31
Filing date: 2001-02-28
Publication date: 2001-12-04

Abstract

This article is a glass substrate having a coating thereon. The coating strongly absorbs certain ultraviolet radiation. The preferred coating absorbs ultraviolet radiation at wavelengths ranging from 230 up to at least 280 nm while providing high transmission throughout a region of visible wavelengths. The preferred coating consists essentially of three layers, wherein the first layer adjacent the substrate is a mixture of SiO2 and TiO2;the second layer is TiO2 and the third layer farthest from the substrate is SiO2.

Description

COATED GLASS THAT ABSORBES ULTRAVIOLET RADIATION TECHNICAL FIELD This invention relates to a glass substrate having a coating thereon. The coating absorbs ultraviolet radiation considerably. In one embodiment, the glasses also absorb ultraviolet radiation.

BACKGROUND OF THE INVENTION When optical systems use high-power lamp light sources, there can be a significant radiation ratio of the light that is emitted in the ultraviolet region. When there are organic materials in the path of light, there will be a degradation of this material over time. Ultraviolet radiation also causes degradation and discoloration in paints, fabrics and plastics. Specifically, the electromagnetic energy in the ultraviolet spectrum (ie, between -100 and -400 nanometers), causes the paints and dye to fade, causes the rubber to crack, and the plastics to disintegrate over time. Therefore, a considerable ultraviolet radiation absorption by architectural glaze materials is beneficial.

The sun is not the only source of light that emits ultraviolet radiation. Several sources of artificial lighting such as Hg or Xe ARC and other discharge lamps emit ultraviolet radiation. Glasses that absorb ultraviolet radiation that block the full scale of ultraviolet emission from these sources can be used. However, as a result of absorption, with prolonged use, many glasses tend to solarize or darken over time, especially the absorption of the highest energy portion, of the shortest wavelength of the ultraviolet region. Pyrex-UV-Plus ™ ultraviolet-absorbing glass (available from Corning Incorporated) has applications such as distributed fiber optic lighting, Liquid Crystal Projection and other projection technologies. These lighting or projection systems use high intensity discharge light sources that contain radiated output in the ultraviolet spectrum. Pyrex-UV-Plus ™ glass has a very sharp band edge near 400 nm (ultraviolet-visible limit) that is useful for protecting organic components that degrade under ultraviolet creep, while providing maximum visible radiation transparency throughout the part visible spectrum (400-760 mm). However, some customer and internal tests have shown that certain metal halide lamps that exit the 250-280 nm scale can cause the absorbent Pyrex-UV-Plus ™ glass to darken in the visible spectrum. The use of glass prefilters that have cuts > 280 nm can prevent photo-obstruction of Pyrex-UV-Plus ™ glass. However, add two More glass surfaces would reduce visible transmission. Most Pyrex-UV-Plus ™ glass applications actually use antireflective coatings applied to glass surfaces to improve visible lumen output. The patent of E.U.A. jointly assigned, co-pending ,925,468, by Stewart, entitled "Solarization Resistant Glass and UV Radiation Blocker", filed April 1, 1997, and which is incorporated herein by reference, discloses ultraviolet-absorbing glass combined with a solarization-resistant glass article for provide a substantially complete UV spectrum blocking filter. Although these glasses provide a substantial improvement in glasses that absorb ultraviolet radiation, the need for improved systems continues. Accordingly, the object of the present invention is to provide an improved UV radiation blocking glass.

BRIEF DESCRIPTION OF THE INVENTION It has been found that the object of the invention can be achieved by the use of certain heat-reflective or anti-reflective heat-reflective coatings that absorb radiation when applied to a glass surface. Briefly, the invention relates to a glass substrate having a multilayer coating thereon. The coating absorbs ultraviolet radiation at wavelengths which vary from -230 to -300 nm while providing high transmission in a whole region of visible wavelengths. Preferably, the coating consists essentially of three layers, wherein the first layer adjacent to the substrate is a mixture of S0O2 and TIO2, the second layer is TIO2 and the third layer furthest from the substrate is SiO2. The coatings are preferably applied by a sol-gel immersion method. Titanium oxide is an ultraviolet radiation absorber that absorbs the photo-darkening wavelengths to provide protection for Pyrex-UV-Plus ™ glass and other UV absorbing glasses. Solarization tests were carried out on coated and uncoated glasses using a 1000-watt Hg-Xe lamp, and the transmission was compared at 500 nm before and after several hours of exposure. A sample with a three-layer sol-gel dip coating consisting of T 2 O 2 and SiO 2 was tested together with one having an antireflective coating of MgF 2 deposited thereon, both against a Pyrex-UV-Plus ™ glass. coated. The data indicate that the coating containing TiO2 absorbed the ultraviolet radiation to decrease the photo-darkening by a factor of 10 (using the loss of transmission at 500 nm). Other embodiments of the coating that must improve the photo-darkening resistance of the glass can be manufactured by including other ultraviolet radiation absorbers such as ZnO, Ce 2, VO 2, Ta 2 O 2 or Nb 2 5.

PREFERRED MODALITY OF THE INVENTION A preferred embodiment of this invention is a glass substrate having a multilayer coating thereon where the coating absorbs ultraviolet radiation at wavelengths ranging from -230 A-300 nm while providing high transmission throughout a region of visible wavelengths. The coating consists essentially of three layers, wherein the first layer adjacent to the substrate is a mixture of S02 and TiO2, the second layer is a mixed layer rich in TiO2, and the third layer furthest from the substrate is SIO2. The first coating layer consists essentially of 25 to 75 weight percent SiO 2 and 25 to 75 weight percent TiO 2. In a more preferred embodiment, the first coating layer consists essentially of 50 weight percent SiO2 and 50 weight percent TiO2. The first layer can also be essentially pure SiO2 or essentially pure Ti02. Although the preferred method of coating application is by the sol-gel immersion method, other methods such as PVD or CVD can also be employed. The layers of the coating have a thickness sufficient to absorb ultraviolet radiation at wavelengths ranging from -230 to -300 nm while providing high transmission over a whole region of visible wavelengths. In general, the coating has a thickness that varies from 1500 to 3500 Angstroms. In general, the first layer has a thickness that varies from 300 to 1200 Angstroms, the second layer has a thickness that varies from 300 to 1200 Angstroms, and the third layer has a thickness that varies from 300 to 1200 Angstroms. Generally, the glass substrate is capable of absorbing ultraviolet radiation at wavelengths in the 4-400 nm region, while providing high transmission throughout the visible region. More specifically, this glass transmits wavelengths in the visible and near infrared regions, while absorbing UV wavelengths in the region 4 to 400 nm. A particularly useful example of said ultraviolet radiation blocking glass is the non-photochromic glass R2O-B2? 3-S0? 2 (without photo-darkening under exposed solar air mass) of the U.S. patent. No. 5,322,819 (which is incorporated herein by reference), which contains a crystalline halide-cadmium halide or precipitated crystal phase and has an acute spectral cutoff at about 400 nm. The glass composition '819 consists essentially of, in cationic percentage, 35-73% S02, 15-45% B O3, 0.12% AI2O3, AI2O3 being less than 10% when S0O2 is greater than 55%, 0-12% Li2O, 0- 20%, Na2O, 0-12% K2O, the Li2? + Na2O + K2O being 4.75-20%, 0-5% CaO + BaO + SrO, 0.125-1.0% Cu2O, 0-1% CdO, 0-5% ZrO2, 0-0.75% Sn02, 0-1% As2O3, and / or Sb2O3, the glass containing 0-1.25% Cl, 0-1.25% Cl, 0-1.0% Br, 0.25-2.0% Cl + Br, and 0 -2% F by weight, and having an R value, calculated in molar percentage, of about 0.15-0.45, the R value not exceeding 0.30, except that the glass composition meets at least one condition selected from the group: up to 12 % cationic Li2O, less than 10% cationic AI2O3, at least 0.3% cationic Cu2O and 0.50-2.0% by weight Cl + Br where R = - - ^ - ^ where the glass oxide values are in B203% cationic. Another embodiment of this invention is a glass substrate having a coating thereon wherein the coating absorbs ultraviolet radiation at wavelengths in the 230-300 nm region while allowing high transmission throughout the region of visible wavelengths, wherein the coating comprises at least one of the oxides of aluminum, silicon, tantalum, titanium, cerium, niobium, hafnium or rare earth elements. These coatings are used with a glass substrate that is capable of acutely cutting ultraviolet radiation at wavelengths in the 400 nm region, while providing high transmission throughout the visible region. With these oxide coatings, the preferred glass is also a glass composition '819. With the glass composition '819, a very preferred coating contains TiO.

EXAMPLE 1 To an optical glass having a '819 glass composition, capable of absorbing throughout the ultraviolet region at wavelengths of 400 nm, while providing high transmission through the visible region in the near IR (2500 nm), it is applied a three-layer sol-gel coating containing TiO2 and SiO2. The coating layers were configured to provide antireflection throughout the visible region, where the first layer adjacent to the substrate was a mixture of SÍO2 and Ti? 2; the second layer was TIO2 and the third layer furthest from the substrate was SiO. The first coating layer was a mixture of 50 weight percent SiO2 and 50 weight percent TiO2. A photo-darkening test was performed on coated and uncoated glasses using a 1000-watt Hg-Xe lamp, and comprising a transmission reading at 500 nm before and after exposures to the lamp for 51.5 hours at 15.24 cm from the cover. quartz reading lamp. This lamp has a high irradiance in the 230 nm region and above the spectral region. A sample with the three-layer sol-gel dip coating consisting of TiO2 and SiO2 was tested together with one having an anti-reflection coating of MgF2 deposited. The results are shown below compared to an unexposed control sample. The transmission at 500 nm was as follows: TABLE 1 Before the After the Exposure exhibition exposure Coating of 98.8 96.7 -2.1 T¡O2 / SiO2 sol-gel Coating of 94.5 70.4 -24.1 MgF2 Uncoated 92.3 56.6 -35.7 Control 92.3 92.5 +0.2 The data indicate that the TiO2-containing coating absorbed sufficient ultraviolet radiation to decrease photo-occlusion by a factor of 10 (using transmission loss at 500 nm).

EXAMPLE 2 In another example, UV radiation blocking glass (glass code 8511, available from Corning Incorporated), was coated with three layers of TiO2 / SiO2 anti-reflective material (Coated), and tested against 8511 chemically reinforced uncoated glass (chemically reinforced ), and 85 1 glass not coated (Not coated). The control sample was an 8511 glass not exposed.

Glass composition 8511 SiO2 59.7 ± 0.30 AI2O3 11.2 + 0.20 B2O3 17.4 + 0.20 Li2O 2.00 + 0.10 Na2O 4.48 + 0.15 K2O 3.30 + 0.15 CuO 0.39 + 0.03 SnO2 0.63 ± 0.03 Br 0.31 ± 0.01 Cl 0.077 ± 0.01 The transmissions measured (%), at 500 nm were the following: Reinforced Coating Time Not Coated Control exposure chemically (hours) 0 98.8 92.4 92.3 92.3 51 96.7 71.2 56.6 92.5 103 94.8 63.1 51.3 92.1 216 93.6 62.0 52.6 92.2 The present invention is particularly useful in applications where ultraviolet radiation blocking glass such as' 819 glass is to be used with artificial light sources, in particular high intensity discharge lamps. In general, the present invention is useful in any applications where UV radiation of short wavelength is present in a light source outlet that reaches the glass. However, this coated glass could also be used in outer space applications. In addition to the modalities discussed above, it will be clear to those skilled in the art that numerous modifications and changes may be made to the previous invention without departing from its intended spirit and scope.

Claims

NOVELTY OF THE INVENTION CLAIMS

1. - A glass substrate having a multilayer coating thereon, the coating comprising at least three layers selected from the group consisting of SiO 2, T 2 O 2 and mixtures thereof, characterized in that said coating absorbs ultraviolet radiation at lengths of wave ranging from about 230 to about 300 nm while providing high transmission over a whole region of visible wavelengths.

2. The coated glass substrate according to claim 1 comprising three layers, further characterized in that the first layer adjacent to the substrate is a mixture of SiO2 and TiO2; the second layer is TiO2 and the third layer furthest from the substrate is SiO2.

3. The coated glass substrate according to claim 1, further characterized in that the first coating layer consists essentially of 25 to 75 weight percent SiO2 and 25 to 75 weight percent TiO2.

4. The coated glass substrate according to claim 1, further characterized in that the first coating layer consists essentially of 50 weight percent SiO2 and 50 weight percent TiO2.

5. - The coated glass substrate according to claim 1, further characterized in that the layers of the coating have a thickness sufficient to absorb ultraviolet radiation at wavelengths ranging from -230 to ~ 300 nm while providing high transmission in a whole region of visible wavelengths.

6. The coated glass substrate according to claim 5, further characterized in that the coating has a thickness ranging from 1500 to 3500 Angstroms.

7. The coated glass substrate according to claim 5, further characterized in that the first layer has a thickness ranging from 300 to 1200 Angstroms.

8. The coated glass substrate according to claim 5, further characterized in that the second layer has a thickness ranging from 300 to 1200 Angstroms.

9. The coated glass substrate according to claim 5, further characterized in that the third layer has a thickness ranging from 300 to 1200 Angstroms.

10. The coated glass substrate according to claim 1, further characterized in that the glass substrate is capable of absorbing ultraviolet radiation at wavelengths in the 380 to 420 nm region, while providing high transmission throughout the visible region, under very sharp cut of the transmission.

11. - The coated glass substrate according to claim 10, further characterized in that the glass substrate is an ultraviolet radiation blocking glass, and the coated glass is an optical element resistant to solarization (or darkening).

12. The coated glass substrate according to claim 11, further characterized in that the ultraviolet radiation blocking glass contains a precipitated cuprous-cadmium halide or cuprous halide crystal phase and has an acute spectral cut in the region 380 to 420 nm , the glass composition consisting essentially of, in cationic percentage, 35-73% SiO2 > 15-45% B2O3, 0-12% AI2O3, AI2O3 being less than 10% when SiO2 is greater than 55%, 0-12% L2O, 0-20%, Na2O, 0-12% K2O, U2O + Na2O + K2O being 4.75-20%, 0-5% CaO + BaO + SrO, 0.125-1.0% Cu2O, 0-1% CdO, 0-5% ZrO2, 0-0.75% SnO2, 0-1% As2O3 and / or Sb2O3, the glass containing 0-1.25% Cl, 0-1.0% Br, 0.25-2.0% Ci + Br, and 0-2% F by weight, and having an R value, calculated in molar percentage, of approximately 0.15- 0.45, the R value not exceeding 0.30, except that the glass composition meets at least one condition selected from the group: up to 12% cationic LÍ2O, less than 10% cationic AI2O3, at least 0.3% cationic Cu2O and 0.50-2.0% in weight Cl + Br.

13. The coated glass substrate according to claim 11, further characterized in that the glass resistant to solarization is a glass capable of transmitting wavelengths in the visible and near infrared regions.

14. - The coated glass substrate according to claim 13, further characterized in that the solarization resistant glass is capable of blocking wavelengths in the 0 to 340 nm region.

15. The coated glass substrate according to claim 13, further characterized in that the glass resistant to solarization begins a total absorption of ultraviolet light in the wavelength range from 200 to 340 nm.

16. The coated glass substrate according to claim 13, further characterized in that the glass resistant to solarization begins a total absorption of ultraviolet light in the wavelength scale from 260 to 300 nm.

17. A glass substrate having a multilayer coating thereon characterized in that the coating absorbs ultraviolet radiation at wavelengths ranging from 250 to 280 nm while providing high transmission over an entire region of visible wavelengths, coating consisting essentially of three layers, wherein the first layer adjacent to the substrate is a mixture of S0O2, characterized in that the glass substrate is capable of absorbing ultraviolet radiation at wavelengths in the 400 nm region, while providing high transmission in the entire visible region, said optical device comprising a glass blocking ultraviolet radiation, and a glass resistance to solarization (or darkening).

18. - An optical body comprising a glass substrate capable of absorbing ultraviolet radiation at wavelengths in the 400 nm region, while providing high transmission throughout the visible region, said glass having thereon at least three layers of a coating that absorbs ultraviolet radiation at wavelengths in the 230-300 nm region while providing high transmission over a whole region of visible wavelengths, the coating comprising at least one of the oxides of tantalum, titanium, cerium, niobium, hafnium or the elements of rare earth.

19. The coated glass substrate according to claim 18, further characterized in that the glass contains a crystallized halide-cadmium cross phase or precipitated crushed glass phase and has an acute spectral cut-off of about 400 nm, the glass composition consisting of essentially of, in cationic percentage, 35-73% Si? 2, 15-45% B2? 3, 0-12% AI2O3, AI2O3 being less than 10% when S¡O2 is greater than 55%, 0-12 % Li2O, 0-20%, Na2O, 0-12% K2O, Li2? + Na2O + K2O being 4.75-20%, 0-5% CaO + BaO + SrO, 0.125-1.0% Cu2O, 0-1% CdO , 0-5% Zr02, 0-0.75% SnO2, 0-1% As2O3, and / or Sb2O3, the glass containing 0-1.25% Cl, 0-1.0% Br, 0.25-2.0% Cl + Br, and 0- 2% F by weight, and having an R value, calculated in molar percentage, of about 0.15-0.45, the R value not exceeding 0.30, except that the glass composition meets at least one condition selected from the group: up to 12% cationic Li2O, less than 10% cationic AI2? 3, at least 0.3% cationic Cu2O and 0.50-2.0 % by weight Cl + Br.

20. - The coated glass substrate according to claim 19, further characterized in that the coating is only TiO2.