JP3778250B2 - Method of forming quartz glass - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for molding quartz glass, which can be molded into a desired shape by reducing entrainment of bubbles when molding quartz glass.
[0002]
[Prior art and problems to be solved by the invention]
Quartz glass is an indispensable material that is indispensable as a material for optical components such as semiconductor photomasks and lenses and mirrors in optical systems. Also, high purity quartz glass is required from the required light transmittance, heat resistance, etc., and the yield of quartz glass obtained at the time of molding is of course important because of the purification of glass raw materials and large-scale manufacturing equipment.
[0003]
The actual shape required is shaped into a square bar or cylinder according to the shape of the photomask, lens, and wafer obtained in the subsequent steps, so the upper or lower part of the glass ingot is also formed flat. Depending on whether or not, the yield is directly involved. Therefore, when molding, if the glass is not melt molded to each corner according to the mold, the upper and lower portions of the glass ingot do not have the desired shape when sliced into the shape of a mask, lens or wafer, thereby reducing the yield. Become.
[0004]
As a method for forming quartz glass, the quartz glass is heated to a temperature higher than the working point, and once melted and formed into a desired shape. In the atmosphere, a carbon or graphite mold material used in the atmosphere, a carbon heater in a furnace, etc. Since oxidative combustion occurs, it is common to seal the inert gas in a vacuum or reduced pressure. In addition, it is necessary to accurately mold along the shape in the mold, and a method of applying pressure as well as heating is known (Japanese Patent Laid-Open No. Sho 56-129621).
[0005]
However, in the conventional method, gas remains between the glass surface and the mold or a graphite or carbon sheet inserted therebetween, and as a result, the glass shape may not be a desired shape along the shape in the mold. .
[0006]
This invention is made | formed in view of the said situation, and it aims at providing the shaping | molding method of quartz glass which can shape | mold into a desired shape with few bubble entrainment.
[0007]
Means for Solving the Problem and Embodiment of the Invention
As a result of intensive studies to achieve the above object, the inventors of the present invention do not have a desired shape around the outer periphery or corner portion of the formed quartz glass. It has been found that the residual gas between the inclusions such as fibers and powders and the quartz glass surface is the cause. And in order to discharge this residual gas, a graphite or carbon mold is fitted with an inclusion such as a breathable carbon or graphite sheet inside if necessary, and quartz glass is put in it and molded. In the above, it has been found that by forming grooves on the entire inner surface of the mold, it is possible to form a desired shape with less entrainment of bubbles, and the present invention has been made.
[0008]
Accordingly, the present invention provides the following method for forming quartz glass.
Claim 1:
Heating the quartz glass in each closed the upper and lower end portions of the tubular body top plate and bottom plate in a graphite or a mold made of carbon is provided, when molded in melt, the inner peripheral surface entire surface of the cylindrical body A plurality of grooves having a depth of 0.5 to 10 mm and a width of 1 to 3 mm are formed continuously from the upper end to the lower end along the vertical direction, and the depths of 0.5 to 10 mm are respectively formed on the inner surfaces of the top plate and the bottom plate. Using a mold in which a plurality of grooves having a width of 1 to 3 mm are continuously formed from one end to the other in a radial, grid, or substantially parallel to each other so that residual gas in the mold is discharged from the grooves to the outside during the molding. A method for forming quartz glass, characterized in that:
Claim 2 :
Molding method according to claim 1, wherein a gap between the plurality of grooves has a groove so as to 30mm or less for substantially parallel to each other.
Claim 3 :
The molding method according to claim 1 or 2 , wherein the rate of temperature rise from 1400 ° C or higher is 20 ° C / min or lower.
Claim 4 :
A top plate is disposed so as to be movable in the vertical direction, and the quartz glass charged in the mold through the top plate is molded by applying a load not more than twice the weight of the quartz glass. molding method according to any one of 3.
Claim 5 :
The molding method according to any one of claims 1 to 4 , wherein the molding is performed by interposing an air-permeable inclusion between the mold inner surface and the quartz glass.
[0009]
Hereinafter, the present invention will be described in more detail.
The method for molding quartz glass of the present invention is performed using a graphite or carbon mold in which the upper and lower ends of a cylindrical body such as a cylinder or a rectangular cylinder are closed and a top plate and a bottom plate are provided.
[0010]
In this case, the present invention uses a mold in which a plurality of grooves are formed on the entire inner peripheral surface of the cylindrical body, and the inner surfaces of the top plate and the bottom plate.
[0011]
FIG. 1 shows an example of a mold 1 used in the present invention. In this example, a square in which a top plate 3 and a bottom plate 4 are disposed by closing the upper and lower ends of a rectangular cylindrical body 2. Although it has a box shape, the mold of the present invention is not limited to this.
[0012]
A plurality of grooves 5 are formed on the inner peripheral surface of the cylindrical body 2 (the inner surface of each side plate 2a), the inner surface of the top plate 3, and the inner surface of the bottom plate 4, respectively.
[0013]
As described above, the mold used in the present invention has the groove 5 formed on the entire inner surface thereof, and when the groove is not provided on the inner surface of the mold, or only the inner surface of the cylindrical body or only the inner surfaces of the top plate and the bottom plate. If the groove is not formed on the entire surface, such as not having a groove on the other inner surface, the gas between the glass surface and the mold or an inclusion such as a graphite or carbon sheet inserted therebetween May remain, and may not be molded accurately according to the shape in the mold, but may remain as bubbles on the outer periphery of the glass.
[0014]
Further, the form of the groove may be any of radial, grid, vertical and horizontal or diagonal directions, and the entire inner surface of the mold may be the same or different. May be formed differently on the inner peripheral surface of the cylindrical body (that is, on the side plates), but the residual gas is radially on the upper and lower surfaces and on the cylindrical inner peripheral surface (side surface). Since the top and bottom plates (upper and lower surfaces) are considered to come out from the vertical direction, they are radial, latticed, vertical and horizontal, or diagonal in one direction, and in the cylindrical body peripheral surface (side surface) in the vertical direction. Preferably there is.
[0015]
In the example of FIG. 1, grooves 5 are provided along the vertical direction on the cylindrical body 2 (each side plate 2 a), and lattice-like grooves 5 are provided on the top plate 3 and the bottom plate 4, respectively. Yes. In this case, as shown in the drawing, each groove 5 is preferably formed in a continuous state from one end to the other end, and the groove of the cylindrical body 2 and the grooves of the top plate 3 and the bottom plate 4 are mutually at their ends. It is preferable from the point of escape of residual gas to form so as to communicate with each other.
[0016]
The mold 1 is placed on a fixing base jig 6 as shown in the figure, and a quartz glass ingot 7 is placed in the mold 1 and heated, melted, and molded. In this case, The top plate 3 can be disposed in the cylindrical body 2 so as to be slidable in the vertical direction, and it is preferable to place a weight 8 on the top plate 3 and load the quartz glass to be formed. is there. In the figure, 9 is a fixing jig. As described above, when the top plate 3 is disposed below the upper end edge of the cylindrical body 2 during molding, for example, by arranging the top plate 3 so as to be slidable in the vertical direction, the cylindrical body as described above. 2, a groove continuous from the upper end to the lower end along the vertical direction is opened upward at the upper end portion so that residual gas in the groove escapes to the outside, and the grooves of the top plate 3 and the bottom plate 4 form the cylindrical body 2. In this case, the residual gas in these grooves can also escape to the outside.
[0017]
Here, the size or the like of the groove formed on the inner surface of the mold of the present invention is 0.5 to 10 mm in depth , preferably 1 to 3 mm, 1 to 3 mm in width, preferably 1.5 to 2 mm, and substantially parallel to each other. The space between the grooves in the state is 30 mm or less, preferably 20 mm or less, and 5 mm or more, particularly 10 mm or more. In the case of radial grooves, the angle between the grooves is preferably 10 to 30 degrees, particularly preferably 15 to 20 degrees. When the depth of the groove is less than 0.5 mm or when the width of the groove is less than 1 mm, the gas is not easily discharged, and as a result, the residual gas cannot be formed into a desired shape. In addition, when the depth of the groove exceeds 10 mm or the width exceeds 3 mm, the quartz glass enters the groove, leaving traces of the groove on the surface of the formed quartz glass, and forming into a desired shape. There are cases where it cannot be done.
[0018]
The thickness of the mold is not particularly limited as long as it is a range that is usually used, but a thickness of 10 mm or more, preferably 20 mm or more is used.
[0019]
In the present invention, quartz glass can be molded by a usual method except that the above mold is used. Usually, in the above graphite or carbon mold, the fused quartz glass is 1400 ° C. or higher, preferably It is performed by a method in which molding is performed at a temperature of 1700 ° C. or higher under vacuum or reduced pressure, and under an inert gas such as argon or helium.
[0020]
In this case, the quartz glass ingot can be put into the mold and heated, melted and molded at a temperature of 1400 to 1900 ° C., but at this time, the rate of temperature rise is preferably 20 ° C./min or less, more preferably Residual gas can be easily discharged by setting it to 15 ° C./min or less and 1 ° C./min or more.
[0021]
Further, by applying a load of not more than twice, preferably 0.5 to 2 times, more preferably the same weight to the quartz glass charged in the mold, the mold does not melt into the groove on the inner surface of the mold. It can be formed into a desired shape along the inner surface.
[0022]
During molding, a gas-permeable inclusion such as graphite or carbon is provided on the inner surface of the mold, and the inclusion is interposed between the mold inner surface and the quartz glass to be molded. Molding can be performed.
[0023]
The method for molding quartz glass of the present invention is not only used for molding quartz glass for lenses and photomasks, but can also be applied to molding of general glass.
[0024]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.
[0025]
[Example 1]
The bottom plate of the cylindrical body having a square shape with a length of 200 mm in length and width and a rectangular column-shaped hollow portion with a height of 800 mm is closed to dispose the bottom plate, and the upper end open portion is closed. In addition, the top plate is disposed so as to be slidable in the up and down direction in the hollow portion, and has the shape shown in FIG. As shown in Fig. 2, a groove having a depth of 0.5 mm and a width of 1 mm is formed in the vertical direction on the inner peripheral surface (inner surface of the mold) of the cylindrical body and in a lattice shape on the inner surface of the top plate and the bottom plate. A mold in which the groove of the cylindrical body and the groove of the top plate and the bottom plate communicate with each other so that the distance between them is 20 mm, and a 1 mm thick carbon sheet having air permeability is mounted on the entire inner surface of the mold. Was used to mold quartz glass.
[0026]
First, a cylindrical 43.9 kg quartz glass having a height of 700 mm and a diameter of 195 mm was put in the above mold, a weight of 20 kg was placed on the top plate, and set in a furnace with a maximum output of 60 KW. The vacuum pump was operated and the pressure in the furnace was reduced to 5 × 10 ⁻⁵ Torr, and then the temperature was raised.
[0027]
The temperature was raised to 1400 ° C. in 30 minutes, and then to 1850 ° C., the temperature was raised at 18 ° C./minute, and then maintained at 1850 ° C. for 120 minutes. At this time, it was maintained at 0.5 Torr using a vacuum pump and a diffusion pump.
[0028]
Thereafter, the electric power is lowered to 1300 ° C. in 30 minutes, and the electric power thereafter is lowered linearly. When the room temperature is reached, the furnace is opened, and a square-shaped square bar-shaped quartz glass having a height of 520 mm and a side of 200 mm. 43 kg was obtained. In the obtained square bar-shaped quartz glass, each corner was accurately shaped along the inner shape of the above-mentioned mold, and further no entrainment of bubbles was observed.
[0029]
[Example 2]
A carbon mold having a thickness of 10 mm and a groove having a depth of 10 mm, a width of 3 mm, and an interval of 20 mm is used in the vertical direction (vertical direction) with respect to the side surface inside the mold and in the horizontal direction with respect to the vertical surface. Except for the above, it was molded in the same manner as in Example 1. As a result, the obtained square bar-shaped quartz glass was accurately shaped at the corners along the inner shape of the mold, and no bubble entrainment was observed.
[0030]
[Comparative Example 1]
When the same carbon mold as in Example 1 in which no groove was provided on the entire inner surface of the mold was molded in the same manner as in Example 1, the obtained square bar-shaped quartz glass had corners along the inner shape of the mold. It was not accurately shaped, and further entrainment of bubbles was observed.
[0031]
【The invention's effect】
According to the method for molding quartz glass of the present invention, the quartz glass can be molded into a desired shape with less entrainment of bubbles.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing an example of a molding die used in the practice of the present invention.
[Explanation of symbols]
1 Type 2 Tubular body 3 Top plate 4 Bottom plate 5 Groove 6 Fixing base jig 7 Quartz glass ingot 8 Weight 9 Fixing jig

Claims (5)

Heating the quartz glass in each closed the upper and lower end portions of the tubular body top plate and bottom plate in a graphite or a mold made of carbon is provided, when molded in melt, the inner peripheral surface entire surface of the cylindrical body A plurality of grooves having a depth of 0.5 to 10 mm and a width of 1 to 3 mm are formed continuously from the upper end to the lower end along the vertical direction, and the depths of 0.5 to 10 mm are respectively formed on the inner surfaces of the top plate and the bottom plate. Using a mold in which a plurality of grooves having a width of 1 to 3 mm are continuously formed from one end to the other in a radial, grid, or substantially parallel to each other so that residual gas in the mold is discharged from the grooves to the outside during the molding. A method for forming quartz glass, characterized in that: Molding method according to claim 1, wherein a gap between the plurality of grooves has a groove so as to 30mm or less for substantially parallel to each other. The molding method according to claim 1 or 2 , wherein the rate of temperature rise from 1400 ° C or higher is 20 ° C / min or lower. A top plate is disposed so as to be movable in the vertical direction, and the quartz glass charged in the mold through the top plate is molded by applying a load not more than twice the weight of the quartz glass. molding method according to any one of 3. The molding method according to any one of claims 1 to 4 , wherein the molding is performed by interposing an air-permeable inclusion between the mold inner surface and the quartz glass.

Images