JP2012116688A - Method of manufacturing glass preform for precise press molding, and method of manufacturing optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To certainly mold a preform whose center coincides with the center of the curvature by preventing displacement of the preform (gob) floating in a die.SOLUTION: This method of manufacturing a glass preform for precise press molding includes dividing molten glass made to flow out of an outflow pipe 102a of a preform molding apparatus 100 into molten glass lumps of a predetermined amount, and sequentially supplying the molten glass lumps to a plurality of circulating dies 104 and molding them into preforms. A blast nozzle 210 of a blower 200 is arranged at a predetermined position on a moving route of the dies 104, air flow spirally blowing from the blast nozzle 210 is sprayed to the peripheral edge of each molten glass lump when the die 104 for holding the molten glass lump in a floated state is located under the blast nozzle 210, and a force rotating about the axis along the vertical direction is applied to the molten glass lump, thereby molding a molten glass lump on the moving die 104.

Description

  The present invention relates to a method for producing a precision press-molding glass preform for separating a glass lump of a constant weight from molten glass and forming the glass preform for precision press molding, and press-molding the molded glass preform. The present invention relates to an optical element manufacturing method for manufacturing a desired optical element.

In general, as a method of manufacturing a lens or other optical product having a highly accurate shape, a preform for press molding (so-called gob) is formed from molten glass, and the optical element is formed by press-molding the gob into a predetermined shape. The precision press molding method to manufacture is known.
The precision press molding method for optical elements does not grind or polish the glass material, but hot forms the gob (preform) from the molten glass lump and forms the curvature of the gob surface to a predetermined value during the cooling process. In this method, the gob is formed into a final product such as a lens by press molding the gob, and a high-precision optical element can be manufactured in large quantities. For this reason, it is suitably used for an optical element that requires high-precision processing and shape, such as an aspheric lens.

Here, as a precision press molding method of this kind, a predetermined weight of molten glass ingot is supplied to a molding die, and hot molding is performed in a state where the molten glass ingot is floated (or substantially floated) in the molding die. A so-called float forming method for forming a gob having a curvature is known.
In the flotation molding method, a plurality of molds are placed on a turntable, and the turntable is rotated to sequentially transfer the molds to a predetermined supply position (cast position) to which a molten glass lump is supplied. The molten glass lump flowing down from the mold is received by each mold, and gob (preform) having a predetermined curvature is sequentially molded in the mold.
The molded gob is conveyed by a turntable, sequentially taken out from the mold at a predetermined take-out position that is a take-out position, and conveyed to a press molding process that is the next process. The mold from which the gob has been taken out is transferred again to the casting position where the molten glass lump flows out by the rotation of the turntable, whereby the gob is continuously formed from the molten glass lump.

In the flotation molding method, the molten glass lump placed in the mold is given an upward wind pressure by the gas / air ejected from the mold, and the molten glass lump is held in a floating state in the mold via the gas cushion. Then, the curvature of the upper surface of the gob is adjusted by pressing, suction, or the like using a mold or air.
In this way, by letting the molten glass lump float through the gas cushion so that the mold and the molten glass lump do not come into contact with each other, the occurrence of wrinkles on the surface of the preform and the so-called can cracking of the glass are prevented. Further, it is possible to prevent deterioration of the mold due to the heat of the molten glass lump, and facilitate maintenance and management of the mold.

As described above, in the precision press molding method, a preform (gob) is directly molded from a molten glass lump by a floating molding method, and an optical product as a final product can be manufactured by press molding in the next process. Compared to the method of manufacturing final products such as lenses through multiple processes such as cutting, processing, pressing, grinding, and polishing of glass materials such as glass plates, high-precision optical products are produced in large quantities continuously and efficiently. An aspherical lens that can be manufactured, and particularly difficult to manufacture by grinding or polishing, can be manufactured with high precision, and is used as a manufacturing method suitable for high-precision optical products.
A precision press molding method using such a floating molding method is disclosed in, for example, Patent Documents 1 to 3.

Japanese Patent No. 4425233 JP 2006-290702 A JP 2007-045696 A

By the way, in the precision press molding method using the float molding method as described above, since the gob is floated, the gob is molded, specifically, the curvature adjustment of the upper surface of the gob is performed. The curvature adjustment operation is performed in an unstable state without being fixed.
For this reason, there has been a problem in that the misalignment of the gob has occurred and accurate molding and curvature adjustment cannot be performed.

Specifically, if the curvature adjustment is performed in a state where the gob is levitated by the floating molding method, the top part (the center of curvature) of the gob upper surface when the gob is viewed from above the mold is shifted from the center of the gob outer periphery. Alternatively, the most depressed portion (center of curvature) of the upper surface of the gob may be displaced from the center of the outer periphery of the gob, and the top portion or the recessed portion of the curvature may be displaced from the center.
When a lens is manufactured by press molding the gob with such a deviation, the thickness becomes large and the optical performance of the lens deteriorates. The problem of becoming difficult occurred.

Here, with respect to such a problem, it is conceivable to provide a configuration or mechanism for preventing the misalignment of the gob on the mold side, but there is a possibility that the mold has a complicated structure.
In addition, a large number of molds are generally provided on the manufacturing apparatus side, and providing such a mechanism for all the molds may complicate the entire manufacturing apparatus. Manufacturing costs are also expected to increase, and in practice it was difficult to realize.

  The present invention has been proposed in order to solve the problems of the conventional techniques as described above, and in a precision press molding method using a floating molding method, without complicating a molding die or an apparatus. , Prevents the position of the preform (gob) that floats in the mold from being displaced, and can reliably form a preform whose center of curvature matches the center of the preform, resulting in uneven thickness during press molding of the preform. It is an object of the present invention to provide a method for manufacturing a precision press-molding glass preform and a method for manufacturing an optical element, which can prevent the above and the like and manufacture a highly accurate optical element.

  In order to achieve the above object, the method for producing a precision press-molding glass preform according to the present invention sequentially separates molten glass that has flowed out of an outflow pipe into a predetermined amount of molten glass lump and circulates it into a plurality of molds that circulate. A method for manufacturing a precision press-molding glass preform that is supplied and molded into a preform, wherein a blow nozzle is installed at a predetermined position on the moving path of the mold, and the molten glass lump is floated. When the mold to be held is positioned below the blow nozzle, an air flow that spirally blows from the blow nozzle is blown to the periphery of the molten glass lump, and the molten glass lump is rotated around an axis along the vertical direction. This is a method of forming the molten glass lump on the moving mold by applying a rotating force.

  In order to achieve the above object, the optical element manufacturing method of the present invention includes a glass preform manufactured by the method of manufacturing a precision press-molding glass preform according to the present invention, and the glass preform is press-molded. As a method for manufacturing an optical element.

According to the method for producing a precision press-molding glass preform and the method for producing an optical element according to the present invention, in the precision press-molding method using the floating molding method, the molding die without incurring complication of the molding die or the apparatus It is possible to prevent the displacement of the preform (gob) that floats inside.
As a result, a preform in which the center of curvature coincides with the center of the preform can be reliably molded, and a highly accurate optical element can be manufactured by preventing the occurrence of uneven thickness during press molding of the preform. Will be able to.

It is the schematic which showed partially an example of the preform shaping | molding apparatus used for the manufacturing method of the glass preform for precision press molding which concerns on one Embodiment of this invention, (a) is a top view, (b) is a side view FIG. It is a figure which shows typically the detail of the ventilation nozzle and shaping | molding die with which the preform shaping | molding apparatus shown in FIG. 1 is equipped, (a) is principal part sectional drawing of a ventilation nozzle and a shaping | molding die, (b) is (a). It is an external appearance perspective view of the center nozzle front-end | tip of the ventilation nozzle shown in FIG. It is principal part sectional drawing which shows the ventilation nozzle shown in FIG. 2, and has shown typically the state of the airflow which blows off from a ventilation nozzle. It is principal part sectional drawing which shows the ventilation nozzle shown in FIG. 2, and has shown typically the dimensional relationship of the front-end | tip opening diameter of a ventilation nozzle, and a preform. It is the schematic which shows an example of the installation position of the ventilation nozzle with which the preform shaping | molding apparatus shown in FIG. 1 is equipped, (a) has shown the 1st position of the ventilation nozzle, (b) has shown the 2nd position similarly.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of a method for producing a precision press-molding glass preform according to the present invention and an optical element producing method for producing an optical element by press-molding a glass preform produced by the method will be described with reference to the drawings. explain.
FIG. 1 is a schematic view partially showing an example of a preform molding apparatus used in a method for producing a precision press-molding glass preform according to an embodiment of the present invention, (a) is a plan view, b) is a side view.
FIG. 2 is a diagram schematically showing details of a blower nozzle and a mold provided in the preform molding apparatus shown in FIG. 1, and (a) is a cross-sectional view of a main part of the blower nozzle and the mold. ) Is an external perspective view of the tip of the center nozzle of the blowing nozzle shown in FIG.

[Preform molding equipment]
A preform molding apparatus 100 shown in these drawings is an apparatus for molding a preform using the precision press molding glass preform manufacturing method according to an embodiment of the present invention. An apparatus for forming and manufacturing a large number of preforms (so-called gob) continuously from a molten glass lump by providing a mold and sequentially supplying a predetermined weight of molten glass onto the mold.

Specifically, as shown in FIG. 1, the preform molding apparatus 100 includes a molten glass supply unit 102 that supplies a molten glass lump that is a raw material of a preform to be manufactured at a predetermined supply position (cast position), A plurality of molds 104 (12 in the example shown in FIG. 1) for receiving a molten glass lump supplied from the glass supply unit 102 and forming it into a predetermined preform (gob), and casting positions of these molds 104 are set. A turntable 106 for transferring to each processing position including the mold, a mold transferring part 108 for driving and controlling the turntable 106, and a mold raising / lowering part 110 for raising and lowering the mold 104 at a predetermined casting position are provided.
Further, the preform molding apparatus 100 improves the shape of the molten glass lump while cooling the molten glass lump by blowing a predetermined air flow (gas / air) from above to the molten glass lump supplied to the mold 104. A blower 200 for adjusting the curvature and thickness is provided.

The molten glass supply unit 102 is installed in accordance with a predetermined casting position of the turntable 106 (position indicated by a two-dot chain line in FIG. 1A), and a molten glass flow melted and melted in a melting furnace (not shown) Outflow and supply to the mold 104 conveyed to the casting position via the outflow pipe 102a.
A temperature control device (not shown) is attached to the outflow pipe 102a of the molten glass supply unit 102 so that the molten glass flow can be controlled to a predetermined viscosity, and the productivity of the glass lump is controlled by the temperature control. It can be controlled.
This temperature control is performed so that the viscosity of the molten glass flowing out from the outflow pipe 102a becomes a predetermined value, for example, 30 to 2 dPa · s, preferably 20 to 5 dPa · s.

The mold transfer unit 108 is a driving unit that supports a turntable 106 on which a plurality of molds 104 are mounted and supported on the upper surface, and that rotates the turntable 106 in a predetermined direction at a predetermined timing.
The turntable 106 is formed of a circular flat plate member disposed and supported in a horizontal direction on the mold transfer unit 108, and a plurality of molds 104 are disposed on the upper surface at equal intervals along the circumferential direction. The turntable 106 is, for example, a disk made of an aluminum alloy that is excellent in weight reduction, and is rotationally driven by driving means (for example, a built-in direct drive motor) provided in the mold transfer unit 108. .
On the outer peripheral portion of the turntable 106, a plurality of molding dies 104 (12 in the example shown in FIG. 1 at an interval of 30 degrees around the rotation axis) are formed at equal intervals along the circumferential direction. It is placed and fixed via.
Then, the turntable 106 repeats the movement of rotating by the interval distance (30 degrees in the example of FIG. 1) of the mold 104 and stopping and rotating in the same direction (30 degrees). Is transferred and conveyed in a predetermined direction at a predetermined timing.

By the rotation of the turntable 106 by the mold transfer unit 108, one mold 104 is transferred to the above-described casting position, stopped once, receives the molten glass lump, and then transferred further downstream from the casting position. The stop / transfer is repeated at a predetermined timing.
Specifically, for example, based on a drive signal from a sequencer, the mold transfer unit 108 repeatedly drives the direct drive motor intermittently to rotate the turntable 106 by a predetermined angle and then stop ( This is called the intermittent index method). By driving the turntable 106 by the intermittent index method, the molding die 104 that has received the molten glass lump is transferred downstream from the casting position, the corresponding position of the blower nozzle 210 of the blower device 200 described later, and the molded preform. After passing through the take-out position (takeout position), the empty mold 104 before receiving the molten glass gob is transferred to the casting position.
By repeating these steps, the molten glass continuously flowing out from the outflow pipe 102a of the molten glass supply unit 102 is sequentially received on the forming mold 104, and is formed into a preform having a predetermined shape and a predetermined curvature, and is conveyed and It will be collected.
In addition, the method of supplying molten glass from the molten glass supply part 102 onto the shaping | molding die 104 is performed by the fall cutting method etc. which are mentioned later, for example.

As shown in FIG. 1B, the mold lifting / lowering unit 110 is disposed immediately below the mold base that holds the mold 104 of the turntable 106 at the casting position where the molten glass lump is supplied.
When the molten glass lump is caused to flow down onto the mold 104 by the molten glass supply unit 102, the mold lifting / lowering unit 110 is driven to move the mold 104 in the cast position up and down, thereby causing a predetermined amount of molten metal. A glass lump is supplied to the mold 104.

Although not particularly illustrated, the mold 104 placed on the turntable 106 is kept at a predetermined temperature in the range from the casting position to the glass lump removal position (takeout position) along the moving locus. Heated or slowly cooled. Thereby, between the cast position and the take-out position, the molten glass on the mold 104 is gradually cooled during the movement between the cast position and the glass lump is molded, and the empty mold from which the glass lump is taken out The mold is heated and kept warm so that the temperature does not drop too much.
Further, a take-out position (not shown) is installed at the take-out position where the molded preform is taken out from the mold 104, and a glass lump having a glass transition point Tg or less is taken out from the mold 104 and carried out to the next process. Is done. For example, as a means for taking out the preform, gas can be blown from the side surface of the mold 104 to the preform thereon, and the preform can be dropped and collected on a collecting device or the like disposed on the opposite side.

As for the some shaping | molding die 104 arrange | positioned on the upper surface of the turntable 106, each shaping | molding die 104 is each mounted on a shaping | molding die base. The mold base is configured to be movable up and down with respect to the turntable 106, and usually a force that pushes down downward is always applied by the biasing force of an elastic body such as a spring.
As described above, the mold raising / lowering unit 110 is installed below the mold base at the casting position of the molten glass, and the drive shaft of the mold raising / lowering unit 110 extends below the mold base. ing.
When casting the molten glass, for example, the mold lifting / lowering unit 110 is driven based on a drive signal from the sequencer, and the drive shaft is lifted to resist the urging force of the mold base spring and the like. Is moved upward.
As a result, the mold 104 is lifted up to the vicinity of the outflow pipe 102 a of the molten glass supply unit 102, and a predetermined amount of molten glass is supplied to the mold 104. At this time, the distance between the tip of the outflow pipe 102a and the upper end of the mold 104 is set to a predetermined value, for example, 5 to 10 mm.

The molten glass supply unit 102 is provided with an outflow pipe 102 a for allowing a molten glass flow melted in a melting furnace (not shown) to flow onto the mold 104. Around the outflow pipe 102a, a heating means such as a heater (not shown) is arranged so that the temperature of the nozzle and thus the temperature of the molten glass are kept constant.
Thereby, the outflow speed of the molten glass is kept constant, and the viscosity of the outflowing molten glass is set to a value suitable for forming a glass lump, for example, 30 to 2 dPa · s, preferably 20 to 5 dPa · s. Be controlled. By controlling the viscosity of the molten glass within a predetermined range, a glass lump having high internal quality without striae can be obtained.

Here, in the preform molding apparatus 100 of the present embodiment, a descending cutting method can be adopted in order to stably flow down and supply a glass lump having a predetermined weight.
Hereinafter, the outline of this descent cutting method will be described.
As described above, when the mold 104 is transferred to a predetermined casting position, the mold lifting / lowering unit 110 is operated based on a drive signal from a sequencer or the like, and the drive shaft of the mold lifting / lowering unit 110 drives the mold base. The movable part can be pushed up.
In a state where there is no push-up by the drive shaft, the movable part of the mold base is pressed downward by an urging force of a spring or the like and kept at a constant height, but when the drive shaft of the mold lifting / lowering part 110 is operated, The movable part of the mold base is pushed up against an elastic force such as a spring and lifted together with the mold 104, and the molding surface of the mold 104 is brought close to the outflow pipe 102a. At this time, the distance between the tip of the outflow pipe 102a and the upper end of the mold 104 is set and controlled so as to be a predetermined value such as 5 to 10 mm.

When the molding surface of the molding die 104 is brought close to the outflow pipe 102a by the driving of the molding die lifting unit 110, supply of the molten glass flow to the molding surface is started.
When the mold is lifted by the mold lifting / lowering unit 110 after a certain time has elapsed, the movable part of the mold base is faster than the flow rate of the molten glass flow due to the biasing force of the mold base spring or the like. And the mold 104 is instantaneously pulled away from the outflow pipe 102a and suddenly descends to the same height as before the ascent.
Before the mold 104 is lowered, the lower end of the molten glass flowing out from the outflow pipe 102a is supported by the mold 104, but the support is rapidly lost due to the rapid lowering of the mold 104, and the lower end of the molten glass and the outflow are discharged. The molten glass is separated and cut between the pipes 102 a, and a predetermined amount of the molten glass lump is supplied into the mold 104.

The descending cutting method as described above has an effect that the trace of the cut portion is less likely to remain than in the case of using the cutter because the molten glass is separated and cut by its own weight without using the cutter.
Further, when the molten glass is received by the mold 104, the mold 104 only moves in the vertical direction, and there is a feature that folding or the like that occurs when the molten glass is cut is less likely to occur in the glass lump.

Each of a plurality of (for example, twelve) molds 104 placed on the turntable 106 via a mold base is provided with a gas pipe (not shown), and a glass lump supplied to the recess of each mold 104 is provided. Gas for rising or substantially rising is supplied.
The gas is ejected from a plurality of gas outlets 104a (see FIG. 2A) formed on the molding surface of the molding die 104, whereby the glass lump in the concave portion of the molding die 104 is floated or substantially omitted by the gas cushion. A predetermined molding process or the like is performed in a floating state.
Specifically, as shown in FIG. 2A, a plurality of gas injection holes 104 a are provided over a certain region of the inner surface of the concave portion of the mold 104. A gas is ejected from these gas ejection holes 104a, and an upward wind pressure is applied to the molten glass lump on the recessed portion, and the glass lump is lifted from the recessed portion or intermittently levitated to contact the glass lump and the mold 104. Is avoided or the contact time is shortened.
Thereby, in the preform shaping | molding apparatus 100 which concerns on this embodiment, a molten glass lump can be hot-molded in the state which floated (or substantially floated) within the shaping | molding die, and has a predetermined | prescribed surface curvature in a floating state. A flotation method that forms the gob can be used.

In the flotation molding method, the molten glass lump is floated through a gas cushion by the gas that is ejected, and the contact between the mold 104 and the molten glass lump can be reduced or avoided. It is possible to prevent the occurrence of glass breakage called cracking, to prevent deterioration of the mold due to the heat of the molten glass lump, and to facilitate maintenance and management of the mold.
Here, as the gas that floats or substantially floats the glass lump, for example, air, an inert gas such as nitrogen, or a mixed gas thereof can be used.
In addition, the number and distribution of the gas jets 104a formed in the mold 104, the locations where the gas jets 104a are formed, the diameter of the jets, and the like can be set to arbitrary values that can float the molten glass lump. Further, the recess of the mold 104 can be formed of a porous material so that gas can be ejected.
And the cooling and shaping | molding process by the air blower 200 are performed with respect to the molten glass lump which floated by the gas cushion.

[Blower]
The blower device 200 is installed at a predetermined location downstream of the casting position where the molten glass lump is supplied, and blows and blows gas from above to the molten glass lump supplied in a floating state in the mold 104. Cooling / molding means to form the molten glass lump to the desired curvature by forming the shape of the molten glass lump and adjusting the curvature / thickness while cooling the molten glass lump. It is.
Specifically, as shown in FIG. 1, the blower 200 is disposed at a position corresponding to a predetermined mold 104 subsequent to the cast position where the molten glass supply unit 102 is provided. In the example shown in FIG. 1, the blower device 200 is disposed at the position of the molding die 104 positioned next to the cast position.
The blower 200 is connected to a main body for supplying predetermined gas / air, and the main body via a duct (see ducts 211a and 214a shown in FIG. 2A) and above the mold 104. A blower nozzle 210 that is disposed and ejects predetermined gas / air from the opening of the tip is provided (see FIG. 2).
Then, the blower device 200 ejects gas from above toward the molten glass lump in the mold 104 at the timing when the forming mold 104 that has been transferred by the rotation of the turntable 106 stops. A predetermined molding process is performed while cooling.

[Blower nozzle]
In the present embodiment, as shown in FIG. 2, the blowing nozzle 210 of the blower device 200 has a predetermined structure, so that the molten glass lump is floated on the mold 104, and the molten glass lump is aligned along the vertical direction. The curvature of the upper surface of the molten glass lump is controlled while correcting the position by applying a rotating force around the axis.
Specifically, as shown in FIG. 2A, the blower nozzle 210 has a double structure including two cylindrical bodies of a center nozzle 211 and an exterior material 213, and the center nozzle 211 and the exterior material. 213 and the nozzle base 214 are integrally formed.

First and second nozzles 211a and 214a are connected to the center nozzle 211 and the nozzle base 214, respectively, and gas and air are supplied from the main body of the blower 200 by two air blow controls. Yes.
And by the double structure of such a cylindrical body, while the 1st blower outlet 210a which blows off air current in the perpendicular direction is provided in the central part of blower nozzle 210, at the peripheral part of blower nozzle 210, A second air outlet 210b that is arranged around the first air outlet 210a and that blows out the airflow spirally is provided.
In addition, such a ventilation nozzle 210 can be comprised with a metal etc. which are suitable as a gas supply pipe, for example, can be comprised with metal pipes, such as stainless steel.

The center nozzle 211 is made of a substantially linear cylindrical tubular member, and the opening on the front end side of the center nozzle 211 is a first outlet 210a.
The rear end portion of the center nozzle 211 communicates with and is connected to the first duct 211a. Although not shown in FIG. 2A, the first duct 211a is connected to the main body of the blower 200. (Refer to FIG. 1 (b)), and the gas sent from the main body of the blower device 200 is blown out vertically downward from the front end opening (first outlet 210a) by air blow control.

Here, as the gas / air to be ejected from the front end opening (the first outlet 210a) of the center nozzle 211, for example, air, nitrogen, etc., like the preform floating gas to be ejected from the mold 104 described above. An inert gas or a mixed gas thereof can be used.
And the front-end | tip part 212 of this center nozzle 211 is covered with the exterior material 213, becomes a double structure, and these center nozzles 211 and the exterior material 213 are integrated in the nozzle base 214, and the ventilation nozzle 210 is comprised.
The exterior material 213 is a cylindrical member that is disposed and mounted so as to cover the front end portion 212 of the center nozzle 211 from the outside, and constitutes the blower nozzle 210 together with the center nozzle 211.

More specifically, the exterior material 213 is disposed so that one end side is abutted against the outer surface in the vicinity of the opening of the center nozzle 211, and a predetermined gap 213 a is formed between the exterior material 213 and the center nozzle 211. This is a cylindrical member.
The rear end side of the exterior material 213 is continuous with the nozzle base 214. By connecting the rear end portion of the center nozzle 211 and the first duct 211a to the nozzle base 214, the center nozzle 211 and the exterior material 213 are connected. Integrally form the air blowing nozzle 210.
In addition, a second duct 214a of a different system from the first duct 211a of the center nozzle 211 is connected to the side surface of the exterior material 213 (or the nozzle base 214), and gas sent from the main body of the blower 200 Is supplied to the gap 213a formed by the exterior material 213 through the second duct 214a.

A plurality of guide grooves 212a are spirally engraved at the interface where the outer surface in the vicinity of the opening of the center nozzle 211 and the inner surface on one end side of the exterior material 213 face each other. The second outlet 210b is formed around the outlet 210a.
In the present embodiment, the guide groove 212 a is provided by engraving a predetermined spiral groove on the surface of the tip 212 of the center nozzle 211.
As described above, in the present embodiment, the guide grooves 212a are formed on the surface of the center nozzle 211, whereby the guide grooves 212a having a desired shape and number can be easily provided.
Further, the center nozzle 211 can be attached / detached / replaced integrally with the blower nozzle 210, whereby a guide groove 212 a having a different shape or number of grooves, an opening diameter (diameter of the second outlet 210 b), or the like, A plurality of center nozzles 211 having different opening diameters (diameters of the first outlets 210a) can be exchanged and used.

Here, the shape and number of guide grooves 212a engraved in the center nozzle 211, the thickness and depth of the grooves, the opening diameter, and the like depend on the size and curvature of the preform to be molded. In addition, by preparing a plurality of center nozzles 211, it is possible to cope with the molding of preforms having different sizes and curvatures.
For example, the opening diameter of the second outlet 210b formed by the guide groove 212a is φ6, 8, 10, 12, 14, 15, 16, 18, 20, corresponding to the outer diameter of the preform to be processed. The center nozzle 211 having a plurality of opening diameters can be prepared. In this case, the blow nozzle 210 including the center nozzle 211 of each size is prepared, and an identification display such as the size can be displayed on the surface of the blow nozzle 210 by marking or the like.
The blower nozzle 210 including the center nozzle 211 can be replaced by removing and replacing the entire blower nozzle 210 by removing the first duct 211a and the second duct 214a from the nozzle base 214, for example.

The guide groove 212a for ejecting the spiral airflow as described above may be provided at the interface between the outer surface near the opening of the center nozzle 211 and the inner surface of the exterior material 213. A configuration other than that engraved on the center nozzle 211 side can also be employed.
For example, any structure can be used as long as the guide groove 212a can be provided by engraving a spiral groove on the inner peripheral surface of the exterior material, and a spiral air current can be ejected to the molten glass lump. It is also good.

The exterior material 213 is connected to a second duct 214a of a different system from the first duct 211a of the center nozzle 211.
As shown in FIG. 2A, the exterior material 213 has a nozzle base 214 connected to the rear end side, and between the exterior surface of the exterior material 213 and the nozzle base 214 and the outer periphery of the center nozzle 212. A gap 213a is formed. The second duct 214a is connected to and connected to the gap 213a.
In the example shown in FIG. 2A, the second duct 214a is communicated with and connected to the side surface of the exterior material 213 (or the nozzle base 214), whereby the second duct 214a, the gap 213a, and the guide groove 212a. Has come to communicate. And although illustration is abbreviate | omitted in Fig.2 (a), this 2nd duct 214a is connected to the main body of the air blower 200. FIG.

Thereby, the gas sent from the main body of the blower device 200 by the air blow control is different from the gas ejected from the first outlet 210a described above, and the second duct 214a, the air gap 213a, and the guide groove 212a. Via the second air outlet 210b which opens around the first air outlet 210a.
The gas ejected in a spiral form from the second outlet 210b is the same as the gas ejected from the first outlet 210a of the center nozzle 211, for example, an inert gas such as air or nitrogen, or a mixed gas thereof. Etc. are used.

Here, the gas supply to the first duct 211a of the center nozzle 211 and the second duct 214a of the exterior material 213 can be independently performed by two air blow controls. Gas can be ejected independently from the one outlet 210a and from the second outlet 210b via the gap 213a of the exterior material 213.
Accordingly, gas can be ejected from the blower nozzle 210 from the first blowout port 210a and the second blowout port 210b, respectively, at a predetermined timing, and the first blowout port 210a or the second blowout port 210b. The gas can be ejected from only one of them, and the gas can be ejected simultaneously or substantially simultaneously from both the first outlet 210a and the second outlet 210b.

And the air blower 200 provided with the above air blowing nozzles 210 is the air blowing nozzle 210 in the state which the air blowing nozzle 210 has been arrange | positioned above the shaping | molding die 104 which received the molten glass lump transferred by the turntable 106. FIG. By blowing the airflow blown out spirally from the second blowout port 210b to the periphery of the molten glass lump, it is possible to give the molten glass lump a force that rotates around the axis along the vertical direction.
Since the air flow blown out from the second blow-out port 210b is blown out along the spiral guide groove 212a, the spiral air flow (spiral air) is blown out while spreading from the nozzle tip as shown in FIG. . Therefore, the molten glass lump rotates around the center of the molten glass lump by blowing the airflow (gas / air) blown out spirally on the periphery of the lump that floats in the mold 104 in this way. It will rotate as the center.

Thus, by rotating the molten glass lump with a spiral air flow (spiral air), the attitude of the molten glass lump (preform, gob) floating in the mold 104 can be stabilized and corrected. The curvature of the upper surface of the preform can be adjusted while correcting and holding the position of the preform floating in the mold so that the center of curvature coincides with the center of the outer periphery of the preform.
In addition, since the position and posture of the molten glass lump in the mold can be stabilized and corrected from above the mold 104 by air blowing means independent of the mold 104, the mold itself is changed or improved. There is no need, and it is possible to realize preform position control and position correction with a simple structure without making the mold complicated. Therefore, the manufacturing cost of the preform molding apparatus 100 does not increase, and it is possible to provide a preform molding apparatus that can be easily applied to existing apparatuses and has excellent versatility and expandability.

Here, as shown in FIG. 3, the spiral air is blown out while spreading from the nozzle tip. For this reason, in order to effectively rotate the air flow against the periphery of the molten glass lump (preform), as shown in FIG. 4, the opening diameter of the guide groove 212a (second outlet 210b) is the object to be molded. It is preferable to select one that is slightly smaller than the outer diameter of the molten glass lump (preform).
The selection / change of the opening diameter of the guide groove 212a (second outlet 210b) may be performed by preparing a plurality of blower nozzles 210 (center nozzle 211) as described above and selecting / removing / changing the nozzles.

Further, the position, range, and strength of the spiral airflow that hits the peripheral edge of the molten glass lump (preform) can also be adjusted by changing the height of the blow nozzle 210. When spiral air does not hit the peripheral edge of the preform or when the momentum of the airflow is weak, the molten glass lump cannot be sufficiently rotated around the center of curvature of the preform as the rotation center. On the other hand, if too much air is discharged, the molten glass lump moves too much in the mold. Defects such as O mistakes, scratches and dirt may occur.
Therefore, for example, if the height of the blow nozzle 210 is adjusted while looking at the quality of the preform to be molded, a highly accurate and high quality preform can be reliably molded.
As a means for adjusting the height of the blower nozzle 210, a well-known adjusting means / adjusting device or the like for adjusting the height of the entire duct provided in the main body of the blower 200 can be used, although not particularly shown.

In addition, by rotating the molten glass lump in the mold by the spiral air flow as described above, it is possible to prevent the occurrence of uneven thickness of the preform and the decrease in roundness, etc. Curvature and wall thickness can be adjusted.
As described above, in this embodiment, the preform is molded while the mold 104 is moved by the turntable 106, but the molten glass lump is moved in a specific direction on the mold by moving the mold 104. Will swing. In the conventional preform molding apparatus, there has been a problem that when the molten glass lump swings, the molten glass lump is biased and the roundness of the outer periphery of the preform is difficult to obtain.
In the present embodiment, the molten glass lump (preform) is rotated by the spiral air in the mold 104 as described above, so that even when the molten glass lump is swayed in a specific direction due to the movement of the mold 104, the vibration is also shaken. The force due to ceases to work only in one direction of the molten glass lump, and the roundness of the outer periphery of the preform can be increased.
As a result, it is possible to mold and manufacture a preform with no roundness and high roundness, prevent uneven thickness from occurring during the press molding of the next process, and to mold and manufacture a highly accurate optical element. It becomes possible.

Moreover, an air current can be blown out spirally from the peripheral part (second outlet 210b) of the air blowing nozzle 210 disposed above the mold 104, and negative pressure can be generated in the atmosphere inside the air current. Thereby, the upper surface of a molten glass lump can be attracted | sucked and the curvature of the said upper surface can be controlled.
As described above, the spiral air current is spouted along the peripheral edge of the molten glass lump while spreading from the tip of the second outlet 210b of the blow nozzle 210 (see FIG. 3). For this reason, the inside of the spiral air above the molten glass lump is in a negative pressure state where no airflow exists. And, by this negative pressure state, a suction force is generated upward in the vertical direction on the upper surface of the molten glass lump.

Accordingly, by ejecting spiral air from the second outlet 210b of the blower nozzle 210, a negative pressure is generated inside the airflow, and the upper surface of the molten glass lump can be sucked by this negative pressure, thereby the molten glass. The curvature of the top surface of the mass can be controlled.
Particularly, since a suction force due to a negative pressure is applied, it is preferable when the curvature is controlled by expanding the center of the upper surface of the preform into a top shape.
As a result, the molten glass lump can be rotated with the center of curvature as the center of rotation by a spiral air flow, and the center of curvature can be sucked and swelled by negative pressure to control the curvature. The curvature of the upper surface of the preform can be adjusted so that the center of the outer periphery of the preform coincides with the preform, and more accurate preform molding can be realized.

In addition, also in the curvature control of the molten glass block by this negative pressure, it is desirable to adjust the size of the opening diameter of the guide groove 212a (second blowing port 210b) and the height of the blowing nozzle 210.
Accordingly, also in this case, the height of the blowing nozzle 210 is adjusted while observing the state of the preform to be molded, the curvature, etc., and the preform having a desired curvature is selected and changed by changing the size of the blowing nozzle 210, etc. Can be reliably molded.

Furthermore, the upper surface of the molten glass lump can be pressurized to control the curvature of the upper surface by blowing an air flow vertically downward from the center of the blow nozzle 210 and blowing the air flow toward the center of the molten glass lump. it can.
That is, in this embodiment, the upper surface of the molten glass lump can be pressurized by ejecting a vertically downward air flow (center air) from the first outlet 210a of the center nozzle 211 of the blower nozzle 210. The curvature of the upper surface of the preform can be controlled.

The blower nozzle 210 according to the present embodiment generates a vertically downward airflow (center air) on the upper surface of the molten glass lump through the first air outlet 210a of the center nozzle 211 by air blow control different from the spiral airflow. Can be ejected.
Therefore, the upper surface of the molten glass lump can be directly pressurized by ejecting the center air from the first outlet 210a of the blow nozzle 210, and the curvature of the upper surface of the molten glass lump is controlled by the action of this air pressurization. can do.
In particular, since pressurization is performed by a vertically downward airflow, it is preferable for curvature control when the upper surface center of the preform is flattened or formed so as to be recessed.
Further, the center air is blown over the entire upper surface of the molten glass lump, so that the molten glass lump is cooled and the occurrence of striae is prevented.

As a result, the molten glass lump can be rotated around the center of curvature by the spiral airflow from the second outlet 210b, and the curvature can be controlled by pressurizing the center of curvature with vertically downward air. Further, the curvature of the upper surface of the preform can be adjusted so that the center of curvature coincides with the center of the outer periphery of the preform, so that more accurate preform molding can be realized.
Therefore, when the center air is pressurized by the center air from the first air outlet 210a of the center nozzle 211, both the air outlets 210a and 201b are used together with the rotation control by the spiral air from the second air outlet 210b. These airs are preferably ejected at the same time, almost at the same time, or around the same time.
In this case, the center air from the first outlet 210a may be ejected first, and the spiral air from the second outlet 210b may be ejected first. Further, it is possible to prevent the center air from being ejected from the first outlet 210a.

In addition, also in the curvature control of the molten glass lump by the center air from the first outlet 210a, the size of the opening diameter of the center nozzle 211 (first outlet 210a) and the height of the blower nozzle 210 are adjusted. Is desirable.
In particular, the center air from the center nozzle 211 has a pulsating effect that eliminates striae, but if the size (opening diameter) of the center nozzle 211 is too small, the pulsating effect is weakened, and only the center part of the preform The striae may disappear and remain in the surrounding area. For this reason, selection of the opening diameter of the center nozzle 211 is important.
Accordingly, for the center air blown out from the center nozzle 211, the height of the blow nozzle 210 is adjusted while checking the state of the preform to be molded, the curvature, the presence or absence of striae, the size of the blow nozzle 210, etc. By selecting / changing, it is possible to reliably form a preform having a desired curvature.

When a desired preform is molded through the molding and cooling process by the blower 200 as described above, the molding die 104 that holds and accommodates the preform is rotated as shown in FIG. From the casting position (the position indicated by the two-dot chain line), the sheet is further transferred in the clockwise direction, and is conveyed to a predetermined take-out position (takeout position) while the glass is gradually cooled in the transfer process.
Then, at a predetermined take-out position, the preform is blown off from the forming die 104 by a take-out means (not shown), for example, by a jetting gas, and is conveyed and collected to the press forming apparatus in the next process. Note that the preform at a predetermined take-out position is gradually cooled to a temperature not higher than the glass transition point Tg.

The mold 104 in which the preform is taken out and the recess is emptied is then heated to a temperature suitable for receiving the molten glass by a heating means (not shown). Then, the molten glass lump is transferred again to the casting position where the molten glass lump is supplied, and the next preform is formed by receiving the supply of the molten glass lump.
In this way, by circulating each mold 104, a desired preform is sequentially formed and manufactured from the molten glass lump with high accuracy.

[Preform manufacturing method]
Next, a preform manufacturing method according to the present embodiment using the preform molding apparatus 100 as described above will be described.
First, in carrying out the preform manufacturing method of the present embodiment, the use / installation position of the blower device 200 and the size of the blower nozzle 210 are selected.
The use (installation) position of the blower 200 is selected according to the position of the preform to be molded / manufactured according to the position where the blower 200 is installed, that is, the position where air is blown to the molten glass lump supplied to the mold 104 at the casting position. This is because the results may differ.

Specifically, first, when the present embodiment is used mainly for improving the shape of a preform, two positions are assumed as the use positions of the blower 200 as shown in FIG.
The first position shown in FIG. 5A is a case where the blower 200 is installed so that the blower nozzle 210 is disposed at a position corresponding to the next molding die of the cast position 102 on the turntable.
In this case, the use position of the blower device 200 corresponds to a position immediately after the casting position 102, and at this position, the molten glass lump of the mold 104 is immediately after being supplied from the molten glass supply unit 102 and is in a softer state. For this reason, the molten glass lump can be rotated in a soft state by the spiral air according to the present embodiment, the roundness can be made more accurate, and the effect of shape improvement by the spiral air is exhibited. It will be easy to make it.

On the other hand, in the second position shown in FIG. 5B, the blower device 200 is installed so that the blower nozzle 210 is disposed at a position corresponding to the mold next to the first position shown in FIG. Is the case.
In this case, the use position of the blower device 200 is a position where the elapsed time from the supply of the molten glass lump is longer than that of the first position, so that the molten glass lump is cooled more than the first position, It is in a solid state. For this reason, the molten glass lump can be rotated by spiral air in a state in which the molten glass lump is solidified to some extent, and preform molding with little influence of striae becomes possible.

When the spiral air (and center air) according to the present embodiment is used mainly for curvature and thickness adjustment, the use position of the blower device 200 is not limited to the first and second positions, The blower device 200 can be installed at an arbitrary location, and the suction effect of spiral air, the pressurization effect by center air, and the like can be utilized.
In that case, it is also possible to install the blower 200 at a plurality of locations.

The size of the blow nozzle 210 is selected according to the shape and size of the preform to be molded, the opening diameters of the first blow port 210a and the second blow port 210b of the blow nozzle 210, and the center nozzle 211. The selection is made based on the number and shape of the guide grooves 211a.
At this time, the opening diameters of the first and second outlets 210a and 210b and the selection of the guide groove 211a can be performed based on information such as markings displayed on the outer surface of the nozzle.

For example, spiral air blown out from the second blow-out port 210b is blown out while spreading from the tip of the nozzle. Therefore, in order to effectively rotate the air flow against the periphery of the molten glass lump (preform), as shown in FIG. In addition, it is preferable to select one having an opening diameter of the second outlet 210b slightly smaller than the outer diameter of the molten glass lump (preform) to be molded.
Further, for example, the center air from the first outlet 210a of the center nozzle 211 has a pulsating effect of the preform, but if the opening diameter of the center nozzle 211 is not sufficient, the pulsating effect is weakened and the preform is reduced. There is a risk that the striae will disappear only in the central part of and remain in the peripheral part. For this reason, it is desirable to select so that the opening diameter of the center nozzle 211 is not too small.

After the use position of the blowing device 200 and the selection of the blowing nozzle 210 as described above, necessary preparations are made for the preform molding device 100, and the device is started to start manufacturing.
First, when both the center air and spiral air of the blower nozzle 210 are used, two systems of air blow control for controlling both airs independently are performed.
In addition, the preform molding apparatus 100 is provided with a plurality of molds 104 (in this embodiment, 12) for molding a molten glass lump into a preform.
These molding dies 104 have the same specifications, are arranged at predetermined positions on the turntable 106, and rotate around the turntable 106 while sequentially moving to a predetermined stop position by index rotation.

An outflow pipe 102a of the molten glass supply unit 102 for flowing out the molten glass is disposed above the mold 104 that is retained at the casting position that is the supply position of the molten glass lump (see FIG. 1B).
The forming die 104 staying at the casting position is pushed up by the forming die raising / lowering part 110 at the lower part of the turntable and brought close to the outlet of the outflow pipe 102a. From the pipe outlet, clarified and homogenized molten glass is continuously discharged at a constant flow rate by a known method.
After the lower end of the molten glass is received and supported by the mold 104 that is pushed up by the mold raising / lowering part 110, the mold is rapidly lowered vertically by releasing the pushing of the mold raising / lowering part 110 at a predetermined timing.

Thereby, the molten glass is separated between the parts received on the outflow pipe side and the mold side, and a molten glass lump is obtained on the mold. The adjustment of the distance between the outflow pipe 102a and the forming die 104 is preferable from the viewpoint of adjusting the distance with high accuracy by adjusting the push-up amount in a predetermined unit, for example, 10 to 100 μm.
The molten glass block received by the mold 104 is levitated by the air ejected from the concave portion of the mold 104 and is held in a levitated state without contacting the mold 104.

Next, the molten glass lump on the mold 104 is unloaded and transferred from the casting position to the downstream side together with the mold 104 as the turntable 106 rotates, and is cooled and molded by the blower 200.
Here, when the main purpose is to improve the shape of the preform, as described above, the position corresponding to the molding die next to the cast position (the first position shown in FIG. 5A) or the cast position. In the position corresponding to the next mold (the second mold from the cast position) (second position shown in FIG. 5B), the melt is caused by the ejection of air from the blow nozzle of the blower 200. The glass lump is cooled and shaped.

First, when air is ejected at the first position (FIG. 5A), the molten glass lump of the mold 104 is in a softer state at the position immediately after the casting position 102.
For this reason, by using the spiral air which concerns on this embodiment, a molten glass lump can be rotated in a soft state, and a roundness can be taken out more accurately. As a result, a preform having an improved shape can be obtained.
On the other hand, when the molten glass lump is soft and receives spiral air ejection, the surface of the molten glass lump is easily pulled due to the negative pressure / suction effect of the spiral air.

Therefore, at this first position, the spiral air from the second outlet 210b is used together with the center air from the first outlet 210a, and the center air prevents the occurrence of striae while Rotating and forming process.
Here, the spiral air and the center air can be ejected almost at the same time. However, in order to enhance the effect of the pulsation by the center air, it is better to eject the center air first and delay the spiral air. More preferred.

On the other hand, when the air is ejected at the second position (FIG. 5B), the elapsed time since the molten glass lump is supplied is longer than that at the first position. Is cooled and hardened to some extent than in the first position.
For this reason, even if a molten glass lump is rotated by spiral air according to the present embodiment, the molten glass lump in a solidified state is not affected by striae.
Therefore, in this case, the center air can be ejected at an arbitrary timing, and the center air may not be used depending on the shape and curvature of the preform.

In addition, when spiral air and center air are used for the purpose of curvature and thickness adjustment, spiral air and center air can be ejected and used at any timing while looking at the shape of the molten glass lump.
In this case, the turntable 106 is rotated and stopped at any time, and the obtained preform is confirmed by visual observation or the like, or the size, shape, curvature, etc. of the preform are checked with a predetermined gauge, etc. The ejection amount, the timing of ejection, etc. can be changed and adjusted at any time.

Next, the timing for stopping the ejection of air from the blower nozzle 210 will be described.
As for the timing of stopping the air, first, when the spiral air (and the center air) is used mainly for improving the shape of the preform, the spiral air is stopped simultaneously with the center air.
When the stop of spiral air is earlier than the stop of enter air, the curvature of the preform tends to be larger by pressing the center air. On the other hand, when the spiral air stop is slower than the center air stop, the curvature of the preform tends to rise due to the spiral air suction effect. For this reason, it is desirable to stop spiral air and center air simultaneously.

However, the stop timing of both airs can be set at an arbitrary timing while checking the quality of the preform.
In addition, when spiral air and center air are used mainly for curvature and thickness adjustment, the stop timing of both airs is set to an arbitrary timing while looking at the shape of the preform.

After the cooling and the predetermined molding process are performed by the air from the blow nozzle 210 as described above, the preform on the mold 104 is cooled to a temperature range where the glass is not deformed, and a predetermined take-out position (takeout) To the position), taken out of the mold and slowly cooled. This preform is transferred to a precision press molding process which is the next process.
The molding die 104 which has been emptied by taking out the preform is transferred to the casting position by the rotation of the turntable 106, and the above steps are repeated.
By repeatedly performing the above steps for each of the plurality of molds 104, preforms can be formed one after another from the molten glass lump that continuously flows out.

Next, the case where there is striae in the molded and manufactured preform will be described.
First, when the formed preform has striae, the preform is formed in a state in which only spiral air is stopped in the same forming process as the preform having striae.
Then, the preform is checked again for the presence or absence of striae.

If there is striae in the preform formed by stopping only the spiral air, the striae is not influenced by the spiral air, so adjustment is made by ordinary striae measures.
For example, the position of the center air and the air volume can be adjusted, or the use position of the blower 200 can be changed.

On the other hand, when there is no striae in the preform formed by stopping only the spiral air, the striae is caused by the spiral air.
In this case, adjustment is performed by the following method.
(1) Strengthen the center air (pulse extinction) (harden the surface early to eliminate striae).
(2) Delay the timing of spiral air.
(3) Decrease the spiral air flow.
(4) Adjust the height of the spiral.
Make adjustments as described above and check the preforms until adjustment disappears.
As described above, a high-quality and high-precision preform without striae can be formed.

[Method for Manufacturing Optical Element]
Next, a precision press molding method is taken as an example of the optical element manufacturing method using the preform (gob) molded and manufactured by the preform molding apparatus and preform manufacturing method according to the present embodiment as described above. explain.
The optical element manufacturing method described below is a method in which a part or all of the precision press-molding preform manufactured and mass-produced by the preform manufacturing method shown in the above-described embodiment is precision press-molded.

The precision press molding is also called a mold optics molding method, and is a method of forming the shape of the optical functional surface by press molding, which is already well known in the technical field to which the present invention belongs.
A surface that transmits, refracts, diffracts, or reflects light rays of the optical element is called an optical functional surface. For example, taking a lens as an example, a lens surface such as an aspherical surface of an aspherical lens or a spherical surface of a spherical lens corresponds to an optical function surface.
The precision press molding method is a method of forming an optical functional surface by press molding by precisely transferring a molding surface of a press mold to glass. That is, it is not necessary to add machining such as grinding or polishing to finish the optical functional surface.

As a press mold used in the precision press molding method, a known mold, for example, a mold having a release film on a molding surface of a mold material such as silicon carbide or super hard material can be used. Among these, it is preferable to use a press mold made of silicon carbide.
As the release film, a carbon-containing film, a noble metal alloy film, or the like can be used. From the viewpoint of durability and cost, it is preferable to use a carbon-containing film.
In the precision press molding method, it is desirable that the molding atmosphere be a non-oxidizing gas atmosphere in order to keep the molding surface of the press mold in a good state. As the non-oxidizing gas, it is preferable to use nitrogen, a mixed gas of nitrogen and hydrogen, or the like.

Next, a precision press molding method particularly suitable for the method for producing an optical element of the present invention will be described.
[Precision press molding method 1]
In this method, the preform is introduced into a press mold, the mold and the preform are heated together, and precision press molding is performed.
In this precision press molding method 1, the temperature of the press mold and the preform is heated to a temperature at which the glass constituting the preform exhibits a viscosity of 10 ⁶ to 10 ¹² dPa · s to perform precision press molding. Is preferred.
In addition, after the glass is cooled to a temperature exhibiting a viscosity of 10 ¹² dPa · s or more, more preferably 10 ¹⁴ dPa · s or more, and even more preferably 10 ¹⁶ dPa · s or more, the precision press-molded product is removed from the press mold. It is desirable to take it out.
Under the above conditions, the shape of the molding surface of the press mold can be accurately transferred with glass, and the precision press molded product can be taken out without being deformed.

[Precision press molding method 2]
In this method, after heating the preform, the preform is introduced into a press mold and precision press molding is performed. That is, the press mold and the preform are separately preheated, and the preheated preform is introduced into the press mold. Precision press molding. According to this method, since the preform is preliminarily heated before being introduced into the press mold, it is possible to manufacture an optical element with good surface accuracy free from surface defects while shortening the cycle time.
In addition, it is preferable to set the preheating temperature of the press mold lower than the preheating temperature of the preform. Thus, by lowering the preheating temperature of the press mold, the consumption of the mold can be reduced.
Further, according to this method, since it is not necessary to perform preform heating in the press mold, the number of press molds to be used can be reduced.

In the precision press molding method 2, it is preferable that the glass constituting the preform is preheated to a temperature exhibiting a viscosity of 10 ⁹ dPa · s or less, more preferably 10 ⁹ dPa · s.
The preform is preferably preheated while floating, and the glass constituting the preform is preferably 10 ^5.5 to 10 ⁹ dPa · s, more preferably 10 ^5.5 dPa · s to 10 ⁹ dPa · s. More preferably, it is preheated to a temperature showing a viscosity of less than s.
Moreover, it is preferable to start cooling the glass simultaneously with the start of the press or during the press.

The temperature of the press mold is adjusted to a temperature lower than the preheating temperature of the preform, and the temperature at which the glass exhibits a viscosity of 10 ⁹ to 10 ¹² dPa · s may be used as a guide.
In this method, it is preferable that after the press molding, the glass is cooled to a viscosity of 10 ¹² dPa · s or more and then released.

In this embodiment, a press mold having at least an upper mold and a lower mold, different shapes of the upper mold molding surface and the lower mold molding surface is used, and a preheated preform is supplied onto the lower mold. Press molding can be performed.
In this embodiment, a preform having a desired surface shape can be manufactured on both the upper surface and the lower surface. By using this preform, a press mold having different upper surface and lower surface forming surface shapes can be obtained. Even if it is used, the optical element can be manufactured with high productivity without causing problems such as a gas trap.
The precision press-molded optical element is taken out from the press mold and gradually cooled as necessary. Further, when the lens is molded, centering may be performed.

  Thus, in this embodiment, for example, various lenses such as a spherical lens, an aspheric lens, and a micro lens, a diffraction grating, a lens with a diffraction grating, various optical elements such as a lens array, a prism, and a digital camera as an application. Guides light used for data reading and / or data writing on optical recording media such as lenses that constitute imaging optical systems for cameras with built-in cameras and cameras, camera-equipped mobile phones, and CDs and DVDs Therefore, various optical elements such as lenses can be manufactured. In addition, if a preform made of copper-containing glass is used, an optical element having a color correction function of a semiconductor imaging element can be produced. Among them, it is suitable as a method for producing a lens mounted on a digital camera.

These optical elements may be provided with an optical thin film such as an antireflection film, a total reflection film, a partial reflection film, or a film having spectral characteristics, if necessary.
Moreover, in the optical element manufacturing method described above, a press material for precision press molding that produces a final product by press molding the preform manufactured by the preform molding apparatus and the preform manufacturing method according to the present embodiment. However, it can also be used as a stamping and processing material when manufacturing optical elements by grinding and polishing the surface of the molded product obtained by press molding to finish it into the final product. it can.

As described above, according to the method for manufacturing a precision press-molding glass preform and the method for manufacturing an optical element according to this embodiment, the molten glass lump supplied to the mold 104 of the preform molding apparatus 100 is blown. By rotating by a spiral air current (spiral air) ejected from the nozzle 210, the attitude of the molten glass lump floating in the mold 104 can be stabilized and corrected. This makes it possible to adjust the curvature of the upper surface of the preform while correcting and holding the position of the preform floating in the mold so that the center of curvature coincides with the center of the outer periphery of the preform.
In addition, since the position and posture of the molten glass lump in the mold can be stabilized and corrected from above the mold 104 by air blowing means independent of the mold 104, the mold itself is changed or improved. There is no need, and it is possible to realize preform position control and position correction with a simple structure without making the mold complicated. Therefore, the manufacturing cost of the preform molding apparatus 100 does not increase, and it is possible to provide a preform molding apparatus that can be easily applied to existing apparatuses and has excellent versatility and expandability.

Moreover, in this embodiment, when the molten glass lump (preform) rotates in the shaping | molding die 104 with the spiral air from the ventilation nozzle 210, when a molten glass lump shakes to a specific direction by the movement of the shaping | molding die 104. However, the force due to the shaking does not work only in one direction of the molten glass lump, and the roundness of the outer periphery of the preform can be increased.
As a result, it is possible to mold and manufacture a preform with no roundness and high roundness, prevent uneven thickness from occurring during the press molding of the next process, and to mold and manufacture a highly accurate optical element. It becomes possible.

Moreover, in this embodiment, a negative pressure is generated inside the air flow by ejecting spiral air from the blow nozzle 210, and the upper surface of the molten glass lump can be sucked by this negative pressure, thereby the molten glass lump. The curvature of the upper surface can be controlled. In particular, since a suction force due to negative pressure is applied, the center of the upper surface of the preform can be bulged and formed into a top shape to control the curvature.
As a result, it is possible to perform the curvature control by rotating and melting the molten glass lump with the center of curvature as the center of rotation by a spiral air flow, and suctioning and expanding the center of curvature with a negative pressure. The curvature of the upper surface of the preform can be adjusted so that the center of the outer periphery of the reform coincides, and a more accurate preform molding can be realized.

Furthermore, the blower nozzle 210 according to the present embodiment can eject a vertically downward airflow (center air) from the center nozzle 211 onto the upper surface of the molten glass lump by air blow control different from the spiral airflow.
By blowing center air from the blower nozzle 210, the upper surface of the molten glass lump can be directly pressurized, and the curvature of the upper surface of the molten glass lump can be controlled by the action of this air pressurization. In particular, since pressurization is performed by a vertically downward airflow, the center of the upper surface of the preform can be flattened or formed to be recessed in a concave shape.
Moreover, by blowing center air over the entire upper surface of the molten glass lump, the molten glass lump is cooled and the occurrence of striae can be prevented.

In this way, according to the present embodiment, spiral air is ejected from the blow nozzle 210 to rotate the molten glass lump with the center of curvature as the center of rotation, and the center of curvature is pressurized and cooled vertically by the center air. By doing so, the curvature of the preform can be controlled.
Thereby, the curvature of the upper surface of the preform can be adjusted so that the center of curvature coincides with the center of the outer periphery of the preform, and more accurate preform molding can be realized.

  As mentioned above, although the manufacturing method of the glass preform for precision press molding of this invention and one embodiment of the manufacturing method of an optical element were demonstrated, the manufacturing method of the glass preform for precision press molding which concerns on this invention, and the manufacturing method of an optical element It is needless to say that the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention.

  For example, in the above-described embodiment, the first air outlet 210a that blows the airflow downward in the vertical direction is formed at the center by adopting a double structure including two cylindrical bodies of the center nozzle 211 and the exterior material 213. The blower nozzle 210 provided around the first blowout port 210a and provided with the second blowout port 210b that blows out the airflow spirally is provided at the peripheral portion. Is not limited, as long as the vertically downward airflow (center air) and the spiral airflow (spiral air) can be ejected by another system of air blow control.

  The present invention relates to the manufacture of a precision press-molding glass preform for press-molding a molded glass preform for separating a glass lump of a constant weight from molten glass and forming it into a glass preform for precision press-molding. It can utilize suitably for manufacture of the optical element by.

DESCRIPTION OF SYMBOLS 100 Preform molding apparatus 102 Molten glass supply part 104 Mold 106 Turntable 108 Mold transfer part 110 Mold raising / lowering part 200 Blower 210 Blower nozzle 211 Center nozzle 212 Exterior material 213 Guide groove

Claims (6)

A method for producing a precision press-molding glass preform that sequentially supplies molten glass that has flowed out of an outflow pipe into a predetermined amount of molten glass lump and supplies it to a plurality of circulating molds to form a preform,
A blower nozzle is installed at a predetermined position on the moving path of the mold, and when the mold that holds the molten glass lump is floated, the blower nozzle spirals from the blower nozzle. Blowing the airflow blown into the periphery of the molten glass lump, giving the molten glass lump a force rotating around an axis along the vertical direction, and forming the molten glass lump on the moving mold A method for producing a glass preform for precision press molding.   The airflow is blown out from the peripheral portion of the air blowing nozzle to generate a negative pressure in the atmosphere inside the airflow, thereby sucking the upper surface of the molten glass lump and controlling the curvature of the upper surface. The manufacturing method of the glass preform for precision press molding of 1.   A flow of air is blown vertically downward from a central portion of the blow nozzle, and the air flow is blown to the center of the molten glass lump to pressurize the upper surface of the molten glass lump to control the curvature of the upper surface. The manufacturing method of the glass preform for precision press molding as described in any one of 1 or 2.   A first air outlet is provided in the central portion of the air blowing nozzle to blow out the air current downward in the vertical direction, and the air current is blown out in a spiral manner around the first air outlet in the peripheral portion of the air blowing nozzle. The manufacturing method of the glass preform for precision press molding as described in any one of Claims 1-3 which provided the 2nd blowing outlet. A predetermined gap is formed between the center nozzle having an opening serving as the first blow-off port and an outer surface in the vicinity of the opening of the center nozzle so that one end side of the blowing nozzle is in contact with the center nozzle. And a cylindrical exterior material mounted so that
A plurality of guide grooves are spirally engraved at the interface where the outer surface in the vicinity of the opening of the center nozzle and the inner surface on one end side of the exterior material are abutted, and the guide grooves are The manufacturing method of the glass preform for precision press molding of Claim 4 which made it open around the blower outlet and formed said 2nd blower outlet. A method for producing an optical element, wherein a glass preform is produced by the method for producing a glass preform for precision press molding according to any one of claims 1 to 5, and an optical element is produced by press-molding the glass preform. .

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