JP7128173B2 - Thermoforming jig and thermoforming apparatus using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a thermoforming jig and a thermoforming apparatus using the same, and more particularly to a thermoforming jig and a thermoforming apparatus for thermoforming a quartz glass ingot to form a quartz glass compact having a predetermined shape. It is.

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 produced by, for example, hydrolyzing a silica raw material such as silicon tetrachloride using oxygen and hydrogen to deposit glass fine particles on a target.

Patent Document 1 proposes a molding die (heat molding jig) used in a method of heating the quartz glass ingot to form the softened quartz glass into a predetermined shape. This proposed molding die is a molding die for heat-molding a quartz glass ingot in an upright state, and the quartz glass ingot is placed in the molding die and softened by heating the quartz glass ingot. Quartz glass is formed into a predetermined shape.

Specifically, as schematically shown in FIG. 7A, a molding portion 51 having an internal shape (inner peripheral surface shape) corresponding to the shapes of the bottom surface and the outer peripheral surface of the quartz glass molded body, and the molding portion A supporting portion 52 is provided above 51 and supports the outer peripheral surface of the quartz glass ingot X with its cylindrical inner peripheral surface.

As described above, in the molding die described in Patent Document 1, since the support portion 52 supports the outer peripheral surface of the quartz glass ingot X, the support portion 52 is in contact with the outer peripheral surface of the quartz glass ingot X. As the heat softening progresses, the outer peripheral surface of the quartz glass ingot X slides on the inner peripheral surface of the supporting portion, and finally, as shown in the transition states of FIGS. Contained and molded.

JP 2015-120619 A

As shown in FIG. 7(a), a large number of layered striae C remain along the growth surface of the columnar quartz glass ingot X produced by the above-described method. When the quartz glass ingot X in which such layered striae C remain is heated and softened in the molding die 51, the quartz glass ingot X is deformed so as to flow downward from the outer periphery as described above, as shown in FIGS. It gradually becomes horizontally long as shown in (c).

However, when the quartz glass molded body formed in the molding die 51 is heated and softened, the veins at the lower part of the quartz glass molded body appear at the outer peripheral portion where the glass flow distance is the longest, as shown in FIG. 7(b). C bends in the vertical direction due to the frictional force of the bottom plate. Then, as shown in FIG. 7(c), the quartz glass molded body has a bent portion, so that the optical characteristics become non-uniform and there is a problem that it is not suitable for optical applications. FIG. 8 shows an enlarged view (cross-sectional view) of the bent striae C. Such striae are hereinafter referred to as bent striae C1.

The inventors of the present application have extensively studied this bending striae, and found that, in the process of softening and deforming a silica glass ingot by heating, horizontal deformation is suppressed by friction between the bottom of the ingot and the bottom of the molding die. The inventors have found that the deformation speed in the vertical direction is faster than the deformation speed in the horizontal direction, and as a result, bending striae are generated, leading to the present invention.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermoforming jig capable of forming a quartz glass compact formed by heating, softening and deforming a quartz glass ingot in a molding die without causing bending striae. It is an object of the present invention to provide a thermoforming apparatus that is easy to use.

A thermoforming jig according to the present invention, which has been devised to solve the above-mentioned problems, has a bottom surface and a side surface, and comprises a molding tray for forming a quartz glass compact having a predetermined shape from a quartz glass ingot, and the molding tray. a mounting table disposed on a bottom surface and on which the quartz glass ingot is mounted; a first support disposed on the top of the molding tray and surrounding the quartz glass ingot; and the first support. a cylindrical second support that is arranged on the upper part of the body and stores the quartz glass ingot therein, wherein the mounting table on which the quartz glass ingot is placed has an inclined surface on the periphery thereof; is formed. Moreover, it is desirable that the inclination angle of the inclined surface formed on the mounting table with respect to the lower end surface of the quartz glass ingot is 30° or more and less than 90°. A lower end surface of the quartz glass ingot may be partially positioned above the inclined surface while the quartz glass ingot is placed on the mounting table.

Further, a thermoforming apparatus according to the present invention, which has been made to solve the above problems, includes the thermoforming jig, a heating furnace that accommodates the thermoforming jig, and a quartz glass ingot that is accommodated in the heating furnace. and a heater for heating.

INDUSTRIAL APPLICABILITY According to the present invention, in a quartz glass molded body obtained by heating and softening a quartz glass ingot and deforming it in a molding die, a quartz glass ingot with suppressed bending striae can be obtained. It is possible to provide a thermoforming apparatus used.

FIG. 1 is a cross-sectional view showing a schematic configuration of a thermoforming jig and 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 thermoforming jig according to the present invention. FIG. 4 is a partially enlarged side view of the heating molding jig of FIG. 3 and the quartz glass ingot placed thereon. FIG. 5 is a perspective view showing a modification of the thermoforming jig according to the present invention. 6(a) and 6(b) are cross-sectional views showing the state of a quartz glass ingot deformed by heating. 7(a), (b), and (c) are cross-sectional views showing the state of deformation of a quartz glass ingot in a conventional thermoforming jig. FIG. 3 is a cross-sectional view in which an end face of a quartz glass molded body is partially enlarged;

An embodiment according to the present invention will be described below with reference to FIGS. 1 to 6. FIG. 1 to 6 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. 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 manufactured by, for example, hydrolyzing a silica raw material such as silicon tetrachloride and depositing glass fine particles on a target. The portion X2 is formed in a curved surface shape whose diameter gradually increases or in a slope 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, an upper end portion having a curved or sloped convex shape, and a lower end portion having a horizontal surface. As shown in FIG. 1, the mounting table 10 is arranged on the bottom surface P1 of the tray P, and the lower end surface (bottom surface) X3 is mounted on the upper surface thereof. The lower end surface X3 is formed in a strictly horizontal plane to the extent that the flatness required for a quartz glass compact can be obtained.

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 mounting table 10. As shown in FIG. Moreover, FIG. 4 is the side view which expanded a part of mounting base of FIG.

The thermoforming jig 3 roughly comprises a molding tray P, first supports 5 (5A and 5B) placed on the upper edge of the molding tray P, and and a mounting table 10 disposed on the bottom surface of the molding tray P.

The first support 5 supports the second support 6, is placed on the upper edge of the molding tray P, and surrounds the quartz glass ingot X. As shown in FIG. The first support 5 is a pair of first beams 5A spaced apart by a distance equal to or greater than the diameter of the quartz glass ingot X, and perpendicular to the first beams 5A spaced apart by a distance equal to or greater than the diameter of the quartz glass ingot X. A pair of second beams 5B are assembled in a parallel cross shape. The second support 6 is formed in a cylindrical shape and placed on top of the first support 5, and the quartz glass ingot X is accommodated inside the second support 6. be.

The molding tray P is a mold for molding a quartz glass molded body having a predetermined shape from the quartz glass ingot X. The molding tray P has a tray bottom portion P1 and a side portion P2, and in plan view, For example, as shown in FIG. 2, it is formed in a rectangular shape. This molding tray P is basically a mold that defines the shape of the quartz glass molded body after molding. A mold is formed.

Specifically, when the quartz glass ingot X is placed on the mounting table 10 and the quartz glass ingot X is heated and softened (when the diameter is expanded), the quartz glass molded body is formed on the upper surface of the mounting table 10 and the side surface of the receiving plate P2. is molded by

As shown in FIG. 3, the mounting table 10 is a flat rectangular plate as a whole, and has a flat upper surface 10a and inclined surfaces 10b formed on the four sides of the periphery thereof. Here, as shown in FIG. 3, the circular lower end surface X3 of the quartz glass ingot X is not entirely in contact with the upper surface 10a of the mounting table 10, but the outer peripheral portion of the lower end surface X3 partially contacts the inclined surface 10b of the mounting table 10. It shows a state in which it is placed in a state of protruding upward (floating state).

As shown in FIG. 4, the diameter at the bottom of the quartz glass ingot X is L, the radial length of the projection above the inclined surface 10b on the lower end surface X3 of the quartz glass ingot X (the tangent line between the quartz glass ingot X and the inclined surface 10b) ) is d1, the radial length parallel to the lower end surface X3 of the inclined surface 10b is d2, and the radial length from the outer peripheral end of the mounting table 10 to the side surface P2 of the tray P is Let d3 be the inclination angle of the inclined surface 10b with respect to the lower end surface X3. Preferred aspects of these parameters will be described later.

Although FIG. 3 shows an example in which the upper surface 10a of the mounting table 10 has a rectangular shape, the present invention is not particularly limited to this. It may be shaped. Further, the material of the molding tray P and the mounting table 10 is not particularly limited as long as it is a material that hardly reacts with quartz glass and has heat resistance. For example, a high-purity carbon material is preferably used.

By the way, if the shape of the inclined surface 10b as shown in FIG. 4 has one or more steps having a vertex, there is a possibility that air bubbles may be caught in the deformed glass at the vertex. In the present invention, FIG.
A linear shape as shown in is preferred. Alternatively, a gentle curve shape may be used, and θ in that case is determined by the angle formed by the straight line connecting the start point and the end point of the curve and the upper surface 10a.

Moreover, the surface roughness of the inclined surface 10b is preferably smooth enough to allow the heat-softened quartz glass to move smoothly.

Next, the operation of the thermoforming jig and the thermoforming apparatus according to the present invention will be described. First, the quartz glass ingot X is placed on the molding tray P so that the center of the quartz glass ingot X is positioned at the center (the center of the top surface 10a) of the mounting table 10 arranged on the bottom surface of the molding tray P. .

The striae C can be observed by a known method, and the projection method and the Schlieren method are preferably used. Further, as shown in FIG. 8, the bending striae C1 in the present invention means that the striae extending in one direction from the central portion when the end face of the quartz glass molded body is observed as shown in FIG. longitudinal direction). In particular, a shape in which the rounded portion is close to 90° can be said to be a typical aspect.

Subsequently, a pair of first beams 5A are arranged on the upper edge of the molding tray P with a gap equal to or larger than the diameter of the quartz glass ingot X. As shown in FIG. Furthermore, the second beam 5B is arranged orthogonally to the first beam 5A with an interval equal to or larger than the diameter of the quartz glass ingot X. Then, considering the height of the quartz glass ingot X, the first support 5 is formed by assembling the first beam 5A and the second beam 5B in a parallel cross shape.

Subsequently, the second support 6 is lowered from above the quartz glass ingot X so that the center of the second support 6 coincides with the center of the quartz glass ingot X, and the quartz glass ingot X is accommodated therein. . This second support 6 rests on the first support 5 . Then, it is confirmed whether or not the center of the second support 6 and the center of the quartz glass ingot X are on the same straight line. If the two are not on the same straight line, the placement position of the second support 6 is shifted and the center of the second support 6 and the center of the quartz glass ingot X are aligned.

After setting the quartz glass ingot X on the heat forming jig, the quartz glass ingot X is heated by the heater 4 shown in FIG. 1 to be softened. As a result of this heating, the diameter of the silica glass ingot X gradually expands from the bottom as shown in FIG. Along with this, the height dimension of the quartz glass ingot X is reduced. At this time, since the lower end surface X3 of the quartz glass ingot X deforms along the inclined surface 10b of the mounting table 10, the quartz glass ingot X is deformed along a horizontal surface without the inclined surface 10b. Friction received by the lower end surface X3 of X is reduced, and it is possible to prevent the outer ends of the striae present in the upper portion of the quartz glass ingot X from changing too quickly in the vertical direction. As a result, it is possible to effectively prevent bending striae that occur due to bending at the ends of the striae.

Then, as shown in FIG. 6(b), the entire quartz glass ingot X is moved into the molding tray P and accommodated therein, and then cooled to produce a quartz glass compact. Then, by horizontally cutting and removing the bottom portion of the quartz glass molded body, a shape that can be processed as a product is obtained.

Preferred embodiments of the present invention are described below. First, with respect to d1, since L of the quartz glass ingot X differs slightly for each product, it is unrealistic to individually design the mounting table 10 to set the value of d1 to zero or constant for each product. . In the present invention, even if d1 exists, it can be said that the effect of the present invention can be sufficiently obtained as long as the value is not extremely large.

When d1 exists in the negative direction, that is, when L of the quartz glass ingot X is smaller than the outer diameter of the top surface 10a, there exists a distance for the bottom portion of the softened quartz glass ingot X to move in contact with the top surface 10a. , the effect of the present invention is offset by that amount, so it cannot be said to be very preferable.

On the other hand, when d1 exists in the positive direction, that is, when L of the quartz glass ingot X is larger than the outer diameter of the upper surface 10a, the contact area with the upper surface 10a decreases when the quartz glass ingot X deforms, resulting in less friction. As compared to when d1 is zero or negative, the effect of the present invention is less impaired. However, there is a risk that the quartz glass ingot X may lack stability when placed or in a softened state, and it is not guaranteed that the softening and descent of the quartz glass ingot X progress evenly at all points around the circumference of the quartz glass ingot X. This is also not desirable.

Considering the above, it is preferable that the absolute value of d1 does not exceed 0.5 times L or is 100 mm or less, since it is possible to prevent occurrence of conspicuous defects in practical use.

θ is preferably 30° or more and less than 90°. If θ is less than 30°, the effect of reducing bending of striae as described above cannot be sufficiently obtained. On the other hand, if θ is set to 90° (perpendicular), the softened quartz glass ingot X may drop rapidly, resulting in excessive deformation. More preferably, θ is 45° or more and 75° or less.

If d3 is too large, the recessed shape at the bottom of the quartz glass molded body after completion of molding becomes excessively large, and the amount to be removed is too large, resulting in a decrease in the portion obtained as a product, which is not preferable. Preferably, d3 is in the range of 1/10 to 1/6 of the length of the molding pan P piece.

Further, when the molding tray P and the mounting table 10 are designed so that θ is 45°, the length of one piece of the molding tray P is 8, L is 4, and d3 is 1, the quartz glass ingot X is Since the degree of deformation is optimized, the effects of the present invention are exhibited most effectively, which is particularly preferable.

As described above, in the heat molding jig and the heat molding apparatus according to the present invention, the quartz glass ingot X is mounted on the mounting table 10 having the inclined surface 10b at the peripheral edge, so that the heat is applied to the quartz glass ingot X. Since friction in the horizontal direction is reduced during deformation, it is possible to prevent or reduce the occurrence of bending striae.

The thermoforming jig and thermoforming apparatus according to the present invention will be further described based on examples.

(common conditions)
A quartz glass ingot X having a bottom diameter of 400 mm, a height of 900 mm and a weight of about 200 kg was produced by a known oxyhydrogen flame melting method using silicon tetrachloride, hydrogen gas and oxygen gas. Next, using a thermoforming apparatus as shown in FIG. 1 and a thermoforming jig as shown in FIG. After allowing to cool, a quartz glass molded body of about 800 mm square was obtained. The bending striae were observed by the projection method.

(Example 1)
Using the mounting table 10 as shown in FIG. 4, the length ratio of L of the synthetic quartz glass ingot X and the length d3 of one piece of the molding tray P was set to 4:8:1. Here, θ is set to 45°. As shown in FIG. 6 , the quartz glass molded body after heating and melting had a recessed portion extending downward by 30 mm along the outer peripheral portion following the shape of the mounting table 10 . Next, the concave portion was cut to obtain a square block with a thickness of 120 mm. Curvature striae were not found in the square blocks, but were found in the upper part of the concave portion.

(Example 2)
The same procedure as in Example 1 was performed except that θ was set to 60° and the value of d1 was changed accordingly. The quartz glass molded body after heating and melting had a recessed portion following the shape of the mounting table 10, as in the first embodiment. No curved striae were found in the square blocks, but were found in the middle of the concave portion.

(Example 3)
The same procedure as in Example 1 was performed except that θ was set to 75° and the value of d1 was changed accordingly. The quartz glass molded body after heating and melting had a recessed portion following the shape of the mounting table 10, as in the first embodiment. Curvature striae were not found in the square blocks, but were found in the lower part of the concave portion.

(Comparative example 1)
A synthetic quartz glass ingot X was placed on a flat plate as shown in FIG. 7 without using a mounting table 10 as shown in FIG. At that time, the length of the flat plate in the longitudinal direction was doubled with d3 being the same as in Example 1. Other conditions were the same as in Example 1. As a result, it was confirmed that the lower part became a flat quartz glass molded body, and bending striae were confirmed in the outer peripheral part.

(Comparative example 2)
The same procedure as in Example 1 was performed except that θ was set to 15° and the value of d1 was changed accordingly. As a result, bent striae were confirmed in the square block, but not in the concave portion.

(Comparative Example 3)
Experiments were conducted in the same manner as in Example 1, except that θ was set to 90° and the value of d1 was changed accordingly. As a result, air bubbles were generated in the quartz glass molded body due to the clearance between the bottom plate of the quartz glass molded body and the mounting table 10 .

As described above, in the quartz glass molded bodies obtained according to the embodiments of the present invention, bending striae (or inclusion of air bubbles) did not occur in the parts used as products. From this, it was confirmed that the present invention can more effectively suppress the occurrence of bending striae, which could not be easily resolved by the conventional method.

REFERENCE SIGNS LIST 1 thermoforming apparatus 2 heating furnace 3 thermoforming jig 4 heater 5 first support 6 second support 10 mounting table 10a upper surface 10b inclined surface C striae C1 curved striae P molding tray X quartz glass ingot L Diameter of quartz glass ingot X

Claims (3)

a molding tray having a bottom surface and side surfaces for forming a quartz glass molded body having a predetermined shape from a quartz glass ingot;
a mounting table disposed on the bottom surface of the molding tray and on which the quartz glass ingot is mounted;
a first support positioned above the molding pan and surrounding the quartz glass ingot;
a cylindrical second support disposed above the first support and containing the quartz glass ingot therein;
A heating and molding jig, wherein an inclined surface is formed on the peripheral edge of the mounting table on which the quartz glass ingot is mounted. 2. The thermoforming jig according to claim 1, wherein the inclination angle of the inclined surface formed on the mounting table with respect to the lower end surface of the quartz glass ingot is 30[deg.] or more and less than 90[deg.]. a thermoforming jig according to claim 1 or claim 2;
a heating furnace that houses the thermoforming jig;
a heater that is housed in the heating furnace and heats the quartz glass ingot;
A thermoforming apparatus characterized by comprising at least

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