GB2076798A - A method of increasing the phototropic effect in phototropic glasses - Google Patents
A method of increasing the phototropic effect in phototropic glasses Download PDFInfo
- Publication number
- GB2076798A GB2076798A GB8114522A GB8114522A GB2076798A GB 2076798 A GB2076798 A GB 2076798A GB 8114522 A GB8114522 A GB 8114522A GB 8114522 A GB8114522 A GB 8114522A GB 2076798 A GB2076798 A GB 2076798A
- Authority
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- United Kingdom
- Prior art keywords
- phototropic
- silver
- crystalline
- precipitates
- glass
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000011521 glass Substances 0.000 title claims abstract description 47
- 230000000694 effects Effects 0.000 title claims abstract description 16
- 238000000034 method Methods 0.000 title claims description 23
- 229910052709 silver Inorganic materials 0.000 claims abstract description 46
- 239000004332 silver Substances 0.000 claims abstract description 44
- 239000002244 precipitate Substances 0.000 claims abstract description 26
- -1 silver halide Chemical class 0.000 claims abstract description 21
- 230000009467 reduction Effects 0.000 claims abstract description 10
- 239000000203 mixture Substances 0.000 claims abstract description 8
- 229910052793 cadmium Inorganic materials 0.000 claims abstract description 6
- 229910052737 gold Inorganic materials 0.000 claims abstract description 5
- 229910052753 mercury Inorganic materials 0.000 claims abstract description 5
- 230000005540 biological transmission Effects 0.000 claims abstract description 4
- 230000008859 change Effects 0.000 claims abstract description 4
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 25
- 230000004913 activation Effects 0.000 claims description 6
- 230000015572 biosynthetic process Effects 0.000 claims description 5
- 230000008569 process Effects 0.000 claims description 5
- 230000002829 reductive effect Effects 0.000 claims description 5
- 238000001228 spectrum Methods 0.000 claims description 4
- 238000010521 absorption reaction Methods 0.000 claims description 3
- 239000000156 glass melt Substances 0.000 claims description 2
- 229910052751 metal Inorganic materials 0.000 abstract description 7
- 239000002184 metal Substances 0.000 abstract description 7
- 238000010899 nucleation Methods 0.000 abstract description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 7
- 230000000638 stimulation Effects 0.000 description 7
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 5
- 239000010931 gold Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 150000002739 metals Chemical class 0.000 description 5
- 235000012239 silicon dioxide Nutrition 0.000 description 5
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 4
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 239000000654 additive Substances 0.000 description 3
- 230000000996 additive effect Effects 0.000 description 3
- 238000000137 annealing Methods 0.000 description 3
- 229910001385 heavy metal Inorganic materials 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 239000000155 melt Substances 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- 239000010453 quartz Substances 0.000 description 3
- 239000010979 ruby Substances 0.000 description 3
- 229910001750 ruby Inorganic materials 0.000 description 3
- 230000035945 sensitivity Effects 0.000 description 3
- 229910000108 silver(I,III) oxide Inorganic materials 0.000 description 3
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 description 2
- FUJCRWPEOMXPAD-UHFFFAOYSA-N Li2O Inorganic materials [Li+].[Li+].[O-2] FUJCRWPEOMXPAD-UHFFFAOYSA-N 0.000 description 2
- KKCBUQHMOMHUOY-UHFFFAOYSA-N Na2O Inorganic materials [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 125000004429 atom Chemical group 0.000 description 2
- 239000006121 base glass Substances 0.000 description 2
- 229910052681 coesite Inorganic materials 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 229910052593 corundum Inorganic materials 0.000 description 2
- 229910052906 cristobalite Inorganic materials 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000010309 melting process Methods 0.000 description 2
- LWJROJCJINYWOX-UHFFFAOYSA-L mercury dichloride Chemical compound Cl[Hg]Cl LWJROJCJINYWOX-UHFFFAOYSA-L 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 229910052682 stishovite Inorganic materials 0.000 description 2
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 description 2
- 229910052905 tridymite Inorganic materials 0.000 description 2
- 229910001845 yogo sapphire Inorganic materials 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 229910018162 SeO2 Inorganic materials 0.000 description 1
- 206010070834 Sensitisation Diseases 0.000 description 1
- MCMNRKCIXSYSNV-UHFFFAOYSA-N ZrO2 Inorganic materials O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000003213 activating effect Effects 0.000 description 1
- 230000006399 behavior Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 238000012505 colouration Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- XUCJHNOBJLKZNU-UHFFFAOYSA-M dilithium;hydroxide Chemical compound [Li+].[Li+].[OH-] XUCJHNOBJLKZNU-UHFFFAOYSA-M 0.000 description 1
- 238000002845 discoloration Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 150000004820 halides Chemical class 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 229910052745 lead Inorganic materials 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000005191 phase separation Methods 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 239000006089 photosensitive glass Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- JPJALAQPGMAKDF-UHFFFAOYSA-N selenium dioxide Chemical compound O=[Se]=O JPJALAQPGMAKDF-UHFFFAOYSA-N 0.000 description 1
- 230000008313 sensitization Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 230000004936 stimulating effect Effects 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 238000005496 tempering Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C4/00—Compositions for glass with special properties
- C03C4/04—Compositions for glass with special properties for photosensitive glass
- C03C4/06—Compositions for glass with special properties for photosensitive glass for phototropic or photochromic glass
Landscapes
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Glass Compositions (AREA)
Abstract
The phototropic effect in a silver halide-containing phototropic glass is increased by producing metallic (e.g. Ag, Au, Hg, Cd or a mixture thereof) seeds or nuclei on the surface of silver halide-containing, crystalline or non- crystalline precipitates in the glass, whereby the transmission change from the colourless, unexposed phototropic state to the absorbing, exposed phototropic state is facilitated. These seeds or nuclei may be formed by reduction of the glass to effect self-seeding and/or by foreign seeding by addition of metal to the glass charge.
Description
SPECIFICATION
A method of increasing the phototropic effect in phototropic glasses
This invention relates to a method of increasing the phototropy of phototropic glasses.
The demand for improvement in phototropic properties of phototropic glasses essentially relates to faster kinetics, i.e. faster phototropic reaction, deeper darkening at a good kinetic rate, higher sensitivity to the stimulating radiation even for weak stimulation energy levels and a more favourable position of stimulation ranges, the application to phototropic glasses in a motor car or to phototropic glazing of buildings being the particular objectives of this invention.
The ever rising raw-material costs of silver, which currently represents an essential cost factor in the production of phototropic glasses, make it highly desirable that either an increased phototropy should be obtainable with the same amount of silver, or the same degree of phototropy with significantly less silver, or that the silver should be replaced, at least partly, by other elements.
Additive colour-changing due to an addition of heavy-metal ions which results in the permanent colloidal separation or precipitation of such ions e.g. by oxidation tinting (silver ruby, gold ruby etc.) and which has been applied for a long time in the production of colloidally tinted silver-ruby glass and the like, as well as dichroism or/and double refraction are not an object of this patent application. This is concerned only with glasses which in unexposed phototropic state have no, or only very little light absorption in the visible region of the spectrum so that they appear colourless or clear.Polychromic glasses, photosensitive glasses and silver-halide bearing, reduced or silver-impregnated tinted glasses are equally not under discussion because of their discoloration in the unexposed phototropic state which makes them unsuitable for application to spectacles or motor-car windows.
Phototropic glasses with silver halide containing, crystalline or non-crystalline precipitates in silicate-, boro-silicate-, phosphate or borate-based base glasses are already known. These base glasses all have a certain phase-separation tendency. Silver, halides and copper are added to the batch for these base glasses prior to melting, the charge materials are then mixed and melted down at a temperature between 1 200 and 1 6000C. After homogenization, by stirring, this melt is cooled down to forming temperature (in the fusion temperature range) press-moulded and cooled to room temperature. This is followed by a heat treatment in the course of which the pressed mouldings (e.g. spectacle lens glasses) are subjected to a heat treatment of, for instance 6400C for two hours.Then the glass is cooled to room temperature whereafter it has phototropic properties. These phototropic properties are caused by the crystalline or non-crystalline, silver halide-containing precipitates which were formed during the heat treatment at 64000. These precipitates have dimensions of the order of 80 to 200 A and are clearly visible under the electron-microscope. Depending on the nature of the heat treatment and on the base glass composition, these precipitates may be crystalline, that is to say characteristically distinguished by a diffraction curve, or non-crystalline. Both types of precipitates were found for different kinds of glass.
Also known are glasses which are coloured and dichroic or polarising by reason of colloidal precipitates of heavy metal ions. Also, effects of this type may be superimposed on the phototropic property.
The object of the present invention is the enhancement or strengthening of the phototropic effect in glasses of the first-mentioned type with a view to achieving stronger phototropy with the same amount of silver or the same degree of phototropy with a smaller amount of silver than heretofore.
According to the present invention there is provided a method for increasing the phototropic behaviour in silver halide-containing phototropic glasses which have little or no absorption in the visible region of the spectrum so that they are colourless, and in which the phototropic effect is caused by crystalline or amorphous precipitates, which are rich in silver halide, comprising producing metallic seeds or nuclei on the surface of the silver halide-containing crystalline or non-crystalline precipitates.
These metallic nuclei may consist of atomic silver, gold, mercury or cadmium, or any mixtures of one or more of these elements. Other metals may be used by way of material for forming such metallic seeds or nuclei. The metallic seeds or nuclei may consist of a single atom or of several agglomerated atoms.
They cover only a part of the surface of the crystalline or non-crystalline, silver halide-containing precipitates and they can be produced by reduction.
The effect of these metallic seeds or nuclei is that of facilitating, or accelerating the transmission change during the transition from the clear, i.e. colourless unexposed state to the coloured or dark state, which can be attributed to a demonstrable reduction in the amount of activation energy required for the colloidal silver-formation on the surface of the silver halide-containing precipitates in the course of the phototropic process.
Whilst it is known that the darkening of phototropic glasses under light exposure is caused by the formation of photolytic silver in metallic form on the surface of the silver halide-containing precipitates in phototropic glasses, and that the kinetics are determined by the growth rate of the silver agglomerates, it has now been found, quite surprisingly, that it is possible to produce, even prior to light exposure, single finest sized nuclei or seeds of silver or other metals on the surface of the silver halidecontaining precipitates to form nucleus cells or sites for the silver centres produced by light exposure. It is possible to show that this achieves a significant reduction in the amount of activation energy needed for the formation under light exposure of silver agglomerates on the surface of the silver halide containing precipitates.Such fine metallic nuclei (Ag, Ag2, Ag3) cannot be optically perceived, that is to say, they do not entail a preliminary darkening or tinting in the unexposed condition, but they improve the kinetics and achieve deeper darkening at a good kinetic rate, higher sensitivity also for weaker stimulation energy, more favourably situated stimulation ranges and even a shift of stimulation ranges right into the visible range. A reduction in the amount of silver needed per kg of glass is achieved because, due to the said metallic nuclei or seeds, deeper darkening is achieved at a good kinetic rate which means that greater phototropy is achieved for the same amount of silver, or the same degree of phototropy is obtained with significantly less silver than in currently known products. Such metallic nuclei or seeds can also be formed by other metals than silver.
It is now found that seed or nucleus formation can be produced by a suitable reducing process without risking colouration of the glass (in the phototropically unexposed state). Self-seeding with Ag is possible by a reduction of the glass melt. Foreign seeding with gold, mercury or cadmium can be obtained by adding a small amount of these metals to the charge. Mixed seeding, that is to say a combination of the two above mentioned methods, will also secure the desired result.
As already mentioned, the effect or action of the metallic seeds can be explained by the lowering of the amount of activation energy needed to form the first silver-agglomerates under light exposure with the aid of these metal nuclei which are already present on the surface of the silver halide-containing precipitates. Greater sensitization (smaller amounts of stimulation or activation energy) increased daylight sensitivity etc. are similarly explained and so is the shift of the stimulation range to longer lengths.
Of all the conceivable possibilities for a reductive generation of metallic seeds, the reduction of the glass seemed td be particularly problematical because, in that case, discolouration by silver or other heavy metals had to be feared. However, it was found that colourless glasses in a phototropically unexposed state can be produced in accordance with this invention so that useful glasses are obtained.
The reduction of the glass is obtained, for example, by producing a melt of the phototropic glass having the following composition:
SiO2 56.0 % by weight
B203 16.0 % by weight
Al203 9.0 % by weight
Na20 3.0 % by weight
K20 3.0 % by weight
Li20 2.0 % by weight
PbO 1.0 % by weight Zero, 4.9 % by weight
TiO2 1.0 % by weight BaO 5.0 % by weight
100.0 % by weight
with the following
additive:
Ag20 0.26 % by weight
Cl 0.40 % by weight
Br 0.35 % by weight
CuO 0.01 % by weight
A weighed sample batch of 3 kg glass was made up from a mixture of standard commercial raw materials and melted in a platinum crucible at 1 4500C for two hours to form a homogenous melt.This was then poured into ingot moulds (40 x 120 x 30 mm) and cooled stressfree to room temperature.
The ingots were then heat-treated at 6450C for two hours. They were then placed into a quartz vessel at 121 OOC and maintained at this temperature for 5 minutes while a continuous flow of forming gas was maintained through the vessel (at the rate of approx. 100 ml/l. glass x min; 20 vol.% of H2, 80 vol.% of N2, injected through a quartz pipe). The melt was then poured into spectacle-lens moulds, cooled stressfree to room temperature, ground and polished to a thickness of 2 mm. The end product was a phototropic spectacle (optical) glass which possessed metallic Ag seeds on the surface of the silver halide-containing precipitates.
According to a simplified form of execution of this method, the reductive melting process of the original batch material was applied in a quartz vessel; however, in that case the injection of forming or activating gas must not be applied at such a high rate as specified above. It was found that adequate quantities of metallic seeds could be obtained with only about 20 ml forming gas per 1 glass x min. In those cases the after-treatment with forming gas at 141 00C can be either abbreviated or totally omitted.
The application of the above described method is independent of the composition of the base glass and equally suited to silicate-, borosilicate-, silico-phosphate-, and borate based glassed in which it produces metallic seeds on the surface of the crystalline or non-crystalline, silver halide-containing precipitates up to 0.5 surface coverage. A further method of producing superficial silver precipitation relies on the effect of exposure to light during the annealing stage.
Gold-, mercury- or cadmium seeds can be produced on the surface of the silver halide containing precipitates in a similar manner, only the appropriate element must be either added to the compound material from the start or stirred in at a later stage. If necessary, the second melting process may be followed by a further annealing stage which should be within the precipitation maximum of the gold-, cadmium or mercury seeds. This temperature can be ascertained during tempering of the glass in a temperature gradient furnace. The length of time needed for such a second annealing process, potentially in a reducing atmosphere will depend on the desired amount of metallic seeds on the surface of the silver-halide containing phase.
Other metals, such as for instance Cu, Pb or Cr appear to have a similar effect as metallic seeds, irrespectively of whether or not they are already known in phototropic glasses. However, their generation involves various problems of different kinds.
The reduction during melting down by application of reducing conditions or by addition of components such as As203, SnO2, SnO, Sb203, Bi203, metallic Zn or metallic Si, SeO2 etc. all of which have a reducing influence under falling temperatures, may also be utilised, however when applying these methods it is important, as in the case of the earlier described application of forming gas, to take due care to prevent unstable redox-pairs being formed which would have the result of causing colour effects in the phototropically unexposed state, e.g. red-, yellow-, orange-and even green-tinting of the glass, which would make the material useless for the envisaged applications. Considered per se, of course, the application of reducing conditions in glass melting is prior art.
TABLE 1
Composition of various phototropic glasses in % by wt. and metallic seeds to be produced therein on the surface of crystalline of non-crystalline silver-halide-containing precipitates. (Components Ag2O to HgCl2 listed as additive % b.w.)
Nr. 2 3 4 5 6 7 8 9 10 SiO2 56,7 56,72 61,47 13,14 13,39 9,82 29,43 28,65 11,0 B2O3 16,5 17,23 16,9 - 4,12 - 39,31 37,29 46,85 Al2O3 9,1 8,93 9,33 24,27 22,66 24,85 19,04 19,79 24,72 P2O5 - 1,05 - 32,76 31,93 35,79 - - ZrO2 1,0 4,1 2,09 2,02 1,85 2,15 1,53 2,6 2,84 TiO2 - 0,53 2,2 0,3 0,51 1,12 - 0,1 Na2O 1,1 4,2 2,2 6,07 4,94 5,93 2,24 1,88 4,94 K2O 1,1 4,2 3,29 9,01 10,3 8,18 0,31 1,67 1,98 Li2O 2,5 2,4 2,52 - - 0,2 2,14 2,6 BaO 7,7 - - 6,57 6,18 6,65 - - CaO - - - 4,04 3,6 3,99 - - MgO - - - - 0,51 - 6,01 4,38 7,66 PbO 4,4 0,63 - 1,72 - 1,33 - 1,04 100,09 99,99 100,00 99,99 99,99 100,01 100,01 100,00 99,99 TABLE 1 (Continued)
Nr. 2 3 4 5 6 7 8 9 10 Ag2O 0,38 0,30 0,27 0,38 0,28 0,19 0,37 0,29 0,32 CuO 0,03 0,02 0,02 0,04 0,005 0,01 0,05 0,005 0,03 Cl 0,40 0,35 0,27 0,27 0,32 0,18 0,17 0,26 0,30 Br 0,30 0,40 0,55 0,38 0,27 0,47 0,18 0,26 0,48 Au - 0,10 - - - 0,22 - 0,15 CdO - - - - 0,18 - 0,20 0,09 HgCl2 - - 0,15 - - - - - 0,27 Type of Metallic Ag Au + Hg Ag Cd Au Cd + Cd + Hg + seeds Ag Ag Au Ag
Claims (9)
1. A method of increasing the phototropic effect in silver halide-containing phototropic glasses which have little or no absorption in the visible region of the spectrum so that they are colourless and in which the phototropic effect is caused by crystalline or amorphous precipitates which are rich in silver halide, comprising producing metallic seeds or nuclei on the surface of the silver halide-containing crystalline or non-crystalline precipitates, whereby the amount of activation energy required in the phototropic process for the formation of colloidal silver on the surface of the silver halide-containing precipitates is reduced so that the transmission change from the colourless, unexposed phototropic state to the absorbing phototropic state is facilitated.
2. A method according to claim 1, wherein the metallic seeds or nuclei are produced from atomic
Ag, Au, Hg or Cd, or from any mixtures of one or more of these elements.
3. A method according to claim 1 or 2, wherein the metallic seeds or nuclei are produced only on a part of the surface of the crystalline or non-crystalline silver-halide-containing precipitates.
4. A method according to any one of claims 1 to 3, wherein the metallic seeds or nuclei are produced by reduction.
5. A method according to claim 4, wherein the crude glass melt is subjected to a reducing treatment at high temperature.
6. A method according to claim 5, wherein the crude glass is treated with a forming gas.
7. A method according to claim 4, wherein the glass is melted down under reducing conditions.
8. A method as claimed in claim 1 substantially as hereinbefore described.
9. A phototropic glass having an increased phototropic effect produced by a method as claimed in any preceding claim.
1 0. A silver halide-containing phototropic glass having little or no absorption in the visible region of the spectrum and in which the phototropic effect is caused by crystalline or amorphous precipitates which are rich in silver halide, wherein metallic seeds or nuclei are on the surface of the silver halidecontaining crystalline or non-crystaliine precipitates, whereby the amount of activation energy required in the phototropic process for the formation of colloidal silver on the surface of the silver halidecontaining precipitates is reduced so that the transmission change from the colourless, unexposed phototropic state to the absorbing phototropic state is facilitated.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19803020357 DE3020357A1 (en) | 1980-05-29 | 1980-05-29 | METHOD FOR REINFORCING THE PHOTOTROPIC EFFECT IN PHOTOTROPIC GLASSES |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2076798A true GB2076798A (en) | 1981-12-09 |
| GB2076798B GB2076798B (en) | 1985-01-30 |
Family
ID=6103484
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8114522A Expired GB2076798B (en) | 1980-05-29 | 1981-05-12 | A method of increasing the phototropic effect in phototropic glasses |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS5722143A (en) |
| DE (1) | DE3020357A1 (en) |
| FR (1) | FR2483394A1 (en) |
| GB (1) | GB2076798B (en) |
| IT (1) | IT8167687A0 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5300557B2 (en) * | 2009-03-27 | 2013-09-25 | 東罐マテリアル・テクノロジー株式会社 | Enamel frit |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB950906A (en) * | 1960-12-30 | 1964-02-26 | Corning Glass Works | Phototropic glass and article made therefrom |
| US3328182A (en) * | 1963-06-24 | 1967-06-27 | Corning Glass Works | Phototropic glass article and method |
| US3892582A (en) * | 1974-02-01 | 1975-07-01 | Robert A Simms | Process for changing the tint of a photochromic material and material formed thereby |
| BR8004828A (en) * | 1979-08-09 | 1981-02-10 | Pilkington Brothers Ltd | PROCESS TO PRODUCE A PHOTOCHROMIC GLASS AND PHOTOCHROMIC GLASS OBTAINED |
| US4251278A (en) * | 1980-01-21 | 1981-02-17 | Corning Glass Works | Photochromic glasses which darken to a brown hue |
-
1980
- 1980-05-29 DE DE19803020357 patent/DE3020357A1/en not_active Withdrawn
-
1981
- 1981-05-12 GB GB8114522A patent/GB2076798B/en not_active Expired
- 1981-05-21 IT IT8167687A patent/IT8167687A0/en unknown
- 1981-05-25 FR FR8110342A patent/FR2483394A1/en active Pending
- 1981-05-28 JP JP8022581A patent/JPS5722143A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| FR2483394A1 (en) | 1981-12-04 |
| JPS5722143A (en) | 1982-02-05 |
| GB2076798B (en) | 1985-01-30 |
| IT8167687A0 (en) | 1981-05-21 |
| DE3020357A1 (en) | 1981-12-03 |
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