JP3022292B2 - Corrective lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a glass composition for eyeglasses, which not only absorbs less radiation in the visible region of the spectrum (ie, is almost colorless), and a lens made from this glass composition. The present invention relates to a glass composition having improved color stability when an antireflection coating is applied to a glass composition.

[0002]

BACKGROUND OF THE INVENTION When an antireflective coating is applied to certain commercially available glass using a glow discharge device, the glass tends to exhibit an undesirable brown color. During the process of manufacturing the anti-reflective layer, short wavelength radiation is generally emitted to the glass in the form of a corrective lens, which induces an undesirable brown color. As a result, many commercial glasses have
When the anti-reflection layer is applied, a problem that the color becomes unstable occurs.

For example, US Pat. Nos. 2,068,801 and 2,
There are many examples of commercially available spectacle glass compositions or solar cell cover glass compositions, such as 657,146, 3,951,671, 4,565,791, 5,017,521 and 5,219,801.

The following properties: (a) a refractive index of 1.523; (b) Abbe number between 55-62; (c) a density of 2.60 g / cm ³ ; (d) a temperature range of 0 ° C.-300 ° C. 93 × 10 ^-7 / ℃ coefficient of linear thermal expansion over; (e) a softening point of 710 ° C., (f) 90.5% of radiation at a wavelength of 400 nm through a glass thickness of 2mm transmittance; and ( g) Commercial spectacle glasses are also available which have a cutoff of ultraviolet radiation at a wavelength of 328 nm, defined as the wavelength at which the transmission equals 1% at 2 mm thickness.

The glasses described above have the property of being sensitive to the process used to apply the anti-reflection coating in glow discharge devices, ie exhibiting an undesired brown color.

[0006] Since such glasses are sometimes used as the main part of multifocal ophthalmic lenses that are melted into individual, commercially available segments, the ophthalmic glasses have a low coefficient of thermal expansion, as well as a softening point. It is important to keep within each range.

[0007]

SUMMARY OF THE INVENTION The basic object of the present invention is to provide a glass composition which is free from the problem of coloration when an antireflection coating is applied to the glass using a glow discharge device. To provide things. Such glasses have the following properties: (1) a refractive index of 1.523 ± 0.005; (2) an Abbe number between 55-62; (3) a density of less than 2.7 g / cm ³ ; (4) 0 ° C.-300. 88-95 × 10 ^-7 / ° C over a temperature range of ° C
(5) Softening point between 680 ° C. and 730 ° C .; (6) 400 n greater than 85% through 2 mm thick glass
(7) UV cut properties between 310-335 nm, ie, transmittance equal to 1% at 2 mm thickness; (8) Occurs in conventional anti-reflection coating equipment. Resistance to coloration when exposed to glow discharge; and
Most preferably, it must have (9) resistance to exposure degradation.

[0008]

SUMMARY OF THE INVENTION Glasses having the above-described properties are expressed as a percentage by weight on an oxide basis (excluding the halogen component reported for halides according to conventional glass analysis practice). -70% Si
O ₂ , 0-5% B ₂ O ₃ , 2-6% Al ₂ O ₃ , 9
-14% of Na ₂ O, 3-10% of K ₂ O, 0.5 -4% of C
aO-, 3-9% of ZnO, 0.5 -2% of ZrO _2, 0.1
-0.3% of CeO _2, 0-2% of Li ₂ O, 0-5% of MgO, 0-5% of SrO, 0-5% of BaO, 0-1.
5% TiO _2, 0-0.5% of the Sb ₂ O _3, 0-0.3%
Consisting essentially of SO ₃ , 0-0.5% Br, 0-0.5% Cl, and 0-0.5% F, wherein Li ₂ O + Na ₂
O + K ₂ O total 6-22% of, MgO + SrO + BaO
Total 0-7% of the total of _{Sb 2 O 3 + SO 3 +} Br + Cl was found to be produced from the composition is less than 1%.

[0009] As used herein, "substantially free of lead" and "substantially free of antimony oxide" means that the glass has the chemical and / or physical properties of the glass (in some cases). Means) does not contain enough lead or antimony oxide to change. Most desirably, it contains no lead or antimony oxide, but this is not always possible and they may be present as impurities.

Table 1 lists some glass compositions, expressed in parts by weight on an oxide basis (excluding halogen components), illustrating the glasses of the present invention. Since the cation to which the halogen is attached is not known, halogen is indicated for the halide as described above. Since the sum of the components is almost 100, for all practical purposes,
The individual values of each component may be considered to indicate weight percent. The actual batch components of the glass can be of any material, either oxides or other compounds, that, when melted together, are converted in a suitable ratio to the desired oxide. For example, if borax is Na ₂
O and B ₂ O ₃ may be included in the source.
Br is the source of Na ₂ O and Br, and CaCO ₃ is C
A source of aO may be provided.

The glass of the present invention uses this glass as the main component of a bifocal lens because it can be easily welded to a high refractive index commercial glass segment because of its expansion coefficient and softening point. be able to.

Although the optimal amounts of the various components of the glass composition of the present invention may vary depending on the process conditions, the following is a general guideline for determining the optimal amounts of the various components. .

[0013] If the SiO ₂ is greater than 70%, the glass melts and becomes difficult to refine by conventional techniques of the glass industry. If the SiO ₂ is less than 60%, the glass will have difficulty obtaining the desired optical and physical properties as well as good chemical resistance.

Although boron oxide does not significantly affect the optical properties of the glass, the inclusion of boron oxide can improve the meltability of the glass. However, the content of boron oxide is kept below 5% so as not to impair the chemical resistance of the glass.

At least 1% alumina is required to provide good chemical resistance to the glass. Al ₂ O
₃ also enhances the UV cut properties when replaced with silica. However, this oxide contains 6%
Exceeding the limit causes problems when melting the glass.

An alkali metal oxide is added as a flux,
Facilitates melting of components used to make glass. Further, in order to maintain the possibility of welding conventional segments to the glass of the present invention for the purpose of manufacturing bifocal corrective lenses, the alkali metal oxides were changed within the range of the indication to 88-95 × The expansion coefficient of the glass between 10 ^-7 / ° C and the softening point of the glass can be adjusted simultaneously. Beyond the content limits shown in the present invention, Na ₂ O, K
Glasses of the type containing ₂ O and Li ₂ O have insufficient chemical durability. For similar reasons,
The total amount of alkali metal oxide is maintained between 6-20%.

In particular, Li ₂ O is an effective flux,
Due to cost and the tendency to make the glass opaque,
Li ₂ O should be kept below 2%.

In order to improve the ability to withstand chemical tempering, at least 3% zinc oxide is required in the composition of the present invention. The use of zinc oxide increases the density and cost, so the content of zinc oxide is 9%
Keep less than.

The refractive index of the glass is adjusted mainly by adding an oxide of zirconium, titanium, barium, strontium and calcium in the above-mentioned composition range.

The content of calcium oxide must be greater than 0.5% to adjust the refractive index of the glass so that a high viscosity slope with an intermediate viscosity, especially around the softening point of the glass of about 10 ^7.6 Pa · s, can be obtained. Must. This viscosity range is
Of particular importance to the present invention, as it contributes to the weldability of the glass of the present invention to current commercial segments. The content of calcium oxide is preferably less than 4% so as not to impair the chemical resistance of the glass.

Magnesium, barium and strontium oxides may be included in the compositions of the present invention such that the individual content is less than 5% and their total is less than 7%. These oxides are used to contribute to the reduction of the high temperature viscosity of the glass, adjust the viscosity slope in the range close to the softening point, and correct the refractive index.

Zirconium oxide imparts good chemical durability to the glass of the present invention and, like zinc oxide, contributes to an improvement in chemical tempering, so that the content of the present invention is at least equal to 0.5%. Required for different types of glass. In addition, zirconium oxide is effectively included in increasing the index of refraction, and may be used to minimize the coefficient of expansion. However, its content is limited to 2% so as not to cause problems when melting the glass.

Cerium oxide has a function of absorbing ultraviolet rays. It has been found that 0.1-0.3% by weight of cerium oxide is necessary to obtain the ultraviolet ray cut characteristics between 310 and 335 nm.

Titanium oxide may be included in the glass type composition of the present invention to supplement the effect of cerium oxide as an ultraviolet absorber and to contribute to the adjustment of the refractive index.
The content of titanium oxide must not exceed 1.5%. Exceeding this content increases the susceptibility to interaction with any impurities contained in the vitrifiable mixture, and this fact leads to an undesirable yellow coloration of the glass. Because.

The glass contains SO ₃ , B in the above-mentioned content.
Calcination with the help of r, Cl and F. These components should be used individually in amounts that do not exceed the stated upper limits to minimize the risk of corroding the glass forming equipment. Furthermore, for the same reason, the sum of the sintering agents is 1
Should not exceed%.

The glass composition of the present invention may be prepared starting from a vitrified mixture of suitable conventional raw materials for use in the glass industry. For example, borax may constitute a source of boron oxide and sodium oxide, sodium bromide may constitute a source of Na ₂ O and bromine, and calcium carbonate may constitute a source of the required calcium oxide. Good. Halogen, arsenic or antimony are added as conventional sintering agents.

[0027]

The present invention will be described below in detail with reference to examples.

In preparing the glass samples 1 and 2 in Table 1, the raw materials were weighed and blended, and the resulting glass melt was thoroughly mixed (blended) so as to be uniform. The mixture was then loaded into a platinum crucible and placed in a furnace for melting. The crucible was capped to limit the loss of volatile elements from the mixture. About crucible with lid
It was moved into a furnace operating at a temperature of 1500 ° C. After melting, the batch was maintained at this temperature for about 3 hours with stirring. The molten glass was poured into a steel mold to form a glass slab or rod having dimensions of about 3 x 7 x 30 cm. The rods were then transferred to the furnace and 540
Reheated (annealed) at ° C.

The above description reflects only laboratory scale methods. Thus, the glass compositions of the present invention can be melted and formed using large-scale commercial glass melting and forming equipment and techniques.

In the laboratory, samples of glass samples 1 and 2 were polished to 60 kilovolts (kV) and 40 microamps to simulate the emission or glow of radiation generated during the anti-reflection treatment of the corrective lens. (ΜA) exposure to X-rays emitted by an X-ray fluorescence device functioning for 15 minutes. A qualitative visual inspection for the color of the glass was then performed. To evaluate the resistance of the glass to exposure degradation, a 2 mm thick glass sample was exposed to ultraviolet light emitted by a lamp with an emission spectrum simulating sunlight, for 48 hours. The susceptibility of the glass to exposure degradation was then determined by 400 n before and after exposure.
Monitored by measuring the change in transmittance at m. For the purpose of this experiment, the initial transmittance of the glass,
The degree of exposure degradation was measured as the difference at 400 nm wavelength from the transmittance after emission from a simulated sunlight lamp. This difference was expressed as a percentage.

Table 1 compares three glass compositions, namely Sample A (a commercially available lead-containing glass), Sample 1 (a lead-containing glass), and Sample 2 (a lead-free glass of the present invention). . Table 1 also shows the color exhibited by each glass prior to exposure to X-rays and UV radiation (color T _O ), the color exhibited after exposure to X-rays (color Tx), and the exposure degradation experienced by each glass. Of the transmittance loss (exposure) due to the above. Both lead-containing glass compositions appeared yellow after exposure.

As shown in Table 1, the presence of lead in the glass composition causes the glass composition to exhibit a yellow color when exposed to X-rays. Therefore, the glass composition must be substantially free of lead. Most desirably, it is completely free of lead, but this is not always possible, and lead may be present as an impurity.

As is clear from Table 1, when lead is not contained, the presence of a pair of CeO ₂ and Sb ₂ O ₃ increases the tendency of exposure deterioration. Therefore, since CeO ₂ is required to ensure the required ultraviolet light cut characteristics, the glass of the present invention substantially contains Sb ₂ O _3.
Is preferably not contained.

[0034]

[Table 1]

In the following experiments, the need to remove lead from the glass composition and the benefits gained from exposure degradation caused by removing antimony from the glass were confirmed.

In Table 2, four glass compositions of the present invention prepared by the above-described method of the present invention (samples 3-6)
Was compared with a commercially available lead-containing glass (Sample A). Again, to illustrate the glass compositions of the present invention, the glass compositions are given in parts by weight on an oxide basis (excluding halogen content). Glass slabs were prepared from the above glass compositions in a manner similar to that described above.

Table 2 also shows the refractive index (n _D ), Abbe number, density in g / cm ³ , and linear thermal expansion in × 10 ^-7 / ° C over the temperature range of 20 ° C to 300 ° C. Coefficient (expansion), softening point expressed in ° C., transmittance (T ₄₀₀ ) of glass having a wavelength of 400 nm at a thickness of 2 mm expressed in% (T ₄₀₀ ), cutoff characteristics (cut-off) of ultraviolet wavelength expressed in nm,% The loss of light transmittance (exposure) due to exposure deterioration and the color (color Tx) exhibited by the glass after exposure to X-rays are listed.

[0038]

[Table 2]

Based on the most desirable combination of chemical, mechanical, and physical properties, preferred glass compositions are substantially free of lead and antimony and have an oxide basis (excluding the halogen content). expressed in weight percent), SiO _2, 1-5% of B ₂ O ₃ of 61-66%, 2-5
% Of Al ₂ O _3, 9-13% of Na ₂ O, 4-9% of K ₂
O, 1-4% CaO, 5-7% ZnO, 0.5-2%
ZrO ₂ , 0.1-0.3% CeO ₂ , 0-1% Li
₂ O, 0-1% MgO, 0-3% SrO, 0-3%
Of BaO, 0-1% of TiO _2, 0-0.2% of SO _3,
0.2-0.5% Br, 0-0.5% Cl, and 0-0.
Consisting essentially of 5% F, Li ₂ O + Na ₂ O + K ₂
Total of O is 13-22%, Total of SO ₃ + Br + Cl is 1%
Is less than.

The most preferred glass composition is the glass composition of Sample 3 shown in Table 2.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Michel Plasa France Vulene S / Seine F-77870 Rue Saint-Elois 16 (72) Inventor Daniel Louis Gabriel Ricoeur Pollezo F-91120 Rue Lamartine 35 (56) References JP-A-58-145538 (JP, A) JP-A-56-78446 (JP, A) JP-A-62-288134 (JP, A)

Claims (6)

(57) [Claims] 1. The following properties: (a) a refractive index of 1.523 ± 0.005; (b) Abbe number between 55-62; (c) a density of less than 2.7 g / cm ³ ; (d) 0 ° C. 88-95 × 10 ^-7 / ° C over a temperature range of 300 ° C
(E) Softening point between 680 ° C and 730 ° C; (f) 400 n greater than 85% through 2 mm thick glass
(g) UV cut properties between 310-335 nm; (h) resistance to coloration when exposed to X-rays; and (i) resistance to exposure degradation. , A corrective lens that is substantially free of lead,
60-70% Si, expressed as weight percent on an oxide basis
O _2, 2-6% of Al ₂ O _3, 0.5 -4% of CaO, 0.
5-2% of ZrO _2, 9-14% of Na ₂ O, 3-9% of ZnO, 0.1 -0.3% of CeO _2, and 3-10% K
A corrective lens substantially consisting of ₂ O. 2. Substantially free of lead and antimony and 61-66% Si, expressed as weight percent on an oxide basis.
O _2, 0.5 -2% of ZrO _2, 9-13% of Na ₂ O, 1
-4% of CaO, 5-7% of ZnO, 2-5% of Al ₂
O ₃ , 0.2-0.5% Br, 1-5% B ₂ O ₃ , 0.1
-0.3% of CeO _2, and 4-9% of corrective lenses according to claim 1, characterized in that consists essentially of K ₂ O. 3. Expressed in weight percent on an oxide basis,
Moreover, 0-3% of BaO, 0-1% of Li ₂ O, 0-
3% SrO, 0-1% of the TiO _2, 0-1% of the Mg
O, 0-0.5% of F, 0-0.2% of SO _3, and 0
Comprises 0.5% _{Cl, Li 2 O + Na 2} O + K 2 O total 13-22% of, MgO + SrO + BaO total of 0-7
%. 4. Properties as follows: (a) a refractive index of 1.523 ± 0.005; (b) Abbe number between 55-62; (c) a density of less than 2.7 g / cm ³ ; (d) 0 ° C. 88-95 × 10 ^-7 / ° C over a temperature range of 300 ° C
(E) Softening point between 680 ° C and 730 ° C; (f) 400 n greater than 85% through 2 mm thick glass
(g) UV cut properties between 310-335 nm; (h) resistance to coloration when exposed to X-rays; and (i) resistance to exposure degradation. , a glass for spectacles, the glass is free of lead substantially, in percent by weight, 60-70% of SiO _2, 0.1 -0.3% of CeO _2,
3-10% of K ₂ O, 0.5 -5% of B ₂ O _3, 2-6% of Al ₂ O _3, 0.5 -4% of CaO, 0.5 -2% of ZrO
_2, 9-14% of Na ₂ O, and 3-9% of the glass, characterized in that consists essentially of ZnO. 5. The method of claim 6, wherein the composition is substantially free of lead and antimony and has a Si content of 61-66%, expressed as a weight percent on an oxide basis.
O _2, 0.5 -2% of ZrO _2, 9-13% of Na ₂ O, 1
-4% of CaO, 5-7% of ZnO, 2-5% of Al ₂
O ₃ , 0.2-0.5% Br, 1-5% B ₂ O ₃ , 0.1
-0.3% of CeO _2, and 4-9% of claims 4 glass, wherein the substantially consists K ₂ O. 6. Expressed in weight percent on an oxide basis,
Moreover, 0-3% of BaO, 0-1% of Li ₂ O, 0-
3% SrO, 0-1% of the TiO _2, 0-1% of the Mg
O, 0-0.5% of F, 0-0.2% of SO _3, and 0
Comprises 0.5% _{Cl, Li 2 O + Na 2} O + K 2 O total 13-22% of, MgO + SrO + BaO total of 0-7
%.