CA1061618A - Photochromic gradient lenses - Google Patents
Photochromic gradient lensesInfo
- Publication number
- CA1061618A CA1061618A CA251,044A CA251044A CA1061618A CA 1061618 A CA1061618 A CA 1061618A CA 251044 A CA251044 A CA 251044A CA 1061618 A CA1061618 A CA 1061618A
- Authority
- CA
- Canada
- Prior art keywords
- lens
- glass
- lenses
- photochromic
- phototropic
- Prior art date
- 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.)
- Expired
Links
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
-
- G—PHYSICS
- G02—OPTICS
- G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
- G02C7/00—Optical parts
- G02C7/10—Filters, e.g. for facilitating adaptation of the eyes to the dark; Sunglasses
- G02C7/102—Photochromic filters
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Ophthalmology & Optometry (AREA)
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Geochemistry & Mineralogy (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Physics & Mathematics (AREA)
- General Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Optics & Photonics (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Glass Compositions (AREA)
- Eyeglasses (AREA)
- Re-Forming, After-Treatment, Cutting And Transporting Of Glass Products (AREA)
- Surface Treatment Of Glass (AREA)
- Electrochromic Elements, Electrophoresis, Or Variable Reflection Or Absorption Elements (AREA)
Abstract
PHOTOCHROMIC GRADIENT LENSES
Abstract of the Disclosure The invention achieves local variation, or a continuous gradation, in photochromic or phototropic properties across the face of glass lenses and lens blanks, especially those of ophthalmic quality. The lenses and lens blanks contain all those ingredients required to produce photochromic o? phototropic behavior. They are exposed to a locally variable temperature field or environment, in such manner as to, in at least one portion of the lens or lens blank cause the temperature therein to exceed the strain point but not the softening point of the glass. In other portions of the lens or lens blank the temper-ature is below the strain point, thus causing development of phototropic or photochromic behavior only in those portions of the lens or lens blank exposed to the temperatures above the strain point.
Abstract of the Disclosure The invention achieves local variation, or a continuous gradation, in photochromic or phototropic properties across the face of glass lenses and lens blanks, especially those of ophthalmic quality. The lenses and lens blanks contain all those ingredients required to produce photochromic o? phototropic behavior. They are exposed to a locally variable temperature field or environment, in such manner as to, in at least one portion of the lens or lens blank cause the temperature therein to exceed the strain point but not the softening point of the glass. In other portions of the lens or lens blank the temper-ature is below the strain point, thus causing development of phototropic or photochromic behavior only in those portions of the lens or lens blank exposed to the temperatures above the strain point.
Description
11~6~
.
Field of the Invention This invention relates to phototropic or photochromic ophthalmic lenses and to a process of making such lenses. More specifically, it relates to lenses with continuous gradations in phototropic behavior and to a process of making such lenses.
Background Discussion of The Prior Art Ophthalmic lenses serve basically three purposes:
(1) corr~ction of vision defects;
.
Field of the Invention This invention relates to phototropic or photochromic ophthalmic lenses and to a process of making such lenses. More specifically, it relates to lenses with continuous gradations in phototropic behavior and to a process of making such lenses.
Background Discussion of The Prior Art Ophthalmic lenses serve basically three purposes:
(1) corr~ction of vision defects;
(2) protection against mechanical hazards to the eye;
(3) protection against radiation.
- The first purpose is accomplished by providing transparent articles in the form of lenses with well defined refractive power.
The second purpose is accomplished by either (1) using impact resistant materials for lens construction or (2~ judicious treatment of glass lenses to provide additional strength. Such methods include, for example, the well known and widely practiced procedure of heating lenses above the stra-in point and rapidly quenching them in either an air stream or a liquid. An example of : -the latter process is described in U.S. patent 3,768f992. A
second method of increasing strength is to provide for a compres-sion envelope over the surface of the lens. Such methods are described, for example, in U.S. patents 3,790,260 and 4,036,623.
Protection against such radiation as ultraviolet light, intense visible light or the infrared can be achieved by adding coloxants to the glass batch. Examples for such colorants can be found in the book COLOURED GLASSES by W. A. Weyl, Soc. Glass Technol., Sh~ffield, England, 1967. In the case of ophthalmic lenses made from high polymers, colorants can be added to the material itsel~ as has been done in some commercially available m~
~ ~36~
sunglasses for many years. It is also possible to tint colorless plastic lenses by exposing them to a surface dyeing process.
An example of sucl- a lens is available in commerce under the trade mark "Tintolite" sold by American Optical Corporation of Southbridge, Massachusetts. Clear ~lass lenses can also be tin~ed by exposing them to a so-called "staining process" of which many examples can be found in the above mentioned book bv W. A. Weyl. A specific example of such a staining process applied to glass lenses is described in the pending patent appli-cation file number AO-2958 Serial No. 260,455 filed September 2, 1976 owned by the assignee of this application. A wide variety of permanently colored lenses useful for ophthalmic application are available in commerce and sold under such trade marks as "Truecolor", "Cruxite", "Cosmetan", "Calobar", all manufactured by American Optical Corporation.
Permanently colored or-dyed opthalmic lenses have a disadvanta~e of ~etaining low transmission of light when the wearer of such lenses is exposed to low lev~ls of illumination i.e., is in a more or less dark environment. A typical example of such an environment would be sunglasses worn during nighttime driving which can, of course, be hazardous. This disadvantage can be overcome, to a certain extent, by the many varieties of phototropic or photochromic glass or plastic lenses available in commerce today. Phototropic ophthalmic lenses have been described for example in U.S. patent 3,197,296. The lenses described therein in essence are transparent to visible radiation but will darken upon exposure to actinic radiation, having a transmission to visible radiation of about 45% o~ the original transmissivity. The reduction in transmissivity of such lenses mjp/ _~_ -.
- : - . ,' '~ ., , :, '' :` ' . . ' , .. ,. ' '~ ' ~ ' 10~
.
is re~ersible with a half-ading time of not more than five -minutes. Some other prior art of which we are aware includes:
the ophthalmic lenses described in U. S. patent 3,197,296 utiliz-ing a specific glass composition falling within the following ranges, on a weight per cent basis: 48 to 5~ SiO2, 6 to 10 A1203, 15 to 22 B2O3, 0.8 to 2.0 Na2O, 2.4 to 3.1 Li2O, 0 to 4 K2O, the total Li2O plus Na2O plus K2O being 3.2 to 7.2, 4.5 to 5.3 PbO, 3 to 9 BaO, 0 to 7.2 ZrO2, 0.15 to 0.6 Ag, 0.01 to 0.02 CuO, 0.3 to 1.2 Cl, 0 to 1.0 Br, 0 to 1.0 I, and 0 to 1.2 F; numerous phototropic or photochromic glasses described for example in U. S. patents 3,208,860; 3,548,060; 3,594,198; 3,617,316, 3,703, 388; 3,765,913; 3,795,523; 3,833,511; 3,834,912, British patent 1,275,019; Ger~an patent 2,230,506; and German Auslegeschrift 2,256,775.
In addition to the above mentioned patents on photochromic glasses, all containing silver halide particles uniformly dis-persed throughout the volume of an article made from them, we know Chance-Pilkington Optical Glass Company, England, is market-ing a phototropic phospho-silicate glass under the trade mark "Reactolite". No reference describing compositional details and methods of making this glass has been found by us in the patent literature to date.
Photochromic glasses sensitized by silver halides are also known to us as described in general in the following articles:
W. H. Armistead and S. D. Stookey: "Photochromic Silicate Glasses Sensitized by Silver Halides", SCIENCE, Vol. 144 (1964) pp. 150-154;
G. Gliemeroth and X. ~. Mader: "Phototropic Glass", Agnew.
Chem. Internat. Edit., Vol. 9 (1970) pp. 434-445;
A. V. Dotsenko et al: "A Study of the Effect of Copper Ions on the Relaxation Properties of Photochromic Glasses", Sov.- J. Opt. Technol., Vol. 41 (1974) pp. 395-397;
cb/ ~ 3 ~
~ , : . . , . , :, .
.
~(~6~G~3 -R. ~. Araujo: "Photochromic Glasses", Chapter ~ of the boo~
P~IOTOCH~OMISM edited by G. H. Brown, Willey Interscience, New York (1971) pp. 667-686;
H. Baeh and G. Gliemeroth: "Phase Separation in Phototropic Silver-Halide-Containing Glasses", J. Amer. Cer. Soc. (1971) ~ -pp. 43-44.
All these prior art glasses seem to have in common that:
1. the ingredients producing the photochromic or phototropie behavior are silver halide particles uniformly dispersed in a glass matrix; and 2. artieles made from these glasses must be exposed to a well defined heat treatment to develop photoehromie or phototropic behavior.
The glasses also appear to differ from each other in the composi-tions of the base glasses which serve as carriers for the phototropic or photochromic eenters. In general terms a photo-tropie glass article is deseribed in U.S. patent 3,208,860.
This patent discloses a phototropic article comprising a silieate glass body havin~ in at least a portion thereof microcrystals of at least one siiver halide selected from the group consisting of silver ehloride, silver bromide, and silver iodide, ths eoneen-tration of said crystals in said portion being at least 0.005% by volume.
In addition to glass artieles eontaining silver halide erystals dispersed throughout their entire volume, we know it~as also been proposed to prepare photoehromie glass lenses by diffusing silver ions into a surfaee layer of a base glass eon-taining quantities of halide ionsiand subsequently exposing these artieles to a speeifie heat treatment. Such an article and the mjp~
process of makin~ it is described for example in U.S. patent 3,419,370.
It also has been proposed to prepare photochromic articles by applying phototropic coatings on substrates such as glass or plastic. Such articles are described for example in U.S. patent 3,~75,321 and in a paper by G. Gliemeroth~at the 75th Annual Meeting o~ the ~merican Ceramic Society, Cincinnati, Ohio, May 2, 1973, which was subse~uently published in the Journal of the American Ceramic Society (1974~ pages 332-335 under the title "Reversible Optical Densit~ Changes in Composite Layers".
Photochromic or phototropic lenses of the kind described above overcome to a certain extent the above-noted disadvantages of permanently tinted lenses. Because of the rSeversibility of the photochromic effect they assume a low transmis~ivity if exposed to ultraviolet or blue light but resume high transmissivity in an environment where low illumi-nation levels of activating radiation prevail. Glass lenses have the known advantage over plastic photochromic lenses of more scratch resistance and they do not appear to lose photochromic properties during extended wear due to degradation of active ingredients.
All photochromic or phototropic lenses presently known to us have the disadvantage that recovery of high 'ransmissivity takes several minutes. This has been noticed with discomfort and dislike by wearers under such conditions as driving an automobile , where low levels of illumination exist inside the car and high levels of illumination outside of the vehicle. It obviously is desirable to reduce the light intensity to a driver~s eyes while he or she is observing road and traffic conditions, but simultan~
eously he or she must be permitted to Observe clearly information mjp( 5-~ 8 presented by instruments on the vehicle dashboard where a low level of illumination normally exists. Indeed, it can be dangerous to prevent this. Other instances which illustrate the problem are found in occupations where sudden changes in the level of illumination from bright to dim occur either (1) by rapid changes in the intensity of the light source or (2) by movement of the wearer of the spectacles from an area of high illumination to a darker environment. Similar disadvantages have been observed by wearers of permanently colored lenses.
Some of the above disadvantages have been overcome by use of eyeglasses with a continuous variation of transmissivi-ty from low at the top of the lens to high over the lower portion of the lens. Lenses with such a permanént gradient in degree of color or tint now are available in commerce. We believe the lenses are being prepared by differentially dyeing plastic lenses or by applying a gradiated colored coating over glass lenses by vacuum deposition of absorbing materials. With plastic lenses the color gradient can be achieved by continuously or progressively changing the concentration of dye absorbed by the lens. For example, a high concentration prevails at the top and a low concentration at the bottom of a lens.
In U.S. patent 3,419,370 we find the statement on repre-sentation that a gradient in photochromic behavior across a glass body is attainable by varying the time and/or temperature at which different portions of the glass body are exposed to an ion exchange medium. ~ccording to this patent the ion exchange bath contains, in all instances, silver ions (see Table 2 of the patent).
The gradient in photochromic properties is achieved by causing or~
allowing different concentrations of silver ions to diffuse into mj~ -6-, . . . ... . . . , . , , : ... . .
~l)6~
the glass. The patent teaches, in our opinion, that the glasses described cannot be made photochromic or phototropic without -having been exposed to the diffusion process in the silver con-taining ion exchange bath prior to the heat treatment required to develop phototropic or photochromic behavior. The glasses do not contain any silver ions in the base composition. The patent does not make any speci~ic reference or teaching that we can find of a photochromic gradient over ophthalmic lenses.
In our opinion, the state of the art of making ophthalmic lenses uniformly phototropic or photochromic throughout their entire volume can be summarized as follows:
1. Glasses of the *ypes listed in Table I hereafter are melted following procedures known to those skilled in the art of glass making.
2. Lens blanks are made of these glasses by known methods such as pressing or casting.
3. These articles are exposed to a controlled heat treat-ment to develop silver halide particles of linear dimensions d falling essentially within the range 5 < d < 50nm. The lower limit is required to produce photochromic or phototropic behavior, the upper limit to avoid light scattering unacceptable in ophthalmic products. The total concentration of these silver halide particles which are dispersed uniformly throughout the glass article should be at least O.OOS
vol. %.
In our opinion, the state of the art of making glass arti-cles with a gradient in photochromic or phototropic behavior as deduced from U.S. patent 3,~19,3Z0 can be summarized as follows:
.:~
mjp~ ~7~
- : : , ' ~ . ' , .'' ,.:
. . . . .
:. ~ - : . . ' ' ~ :' - ~36~
.. . . .
1. A base glass having a composition in essence in the general system Alk. Oxide ~ A12O3 - B2O3 - SiO2, with addition of halides to the batch, is melted under ; conditions that allow retention of a sufficient quantity of halides.
2. Lens blanks are made from the glasses by known methods such as pressing or casting.
3. Finished lenses a~e made from thé blanks by grinding and polishing.
- The first purpose is accomplished by providing transparent articles in the form of lenses with well defined refractive power.
The second purpose is accomplished by either (1) using impact resistant materials for lens construction or (2~ judicious treatment of glass lenses to provide additional strength. Such methods include, for example, the well known and widely practiced procedure of heating lenses above the stra-in point and rapidly quenching them in either an air stream or a liquid. An example of : -the latter process is described in U.S. patent 3,768f992. A
second method of increasing strength is to provide for a compres-sion envelope over the surface of the lens. Such methods are described, for example, in U.S. patents 3,790,260 and 4,036,623.
Protection against such radiation as ultraviolet light, intense visible light or the infrared can be achieved by adding coloxants to the glass batch. Examples for such colorants can be found in the book COLOURED GLASSES by W. A. Weyl, Soc. Glass Technol., Sh~ffield, England, 1967. In the case of ophthalmic lenses made from high polymers, colorants can be added to the material itsel~ as has been done in some commercially available m~
~ ~36~
sunglasses for many years. It is also possible to tint colorless plastic lenses by exposing them to a surface dyeing process.
An example of sucl- a lens is available in commerce under the trade mark "Tintolite" sold by American Optical Corporation of Southbridge, Massachusetts. Clear ~lass lenses can also be tin~ed by exposing them to a so-called "staining process" of which many examples can be found in the above mentioned book bv W. A. Weyl. A specific example of such a staining process applied to glass lenses is described in the pending patent appli-cation file number AO-2958 Serial No. 260,455 filed September 2, 1976 owned by the assignee of this application. A wide variety of permanently colored lenses useful for ophthalmic application are available in commerce and sold under such trade marks as "Truecolor", "Cruxite", "Cosmetan", "Calobar", all manufactured by American Optical Corporation.
Permanently colored or-dyed opthalmic lenses have a disadvanta~e of ~etaining low transmission of light when the wearer of such lenses is exposed to low lev~ls of illumination i.e., is in a more or less dark environment. A typical example of such an environment would be sunglasses worn during nighttime driving which can, of course, be hazardous. This disadvantage can be overcome, to a certain extent, by the many varieties of phototropic or photochromic glass or plastic lenses available in commerce today. Phototropic ophthalmic lenses have been described for example in U.S. patent 3,197,296. The lenses described therein in essence are transparent to visible radiation but will darken upon exposure to actinic radiation, having a transmission to visible radiation of about 45% o~ the original transmissivity. The reduction in transmissivity of such lenses mjp/ _~_ -.
- : - . ,' '~ ., , :, '' :` ' . . ' , .. ,. ' '~ ' ~ ' 10~
.
is re~ersible with a half-ading time of not more than five -minutes. Some other prior art of which we are aware includes:
the ophthalmic lenses described in U. S. patent 3,197,296 utiliz-ing a specific glass composition falling within the following ranges, on a weight per cent basis: 48 to 5~ SiO2, 6 to 10 A1203, 15 to 22 B2O3, 0.8 to 2.0 Na2O, 2.4 to 3.1 Li2O, 0 to 4 K2O, the total Li2O plus Na2O plus K2O being 3.2 to 7.2, 4.5 to 5.3 PbO, 3 to 9 BaO, 0 to 7.2 ZrO2, 0.15 to 0.6 Ag, 0.01 to 0.02 CuO, 0.3 to 1.2 Cl, 0 to 1.0 Br, 0 to 1.0 I, and 0 to 1.2 F; numerous phototropic or photochromic glasses described for example in U. S. patents 3,208,860; 3,548,060; 3,594,198; 3,617,316, 3,703, 388; 3,765,913; 3,795,523; 3,833,511; 3,834,912, British patent 1,275,019; Ger~an patent 2,230,506; and German Auslegeschrift 2,256,775.
In addition to the above mentioned patents on photochromic glasses, all containing silver halide particles uniformly dis-persed throughout the volume of an article made from them, we know Chance-Pilkington Optical Glass Company, England, is market-ing a phototropic phospho-silicate glass under the trade mark "Reactolite". No reference describing compositional details and methods of making this glass has been found by us in the patent literature to date.
Photochromic glasses sensitized by silver halides are also known to us as described in general in the following articles:
W. H. Armistead and S. D. Stookey: "Photochromic Silicate Glasses Sensitized by Silver Halides", SCIENCE, Vol. 144 (1964) pp. 150-154;
G. Gliemeroth and X. ~. Mader: "Phototropic Glass", Agnew.
Chem. Internat. Edit., Vol. 9 (1970) pp. 434-445;
A. V. Dotsenko et al: "A Study of the Effect of Copper Ions on the Relaxation Properties of Photochromic Glasses", Sov.- J. Opt. Technol., Vol. 41 (1974) pp. 395-397;
cb/ ~ 3 ~
~ , : . . , . , :, .
.
~(~6~G~3 -R. ~. Araujo: "Photochromic Glasses", Chapter ~ of the boo~
P~IOTOCH~OMISM edited by G. H. Brown, Willey Interscience, New York (1971) pp. 667-686;
H. Baeh and G. Gliemeroth: "Phase Separation in Phototropic Silver-Halide-Containing Glasses", J. Amer. Cer. Soc. (1971) ~ -pp. 43-44.
All these prior art glasses seem to have in common that:
1. the ingredients producing the photochromic or phototropie behavior are silver halide particles uniformly dispersed in a glass matrix; and 2. artieles made from these glasses must be exposed to a well defined heat treatment to develop photoehromie or phototropic behavior.
The glasses also appear to differ from each other in the composi-tions of the base glasses which serve as carriers for the phototropic or photochromic eenters. In general terms a photo-tropie glass article is deseribed in U.S. patent 3,208,860.
This patent discloses a phototropic article comprising a silieate glass body havin~ in at least a portion thereof microcrystals of at least one siiver halide selected from the group consisting of silver ehloride, silver bromide, and silver iodide, ths eoneen-tration of said crystals in said portion being at least 0.005% by volume.
In addition to glass artieles eontaining silver halide erystals dispersed throughout their entire volume, we know it~as also been proposed to prepare photoehromie glass lenses by diffusing silver ions into a surfaee layer of a base glass eon-taining quantities of halide ionsiand subsequently exposing these artieles to a speeifie heat treatment. Such an article and the mjp~
process of makin~ it is described for example in U.S. patent 3,419,370.
It also has been proposed to prepare photochromic articles by applying phototropic coatings on substrates such as glass or plastic. Such articles are described for example in U.S. patent 3,~75,321 and in a paper by G. Gliemeroth~at the 75th Annual Meeting o~ the ~merican Ceramic Society, Cincinnati, Ohio, May 2, 1973, which was subse~uently published in the Journal of the American Ceramic Society (1974~ pages 332-335 under the title "Reversible Optical Densit~ Changes in Composite Layers".
Photochromic or phototropic lenses of the kind described above overcome to a certain extent the above-noted disadvantages of permanently tinted lenses. Because of the rSeversibility of the photochromic effect they assume a low transmis~ivity if exposed to ultraviolet or blue light but resume high transmissivity in an environment where low illumi-nation levels of activating radiation prevail. Glass lenses have the known advantage over plastic photochromic lenses of more scratch resistance and they do not appear to lose photochromic properties during extended wear due to degradation of active ingredients.
All photochromic or phototropic lenses presently known to us have the disadvantage that recovery of high 'ransmissivity takes several minutes. This has been noticed with discomfort and dislike by wearers under such conditions as driving an automobile , where low levels of illumination exist inside the car and high levels of illumination outside of the vehicle. It obviously is desirable to reduce the light intensity to a driver~s eyes while he or she is observing road and traffic conditions, but simultan~
eously he or she must be permitted to Observe clearly information mjp( 5-~ 8 presented by instruments on the vehicle dashboard where a low level of illumination normally exists. Indeed, it can be dangerous to prevent this. Other instances which illustrate the problem are found in occupations where sudden changes in the level of illumination from bright to dim occur either (1) by rapid changes in the intensity of the light source or (2) by movement of the wearer of the spectacles from an area of high illumination to a darker environment. Similar disadvantages have been observed by wearers of permanently colored lenses.
Some of the above disadvantages have been overcome by use of eyeglasses with a continuous variation of transmissivi-ty from low at the top of the lens to high over the lower portion of the lens. Lenses with such a permanént gradient in degree of color or tint now are available in commerce. We believe the lenses are being prepared by differentially dyeing plastic lenses or by applying a gradiated colored coating over glass lenses by vacuum deposition of absorbing materials. With plastic lenses the color gradient can be achieved by continuously or progressively changing the concentration of dye absorbed by the lens. For example, a high concentration prevails at the top and a low concentration at the bottom of a lens.
In U.S. patent 3,419,370 we find the statement on repre-sentation that a gradient in photochromic behavior across a glass body is attainable by varying the time and/or temperature at which different portions of the glass body are exposed to an ion exchange medium. ~ccording to this patent the ion exchange bath contains, in all instances, silver ions (see Table 2 of the patent).
The gradient in photochromic properties is achieved by causing or~
allowing different concentrations of silver ions to diffuse into mj~ -6-, . . . ... . . . , . , , : ... . .
~l)6~
the glass. The patent teaches, in our opinion, that the glasses described cannot be made photochromic or phototropic without -having been exposed to the diffusion process in the silver con-taining ion exchange bath prior to the heat treatment required to develop phototropic or photochromic behavior. The glasses do not contain any silver ions in the base composition. The patent does not make any speci~ic reference or teaching that we can find of a photochromic gradient over ophthalmic lenses.
In our opinion, the state of the art of making ophthalmic lenses uniformly phototropic or photochromic throughout their entire volume can be summarized as follows:
1. Glasses of the *ypes listed in Table I hereafter are melted following procedures known to those skilled in the art of glass making.
2. Lens blanks are made of these glasses by known methods such as pressing or casting.
3. These articles are exposed to a controlled heat treat-ment to develop silver halide particles of linear dimensions d falling essentially within the range 5 < d < 50nm. The lower limit is required to produce photochromic or phototropic behavior, the upper limit to avoid light scattering unacceptable in ophthalmic products. The total concentration of these silver halide particles which are dispersed uniformly throughout the glass article should be at least O.OOS
vol. %.
In our opinion, the state of the art of making glass arti-cles with a gradient in photochromic or phototropic behavior as deduced from U.S. patent 3,~19,3Z0 can be summarized as follows:
.:~
mjp~ ~7~
- : : , ' ~ . ' , .'' ,.:
. . . . .
:. ~ - : . . ' ' ~ :' - ~36~
.. . . .
1. A base glass having a composition in essence in the general system Alk. Oxide ~ A12O3 - B2O3 - SiO2, with addition of halides to the batch, is melted under ; conditions that allow retention of a sufficient quantity of halides.
2. Lens blanks are made from the glasses by known methods such as pressing or casting.
3. Finished lenses a~e made from thé blanks by grinding and polishing.
4. The finished lenses are exposed to a source of silver ions at elevated temperature in such a fashion that in those parts of the lens where a high degree of phototropic or photochromic behavior is desired the silver concentration is higher than in those parts where a low degree of phototropic or photochromic `i behavior is desired.
5. The thus treated lenses ar~e exposed to a carefully controlled heat treatment to grow silver halide crystals to a size required for photochromic or phototropic behavior, but not exceeding linear dimensions of 50 nm to avoid the light scattering unacceptable in ophthalmic lenses.
Summary of Our Invention Ophthalmic lens pressings which do not exhibit photo-tropic or photochromic behavior are made from glasses contain-26 ing all necessary ingredients to produce such phototropic or cb/ - 8 -'. :.
: . : ' ': ':: : ' ': ' , .: ,, .. . , :.`. : . ,, : " :: : . ,,, , ' ' . ': ::
r ~ 6~
photochromic behavior. Such glass is hereafter sometimes referr-ed to as "unnucleated" photochromic glass. This expression is used herein for reasons of simplicity. We are aware that the submicroscopic nuclei required to develop silver halide particles already exist in the non-phototropic state of the glass. In other words, the nuclei are so small they cannot be seen with a light microscope since they do not apparently reflect light.
Numerically speaking, they have a maximum linear dimension which is less than 5 nm. In fact, as will be recogniæed by one skilled in the art, these particles are too small to interact with light in the visible spectrum. We have not measured them but choose -the 5 nm number as one having a meaning to one in this art.
The pressings are not exposed to the heat treatment required to develop photochromic or phototropic behavior. The pressings~
are transferred ormade into lens blanks, the blanks are given a gradient in their phototropic or photochromic behavior by exposing them to a temperature field. The exposure is such that one portion of the blank is heated to a temperature above the strain point but below the softening point of the glass while a distant part of the blank is maintained at a temperature below the strain point.
It has also been found that ophthalmic lenses made from unnucleated glass pressings which have not been exposed to the specific heat treatment re~uired to develop photochromic or phototropic behavior, can be made into semi-finished or finished lenses having a gradient in their phototropic or 27 photochromic behavior across the face.
cb/
.
-- ~Q6:~6~L~
Thus, the invention relates to a glass article having a progressive, local variation in phototropic or photochromic behavior from one edge to an area spaced therefrom, comprising:
an oxide glass body containing throughout its volume at least O.OOS vol. ~ of at least one silver halide selected from the group consisting of silver chloridé, silver bromide, silver iodide, and mixtures thereof, i.n at least that portion of the article showing phototropic or photochromic behavior the halide being in the form of particles, there being a progressive varia-tion in the average linear dimension of the particles substantially corresponding to the variation in phototropic or photochromic behavior, in at least one portion of the article the average linear dimensions of the silver halide particles being smaller than about 5 nm and in other portions the particles substantially, progressively increasing in size to about 50 nm~
In its method aspect the invention relates to a method of making glass ophthalmic quality lenses exhibiting a progressivej local variation in phototropic or photochromic behavior from one edge to an area spaced therefrom comprising: forming an oxide glass body from a glass making batch, the body containing through-out its volume at least 0.005 ~ol. % of at least one silver halide selected from the group consisting of sil~er chloride, silver bromide, silver iodide, and mixtures therèof, subjecting the glass article to a heat treatment, the heat treatment consisting of subjecting one area of such a lens to a temperature above the strain point but below the softening point thereof for a time :-period sufficient to grow silver halide particles having an average linear dimension of about 50 nm, substantially progressive-mjp/ -10- ~.
Summary of Our Invention Ophthalmic lens pressings which do not exhibit photo-tropic or photochromic behavior are made from glasses contain-26 ing all necessary ingredients to produce such phototropic or cb/ - 8 -'. :.
: . : ' ': ':: : ' ': ' , .: ,, .. . , :.`. : . ,, : " :: : . ,,, , ' ' . ': ::
r ~ 6~
photochromic behavior. Such glass is hereafter sometimes referr-ed to as "unnucleated" photochromic glass. This expression is used herein for reasons of simplicity. We are aware that the submicroscopic nuclei required to develop silver halide particles already exist in the non-phototropic state of the glass. In other words, the nuclei are so small they cannot be seen with a light microscope since they do not apparently reflect light.
Numerically speaking, they have a maximum linear dimension which is less than 5 nm. In fact, as will be recogniæed by one skilled in the art, these particles are too small to interact with light in the visible spectrum. We have not measured them but choose -the 5 nm number as one having a meaning to one in this art.
The pressings are not exposed to the heat treatment required to develop photochromic or phototropic behavior. The pressings~
are transferred ormade into lens blanks, the blanks are given a gradient in their phototropic or photochromic behavior by exposing them to a temperature field. The exposure is such that one portion of the blank is heated to a temperature above the strain point but below the softening point of the glass while a distant part of the blank is maintained at a temperature below the strain point.
It has also been found that ophthalmic lenses made from unnucleated glass pressings which have not been exposed to the specific heat treatment re~uired to develop photochromic or phototropic behavior, can be made into semi-finished or finished lenses having a gradient in their phototropic or 27 photochromic behavior across the face.
cb/
.
-- ~Q6:~6~L~
Thus, the invention relates to a glass article having a progressive, local variation in phototropic or photochromic behavior from one edge to an area spaced therefrom, comprising:
an oxide glass body containing throughout its volume at least O.OOS vol. ~ of at least one silver halide selected from the group consisting of silver chloridé, silver bromide, silver iodide, and mixtures thereof, i.n at least that portion of the article showing phototropic or photochromic behavior the halide being in the form of particles, there being a progressive varia-tion in the average linear dimension of the particles substantially corresponding to the variation in phototropic or photochromic behavior, in at least one portion of the article the average linear dimensions of the silver halide particles being smaller than about 5 nm and in other portions the particles substantially, progressively increasing in size to about 50 nm~
In its method aspect the invention relates to a method of making glass ophthalmic quality lenses exhibiting a progressivej local variation in phototropic or photochromic behavior from one edge to an area spaced therefrom comprising: forming an oxide glass body from a glass making batch, the body containing through-out its volume at least 0.005 ~ol. % of at least one silver halide selected from the group consisting of sil~er chloride, silver bromide, silver iodide, and mixtures therèof, subjecting the glass article to a heat treatment, the heat treatment consisting of subjecting one area of such a lens to a temperature above the strain point but below the softening point thereof for a time :-period sufficient to grow silver halide particles having an average linear dimension of about 50 nm, substantially progressive-mjp/ -10- ~.
6~3 ly varying the temperature of heat treakment across the lens from the one edge to the area sp~ced the~e~xo~ in such ~
manner as to form silver halide particles of progressively smaller average linear dimension to thereby produce a lens characterized by a local variation ill phototropic or photo-chromic behavior.
It also has been ~ound that so-called "one-piece multi-focal" or "raised ledge multifocal', glass lenses and progressiye power glass lenses with desirable properties can be made with a gradient in the phototropic or photochromic behavior since such lens designs are particularly suited to the practice of the present invention that the portion of the lens used for distant vision can be made phototropic or photochromic whereas the portion of the lens used for near vision will not have such prope~ties.
To achieve such a gradient in photochromic or phototropic behavior in raised ledge multifocal lenses lens blanks suitable for subsequent generating and polishing are exposed to a tempera-ture gradient as described, alternatively, ~inished lenses can be exposed to a corresponding temperature gradient.
The present invention is a-pplicable to all glass lens blanks or lenses. The lenses and blanks contain all those ingredients required for producing photochromic or phototropic behavior substantially uniformly dispersed therethrough but having silver halide in an unnucleated state, that is, particles thereof are of less size than that required to produce photochromic or phototropic behavior. It is preferred to use glasses with a coefficient of expansion below 60-10 7 per degree C to reduce thermal fracture of lenses and blanks during treatment in the temperature gradient field. However, the invention is not limited to such glasses.
, mjp/ -11-.- . . , : - ,, ., . ~ . : : i .:: .: : , . : ::.
, : . . . . . .
36~
Descrl~tion of the Preferred Embodiments ~ o better understand articles and processes according to the instant invention the following considerations appear to be helpful.
The transmission T of a glass lens can be described by the expression T = exp (-K ZO) where X = coefficient of extinction and ZO = thickness of the lens at the location of measurement measured parallel to the direction of the incident beam of light.
K is a function of the wavelength of light and for a given wave-length is normally a material constant characteri~tic for the glass the lens is made of. The lens thickness ZO i~s a variable of the two space coordinates x and y in a plane normal to the optical axis of the lens. The degree of variation of ZO depends on the Rx values of the lens. For negative lenses ZO is larger at the edge than at the center, for positive lenses ZO is larger at the center than at the edge. This results in a local variation of the light transmission T. Strong negative lenses e.g. made of a colored glass appear to be darker at the edge than at the center. The degree of variation of T in this case is entirely determined by the shape of the lens required to achieve a specific - prescription. In general, ZO = ZO (x, y).
In case of a photochromic or phototropic lens the extinc~
::
tion coefficient K is time dependent and dependent upon wave-length and intensity of the activating radiation. For reasons of simplicity a monochromatic activating radiation of constant 29 intensity shall be assumed. If t is the duration of exposure cb/ - 12 -, .: :~,, . " . . . . ..
,.: : .. . , ,.. .. , ~ . . .^. , ,; : .. .: . .. . . .
~ ~6~6 ~
to such activa-ting radia-tion Kl increases with t or dKl dt ~ r whereby Kl(t) reaches a constant value after approximately 1/2 hour depending upon the g].ass studied and the precision :
of the measurement.
Therefore eq. (1) becomes -Kl(t).Zo Tl(t) = e with dTl dK -Kl(t).Zo - = -Z . 1 e dt dt i.e. the transmission decreases with increasing exposure time.
The saturation value of Tl(t) reached after approximately 30 minutes can be between 30 and 45% depending upon the nature of the glass and the thickness of the lens. The original trans-mission before exposing the lens to activating radiation is nor-mally above 90%.
After removing the activating radiation the lens gradually regains its original transmission value. This process can be des-cribed by introducing a second time dependent extinction co-efficient K2(t) with dK2 dt Correspondingly the~change in transmission T2 with time t is 2 = z 1 2~ e K2(t).Zo dt dt In general terms the transmission T of a photochromic lens therefQre can be described by T (t, x, y) = exp (-Ki(t).Zo (x, y)) with K.(t) = Kl(t) during exposure to activating 29 1 radiation~
cb~ - 13 -,.
. . : , . . . . : .. ~ : .. ..
and Ki~t) = K2~t) aftex removing the activating radiation;
ZO ~x, y) is determined by the prescription values required to provide for correction of vision in each individual case.
To achieve a gradient in phototropic or photochromic behavior across the face of a lensthe coefficient of extinction K must be a function of the two space coordinates x and y in addition to its dependence on time:
K = K (t, x, y).
The corresponding expression fcr light transmission through the lens at point ~x, y~ ig . T (.t, x, y) = exp (-K~t, x, y) ZO(X, Y)~
which for plano lenses can be simplified to T~t, x, y~ = exp (-K(t, x, y)-ZO) with ZO = constant.
To achieve such a space dependent coefficient of extinc-tion prior art U. S. patent 3,419,370 teaches utilization of a ..
corresponding variation in the concentration vf silver required .
to form silver halide crystals providing for phototropic or .`
photochromic behavior. As indicated above in the section "sack-ground Discussion of the Prior Art'! such a process is only appli- .-cable to finished lenses. It is furthermore very difficult to control and requires an additional step; namely, the introduction ~
of silver ions through a diffusion process. It furthermore .
requires use of a glass melted under special conditions to retain - :
sufficient halogen to form silver halide particles. ..
Prior workers have failed to recognize or appreciate that 31 all potentially phototropic or photochromic glass articles utiliz-., .
cb/ - - 14 - :
- . . , . . : ., , ,, , : , ;: ., . , ~ . :, ing silver halide particles to achieve phototropic or photo-' chromic behavior can be used to prepare articles with a gradient in that behavior. To produce an extinction coefficient K ~t, x, y) through local variation of the silver concentration the prior workers have usecl a specially melted glass and subsequent exposure to a silver diffusion process. In contrast we provide a locally variable extinction coefficient through well controlled develop-ment of a proper size distribution of silver halide particles in unnucleated glass initially containing all of the necessary silver . an~ halogen atoms uniformly distrlbuted throughout the entire volume of the glass article. Such a desirable size distribution of silver halide particles is achieved by carefully contxolled exposure to a locally variable temperature field. This can be done with either lens blanks ~r finished lenses. Such lenses are made of glass which can be described as "potentially photochromic or phototropic glass".
While practicing the present invention, care must be taken to avoid thermal fracture of the lenses or lens blanks when they are exposed to a locally variable temperature field. Glasses with a low coefficient of thermal expansion, such as certain boro-silicates, are better suited for this application than glasses with a high coefficient of thermal expansion, such as the phospho-silicates. Boro-silicate glasses have coefficients of thermal expansion in the range approximately 30 -to 60xlO 7/oC. To the best of our knowledge o-ther glasses used commercially as a carrier or matrix for phototropic or photochromic centers have coefficients of thermal expansion of 90xlO 7/oC and above. The 29 higher the coefficient of thermal expansion, the higher the " :.
cb/ - 15 - ;
. . . . .
~;
61~
thermal str~sses existing in the glass article when they are exposed to a temperature gradient.
B f Description of the Drawings Fig. 1 is a schematic of the laboratory furnace used for exposing lens blanks to the temperature gradlent required for practicing the invention.
Fiy. 2 is the temperature profile between points A and B in such a furnace which was used to produce a photochromic gradient in unnucleated potentially phototropic glass of com-position A of Table No. 1.
Fig. 3 schematically illustrates the appearance of a ;
plano lens and the corresponding visual transmittance across the face of such a lens before ~a) and after ~b) exposure to activating radiation ~sunlight) for approximately 30 minutes. ~ ;
Example No. 1 A disk-like glass pressing or lens blank consisting of an unnucleated photochromic glass according to composition A of Table I, having a thickness of 8.5 mm and a diameter of 65 mm, -~
was placed in a furnace according to Fig. 1 and exposed to a temperature gradient according to Fig. 2 for approximately 90 minutes. The lens blank was removed from the furnace, placed between preheated insulating asbestos cloth blankets and allowed to cool to room temperature. The blank exhibited a photochromic gradient upon exposure to sunlight. It returned to its initial uniform state of high transmissivity after being stored for approxi-mately 2 hours a-t room temperature out of ultraviolet radiation (i.e. out of the sun's light). From this blank a plano lens of 2.2 mm center thickness was generated and polished on both 29 sides according to normal procedures. It was then edged to fit cb/ - 16 -6~6~
. .
the left eye of a metal frame sold under the trademark "Quasar"
by American Optical Corporation. A second plano lens was pre-pared following the same procedures to fit the right eye of the same frame. Both finished lenses were then strengthened by an ion exchange process in binary sodium-potassium nitrate bath at ~00C followin~ procedures routinely applied in the industry.
The lenses were then impact tested following FD~ recommendations and mounted in the frame. The pair of spectacles thus prepared had lenses which exhibited the desired characteristics of variable photochromicity from top to bottom.
Example No. 2 A lens blank as described in Example No. 1 was exposed to the same preparation treatment and subsequently ground and polished to a -5.62 diopter unfinished lens. It was then edged to fit the left eye of the same type of frame. A second lens was made following the same procedure except it was ground and polished to a -4.75 diopter unfinished lens and then edged for insertion into the right eye of the same frame. Both lenses were strengthened and impact tested and mounted in the frame.
This pair of prescription spectacles was actually worn and the advantages described above in the Summary of Our Invention were actually observed.
Example No. 3 Six blanks according to Example No. 1 were treated sub-sequently in the laboratory furnace of Fig. 1. They were ground ~' and polished on commercial production equipment used for producing raised ledge bifocal lenses. The Rx values of these lenses were 0 diopters for the,distant vision portion and +1 diopter for the 29 near vision portion, a prescription frequently used for early c~/ - 17 -: . . .
~ , . ~ ......... ,.. ,: : :~ - : . -:
. . ~ , .
~ ~J63L6~L8 presbyopes. These unfinished lenses showed the desirable grad-ient in phototropic behavior as described in the Summary of Our Invention.
Example No. 4 A single vision plano lens having 3.4 mm center thick-ness was generated and polished from a blank consisting oE a potentially photochromic glass having the composition A of Table I. This lens was edged to 48 mm FV7 size and shape, one which is frequently used in glazing safety frames. This ;
plano lens was then exposed to the heat treatment described above with reference to Example No. 1. It was subsequently exposed to an air quench s~rengthening process regularly used in the safety eyewear industry, tested for impact resistance -according to A~SI Z-87, and mounted in a plastic safety frame.
A second lens was prepared following the same procedures and mounted in the other eye of the same frame. This pair of safety spectacles displayed the advantages described above in the Summary of Our Invention.
Table I
Compositions in wt % of Unnucleated Glasses Useable According to This Invention A B C D E
SiO2 53.0 21.4 58.8 57.3 0.0 A123 10.5 37.7 22.9 9.1 8.3 Zr2 2.0 0.0 0.0 0.0 1.3 Li2O 2.1 0.0 4.5 0,0 0.0 BaO 6.0 5.5 0.0 0.0 3.3 28 SrO 0.2 cb/ - lB -. . , , . , , ~ .
~rable I (Cont'd~
A B C D E
Na2O 0.6 3.8 1.5 6.5 16.2 NaF 1.0 1.0 4.7 3.1 0.0 NaCl 1.~ 1.0 1.8 2.6 1.0 Ag2O 0.4 0.5 0.4 0.5 0.6 PbO 5.1 0.0 0.0 1.0 0.0 CuO 0.1 0~1 0.02 0.02 0.02 P2O5 15.6 0.0 0.0 7.5 B2O3 18.0 4.8 2.S 18.6 61.8 K2O 0.0 8.6 0.0 0.0 0.0 NaBr 0.0 0.0 0.8 1.3 0.0 MgO 0.0 0.0 2.1 0.0 0.0 Colorants well known to those skilled in the art may be included. Such colorants are substantially neutral or non-reactive as far as the other glass constituents are concerned.
Exemplary ones include: transition metal oxides including such as Fe2O3, Cr2O3, CoO; certain rare earth oxides such as Nd2O3, Pr23 . ,~ ,, Example No. 5 Glasses B, C, D, and E, may also be used to practice our invention. While we have not actually fabricated lenses in the laboratory to practice the present invention, the use ~ -of these glasses is within the scope of our invention. To use the glasses, one prepares lenses, or lens blanks, as des-cribed in Examples 1 through 4 above. The strain point and softening point of the respective glasses are noted and furnace insulation is placed to allow an appropriate temperature gradient 29 along the length of the furnace. As noted, the appropriate ::
cb/ - 19 ~
, .:
, , - : : , .
~ 6iG~
temperature gradient allows a potential upper portion of a lens to have well-developed silver halide crystals with a controlled progression to substantial freed~m from nucleation at the bottom, or potential bottom, of the lens, or lens blank. This is accom-plished by assuri.ng that a leading edge, for example, of a lens is heated above its strain point but below its softening point while th~ following, or opposite, edge is heated to a lower temperature. After heating, the lenses are allowed to cool suffi.ciently to avoid thermal fracture in an annealin~ ~urnace, or within asbestos blankets, or the like, to prevent thermàl :~
fracture. Conventional grinding, polishing, generating, edging, ..
and glazing techniques then are used to prepare and mount lenses in frames. Suita~le conventional strengthening techniques, pursuant to commercial practices, are used to satisfy Government .;
regulations.
Table II
Prior Art Examples of Silver Halide-Containing Glasses `
Requiring Heat Treatment to Produce Pho-tochromic or :
Phototropic Behavior ~; .
Base Glass System (major ingredients)Source 5ilicateU. S. Patent 3,208,860 Alumino-Boro-Silicate 3,197,296 Boro-Alumina-Alkallne Earth3,5~8,060 Boro-Silica-Potassia 3,59~,198 Borate 3,617,316 :
Lanthanum-Borate 3,703,388 Lanthanum-Alumina-Boro-Silicate3,765,913 .
29 Alumina-Boro-Silicate 3,795,523 .
, cb~ - 20 - :
. . , : ., . . . ~ ,: ~ , : ... : . .. . .. . . .
~ 616~3 Table II ~Cont'd?
Base Glass System (ma~or lngredients) Source .. ..
Alumina-Potassia-Boro-SilicateU.S. Pa-tent 3,833,511 Lead-Zinc-~Iumina-Borate 3,83~,912 Alumina-Boro-PhosphateBrit. Patent 1,275,019 Alumi.na-Phospho-Silicate"Reactolite" (trademark) Analysis Th~ glasses of these references may be used to practice our invention.
Detailed Description of the Drawings .
In Fig. 1 there is shown a suitable refractory insulating support structure 10 for a laboratory furnace used to practice the present invention. Mounted or supported on an upper surface 11 is an elongate arcuate furnace shell 12. The rear end 13 of the shell is closed by brick 20 to form an open ended box. The opposite end 14 is selectively closed with a refractory shield 15. ;
Supported within the grooves 16 are electrical heating elements (not shown to maintain drawing simplicity). The heating elements 20 which we use are ~eavy Duty Electric Co. type 808-104, 850 watts.
Over the top of the furnace shell are a series of refractory insulating brick. In the laboratory furnace the bricks are conventional nine inch straights, two of which have an arcuate opening cut through one long edge. The bricks we used were to provide the gradient, we cut different diameter ones in otherwise identical brick. Thus, the first brick 20 fits snugly against the outer or back surface of the member I2 to close it. The second brick 21 has an arcuate cut 22 and the third brick 23 had a yet deeper arcuate cut 2~. Thus, the bricks 21 and 23 30 are spaced different distances from shell 12. The distance :
cb/ - 21 -~.. . . . .. -, .- ~
: , . ~ : . , .-, . .
- . ~, ,... .
:
. , ~ , . , .-,, .. : . ~
, . . .
.
progressively increases in size allowing variable flows of air and thus greater cooling through convection and radiation. In this manner we allow for the progressive variation in temperature.
Of course, a much finer or more greater temperature variation could be accomplished by using thinner refractory brick with a slower stepwise progression of air space. This technique is well known to those in the refractory and ceramic art. It in fact, utilizes many of the conventional techniques used in fabricating and operatiny tunnel kilns. In fact, the tunnel kiln is the preferred commercial method of practicing the present invention wherein a suitable conveyor enters one end of a kiln with untreated lenses while finished lenses are con-tinuously removed from the opposite end. The lens travel is normal to the temperature gradient.
For example, a kiln or lehr useful for large scale pro-duction of lens blanks and lenses according to the invention.
A belt with speed V is related to the length Q of the furnace zone in which the temperature gradient exists by the approximate formula V = 90 [m/min]. This belt speed will vary depending upon the desired gradation of the photochromic behavior and the type of raw glass used.
Referring again to Fig. 1, a lens 30 is supported on a `
brick of refractory 31 which serves as a lens support. The drawing is substantially to scale and thus the following dimen-sions will allow one skilled in the art to reproduce our labor- -atory furnace with ease.
The following is a parts list for the furnace shown in Fig. 1 that we constructed and used in conducting the work repeat-29 ed in Examples 1-4 above.
cb/ - 22 -Table III
1) Heavy Duty Heater Type 808-104 - 850 Watts 115 volts ~" long hemi. R = 3-1/4"-O.D. R = 2-1/2"I.D. ~3/4" rib) Heavy Duty Electric, Div. of Sola Basic IndustrieS, Hubbard St., Chicago, Ill.
2) Furnace Floor and ~leater Support Kaylo ~Pin1c) K-20 Block 2 pcs. 15" long x 9 1/2" wide x 1" thick Owen-Corning Fiber Glass 4 pcs. 2-1/4 x 2-1~4 x 1" for legs Inailed) 3) Insulating Firebrick 3 pcs. JM-23 ~2-1/2" straights) 9" x 4-1/2" x 2-1/2"
one as-is for rear wall Johns-Manville one shaped to fit heater snugly one shaped with 3/4" longer radius than above (furnace protrudes 1") 4) Block Carrier one piece 4-1/2" long x 2-3/4" wide x 3/4"
thick ~Firebrick, type JM-30~
5) AO Std Fusing Block Chromite (brown,block with wire and ~6.00D R.) 6) Heat Radiator St. S 1/16" thick. Channel Bèam Shape 7" x 7"
x 2-1~2'' Thermo-Couple hole 5/32" @ ct and 2-1/4"
from furnace floor
manner as to form silver halide particles of progressively smaller average linear dimension to thereby produce a lens characterized by a local variation ill phototropic or photo-chromic behavior.
It also has been ~ound that so-called "one-piece multi-focal" or "raised ledge multifocal', glass lenses and progressiye power glass lenses with desirable properties can be made with a gradient in the phototropic or photochromic behavior since such lens designs are particularly suited to the practice of the present invention that the portion of the lens used for distant vision can be made phototropic or photochromic whereas the portion of the lens used for near vision will not have such prope~ties.
To achieve such a gradient in photochromic or phototropic behavior in raised ledge multifocal lenses lens blanks suitable for subsequent generating and polishing are exposed to a tempera-ture gradient as described, alternatively, ~inished lenses can be exposed to a corresponding temperature gradient.
The present invention is a-pplicable to all glass lens blanks or lenses. The lenses and blanks contain all those ingredients required for producing photochromic or phototropic behavior substantially uniformly dispersed therethrough but having silver halide in an unnucleated state, that is, particles thereof are of less size than that required to produce photochromic or phototropic behavior. It is preferred to use glasses with a coefficient of expansion below 60-10 7 per degree C to reduce thermal fracture of lenses and blanks during treatment in the temperature gradient field. However, the invention is not limited to such glasses.
, mjp/ -11-.- . . , : - ,, ., . ~ . : : i .:: .: : , . : ::.
, : . . . . . .
36~
Descrl~tion of the Preferred Embodiments ~ o better understand articles and processes according to the instant invention the following considerations appear to be helpful.
The transmission T of a glass lens can be described by the expression T = exp (-K ZO) where X = coefficient of extinction and ZO = thickness of the lens at the location of measurement measured parallel to the direction of the incident beam of light.
K is a function of the wavelength of light and for a given wave-length is normally a material constant characteri~tic for the glass the lens is made of. The lens thickness ZO i~s a variable of the two space coordinates x and y in a plane normal to the optical axis of the lens. The degree of variation of ZO depends on the Rx values of the lens. For negative lenses ZO is larger at the edge than at the center, for positive lenses ZO is larger at the center than at the edge. This results in a local variation of the light transmission T. Strong negative lenses e.g. made of a colored glass appear to be darker at the edge than at the center. The degree of variation of T in this case is entirely determined by the shape of the lens required to achieve a specific - prescription. In general, ZO = ZO (x, y).
In case of a photochromic or phototropic lens the extinc~
::
tion coefficient K is time dependent and dependent upon wave-length and intensity of the activating radiation. For reasons of simplicity a monochromatic activating radiation of constant 29 intensity shall be assumed. If t is the duration of exposure cb/ - 12 -, .: :~,, . " . . . . ..
,.: : .. . , ,.. .. , ~ . . .^. , ,; : .. .: . .. . . .
~ ~6~6 ~
to such activa-ting radia-tion Kl increases with t or dKl dt ~ r whereby Kl(t) reaches a constant value after approximately 1/2 hour depending upon the g].ass studied and the precision :
of the measurement.
Therefore eq. (1) becomes -Kl(t).Zo Tl(t) = e with dTl dK -Kl(t).Zo - = -Z . 1 e dt dt i.e. the transmission decreases with increasing exposure time.
The saturation value of Tl(t) reached after approximately 30 minutes can be between 30 and 45% depending upon the nature of the glass and the thickness of the lens. The original trans-mission before exposing the lens to activating radiation is nor-mally above 90%.
After removing the activating radiation the lens gradually regains its original transmission value. This process can be des-cribed by introducing a second time dependent extinction co-efficient K2(t) with dK2 dt Correspondingly the~change in transmission T2 with time t is 2 = z 1 2~ e K2(t).Zo dt dt In general terms the transmission T of a photochromic lens therefQre can be described by T (t, x, y) = exp (-Ki(t).Zo (x, y)) with K.(t) = Kl(t) during exposure to activating 29 1 radiation~
cb~ - 13 -,.
. . : , . . . . : .. ~ : .. ..
and Ki~t) = K2~t) aftex removing the activating radiation;
ZO ~x, y) is determined by the prescription values required to provide for correction of vision in each individual case.
To achieve a gradient in phototropic or photochromic behavior across the face of a lensthe coefficient of extinction K must be a function of the two space coordinates x and y in addition to its dependence on time:
K = K (t, x, y).
The corresponding expression fcr light transmission through the lens at point ~x, y~ ig . T (.t, x, y) = exp (-K~t, x, y) ZO(X, Y)~
which for plano lenses can be simplified to T~t, x, y~ = exp (-K(t, x, y)-ZO) with ZO = constant.
To achieve such a space dependent coefficient of extinc-tion prior art U. S. patent 3,419,370 teaches utilization of a ..
corresponding variation in the concentration vf silver required .
to form silver halide crystals providing for phototropic or .`
photochromic behavior. As indicated above in the section "sack-ground Discussion of the Prior Art'! such a process is only appli- .-cable to finished lenses. It is furthermore very difficult to control and requires an additional step; namely, the introduction ~
of silver ions through a diffusion process. It furthermore .
requires use of a glass melted under special conditions to retain - :
sufficient halogen to form silver halide particles. ..
Prior workers have failed to recognize or appreciate that 31 all potentially phototropic or photochromic glass articles utiliz-., .
cb/ - - 14 - :
- . . , . . : ., , ,, , : , ;: ., . , ~ . :, ing silver halide particles to achieve phototropic or photo-' chromic behavior can be used to prepare articles with a gradient in that behavior. To produce an extinction coefficient K ~t, x, y) through local variation of the silver concentration the prior workers have usecl a specially melted glass and subsequent exposure to a silver diffusion process. In contrast we provide a locally variable extinction coefficient through well controlled develop-ment of a proper size distribution of silver halide particles in unnucleated glass initially containing all of the necessary silver . an~ halogen atoms uniformly distrlbuted throughout the entire volume of the glass article. Such a desirable size distribution of silver halide particles is achieved by carefully contxolled exposure to a locally variable temperature field. This can be done with either lens blanks ~r finished lenses. Such lenses are made of glass which can be described as "potentially photochromic or phototropic glass".
While practicing the present invention, care must be taken to avoid thermal fracture of the lenses or lens blanks when they are exposed to a locally variable temperature field. Glasses with a low coefficient of thermal expansion, such as certain boro-silicates, are better suited for this application than glasses with a high coefficient of thermal expansion, such as the phospho-silicates. Boro-silicate glasses have coefficients of thermal expansion in the range approximately 30 -to 60xlO 7/oC. To the best of our knowledge o-ther glasses used commercially as a carrier or matrix for phototropic or photochromic centers have coefficients of thermal expansion of 90xlO 7/oC and above. The 29 higher the coefficient of thermal expansion, the higher the " :.
cb/ - 15 - ;
. . . . .
~;
61~
thermal str~sses existing in the glass article when they are exposed to a temperature gradient.
B f Description of the Drawings Fig. 1 is a schematic of the laboratory furnace used for exposing lens blanks to the temperature gradlent required for practicing the invention.
Fiy. 2 is the temperature profile between points A and B in such a furnace which was used to produce a photochromic gradient in unnucleated potentially phototropic glass of com-position A of Table No. 1.
Fig. 3 schematically illustrates the appearance of a ;
plano lens and the corresponding visual transmittance across the face of such a lens before ~a) and after ~b) exposure to activating radiation ~sunlight) for approximately 30 minutes. ~ ;
Example No. 1 A disk-like glass pressing or lens blank consisting of an unnucleated photochromic glass according to composition A of Table I, having a thickness of 8.5 mm and a diameter of 65 mm, -~
was placed in a furnace according to Fig. 1 and exposed to a temperature gradient according to Fig. 2 for approximately 90 minutes. The lens blank was removed from the furnace, placed between preheated insulating asbestos cloth blankets and allowed to cool to room temperature. The blank exhibited a photochromic gradient upon exposure to sunlight. It returned to its initial uniform state of high transmissivity after being stored for approxi-mately 2 hours a-t room temperature out of ultraviolet radiation (i.e. out of the sun's light). From this blank a plano lens of 2.2 mm center thickness was generated and polished on both 29 sides according to normal procedures. It was then edged to fit cb/ - 16 -6~6~
. .
the left eye of a metal frame sold under the trademark "Quasar"
by American Optical Corporation. A second plano lens was pre-pared following the same procedures to fit the right eye of the same frame. Both finished lenses were then strengthened by an ion exchange process in binary sodium-potassium nitrate bath at ~00C followin~ procedures routinely applied in the industry.
The lenses were then impact tested following FD~ recommendations and mounted in the frame. The pair of spectacles thus prepared had lenses which exhibited the desired characteristics of variable photochromicity from top to bottom.
Example No. 2 A lens blank as described in Example No. 1 was exposed to the same preparation treatment and subsequently ground and polished to a -5.62 diopter unfinished lens. It was then edged to fit the left eye of the same type of frame. A second lens was made following the same procedure except it was ground and polished to a -4.75 diopter unfinished lens and then edged for insertion into the right eye of the same frame. Both lenses were strengthened and impact tested and mounted in the frame.
This pair of prescription spectacles was actually worn and the advantages described above in the Summary of Our Invention were actually observed.
Example No. 3 Six blanks according to Example No. 1 were treated sub-sequently in the laboratory furnace of Fig. 1. They were ground ~' and polished on commercial production equipment used for producing raised ledge bifocal lenses. The Rx values of these lenses were 0 diopters for the,distant vision portion and +1 diopter for the 29 near vision portion, a prescription frequently used for early c~/ - 17 -: . . .
~ , . ~ ......... ,.. ,: : :~ - : . -:
. . ~ , .
~ ~J63L6~L8 presbyopes. These unfinished lenses showed the desirable grad-ient in phototropic behavior as described in the Summary of Our Invention.
Example No. 4 A single vision plano lens having 3.4 mm center thick-ness was generated and polished from a blank consisting oE a potentially photochromic glass having the composition A of Table I. This lens was edged to 48 mm FV7 size and shape, one which is frequently used in glazing safety frames. This ;
plano lens was then exposed to the heat treatment described above with reference to Example No. 1. It was subsequently exposed to an air quench s~rengthening process regularly used in the safety eyewear industry, tested for impact resistance -according to A~SI Z-87, and mounted in a plastic safety frame.
A second lens was prepared following the same procedures and mounted in the other eye of the same frame. This pair of safety spectacles displayed the advantages described above in the Summary of Our Invention.
Table I
Compositions in wt % of Unnucleated Glasses Useable According to This Invention A B C D E
SiO2 53.0 21.4 58.8 57.3 0.0 A123 10.5 37.7 22.9 9.1 8.3 Zr2 2.0 0.0 0.0 0.0 1.3 Li2O 2.1 0.0 4.5 0,0 0.0 BaO 6.0 5.5 0.0 0.0 3.3 28 SrO 0.2 cb/ - lB -. . , , . , , ~ .
~rable I (Cont'd~
A B C D E
Na2O 0.6 3.8 1.5 6.5 16.2 NaF 1.0 1.0 4.7 3.1 0.0 NaCl 1.~ 1.0 1.8 2.6 1.0 Ag2O 0.4 0.5 0.4 0.5 0.6 PbO 5.1 0.0 0.0 1.0 0.0 CuO 0.1 0~1 0.02 0.02 0.02 P2O5 15.6 0.0 0.0 7.5 B2O3 18.0 4.8 2.S 18.6 61.8 K2O 0.0 8.6 0.0 0.0 0.0 NaBr 0.0 0.0 0.8 1.3 0.0 MgO 0.0 0.0 2.1 0.0 0.0 Colorants well known to those skilled in the art may be included. Such colorants are substantially neutral or non-reactive as far as the other glass constituents are concerned.
Exemplary ones include: transition metal oxides including such as Fe2O3, Cr2O3, CoO; certain rare earth oxides such as Nd2O3, Pr23 . ,~ ,, Example No. 5 Glasses B, C, D, and E, may also be used to practice our invention. While we have not actually fabricated lenses in the laboratory to practice the present invention, the use ~ -of these glasses is within the scope of our invention. To use the glasses, one prepares lenses, or lens blanks, as des-cribed in Examples 1 through 4 above. The strain point and softening point of the respective glasses are noted and furnace insulation is placed to allow an appropriate temperature gradient 29 along the length of the furnace. As noted, the appropriate ::
cb/ - 19 ~
, .:
, , - : : , .
~ 6iG~
temperature gradient allows a potential upper portion of a lens to have well-developed silver halide crystals with a controlled progression to substantial freed~m from nucleation at the bottom, or potential bottom, of the lens, or lens blank. This is accom-plished by assuri.ng that a leading edge, for example, of a lens is heated above its strain point but below its softening point while th~ following, or opposite, edge is heated to a lower temperature. After heating, the lenses are allowed to cool suffi.ciently to avoid thermal fracture in an annealin~ ~urnace, or within asbestos blankets, or the like, to prevent thermàl :~
fracture. Conventional grinding, polishing, generating, edging, ..
and glazing techniques then are used to prepare and mount lenses in frames. Suita~le conventional strengthening techniques, pursuant to commercial practices, are used to satisfy Government .;
regulations.
Table II
Prior Art Examples of Silver Halide-Containing Glasses `
Requiring Heat Treatment to Produce Pho-tochromic or :
Phototropic Behavior ~; .
Base Glass System (major ingredients)Source 5ilicateU. S. Patent 3,208,860 Alumino-Boro-Silicate 3,197,296 Boro-Alumina-Alkallne Earth3,5~8,060 Boro-Silica-Potassia 3,59~,198 Borate 3,617,316 :
Lanthanum-Borate 3,703,388 Lanthanum-Alumina-Boro-Silicate3,765,913 .
29 Alumina-Boro-Silicate 3,795,523 .
, cb~ - 20 - :
. . , : ., . . . ~ ,: ~ , : ... : . .. . .. . . .
~ 616~3 Table II ~Cont'd?
Base Glass System (ma~or lngredients) Source .. ..
Alumina-Potassia-Boro-SilicateU.S. Pa-tent 3,833,511 Lead-Zinc-~Iumina-Borate 3,83~,912 Alumina-Boro-PhosphateBrit. Patent 1,275,019 Alumi.na-Phospho-Silicate"Reactolite" (trademark) Analysis Th~ glasses of these references may be used to practice our invention.
Detailed Description of the Drawings .
In Fig. 1 there is shown a suitable refractory insulating support structure 10 for a laboratory furnace used to practice the present invention. Mounted or supported on an upper surface 11 is an elongate arcuate furnace shell 12. The rear end 13 of the shell is closed by brick 20 to form an open ended box. The opposite end 14 is selectively closed with a refractory shield 15. ;
Supported within the grooves 16 are electrical heating elements (not shown to maintain drawing simplicity). The heating elements 20 which we use are ~eavy Duty Electric Co. type 808-104, 850 watts.
Over the top of the furnace shell are a series of refractory insulating brick. In the laboratory furnace the bricks are conventional nine inch straights, two of which have an arcuate opening cut through one long edge. The bricks we used were to provide the gradient, we cut different diameter ones in otherwise identical brick. Thus, the first brick 20 fits snugly against the outer or back surface of the member I2 to close it. The second brick 21 has an arcuate cut 22 and the third brick 23 had a yet deeper arcuate cut 2~. Thus, the bricks 21 and 23 30 are spaced different distances from shell 12. The distance :
cb/ - 21 -~.. . . . .. -, .- ~
: , . ~ : . , .-, . .
- . ~, ,... .
:
. , ~ , . , .-,, .. : . ~
, . . .
.
progressively increases in size allowing variable flows of air and thus greater cooling through convection and radiation. In this manner we allow for the progressive variation in temperature.
Of course, a much finer or more greater temperature variation could be accomplished by using thinner refractory brick with a slower stepwise progression of air space. This technique is well known to those in the refractory and ceramic art. It in fact, utilizes many of the conventional techniques used in fabricating and operatiny tunnel kilns. In fact, the tunnel kiln is the preferred commercial method of practicing the present invention wherein a suitable conveyor enters one end of a kiln with untreated lenses while finished lenses are con-tinuously removed from the opposite end. The lens travel is normal to the temperature gradient.
For example, a kiln or lehr useful for large scale pro-duction of lens blanks and lenses according to the invention.
A belt with speed V is related to the length Q of the furnace zone in which the temperature gradient exists by the approximate formula V = 90 [m/min]. This belt speed will vary depending upon the desired gradation of the photochromic behavior and the type of raw glass used.
Referring again to Fig. 1, a lens 30 is supported on a `
brick of refractory 31 which serves as a lens support. The drawing is substantially to scale and thus the following dimen-sions will allow one skilled in the art to reproduce our labor- -atory furnace with ease.
The following is a parts list for the furnace shown in Fig. 1 that we constructed and used in conducting the work repeat-29 ed in Examples 1-4 above.
cb/ - 22 -Table III
1) Heavy Duty Heater Type 808-104 - 850 Watts 115 volts ~" long hemi. R = 3-1/4"-O.D. R = 2-1/2"I.D. ~3/4" rib) Heavy Duty Electric, Div. of Sola Basic IndustrieS, Hubbard St., Chicago, Ill.
2) Furnace Floor and ~leater Support Kaylo ~Pin1c) K-20 Block 2 pcs. 15" long x 9 1/2" wide x 1" thick Owen-Corning Fiber Glass 4 pcs. 2-1/4 x 2-1~4 x 1" for legs Inailed) 3) Insulating Firebrick 3 pcs. JM-23 ~2-1/2" straights) 9" x 4-1/2" x 2-1/2"
one as-is for rear wall Johns-Manville one shaped to fit heater snugly one shaped with 3/4" longer radius than above (furnace protrudes 1") 4) Block Carrier one piece 4-1/2" long x 2-3/4" wide x 3/4"
thick ~Firebrick, type JM-30~
5) AO Std Fusing Block Chromite (brown,block with wire and ~6.00D R.) 6) Heat Radiator St. S 1/16" thick. Channel Bèam Shape 7" x 7"
x 2-1~2'' Thermo-Couple hole 5/32" @ ct and 2-1/4"
from furnace floor
7) Variac. 10 AMP 1.4 KVA
8) Type 'K' Shielded Thermocouple etc. Recorder AZAR
Desirable: Programmable Temp. Controller, tongs, asbestos gloves, annealing oven, Colmoscope ~trade mark), flash lamp. U.V.
The base supporting structure 10 is 15" long 9" wide and 4" above a supporting table. The legs are 2-1/4" x 2-1/4" x 1"
slices of brick and the thickness of structure 10 is 2". The cb/ - 23 -; . . : ~ . . .
"
~: . . . .
6~
refractory insulating brick are of standard dimension i.e. 9" x
Desirable: Programmable Temp. Controller, tongs, asbestos gloves, annealing oven, Colmoscope ~trade mark), flash lamp. U.V.
The base supporting structure 10 is 15" long 9" wide and 4" above a supporting table. The legs are 2-1/4" x 2-1/4" x 1"
slices of brick and the thickness of structure 10 is 2". The cb/ - 23 -; . . : ~ . . .
"
~: . . . .
6~
refractory insulating brick are of standard dimension i.e. 9" x
9" x 2-1/2". The arcuate shell 12 is 6" long and extends 1" beyond ~ , the brick 23. l'he radius of the inside of the exposed face of a strut forming the channels in which the heating elements are located is 2-1/2". The radius of the curvature oE the outslde of the shell is 3-1/2l" and the radius of the arcuate cu-t in the forward brick 24 is 3-1/4". The shield 15 is a piece of angle iron 7" high having rearwardly extending legs 2-1/2" in length. ';
Broadly speaking, an article fabricated according to the present invention is a lens or lens blank exhibiting regressive variation in pho~ochromic behavior from top to bottom as the lens appears in a frame. Distributed throughout the oxide glass ' body from which the lens or blank is fabricated are silver halide particles constitutingat least 0.005 vol. % thereof. , The silver halide is selected from the group consisting of silver chloride, silver bromide, and silver iodide. The silver halide particles in the finished lens are of such a size distribution that in at least one portion of the article the linear dimension of said particles is smaller than 5 nanometers (nm) and in remain-ing portion of the article in a range between 5 and 50 nm. Thus, at the top, or through that portion generally referred to as the "distance portion" the particles are relatively large whereas towards the lower or reading portion of the lens the particles are progressively much smaller to about 5 nm at the bottom.
As elsewhere mentioned above, Fig. 2 is a diagram of the temperature profile actually established in the furnace in fabrication of the lenses described in Examples 1 through 4. ' Fig. 3A is a schematic diagram of a clear lens having the un-nucleated characteristics described above prior to treatment in ~30 the furnace of Fig. 1. Fig. 3B is such a lens after treatment.
cb/ - 24 ~
~J6:~L61~
The preferred and best mode of practicing our invcntion presently known to us is Example 1 above, using glass A of Table I in the furnace of Fig. 1 and using the temperature profile of ~ig. 2.
In the foregoing discussion we have mentioned variation in the linear dimensions of the silver halide particles. It should be understood that when we are discussing the particles being smaller than about 5 nm and substantially progressively increased in size to about 50 nm we are describing an average particle. When we say "average" we mean a substantial per ponderance of the particles have the specific linear dimensions.
Of course, some particles will be smaller and some larger in any given area because of the lack of precise control over the chemical reaction which results in the particle formation.
While we described silver chloride, silver bromide, and silver iodide there can also be mixtures thereof. Broadly, the inven-tion consists of providing for local variation in phototropic or photochromic behavior from one edge to an area spaced therefrom.
For example, from a very low transmissivity condition adjacent from a top edge of a lens when it is mounted on a frame to, in a case of a Bifocallens, very high transmissivity in the reading portion which is adjacent at the bottom edge of a lens when it is in a frame.
Having thus described our invention in detail and with sufficient particularity as to enable one skilled in the art to practice the invention what is desired to have protected by 27 Letters Patent is set forth in the following claims.
cb~ - 25 -.: . : . . . ,, , ~ . ., . , . " ~
., . , , : ' :
Broadly speaking, an article fabricated according to the present invention is a lens or lens blank exhibiting regressive variation in pho~ochromic behavior from top to bottom as the lens appears in a frame. Distributed throughout the oxide glass ' body from which the lens or blank is fabricated are silver halide particles constitutingat least 0.005 vol. % thereof. , The silver halide is selected from the group consisting of silver chloride, silver bromide, and silver iodide. The silver halide particles in the finished lens are of such a size distribution that in at least one portion of the article the linear dimension of said particles is smaller than 5 nanometers (nm) and in remain-ing portion of the article in a range between 5 and 50 nm. Thus, at the top, or through that portion generally referred to as the "distance portion" the particles are relatively large whereas towards the lower or reading portion of the lens the particles are progressively much smaller to about 5 nm at the bottom.
As elsewhere mentioned above, Fig. 2 is a diagram of the temperature profile actually established in the furnace in fabrication of the lenses described in Examples 1 through 4. ' Fig. 3A is a schematic diagram of a clear lens having the un-nucleated characteristics described above prior to treatment in ~30 the furnace of Fig. 1. Fig. 3B is such a lens after treatment.
cb/ - 24 ~
~J6:~L61~
The preferred and best mode of practicing our invcntion presently known to us is Example 1 above, using glass A of Table I in the furnace of Fig. 1 and using the temperature profile of ~ig. 2.
In the foregoing discussion we have mentioned variation in the linear dimensions of the silver halide particles. It should be understood that when we are discussing the particles being smaller than about 5 nm and substantially progressively increased in size to about 50 nm we are describing an average particle. When we say "average" we mean a substantial per ponderance of the particles have the specific linear dimensions.
Of course, some particles will be smaller and some larger in any given area because of the lack of precise control over the chemical reaction which results in the particle formation.
While we described silver chloride, silver bromide, and silver iodide there can also be mixtures thereof. Broadly, the inven-tion consists of providing for local variation in phototropic or photochromic behavior from one edge to an area spaced therefrom.
For example, from a very low transmissivity condition adjacent from a top edge of a lens when it is mounted on a frame to, in a case of a Bifocallens, very high transmissivity in the reading portion which is adjacent at the bottom edge of a lens when it is in a frame.
Having thus described our invention in detail and with sufficient particularity as to enable one skilled in the art to practice the invention what is desired to have protected by 27 Letters Patent is set forth in the following claims.
cb~ - 25 -.: . : . . . ,, , ~ . ., . , . " ~
., . , , : ' :
Claims (11)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A glass article having a progressive, local variation in phototropic or photochromic behavior from one edge to an area spaced therefrom, comprising:
an oxide glass body containing throughout its volume at least 0.005 vol. % of at least one silver halide selected from the group consisting of silver chloride, silver bromide, silver iodide, and mixtures thereof, in at least that portion of the article showing phototropic or photochromic behavior .
said halide being in the form of particles, there being a pro-gressive variation in the average linear dimension of said par-ticles substantially corresponding to the variation in photo-tropic or photochromic behavior, in at least one portion of the article the average linear dimensions of said silver halide par-ticles being smaller than about 5 nm and in other portions said particles substantially, progressively increasing in size to about 50 nm.
an oxide glass body containing throughout its volume at least 0.005 vol. % of at least one silver halide selected from the group consisting of silver chloride, silver bromide, silver iodide, and mixtures thereof, in at least that portion of the article showing phototropic or photochromic behavior .
said halide being in the form of particles, there being a pro-gressive variation in the average linear dimension of said par-ticles substantially corresponding to the variation in photo-tropic or photochromic behavior, in at least one portion of the article the average linear dimensions of said silver halide par-ticles being smaller than about 5 nm and in other portions said particles substantially, progressively increasing in size to about 50 nm.
2. An article according to claim 1 in the form of an ophthal-mic lens blank.
3. An article according to claim 1 in the form of an ophthal-mic lens selected from the group consisting of safety lenses, progressive power lenses, raised ledge multifocal lenses, single vision lenses.
4. An ophthalmic lens blank according to claim 2 in which only the upper or distance portion of said lens exhibits photo-tropic or photochromic behavior.
5. A lens blank according to claim 4, in which said blank is in the form of a raised ledge multifocal lens.
6. An ophthalmic lens according to claim 4, in which said lens is in the form of a progressive power lens.
7. That method of making glass ophthalmic quality lenses exhibiting a progressive, local variation in phototropic or photo-chromic behavior from one edge to an area spaced therefrom com-prising:
forming an oxide glass body from a glass making batch, said body containing throughout its volume at least 0.005 vol. %
of at least one silver halide selected from the group consisting of silver chloride, silver bromide, silver iodide, and mixtures thereof, subjecting said glass article to a heat treatment, said heat treatment consisting of subjecting one area of such a lens to a temperature above the strain point but below the soften-ing point thereof for a time period sufficient to grow silver halide particles having an average linear dimension of about 50 nm, substantially progressively varying the temperature of heat treatment across said lens from said one edge to said area spaced therefrom in such a manner as to form silver halide particles of progressively smaller average linear dimension to thereby produce a lens characterized by a local variation in phototropic or photochromic behavior.
forming an oxide glass body from a glass making batch, said body containing throughout its volume at least 0.005 vol. %
of at least one silver halide selected from the group consisting of silver chloride, silver bromide, silver iodide, and mixtures thereof, subjecting said glass article to a heat treatment, said heat treatment consisting of subjecting one area of such a lens to a temperature above the strain point but below the soften-ing point thereof for a time period sufficient to grow silver halide particles having an average linear dimension of about 50 nm, substantially progressively varying the temperature of heat treatment across said lens from said one edge to said area spaced therefrom in such a manner as to form silver halide particles of progressively smaller average linear dimension to thereby produce a lens characterized by a local variation in phototropic or photochromic behavior.
8. The method of claim 7 in which the glass lens is made from a batch having the following oxide analysis:
Si02 53.0 A1203 10.5 Zr02 2.0 Li20 2.1
Si02 53.0 A1203 10.5 Zr02 2.0 Li20 2.1
9. The lens of claim 8 in which the heat treatment is characterized by a curve substantially identical to that shown in Fig. 2.
10. The process of claim 9 in which the temperature at said portion spaced from the edge does not exceed the strain point of the glass.
11. A process according to claim 9 in which lens consists of a glass matrix selected from the group consisting of silicate, boro-silicate, phospho-silicate, and containing at least 0.005 vol. % of molecularly dispersed silver and at least one halogen selected from the group consisting of chlorine, bromine and iodine.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US62468875A | 1975-10-22 | 1975-10-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1061618A true CA1061618A (en) | 1979-09-04 |
Family
ID=24502936
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA251,044A Expired CA1061618A (en) | 1975-10-22 | 1976-04-26 | Photochromic gradient lenses |
Country Status (13)
| Country | Link |
|---|---|
| JP (1) | JPS595538B2 (en) |
| BE (1) | BE841167A (en) |
| BR (1) | BR7604007A (en) |
| CA (1) | CA1061618A (en) |
| DE (1) | DE2617665C2 (en) |
| ES (1) | ES450600A1 (en) |
| FR (1) | FR2328668A1 (en) |
| GB (1) | GB1548744A (en) |
| IT (1) | IT1058165B (en) |
| MX (1) | MX143311A (en) |
| NL (1) | NL182395C (en) |
| SE (1) | SE425032B (en) |
| ZA (1) | ZA762173B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4160655A (en) * | 1977-12-19 | 1979-07-10 | Corning Glass Works | Process for making gradient photochromic glass articles |
| JPH041837U (en) * | 1990-04-17 | 1992-01-09 | ||
| JP2003231413A (en) * | 2002-07-22 | 2003-08-19 | Akiyoshi Sugimoto | Car |
| FR2923917B1 (en) * | 2007-11-16 | 2010-11-26 | Christian Dalloz Sunoptics | NOVEL TRANSPARENT OPTICAL SUBSTRATE, ITS OBTAINING METHOD AND ITS APPLICATION AS EYE |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2770922A (en) * | 1952-05-19 | 1956-11-20 | Pittsburgh Plate Glass Co | Radiation colorable chromium glass |
| US3419370A (en) * | 1965-11-22 | 1968-12-31 | Corning Glass Works | Method of producing a photochromic glass and resulting article |
-
1976
- 1976-04-12 ZA ZA762173A patent/ZA762173B/en unknown
- 1976-04-20 IT IT49092/76A patent/IT1058165B/en active
- 1976-04-20 SE SE7604520A patent/SE425032B/en not_active IP Right Cessation
- 1976-04-22 DE DE2617665A patent/DE2617665C2/en not_active Expired
- 1976-04-26 CA CA251,044A patent/CA1061618A/en not_active Expired
- 1976-04-27 BE BE166487A patent/BE841167A/en not_active IP Right Cessation
- 1976-04-28 GB GB17372/76A patent/GB1548744A/en not_active Expired
- 1976-04-28 JP JP51047928A patent/JPS595538B2/en not_active Expired
- 1976-05-03 MX MX164537A patent/MX143311A/en unknown
- 1976-05-04 FR FR7613214A patent/FR2328668A1/en active Granted
- 1976-05-20 NL NLAANVRAGE7605399,A patent/NL182395C/en not_active IP Right Cessation
- 1976-06-22 BR BR7604007A patent/BR7604007A/en unknown
- 1976-08-10 ES ES450600A patent/ES450600A1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| NL182395B (en) | 1987-10-01 |
| SE7604520L (en) | 1977-04-23 |
| NL182395C (en) | 1988-03-01 |
| GB1548744A (en) | 1979-07-18 |
| JPS595538B2 (en) | 1984-02-06 |
| FR2328668A1 (en) | 1977-05-20 |
| NL7605399A (en) | 1977-04-26 |
| DE2617665A1 (en) | 1977-04-28 |
| JPS5251412A (en) | 1977-04-25 |
| IT1058165B (en) | 1982-04-10 |
| BR7604007A (en) | 1977-06-28 |
| DE2617665C2 (en) | 1987-01-22 |
| FR2328668B1 (en) | 1979-04-20 |
| ES450600A1 (en) | 1978-01-16 |
| BE841167A (en) | 1976-08-16 |
| ZA762173B (en) | 1977-04-27 |
| MX143311A (en) | 1981-04-14 |
| SE425032B (en) | 1982-08-23 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4358542A (en) | Photochromic glass suitable for microsheet and simultaneous heat treatment and shaping | |
| US4240836A (en) | Colored photochromic glasses and method | |
| CA1190426A (en) | Very fast fading photochromic glass | |
| EP0164884B1 (en) | Ultraviolet absorbing photochromic glass of low silver content | |
| US4130437A (en) | Photochromic glasses suitable for simultaneous heat treatment and shaping | |
| JPS6351981B2 (en) | ||
| US4168339A (en) | Photochromic microsheet | |
| US4290794A (en) | Method of making colored photochromic glasses | |
| JPS63123836A (en) | Photochromic glass composition for lightweight lens, photochromic glass of compoisiton and photochromic lens element | |
| CA1091024A (en) | Preparation of photochromic gradient lenses | |
| CA1050273A (en) | Process for making multifocal photochromic ophthalmic lens | |
| US4036624A (en) | Heat treatment method for making photochromic gradient lenses | |
| US3801336A (en) | Lead borosilicate optical glass adaptable to fusion with photochromic glass to produce multifocal lens | |
| EP0452640B1 (en) | Method of coloring photochromic glasses | |
| US4101302A (en) | Photochromic gradient lenses | |
| CA1061618A (en) | Photochromic gradient lenses | |
| CA1083821A (en) | Ion exchangeable segment glass | |
| GB2045230A (en) | High index opthalmic glasses | |
| US3975093A (en) | Photochromic multifocal lenses | |
| US3957499A (en) | Fast-fading index-corrected photochromic glass compositions | |
| US4080051A (en) | Preparation of photochromic gradient lenses of cosmetically improved color | |
| GB2063852A (en) | Coloured photochromic glasses | |
| US4092174A (en) | Photochromic glasses | |
| US4076395A (en) | Preparation of photochromic gradient lenses of improved color | |
| CA2103831A1 (en) | Multipurpose photochromic brown glasses |