JP3140259B2 - Method for producing optical glass lump and method for producing optical glass molded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to a manufacturing method and its use in high-precision optical glass gob such as a lens prism.

[0002]

2. Description of the Related Art In recent years, miniaturization and asphericalization of optical molded products have been demanded in response to miniaturization and weight reduction of optical crosspieces.

Conventional spherical lenses have been manufactured by grinding and polishing. However, micro lenses or aspherical lenses are manufactured by the so-called glass molding method because it is difficult to process and mass-produce by the grinding and polishing method. .

[0004] The glass molding method is a process of intermittently cutting molten glass leaking from an orifice of a glass melting furnace, cooling and solidifying the glass, and then grinding and polishing.
Next, a preforming step of press-molding with a preforming mold,
Further, it comprises a precision molding step of press-molding to a desired final shape by a precision molding die.

However, in the above method, the glass once cooled and solidified is heated and melted again at the time of preforming, so that the number of steps is increased and it is difficult to reduce the cost.
There are problems such as being unfavorable from the viewpoint of energy saving.

In view of the above, a method has been proposed in which precision molding is carried out directly from a glass in a molten state through preforming without providing a reheating step (hereinafter, this method is referred to as a direct glass molding method). I have. However, in the direct glass molding method, if the temperature of the receiving mold for receiving the high-temperature molten glass leaking from the orifice of the glass melting furnace or the temperature of the pre-forming mold for pre-forming the high-temperature glass is too high, the mold and the glass are not heated. However, there is a problem that the mold cannot be used for a long time because of severe deterioration of the mold.On the other hand, if the temperature of the mold is too low, surface defects such as wrinkles and sink marks will occur in the glass and precision lenses Cannot be constructed.

[0007] Japanese Patent Application Laid-Open No. 4-37614 discloses 200-
550 ° C., disclosed in Japanese Patent Application Laid-Open No.
After receiving the molten glass with a 50 ° C jig, re-heat it to a temperature above the glass softening point before molding, so that “wrinkles” and “hike”
There is disclosed a method for removing shrinkage marks such as the above and surface defects such as vacuum bubbles.

[0008]

However, in the methods described in the above publications, it is necessary to reheat the glass once received by the low-temperature jig to a temperature higher than the softening point, and the deterioration of the jig caused by the heating. In addition, it has been difficult to improve the yield of products due to problems such as fusion between the jig and the glass during reheating.

In view of the above-mentioned problems of the prior art, the present invention solves the problems of mold deterioration, glass surface defects, and the like in a direct glass molding method in which it is not necessary to reheat the glass, thereby improving the yield. An object of the present invention is to provide a method for manufacturing a molded article .

[0010]

SUMMARY OF THE INVENTION The present invention, which achieves the above object, comprises at least a step of receiving a molten glass lump that drops from an orifice and press-molding a glass lump in a high-temperature softened state into a predetermined shape. Optical glass block consisting of
In the method of manufacturing, the between the two steps, while from the transport path surface of the porous member having a glass gob transport path that can be a glass gob travels by ejecting a gas to float the glass gob, for driving the transport look including the step of performing transport is moved along the conveying path while horizontally rotating the glass gob has emerged in the conveying path by means, and porous in said step
Temperature of the gas ejected from the pores of
This is a method for producing an optical glass lump, which is characterized in that defects on the glass surface are eliminated by forming the glass block .

Further, the present invention includes performing the transporting step in the atmosphere.

Further, the present invention includes that the conveyance drive output means is based on wind power.

Further, the present invention includes heating the porous member.

The present invention also includes heating the glass from above the porous member to remove surface defects on the upper surface of the glass.

Further, the present invention includes changing the temperature of the gas ejected from the porous member depending on the location of the porous member.

The present invention also provides a step of preforming glass in a softened state by press molding in a non-oxidizing atmosphere.
It includes a step of precision molding the preformed glass by press molding in a non-oxidizing atmosphere.

[0017]

It is difficult to hold or transport hot glass without causing defects such as wrinkles on the surface. This is because such wrinkles are mainly caused by a temperature difference between the jig that receives or transports the high-temperature glass and the glass, and such a jig includes a heat-resistant metal or Ceramics and the like are generally used, but the higher the temperature, the more easily these jigs react with the glass.

In the present invention, the jig and the glass are conveyed while the high-temperature glass, which is melted and dropped from the orifice, is floated and conveyed by the gas ejected from the porous member until the temperature becomes suitable for press molding. It is intended to solve the problem of reaction and the problem of wrinkles on the glass surface.
Furthermore, by moving the glass while rotating it horizontally, a preform glass lump having a uniform cooling state, shape and the like is obtained.

Hereinafter, the present invention will be described in detail.

In the present invention, the glass in the molten state is
The glass having a viscosity of 10 ⁴ dPa · sec or less, and the glass in a softened state at a high temperature are those having a viscosity of 10 ¹⁰ dPa · sec or less.

The porous member can be appropriately selected from those having a hole density capable of ejecting a gas at a flow rate sufficient to float glass, heat resistance, and appropriate mechanical strength. For example, when an oxidizing gas such as air is used as a gas to be ejected, a heat-resistant oxide ceramic such as alumina or mullite is used. When an inert gas such as nitrogen is used, a heat-resistant oxide such as silicon nitride is used. What is necessary is just to select a crystalline nitride ceramic.

For the purpose of preventing gas leakage and efficiently adjusting the flow rate and temperature on the surface of the porous member excluding the gas introduction portion and the transport path, high-temperature spraying of ceramics, metal, etc., dipping, and wet coating are performed. A surface treatment such as a wet densification treatment may be performed.

The gas ejected from the porous member functions to float the glass and to heat and soften the lower surface of the glass to remove surface defects on the lower surface of the glass. As such a gas component, an inert gas such as N ₂ , He, or Ar, or air is preferable. The temperature of the gas to be ejected is preferably 300 to 1000 ° C. Further, by gradually lowering the temperature of the gas as the glass moves on the conveying path, surface defects such as wrinkles are generated on the glass surface. Without cooling to a temperature suitable for being subjected to press molding.

The flow rate of the gas to be jetted is 50
It is preferable to set it to 1000 cc / min / cm ² .

Further, by heating the porous member by a heating means such as a cartridge heater, it is possible to prevent the temperature of the jetted gas from lowering and to easily control the temperature of the gas.

Further, by heating the glass from above the porous member by a heating means such as a SiC ceramics heater or a nichrome heater, the upper surface of the glass is softened and surface defects on the upper surface of the glass block can be removed.

As the pushing means, any means can be used as long as it can advance the glass while horizontally rotating it along the conveying path of the porous member. FIG. 1 is a schematic plan view showing an example in which wind power is used as the pushing means. In this example, the glass 104 floating on the transport path 103 of the porous member 102 due to the hot air blown from the gas pipe 101 moves forward while rotating horizontally on the transport path 103. At this time, the gas pipe 101 is installed diagonally behind the glass 104 so that the glass 104 moves forward while rotating horizontally. Examples of other extrusion means include, for example,
Examples of such a method include mechanical force such as pushing with a tip of a carbon rod or the like.

Regarding the atmosphere in which the steps of the present invention are carried out, the step of performing press molding is preferably performed in a non-oxidizing atmosphere because of problems such as mold deterioration. Until the step of obtaining the preform glass lump, the glass and the mold do not come into contact with each other or require only an extremely short contact, so that it can be carried out almost without any trouble even in the air.

[0029]

EXAMPLES The present invention will be described more specifically with reference to the following examples.

As a receiving die for receiving a glass in a molten state that is melted and dropped from the orifice, a receiving die having a recess with a radius of curvature of 200 mm was manufactured using SUS303. Next, alumina is sprayed on the surface of the porous alumina material having an average pore diameter of about 5 μm and a porosity of about 30% to a thickness of about 100 μm to make the surface non-porous. Was ground to obtain a porous member. In addition, the glass conveyance path was a 90-cm-long recess. As a mold for preforming, the surface of a cemented carbide mainly composed of tungsten carbide WC was coated with titanium nitride (TiN). As a mold for precision molding, a titanium carbide was coated on a cemented carbide base material also containing WC as a main component, and a hard carbon film was further coated.

Using the jig processed as described above, a convex glass lens was manufactured in the following manner.

FIG. 2 is a process chart showing a series of manufacturing steps of a glass lens.

The glass material 201 has a glass transition point of 5
Using an optical glass SK12 of 10 ° C., a glass melting furnace 2
Then, the molten glass was melted at 1200.degree. C. by the use of an O.sub.2 and passed through a flow control tube 203 maintained at 1100.degree. C., and the molten glass was received from an orifice 204 into a receiving mold 205 maintained at 450.degree. The glass block 222 is transported by the transport jig (not shown) together with the receiving mold 205 to a position above the porous member 208, and the receiving die is tilted by the transport jig so that the lower surface of the receiving die becomes a surface on the porous member However, it was dropped on the porous member 208 so as to be on the lower surface.

FIG. 3 illustrates an example of a process for obtaining a glass block 222 by receiving a molten glass 201 falling from an orifice by a receiving mold 205.

Next, the hot air gas supply jig 20 is attached to the porous member.
Air was supplied from 7 and heated by a heater built in the porous member, and air at about 750 ° C. was jetted at a rate of 50 l / min from the surface of the conveying path of the porous member. Hot air at about 800 ° C. was blown onto the glass side surface at a rate of 5 l / min from the transport driving pipe 206 at a rate of 5 l / min for about 1 second, and the glass block 222 was rotated and advanced at a speed of about 5 cm / sec.

FIG. 4 shows a process in which the glass block 222 advances while horizontally rotating in the longitudinal direction of the glass transport path 224 by the gas 225 blown out from the hot air gas supply jig 207.

From a point at which the glass lump advances 20 cm, air of about 900 ° C. is supplied by another hot-air gas supply jig 209, and a heater 21 provided above the porous member is provided.
1 heated the top of the glass mass to about 850 ° C. The lower surface of the glass block was heated by air at 900 ° C. and the upper surface of the glass block was heated by a heater, so that surface defects on both surfaces were removed. The advance distance of the glass block during this time is 50 cm,
The forward speed was 2 cm / sec on average.

Next, air at about 400 ° C. is supplied by another hot air gas supply jig 210 to cool the glass block for about 20 seconds, and the glass block is cooled and cooled until the side and bottom surfaces thereof become 600 ° C. or lower. A molding glass block 223 was obtained. All the steps so far were performed in an air atmosphere.

The side surface of the obtained preform glass block 223 is sandwiched between ring-shaped transfer jigs 212 to form a gas replacement chamber 214.
Through the lower die 217 of the preforming die set in the molding chamber 215 in a non-oxidizing atmosphere, and lowers the upper die 216 to press the die under the conditions of a press pressure of 1 × 10 ⁶ Pa and 650 ° C.
Pressure molding was performed for 0 seconds. The preformed glass lens preform 226 is carried by the ring-shaped transfer jig 218 onto the lower mold 220 of the precision molding die, and the upper mold 219 is lowered to obtain a press pressure of 4 × 10 ⁶ Pa and 580 ° C. Pressure molding was performed for 1 minute under the conditions to obtain a convex glass lens 221.

The surface roughness and the surface accuracy of the obtained glass lens 221 were measured by using a surface roughness measuring device (M
AXIM-3D), Optical interferometer (MARC manufactured by Zygo)
As a result of the measurement in 3), the surface roughness of the press-formed surface was 2n.
m, the surface accuracy is one Newton ring or less,
It was confirmed that the glass lens had a good surface shape.

The present invention has been described with reference to the embodiments.
Atmosphere of each process, composition of gas passing through porous member,
It goes without saying that the material and shape of the jig in contact with the glass, the heating means, the type of glass, the shape of the optical molded product , and the like are not limited to the present embodiment.

[0042]

According to the present invention, it is not necessary to reheat the glass, so that the manufacturing process is simplified, the cost can be easily reduced, and the direct glass molding method, which is a preferable manufacturing method from the viewpoint of energy saving, can be used. It is possible to provide a manufacturing method capable of solving problems such as deterioration of glass and surface defects of glass such as wrinkles and sink marks and manufacturing a good optical glass lump with high yield.

Further, the glass floated on the glass transport path provided on the porous member is moved on the transport path while being horizontally rotated to obtain a glass preform having a uniform cooling state and shape. Resulting in good optics
A molded article can be obtained.

Further, by adjusting the temperature of the hot air gas that floats the glass, the glass can be cooled without causing any surface defects on the lower surface of the glass without providing a step of removing the surface defects. The molding step can be omitted or the molding time can be shortened.

[Brief description of the drawings]

FIG. 1 is a schematic plan view illustrating one embodiment of an extrusion unit.

FIG. 2 is a process chart showing a glass lens manufacturing process in an example.

FIG. 3 is a schematic view showing an example of a process in which glass melted and dropped from an orifice is received by a mold into a glass lump.

FIG. 4 is a schematic view showing an example of a process in which a glass lump moves while horizontally rotating on a glass transport path of a porous member.

[Explanation of symbols]

 Reference Signs List 101 gas pipe 102 porous member 103 glass transport path 104 glass 201 molten glass 202 glass melting furnace 203 flow control tube 204 orifice 206 transport drive pipe 207 hot air gas supply pipe 208 porous member 215 forming chamber 221 glass lens 223 preforming glass Lump 224 Glass transport path

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akazu Mizuwa 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-63-256543 (JP, A) JP-A Sho 63-162540 (JP, A) JP-A-61-132526 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C03B 7/14 C03B 11/00 C03B 35/00

Claims (10)

(57) [Claims] 1. An optical system comprising at least a step of receiving a molten glass lump that drops from an orifice and a step of press-molding a high-temperature softened glass lump into a predetermined shape.
In the method for producing a glass lump , the glass
The gas is ejected from the surface of the transport path of the porous member having the glass lump transport path through which the lump can move, and the glass lump floats on the transport path while being floated on the transport path by the transport driving means. Contact the step of performing transport is moved along the glass gob is in the conveyance path while being horizontally rotated to unrealized, and the step
The temperature of the gas ejected from the pores of the porous member
Therefore, a method for producing an optical glass lump, wherein the defect is eliminated by changing the glass surface . 2. A process according to claim 1, said transporting step performed in the atmosphere. 3. The manufacturing method according to claim 1, wherein the means for driving the transfer is based on wind power. 4. The manufacturing method according to claim 1, wherein the movement of the glass block is a horizontal rotation movement . 5. A method according to any one of claims 1 to 4 porous and upper heating the glass body from the member to remove the surface defects of the glass gob top. 6. A transport member forming a transport path has a long shape.
Shape, and the groove-shaped transfer part of this transfer member is
Producing how <br/> method of claim 1, wherein the moving mass. 7. A process for preforming by press molding in a hot softened condition nonoxidizing atmosphere glass mass, claim 1 comprising the step of precision molding by press molding a preformed glass gobs in a non-oxidizing atmosphere 6. The production method according to any one of items 1 to 5, 8. The temperature of a gas ejected from pores of a porous member.
The temperature range is from 300 to 1000 ° C.
The method according to claim 1, wherein 9. The method according to claim 1, wherein
Optical glass lump manufactured by the method for manufacturing light glass lump
Is pressed with a pair of molds to form an optical glass molded body.
A method for producing an optical glass molded body, characterized by being obtained. 10. An optical glass lump taken out of a conveying member.
And Ku things heating was press-molded by a pair of molds,
An optical glass molded body is obtained, according to claim 9,
Manufacturing method.