JPH10152341A - Optical glass for injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain optical glass for injection molding, not depositing metal Pb even on injection molding in a reducing atmosphere due to P2 O5 component and thereby especially not giving a large damage to a mold, although containing PbO component essential for lowering the melting point of the glass. SOLUTION: This optical glass for injection molding comprises concretely 32-55wt.% of P2 O5 , 4-65wt.% of PbO, 1-26wt.% of an alkali metal oxide comprising Li2 O, Na2 O and/or K2 O, 0-32wt.% of an alkaline earth metal oxide comprising MgO, CaO, SrO and/or BaO, and 0-11wt.% of other oxides comprising ZnO, B2 O3 , Al2 O3 , TiO2 and/or Nb2 O5 , and has a working point temperature of 550 deg.C. Thereby, the reduction of PbO can be inhibited due to the P2 O5 component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical glass for injection molding which is suitable for producing optical parts such as lenses by injection molding glass which has been heated and melted.

[0002]

2. Description of the Related Art As a precision optical component, for example, a method in which a lens is manufactured by polishing glass has been used for a long time, but the manufacturing efficiency is poor and it is difficult to manufacture an aspherical lens. There is. For this reason, in recent years, a glass preformed into a predetermined shape is mounted in a molding die, and the preform is heated and softened, and pressed to transfer the shape of the die. The press forming method described above is used. Also, an injection molding method has been developed in which the viscosity is reduced until it becomes a fluid state by heating and melting the glass, and the molten glass is transferred to a mold shape by injecting the molten glass into a mold. I have.

[0003] Regardless of the press molding method or the injection molding method, the mold is heated together with the glass at the time of molding. When the mold is heated to a very high temperature,
There are problems such as oxidation of the mold material and peeling of the coating to promote the releasability, and the life of the mold is shortened.

Here, the characteristic points of glass include a transition point, a yield point, a softening point, and a working point. The relationship between these characteristic points and the viscosity is such that the viscosity at the transition point is about 10 ^12.
In poise, the viscosity at the yield point is about 10 ^10.5 poise,
The viscosity at the softening point is 10 ^7.6 poise and the viscosity at the working point is 10 ⁴ poise. And since press molding is performed in a state where the glass is softened, it is necessary to have a viscosity below the yield point.In injection molding, it is necessary to fluidize the glass. Must be lowered. Although the temperature at each of the above-mentioned characteristic points differs depending on the composition of the glass, when using the same material of glass, injection molding needs to have a lower viscosity than press molding. This would require heating the glass to a higher temperature.

[0005]

Here, as a glass material for forming a precision optical component, optical glass containing PbO has a transition temperature of 435 to 455 ° C. as compared with other glasses. In addition, the relatively low melting point and thus the relatively low melting point make it suitable for injection molding in terms of temperature. However, when PbO is melted, it is easily reduced, so that reduced metal Pb is precipitated, and this metal Pb reacts with the mold and its coating material to damage the mold. is there.

[0006] In view of the above points, the present inventor considered that PbO
As a result of intensive studies to suppress the reduction of PbO in the injection molding of glass containing P ₂ O ₅
The present inventors have found that when the components are added to a PbO-based glass, it is difficult to reduce PbO even when molding is performed in a reducing atmosphere as well as a neutral atmosphere, and have completed the present invention.

The object of the present invention is to:
An object of the present invention is to provide an optical glass for injection molding, which is a PbO-based glass exhibiting a low melting point, does not reduce PbO even in a neutral or reducing atmosphere, and does not easily react with a platinum-based coating material or the like. Is what you do.

[0008]

To SUMMARY OF THE INVENTION To achieve the above object, the present invention is characterized in that the P ₂ O ₅ component, and suppressed the reduction of PbO component, details, P ₂ O ₅ is 32-55 wt%, PbO is 4-65 _{wt%, Li 2 O, Na 2} O, alkali metal oxides consisting of K ₂ O is 1 to 26 wt%, MgO, CaO, SrO,
Alkaline earth metal oxides consisting of BaO is 0 to 32 _{wt%, ZnO, B 2 O 3} , Al 2 O 3, TiO 2, Nb 2
O Other oxide comprising ₅ comprises 0-11 wt%, respectively, is to its wherein the temperature indicating the working point is an injection molding optical glass 550 ° C. or less.

[0009]

Embodiments of the present invention will be described below. First, the optical glass in the present invention is for injection molding. Therefore, one method of performing injection molding will be described below with reference to FIG.

FIG. 1 shows an injection molding apparatus using an injection cartridge. In the figure, reference numeral 1 denotes a molding die, which has an upper die 2 and a lower die 3, and a cavity 4 is formed between the upper die 2 and the lower die 3.
A gate 5 is provided in the cavity 4, and a sprue 6 communicates with the gate 5, and the sprue 6 opens on the side surface of the mold 1. Then, the molding die 1 includes an upper die 2
The molten glass is poured in a state where the mold is clamped between the lower mold 3 and the lower mold 3.

Reference numeral 10 denotes an injection cartridge. The injection cartridge 10 has a cylinder chamber 11, an injection nozzle 12 is connected to a distal end of the cylinder chamber 11, and a cylinder chamber 11 is connected to a base end of the cylinder chamber 11. Is provided with a pressurizing chamber 13 in which fluid pressure acts. A piston 14 is provided in the cylinder chamber 11 so as to be slidable in the axial direction, and a rod glass 15 made of a glass material in a rod shape is detachably accommodated. A heater 16 is attached to a portion from the injection nozzle 12 to the tip of the cylinder chamber 11, and the tip of the rod glass 15 is heated by the heater 16 to be in a molten state. Then, when pressure is applied to the pressurizing chamber 13 to push the rod glass 15 through the piston 14, the molten glass in the injection nozzle 12 is supplied to the molding die 1 at a predetermined pressure.

When the glass reaches the entire inside of the cavity 4 of the molding die 1, the whole of the molding die 1 is cooled, so that the glass is solidified in a state where the shape of the cavity 4 is transferred. Therefore, after the mold 1 is disassembled and the glass molded product is taken out, the portion corresponding to the sprue 6 is cut and removed, whereby an optical component having a required shape is formed.

As described above, in order to manufacture a precision optical component such as a lens by injection molding, an injection cartridge 10 is required.
However, as a characteristic that the rod glass 15 mounted on the injection cartridge 10 must have, it must first be able to perform injection molding at a low temperature. Generally, if the molding temperature exceeds 650 ° C., the life of the mold becomes extremely short. Therefore, it is necessary to use glass having a molding temperature of at least 650 ° C., preferably at least 550 ° C. Further, a coating material is laminated on the surface of the mold 1 on which the cavity 4 is formed, and it is necessary to prevent components of glass from reacting with the coating material and the mold 1 itself.

[0014] Optical glass containing the commercial PbO, generally a glass of SiO ₂ -PbO system in which the SiO ₂ to the base, has a relatively low transition temperatures, but the working temperature is 6
Glass below 50 ° C. is not known. Furthermore, when these glasses are heated to the forming temperature, that is, the working temperature in a neutral or weakly reducing atmosphere as described above, metal Pb is precipitated by reduction. In order to suppress the precipitation of the metal Pb, a P ₂ O ₅ component is added. As a result, the metal Pb hardly precipitates. As a coating material for improving the releasability of the transfer surface in the mold, a platinum-based material is generally used. However, precipitation of metal Pb due to reduction of PbO, which is usually generated during injection molding, is caused by P ₂ O ₅ component. As a result, the coating material is not damaged. Further, the P ₂ O ₅ component is more preferable because it has a lower melting point than the SiO ₂ component. Glass having a working temperature of 650 ° C. or lower, preferably 550 ° C. or lower can be easily obtained.

[0015] Here, the specific composition of the optical glass of the present invention, respectively by weight%, P ₂ O ₅ is thirty-two to fifty-five%, P
bO is _{4~65%, Li 2 O, Na} 2 O, alkali metal oxides consisting of K ₂ O, etc. is 1~26%, MgO, Ca
O, SrO, alkaline-earth metal oxide 0-32% consisting of BaO, _{etc., ZnO, B 2 O 3,} Al 2 O 3, TiO
_2, Nb and other oxides composed of ₂ O ₅ is comprises 0 to 11%. The glass having this composition has a temperature of 550 ° C. or less in the state of a viscosity of 10 ⁴ poise, which is the working point.

When P ₂ O ₅ contains at least 32% by weight, the reduction of PbO can be effectively suppressed. However, P ₂ O
_{If 5} is 32% by weight or less, the glass tends to have a strong devitrification tendency, which is not preferable. Further, when the content of PbO is 65% by weight or more and the content of the alkali metal oxide is 1% by weight or less, the glass tends to have a strong devitrification tendency. And P ₂ O ₅ is 5
When the content is 5% by weight or more, the content of PbO is 4% by weight or less, and the content of the alkali metal oxide is 1% by weight or less, a desired low melting point cannot be obtained. Alkaline earth oxides and other oxides are not necessarily essential components, but can be added to improve devitrification resistance and chemical durability, adjust optical constants, surface tension, and the like. However, if added excessively, the melting property may be deteriorated and the cost may be increased. Therefore, it is preferable to limit the content of these alkaline earth oxides and other oxides to 32% by weight or less and 11% by weight or less, respectively.

[0017]

EXAMPLE Raw materials of an aqueous solution of orthophosphoric acid, lithium carbonate, sodium carbonate, lead oxide, barium carbonate, zinc oxide, aluminum hydroxide, niobium oxide and boric acid were prepared as No. 1 in Table 1 below. 2
A raw material batch corresponding to 2.5 kg in glass amount is prepared so as to have the composition shown in the above, and after mixing this raw material batch, it is put into a 1-liter platinum crucible,
It was melted at 000 ° C. and poured out of a platinum pipe connected to the bottom of the crucible into a preheated mold to form a plate-like glass block. After slow cooling, cut out the timber from the block and perform centerless processing by the usual method.
A rod-shaped glass having a diameter of 12 mm and a length of 120 mm was obtained. This rod-shaped glass is mounted in the cylinder chamber 11 of the injection cartridge 10 in the injection molding apparatus shown in FIG. 1, and the temperature of the glass at the injection nozzle 12 is set to 515 ° C.
When injection molding was performed while the mold 1 was heated to the same temperature, a biconvex lens having the characteristics shown in Table 1 and having a diameter of 12 mm was formed. Table 1
The measurement of the optical properties of the sample was performed using a spectrometer.
It was obtained by interpolation using the her formula.

Using the same raw materials, the composition of the glass was Glass amount to be 3

A raw material batch corresponding to 2.5 kg was prepared. When a plano-convex lens having a diameter of 10 mm was injection molded by the same procedure as described above, a lens product having initial performance was formed. The optical properties of this lens are
The measurement was performed in the same manner as described above.

In any case, no precipitation of the lead compound was observed in the platinum-based coating material laminated on the transfer surface of the molding die 1 after molding.

[0021]

[Table 1]

[0022]

As described above, the optical glass of the present invention has a low melting point and a P which is essential for lowering the melting point.
Despite having the bO component, even when injection molding is performed in a reducing atmosphere, no precipitation of metal Pb is observed, so that no significant damage is given to the mold, and the life of the mold is extended. Has the effect of

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view showing an example of an injection molding apparatus for injection molding an optical component such as a lens using the rod-shaped optical glass of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 2 Upper mold 3 Lower mold 4 Cavity 10 Injection cartridge 11 Cylinder chamber 12 Injection nozzle 13 Pressurization chamber 15 Rod glass 16 Heater

Claims (2)

[Claims] 1. An optical glass for injection molding wherein the reduction of a PbO component is suppressed by a P ₂ O ₅ component. Wherein P ₂ O ₅ is 32-55 wt%, PbO is 4-65 _{wt%, Li 2 O, Na 2} O, alkali metal oxides consisting of K ₂ O is 1 to 26 wt%, MgO, Ca
O, SrO, alkaline-earth metal oxide is 0-32 wt% consisting of _{BaO, ZnO, B 2 O 3} , Al 2 O 3, Ti
O _2, Nb ₂ O other oxide comprising ₅ comprises 0-11 wt%, respectively, for injection molding optical glass of claim 1, wherein a temperature showing a working point of 550 ° C. or less.