JPH035341A - Optical glass - Google Patents

Abstract

PURPOSE:To obtain optical glass having low electric resistance, a low yield point and superior chemical durability by blending SiO2+B2O3 with Li2O, BaO and La2O3+Al2O3+ZrO2+TiO2 in a specified ratio. CONSTITUTION:This optical glass has a compsn. consisting of, by weight, 36-62% SiO2+B2O3 (23-62% SiO2 and 0-28% B2O3), 0.5-7% Li2O, 12-52% BaO, La2O3+Al2 O3+ZrO2+TiO2 (0.5-11% La2O3; 0-7% Al2O3, 0-8% ZrO2 and 0-2% TiO2), 0-5% Na2O, 0-5% K2O, 0-10% MgO, 0-15% CaO, 0-20% SrO and 0-14% ZnO and has 1.58-1.67 refractive index and 50-62 Abbe's number.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an optical glass having a composition having a refractive index (nd) of 1.58 to 50 and a refractive index (nd) of 50 to 62. In particular, it relates to optical glasses having the above optical constants and classified as barium crown glasses and heavy crown glasses.

[Prior art] nd 1. 58-1. Optical glasses having optical constants of 67 and d50 to 62 and classified as barium crown glass or heavy crown glass have been produced in large quantities for a long time.

[Problems to be Solved by the Invention] In recent years, direct current melting has been widely used in the production of optical glass, as it has superior thermal efficiency and generates less pollution than the conventional method of melting glass by gas combustion. This direct current melting uses Joule heat due to the electrical resistance of the glass melt to melt the glass.

However, nd 1.58-1.67, d50
Glass that has an optical constant of ~62 and is classified as barium crown glass or heavy crown glass has a problem in that it is extremely difficult to directly melt it with electricity because its electrical resistance value is too large.

Furthermore, in order to obtain optical glass molded products, so-called molding, which does not require a polishing process and obtains the final lens product only by pressing, has been attracting attention in recent years.

However, when molding is applied to glass classified as barium crown glass or heavy crown glass, the high yielding point of these glasses causes an increase in molding temperature, resulting in a decrease in molding accuracy and deterioration of the mold. cause. For this reason, it is desirable to lower the deformation point of glass as much as possible for mold forming, but in general, when trying to lower the deformation point of glass, the chemical durability of the glass usually decreases, so mold forming suitable,
It has been difficult to obtain barium crown glass or heavy crown glass that also has excellent chemical durability.

Therefore, the object of the present invention is to
, an optical constant of 50 to 62, a low electrical resistance suitable for direct current melting, a low yield point suitable for mold forming, and excellent chemical durability. There is a particular thing.

[Means for Solving the Problems] The present invention has been made to solve the above objects, and
The optical glass of the present invention has SiO+ +B+Ox 36~62w
t% (However, SiO+ 23-62wt%B
I03 0-28wt%) Li+0 0. 5-7wt%Ba
O12~52wt% La+Ox +Al103 +2rO++TiO+
1 to 18 wt% (However, La + Ot 0.5
~11wt%Al20xO~ 7vt% Zto+ 0~8vt% Ti1t O~2wt%) NaIo
20 to 0-5wt%
0~5wt%MgO0~10wt% CaOO~15vt% SrOO~20vt% Z port 0
It has a composition of 0 to 14 wt%, and a refractive index (n
d) is 1.58 to 1°67 and the Atsbe number (νd) is 50.
~62.

By strictly limiting the composition of the glass as described above, it has optical constants of nd 1.58 to 1.67 and sid 50 to 62, which are the objects of the present invention, and has low optical constants suitable for direct current melting. It becomes possible to provide optical glass that has an electrical resistance value, a low yield point suitable for molding, and excellent chemical durability.

The reasons for limiting each component are as follows.

SiO+ and Bl 03 are components that form the glass skeleton, and if the total amount is less than 36 wt%, nd will be too high, so 36 wt% or more is required, but if it exceeds 62 wt%, nd will be too low, so these The total amount of the components is limited to 36-62 wt%. In order to obtain glass with excellent chemical durability, it is necessary to
iQ1 is required, and B2O3 must not be contained in an amount exceeding 28 wt%. Therefore, the amount of Sigh is 23
~62wt%, and the amount of B+ Os is 0~28wt%
Each is limited to

Li1O is an effective component for lowering the electrical resistance value and yielding point of glass; Although 5wt% or more is required,
If the amount exceeds 7 wt%, the chemical durability of the glass and devitrification resistance will decrease, so the amount of Lil Q should be 0.
It is limited to 5 to 7 wt%.

BaO is an essential component to obtain the desired nd and νd, and is required in an amount of 12 wt% or more, but if it exceeds 52 wt%, the chemical durability of the glass will decrease, so the amount of BaO should be 1.
It is limited to 2 to 52 wt%.

La+Ox, AI+03.1ror, and TiO+ are components that improve the chemical durability of glass as well as effective components for improving devitrification resistance, and the total amount is 1wt%.
The above is necessary. Among them, La+03 has a remarkable effect and has many advantages such as not only having no adverse effect on melting properties but also being advantageous for obtaining glass with high refractive index and low dispersion, so Q: 5wt% or more is required. It is. However, since the raw materials for La+Os are relatively expensive, 11
It is not a good idea to contain more than wt%. AlIO3
When the amount exceeds 7 wt%, the devitrification resistance of the glass decreases,
The same applies when the amount of 1ror exceeds 8vt%. Furthermore, when the amount of Ti11 exceeds 2 wt%, the transmittance of the glass decreases. For these reasons, the amount of 1a103 is 0
．． 5-1 lvt%, the amount of AI + O kudzu is Q ~ 7 wt
%, the amount of Zr0I is limited to 0-8 wt%, the amount of TiO+ is limited to 0-2 wt%, and the total amount of these components is limited to 1-18 wt%.

Na+ 01K10, MgO, CaO, SrO and 200 are used in amounts of 0 to 5 wt%, O to 5 vt%, and 0, respectively, for the purpose of adjusting optical constants, improving devitrification resistance, improving meltability, etc.
It can be contained in the ranges of ~1Qvt%, 0-15vt%, 0-20wt%, and 0-14wt%, but exceeding each range will lead to a decrease in chemical durability and devitrification resistance. Therefore, the amounts of these components are limited to the above ranges.

In addition to the above-mentioned components, the optical glass of the present invention also contains commonly used defoaming agents such as AS+03 and Sb+03, and a small amount of F within a range that does not deteriorate the properties of the glass.
5PI05SPbO etc. can also be added.

The optical glass of the present invention is made of silica powder, boric acid, lithium carbonate, barium carbonate, lanthanum oxide, aluminum hydroxide, zirconium oxide, titanium oxide, sodium carbonate, sodium nitrate, potassium carbonate, potassium nitrate, and hydroxide, which are commonly used as raw materials. magnesium, magnesium carbonate,
Calcium carbonate, strontium nitrate, strontium carbonate, zinc oxide (zinc white), etc. are used, and a mixture of these raw materials is placed in a heat-resistant container such as a platinum crucible for 120 minutes.
Heat to 0-1400℃ to melt, stir and homogenize,
After removing the bubbles, it can be obtained by pouring into a mold preheated to an appropriate temperature and slowly cooling.

For melting the glass at this time, conventional methods including direct current melting can be directly applied, and for molding, conventional methods including molding can be applied as is.

[Example] Examples of the present invention will be described below.

Examples 1 to 4 As starting materials for the optical glasses of Examples 1 to 4, silica powder,
Using boric acid, lithium carbonate, barium carbonate, lanthanum oxide, aluminum hydroxide, zirconium oxide, titanium oxide, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, strontium nitrate, and zinc oxide (zinc white), these starting materials are Weighed each example so that the composition of the final glass would be as shown in Table 1, mixed thoroughly in a Zuizui mortar, and then coarsely melted the resulting mixture in a silica crucible. Cullet was obtained for each example.

Next, the obtained cullet was placed in a melting furnace made of zirconia electroformed bricks and melted by direct electric current to a temperature of 1250
After heating to ~1300°C to melt, stirring to homogenize, and removing bubbles, it was molded into a plate using a mold, and slowly cooled to obtain a plate-shaped optical glass. Next, a glass gob of a predetermined weight was cut out from the plate glass, a spherical preform was obtained by a conventional polishing method, and a total of four types of aspherical convex optical lenses were obtained by molding.

The refractive index (nd) and Atsube number (νd) of each optical lens obtained in this way with respect to the d-line of the helium lamp are
) and yield point were measured, nd was 1.589 ~
1.658, νd is 51-61, yield point is 570-59
5°C, and the optical lenses obtained in any of the examples also had
It was confirmed that it had the desired nd and vd as well as a low yielding point suitable for molding.

In addition, the acid resistance (Da) of the optical lens obtained in each example
and water resistance (Dw) were measured based on JOGIS (Japan Optical Glass Industry Association Standards) 06 1975.
Weight loss rate) and Dw were 0.01 to 0.06 wt% (however, weight loss rate), and it was confirmed that all optical lenses had excellent chemical durability.

Furthermore, when we measured the specific resistance of the optical lenses obtained in Examples 1 and 2, we found that they had a much lower electrical resistance value than conventional barium crown glass and heavy crown glass, as shown in Figure 1. This was confirmed.

Comparative Examples 1 and 2 The compositions, nd, vd, deformation points, Da, and DW of SK5 and 5SK5, which are conventional heavy crown glasses, are shown in Comparative Examples 1 and 2 in Table 1, respectively.

As is clear from Table 1, nd and νd of SK5 are the same as those of Example 1, but the yield point is 100°C higher than that of Example 1.
Even more expensive. Furthermore, although nd and vd of 5SK5 are the same as those of Example 2, the yield point is nearly 100° C. higher than that of Example 2.

Furthermore, when the specific resistance of SK5 and 5SK5 was measured, it was confirmed that they had much higher electrical resistance values than the optical lenses obtained in Examples 1 and 2, as shown in FIG.

(Hereinafter, blank space) [Effects of the invention As explained above, the optical glass of the present invention has nd 1
．． It has an optical constant of 58 to 1.67 and a sid of 50 to 62, a low electrical resistance value suitable for direct current melting, a low yield point suitable for mold forming, and excellent chemical durability. are doing.

Therefore, by practicing the present invention, ndl, 58
It becomes possible to simplify the manufacturing process, reduce production costs, shorten delivery time, etc. of optical glass having optical constants of ~1.67 and Sid50-62.

[Brief explanation of the drawing]

FIG. 1 shows the optical glass of Example 1.2 and Comparative Example 1.
2 is a graph showing the relationship between specific resistance and temperature of optical glass No. 2.

Claims (1)

[Claims] (1) SiO_2+B_2O_3 36-62wt% (
However, SiO_2 23-62wt% B_2O_3 0-28wt%) Li_2O 0.5-7wt% BaO 12-52wt% Li_2O_3+Al_2O_3+ZrO_2+TiO
_2 1 to 18 wt% (However, La_2O_3 0.
5-11wt% Al_2O_3 0-7wt% ZrO_2 0-8wt% TiO_2 0-2wt%) Na_2O 0-5wt% K_2O 0-5wt% MgO 0-10wt% CaO 0-15wt% SrO 0-20wt% ZnO 0-1 4wt% It has a composition with a refractive index (nd) of 1.58 to 1.67.
An optical glass having an Abbe number (νd) of 50 to 62.