JPH01230452A - Production of colored photochromic glass - Google Patents

Abstract

PURPOSE: To make it possible to generate some of hues of a specified color tone having excellent thermal stability and to attain desired visual sensation transmittance by at least partly chemically removing the colored surface layers formed by subjecting transparent photochromic glass products to a heat treatment in a reducing gaseous atmosphere, thereby changing the colors of the colored surface layers.

CONSTITUTION: The transparent photochromic glass products contg., for example, silver halide crystals as a photochromic component and lead oxide as an indispensable component are heat treated at the temp. higher than the distortion point of the glass in the environment of the reducing gas, such as H₂, thereby, the glass products are at least partly provided with the colored surface layers. Next, the colored surface layers are at least partly chemically removed, thereby, the colors of the colored surface layers are changed and the selectively colored photochromic glasses are obtd.

COPYRIGHT: (C)1989,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing colored photochromic glass.

Glasses, variously called photochromic glasses or phototropic glasses, have their origin in US Pat. No. 3.2011.860. As explained in this patent, photochromic glasses darken, or change color, when exposed to actinic radiation, typically ultraviolet radiation, and return to their original transmittance when removed from the actinic radiation. This type of glass is commonly used in eyeglasses. For example, photochromic eyeglass lenses have a transmittance of greater than 90% indoors, but when the wearer goes outdoors into sunlight, they quickly darken and their transmittance drops to less than 50%. When the wearer returns indoors, the lenses fade to their original transmittance.

Although other photochromic components are known, silver halide crystals, especially A
Crystals of gCρ and AgBr are used as photochromic components. Similarly, basic glass compositions have been studied with some success, but commercially available glasses contain significant amounts of silica. Generally, commercially available glasses have a basic composition within an alkali metal aluminoborosilicate system. U.S. Patent No. 3,208,8
No. 80 describes the above basic composition containing silver halide crystals as a preferred example.

CoQ in the glass composition to color the glass.

Nip, Cr203, Cub, Fe203.

■ It is well known to add transition metal oxides such as 205 and M n O and rare earth metal oxides such as Pr, 403 and Er2O3. Spectacle lenses colored by this method, including photochromic lenses, are currently commercially available. However, the coloring method described above requires the careful addition of a precisely defined amount of colorant in order to uniformly color each lens and each glass melt. Furthermore, in the above coloring method, it is necessary to strictly control the redox conditions during melting and shaping of the glass. Therefore, it is clear that a method that can impart a desired color to glass without adding a colorant is very attractive in practice. It will be appreciated that where ophthalmic lenses are being made, such coloring methods must not adversely affect the photochromic properties of the glass. Additionally, if the lens must be chemically or thermally strengthened, the tinting must be durable enough that it remains in the glass even after the glass has been subjected to said toughening. .

U.S. Patent Nos. 3,892,5.82 and 3.920
, No. 4G3 relates to a method for coloring photochromic glass using silver halide crystals as a photochromic component. In the former case, a glass product having the composition contained in the above-mentioned U.S. Pat. No. 3,208,860 is heated in a reducing atmosphere, which is generally an atmosphere containing hydrogen, at 300°C for about 15 minutes to 600°C for about 4 to 5 minutes. It is disclosed that heat treatment is performed. In this method, strict adherence to the above heat treatment parameters is required due to the coloring mechanism provided.

The above-mentioned US Pat. No. 3,892,582 states that in almost all photochromic glasses there is an inherent excess of photochromic components. Therefore, an excess of silver halide crystals is present in the glass composition of this patent.

The reduction method of this patent is designed to act on the photochromic component, preferably only on the excess of the photochromic component so that the photochromic properties are not impaired.

If a slight reduction in photochromic properties is tolerated, it is permissible to reduce some of the active photochromic components. However, it is stated that long-term heat treatment at high temperatures should be avoided because it reduces the photochromic component to the extent that the photochromic properties of the glass are lost. Furthermore, it is stated that the use of reducing conditions so severe as to reduce the oxides in the base glass composition should be avoided.

No. 3,920,463 relates to the same reduction method, but in that patent's method the reduced glass is then exposed to ultraviolet light. It is stated that this exposure produces a darker and deeper coloration than that obtained by reduction treatment alone.

U.S. Pat. No. 4,118,214 discloses an improved method for making polychromatic glass. Traditional methods for producing polychromatic glass consisted of two repetitions of exposure to high-energy or actinic radiation and subsequent heat treatment in air.

In the method of this patent, instead of a second exposure and heat treatment in air, at least 350
The heat treatment is carried out at a temperature lower than the strain point of the glass.

The coloration of polychromatic glass is caused by the presence of color centers in the glass. The center of this color is AgCρ.

It is a microcrystal of an alkali metal fluoride (generally NaF) containing a silver halide selected from the group consisting of AgBr and AgI, and metallic silver is precipitated inside or on the surface of this microcrystal. This multicolored glass is N a'z O
, Ag, F, and a halide selected from the group consisting of CΩ, Br, and I, and may contain one or both of A, QzO3, and ZnO as optional components.

Although other reducing agents may be used, it is stated that a hydrogen atmosphere is the most effective reducing environment. It is stated that the use of temperatures at or above the strain point of the glass should be avoided as this destroys the color centers.

U.S. Pat. No. 4,125.4 (15) discloses a red glass containing silver halide, which is made under reducing melting conditions and exhibits slight photochromic properties. The photochromic properties of the glass are insufficient to make it practical for photochromic products.If heat treatment is used to enhance the photochromic properties of the glass, the red coloration of the glass is generally destroyed.

Another type of silver halide-containing photochromic glass has also recently been developed which exhibits improved darkening and fading properties. Such a glass family or U.S. Patent No. 4,19
No. 0,451.

Efforts have also been made to develop photochromic lenses that darken only at the top and therefore exhibit gradient darkening characteristics. Examples of methods for making such lenses are U.S. Pat. No. 4,036,624, U.S. Pat. [Seen in issue i55.

As is clear from the descriptions of the above patents, coloring of photochromic and polychrome glasses is achieved by reducing silver ions to metallic silver.

Such coloring takes place at relatively low temperatures.

That is, a temperature below the strain point of the glass is used. Alternatively, coloration can also be achieved by very short exposure to higher temperatures.

U.S. Patents No. 3,892,582 and 3.9, supra.
The yellow coloration observed when heat treating photochromic glasses under reducing conditions such as those described in No. 20,463 is due to absorption bands created by metallic silver precipitated in the glass during heat treatment. In other silver-containing glasses without precipitated phases, this silver absorption band appears as an absorption peak at about 390 nm in the violet region of the spectrum. Nos. 3,892,582 and 3,9, which contain silver halide precipitates in addition to the matrix glass.
It has been reported that the reduction-fired photochromic glass of No. 20.4133 has an absorption peak in the blue region of about 430 to 4 EiOnm.

The hue and intensity of the coloring in the glasses of the two US patents probably depends on the position and intensity of the absorption peaks produced by the heat treatment. The deepest yellow color was produced by the strong absorption peak present between 430 and 460 nm;
The same basic absorption peak was initially observed after mild heat treatment.
Since it appeared weakly around nm, it is thought that this caused the pale pink color.

Although the conventionally used reduction heat treatment described above is a simple method for imparting surface coloring to photochromic glass, it is possible to obtain only a very limited range of colors. Attempts to increase the coloration, for example by using more intense heat treatments, simply shift the fundamental absorption peak toward the violet direction, resulting in a glass with a stronger yellow coloration.

Food and Drug Administration
Since the Japanese government has established strength standards for eyeglass products, glass products for eyeglasses must be thermally strengthened or chemically strengthened to pass the standards.

Thermal strengthening consists of heating a glass product to or near the softening point of the glass and then rapidly cooling it. Chemical strengthening is the process of strengthening a glass product (generally containing alkali metal ions) at a high temperature below the strain point of the glass with alkali metal ions that are larger in size than the ions in the glass product (generally having a larger ionic radius). ) for a sufficient period of time to cause the large ions to migrate to the glass surface and displace the small ions present in the glass. This ion exchange reaction is generally carried out for several hours, often overnight.

All of these strengthening methods have the side effect of altering the coloration produced in the glass by the reduction of silver ions. Of course, such adverse effects can be eliminated by strengthening the glass before subjecting it to the reduction heat treatment. However, since glass strengthening is currently performed just before the lens is inserted into the customer's frame, it is contrary to current production flow to perform the strengthening prior to the reductive heat treatment. Furthermore, the heating during the reduction heat treatment alters the strength produced by thermal or chemical strengthening.

In the past, eyeglass wearers have desired to produce glasses with a variety of shades. For example, sportsmen use so-called user glasses (SL+OOTER'S) with a yellow tint for use as prescription and non-prescription lenses.
glass). The utility of such products in reducing haze and glare observed by the wearer is 111 by keeping the color tone within a narrow range of transmittance.
It will be done. The ideal product would have a tint with tightly controlled transmission in a glass exhibiting photochromic properties, and the tint would exhibit excellent thermal stability. That is, the color tone will be hardly affected by a long heat treatment at a temperature near the strain point (=I) of the glass or a short time heat treatment at a temperature near the softening point of the glass.

Another desirable product would be a photochromic ophthalmic lens that exhibits a fixed negative slope with -like photochromic darkening properties. Such lenses darken when exposed to actinic radiation and fade when removed from actinic radiation, but also have a fixed negative gradient or other color pattern selectively placed on the lens. will have. This fixed negative gradient or color pattern does not change as lighting conditions change. It is therefore possible to obtain a lens that exhibits photochromic darkening in all lens parts and also exhibits a negative gradient that is always perceptible to the observer. Important requirements for such lenses are that they have relatively-like phototalomic darkening performance, that they have a fixed negative slope or other color pattern, and that optical power aberrations must be controlled during lens manufacturing. should not occur. Of course, regarding both sunglass products and prescription eyeglass lens products,
Manufacturing methods that risk producing changes in surface smoothness and curvature that adversely affect the optical properties of the lens are unsuitable.

It is an object of the present invention to produce several shades of a constant color tone exhibiting excellent thermal stability, i.e. color differences primarily due to changes in luminous transmittance or to some extent due to shifts in chromaticity, into a single photochromic material. The object of the present invention is to provide a method for producing a glass composition.

Another object of the present invention is to provide a method for producing a photochromic glass that exhibits a surface coloring different from the yellow tone of conventional photochromic glasses.

Yet another object of the present invention is a method for producing in a single photochromic glass composition several shades of yellow color exhibiting excellent thermal stability and for adjusting the inkstone transmittance of the glass to a desired level. Our goal is to provide the following.

Yet another object of the present invention is to provide a method for producing a photochromic glass substrate having relatively constant color coordinates but with a transmittance gradient along its surface, and whose color tone exhibits excellent thermal stability. There is a particular thing.

Yet another object of the present invention is that one side is colored;
Another object of the present invention is to provide a method for manufacturing a photochromic glass lens semi-finished product whose coloring exhibits excellent thermal stability.

Yet another object of the present invention is to provide a method for producing photochromic glass bodies having a coloration exhibiting excellent thermal stability and which significantly absorb radiation at wavelengths shorter than about 450 nm.

Yet another object of the present invention is to provide a method for producing photochromic glass substrates containing conventional colorants in the composition in which the color tone is changed by the colorant to a color tone exhibiting excellent thermal stability.

Yet another object of the present invention is to provide a method for manufacturing a selectively colored photochromic glass lens comprising a portion with a surface coloration and another portion with no surface coloration or a different surface coloration. It's about doing.

The present invention provides a method of producing a surface coloration in transparent photochromic glass in addition to, or in place of, the relatively pure yellow coloration produced by the use of conventional reductive heat treatments. As explained above, in photochromic glass, the above-mentioned reduction heat treatment is generally effective in producing only the basic absorption peak of metallic silver in the glass, and although the basic absorption peak changes in intensity and wavelength, it is generally around 430 nm. ~4[fOnm].

In the present invention, the heat treatment is carried out in a reducing gas environment at a temperature above about 200'C for a sufficient period of time so that one or two absorption peaks at longer wavelengths than the fundamental absorption peak of metallic silver in the glass are removed. At wavelengths above, the luminous transmittance of the glass surface layer is lower than that of the untreated glass surface layer. Such a decrease in luminous transmittance is a relatively wide-ranging decrease in transmittance in the visible region at longer wavelengths than the fundamental absorption peak of metallic silver, depending on the reducing conditions and glass composition used. or by the generation of a relatively narrow new absorption band in the visible region.

In a first embodiment of the present invention, a glass containing silver halide crystals as a photochromic component and lead oxide as an essential component is cooled to a temperature higher than the strain point of the glass in a strongly reducing gas environment, preferably slowly. It has been found that the transmittance can be reduced over a relatively wide range in the visible region by heat treatment at temperatures near or somewhat higher. At such high temperatures, not only the silver ions in the glass are reduced to metallic silver, but also the lead ions are reduced to metallic lead. It is thought that this metallic lead coats the silver particles or forms an alloy with the silver particles.

In the first embodiment, the photochromic glass contains at least one of AgCIJ, AgBr and Agl as a photochromic component, and also contains lead oxide which gives the desired color when reduced according to the method of the invention. If so, the method of the present invention can be applied regardless of the basic composition of the glass. For example, in U.S. Pat. No. 3,548,060, Ag2O3-B2O
Glasses having a base composition within the 3-RO system are disclosed.

That is, the glass of this patent has a weight percentage of 30 to 86%.
of B2O3, 2 to 35% Ag2O3 and 12 to 45% alkaline earth metal oxide. U.S. Pat. No. 3,703,388 discloses glasses having a basic composition within the La203-B2O3 system.

That is, the glass of this patent has a weight percentage of 15 to 75%.
of La2O3 and 13 to 65% of B2O3. φ U.S. Patent Section 3,834.912 has pbo-B2
Glasses having a basic composition within the 03 series are disclosed.

That is, the glass of this patent has a weight percentage of 14.2 to 4.
8% B2O3, 29-73% pbo.

0-15% alkaline earth metal oxides and O-2
It consists of at least one of 3% ZrO2, Ai)z03 and ZnO. U.S. Patent No. 3.878,43
No. 6 discloses a glass having a basic composition within the R20-Ag2O3-B205 system.

That is, the glass of this patent contains at least 17% by weight.
% P2O5, 9 to 34% Ag2O3, up to 40% SiO2, up to 19% 8203 and at least 1
Consisting of 0% alkali metal oxide. U.S. Patent No. 3,9
No. 57,498 has R20-A, Q 203-8i02
A glass having a basic composition within the system is disclosed. That is, the glass of this patent consists of 13-21% alkali metal oxide, 17-25% Ag2O3 and 45-56% 5i02 by weight. Furthermore, as previously mentioned in the discussion of US Pat. No. 3,208,860, currently commercially available photochromic glasses have a base composition within the alkali metal aluminoborosilicate system. This patent states that the preferred glass is 4 to 2% by weight.
626 Ag2O3; 4 to 2[i%(')B203;
40-76% (7) Si02; and 2-8% (
7) Li20.4-15% Na20.6-20%
20.8-25% Rb2O and 1o-30
% CS At least 1 selected from the group consisting of 20
A glass comprising alkali metal oxides of various species is disclosed. The glass contains minimum effective amounts of at least one of chlorine, bromine and iodine of 0.2%, 0.1% and 0.08%, respectively, based on chemical analysis and at least Contains the minimum effective amount of silver.

The minimum effective amount of silver is 0 when the available halogen is chlorine.
．． 2%, 0.05% if the available halogen or bromine but less than 0.08% iodine is present, and 0.03% if at least 0.08% iodine is present. If clear glass is desired, the amount of silver is 0.7%
Must be below, and the total of the three types of Haloken must be 31
'JAL must be below 0.6%. The total amount of each of the above basic glass components, silver and halogens must be at least 85% of the total composition.

The amount of lead required to have the desired effect on transmittance when the glass is treated according to the method of the invention is at least 0.5%, expressed as PbO, and greater than 1%. was found to be the most preferable. Colors ranging from pale yellow to almost orange can be produced, and tight control of the color produced and the luminous transmittance of the glass is possible, so that the coloration can be produced with good reproducibility.

The actual color and luminous transmittance produced depends somewhat on the glass composition, especially the PbO content, but is primarily a function of the parameters of the reduction process.

No. 3,892.582 and 3.92, supra.
Contrary to the content of No. 0,403, the photochromic properties of the glass do not significantly deteriorate unless the reduction treatment temperature significantly exceeds the annealing point of the glass for a considerable period of time. Judging from the experimental results, it is approximately 5% lower than the annealing point of glass.
Reduction treatments at temperatures above 0° C. for longer than about 1 hour appear to have an adverse effect on the photochromic properties of the glass.

A pure hydrogen atmosphere was found to be the most effective environment in terms of reaction rate. Therefore, the reaction appears to be based on a diffusion effect, with the coloring starting at the surface and gradually moving into the interior. Because of this phenomenon, the longer the treatment time or the higher the treatment temperature, the deeper the coloring penetrates into the glass. Furthermore, due to the strong temperature dependence of the above phenomenon, a negative gradient can be created along the glass surface. Although pure hydrogen is preferred from a reaction rate standpoint, other reducing environments such as -carbon oxides, cracked ammonia, and mixtures of hydrogen and nitrogen can also be used. Generally, the glass is exposed to a reducing gas atmosphere at a specified temperature for a sufficient time to reduce the lead ions in the glass to metallic lead and produce metallic particle color centers. This exposure time depends on the composition of the glass, the environment used and the temperature used. For example, if pure hydrogen is used, exposure as short as a few minutes is sufficient at higher temperatures, but at temperatures near the strain point of the glass (=J) exposures of several hours are required. Additionally, the depth of color penetration in the glass is of course a factor that must be taken into account.This depth of color penetration is governed by the law of diffusion.

The method of the invention allows the production of semi-finished products. For example, one side of an eyeglass lens blank may be finished (grinded and polished to an appropriate degree), and the entire blank or the finished side of the blank may contain metallic lead particles that impart the desired coloration to the blank. Exposure to a reducing environment for a sufficient period of time to form an integral surface layer. The unfinished surface of the blank is then ground to obtain the final degree. Any coloring that develops on the unfinished surface is removed during finishing of that surface, but the final lens retains the coloring on the originally finished surface.

Since the present invention aims to produce a photochromic eyeglass lens, that is, a eyeglass lens that exhibits reversible luminous transmittance, the present invention preferably reduces the amount of actinic radiation when the eyeglass wearer is exposed to sunlight. A highly absorbent surface layer is formed only on the back side of the lens to avoid absorption.

The method of the present invention is suitable for glasses with very high PbO contents (e.g., U.S. Pat.
% PbO), but the coloration obtained in glasses with high PbO content is
This is no different from the coloring obtained in glasses with much lower O contents. However, glass is at least 0.
It is necessary to contain more than 5%, preferably more than 1%, of PbO, and also to contain silver halide crystals as a photochromic component. U.S. Patent No. 3,20
For the preferred glass compositions of No. 8.8GO, the maximum PbO content generally does not exceed about 10%.

As mentioned above, the method of the present invention is useful for producing molded articles in which only a portion of the surface is colored or a color gradient is created along the surface.

U.S. Pat. No. 4,072,490 discloses an apparatus and method that can be easily modified to assist in the method of the present invention.

Furthermore, the method of the invention allows the production of colored photochromic glass bodies that are highly UV-absorbing. Such glasses are particularly useful when prescribed medically as ophthalmic lenses for conditions such as retinitis pigmentosa, where protection from intense lighting, especially ultraviolet light, is necessary. A two-step process is required to obtain the colored photochromic glass substrate. First, photochromic glass received the No. 3 U.S. patent.
892,582 in a reducing atmosphere. That is, the glass is fired under firing conditions (firing temperature and firing time) sufficient to reduce Ag+ ions to metallic silver. Preferably, a firing temperature below the strain point of the glass is used. after that,
The treated glass is fired in a reducing environment at a temperature near or above the annealing point of the glass for a time sufficient to reduce the lead ions to metallic lead in a thin surface layer. As a result of this continuous firing of the glass at different temperatures, a layer containing metal lead particles is formed on the layer containing metal silver particles. The metallic silver particles cause a sharp cut in the transmittance at a wavelength of approximately 45°nl11, resulting in strong absorption from the blue region of the visible spectrum to the ultraviolet region. This is why glass is particularly suitable as a UV filter.

However, since the human eye is most sensitive to wavelengths of approximately 555 nn+ (yellow-green), even this absorption by metallic silver particles cannot reduce transmission in the visible region of the spectrum. In contrast, metallic lead particles generally absorb in the visible spectrum. Therefore, the luminous transmittance exhibited by the glass is determined primarily by the thickness of the layer containing metal lead particles.

In summary, a first embodiment of the invention seeks to produce a photochromic glass product, in particular a spectacle lens, having an integral surface layer containing metallic silver particles and metallic lead particles on its back side. This first method of the invention makes it possible to produce the above-mentioned glass products, which absorb strongly in the ultraviolet region of the spectrum and exhibit various shades, without resorting to hot glass forming methods.

In a second embodiment of the present invention, a relatively narrow absorption band is produced on the longer wavelength side than the basic absorption wavelength of silver by subjecting silver halide-containing photochromic glass to a reduction heat treatment under appropriate thermal conditions. It has now been found that it is possible to obtain a colored photochromic glass which exhibits a surface coloration, for example orange, red, violet or blue, in the undarkened state. Such results are obtained by using a heat treatment temperature range that is somewhat lower than that conventionally used in order to minimize photochromic phase (silver halide) melting during the reduction process. Other factors that influence the results are the composition and thermal history of the photochromic glass starting material used in this coloring process.

The extensive surface coloration seen in photochromic glasses produced according to the second method of the invention is due to the strong absorption bands that develop on the glass surface during heat treatment. This absorption band is on the longer wavelength side than 480nm, and is often at 510nm.
~580 nm. This absorption band shifts the color of the glass from yellow to orange, red, purple or blue. Thus, the surface-colored photochromic glass obtained by the method of the present invention exhibits strong absorption only at 430 to 4 GO nm, and is different from conventional surface-colored photochromic glasses that exhibit relatively weak absorption at the wavelengths necessary for producing non-yellow glass. It is something.

In terms of spectral transmittance characteristics, conventional surface-colored photochromic glass products exhibit an absorption peak located to the left of line CB in FIGS. 7 to 9, at least in the shape of commonly used spectacle lenses. This is most clearly shown in FIG. As shown in FIGS. 7 and 9, the present invention provides a surface-colored photochromic glass product with an absorption peak located to the right of line CB.

In particular, a second embodiment of the present invention provides a silver halide-containing photochromic glass article under reducing conditions at about 450°C.
There is provided a surface-colored photochromic glass product manufactured by a method comprising heat treatment at a temperature of: The heat treatment is continued for a sufficient period of time to develop specific light absorption properties in the glass article. This light absorption characteristic is generally 430 to 460 at least in one cross section of the non-darkened state of the glass product after the above-mentioned reduction heat treatment.
It has such a characteristic that it exhibits a spectral transmittance curve having at least one absorption peak on the longer wavelength side than the fundamental absorption wavelength of silver observed in nm. Therefore, the peak produced by the reduction heat treatment is generally in the spectral transmittance region to the right of line CB in FIG.

Accordingly, surface-tinted photochromic glass articles such as those described above are prepared by preparing silver halide-containing photochromic glass articles under reducing conditions at temperatures below about 450° C. for a period sufficient to produce at least one absorption peak having the characteristics described above. Obtained by heat treatment.

The above light absorption properties were first produced in photochromic glasses of the type disclosed in the above-mentioned US Pat. No. 4,190,451. However, this novel light absorption effect is not limited to such glasses, and has also been observed in other types of photochromic glasses that have been subjected to reduction heat treatment in the manner described above.

The unusual coloring effect observed in the photochromic glass obtained by the second method of the present invention is believed to be caused by the chemical reduction of silver in contact with silver halide microcrystals in the region very close to the glass surface; The observed color appears to be determined by the shape and arrangement of metallic silver on the microcrystals. This means that when a certain reducing heat treatment is used, a particular photochromic glass will produce any of a number of different absorption peaks depending on the method originally used to produce the silver halide crystallites in the glass. This is consistent with the experimentally observed fact that

Furthermore, since the surface coloring imparted to the photochromic glass by reduction heat treatment is sufficiently close to the gas surface, a portion of the colored glass surface can be selectively removed without changing the optical properties of the surface. It has been found that it can be done.

That is, the coloration produced by reductive heat treatment is in a very thin layer, typically about 10 to 100 microns thick, on the treated lens surface, and removal of this surface layer by chemical means has no effect on the refractive power or surface quality of the lens surface. It was found that there were no significant negative effects.

Accordingly, the present invention further provides a method for treating surface-colored photochromic glass products produced by heat treatment in a reducing gas environment as described above to obtain selectively colored glass products. This method chemically removes selected portions of the colored surface layer, reducing the apparent color of that layer.
It therefore consists of changing the apparent color of the product. The colored surface layer that is chemically removed from the lens has a colored pattern,
Preferably, it can be chosen to provide a negative gradient varying from a relatively strong color at the top of the lens to achromatic at the bottom of the lens. The portion of the colored surface layer that is chemically removed can also be controlled in terms of thickness, so that the color change consists of both a limited reduction in color intensity and a complete removal of color.

Furthermore, a known glass colorant may be included in the glass composition if necessary. Of course, the combination of colorants and the coloration produced by the method of the invention produces a variety of shades and shades.

Corning Glass Work
s, Corning.

The first method of the present invention will be described below using three types of photochromic glasses commercially available from Co., Ltd. (New York) for use in eyeglass lenses. The approximate composition of each glass is shown in weight percent in the table below. Glass A, B and C
are sold under the names Corning 8097, Corning 8111 and Corning 8105, respectively.

The table below also shows approximate values for the softening point, annealing point and strain point of each glass.

A B C 8i 02 55.8 56.4[i
55.52B2o316.4 1.8.1
5 1G, 10Al) 2o38.9G,
19 8.90L i 2 0 2. f
li5 1.81 2.65N a 2 0
1.85 4.0g 1.8
3 to 20 0.01 5.72
-B a O [i, 7 B,
70Ca OO,2-- P b O5,05,04 Z r 02 , 2.2 4.99
2. O7Ag 0.1B
0.207 0.175Cu OO,0350,
0060,0128CL) 0.24
0.1G6 0.125B r
O, 1450, 1370, 50F
O,190,2Ti02
2.07 - Softening point 675° 662°
675° Annealing point 511° 500' 510
'Strain Points 473° 468° 475° Two circular lens blanks with a diameter of about 70 mm and a thickness of about 6n++n were pressed from glass C, and each was divided into four parts and polished to a thickness of 3+++m. Two of the eight samples thus obtained were placed in a tube electric furnace connected to a source of pure hydrogen gas. The electric furnace was purged with nitrogen gas and then with pure hydrogen gas, and then the sample was heated at 415°C, 435°C, and 460°C in a pure hydrogen gas stream with a pressure slightly higher than atmospheric pressure and a flow rate of about 10 cc/sec. ℃ and 525 ℃ for 30 minutes. The sample was taken out of the electric furnace and its negative side was polished to a thickness of 2+++ m. One sample was then chemically strengthened. This chemical reinforcement consists of 60% by weight KNO3 and 40% by weight NaNO3.
This was done by immersing the sample in a 400°C molten salt bath for 16 hours.

The color and photochromic properties of the undarkened state were measured using a conventional tristimulus colorimeter and research exposure/photometer equipment. Store each sample at room temperature, i.e. approximately 20-25°C.
Exposure to UV light for 20 minutes followed by removal from UV light for 5 minutes. Table 1 below shows the luminous transmittance exhibited by each sample, including To, TD2o and TF5.
before darkness, after 20 minutes of darkness, and 5 minutes, respectively.
It represents the luminous transmittance after fading for minutes. Table 1 also shows the chromaticity coordinates (x, y) of each sample in the non-darkened state.

Figure 1 shows the chromaticity coordinates of each sample in the non-darkening state on a chromaticity diagram, and Figure 2 shows the chemical strengthening after thermal bleaching, that is, after heating at 97°C for 35 minutes. This figure shows the spectral transmittance curve of the sample.

As is clear from the comparison of Example 4 and the other Examples in Table 1, FIGS. 1 and 2, there are significant differences between Example 4 and the other Examples. This difference is particularly clearly shown in the spectral transmittance curves in FIG. The temperature of 525° C. (above the annealing point of Glass C) is sufficiently high to cause reduction of lead ions in addition to reduction of silver ions. Glass heat-treated at this temperature absorbs light in the entire visible region, and does not have a sharp absorption band due to metallic silver particles having a peak on the wavelength side longer than 450 nm. In addition, the color shifts toward green due to the reduction of lead ions.

The chemical strengthening method does not have an adverse effect on the method of the present invention, as evidenced by the comparison of the color and photochromic properties exhibited by the chemically strengthened samples with those exhibited by the non-chemically strengthened samples. do not have.

A circular lens blank having the same diameter and thickness as the circular lens blank of glass C was pressed from glass A, divided into four parts, and ground and polished to a thickness of about 3 mm. After that, the sample was heated in the same manner as above for 400 min in a pure hydrogen gas stream.
℃, 455°C, 480°C and 530°C for 0.5 hour.

One side of each sample was ground to a thickness of approximately 2 mm, and then the color and photochromic properties of each sample were measured using the same method and equipment as in Section 1.

Each sample was exposed to UV light for 20 minutes at room temperature and then removed from UV light for 5 minutes. Table 2 below shows the luminous transmittance (To) before darkening exhibited by each sample.
) and chromaticity coordinates (x, y).

Table 2 Example No. Heat treatment temperature T. x y5
400℃ 65.9 0.4080 0.39546
455°CGo, 9 0.44G7 0.442774
80°C5B, 5 0.4153 0.4190853
0°C27, 80, 40490, 4063 Figure 3 shows the spectral transmittance curves of each sample in the non-darkening state, and this Figure 3 shows the spectral transmittance curves of the samples that have not undergone the above-mentioned reduction heat treatment. is also shown.

As is clear from Table 2, the color change that occurs in the temperature range from 48°C to 530°C is relatively small, but the change in luminous transmittance is large. The transmittance curve of the glass at 455 °C and 455 °C shows a strong absorption peak at about 450-500 nm due to the presence of silver particles. In the glass treated with higher processing temperatures, this absorption peak disappears and is replaced by Peakless absorption occurs over the entire visible wavelength range, and this absorption decreases with increasing wavelength.Therefore, at a processing temperature of 480 °C (slightly higher than the strain point of glass A). The traces of absorption peaks seen in the transmittance curve of certain glasses may be removed by increasing the processing time.

Circular lens blanks were pressed from glass A and glass B in the same manner as above, divided into four parts, and polished to a thickness of 2 mm. 5. Samples obtained using the same apparatus and method as described above were heated in a stream of pure hydrogen gas at a temperature of 520°C, i.e. approximately 50°C above the strain point of the glass. 1.0.
Baked for 20 and 40 minutes. The luminous transmittance (To
), chromaticity coordinate (x.

y) and color purity (%) were measured using the same equipment and method as above. The results are shown in Table 3 below.

FIG. 4 shows the spectral transmittance curves of the glasses of Examples 9 to 12, and FIG. 5 shows the spectral transmittance curves of the glasses of Examples 13 to 16.

Examples 9 to 12 (lead-containing glass) and Examples 13 to 16 (
As is clear from the comparison of lead-free glass (lead-free glass), there are three major differences between the two:

(a) In lead-free glass, the silver absorption band in the spectral transmittance curve does not disappear even after being fired for a relatively long time.

(b) Lead-free glass shows only a very small improvement in transmittance even after firing for a relatively long time.

(C) Although lead-free glass exhibits fairly large changes in chromaticity, its luminous transmittance changes relatively little.

These differences highlight the profound effect that the reduction of lead ions to metallic lead particles has on the color and transmittance of the glass. The data in Table 3 and the spectral transmittance curves in FIG. 5 demonstrate that the method of the present invention allows for tight control of the tint produced in glasses containing silver and lead.

The back surface of a glass C lens blank was ground and polished to a desired curvature, resulting in a semi-finished lens. This lens semi-finished product was fired in a pure hydrogen atmosphere using the following firing schedule to obtain a colored lens semi-finished product.

(a) 22 hours at 420°C and 1 hour at 560°C (Example 17).

(b) 4GO℃te 22 hours and 560℃te 0.5
Time (Example 18).

Thereafter, the front surface was ground and polished to obtain a lens with a thickness of about 3 mm. In the resulting lens, all the coloring is provided by a thin layer on the back. The photochromic properties of the glass are therefore unaffected.

FIG. 6 shows the spectral transmittance curves of the glasses of Examples 17 and 1B. The glass of Example 17 is the glass of Example 18.
It blocks slightly more blue light than glass. Although this difference is at a temperature lower than the strain point of glass, 48
This appears to be because the prolonged treatment at 0'C was sufficient to reduce some of the lead ions to metallic lead and alter the absorption by metallic silver. In reduction, the double firing process resulted in strong absorption by the silver in the deep layers, which prevented the transmission of light with wavelengths shorter than about 450 nm. 2 times
The higher temperatures used for firing the glass decreased the overall luminous transmittance of the glass.

A second method of the invention, which provides a colored photochromic glass exhibiting a narrow absorption peak at longer wavelengths, is described below.

Process-induced absorption peaks are defined as absorption peaks caused by surface reduction of photochromic glasses as described herein.

No such peak is present in the parent photochromic glass from which the surface-colored photochromic glass is made. Therefore, a surface-colored photochromic glass is one in which the color of the surface is different from the color of the glass body (if the glass body has a color). This can be easily verified by comparing the spectral transmittance characteristics of the glass before and after removing the surface glass.

The peak position of the absorption peak is determined by its wavelength and intensity. In this case, the wavelength is the wavelength at which the light transmittance of the glass in the non-darkened state is minimum. However, multiple absorption bands with peaks may be so close together that one absorption peak appears only as a shoulder of another absorption peak.

In such cases, peak positions are determined according to conventional spectral analysis methods.

FIG. 8 shows the spectral transmittance curves of a series of surface-colored photochromic glass eyeglass lens blanks manufactured by the conventional method in a non-darkened state, and illustrates the absorption characteristics of the conventional surface-colored photochromic glasses. be. All of these lens blanks are made of Corning Code 8097 photochromic glass, which is commercially available from Corning Corporation as "Photogray (registered trademark)". They were prepared by heat treatment for 10 minutes at the various temperatures indicated.

As is clear from Figure 8, the surface-colored glass produced by the conventional method has a very slight absorption near 510 nm obtained by mild heat treatment, and a strong absorption shifted to the short wavelength side obtained by more intense heat treatment. It has absorption properties ranging from Slightly light-absorbing glasses produced by heat treatment at 300° C. exhibit a pink color, while more strongly light-absorbing glasses exhibit a yellow color.

As far as the prior art documents describe, these glasses do not exhibit significant absorption at wavelengths longer than 510 nm;
Moreover, it does not show a strong absorption peak in the range of 460 to 510 nm. Therefore, the absorption peak exhibited by these glasses, whose position is indicated by the point of minimum transmittance, is limited to the region to the left of line CB in FIG. 8, and the color of the glass is therefore limited. This line CB will be referred to as “color barrier” (
color barrier).

Quite different from the above, according to the method of the invention obtained = 4
4 - The glass products shown exhibit strong absorption bands in the green and yellow regions to the right of the color barrier. FIG. 7 shows the spectral transmittance curves of several such surface-tinted glass products in the undarkened state, illustrating the various different absorption characteristics exhibited by the glass products. Similar to the color barrier CB in FIGS. 8 and 9, the color barrier CB in FIG. is a straight line connecting the points. The absorption characteristics exhibited by the glass products of the invention vary from the strong absorption peak in the blue region to the right of the color barrier giving the orange coloration (curves 1 and 5 in Figure 7) to the width of the yellow region giving the blue coloration. It varies within a range up to a broad absorption peak (curve 4 in Figure 7). The generation of absorption peaks within the above range in colorless photochromic glass produces surface-colored glass exhibiting orange, red, purple, blue, or a mixture thereof.

As mentioned above, the absorption properties obtained according to the invention are strongly dependent on the temperature at which the glass is kept during the reductive heat treatment.

In particular, it is very difficult to obtain colors of orange, red, purple and blue, or mixtures thereof, using temperatures higher than about 450°C. For example, when the glass shown in the curve in Figure 7 is heat treated at a temperature around 450°C or higher in a reducing atmosphere, 510 parts m
The relatively strong absorption peak in the vicinity shifts to an absorption near 450 parts m, and the glass becomes brighter and its color approaches yellow. For this reason, temperatures of about 200 to 450°C are preferably used in the second method of the invention.

It has also been found that the surface coloration exhibited by heat-treated glasses is strongly dependent on the thermal history of the precursor glass. As an extreme example, if the precursor glass of the glass shown in curve 1 in Figure 7 is simply slowly cooled without being heat-treated at the photochromic phase generation temperature, the glass obtained for all reduction heat treatments in the range of 300 to 450°C is It is yellow.

The base glass composition also has a significant influence on the various surface colors obtained. The glass of curve 1 in Figure 7 is 40
The Corning code 8097 photochromic glass used to obtain the surface-colored photochromic glass according to the conventional method is yellow after the same reductive heat treatment, while it is orange after a one hour reductive heat treatment at 0°C.

Preferred photochromic glasses for making surface-colored photochromic glass products according to the method of the present invention are those disclosed in the above-referenced US Pat. No. 4,190,451. The glass of this patent contains approximately 0 to 2.5% LiO, O to 9% NaZO, O to 17%, and 20 to 6% by weight.
Cs2O, 14-23% of 8203.5-25%
Ag2O3,0 to 25% P 205.20 to 6
5%5i02.0.004-0.02% Cu 0.
It consists of 0.15-0.3% Ag, 0.1-0.25% CΩ and 0.1-0.2% Br, where Li20+Na20+20+C820 is 8-20
%, and the alkali metal oxide diB2O3 molar ratio is approximately 0
,55 to 0,85, and Ag: (CΩ+
Br) weight ratio is approximately 165 to 0.95. Also, as described in this patent, the glass may optionally contain other oxides or elements in a total amount up to about 10%. Such optional components include up to 6% ZrO2, up to 3% TiO2, and up to 5% Pb0.
, 7% or less Ba0, 4% or less CaO13% or less M
Nb2O5 with gO up to 16%, La2O3 up to 4% and F up to 2%.

Of course, it has been found that other photochromic glasses can also be used in the method of the present invention depending on the absorption properties produced by the reduction heat treatment. Another photochromic glass suitable for use in the method of the invention is U.S. Pat.
This is a photochromic glass disclosed in No. 018,965. This glass has approximately 57.1 to 65.3% 5i02.9.6 to 13.9% Ap by weight.
z-03,12,0 to 22,0% B2O3,1,0
3.5% to 120.3, 7 to 12.0% Na
no, 0 to 5.896, 20, 0.7 to 3096
of Pb0, 0.1 to 1.0% Ag.

〇, 15 to 1. Q% BSo to 8.0% Br.

0-2.5% F, 0.008-0.12% Cub.

consisting of a transition metal oxide colorant in a total amount of O to 1% and a rare earth oxide colorant in a total amount of 0.5%, where L
20 is 6 to 15% for i20+Na20+, and L
The weight ratio of 20 to i2O to Na2O+ is about 223 or less. As stated in this patent, the glass is particularly suitable for the production of glazings such as photochromic sunglass lenses.

Next, the present invention will be explained by examples.

Example A Approximately 5B in parts by weight, 46 parts S i 02 , θ, 1
9 parts A, ll'203, 18.15 parts B203.1
．． ．． 81 parts Li2O, 4.08 parts Na20.5.7
2 parts 20.4.99 parts ZrO2, 2.07 parts T
i 02, o, ooe part Cu 0. 0.207
part of Ag, 0.100 part of c4 and 0.137 part
A composition for photochromic glass consisting of 100% Br is melted in a continuous melting device, pressed to form a spectacle lens blank, slowly cooled for 10 minutes at a peak slow cooling temperature of 470°C, and then cooled at the cooling rate of the furnace. did. Next, some of these slowly cooled eyeglass lens blanks were heat-treated at 660°C for 30 minutes to turn them into photochromic lens blanks, and some were heat-treated at 550°C for 65 hours to turn them into photochromic lens blanks. Ta. Small samples were cut from these photochromic lens blanks and the samples were polished to a thickness of 2 mm.

The photochromic glass sample obtained by heat treatment at a temperature of 550°C was placed in a 400°C furnace containing a 100% H2 flow. The glass samples were kept in the oven for one hour and then removed from the oven and examined.

The surface-colored sample obtained by the above treatment appeared pale orange in the light transmitting state, and exhibited a spectral transmittance curve almost the same as curve 1 in FIG. 7 in the non-darkening state. This spectral transmittance curve is 460nm and 510nm
It has two strong absorption peaks centered around 51
Transmittance at 0 nm is approximately 11% in non-darkened state
It is.

Example B One of the photochromic glass samples of Example A obtained by heat treatment at 660°C was heated to 10% as in Example A.
Reductive heat treatment was performed at a temperature of 400°C for 1 hour in a 0% H2 stream. After this reduction heat treatment, the sample exhibits a red color in the light transmitting state and curve 2 in Figure 7 in the non-darkening state.
It showed almost the same spectral transmittance curve. This spectral transmittance curve has two strong absorption peaks centered around 4 GO nm and around 540 nm, and the spectral transmittance curve has two strong absorption peaks centered around 4 GO nm and 540 nm.
The transmittance in nm is about 9% in the undarkened state.

Example C Two photochromic glass samples of Example A obtained by heat treatment at 550° C. were subjected to reduction heat treatment. One sample (sample 3) was subjected to reduction heat treatment at a temperature of 300° C. for 1 hour in a 100% H 2 stream. The other sample (sample 4) was
Photothermal treatment was performed at a temperature of 0° C. for 16 hours.

After the above treatment, sample 3 exhibited a medium intensity purple color while sample 4 exhibited a pale blue color in the light transmission state. The spectral transmittance curves of Sample 3 and Sample 4 were approximately the same as Curve 3 and Curve 4 in FIG. 7, respectively.

Sample 3 contains 535n in the yellow-green region of the visible spectrum.
It shows an absorption peak centered around m, and the transmittance at 585 nm is about 29% in the non-darkened state. Sample 4 has 565r+m in the yellow region of the visible spectrum.
It shows a broad absorption peak centered around 5[i5
The transmittance in nm is about 63.5 in the non-darkened state.
%.

If a surface-colored photochromic glass product with one of these new absorption bands is heated to a temperature higher than that used to color the product, as in the case of ion-exchange or thermal strengthening, In general, the absorption band shifts toward the violet side of the spectrum, which shifts the color of the glass toward yellow. If it is desired to avoid such color migration, the photochromic glass can be chemically or otherwise strengthened prior to the reductive heat treatment, followed by the reductive heat treatment. In this case, the reducing heat treatment has little negative effect on glass strength. Examples regarding the above will be described below.

Example D A pair of photochromic glass spectacle lens blanks, commercially available from Corning Inc. as Corning Code 811 Lens Blanks, were used in the experiments.

This lens blank has approximately the same composition as the samples of Examples AC. This pair of lens blanks were ground and polished to give them a prescription, frame edges were added, and then chemically strengthened. This chemical strengthening involves KN O3 and N
This was done by immersion in a 400° C. molten salt bath consisting of aNO3 for 16 hours.

After ion exchange strengthening treatment, the lens is placed in a tube furnace,
It was photothermally treated at a temperature of 430° C. for 15 minutes under 100% H2 atmosphere and then removed from the oven and inspected. In the light transmitting state, the lens exhibited a vermilion color. This is because a moderately broad strong absorption peak centered around 510 nm occurred in the green region of the spectrum. lens 51
Transmittance at 0 nm is approximately 44% in non-darkened state
Met.

When the lenses were placed in a frame to form photochromic sunglasses, these lenses showed particularly excellent performance outdoors against a green background.

This is because the transmittance of these lenses is relatively low for green light and significantly high for blue, yellow and red light. Such transmittance characteristics enhance object-background contrast for many objects observed against a green background.

By the method of the present invention, the glass colorant is added to the solute oxide (di
An example will be described below in which a surface-colored photochromic glass product is manufactured from a photochromic glass product containing a photochromic glass product in the form of ssolved oxide.

Example E has approximately the same composition as the photochromic glass of Example A above, but additionally contains 0.09 parts by weight of NiO and 0.09 parts by weight of NiO.
A pair of photochromic glass eyeglass lens blanks containing 0.01 parts by weight of Coo as the solute oxide glass colorant were used in the experiment. These lens blanks are commercially available from Corning Corporation as Corning Code 8115 lens blanks and are light brown in color.

Grind and polish the blank to a certain degree (=J digit).

The resulting pair of lenses was placed in a 42-meter tube containing a 100% H2 atmosphere.
It was placed in an oven at 0°C and kept there for 15 minutes to remove the surface coloration, and then removed from the oven.

The colored lenses thus obtained exhibited a color mixture between the body color and the resulting surface coloring. This colored lens was subjected to the same ion exchange strengthening treatment as in Example.

That is, the colored lens was immersed in a 400°C molten salt bath containing KNO3 and NaNO3 for 10 hours.

The colored lenses were then removed from the bath, cleaned, and characterized. The obtained reinforced lens exhibited a reddish-brown color and had a 485n
It shows a somewhat wide absorption band centered around m, and 2
It had a 485+un transmittance of about 25% at mm thickness. These reinforced lenses also exhibited excellent darkening and fading responses.

Corning Code 8115 glass having a composition as described above is a particularly preferred photochromic glass for the method of the present invention, and light gray Corning Code 8114 glass
Glass is also a particularly preferred photochromic glass for the method of the invention. This 8114 glass has the same basic composition as 8115 glass, except that 0.09 parts by weight of NiO and 0.01 parts by weight of Co are contained in 8115 glass.
0.017 parts by weight of NiO and 0.02 parts by weight in place of o
Contains 0 parts by weight of Coo. However, as illustrated in the Examples below, other photochromic glasses can also be used to make surface color photochromic glass products in accordance with the present invention.

Example F Approximately 5983% by weight 8102.15.01% 8203.9.42% AJ7203.1.84% 20% 3.5% Na20.5.8% I(20
A photochromic glass composition consisting of 146% Cab, 0.5% Ag = 0.5% Cρ and 0.206% CuO was melted in a small continuous melter and formed into glass products. The glass products obtained in this way are approximately 4
It was slowly cooled for 10 minutes at a peak slow cooling temperature of 70°C, and then cooled at the cooling rate of the furnace.

Several small glass samples were then cut from the glassware and polished to a thickness of 2 mm. One of the obtained samples was heat treated at a temperature of 575° C. for about 60 minutes to obtain a photochromic glass sample.

Next, this photochromic glass sample was heated to 100% H.
The sample was placed in a furnace at a temperature of 400°C containing 2 atmospheres and kept there for 1 hour. The sample was then removed from the furnace and its properties investigated.

The color of this sample in the light transmission state was dark orange. Moreover, the spectral transmittance curve of this sample was almost the same as curve 5 in FIG. This spectral transmittance curve has a strong absorption peak centered near 470 nm (i) in the blue region of the spectrum.

The transmittance at 470 nm for a 2n+m thick sample is approximately 6% in the undarkened state.

Example G Approximately 58.6 parts by weight of 5i02.17.5 parts of B
203.11.5 parts of Ag2O3, 7.7 parts of Nan
o, 2.0 parts of Li2O, 1.5 parts of 2012.2
pbo of part, o, Ag of part a, Cρ of part OJ7, 0.
13 parts B, 0.022 parts F, 0.025 parts Cub.

Thin photochromic lenses molded from drawn glass having a composition of 0.041 parts NiO and 0.029 parts Coo were used in the experiments. This lens is pale gray in the undarkened state and its thickness is approximately 1.5 mm.
It was 5w++n. Also, the spectral transmittance curve of this lens in the non-darkened state is called ``untreated'' in Figure 9;
] It was almost the same as the curve that was eclipsed.

This lens was surface colored by placing it in a 420'C oven containing 100% H2 atmosphere for 15 minutes (-
I gave 1. After this reduction heat treatment, the lenses were taken out of the furnace and their properties were investigated.

The color of the lens in the light transmitting state is grayish brown (g
The spectral transmittance curve of this lens in the non-darkened state was almost the same as the curve at "420°C" in FIG. Therefore, the lens is 490 parts m
(It shows an absorption peak centered near J, and the lens shows an absorption peak centered near J.
The transmittance at 9[1nI11 is about 42% in the undarkened state.

Next, the same FoI chromic xanglass lens as above was photothermally treated at a temperature of 465°C for 15 minutes in a 100% H2 atmosphere. The lens after this reduction heat treatment is yellowish gray (yet low-gray), as shown in Figure 9.
It had a spectral transmittance curve that was almost the same as the curve at 465°C.As is clear from this spectral transmittance curve, at 465°C
In the case of the reduction heat treatment at 420°C, the absorption peak that existed near 490 parts m shifts to the shorter wavelength side, and the absorption peak at 480 parts to the left of the color barrier CB in Fig. 9 shifts to the shorter wavelength side. Part m (・Appears near I.

And for this reason, a strong yellow component can be seen in the lens. As is clear from this example, the absorption characteristics observed in the photochromic glass subjected to the reduction heat treatment strongly depend on the temperature of the reduction heat treatment.

In obtaining a selectively colored photochromic glass lens by removing the surface layer by the method of the present invention,
It has been found that acidic agents containing F--ions are suitable as chemical agents for selectively removing surface material from tinted lenses.

However, in order to minimize the effect of removing the surface layer on the surface layer lubricity of the lens, the thickness of the colored surface layer of the surface-tinted photochromic lens to be treated is approximately 1.
00 microns or less is preferable.

The type of chemical agent used for selective surface removal is not particularly important. The selected fo! without surface defects such as frost or upper holes! - Any chemical agent effective to dissolve chromic glass can be used. A preferred agent for use in commercial compositions of silicate photochromic glasses is an aqueous solution of HF.

The rate of surface removal from glass can be controlled by controlling the composition of the remover, for example by dilution or by the introduction of modifiers such as acids, salts, etc., and by controlling the temperature of the remover during removal. It can also be controlled by controlling. By appropriately varying these parameters, conditions suitable for very rapid removal of colored surface glass, e.g. complete removal of the colored layer within a few seconds, or relatively slow conditions, such as requiring several minutes for complete removal of the colored layer, can be achieved. Conditions suitable for dissolution rate can be easily obtained.

Control over the area and shape of the surface portion that is chemically removed can be achieved using various masking techniques commonly used in hydrofluoric acid etching of glass products. Such masking techniques include the use of paraffinic masking agents or other methods of preventing contact of the removal agent with the glass surface.

Preferably, a portion of the lens is immersed in the remover for a time sufficient to effect change or removal of the colored layer, after which the lens is removed from the remover and rinsed to stop the removal process. This method is particularly effective in creating color gradients in lenses. This is because the color gradient can be easily controlled by changing the dipping method. Thus, a quick partial immersion and immersion followed by rapid removal and rinsing can provide a sharp color gradient or rapid color change between the top and bottom of the lens, while a slow immersion and removal allows the lens to It is possible to obtain a gentle negative gradient, that is, a slow color change between the upper and lower parts. The dark color border between the immersed and non-immersed parts of the lens that occurs in such '/M'lk methods can be avoided by not moistening the lens with water before immersion.

The method for selectively removing the wide surface layer of the six-color surface photochromic glass product of the present invention will be explained below using Examples.

Example H Approximately 58.6 parts by weight of 5i02.17.5 parts of 8
203.11.5 parts of Aρ203, 7.7 parts of Na
20.20 parts of Li2O,l, 5 parts of 20.2.2 parts of pbo, 0.3 parts of Ag, 0.47 parts of Cρ, 0.1
3 parts Br, 0.022 parts F, 0.025 parts Cub.

Thin F1 chromic sunglass lenses molded from drawn glass having a composition of 0.150 parts NiO and 0.014 parts Coo were used in the experiments. The lens is light brown in the undarkened state and is approximately 1.
It has a thickness of 5nr+n and is commercially available from Corning Corporation as Corning Code 8103 glass.

To provide a colored surface layer on this lens, the lens is
Reductive heat treatment was performed at a temperature of 550°C for 30 minutes in a tube furnace containing 00% H2 atmosphere. The lenses were then removed from the furnace and their properties were investigated. In the light transmitting state, the lens exhibited a dark brown surface coloration.

To obtain a selectively colored lens from this surface-tinted lens, the lens is first moistened with water and then a portion thereof is immersed in an aqueous HF solution containing about 16% by weight of HF for about 2 minutes. A part of the surface colored layer was chemically removed.

Approximately 1/2 of the lens was immersed in the HF aqueous solution, and the immersion and removal of the lens was controlled such that a relatively slow color change was obtained between the treated and untreated portions of the lens surface.

The above process resulted in a photochromic sunglass lens that exhibits a relatively dark black color when exposed to ultraviolet light and has a fixed negative slope observed in both the undarkened and darkened states. In the undarkened state, the upper part of this lens is a relatively dark brown and the lower part is a very pale yellow. Furthermore, no change in refractive power on the lens surface was visually observed.

Example I To impart a contrasting color to the lower part of the fixed negative slope sunglass lens obtained in Example H above, the lens was retinted after the dipping treatment described in Example H. The lens was subjected to a reducing heat treatment to recolor the pale yellow lower part of the lens. This reduction heat treatment was performed by firing the lens at a temperature of 350° C. for 1 hour in a tube furnace containing a 100% H2 atmosphere.

After the reduction heat treatment, the lenses were removed from the furnace and their properties were investigated. In the light transmitting state, the lower part of the lens was pale purple. This color shows a high contrast with the dark brown color at the top of the lens.

When performing the above-mentioned reheating surface coloring, apply a second layer on the glass.
The reheating used to apply the or more colored surface layers is at a lower temperature than that used when the first or other extended surface layer was applied on the glass. It is preferable to do so. This is because lower temperatures generally do not change the color of the previously applied layer. Therefore, when producing multicolored glass products, generally the first color applied to the glass must be the color that requires the highest reductive heat treatment temperature, and subsequent colors are sequentially applied at lower reductive heat treatment temperatures. must be established.

In the aforementioned reduction heat treatment of phototalomic glass containing PbO, in addition to coloring with silver, PbO
Coloration is present in the glass due to the reduction of lead to metallic lead. This lead staining is also confined to the glass surface and can be removed. Lead staining is much more impermeable than silver staining. Therefore, by appropriately controlling the surface removal process, it is possible to remove lead staining from one surface area and lead and stud staining from another surface area, and for this purpose a single heat treatment is required. It is possible to provide brown-yellow and clear areas in a single glass product.

[Brief explanation of the drawing]

FIG. 1 shows on a chromaticity diagram the chromaticity coordinates of colored photochromic glass produced by the reduction heat treatment method of the present invention. FIG. 2 is a graph showing the spectral transmittance curve of colored photochromic glass produced by the reductive heat treatment method of the present invention. FIG. 3 is a graph showing spectral transmittance curves of colored photochromic glass produced by the reduction heat treatment method of the present invention and untreated photochromic glass. 4 to 7 are graphs showing spectral transmittance curves of colored photochromic glass produced by the reductive heat treatment method of the present invention. FIG. 8 is a graph showing a spectral transmittance curve of blue photochromic glass manufactured by a conventional reduction heat treatment method. FIG. 9 is a graph showing spectral transmittance curves of colored photochromic glass produced by the reduction heat treatment method of the present invention and untreated photochromic glass. -4 expenses (me) 2 bean paste (wave) @→Dou (rug)

Claims (1)

[Claims] (1) a) heat treating a transparent photochromic glass product in a reducing gas environment to provide a colored surface layer on at least a portion of the product; and then b) chemically removing at least a portion of the colored surface layer. A method for producing selectively colored photochromic glass, characterized in that the color of the colored surface layer is changed by changing the color of the colored surface layer.