Colored glass

Abstract: This invention provides: (1) a colored glass comprising 20 to 85% by weight of SiO₂, 2 to 75% by weight of B₂O₃, not more than 15% by weight of Al₂O₃, not more than 30% by weight of at least one member of Li₂O, Na₂O, K₂O, Rb₂O and Cs₂O, not more than 10% by weight of at least one member of MgO, CaO, ZnO, BaO, SrO and PbO, not more than 10% by weight of at least one member of ZrO₂, La₂O₃, Y₂O₃, Ta₂O₃ and Gd₂O₃, 0.05 to 15% by weight of at least one copper halide, and 0.001 to 7% by weight of at least one member of oxides of Fe, Ni, Mn, Co, V, Cr, Cu, Nd and Pd; and (2) a colored glass comprising 8 to 25% by weight of SiO₂, 5 to 35% by weight of P₂O₅, not more than 30% by weight of B₂O₃, 10 to 35% by weight of Al₂O₃, 5 to 20% by weight of at least one member of Li₂O, Na₂O, K₂O, Rb₂O and Cs₂O, not more than 20% by weight of at least one member of MgO, CaO, ZnO, BaO, SrO and PbO, not more than 10% by weight of at least one member of ZrO₂, La₂O₃, Y₂O₃, Ta₂O₃ and Gd₂O₃, 0.05 to 15% by weight of at least one copper halide, and 0.001 to 7% by weight of at least one member of oxides of Fe, Ni, Mn, Co, V, Cr, Cu, Nd and Pd.

Description: Background Art The present invention relates to colored glass. It should be understood that throughout this specification the symbol % means percentage by weight. Colored glass containing colored ions exhibits its expected functions by absorbing light, either broadly or sharply, in the ultraviolet, visible or near-infrared region of the spectrum. Examples of colored glass contain at least one of such ions as Fe, Ni, Co, V, Ce, etc. as incorporated in the base glass. These types of colored glass have been used in distinct applications according to their transmission and absorption characteristics, for example as optical filters such as neutral density filters, blue filters, etc., sunglasses, colored glasses for containers, colored plate glass and so on. However, the conventional colored glass has not fully satisfied the performance requirements in such respective applications. For example, when colored glass is used for sunglasses, it is not only required to have the expected transmission characteristic with regard to visible light but desirably should intercept light in the ultraviolet region, which is harmful to the eye, with substantial thoroughness. Actually, however, when the absorption of visible light is set to the transmittance value suited to sunglasses, the conventional colored glass passes most of the harmful light in the ultraviolet spectrum, too. On the other hand, if an UV absorbing colored ion, such as Ce, is incorporated in glass to the extent completely absorbing light in the ultraviolet region, light in the visible region is also mostly absorbed because of its broad absorption characteristic, with the result that the colored glass cannot discharge the function required of sunglasses. Therefore, whenever the conventional colored glass is used for sunglasses, either the transmittance characteristics of visible light or that of ultraviolet light has to be sacrificed. JP-B-463464 relates to a glass composition comprising CuCl or CuBr. The glass composition intercepts UV light at a wavelength less than a specific wavelength within the range 375-425 nm and has a wavelength inclination of about 6 nm. Nevertheless the glass does not exhibit good resistance to fading. Summary of the Invention The primary object of the present invention is to provide a fade resistant colored glass which exhibits the desired transmittance characteristic which can be achieved by incorporated colorants in the visible region of the spectrum and can substantially completely intercept light of wavelengths not longer than a selected wavelength within or near the ultraviolet region. In view of the above shortcomings of the conventional colored glass, the inventors of the present invention made intensive investigations for developing new types of colored glass that could accomplish the above-mentioned object. As a consequence, the inventors discovered that when a copper halide, which is a semiconductor substance composed of elements of groups I and VII of the Periodic Table is included in base glass as a dopant together with a certain component, there is obtained a colored glass which intercepts light not exceeding a given wavelength, shows a colorant-associated spectral transmission characteristic almost completely for light longer than said wavelength, and insures an excellent transmission characteristics represented as a sharply inclined curve with a narrow wavelength gradient profile. Thus, the present invention provides a colored glass comprising 20 to 85% by weight of SiO 2 , 2 to 75% by weight of B 2 O 3 , not more than 15% by weight of Al 2 O 3 , not more than 30% by weight of at least one member of Li 2 O, Na 2 O, K 2 O, Rb 2 O and Cs 2 O, 0.1 to 5% by weight of at least one member of MgO, CaO, ZnO, BaO, SrO and PbO, 0.1 to 5% by weight of at least one member of ZrO 2 , La 2 O 3, , Y 2 O 3, Ta 2 O 3 and Gd 2 O 3 , 0.05 to 15% by weight of at least one member of CuCl, CuBr and CuI, and 0.001 to 7% by weight of at least one member of oxides of Fe, Ni, Mn, Co, V, Cr, Cu, Nd and Pd. The colored glass according to the present invention contains a microcrystalline copper halide as a dopant in a basal glass composition as mentioned above and not only selectively pass light of wavelengths longer than a selected wavelength but substantially intercepts the ultraviolet beam not longer than said wavelength to insure a desired spectral transmission characteristic. Moreover, the colored glass of the invention does not change color even on exposure to intense ultraviolet light so that its intrinsic light transmission characteristic is retained without alteration. Brief Description of the Drawings Referring to the accompanying drawings, Figs. 1 through 4 are graphs showing the spectral transmission characteristics of the colored glasses of the invention; and Figs. 5 through 14 are graphs showing the spectral transmission characteristics of the colored glasses of comparative examples. Detailed Description of the Invention Of the glass components of the colored glass of the invention, all components other than copper halide, which is the outstanding feature of the invention, are selected from among the various materials used commonly as glass components. To be specific, such components other than copper halide in the invention are selected from among SiO 2 , B 2 O 3 , Al 2 O 3 , Li 2 O, Na 2 O, K 2 O, Rb 2 O, Cs 2 O, MgO, CaO, ZnO, BaO, SrO, PbO, ZrO 2 , La 2 O 3 , Y 2 O 3 , Ta 2 O 3 , Gd 2 O 3 , and oxides of Ni, Mn, Co, V, Cr, Cu, Nd and Pd, all of which are known components, and used in the specified proportions. Of course, in a multi-component glass system, the respective components interact with each other to determine characteristics of the whole system and it may not always valid to discuss the quantitative relation of components in independent terms. However, the ground for the quantitative range shown for each component in the first and the second invention is discussed below. Of the glass components to be used in the invention, SiO 2 is a main component forming a glass-network and used in a proportion of 20 to 85% by weight, preferably about 50 to 71%, based on the total composition. If the proportion of SiO 2 exceeds 85%, the meltability of glass will be adversely affected, while the use of SiO 2 in a proportion less than 25% will lead to inadequate chemical permanence or durability and, hence, may undesirably cause discoloration. B 2 O 3 not only contributes to the meltability of glass but assists in the formation of glass-network in certain compositions. B 2 O 3 is incorporated in a proportion of about 2 to 75%, preferably about 12 to 27%, based on the total composition. If the proportion exceeds 75%, the chemical durability of glass will not be sufficiently high, while the use of B 2 O 3 in a proportion less than 2% will result in an inadequate light transmission characteristic and a reduced meltability of glass. Al 2 O 3 is a component for inhibiting the devitrification and enhancing the chemical durability of glass, and is incorporated in a proportion not greater than about 15%, preferably of about 1 to 10%, based on the total composition. If the proportion exceeds 15%, the meltability of glass is considerably sacrificed. Li 2 O, Na 2 O, K 2 O, Rb 2 O and Cs 2 O are effective in improving the meltability of glass and it is preferable that one or more species be added in a proportion not greater than about 30%, more desirably of about 5 to 15%, based on the total composition. If the proportion exceeds 30%, the chemical durability of glass will become inadequate. MgO, CaO, ZnO, BaO, SrO and PbO are effective in improving the chemical durability of glass and one or more species of them are added in a proportion in the range from 0.1 to 5%, all based on the total composition. ZrO 2 , La 2 O 3 , Y 2 O 3 , Ta 2 O 3 and Gd 2 O 3 are effective in improving the chemical durability of glass and one or more of them are added in a proportion in the range from 0.1 to 5%, based on the total composition. The oxides of Fe, Ni, Mn, Co, V, Cr, Cu, Nd and Pd are effective in coloring glass in the visible region of the spectrum and it is preferable that one or more members be added in a proportion of about 0.001 to 7%, more preferably about 0.05 to 3%, based on the total composition. If the proportion of this component exceeds 7%, the light transmission of glass is decreased, while the use in a proportion less than 0.001% is inadequate in glass coloring effect. The copper halide to be used in accordance with the first invention includes CuCl, CuBr and CuI, and glass can be doped with one or more of these species. These species of copper halide act as colorants which absorb light of a specific wavelength range in ultraviolet or visible region of the spectrum. In the invention, this component is added in a proportion of about 0.05 to 15%, preferably about 0.3 to 8%, based on the total composition. When the proportion of this component in glass is controlled within the above range, it substantially completely intercepts light of wavelengths not longer than a given wavelength within the range of 350 to 450 nm and insures a colorant-associated spectral transmission characteristic almost completely for light longer than said wavelength. Furthermore, there is obtained a glass having an excellent transmission characteristic with a narrow absorption wavelength gradient profile. If the proportion of copper halide is less than 0.05%, the above desirable effect will not be fully realized. Conversely, if the proportion exceeds 15%, devitrification will undesirably occur. The colored glass of the invention can be manufactured by mixing the starting materials according to the above-described formula and treating the mixture in the per se conventional manner. For example, the starting materials in the specified proportions are melted at a temperature of about 1,200 to 1,500°C, stirred, refined, cast, heat-treated at a temperature of about 450 to 700°C for about 0.1 to 5 hours either in the course of cooling or after cooling, and finally processed by cutting, polishing, etc. to give a glassware of the desired shape. In order to incorporate microcrystals of said copper halide in glass in the above production process, either a copper halide itself or a copper source compound, such as copper oxides, copper halides, etc., in combination with a halogenated alkali compound which can be a halogen source capable of forming a copper halide with said copper source, such as lithium halides, sodium halides, potassium halides, rubidium halides, cesium halides, etc., can be blended with the other component materials in accordance with the specified formula. Regarding the components other than copper halides, the conventional glass materials such as oxides, carbonates and hydroxides which eventually provide the intended composition can be used as they are. The cooling step referred to above should be as gradual as possible to prevent thermal straining of glass, e.g. at a rate of about 10 to 100°C/hr or preferably about 30 to 50°C/hr. For the same reason, the heating is also preferably conducted gradually at about 10 to 100°C/hr, preferably at about 30 to 70°C/hr. The heating speed and time are determinant of the crystal size of copper halide. In this invention, the crystal size is preferably controlled at about 0.1 to 10 nm in diameter. The melting step is preferably carried out in a neutral or reducing atmosphere to convert Cu ion into Cu +. In the refining step, a known refining agent such as As 2 O 3 , Sb 2 O 3 or the like can be employed and the level of addition of such a refining agent is optional within the range not adversely affecting the characteristics of the colored glass of the invention. The refining agent is used usually in an amount of about 0.5 % or less, preferably about 0.05 to 0.3%, based on the total composition. The glass of the present invention is capable of producing the following effects. (1) In the wavelength range of 250 to 800 nm, the glass almost completely intercepts light of wavelengths not longer than a selected wavelength in the range of 350 to 450 nm and almost completely achieves a colorant-associated spectral transmission characteristic for light longer than said wavelength. Moreover, it has an excellent transmission characteristics represented as a sharply inclined curve with a narrow wavelength gradient profile. (2) By adjusting the content or kind of copper halide, or the combination of the content and kind of copper halide, light of optional wavelengths within the range of 350 to 450 nm can be controlled. (3) Exposure to ultraviolet light, visible light or near-infrared light does not cause changes in the above spectral transmission characteristic. (4) Unlike the conventional colored glass, the production process is safe and it is not necessary to exercise more than usual care in handling or disposal. Therefore, the colored glass can be manufactured using the general glassmaking equipment without addition of any treating device. (5) Since the meltability of glass is satisfactory, glass material of homogeneous composition with stable performance properties can be obtained. (6) Therefore, the colored glass according to the present invention is of great use as glass materials for masking in an apparatus for UV-curable resin, glass materials for protection of fine arts, etc., glass materials for optical filters, glass materials for spectacles, illumination glass materials, protective glass materials for liquid crystal panels, glass materials for containers, powdery UV absorbent additives and so on. The following examples are intended to further clarify the characteristics of the present invention. Examples 1 through 2 The starting materials were mixed to give the compositions shown (%) in Table 1 and each composition was melted in an alumina crucible, stirred, refined, cast in a mold, and allowed to cool down to room temperature. The cast glass was heat-treated, cut and polished to give a colored glass according to the invention. The melting was carried out in a neutral or reducing atmosphere. The cooling rate and the heating rate in the heat treatment stage were 30°C/hr and 50°C/hr, respectively. All the compositions could be easily melted and formed and the resulting glasses were excellent in chemical durability. It was confirmed that the use of As 2 O 3 or Sb 2 O 3 in an amount of 0.2-0.25% in the refining stage did not cause changes in the transmission characteristics of the glasses. Example 1 2 SiO 2 70.5 61.7 B 2 O 3 13.8 16.0 Al 2 O 3 - 3.2 Li 2 O 0.5 - Na 2 O 6.5 6.0 K 2 O 3.2 5.5 MgO - - CaO 3.0 - ZnO - - BaO 0.5 - SrO - 1.0 ZrO 2 0.5 - La 2 O 3 - 0.5 Y 2 O 3 - - CuCl - - CuBr 0.9 - CuI - 6.0 Colorant CuO - - Fe 2 O 3 - - NiO 0.6 - CoO - 0.1 Nd 2 O 3 - - Melting temperature 1450°C 1400°C Heat treatment temperature 670°C 630°C Heat treatment time 5 hours 3 hours Examples 3 through 4 The starting materials were mixed to give the compositions shown (%) below in Table 2 and each composition was melted in an alumina crucible and treated in the same manner as Examples 1 through 2 to give colored glasses of the invention. All the compositions could be easily melted and formed and the resulting glasses were excellent in chemical durability. It was confirmed that the use of As 2 O 3 or Sb 2 O 3 in an amount of 0.2 to 0.25% in the refining stage did not cause changes in the transmission characteristics of the glasses. Example 3 4 SiO 2 62.0 67.7 P 2 O 5 - - B 2 O 3 17.8 23.1 Al 2 O 3 - - Li 2 O - - Na 2 O 8.2 3.3 K 2 O 2.0 1.2 Rb 2 O 0.5 - Cs 2 O - - CaO - - ZnO - 1.1 BaO 0.5 - SrO - - PbO 2.0 - Ta 2 O 3 0.5 - Gd 2 O 3 - 0.5 CuCl 1.7 1.09 CuBr - - Colorant (a):0.3 (e):1.5 (f):0.01 (g):0.5 Melting temperature 1400°C 1450°C Heat treatment temperature 580°C 650°C Heat treatment time 2 hours 2 hours Note: (a)...V 2 O 3 , (b)...MnO, (c)...Cr 2 O 3 , (d)...PdO, (e)...NiO, (f)...CoO, (g)...CuO Comparative Examples 1 through 5 The starting materials were mixed to give the compositions shown (%) in Table 3 and each composition was melted in an alumina crucible and treated in the same manner as Examples 1 through 5 to give Comparative Examples of colored glass. Incidentally, the colors glasses of Comparative Examples were not heat-treated because heat-treatment does not improve the characteristics. The same applies to Comparative Examples 6 through 10 which appear hereinafter. Comparative Example 1 2 3 4 5 SiO 2 67.3 59.4 70.5 67.7 57.7 B 2 O 3 12.6 20.8 13.8 16.0 26.1 Al 2 O 3 1.0 4.6 - 3.2 2.0 Li 2 O 1.8 - 0.5 - 0.5 Na 2 O 11.6 13.4 6.5 6.0 12.6 K 2 O 1.5 - 3.2 5.5 - MgO 1.0 - - - - CaO 2.9 - 3.0 - - ZnO - 1.2 - - - BaO - - 0.5 - - SrO - - - 1.0 - ZrO 2 - - 0.5 - - La 2 O 3 - - - 0.5 - Y 2 O 3 - - - - 0.8 Gd 2 O 3 - - 0.9 - - Colorant CuO 0.3 - - - - Fe 2 O 3 - 0.6 - - - NiO - - 0.6 - - CoO - - - 0.1 - Nd 2 O 3 - - - - 0.3 Melting temperature 1400°C 1380°C 1450°C 1400°C 1250°C Comparative Examples 6 through 10 The starting materials were mixed to give the compositions shown (%) in Table 4 and each composition was melted in an alumina crucible and treated in the same manner as Examples 1 through 5 to give Comparative Examples of colored glass. Comparative Example 6 7 8 9 10 SiO 2 62.0 59.4 15.3 13.5 67.7 P 2 O 5 - - 27.0 30.0 - B 2 O 3 17.8 16.8 24.0 14.99 23.1 Al 2 O 3 - 7.2 17.0 23.1 - Li 2 O - - - 1.5 - Na 2 O 8.2 - - 12.7 3.3 K 2 O 3.7 10.5 13.1 1.8 1.2 Rb 2 O 0.5 - - - - Cs 2 O - 0.5 1.0 - - CaO - 2.2 1.3 - 1.09 ZnO - 2.2 - 0.9 1.1 BaO 5.0 - 0.5 - - SrO - - - 1.5 - PbO 2.0 - - - - Ta 2 O 3 0.5 - - - 0.5 Colorant (a):0.3 (b):1.2 (c):0.8 (d):0.01 (e):1.5 (f):0.01 (g):0.5 Melting temperature 1400°C 1420°C 1350°C 1370°C 1450°C Note: (a)...V 2 O 3 , (b)...MnO, (c)...Cr 2 O 3 , (d)...PdO, (e)...NiO, (f)...CoO, (g)...CuO Test Example 1 The spectral transmission characteristics of the glasses (thickness: 2 mm) obtained in Examples 1 through 4 were investigated by irradiating them with light in the wavelength range of 300 to 800 nm. The results are shown in Figs. 1 through 4. It is clear from Figs. 1 through 4 that the colored glasses according to the invention effectively intercept light in the ultraviolet region of the spectrum and have a sharp absorption characteristic with a narrow wavelength gradient profile. Each of the glasses obtained in Examples 1 through 4 was irradiated with ultraviolet rays using a 500 W super-high-pressure mercury vapor lamp at a distance of 10 cm and its spectral characteristic was then investigated by exposing it to light in the wavelength region of 250 to 800 nm. The resulting transmittance curves were in agreement with the curves of the corresponding glasses of Examples 1 through 4 prior to ultraviolet light irradiation, indicating that irradiation of the glass of the invention with ultraviolet light does not cause changes in transmission characteristic. Test Example 2 The spectral transmission characteristics of the glasses (thickness: 2 mm) obtained in Comparative Examples 1 through 10 were investigated by irradiating them with light in the wavelength region of 300 to 800 nm. The results are shown in Figs. 5 through 14, respectively. It is apparent from Figs. 5 through 14 that the colored glasses of Comparative Examples cannot effectively intercept light in the ultraviolet region and have a broad absorption characteristic with a wide wavelength gradient profile.

Claims: A colored glass comprising 20 to 85% by weight of SiO 2 , 2 to 75% by weight of B 2 O 3 , not more than 15% by weight of Al 2 O 3 , not more than 30% by weight of at least one member of Li 2 O, Na 2 O, K 2 O, Rb 2 O and Cs 2 O, 0.1 to 5% by weight of at least one member of MgO, CaO, ZnO, BaO, SrO and PbO, 0.1 to 5% by weight of at least one member of ZrO 2 , La 2 O 3, Y 2 O 3 , Ta 2 O 3 and Gd 2 O 3 , 0.05 to 15% by weight of at least one member of CuCl, CuBr and CuI, and 0.001 to 7% by weight of at least one member of oxides of Fe, Ni, Mn, Co, V, Cr, Cu, Nd and Pd. A colored glass according to claim 1 which comprises 50 to 71% by weight of SiO 2 , 12 to 27% by weight of B 2 O 3 , 0.1 to 10% by weight of Al 2 O 3 , 5 to 15% by weight of at least one member of Li 2 O, Na 2 O, K 2 O, Rb 2 O and Cs 2 O, 0.1 to 5% by weight of at least one member of MgO, CaO, ZnO, BaO, SrO and PbO, 0.1 to 5% by weight of at least one member of ZrO 2 , La 2 O 3 , Y 2 O 3 , Ta 2 O 3 and Gd 2 O 3 , 0.3 to 8% by weight of at least one member of CuCl, CuBr, and CuI, and 0.05 to 3% by weight of at least one member of oxides of Fe, Ni, Mn, Co, V, Cr, Cu, Nd and Pd.

Inventors: EINISHI TOSHIHIKO, TARUMI TAKASHI, EINISHI, TOSHIHIKO, TARUMI, TAKASHI
Applicants: ISUZU GLASS CO LTD, ISUZU GLASS CO., LTD.
Application year: 1992
Main classification: C03C3
IPC codes: C03C3, C03C4, C03C1, G02B5