JP7141997B2 - Thermoforming apparatus and method for manufacturing quartz glass molded body using same - Google Patents

Description

The present invention relates to a thermoforming apparatus and a method for manufacturing a quartz glass molded body using the same , and more particularly to a thermoforming apparatus for thermoforming a quartz glass ingot to form a cylindrical quartz glass molded body. and a method for producing a quartz glass molded body using the same.

As one method for producing a synthetic quartz glass body suitable for optical applications, an ingot of synthetic quartz glass is produced, then the quartz glass ingot is heated at a predetermined temperature to be softened, and a mold having a predetermined shape is used to soften the ingot. Molding manufacturing methods are known. The quartz glass ingot is manufactured by a gas phase reaction method, for example, by hydrolyzing a silica raw material such as silicon tetrachloride and depositing glass microparticles on a target.

For example, when it is desired to obtain a cylindrical quartz glass compact using the quartz glass ingot, conventionally, the quartz glass ingot is first heated and melted to a desired diameter and thickness, and then machined from the center in the radial direction. A method of forming a quartz glass compact having a predetermined inner diameter by mechanically grinding is known. However, in the method of mechanically grinding a columnar quartz glass ingot, the grinding process takes a long time and a large amount of ground glass powder is produced, resulting in material loss and processing costs. There was a problem that an increase occurred.

In order to address such a problem, in Patent Document 1, when the glass material 60 is heated and melted as shown in FIG. 2, a method is disclosed in which a molded body 61, which is a glass material after heating and melting, is formed into a columnar shape (a shape close to a cylindrical shape) with a concave central portion. As shown in FIG. 7(b), after obtaining a columnar molded body 61 with a recessed central portion, the lower part (the portion surrounded by the dashed line) is removed by cutting in the next step, as shown in FIG. 7(c). and molded into a cylindrical shape. According to such a method, the time and amount of grinding can be greatly reduced, the efficiency can be improved, and the cost can be reduced.

JP 2010-100493 A

By the way, in the glass molded body 61 formed by the method disclosed in Patent Document 1, the lower part is cut to form a cylindrical shape. However, fine unevenness exists on the lower surface of the molded body after being cut. When such unevenness exists, there is a possibility that processing distortion due to the unevenness occurs even when polishing is performed in a post-process.

In addition, in the method disclosed in Patent Document 1, the glass material is not wasted and the cost can be reduced compared to the method of grinding and removing the entire hollow portion of the cylinder. The problem remains that the wasted glass material cannot be completely eliminated for removal. In addition, there is a possibility that the center line may be shifted when the pressing jig 51 is used to press the central portion of the glass material 60 to form a recess (hole).

The present invention has been made to solve the above-mentioned problems, and its object is to obtain a cylindrical glass molded body free from processing distortion by heating and deforming a quartz glass ingot in a molding die. It is an object of the present invention to provide a thermal molding apparatus capable of reducing molding costs by eliminating material waste, and a method for producing a quartz glass molded body using the apparatus.

A thermoforming apparatus according to the present invention, which has been devised to solve the above-described problems, is a thermoforming apparatus for forming a cylindrical quartz glass compact from a quartz glass ingot having a cylindrical or prismatic shape and having at least a flat lower end portion. The thermoforming apparatus includes at least a thermoforming jig, a heating furnace that accommodates the thermoforming jig, and a heater that is accommodated in the heating furnace and heats the quartz glass ingot. The jig includes a molding tray having a bottom surface and side surfaces, and a cylindrical core disposed on the bottom surface of the molding tray and forming a cylindrical quartz glass compact from a quartz glass ingot together with the bottom surface and side surfaces. An annular inclined surface is formed on the peripheral edge of the top surface of the core on which the flat surface of the quartz glass ingot is placed, and the inclined surface of the inclined surface with respect to the top surface of the core has an inclination angle θ1 is larger than the inclination angle θ2 of the inclined surface with respect to the outer peripheral side surface of the core, θ1 is 45° or more and 60° or less, and θ2 is 15° or more and 45° or less. be.

In the thermoforming apparatus configured as described above, the quartz glass ingot is heated and melted after being placed on the core, and is deformed in the thermoforming jig by its own weight to form a cylindrical glass. you get a body Since the glass molded body obtained in this way is formed only by heating and melting from a quartz glass ingot, it occurs when a hole (recess) is made by applying a load to a conventional jig. There is no centerline deviation. Moreover, since a mechanical cutting process is not required, it is possible to prevent the occurrence of processing strain, and since no wasteful glass material is generated, the cost can be reduced.

Further, in the method for producing a quartz glass molded body according to the present invention, which has been made to solve the above-mentioned problems, a columnar or angular shape is provided on the top surface of the core of the heat-forming jig housed in the heating furnace. The method includes the steps of: placing a silica glass ingot having a columnar shape and having at least a flat lower end; and heating and melting the silica glass ingot with the heater.

According to the present invention, a quartz glass ingot can be heat-deformed in a molding die to obtain a cylindrical glass molded body without processing distortion, and the cost of molding can be reduced by eliminating waste of materials. It is possible to provide a thermoforming apparatus that can

FIG. 1 is a cross-sectional view showing a schematic configuration of a thermoforming apparatus according to the present invention. 2 is a plan view of a thermoforming jig provided in the thermoforming apparatus of FIG. 1. FIG. FIG. 3 is a perspective view of a core included in a thermoforming jig. 4 is a partially enlarged sectional view of the core of FIG. 3. FIG. 5(a) and 5(b) are cross-sectional views showing the state of a quartz glass ingot deformed by heating. 6 is a perspective view of a quartz glass molded body obtained by the heat molding apparatus of FIG. 1. FIG. 7(a), (b), and (c) are cross-sectional views showing an example of manufacturing a cylindrical quartz glass molded body in a conventional thermoforming apparatus.

An embodiment according to the present invention will be described below with reference to FIGS. 1 to 5. FIG. 1 to 5 schematically show the shapes of the device and the jig for explanation.

FIG. 1 is a diagram showing a schematic configuration of a thermoforming apparatus 1. The thermoforming apparatus 1 includes at least a heating furnace 2, a thermoforming jig 3, and a heater 4 for heating a quartz glass ingot X. I have it. The heating furnace 2 accommodates a heater 4 therein, and heats the quartz glass ingot X with heat generated by the heater 4 . The heat molding jig 3 is a jig for forming a quartz glass compact having a predetermined shape while heating and softening the quartz glass ingot X, as will be described in detail later.

The quartz glass ingot X is produced, for example, by hydrolyzing a silica raw material such as silicon tetrachloride and depositing glass fine particles on a target. The upper end portion X2 is formed on a flat surface as shown. Alternatively, the upper end portion X2 may be formed in a curved shape with a gradually increasing diameter, or in a sloped shape. Further, the lower end surface X3 is formed as a flat surface.

That is, the quartz glass ingot X has a cylindrical or prismatic shape, and has, for example, a flat surface (not limited to a horizontal surface) at the upper end and a horizontal surface at the lower end. As shown in FIG. 1, a core 10 is arranged at the center of the bottom surface portion P1 of the saucer P, and the lower end surface (bottom surface) X3 of the quartz glass ingot X is placed on the upper surface thereof. The lower end surface X3 has a strictly horizontal surface.

Next, the configuration of the thermoforming jig 3 housed in the thermoforming apparatus 1 will be described with reference to FIGS. 1 to 4. FIG. 2 is a plan view of the thermoforming jig 3, and FIG. 3 is a perspective view of the core 10. As shown in FIG. 4 is a cross-sectional view enlarging a part of the mounting table in FIG.

The thermoforming jig 3 is mainly composed of a molding tray P and a core 10 arranged on the bottom surface of the molding tray P. As shown in FIG. The molding tray P has a tray bottom portion P1 and a side portion P2, and is formed in a circular shape in a plan view, for example, as shown in FIG. With the silica glass ingot X placed on the core 10 as shown in FIG. 1, the side surface portion P2 surrounds the silica glass ingot X.

The thermoforming jig 3 is a mold that defines the shape of quartz glass after molding, and the mold is formed by the outer peripheral surface 10a of the core 10, the bottom surface portion P1, and the side surface portion P2. Specifically, by placing the quartz glass ingot X on the core 10 and heating and softening the quartz glass ingot X, a gap between the outer peripheral surface 10a of the core 10 and the tray bottom portion P1 and the side surface portion P2 is formed. The softened quartz glass enters and is molded.

As shown in FIG. 3, the core 10 has a substantially cylindrical shape as a whole, and has a body portion 10A having the outer peripheral side surface 10a, an upper end portion 10B having a top surface 10b, and a lower end portion 10C having a lower surface 10c. is doing. The outer peripheral side surface 10a of the body portion 10A has, for example, a circular cross-sectional shape in the horizontal direction, and is formed by a surface orthogonal to the horizontal plane in the vertical direction. The lower surface 10c of the lower end portion 10C is formed in a horizontal plane, and the outer peripheral side surface 10a is arranged vertically with the core 10 standing upright.

FIG. 4 is an enlarged cross-sectional view of the upper end portion 10B that is part of the mounting table in FIG. That is, the annular inclined surface 10d formed on the peripheral edge of the upper end portion 10B has an inclination angle θ1 with respect to the top surface 10b of the core 10 and an inclination angle θ2 with respect to the outer peripheral side surface 10a of the core 10. have.

If the core 10 is a perfect cylinder without the inclined surface 10d, the surface tension of the softened silica glass will cause the core 10 to move, especially when a thin cylindrical silica glass compact with a narrow width is produced. flow between the outer peripheral surface 10a and the bottom surface portion P1 of the thermoforming jig 3 cannot be created. Therefore, with such a core 10, it has been difficult to manufacture a hollow quartz glass compact using only its own weight.

θ1 is slightly increased so that the quartz glass ingot X in which the core 10 is heated and melted deforms and bites smoothly. Also, θ2 is set slightly small so that the core 10 can pass through the quartz glass ingot X completely and move smoothly without causing burrs or bulges. In the present invention, θ1>θ2 is set in order to sufficiently exhibit these effects.

Furthermore, the inclination angle θ1 is set to be 45° or more and 60° or less, and the inclination angle θ2 of the inclined surface 10d with respect to the outer peripheral side surface 10a is set to be 15° or more and 45° or less.

In the present invention, it can be said that .theta.1 exhibits the effect of accelerating the deformation of quartz glass, and .theta.2 exhibits the effect of smooth flow of the softened quartz glass. Therefore, not only by setting θ1>θ2 but also by setting such a numerical range, the effect can be exhibited more effectively.

If θ1 is less than 45°, it is difficult for the softened quartz glass to flow between the outer peripheral surface 10a, the saucer bottom portion P1, and the side surface portion P2. There is concern that microbubble aggregates) may occur. On the other hand, if θ1 exceeds 60°, the flow speed of the softened quartz glass is too high, so that the shaping does not proceed evenly particularly in the circumferential direction, and the shape may become unstable.

If θ2 is less than 15°, the flow rate of the softened quartz glass is too high, which hinders molding. On the other hand, if θ2 exceeds 45°, the flow of the softened quartz glass becomes abrupt and does not flow uniformly.

In addition, the dimension d1 from the terminal end of the top surface 20b to the outer peripheral side surface 10a along the radial direction and the dimension d2 from the upper end of the outer peripheral side surface 10a to the top surface 10b along the vertical direction shown in FIG. However, the present invention can be made more preferable by setting d1 and d2 within appropriate ranges.

It is more preferable that the value of d1 is in the range of 1 to 10% when the outer diameter of the core 10 is taken as 1. If it is too small, the effects of the present invention cannot be obtained, but if it is too large, there is a concern that the stability of placing the quartz glass ingot X on the top surface 10b will be impaired.

Since θ1>θ2, d1<d2 from the right triangle theorem. Furthermore, since θ1 is 45° or more and 60° or less and θ2 is 15° or more and 45° or less, d2 is uniquely determined if θ1 (or θ2) and d1 are given.

Further, when the diameter of the lower end surface X3 of the quartz glass ingot X is D1, the diameter of the upper surface 10b of the core 10 is D2, and the diameter of the lower surface 10c of the core 10 is D3, the size of the quartz glass ingot X is Therefore, optimizing these parameters is more favorable.

That is, it is preferable that D2 is at least 50% or more of D1 because stability can be ensured when the quartz glass ingot X is placed on the top surface 10b. Also, when the value of D1-D3 is less than 20 mm, the gap into which the softened quartz glass flows is small, and the softened quartz glass hardly flows between the outer peripheral surface 10a and the saucer bottom portion P1 and side portion P2, which is preferable. I can't say

By the way, when it is desired to obtain a silica glass molded body XA that is long in the axial direction, it is possible to some extent by increasing the depth of the molding tray P (the height of the side surface portion P2) and the height of the core 10. . However, since the present invention is an invention using the flow of softened quartz glass, it can be said that it is suitable for manufacturing a thick cylindrical body (annular body) rather than a so-called thin and elongated tubular body. It is not preferable to raise the side part P2. For example, when the quartz glass compact XA has an outer diameter of D4 and an axial length of L, D4/L is more preferably 0.3 or more and 1.8 or less.

When the quartz glass ingot X is heated and melted, the deformation of the quartz glass ingot X is accelerated by forming the heat molding jig 3 in such a shape. A shaped quartz glass compact XA is obtained. The quartz glass molded body XA obtained in this way is formed only by heating and melting the quartz glass ingot X, so that the conventional method of making a hole by applying a load to a jig causes a crack. There is no centerline deviation. Moreover, since a mechanical cutting process is not required, it is possible to prevent the occurrence of machining strain.

The material of the molding tray P and the core 10 is not particularly limited as long as it does not easily react with quartz glass and has heat resistance. For example, a material such as high-purity carbon can be suitably used as the material of the molding tray P and the core 10 . Moreover, these surfaces are preferably smooth enough to allow the softened quartz glass to move smoothly.

Next, the operation of the thermoforming method by the thermoforming apparatus using the thermoforming jig according to the present invention will be described. First, as shown in FIG. 5A, the quartz glass ingot X is placed so that the center of the cylindrical quartz glass ingot X is positioned at the center of the core 10 arranged at the center of the bottom surface of the molding tray P. do.

After setting the quartz glass ingot X on the heat forming jig 3, the quartz glass ingot X is heated and softened by the heater 4 shown in FIG. Due to this heating, the quartz glass ingot X is deformed by its own weight so as to cover the core 10 from the inclined surface 10d of the core 10 along the outer peripheral side surface 10a as shown in FIG. 5(b).

Then, the deformation of the quartz glass ingot X is accelerated, and the core 10 penetrates the quartz glass ingot X smoothly. The molten quartz glass ingot X covers the bottom surface P1 of the saucer without gaps, and is cooled after the upper surface of the molded body becomes horizontal, whereby the quartz glass molded body XA as shown in FIG. 6 is manufactured. The quartz glass molded body XA is then sliced into a required length, washed and inspected to obtain a finished product.

As described above, in the thermoforming apparatus using the thermoforming jig according to the present invention, the quartz glass ingot X is heated and melted after being placed on the core 10, and is thermoformed by its own weight. It is deformed in the jig 3 to obtain a cylindrical glass molded body 10A. The quartz glass molded body XA obtained in this way is formed only by heating and melting the quartz glass ingot X, so that the conventional method of making a hole by applying a load to a jig causes a crack. There is no centerline deviation. Moreover, since a mechanical cutting process is not required, it is possible to prevent the occurrence of processing strain, and since no wasteful glass material is generated, the cost can be reduced.

The thermoforming apparatus according to the present invention and the method for producing a quartz glass molded body using the apparatus will be further described based on examples.

First, a commonly used quartz glass ingot X is prepared. This is synthetic quartz glass obtained by the known method described above, weighs 50 kg, and has a lower end surface X3 with a diameter of 300 mm.

(Example 1)
A carbon molding saucer P having an inner diameter of 500 mm was prepared, and a carbon core 10 having an outer diameter of 470 mm and a height of 150 mm was placed therein so that the center of the molding saucer P coincided. Then, the quartz glass ingot X was placed on the top surface 10 b of the core 10 . Here, the core 10 has d1 of 50 mm and θ1 of 50°. Next, they were placed in an electric furnace and subjected to heat treatment at 2000° C. for 1 hour in the atmosphere. The hollow quartz glass compact XA thus obtained was sliced to obtain a ring plate having an outer diameter of 500 mm and an inner diameter of 470 mm. Furthermore, a highly accurate shape was obtained without any deformation.

(Comparative example 1)
Heat treatment was performed under the same conditions as in Example 1 except that the core 10 was set to θ1=0 (that is, d1=0, no taper processing was performed). It contained a large amount of foam and could not be used as a product.

(Comparative example 2)
Heat treatment was performed under the same conditions as in Example 1, except that θ1 was 80°. I couldn't do it.

REFERENCE SIGNS LIST 1 heat molding device 2 heating furnace 3 heat molding jig 4 heater 10 core 10a outer peripheral side surface 10b top surface 10c lower surface 10d inclined surface P molding tray X quartz glass ingot

Claims (4)

A thermoforming apparatus for forming a cylindrical quartz glass compact from a quartz glass ingot having a cylindrical or prismatic shape and having at least a flat lower end, comprising:
The thermoforming apparatus includes at least a thermoforming jig, a heating furnace that houses the thermoforming jig, and a heater that is housed in the heating furnace and heats the quartz glass ingot,
The thermoforming jig includes a molding tray having a bottom surface and a side surface, and a cylindrical shape disposed on the bottom surface of the molding tray and forming a cylindrical quartz glass molded body from the quartz glass ingot together with the bottom surface and the side surfaces. and a core of
An annular inclined surface is formed on the peripheral edge of the top surface of the core on which the flat surface of the quartz glass ingot is placed. larger than the inclination angle θ2 of the inclined surface with respect to the outer peripheral side surface of the child,
A thermoforming apparatus , wherein θ1 is 45° or more and 60° or less, and θ2 is 15° or more and 45° or less . In the method for manufacturing a quartz glass molded body using the heat molding apparatus according to claim 1 ,
a step of placing a quartz glass ingot having a cylindrical or prismatic shape and having at least a flat lower end portion on the top surface of the core of the heat forming jig housed in the heating furnace;
and a step of heating and melting the quartz glass ingot with the heater. When D1 is the diameter of the lower end surface of the quartz glass ingot, D2 is the diameter of the upper surface of the core, and D3 is the diameter of the lower surface of the core, D2 is 50% or more of D1, and D1-D3 is equal to or greater than D1. 3. A method according to claim 2, characterized in that the value is at least 20 mm. 4. The method according to claim 2 or 3, wherein D4/L is 0.3 or more and 1.8 or less, where D4 is the outer diameter of the quartz glass molded body to be manufactured, and L is the length in the axial direction. A method for producing a quartz glass molded body.

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