JPH0337130A - Optical glass for precise press molding - Google Patents

Abstract

PURPOSE:To produce the subject optical glass capable of carrying out press molding at extremely low temperature by preparing the optical glass consisting of a specific ratio of SiO2, B2O3, Li2O, Na2O, BaO, CaO, ZnO, La2O3; Gd2O3, Al2O3 and ZrO2 and specified in At, nd and nud. CONSTITUTION:The optical glass for precise press lens consisting of 20-40wt.% SiO3 and 11-12wt.% B2O3 in which total amount of SiO2 and B2O3 is 43-55wt.%, 3-8wt.% Li2O and 0-6wt.% Na2O in which total amount of Li2O and Na2O is 7-11wt.%, 0-22wt.% BaO and 0-16wt.% CaO, 0-23wt.% ZnO and 2-21wt.% La2O3 and 0-15wt.% Gd2O3 in which total amount of La2O3 and Gd2O3 is 4-29wt.% and 0.5-5.0wt.% Al2O3 and 0.2-3.0wt.% ZrO2, having 550 deg.C refractive temperature, 1.59-1.65 refractive index, >=54 ape number, extremely low softening temperature and middle refractive index and low dispersion is prepared. Thereby optical glass practically usable for a long time is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical glass for precision press lenses that can be press-molded at extremely low temperatures.

Conventional technology The medium refractive index low dispersion type (n d = 1.59 or more, νd = 54
(above) optical glasses exist.

In addition, as glass for press molding, phosphoric acid tomb glass (JP-A-55-154343, JP-A-58-79)
(See Publication No. 839, Japanese Unexamined Patent Publication No. 122749/1983)
, fluorophosphate glass (JP-A-56-59641
Publication No. 149343/1983, Japanese Patent Application Laid-open No. 1982-149343
-217451), fluoroborate glass (see
(see Japanese Patent Laid-Open No. 59-146952) is known.

Problems to be Solved by the Invention However, the conventional medium refractive index and low dispersion type (n d
= 1. 59 or higher, νd = 54 or higher), the only optical glasses that have a yield temperature (At) of 630°C or higher exist, and cannot be formed unless the pressing temperature is high, exceeding 700°C. Ta. In known mold materials for precision press molding, the limit of press temperature in mass production is less than 650 °C, preferably 600 °C or less,
If the temperature is higher than that, problems such as oxidation of the mold material may occur.
It is difficult to maintain surface accuracy and is not suitable for mass production. Therefore, it is desirable that the glass to be pressed be able to be formed at the lowest possible temperature. In order to solve these problems, the above-mentioned publication on glass for press molding selects phosphoric acid and boric acid as glass-forming oxides. However, although phosphoric acid and boric acid are advantageous in lowering the press forming temperature, they tend to cause problems in the chemical durability and weather resistance of the glass. Furthermore, if the chemical durability and weather resistance of the glass deteriorate, it not only leads to deterioration of the surface precision in the case of the breath acid type, but also makes it impossible to use the glass in long-term practical use. In addition, the introduction of fluorine as seen in the above publication is advantageous in lowering the press temperature and lowering dispersion, but it increases volatilization during glass melting, making it difficult to obtain a stable and homogeneous glass. . In addition, it is likely to cause problems with the environment and the like. Glass containing lead is also seen in the above patent, but if lead is included, lead volatiles adhere to the mold material, which tends to cause problems in maintaining surface accuracy. In addition, borosilicate glasses similar to those of the present invention (see Japanese Unexamined Patent Publication No. 123040/1982) are known, but these glasses have the same problems in terms of chemical durability as the above-mentioned publications. . In other words, these glasses comply with the Japan Optical Glass Industry Association standard JOGIS-06-1975.
When a chemical durability test was actually conducted using the measurement method, the water resistance rank was 3 or less, which caused problems in long-term practical use. In actual practical use, a water resistance rank of 2 or higher is appropriate.

Therefore, the first object of the present invention is to achieve extremely low temperatures (6
An object of the present invention is to provide an optical glass for precision press molding, which can be precision pressed at temperatures below 00°C.

The second object of the present invention is to have a refractive index (nd) of 1.5.
The object of the present invention is to provide an optical glass that has a medium refractive index and low dispersion of 9 to 1o65 and an Abbe number (νd) of 54 or more, and has very good chemical durability and weather resistance that can withstand long-term practical use. .

Means for Solving the Problems The inventors of the present invention took into account the drawbacks of conventional optical glasses and optical glasses for press molding as described above, and as a result of various studies and studies, 5iOz, Bt Ox, Lit O%La.
Optical glass with a glass composition that requires g Os, Alx 0ZrO* has almost the same optical constants as medium refractive index low dispersion type optical glass (nd-1°59 or higher, cid-54 or higher). , and can be press-formed at a much lower temperature than those, with almost no effect on the mold material.
And furthermore, than the optical glass for press molding of the above patent,
Optical for press lenses that have excellent stability, chemical durability, weather resistance, and meltability, can be handled in the same way as conventional optical glasses, and have a low yielding temperature (At), so they do not require grinding or polishing after press molding. The present invention was achieved by discovering a glass composition that is optimal as a glass.

That is, if the present invention is expressed in weight percent, 5iOz Btus however, iOx +Bt 20-40 11-22 Total amount of Ol 43-55 3-8 0-6 Li*0 Nan.

however, L is O+Na* BaO BaO n0 La, O.

Gd,Os however, atex 1s Os ZrO* Total amount of O 7-11 0-22 0-16 0-23 2-21 0-15 +Gdt Total amount of Ox 4-29 0 5-5.0 0, 2-3. 0 It has a composition consisting of:

The reason why the range of each component of the optical glass according to the present invention is limited as described above is as follows.

SiO* is the main component that makes up the glass network, but 4
If it exceeds 0%, the viscosity during melting increases, leading to an increase in the softening temperature. On the other hand, if it is less than 20%, the tendency to devitrify increases and chemical durability deteriorates.

B, 0. has a glass mesh similar to 5ins,
It is an effective component for stabilizing glass. It is also effective in homogenizing glass, and furthermore, by containing it in an appropriate amount, it lowers the softening temperature. However, if it is less than 11%, the above effect will be small, and if it is more than 22%, chemical durability will deteriorate.

Furthermore, if the total amount of SiO* and Btus increases or decreases by more than 43 to 55%, the desired optical constants will not be obtained, so it should be within a predetermined range.

By containing Li*O in an appropriate amount as an essential compounding component, it has the effect of significantly lowering the press molding temperature without impairing chemical durability compared to other alkaline components.

However, if it is less than 3%, the above effect will be small, and if it is more than 8%, the tendency to devitrify will increase.

Nano also contributes to lowering the press molding temperature, but if it exceeds 6%, not only does the tendency for devitrification increase, but also the chemical durability deteriorates.

Furthermore, if the total amount of Li, O and Na, O is less than 7%, the effect on lowering the softening temperature will be small, and if it is more than 11%, the chemical durability of the glass will deteriorate, so it should be within the specified range. .

ZnO is an optional compounding component and is a very effective component for lowering the softening temperature and adjusting optical constants, but if it exceeds 23%, the tendency to devitrify increases.

BaO is an optional compounding component, and is an effective component for increasing the refractive index and lowering dispersion. However, the use of a large amount of BaO deteriorates the chemical durability of the glass, so the amount used is 22%.
within.

CaO is an optional compounding component, and is an effective component for improving chemical durability and adjusting optical constants, but when it exceeds 16%, the tendency to devitrify increases.

La*Os is an essential compounding component and is very effective in achieving a high refractive index and low dispersion of glass. It is also an effective component for improving chemical durability. However, if it is less than 2%, the above effect will be reduced, and if it is more than 21%, the softening temperature will increase.
Increases devitrification tendency.

Gd and 03 are optional ingredients, and La.

It is used in conjunction with 03 to adjust optical performance, but 15%
If the amount is higher, the softening temperature will increase.

Furthermore, if the total amount of La*Ox and G d t Os is less than 4%, the desired optical constants cannot be obtained, and if it is more than 29%, it not only impairs the stability of the glass but also increases the softening temperature. Therefore, Zr0t, which is within this range, is a component that has a very important meaning in the present invention, and by adding an appropriate amount as an essential component in a small amount, the chemical durability of the glass is significantly improved. However, 0. If it is less than 2%, the above effect will be small, and if it is more than 3%, the tendency to devitrify will increase.

A1. O, is an essential compounding component, and like ZrO, it is very effective in improving the chemical durability of glass, but 0.5%
If it is less than 5%, the effect will be small, and if it exceeds 5%, the softening temperature of the glass will increase, so it should be within the specified range.

In addition to the above-mentioned components, the optical glass of the present invention includes, in order to adjust optical performance, improve meltability, expand the vitrification range, etc.
Unless it departs from the purpose of the present invention, S ro%Tas
Os, MgO.

Y203 I rlt o3, Gas Ox, etc. can be contained.

Next, the composition of the examples related to the present invention (values are weight %),
Refractive index (nd), Atsube number (νd), yielding temperature (At
) and water resistance (rank) are shown in Table 1. Regarding water resistance (Rw), please refer to the Japan Optical Glass Industry Association standard JOGI.
This was conducted according to the chemical durability measurement method of S-06-1975. That is, standard mesh sieve 420-590
A powdered glass sample that remains within μm was treated in pure water at 99°C or higher for 60 minutes, and the weight loss rate (%) of the sample before and after treatment.
This is a method of determining the weight loss rate and classifying the weight into the six classes shown in Table A.

Table 1: The optical glass of the present invention uses corresponding oxides, hydroxides, carbonates, nitrates, etc. as raw materials for each component, and
Weighed and thoroughly mixed at a predetermined ratio, the raw materials for glass preparation were put into a platinum-type crucible and heated in an electric furnace to 1,000 to 13
After melting at 00℃, stirring with a platinum stirring wire to clarify and homogenize, and casting into a mold preheated to an appropriate temperature,
Prepare by slowly cooling. In addition, a small amount of As and 0.0% are added to prevent coloring of the glass and to defoam. or the addition of a small amount of a defoaming component which is well known in the industry does not affect the effect of the present invention.

Effects of the Invention According to the present invention, the yield temperature (At) is 550°C or less,
Refractive index (nd) is i, 59-t.

65, has an optical constant with an Atsube number (νd) of 54 or more,
Optics for precision press lenses that are stable against devitrification, have very good chemical durability that can withstand long-term practical use, can be precision pressed at extremely low temperatures, and do not require grinding or polishing after press molding. glass is obtained.

Claims (1)

[Claims] SiO_220-40% by weight (hereinafter expressed as %) B_2O_311-22% However, total amount of SiO_2+B_2O_3 43-55% Li_2O3-8% Na_2O0-6% However, total amount of Li_2O+Na_2O 7-11% BaO0 ~22% CaO0-16% ZnO0-23% La_2O_32-21% Gd_2O_30-15% However, the total amount of La_2O_3+Gd_2O_3 is 4-29% Al_2O_30.5-5.0% ZrO_20.2-3.0% or more. (At) is 550°C or less, the refractive index (nd) is 1.59 to 1.65,
An optical glass for precision press lenses with an Abbe number (νd) of 54 or more and an extremely low softening temperature, medium refractive index, and low dispersion.