JPH0316932A - Optical glass for precision press-molding - Google Patents

Abstract

PURPOSE:To provide an optical glass for precision press-molding, having a specific oxide composition, a yield temperature of <=570 deg.C and refractive index and Abbe number falling within a range defined by three specific points and moldable by press-molding at an extremely low temperature. CONSTITUTION:The objective optical glass for precision press-molding and having low softening temperature, high refractive index and low dispersion has a composition of (A) 23-30wt.% of B2O3, (B) 0-6wt.% of SiO2 (A+B is 26-33wt.%). (C) 0-23wt.% of La2O3. (D) 0.4-34wt.% of Gd2O3, (E) 0-14wt.% of Y2O3 (C+D+E is 1-43wt.%), (F) 3-5wt.% of Li2O, (G) 0-24wt.% of ZnO, (B) 0-7wt.% of ZrO2, (I) 0-15wt.% of Ta2O5, (J) 0-3wt.% of Nb2O5 (H+I+J is 0-19wt.%), (K) 20-41wt.% of LaF3, (L) 0-19wt.% of GdF3 and (M) 0-15wt.% of YF3 (K+L+M is 20-60wt.%), a yield temperature of <=570 deg.C and a refractive index and an Abbe number falling within the range defined by the points A, B and C of the figure.

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-formed at extremely low temperatures.

Prior Art Conventionally, there is a high refractive index, low dispersion type optical glass (nd = 1.70 or higher, νd = 47.5 or higher) that has similar optical constants. As the glass, phosphate glass (JP-A-60-122749
No. 79839, European Patent No. 1
Specification No. 9342, see! ]6. ), fluorophosphate glass (Japanese Unexamined Patent Application Publication No. 1983-1985, 65-96-41,
JP-A-58-2-17451, reference), porosilicate glass (JP-A-62-123040, reference)
Kachiwa is calm.

However, the conventional high refractive index low dispersion type (nd=1
．． 70 or higher, νd = 47.5 or higher), there is only one with a yield temperature (At) of 670°C or higher, and the pressing temperature must be high enough to exceed 700"C to form it. With known mold materials for precision press molding, the limit of press molding temperature is less than 650°C, preferably 600°C or less, and higher temperatures may cause oxidation of the mold material. Problems occur and it is difficult to maintain surface precision, making it unsuitable for mass production of lenses.For this reason, the pressed glass is 4H, which is as low as possible.
It is desirable that the material can be molded at a high temperature. In order to solve these problems, the above-mentioned publications on glass for press molding have been proposed. However, the glass of these threads is
The light ``i'' fil ability that Masaaki Hon is aiming for does not meet the high requirements of the fil ability, so it will not be released. Looking at the claims in each of the above-mentioned Zunanocchi publications, it cannot be seen whether the glasses cited therein exhibit the high refractive index and low dispersion that is the object of the present invention. Further, some of the above-mentioned publications contain lead as a glass component, but if lead is included, lead volatiles will adhere to the mold material, causing problems in maintaining surface accuracy, etc. Furthermore, there are some that are insufficient in terms of chemical durability.

Furthermore, fluoroborate glass (Japanese Unexamined Patent Application Publication No. 59-146952) is known as a glass that can partially satisfy the high requirements aimed at by the present invention. The glass contains lead as a glass component, as in the above publication, and is not suitable as a glass for press molding. Therefore, the first object of the present invention is to provide an optical glass for precision press molding, JJ2, which allows precision pressing to be carried out at extremely low quality (f300'C or higher).

A second object of the present invention is to obtain point A (1,
700, 58.5). B (1,700, 47.5).
The object of the present invention is to provide a high refractive index, low dispersion optical glass having a refractive index (nd) and Athe number (vd) within the range surrounded by the three points C (1.765, 47.5).

Means for Solving the Problems The inventors of the present invention have considered the various drawbacks of conventional optical glasses and optical glasses for press molding as described above, and have developed the following research results: B203. Li20, Gd203. La
F': Within the specified composition range, optical glass with a glass composition that requires + has a high refractive index, low liquid, and light that is not found in optical glasses for press molding. fliiiλ, is it softer than the optical glass of 11, t, low breakout, and 7? They found that it has almost no effect on the mold material in mass production of press molding, and came to the conclusion that it is optimal as an optical glass for precision press lenses that does not require grinding or polishing after press molding, leading to the present invention. This is what I did.

That is, if the present invention is expressed in weight%, 8203 23-30 weight/weight% (hereinafter expressed in %) Si0■ 0-6% f(1, total amount of B203+sioz 26-33% La. 203 0-23% Gd203 0
．． 4-34% Y203 0-14% However, the total amount of La203+Gd203+Y203 is 1-43% Li203-5
%Z n 0 0 ~ 2 4
%Zr0 2 0 ~ 7
%Ta20, 0~1
5%Nb20. ．． 0 ~
3% However, i' az O s + Z
r O 2 + N b 2 0 5 combination 5], 0 to 19% L a F 3 2 0 to 4 1
%Gd. F3
0 to 19%YFs
O ~ L 5% However, L
It has a composite strength consisting of a total amount of 20 to 60% of aF3+GdFs+YF3.

This invention. The range of each component of the optical glass related to the above is as follows.
The reason for limiting the scope to the following is as follows.

B20s is a main component constituting the glass network, and is effective in stabilizing the glass, lowering the yielding temperature (At), and lowering the dispersion. However, if it is less than 23%, the glass becomes unstable, and if it is more than 30%, the chemical durability deteriorates.

Sin2 is B20. It is also a component of the glass network, and is effective in stabilizing the glass.

However, if it exceeds 6%, the glass becomes unstable, so it should be within a certain range.

Further, if the total amount of B z O 3 and SiO2 is less than 26%, the glass becomes unstable, and if it exceeds 33%, chemical durability deteriorates and predetermined optical constants cannot be obtained.

L a2 0 s, Gd2O30s, and Y203 are effective components for achieving a high refractive index and low dispersion in terms of optical performance.

However, if the content is less than 1%, the effect cannot be obtained, and if it is more than 43%, the glass becomes extremely unstable, so it should be within a predetermined range.

When the amount of L D 2 0 3 exceeds 23%, the tendency to see through increases.

Gd20s gives glass the same optical properties as La20j, and has the effect of reducing the glass's tendency to show through, but if its amount increases or decreases by more than 0.4% to 34%, the glass will no longer have a tendency to show through. It becomes increasingly unstable.

When the amount of Y20 exceeds 14%, the tendency to see through increases.

Ta20g, Z r O 2 and Nb20s are effective components for adjusting refraction and dispersibility, and further improving chemical durability. However, if the content exceeds 19%, the softening temperature will increase.

Ta++()s is a component for stabilizing the glass and increasing the refractive index, but if it exceeds 15%, it increases the softening temperature.

Like Ta20a, ZrO2 is effective in increasing the refractive index of glass and further improving chemical durability. However, if it exceeds 7%. This increases the softening temperature, increases the dispersion, and further increases the tendency to seep.

When Nb20g exceeds 3%, the arrow tendency increases.

ZnO is more effective in lowering the softening temperature of glass than other components. It is also a very effective component for adjusting optical constants. However, if it exceeds 24%, the tendency to see through will increase, so it should be within a predetermined range.

When L i 2 0 is added in an appropriate amount as a small amount of essential component, it has the effect of lowering the temperature during press molding significantly more than other alkaline components without causing a decrease in chemical durability. However, if it is less than 3%, the effect is small;
%, the stability of the glass will be impaired.

LaFs and -G d F . and YF a are very effective components for increasing the refractive index and lowering the dispersion of glass,
Furthermore, Law's and G d 2 0 3 and Y20
Increasing the amount of oxide components such as No. 3 increases the tendency for glass to become transparent, whereas the three fluoride components mentioned above have a tendency to markedly increase the stability of the glass. However, if the content is less than 20%, the above effect is insufficient, and 60%
If the amount increases, volatilization during glass melting increases, making it difficult to obtain homogeneous glass.

L a F ; is an essential component in the present invention, but 2
If it is less than 0%, the above effects will be small, and if it is more than 41%, it will not be possible to obtain the desired optical constants, and furthermore, volatilization will increase during melting.

By mixing GdFj and YF3 with LaF3 and using 10, one component of LaF3 becomes 45'=
Although it increases the stability of the glass more than when it is melted, if both exceed 19% and 15%, there will be a lot of volatilization during melting, making it difficult to obtain a homogeneous glass. In addition to the above-mentioned components, the optical glass of the present invention contains, in order to adjust optical performance, improve meltability, expand vitrification range, lower softening temperature, etc.
Unless it departs from the purpose of the present invention, Na. K. Cs. S
r. C. a. Metallic oxides and fluorides such as Ba, Ga, In, and more. BFs. ZnF2. ZrF. ．． 1
'aF+, etc. can be contained.

Examples Next, the compositions (values are %) and refractive index (nd) of examples according to the present invention. Abbe number (yd). The yielding temperatures (At) are shown in Table 1.

Table 11 12 1 3 The optical glass of the present invention uses oxides, hydroxides, fluorides, carbonates, nitrates, etc. corresponding to each of the seven as raw materials for each component, and weighs them in predetermined proportions. , mix thoroughly and put it into a platinum crucible as glass preparation raw material and heat it in an electric furnace at 900℃~
It is made by melting it at 1200"C, stirring it with a platinum stirring rod to clarify and homogenize it, then casting it into a preheated mold to an appropriate temperature, and then slowly cooling it. Note that the blue color of the glass The effect of the present invention is not affected by the addition of As203 a little too early for prevention and defoaming, or by the addition of a small amount of a defoaming component which is well known in the industry.

Effects of the Invention According to the present invention, the yield temperature (At) is 570°C or less,
and point A (1.700, 58.5) shown in FIG. B
(1.700, 47.5)C (1.765, 47.
It has a refractive index (nd) and Abbe number (νd) within the range surrounded by the three points in 5), is stable against arrow penetration, can be precision pressed at extremely low temperatures, and can be ground or Optical glass for precision press lenses that does not require polishing
5 is obtained.

4.

[Brief explanation of drawings]

No. Figure 1 is The optical constant range of the glass of the present invention is shown. Optical constant diagram (nd νd diagram) It is.

Claims (1)

[Claims] B_2O_3 23 to 30% by weight (hereinafter expressed as %) SiO_2 0 to 6% However, the total amount of B_2O_3 + SiO_2 is 26 to 33% La_2O_3 0 to 23% Gd_2O_3 0.4 to 34% Y_2O_3 0 to 14% However, La_2O_3+Gd_2O_3+Y_2O_3
Total amount of 1 to 43% Li_2O 3 to 5% ZnO 0 to 24% ZrO_2 0 to 7% Ta_2O_5 0 to 15% Nb_2O_5 0 to 3% However, total amount of Ta_2O_5 + ZrO_2 + Nb_2O_5 0 to 19% LaF_3 20 to 41% GdF_3 0~ 19% YF_3 0~15% However, the total amount of LaF_3+GdF_3+YF_3 is 20~
60% composition, the yield temperature (At) is 570°C or less, and points A (1.700, 58.5) and B (1
．． 700, 47.5), C (1.765, 47.5), and has a refractive index (nd) and Abbe number (νd) of extremely low softening temperature, high refractive index, and low dispersion. Optical glass for precision press lenses.