JPS60122745A - Optical glass - Google Patents

Abstract

PURPOSE:To develop the titled optical glass having small sp.gr., a high refractive index, and low dispersion by adding Nb2O5 and CaO having comparatively small sp.gr. and affording a high refractive index into an optical glass composition. CONSTITUTION:An optical glass is the glass having the following composition. A starting material is melted, homogenized, and annealed to obtain the glass contg. 0-22% SiO2 and 3-30% B2O3 where SiO2+B2O3=20-30%, 18-37% La2O3 and 0-8% Y2O2 where La2O3+Y2O3=18-37%, 8-22% Nb2O5, 1-8% ZrO2, 10-24% CaO and 0-10% MgO where CaO+MgO=10-24%, <10% ZnO, <5% BaO, <8% SrO, <5% PbO, <2% TiO2, <5% Ta2O5, <5% WO3, <5% metallic oxide such as Na2O and K2O, <6% Al2O3, and <6% P2O5. The high-refractive index and low-dispersion optical glass having >=1.78 nud, >=38 nud, and <4.3 sp.gr. can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides that nd≧1.78. Sid≧38. This invention relates to an optical glass having a specific gravity of 4.3.

Many optical glasses that satisfy the above optical constants are already known. For example, in Japanese Patent Publication No. 36-1394,
Glass containing ThO2, CdO, and
632633 discloses a glass containing a large amount of Gd2O3.In addition, a glass containing a large amount of Gd2O3 is taught. There are many known glasses containing ZnO, Ta?Os, etc., as shown in Japanese Patent Laid-Open Publication No. 101414/1983.However, these conventional glasses contain La2O3.

Since it contains a large amount of ZNO, Ta205, etc., it usually has a high specific gravity.

However, in recent years, in the field of optical equipment, the market trend has been toward smaller and lighter lenses, and there is a strong desire to develop lightweight lens materials.

The purpose of the present invention is to eliminate the harmful substance ThO2゜CdO'v
Does not contain Gdz 03, an expensive component, and has a specific gravity of 4.
It is an object of the present invention to provide a high refractive index, low dispersion glass having an optical constant of less than 3 and having an optical constant within the above range. are Nb2O5 and C giving relatively small specific gravity.
This is achieved by containing aO as an essential component and strictly limiting the content of components that increase specific gravity and dispersion.

, that is, the optical glass of the present invention has a weight percentage of 5N)
2+8203 20~30,5tOz O~22B20
3' 3~3G, L a203 +Y203 18
~37, La2O318~37. Y203 0~BN
bz Os 8~22.7r02 1~'8゜cao+
MQo io ~24. CaO10~24゜MQOO~
10. ZnO<19. L3aO<5°SrO<8. Pb
O<5. T' io? <2°Ta205<5. WO3<
5. “PJLi force”) Metal oxide <5.AI2! 03
<6. It has a composition of P20s<6, and nd≧1.78
．． v d≧38. It is characterized by having a specific gravity of 4.3.

Regarding the optical glass of the present invention, the reason for limiting the constituent components is that if the content of SiO2 and B203 exceeds 30%, the desired high refractive index cannot be obtained, and if the content is less than 20% at the abutment, the glass becomes unstable. Become. Also, S! Similarly, if B2O2 exceeds 22% or B2O3 becomes less than 3%, the glass becomes unstable.

18% or more of La2O3 is required to maintain a high refractive index and low dispersion, but since this component greatly increases the specific gravity, 37
% or less. It is effective because it gives optical constants equivalent to Y2 (1 + a?03 and has a smaller specific gravity than LazO:+, but since it is an expensive raw material v1, it should be limited to 8% or less.Nb2O5 is It is an essential component to obtain a high refractive index and low specific gravity, and requires at least 8%.
If it exceeds 22%, the desired high Atsube number cannot be maintained.

ZrO2 gives almost the same specific gravity as Nb2O5, and
Since the number is increased, 1% or more is required, but if it exceeds 8%, the devitrification resistance will deteriorate rapidly. CaO stabilizes the glass and gives it a low specific gravity, so 10% or more is necessary, but if it exceeds 24%, the glass becomes unstable. Mg
O can be partially replaced with CaO without increasing the specific gravity, but if it exceeds 10%, the devitrification resistance deteriorates. Other components are mainly added for the purpose of adjusting optical constants, improving devitrification resistance, improving meltability, etc.
nO, Bao, SrO, pbo, Ta205. WO3 is a component that increases specific gravity, so it is 10%, 5%, and 8%, respectively.
, 5%, 5%, limited to less than 5%. Further, JfO2 reduces the number of bubbles and strengthens the coloring, so it is limited to less than 2%, and alkali metal oxides and Al203P205 deteriorate the devitrification resistance, so they are limited to less than 5%, 6%, and 6%, respectively.

In addition, a small amount of AS203, S for the purpose of clarifying, embellishing, etc.
This does not preclude addition of b203, F, etc.

Examples of the present invention (each component number and weight %) are shown in the following table. (
(Left below) These glasses are made by heating a mixture of commonly used IFI powder, lanthanum borate, niobium oxide, zirconium oxide, calcium carbonate, etc. in a platinum crucible at 1,300~
It can be produced by melting at 1350°C, stirring to homogenize and remove bubbles, preheating at an appropriate temperature, pouring into a mold and slowly cooling.

Patent Applicant Rei Hoya Glass Co., Ltd. Agent Masayuki Asakura Procedural Amendment Guide (Method) % Formula % 1. Indication of the case 1982 Patent Application No. 229948 @ 2. Name of the invention Optical Glass 3. Person making the amendment Related Patent Applicant: Hoya Glass Co., Ltd. 4, Agent: Ozato Kaikan 5, 1-18-14 Nishi-Shinbashi, Minato-ku, Tokyo, Date of Amendment Order: February 28, 1980, 6, Subject of Amendment

Claims (1)

[Claims] (At 21% by weight S io2+B203 20-30 Si02 0-22 B203 3-30 Laz 03 +Y203 18-37 3°L az
03 18~37 Y203 0~8 Nb20s 8~22 Zr02 1~8 CaO+MCl0 10~24 CaO10~24 MaOO~1゜zno <10 [3aO<5 SrO<8 PbO<5 TiO2<2 Ta2 ()s <5 WO 3 <5 Alkali metal oxide 5 A+203 <6 P205 , <5 It has the following composition, nd≧1.78, sid≧38. Optical glass having a specific gravity of <4.3.