JP2001089183A - Optical glass for press formed lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain optical glass for lens, capable of stably carrying out press forming at a relatively low temperature and a low cost, reducing damage of a forming mold and prolonging life of the mold. SOLUTION: This optical glass has the following component composition: SiO2: 21-37 wt.%, B2O3: 22-40 wt.%, Al2O3: 10-30 wt.% and SiO2+B2O3+Al2O3 is 64-83 wt.%; Na2O is 3-15 wt.%, K2O is 0-15 wt.% and Li2O+Na2O+K2O is 14-26 wt.%; TiO2+ZrO2+Nb2O5+WO3 is 0-14 wt.%; BaO+SrO+CaO+MgO+ ZnO is 0-14 wt.%. The optical glass has <=510 deg.C sag temperature (Ts), 1.51-1.58 refractive index (nd) and 50-63 Abbe's number (νd).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low melting point optical glass which can be pressed at a relatively low temperature.

[0002]

2. Description of the Related Art In recent years, lens manufacturing methods by precision press molding that do not require polishing have been widely performed. At that time, in order to reduce damage to the mold, it is necessary to use a low-melting glass that can be press-molded at a temperature as low as possible.

[0003] As precision optical components such as lenses, those having a refractive index (nd) of 1.51 to 1.57 and an Abbe number (νd) of around 50 to 63 are preferably used as optical constants. However, optical glass having such an optical constant has been conventionally produced. However, since the glass composition has a high SiO ₂ content and a high viscosity, the pressing temperature is usually too high. Further, those containing PbO to lower the melting point are also known. This gives a low melting glass with a relatively low melting point,
When press-molding it, Pb precipitates on the surface and reacts with the mold, so that the molding surface of the mold is roughened. It is not always suitable as a glass material for molding.

In order to solve the above-mentioned problems, Japanese Patent Application Laid-Open No. Hei 5-193977 discloses that S
iO is 39~65%, B ₂ O ₃ is 10~38%, Li ₂
O is 3 to 12%, Na ₂ O is 0 to 7%, K ₂ O is 0
6.5%, and the total amount of Li ₂ O, Na ₂ O, and K ₂ O is 9 to 18%, Al ₂ O ₃ is 5 to 15%, M
gO is 0-6%, CaO is 0-6%, BaO is 0-6%.
Having a yield temperature of 560 ° C. or less, a refractive index (nd) of 1.51 to 1.54, and an optical constant of an Abbe number (νd) of 62 to 65.5. Material is disclosed.

[0005]

The glass composition of the prior art described above specifically has a yield temperature of 514 to 55.
9 [deg.] C., and in fact, it is 30 to
Molding is performed at a temperature as high as about 50 ° C. By the way, in order to protect the molding die and extend its life, the molding temperature must be suppressed as low as possible. In the case of a general molding die, the temperature of use is substantially at a temperature of 600 ° C. or more, and the possibility of damage to the molding die increases as the temperature approaches the usage limit temperature. Therefore, if the temperature at the time of press molding can be made slightly lower than this service limit temperature, a significant difference appears in the life of the molding die.

In view of the above, the present inventor has conducted intensive studies to obtain a glass composition for press molding having an optical constant required as a precision optical component such as a lens and having a lower melting point. result, SiO ₂ content is a component to increase the viscosity in a relatively small area, in the predetermined range B ₂ O _3, Al ₂
The present inventors have found that the intended purpose is achieved by combining O ₃ and an alkali metal oxide, and have completed the present invention. Accordingly, an object of the present invention is to provide an optical glass for press molding that has a yielding temperature of 500 ° C. or less and can be press-molded at a lower temperature.

[0007]

In order to achieve the above-mentioned object, the composition of the optical glass for press molding according to the present invention is as follows: 21 to 37% by weight of SiO _{2 and} 22 to 40% of B ₂ O ₃ by weight. %, Al ₂ O ₃ is 10 to 30%, and SiO ₂ + B ₂ O ₃ + Al ₂ O ₃ is 64 to 83%, Na
₂ O is 3 to 15%, K ₂ O is 0 to 15%, and L
14 to 26% of i ₂ O + Na ₂ O + K ₂ O, and further Ti
O ₂ + ZrO ₂ + Nb ₂ O ₅ + WO ₃ is 0 to 14%, B
aO + SrO + CaO + MgO + ZnO is 0 to 14%, the sag temperature (Ts) is 500 ° C. or less, and the refractive index (n
d) is 1.51 to 1.58, Abbe number (νd) is 50 to
63.

The reasons for limiting the range of each component as follows are as follows.

First, SiO ₂ , B ₂ O ₃ and Al ₂ O ₃ are essential components. If the content is less than 64%, the refractive index becomes too high, and if it exceeds 83%, the yield temperature becomes too high. Of these, the range of the amount of SiO ₂ is particularly important in the present invention, and keeping it at 37% or less is particularly effective for obtaining a yield temperature of 500 ° C. or less. However, 21%
If it is less than 10, the chemical durability deteriorates. If the content of B ₂ O ₃ exceeds 40%, the chemical durability deteriorates, and if it is less than 22%, the yield temperature becomes too high and the meltability deteriorates. Al ₂ O ₃
Is 10% to suppress the phase separation tendency and improve the chemical durability.
% Or more, particularly effective when the B ₂ O ₃ content is high, but if it exceeds 30%, the yield temperature is too high.

The content of the alkali metal oxide is required to be 14% or more for lowering the melting point, improving the devitrification resistance, and improving the melting point, but if it exceeds 26%, the chemical durability is excessively deteriorated.
Of alkali metal oxides, Li ₂ having a high melting effect
O and Na ₂ O are essential components of the present invention. 1% each
And 3% or more, but if it exceeds 10% and 15%, respectively, the chemical durability deteriorates. K ₂ O is an optional component and can be used for improving the melting property, adjusting the refractive index, and the like. However, if it exceeds 15%, the chemical durability deteriorates.

TiO ₂ , ZrO ₂ , Nb ₂ O ₅ , WO ₃
Is an optional compounding component and is mainly used for adjusting optical constants. However, if the content exceeds 14%, the tendency of phase separation increases and the yield temperature becomes too high.

BaO, SrO, CaO, MgO, ZnO
Is also an optional component, and is mainly used for adjusting optical constants. However, if the content exceeds 14%, the yield temperature becomes too high. In addition to the above components, La ₂ O ₃ , Ta ₂ O _5, etc. may be contained for the purpose of adjusting the optical constant, improving the chemical durability, etc. within a range not departing from the object of the present invention. it can. Further, a small amount of Sb ₂ O ₃ , F, Cl is used as a defoaming material.
You can add something like that.

[0013] The optical glass of the present invention comprises an oxide, a hydroxide,
Using a carbonate, a nitrate, etc., weigh them so as to have a predetermined composition, mix them, and use a platinum crucible in an electric furnace.
It can be manufactured by melting at 150 to 1300 ° C., casting into a preheated mold, and gradually cooling.

[0014]

Next, an embodiment of the present invention will be described. In the table below, the component compositions of the glasses used in Examples 1 to 8 are shown in% by weight, and the optical constants and the deformation temperatures of the glass in each Example are also shown. In the table, the refractive index (nd) and Abbe number (νd) indicate the cooling temperature −10 ° C./ho.
This is a value measured by gradually cooling with ur. The yield temperature (Ts) is a value measured at a rate of 5 ° C./min using a thermal dilatometer. Each had a sagging temperature of 500 ° C. or less.

Next, according to the above procedure from these compositions,
A glass block was prepared, and a polishing ball having a predetermined weight was produced through processing steps of cutting, grinding, and polishing. Next, when press molding was performed using them, press molding was possible at 540 to 570 ° C.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

According to the present invention, press molding can be performed at a relatively low temperature, damage to a molding die can be reduced, and its life can be extended, and stable press molding of optical glass and low cost can be achieved. This has the effect of achieving realization.

Continued on the front page F term (reference) 4G062 AA04 BB05 DA04 DA05 DB04 DC04 DC05 DD01 DE01 DE02 DE03 DE04 DF01 EA01 EA02 EA03 EA04 EB03 EB04 EC01 EC02 EC03 EC04 ED01 ED02 ED03 ED04 EE01 EE02 EE03 EF03 EF04 EF04 FA10 FB01 FB02 FB03 FB04 FC01 FC02 FC03 FC04 FD01 FE01 FF01 FG01 FG02 FG03 FG04 FH01 FJ01 FK01 FL01 GA01 GA10 GB01 GC01 GD01 GE01 HH01 HH03 HH05 HH07 HH08 NN07HH KK NN32

Claims (1)

[Claims] 1. The method of claim 1 wherein the weight percent of SiO_Two Is 21-37
%, B_Two O_Three Is 22-40%, Al _Two O_Three Is 10-30
% And SiO_Two + B_Two O_Three + Al_Two O_Three Is 64
~ 83%, Na_Two O is 3 ~ 15%, K_Two O is 0 to 15%
And Li_Two O + Na _Two O + K_Two O is 14-26
%, Plus TiO_Two + ZrO_Two + Nb_Two O_Five + WO_ThreeBut
0-14%, BaO + SrO + CaO + MgO + ZnO
Has a composition of 0 to 14% and a yield temperature (Ts) of 500
° C or lower, refractive index (nd) of 1.51 to 1.58, Abbe
Glass for press-molded lenses having a number (νd) of 50 to 63
Su.