JPS61168551A - Glass for glasses having high refractive index - Google Patents

Abstract

PURPOSE:To produce glass for lightweight glasses having high refractive index, by producing lens for glasses from glass consisting of base seven components of SiO2, B2O3, CaO, La2O3, TiO2, ZrO2, and Nb2O5, having specific properties. CONSTITUTION:Lens for glasses is produced from glass of seven component system containing 9-15wt% SiO2, 10-17wt% B2O3, 12-20wt% CaO, 30-40wt% La2O3, 10-15wt% TiO2, 3-8wt% ZrO2, and 1-10wt% Nb2O5. Lightweight lens for glasses having high refractive index, having 1.81-1.89 refractive index n4, 28-37 Abbe's number nu4, 80X10<-7>-100X10<-7> coefficient of linear expansion in 20 deg.C-300 deg.C temperature range, and 670-710 deg.C softening temperature is obtained from this glass.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a glass for spectacle lenses having an extremely high refractive index n4 of 1.81 to 1.89.

In particular, the present invention relates to a chemically durable glass used as a material for beads (also called segments or buttons) of bifocal or trifocal eyeglass lenses.

BACKGROUND OF THE INVENTION A bifocal or trifocal eyeglass lens consists of one glass lens (
A small lens with a high refractive index is attached to a part of a glass plate (called a plateau or lens blank) to provide two or three focal lengths for distance and near vision. It is manufactured by welding small glass beads with a high refractive index into the recessed parts.

In conventional multifocal lenses, the refractive index is 1.52 as the base.
No. 3 crown glass for glasses is used, and as a small ball,
Glass having a higher refractive index na=1.58 to 1.70 (the refractive index is appropriately selected from the above range depending on the degree of vision correction required) is used.

However, recently, a lightweight, high-refractive-index glass for eyeglass lenses has been developed, which has a refractive index of 1.70, which is higher than that of conventional crown glass for eyeglasses, and has a lower density.
It has become commercially available. This type of glass is particularly appreciated by wearers with high visual acuity, as it reduces the edge thickness of the lens, makes it lighter, and eliminates the swirly appearance. , has been well received by the general public due to the recent trend towards weight reduction.

The applicant has previously determined that the composition is in weight%, this 11-53% Ca0
25~43 TiOz + NbzOs 8~19 However, Ti0□ 0~15 SiOz O~36Y20
KO~11SrO+BaO
+ZnOO~? Zr0z O~11LizO
+KzO+NazOO~ 4 Mg0 O~1Opbo
o ~ 4^It'3
0 ~4Law'3
0 to 15 TatOs
O~19No,
Q ~11, refractive index n4 is 1.68~1
．． 71, a patent application was filed for a lightweight, high-refractive-index glass for eyeglass lenses with a specific gravity of 2.88 to 3.18 (Japanese Patent Application Laid-open No. 109-1983)
No. 514).

Incidentally, as general eyeglass lenses become lighter and have higher refractive indexes, there is an increasing demand for multifocal eyeglass lenses to be lighter and have higher refractive indexes as well. Therefore, if the base glass is replaced with a lightweight, high-refractive-index glass, it is natural that the small glass should be changed to a suitable one. The coefficient of thermal expansion αXl0-' (especially the coefficient of thermal expansion α×10-' at 20-300°C) must be almost the same (the difference in α is within ±5). , the refractive index should also be preferably higher than 0.1.

(Object of the invention) Therefore, the object of the present invention is to solve the problem of the previous invention (
When using the lightweight high refractive index glass of JP-A No. 53-109514 (Japanese Unexamined Patent Publication No. 109514/1989) or the II mirror glass having an equivalent refractive index, an equivalent coefficient of thermal expansion, and an equivalent softening temperature, the refractive index is at most suitable for small glass beads. Our goal is to provide glass. In particular, the present invention has a refractive index n6 of 1.81 to 1.89.
, an Atsbe number νd of 28 to 37, a coefficient of thermal expansion (αX 10-') α of 80 to 100 in a temperature range of 20 to 300°C, and a softening temperature of 670 to 710°C. It's about doing.

(Summary of the Invention) As a result of intensive research, the present inventor discovered that SiO□-B, 0
s-CaO-La2O2-TiO, -ZrOz-Nbt
We discovered that among the glasses consisting of the seven basic components of Os, the following composition meets the purpose.
The present invention has been accomplished.

Therefore, the present invention provides Si0□ 9-15 B! in weight %. It has a composition of Os 10-17 Ca0 12-20 1, atO+ 30-40 TiO210-15 ZrO23-8 NbzOs 1-10, a refractive index n4 of 1.81-1.89, and an asobe number ν of 28-37. .Thermal expansion coefficient in the temperature range between 20°C and 300°C is 80 x 10-7 to 100
Provided is a glass for eyeglass lenses having a softening temperature of 670 to 710°C.

Next, the reason why the composition ratio of glass is limited in the present invention will be described.

SiO2 has the effect of increasing the viscosity of glass and reducing the tendency for devitrification, and is an indispensable component in melting on a mass production scale. It also works to enhance chemical durability and mechanical strength, which are particularly important in applications such as eyeglass glasses. Therefore, 9 to 15% (% means weight %, the same applies hereinafter) is necessary; less than 9% is practically preferred for the above reasons, and more than 15% causes unmelted materials to obtain a homogeneous glass. This makes it difficult to obtain predetermined optical constant values.

B20. If it is less than 10%, the tendency of glass to devitrify increases,
If it exceeds 17%, predetermined optical constant values cannot be obtained.

When CaO is less than 12%, the devitrification stability of the glass decreases,
On the other hand, if it exceeds 17%, predetermined optical constant values cannot be obtained.

La, 0. is an important component because it gives glass a high refractive index and low dispersion, but if its amount is less than 30%, it will be difficult to obtain the desired optical constant value, and if it exceeds 40%.

The tendency to devitrification increases.

TiO□ has the effect of increasing the refractive index and improving the chemical durability of the glass. If it is less than 10%, it becomes difficult to obtain a predetermined optical constant value, while if it exceeds 15%, the tendency to devitrify increases.

7rrOt is an effective component for increasing the refractive index and stabilizing glass, and also has the effect of improving chemical durability.If it is less than 3%, these effects are insufficient, and if it exceeds 8%, it will not be absorbed into the glass. The meltability of the glass deteriorates, making it difficult to obtain a homogeneous glass.

Nb! O, is an effective component for increasing the refractive index and stabilizing the glass; if it is less than 1%, it is ineffective, and if it exceeds 10%, the tendency to devitrify increases.

In the glass of the present invention, in addition to the above seven basic components,
Other ingredients such as Ljz may be used as long as they do not impair the purpose of the present invention.
O+ Na1O+ Mg0I SrO,Ha(L Zn
(L PbO+^1lzOs.

YzOs, YtlzO3+ GdJs+ TazOs
+ too, etc. may be added.

The glass according to the present invention uses the corresponding oxides, carbonates, sulfates, etc. as raw materials for each component, collects them in the desired ratio, adds a fining agent if necessary, and thoroughly mixes the powder to form a raw material. This can be produced by putting it into a platinum crucible in an electric furnace heated to 1200 to 1300°C, melting it, clarifying it, stirring it to make it uniform, then casting it into an iron mold and slowly cooling it.

(Example) The following table shows the composition (% by weight), refractive index (na), Atsube number (νd), coefficient of thermal expansion (αXl0-'), and glass softening temperature of Examples according to the present invention. (^t
) is shown.

Table 1 Table 1 ('ll1t) Table 1 (continued) Table 1 (M) (Effects of the invention) As described above, according to the present invention, the refractive index nd is 1.81.
~1.89, Atsbe number νd is 28~37.20℃~30
Thermal expansion coefficient in the temperature range between 0℃ (α×101)
A high refractive index glasses lens glass having an α of 80 to 100 and a softening temperature of 670 to 710°C can be obtained.

Therefore, within this range, the thermal expansion coefficient α is approximately equal to that of the base glass (particularly those selected from the glass composition of the invention of JP-A-53-109514 or its equivalent), and the softening temperature is equal or It is possible to select a glass with a low and high refractive index, and if a small lens is made from the selected glass, it can be bonded extremely well to a gold lens.

Claims (1)

[Claims] It has the following composition in weight% and has a refractive index n_d of 1.81.
~1.89, Abbe number ν_d is 28~37, 20℃~3
Thermal expansion coefficient in the temperature range between 00℃ and 80×10
^-^7~100x10^-^7, softening temperature is 670~
Glass for eyeglass lenses at 710℃. SiO_2 9-15 B_2O_3 10-17 CaO 12-20 La_2O_3 30-40 TiO_2 10-15 ZrO_3 3-8 Nb_2O_5 1-10