JP2001031443A - B2O3-La2O3-RO GLASS FOR MOLDED LENS (BORIA-LANTHANA-RO) - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower the glass transition point and the liquid phase temperature by admixing multi-components of divalent metal oxides to the minimum concentration of B2O3 for vitrification. SOLUTION: In an embodiment, this glass comprises 30-35 wt.% of B2O3, 15-25 wt.% of La2O3, and 45-50 wt.% of RO. In a preferred embodiment, a part of La2O3 may be replaced with 0-5 wt.% of ZrO2, 0-5 wt.% of TiO2, and 0-10 wt.% of Nb2O5 and/or a part of B2O3 may be replaced with 0-2 wt.% of SiO2. Further, RO is constituted with two or more kinds of ZnO, Bad, CaO and their suitable amounts are individually 15-30 wt.%, 5-40 wt.% and 5-10 wt.%. The glass transition point and the liquid phase temperature are lowered to stabilize the glass and raises the refractive index. Thus, the mold release agent that is coated on the surface of the mold for releasing the molded lens from the mold can be prevented from causing reaction or fusion or from deteriorating physically, the coat layer on the mold can prolong its life to reduce the production cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polishing molded lens B ₂ O ₃ can be formed by press molding without -La
_{The present} invention relates to a ₂ O ₃ -RO glass.

[0002]

2. Description of the Related Art Around 1883, a technique has been developed for producing a molded lens having the same surface shape and surface roughness as a polished surface by pressing instead of polishing. As one of the elemental technologies for producing the molded lens, there is a development of a glass having a low glass transition point (hereinafter, abbreviated as “Tg”).

[0003] To make a molded lens, precision grinding and
Using a polished mold, the glass is bent at a yield point (hereinafter referred to as “T
s ") for about 20 seconds. At this time, the temperature of the mold and the glass must be the same. By setting the same temperature, the mold shape can be transferred to the glass without causing sink marks (deformation) of the glass.

In order to release a mold lens from a mold, a mold release film such as DLC (diamond-like carbon) or TiCN is coated on the surface of the mold. However, there is a problem in that it reacts and fuses with glass or physically deteriorates. To avoid this, it is desirable not only to control in an N ₂ atmosphere, but also to press at as low a temperature as possible. Correspondingly, glass having a low Ts or Tg is required.

[0005] The composition of the conventional mold glass is determined from the viewpoint of the refractive index, Abbe number or chemical durability.
Lowering g was not considered. Rather, a low Tg has been avoided because it increases the thermal expansion coefficient and tends to deteriorate the chemical durability.

[0006]

As a glass for a molded lens, a glass having a low Tg is demanded in order to prolong the life of a mold coating film and reduce costs.

An object of the present invention is to solve the above conventional problems and to provide a glass having a low Tg and a high refractive index.

[0008]

In order to achieve the above-mentioned object, the present invention provides a divalent metal oxide RO which is multi-componented into a minimum concentration of B ₂ O ₃ which can be vitrified to obtain a glass transition point of glass. It lowers the liquidus temperature and stabilizes the glass.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION
In the B ₂ O ₃ -La ₂ O ₃ -RO system glass, the divalent metal oxide RO is made into a multi-component to the minimum concentration of B ₂ O ₃ that can be vitrified to lower the glass transition point and the liquidus temperature, It stabilizes glass and has the effect of increasing the refractive index.

[0010] The invention according to claim 2 is a method according to claim 1, wherein
₂ O ₃ : 30 to 35% by weight, La ₂ O ₃ : 15 to 25% by weight, RO: 45 to 50% by weight (R is a divalent metal oxide). It has the effect of lowering the phase temperature and increasing the refractive index.

The invention according to claim 3 is the invention according to claim 2.
a part of _{a 2 O 3, ZrO 2:} 0~5 wt%, TiO _2: 0
5 wt%, Nb ₂ O _5: 0~10 those that substitute a weight percent range, has the effect of glass to stabilize, and more reliably increase the refractive index.

The invention according to claim 4 is the same as the invention according to claim 2,
It substitutes a part of ₂ O ₃ in the range of SiO ₂ : 0 to 2% by weight, and has an effect of further stabilizing the glass.

The invention according to claim 5 is the same as the invention according to claim 2,
O is composed of at least two kinds of ZnO, BaO, and CaO, and the composition range thereof is 15 to 30% by weight, 5 to 40% by weight, and 5 to 10% by weight, respectively. It has the effect of lowering the liquidus temperature and stabilizing the glass.

Next, a B ₂ O ₃ -La ₂ O ₃ -RO glass for molding according to an embodiment of the present invention will be described.

In B ₂ O ₃ -La ₂ O ₃ -BaO glass, the minimum concentration of B ₂ O ₃ that can be vitrified was determined. 50 g of boric acid, lanthanum oxide and barium carbonate in terms of oxide
Weigh and mix, put into a platinum crucible, 13 in an electric furnace
Melted at 00 ° C. for 30 minutes. After melting, the glass melt was cast on a preheated mold, and then the glass was cooled in an annealing furnace to produce a glass block.

After the obtained glass was pulverized, Tg, Tc (crystallization temperature) and Lt (liquidus temperature) were determined by differential thermal analysis. Table 1 shows the composition of glass and Tg, T
The measurement results of c, Lt and refractive index are shown.

[0017]

[Table 1]

[0018] is (Table 1) results until LaF1~LaF16 were examined ternary glass _{B 2 O 3 -La 2 O 3} -BaO in.

FIG. 1 shows the vitrified region of the glass studied above. B ₂ O ₃ : 30% by weight is the lowest limit of the vitrification region. 2 and 3 show the relationship between the amount of La ₂ O ₃ and Tg, and the relationship between Tg and the refractive index in this composition system. 2 and 3, the Tg is reduced and the refractive index is increased by reducing the amount of B ₂ O ₃ . FIG.
From the results, it was found that T was almost the same when the B ₂ O ₃ amount was 30 wt% and 35 wt%.
Therefore, the amount of B ₂ O ₃ is desirably 35% by weight or less.

Further, when the amount of the glass-forming oxide decreases, the glass becomes unstable and tends to crystallize. To stabilize the glass, it is necessary to lower the liquidus temperature or increase the viscosity of the glass. Here, assuming that Tg is a glass transition point, Tc is a crystallization temperature, and Lt is a liquidus temperature as parameters for measuring the stability of the glass, the β value is β = (Tc−Tg) / (Lt−
Tc), and it is said that the glass is sufficiently stable if the β value is 2.4 or more.

In Table 1, LaF23 to LaF26 have B
_{An example in which 2} O ₃ is substituted with SiO ₂ in the range of 0 to 10% by weight will be described.

FIG. 4 shows the results of LaF23 to LaF26. FIG. 4 shows that when the SiO ₂ amount is in the range of 0 to 5% by weight, the stability is increased as compared with the case where the substitution amount is 0.

In addition, LaF27 to LaF2 in (Table 1)
8 shows an example in which was replaced with a range of La ₂ O ₃ in the ZrO ₂ 0% by weight. In addition, the LaF27 to LaF
The result of F28 is shown in FIG. FIG. 5 shows that the amount of ZrO ₂ is 0
In the range of 〜5% by weight, the stability is increased as compared with the case where the substitution amount is 0.

Similarly, LaF29-L in (Table 1)
the aF31 the La ₂ O ₃ in the range of 0 to 15 wt% Nb ₂ O _5, a La ₂ O ₃ to TiO ₂ in LaF32～LaF34 0
It shows an example of substitution in the range of 10 to 10% by weight. N
If b ₂ O ₅ is in the range of 0 to 10% by weight and TiO ₂ is in the range of 0 to 5% by weight, the stability is increased.

In order to increase the stability of the glass, SiO ₂ ,
When ZrO ₂ , Nb ₂ O ₅ , and TiO ₂ are contained, the stability of the glass tends to increase, but the stability does not increase until β> 2.4 is exceeded.

Further, LaF17 to LaF2 in (Table 1)
Fig. 4 shows an example in which BaO is replaced with ZnO. FIG. 6 shows the results of LaF17 to LaF24. As shown in FIG. 6, the liquidus temperature was 979.
(BaO: 50% by weight) to 803 ° C (BaO: Zn
O = 3: 2), and the β value also exceeds 2.4.
Particularly, in the range of BaO: ZnO = 4: 1 to 2: 3, the β value also increases.

Further, Ba is used as a divalent metal oxide.
Examples of adding CaO to O and ZnO are shown in FIG.
5 to LaF39. CaO: 9% by weight, and further addition lowers the liquidus temperature to 737 ° C., increasing the stability and increasing the refractive index.

From the above results, ZnO, BaO, CaO
Are in the ranges of 10 to 30% by weight, 9 to 40% by weight, and 0 to 10% by weight, respectively.

The optimum composition of the divalent metal oxide is Zn
O: BaO: CaO = 2: 2: 1 to 3: 1: 1. By thus making the RO component multi-component, a very stable glass can be produced.

[0030]

As described above, the present invention has the effect of preventing the reaction between glass and the mold coating film, achieving a long life of the mold, and reducing the cost of the mold lens. .

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a vitrified region of a B ₂ O ₃ —La ₂ O ₃ —RO glass for a molded lens according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining a change in Tg due to B ₂ O ₃ and La ₂ O ₃ .

FIG. 3 is a view for explaining changes in Tg and refractive index by B ₂ O ₃ .

FIG. 4 is a diagram illustrating a change in β value due to the substitution of B ₂ O ₃ and SiO ₂ .

FIG. 5 is a view for explaining a change in β value due to substitution of La ₂ O ₃ and ZrO ₂ .

FIG. 6 is a view for explaining changes in Tg, Lt, and β values due to the BaO—ZnO substitution.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Shigeo Furukawa 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Yoshinori Higashiyama 1006 Odaka Kadoma Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Tetsuro Izumiya 685-58 Fuku termo, Hokushi, Tokyo 4G062 AA04 BB05 BB08 DA02 DA03 DB01 DC05 DD01 DE04 DF01 EA01 EB01 EC01 ED01 EE03 EF01 EG03 EG04 EG05 FA01 FB01 FB02 FC03 FC01 FC01 FF01 FG01 FG02 FG03 FH01 FJ01 FK04 FL01 GA01 GA10 GB01 GC01 GD01 GE01 HH01 HH03 HH05 HH07 HH09 HH11 HH13 HH15 HH17 HH20 JJ01 JJ03 JJ05 JJ07 JJ10 KK01 KK03 KK05 NN07 NN02

Claims (5)

[Claims] In a B ₂ O ₃ —La ₂ O ₃ —RO system glass, a divalent metal oxide RO is made into a multi-component to a minimum viscous concentration of B ₂ O ₃ to obtain a glass transition point of the glass; A B ₂ O ₃ -La ₂ O ₃ -RO glass for mold lenses in which the liquidus temperature is lowered and the glass is stabilized. 2. B ₂ O ₃ : 30 to 35% by weight, La ₂ O ₃ :
15-25 wt%, RO: 45 to 50 wt% (R is a divalent metal oxide) and a molded lens according to claim 1, wherein comprised of _{B 2 O 3 -La 2 O 3} -RO based glass. _3. A part of La ₂ O ₃ is substituted within a range of ZrO ₂ : 0 to 5% by weight, TiO ₂ : 0 to 5% by weight, and Nb ₂ O ₅ : 0 to 10% by weight. mold lens according _{B 2 O 3 -La 2 O 3} -RO based glass. 4. The molded lens B according to claim 2, wherein a part of B ₂ O ₃ is substituted in the range of SiO ₂ : 0 to 2% by weight.
₂ O ₃ -La ₂ O ₃ -RO based glass. 5. The method according to claim 2, wherein the RO comprises at least two kinds of ZnO, BaO, and CaO, and their composition ranges are 15 to 30% by weight, 5 to 40% by weight, and 5 to 10% by weight, respectively. B ₂ O ₃ -La ₂ O ₃ for molded lenses
-RO glass.