JPS5899125A - Rough melting method for optical glass - Google Patents

Abstract

PURPOSE:To prevent the deterioration of glass due to the penetration of platinum by melting starting materials for optical glass with a high PbO content with a roughly melting apparatus having a double structure composed of a refractory crucible and a platinum crucible so as to prevent the deterioration of the platinum crucible. CONSTITUTION:A roughly melting apparatus having a double structure composed of a refractory crucible 5 made of quartz or aluminous refractory and a platinum crucible 7 is put in an electric furnace 1 provided internally with a resistance heating element 2, and starting materials 9 for dense flint glass with a high PbO content or optical B2O3-PbO glass with a high PbO content are charged into the crucible 5. The materials 9 are roughly melted by heating to 1,000- 1,400 deg.C and poured into the outer crucible 7 from the bottom outlet 15 of the crucible 5. The roughly melted glass 10 stored once in the crucible 7 is poured into a water tank from the bottom nozzle 8 of the crucible 7. The erosion of the platinum crucible due to PbO is prevented, and homogenous optical glass contg. no unmelted starting material and undergoing no deterioration due to platinum is obtd.

Description

[Detailed description of the invention] The present invention relates to a coarse dynamic solution method for optical glass raw materials.

The present invention relates to a coarse dynamic solution method for optical glass using a double crucible.

Optical glass is generally produced by using the clay crucible method as raw material for optical glass.
It is manufactured by melting by the platinum crucible method or continuous melting method, but the time required for the optical glass raw material to complete vitrification in the melting process is 60 to 50 minutes of the total melting process.
There was a drawback that it occupied %. Alternatively, if an optical glass raw material containing a relatively large amount of PbO is directly supplied to a platinum crucible and melted.

Alloying of lead and platinum may occur, causing deterioration of the platinum crucible, or melting of platinum into the molten glass, resulting in yellowing or loss.
This is remelted in a platinum crucible to produce optical glass.

By doing this, the time required to complete the vitrification of (11 raw materials) is shortened (10 to 2.0 times the total melting process).
%), improving the efficiency of equipment, 121Pb.

Even when glass raw materials containing relatively large amounts of Effects such as preventing the occurrence of devitrification and devitrification can be obtained.

A method for roughly melting the glass raw material is a platinum crucible or a quartz crucible (a method in which the glass raw material is supplied, heated, coarsely melted, and allowed to flow down from a nozzle or hole provided in the crucible, or from one end of a cylindrical body of platinum or quartz). A method of supplying a glass raw material, heating it, roughly melting it, and flowing it down from the other end (Japanese Patent Application Laid-open No. 51
-67310) etc. have been proposed.

However, in the above method, for example, heavy flint glass with a PbO content of 50% or more or B2O3-
When producing PbO-based special glass, if the glass material is crudely melted in a platinum crucible or a cylindrical body with platinum on the inner surface, the aforementioned deterioration of platinum, yellowing and devitrification of the glass will occur. There are drawbacks that arise. In addition, in the method of supplying glass raw material to a quartz crucible, roughly melting it, and letting it flow down through a hole at the bottom of the crucible, the flow hole becomes larger due to erosion.
This will increase the amount of molten glass flowing down. If the flow rate increases, the raw material glass cannot remain in the coarse melting region for a sufficient period of time. Therefore, for example, when producing heavy flint glass with a PbO content of 50% or more or B203-PbO type special glass, Since there are considerable differences in the meltability of each component or material of the glass raw material, Pt)O, B, 03 which is easy to melt.
．． Alkaline oxides etc. are preferentially melted and 5t is difficult to melt.
02* Unmelted components such as uzoa mix into the crude molten glass. When optical glass is manufactured by melting crude molten glass containing such unmelted raw material components as a raw material, the refractive index fluctuations due to unmelted components and uneven distribution of components are extremely large, making it unsuitable for practical use. Furthermore, even with a system in which glass raw materials are supplied from one end of the cylindrical body and crude molten glass is allowed to flow down from the other end, it is difficult to prevent the contamination of unmelted materials as described above.

An object of the present invention is to provide a method for crudely melting optical glass raw materials without the above-mentioned drawbacks.

Particularly, one object of the present invention is to provide a method for homogeneously and coarsely melting glass raw materials without the above-mentioned drawbacks when manufacturing heavy 7 lint glass with a high PbO content or B203-PbO-based special glass. .

The present inventors removed the above-mentioned drawbacks, and as a result of various studies on the crude melting method of glass raw materials Q) to obtain a homogeneous optical glass, we found that a platinum crucible with a nozzle for flowing the crude molten glass @VC. A crucible made of quartz, alumina refractory, or zirconia refractory and having an outflow hole for crude molten glass is arranged, an optical glass raw material is supplied to the inner crucible, heated and melted, and the crude molten glass is passed through the outflow port. It was discovered that the distribution purpose could be achieved by supplying the material to the outer platinum crucible and then letting it flow down from the nozzle of the platinum crucible.

Hereinafter, practical examples of the present invention will be explained with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing an example of a crude melting apparatus for carrying out the method of the present invention. In the figure, an electric furnace 1 is heated by a heating element 2VC, such as a silicon carbide heating element, the temperature inside the electric furnace is detected by a thermocouple 3, and a desired crude melting temperature 5, for example, is determined by a temperature control device (not shown). 1,0OOC~1
．． Controlled to 40DC. The optical glass raw material is continuously or intermittently supplied to the inner refractory crucible 5 by the raw material supply device 4 through the supply port 16 (the lid 14 is opened during supply). The crucible 5 is made of, for example, quartz, alumina refractory, zirconia refractory, or the like. The supplied optical glass raw material 9 is crudely melted in the crucible 5, and the crude molten glass enters the platinum crucible 7 placed outside 11 of the crucible 5 through an outflow hole 15 provided at the bottom of the crucible 5, and flows into the -tanko. The crude molten glass 10 held in place flows down from a nozzle 8 provided at the bottom of the platinum crucible 7. The crude molten glass 11 that has flowed down is, for example, rapidly cooled in a water tank, crushed and then dried to obtain homogeneous fine granular glass containing no unmelted raw material components, which is then remelted in a platinum crucible. Can be superior to homogeneous optical glass. As shown in the figure, the platinum bolt and bore are supported by a refractory support 6vc, and the support 6 is installed on the bottom of the furnace by a refractory 12.

Next, an actual winding example will be described in which a glass raw material is roughly melted when producing a heavy flint glass having a PbO content of 50 or more by the method of the present invention.

Using the double crucible type crude melting device as described above, the weight '-
+ y) Te5t02'17%, A-e203
2%.

Pb064%, Nano 1%, 203%, Ti
O23%.

1 optical glass raw material having a composition of 0.3% As203
Quartz crucible 5 with a capacity of 1120A at a rate of 0 to 25r-sweat sowing
The material is roughly melted at a furnace temperature of i, o o o ~ 1,300 t:', and then passed through nozzles 8 to 10 of the outer platinum crucible 7.
It was possible to obtain homogeneous crude molten glass with a flow rate of 25" sea. In this case, random K I KF samples were taken 10 times from the 1,000 Kp crude molten glass and the refractive index was measured. The standard deviation is 100X10-5,
It was less than 1/1o of the conventional method. When crudely melting glass raw materials, it is desirable to increase the amount of molten glass flowing down as much as possible without mixing unmelted materials, but in the present invention, as described above, 10 to 25 Ky, z
Even at a considerably large flow rate of , it was possible to outperform homogeneous crude molten glass without contamination with unmelted materials.

As mentioned above, the multi-layered crucible uses a crude melting device with a dual structure of a refractory crucible and a platinum crucible, supplies glass raw materials to the inner refractory crucible and melts it, and transfers it to the platinum crucible on the outside. The Pb
Heavy flint glass or 8203-P with an O content of 50% or more
Even when producing bO-based special glass, it prevents deterioration of the platinum crucible, yellowing and devitrification due to platinum contamination, and contamination of unmelted components caused by increased flow rate due to erosion of the refractory crucible diversion holes. , homogeneous crude molten glass can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing one embodiment of an apparatus used to carry out the crude melting method of the present invention. 1... Electric furnace 2... Electric heating element 5... Refractory crucible 7... Platinum crucible (6 people) 1981 Patent Application No. 1955744. Name of the i20 invention: Rough melting method for optical glass 3, Person making the amendment Relationship to the case: Name of the patent applicant (520) Fuji Photo Film Co., Ltd. Kasumigaseki Building Post Office Post Office Box No. 49 Separate Haruka No. 1 figure

Claims (1)

[Claims] (1) In a double crucible rough melting device consisting of a platinum crucible with a nozzle and a refractory crucible with an outflow hole placed in the crucible 1111, an optical glass raw material is supplied to the inner crucible and heated and melted. A method for coarsely dissolving optical glass raw materials, characterized in that the glass is introduced into a platinum crucible on the outer side through an outflow hole, and is caused to flow down from a nozzle of the platinum crucible. (21) The refractory crucible is made of quartz, alumina 'H refractory, or zirconia refractory.
The coarse motion solution method described in Section 1. (31) The coarse dynamic solution method according to claim (1), wherein the optical glass raw material is a heavy flint glass having a PbO content of 50% or more or a raw material for B204-PbO-based special glass.