JP2003112927A - Glass forming method and glass forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass forming method which is based on an isothermal forming method, shortens the time required for lowering the temperature of a flat plate-shaped glass material which is heated and pressed up to the glass softening temperature or less, improves throughput and performs glass forming with high productivity. SOLUTION: The glass forming method comprises a process of heating and pressing the glass material 19 and forming the same into a flat plate with a pair of dies 7a, 7b, a process of decreasing a pressurizing force after the flat plate forming and, at the same time, stopping the heating and a process of subsequently releasing the same from the dies 7a, 7b. Therein, after the process of decreasing pressurizing force and stopping the heating and before the process of the releasing, cooling fluid is supplied to cooling fluid passages 14, 14 which are formed so as to be contact with back surfaces of the dies 7a, 7b in pressurizing pieces 6a, 6b which support the dies 7a, 7b, thereby the dies 7a, 7b are cooled from the back surfaces and, thus, the glass material 19 which is formed in flat plate is forcibly cooled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass forming method and a glass forming apparatus, and more particularly to a technique for forming a glass substrate with high surface precision and high precision. A glass substrate for a magnetic disk is a typical example of a glass substrate having high surface accuracy.

[0002]

2. Description of the Related Art First, as a reference, the historical background of technology will be described.

With the spread of computers in recent years, there is a great demand for high performance such as miniaturization and high capacity in a hard disk, which is one of external storage devices. Along with this, low flying of magnetic heads has been actively studied, and extremely high accuracy is required for smoothness of magnetic disks.

Conventionally, aluminum alloys have been mainly used as substrate materials for magnetic disks. However, the hardness of the aluminum alloy substrate is low. Therefore, even if precision polishing is performed using highly accurate abrasive grains and a polishing device, the polished surface is plastically deformed. That is, it is difficult to obtain a highly accurate smooth surface. Also, nickel with higher hardness? Even if the phosphorous plating layer is formed on the substrate surface, it is difficult to meet the current high demand for smoothness accuracy.

Further, the technological trend toward miniaturization requires a thinner disc thickness. From this point of view, it is difficult to meet the demand with the aluminum alloy substrate having low strength.

Recently, the adoption of a high-sensitivity giant magnetoresistive head has been promoted. Along with this, the magnetic disk is required to reduce noise, and the substrate is required to respond to noise reduction by heat treatment after the magnetic film is formed.

However, also in this respect, it is difficult to meet the above requirements in the case of the aluminum alloy substrate.

Therefore, new materials such as glass, ceramics and carbon have been proposed as substrates for magnetic disks. Above all, the glass substrate has been widely studied and already put into practical use.

The glass substrate has high strength and good heat resistance. Further, high precision polishing with high surface hardness can sufficiently meet the demand for high precision smoothness.

Conventionally, a glass substrate for a magnetic disk has been manufactured by a polishing method in which each glass substrate is precisely polished to obtain a smooth surface after being cut into a predetermined size.

However, there are drawbacks that the polishing process requires high accuracy and the number of processes is large.

The following is a description of the prior art which is a direct comparison object with the present invention.

For the above reasons, a new method of manufacturing a glass substrate for a magnetic disk is being studied. It is an isothermal press molding method in which a mold and a glass material are pressed at an equal temperature. The isothermal press molding method has been extensively studied in the field of optical glass element manufacturing, and has already been put into practical use as a manufacturing method capable of high quality and high productivity.

FIG. 6 is a front view showing a schematic structure of a conventional glass forming apparatus.

In FIG. 6, reference numeral 31 is a device frame, and 32 is a device frame.
Is a hydraulic cylinder, 32a is a piston rod of the hydraulic cylinder 32, 33a is an upper indenter attached to the lower end of the piston rod 32a, 33b is a lower indenter fixed to the lower part of the device frame 31, and 34a and 34b are indenters. 33a, 33b
, 35a is an upper mold supported by the upper indenter 33a, 35b is a lower mold supported by the lower indenter 33b, and 36 is a glass material to be molded.

When the glass material 36 is sandwiched between the upper and lower molds 35a and 35b preheated to near the glass softening point temperature by the heaters 34a and 34b and the hydraulic cylinder 32 pressurizes the glass material 36, the glass material 36 is softened and deformed, and a flat disk is formed. Formed into a shape. When the pressure applied by the hydraulic cylinder 32 is reduced when the glass material 36 has reached a predetermined thickness, the glass material 36 hardly deforms. Therefore, the heater 34
When the currents of a and 34b are cut off, the temperatures of the molds 35a and 35b are lowered to the glass softening point temperature or lower. At that time, the glass material 36 is solidified and a flat glass substrate is completed.

[0017]

However, in the glass forming method based on such a conventional isothermal press forming method, the cooling step of lowering the temperature of the mold to the glass softening point temperature or lower is natural cooling. Because it is natural cooling,
Since the predetermined cooling takes a lot of time and the throughput is low, the productivity is poor. If a large number of devices are provided, the productivity is improved, but if a large number of devices are provided, there is a problem that manufacturing cost and maintenance cost increase and the product price increases.

The present invention was created in order to solve the above-mentioned problems. By shortening the cooling time, the throughput can be improved and glass molding can be performed with high productivity. Is intended.

[0019]

The present invention regarding a glass forming method and a glass forming apparatus solves the above problems by taking the following means.

The glass forming method of the present invention comprises a step of heating and pressing a glass material into a flat plate by a pair of molds, a step of reducing the applied pressure and stopping the heating after the flattening step, and then a step of molding the metal. It is premised that a step of releasing the mold is included. In such a glass forming method, after supplying the cooling fluid to the indenter supporting the mold after the step of reducing the pressure and stopping the heating and before the step of releasing the mold. It is characterized in that the mold is cooled from the back side thereof, and thus the flattened glass material is forcibly cooled.

Further, in the glass forming apparatus of the present invention, at least one of the pair of molds which can be moved toward and away from each other, the pair of indenters for supporting each of the molds, and at least one of the both indenters is moved in and out. It is premised that a driving means is provided. Further, in such a glass forming apparatus, it is characterized in that each of the both indenters is formed with a cooling fluid flow path for flowing a cooling fluid along the back surfaces of both molds.

According to the present invention, a glass material flattened into a predetermined shape and a predetermined dimension by heating and pressurization is caused by the flow of the cooling fluid in the cooling fluid passage of the indenter before the mold release (before the mold opening). Both dies are positively and effectively cooled through forced cooling of the dies from the back of the dies. Therefore, the time required for the flattened glass material to cool to the glass softening point temperature or lower can be significantly shortened as compared with the conventional method of natural cooling.

Further, in general, a die is required to have a high processing accuracy, and the cost tends to increase from the viewpoint of material and processing. If such a die itself is to be provided with a cooling fluid flow channel, the cost is high. The surface becomes more severe. In the present invention, the cooling fluid flow path is not formed in the mold itself, but the cooling fluid flow path is formed in the indenter supporting the mold. For this reason, the degree of freedom in designing the cooling fluid channel is high. That is, it is easy to form a cooling fluid flow path that provides more effective cooling. In addition, the cost burden can be reduced.

As described above, the throughput can be improved and the productivity can be improved. Further, since it is possible to alleviate the necessity of providing a large number of devices, it is possible to advantageously develop equipment, manufacturing costs, and maintenance costs. As a result, it is advantageous in promoting the reduction of the product price. Moreover,
The magnetic recording medium manufactured by using the glass substrate manufactured in this way is easy to increase the density and size due to the excellent smoothness of the glass substrate. This is advantageous in manufacturing the medium at low cost.

Gas is generally desirable as the cooling fluid. This is because the indenter cooled in the cooling step suppresses heat taken from the mold in the heating / pressurizing step as much as possible. It is common to stop the flow of the cooling fluid in the process of heating and pressurizing the glass material, but since the gas has a smaller heat capacity than the liquid and the gas whose flow is stopped has a high adiabatic property, in the heating and pressurizing process The temperature rising rate of the mold can be increased.

However, the cooling fluid is not necessarily limited to gas, and may be liquid. Of these, liquids rich in volatility are preferable.

A cylinder is a suitable example of the drive means, but both indenters may be provided with drive means, or only one of the indenters may be provided with drive means.

In a preferred embodiment of the above-mentioned glass forming method invention, in the step of cooling the mold, the cooling fluid is radially diffused and flowed from the center of the mold along the back surface of the mold. Is.

In a preferred aspect of the invention of the above-mentioned glass forming apparatus, the indenter is a cooling fluid lead-out path for leading out the cooling fluid to the central part of the indenter body, and the cooling fluid is radiated from the cooling fluid lead-out path. And a plurality of grooves that allow the fluid to flow.

Since the degree of contact with the outside air is lower in the central portion of the mold than in the peripheral portion, the heat storage property is high, and accordingly it is more difficult to cool. Cooling fluid is led out to the hard-to-cool central part and radially flows from the central part to the outer peripheral part to cool the mold axisymmetrically, so the heat exchange efficiency between the cooling fluid and the hot mold Will be high. Further, the cooling fluid can be evenly flowed on the back surface of the mold. Therefore, it is possible to enhance the cooling effect with respect to the mold and further the flattened glass material.

In a preferred embodiment of the invention of the above-mentioned glass forming apparatus, the indenter is constituted by a radiation fin having a thin wall for partitioning the radial groove.

The width of the cooling fluid channel is widened by reducing the thickness of the radiating fins, and the contact area between the cooling fluid channel and the hot mold back surface is designed to be as large as possible. This makes it possible to effectively remove heat from the high temperature mold, and further enhance the cooling effect for the mold, and thus the flattened glass material.

Further, in a preferred aspect of the invention of the above-mentioned glass forming apparatus, the indenter has a cooling fluid lead-out path for leading out the cooling fluid to the center of the indenter body, and a concentric ring around the cooling fluid lead-out path. It is provided with a plurality of annular walls forming a circular annular groove, and a communication groove formed in a state where the adjacent annular grooves communicate with each other at a plurality of circumferential positions of the annular wall.

In this case, a labyrinth-like cooling fluid flow path is formed as a whole by the plurality of concentric annular grooves and the plurality of communication grooves which communicate these. This allows the cooling fluid to flow evenly on the back surface of the mold, and effectively cools the mold, and thus the flattened glass material. In addition, it is more preferable for effective cooling that the communication groove of one annular wall and the communication groove of the adjacent annular wall are out of phase with each other.

Further, in a preferred aspect of the invention of the above-mentioned glass forming apparatus, the indenter is suitable around a cooling fluid outlet passage for leading out the cooling fluid to the center of the indenter body and around the cooling fluid outlet passage. And a plurality of pin portions that are dispersedly arranged at intervals.

In this case, by providing a large number of pins, the total contact area of the end surface of the pin with the mold and the total contact area of the peripheral surface of the pin with the cooling fluid flowing in the cooling fluid passage are increased. Have secured as. This allows
The cooling fluid can be evenly flowed on the back surface of the mold, and the mold and thus the flattened glass material can be effectively cooled.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a glass forming apparatus of the present invention and a glass forming method carried out using this apparatus will be described in detail below with reference to the drawings.

FIG. 1 is a partially cutaway front view showing a schematic structure of a glass forming apparatus according to an embodiment of the present invention, FIG. 2 is a perspective view showing details of an indenter, and FIG. 3 is a drawing operation during heating and pressing. It is a partially broken sectional view showing a state.

As shown in FIG. 1, a base 1, a plurality of support columns 2 and a top plate 3 constitute an apparatus frame body 4. The cylinder body 5a of the hydraulic cylinder 5 is provided at the center of the top surface of the top plate 3.
Is mounted in a vertical posture, and its piston rod 5b penetrates the top plate 3 downward. Inside the device frame 4, the indenter 6a is attached to the lower end of the piston rod 5b, the upper die 7a is attached to the lower surface of the indenter 6a, and the die 7a is for heating the die 7a. Heater 8
a is provided.

A support 9 is fixed to the center of the upper surface of the base 1 of the apparatus frame 4, an indenter 6b is attached to the upper surface of the support 9, and a lower die 7 is attached to the upper surface of the indenter 6b.
b is mounted, and the die 7b is further provided with a heater 8b for heating the die 7b. Mold 7a, 7b
The temperature control is performed by turning on / off the current flowing through the heaters 8a and 8b.

Although FIG. 2 shows the details of the lower indenter 6b, the upper indenter 6a has a similar structure. The indenter 6b has an indenter body 10 as a main component.
A cooling fluid outlet path 11, a plurality of arc-shaped grooves 12, and a plurality of arc-shaped heat radiation fins 13.

A cooling fluid lead-out passage 11 is formed in the center of the indenter body 10. The cooling fluid lead-out passage 11 is
The indenter body 10 is formed in such a manner that it extends from the center of the front surface side of the indenter body 10 along the axial direction to the intermediate thickness portion, then extends radially outward, and further extends along the axial direction to reach the back surface of the indenter body 10. There is.

From the immediate vicinity of the cooling fluid outlet passage 11 to the indenter 6
A plurality of arc-shaped grooves 12 are formed in a radially expanded state over the outer peripheral portion of b. The plurality of arc-shaped radiating fins 13 left as a result of the formation of the plurality of arc-shaped grooves 12
Is also expanding radially. One arc-shaped groove 12 is formed between two arc-shaped heat radiation fins 13 that are adjacent to each other in the circumferential direction. The thickness of each arc-shaped radiation fin 13 is sufficiently smaller than its height. This is because by making the heat radiation fins 13 arcuate, the strength can be increased as compared with the case of being linear, and the required strength can be secured while reducing the thickness.

The plurality of arc-shaped heat radiation fins 13 are the indenter body 1
0 is constructed as a series. The plurality of arc-shaped radiating fins 13 have respective end surfaces flush with each other,
One end of the surface is configured to be in close contact with the mold 7b. In this way, the indenter 6b is brought into close contact with the die 7b and airtightly fixed to each other, so that the arc-shaped groove 12, the arc-shaped radiating fins 13 and the die 7b form a plurality of arc-shaped cooling fluid flow paths 14. Is forming. This cooling fluid channel 1
Reference numeral 4 is a back surface (back surface) of the mold 7b, which is developed in an arcuate shape. That is, by causing the cooling gas flowing from the cooling fluid outlet passage 11 to flow into the plurality of cooling fluid flow passages 14, the cooling fluid is radially radiated from the center toward the outer side in the radial direction on the back surface of the mold 7b. Let it flow.

By forming the radiation fin 13 thin in this way, the radiation efficiency by heat conduction is increased. In addition, the heat radiation efficiency is increased by forming many heat radiation fins 13 and grooves 12.

The above description of the lower indenter 6b also applies to the upper indenter 6a.

The upper die 7a and the lower die 7b are
Both have a mold body 15 and a protruding molding surface 16. A molding surface 16 that directly acts on the glass material to be molded is formed in the mold body 15 in a protruding state. The protruding molding surface 16 is formed integrally with the mold body 10 in series. The heaters 8a and 8b are attached to the outside of the projecting molding surfaces 16 and 16.

Cooling fluid flow path 1 in both indenters 6a, 6b
4, 14 are connected to cooling fluid supply hoses 18, 18 via joints 17, 17. The other ends of the cooling fluid supply hoses 18, 18 are connected to a cylinder of cooling fluid (not shown). A gas is generally used as the cooling fluid, and for example, nitrogen at room temperature is used.

Next, the operation of the glass forming apparatus configured as described above will be described with reference to FIGS.

In the mold open state of FIG. 1, the heaters 8a and 8b are
The glass material 19 is placed on the protruding molding surface 16 of the lower mold 7b in a state where the molds 7a and 7b are preheated to near the glass softening point temperature by controlling the energization to the mold. The hydraulic cylinder 5 is driven to extend, the piston rod 5b is moved downward, and the upper indenter 6 is moved.
a and the die 7a are integrally moved downward, and the upper die 7a is moved closer to the lower die 7b. Lower mold 7
The protruding molding surface 16 of the upper die 7a is brought into contact with the glass material 19 placed on the protruding molding surface 16 of b,
By further extending the hydraulic cylinder 5, the glass material 19 is held between the protruding molding surfaces 16 of the upper and lower molds 7a and 7b.

By controlling the energization of the heaters 8a and 8b, the molds 7a and 7b are heated to a predetermined temperature and maintained at the predetermined temperature while being heated by the protruding molding surfaces 16 and 16 of the two molds 7a and 7b. Pressurize. When the temperature of the glass material 19 reaches the glass softening point temperature in the process, the softened glass material 19 is softened and deformed into a disk shape by the applied pressure.

At the stage where the glass material 19 is softened and deformed to a predetermined shape and size, the pressure applied by the hydraulic cylinder 5 is reduced and the energization of the heaters 8a and 8b is turned off. At this point, cooling gas (for example, nitrogen at room temperature) is supplied from the cooling fluid supply hoses 18, 18 while maintaining the mold clamped state of both molds 7a, 7b. Cooling gas is double indenter 6
a, 6b through the cooling fluid lead-out passages 11, 11 at the central portions of the molds 7a, 7b in an arc-shaped radial cooling fluid flow path 1
Flow 4,14.

This arc-shaped radial cooling fluid flow path 14, 14
In the process in which the cooling gas flows in an arcuate shape from the center side to the outer peripheral side, heat exchange between the cooling gas and the molds 7a, 7b in the high temperature state progresses, and the molds 7a, 7b are cooled relatively rapidly. To go. At this time, the arc-shaped radial cooling fluid flow path 1
Since there are a large number of 4, 14 and they are densely and regularly arranged, the cooling gas comes into uniform contact with the entire back surfaces of the molds 7a, 7b. This makes the mold 7
A and 7b can be positively and effectively forcibly cooled.

Further, the thickness of the radiating fins 13 is made thin so that the flow width of the cooling fluid flow path 14 is made as wide as possible. That is, the contact area between the cooling fluid flow path 14 and the back surfaces of the hot molds 7a and 7b is designed to be as large as possible. Further, the height of the heat radiation fins 13 is made relatively large so that the flow passage depth of the cooling fluid flow passage 14 is secured as large as possible. That is,
The device has been devised to increase the flow passage cross-sectional area and to secure as much flow rate as possible per unit time. This makes it possible to effectively remove heat from the hot molds 7a and 7b. The cooling gas heated by the heat exchange is used in the mold 7
It is discharged from the outer peripheral portions of a and 7b.

Both molds 7 in the mold clamped state as described above
The temperature of the molds 7a and 7b is rapidly lowered by causing the cooling gas to flow evenly on the back surfaces of the a and 7b, and the temperature of the glass material 19 formed into a disk shape that is in contact with the protruding molding surfaces 16 and 16. To drop rapidly. Glass material 19
If the temperature is below the glass softening point temperature, the glass material 19
Since it solidifies and does not deform, it can be taken out. Therefore, the hydraulic cylinder 5 is driven to contract, and the upper indenter 6a and the mold 7a are raised together with the piston rod 5b, and the molds 7a and 7b are released (mold opening).

In the above, in the step of heating and pressing the glass material 19, the flow of the cooling gas is stopped. If they are made to flow, the rate of temperature rise of the mold is suppressed due to heat removal. Since the cooling medium is a gas, the gas has a relatively small heat capacity, and the gas when the flow is stopped has high adiabaticity,
It is possible to increase the rate of temperature rise of the mold in the heating / pressurizing step. The radiating fins 13 are formed as thin as possible so that the contact area between the radiating fins 13 and the back surface of the mold is made small to suppress heat removal from the mold in the heating and pressing step.

A modified example of the indenter for forming the cooling fluid passage on the back surface of the mold will be described.

The indenter shown in FIG. 4 is constructed as follows.

At the center of the indenter body 10, the cooling fluid outlet passage 1 is provided.
1 is formed. A plurality of annular walls 20 are concentrically formed integrally on one side of the indenter body 10 in series. An annular groove 21 is formed between the annular walls 20 that are adjacent to each other in the radial direction. Communication grooves 22 are formed in each of the annular walls 20 at appropriate intervals in the circumferential direction, and the adjacent annular grooves 21 and 21 are connected to each other through the communication grooves 22.
Regarding the phase of the communication groove 22, that is, the position in the circumferential direction, the phase is made different between the annular walls 20, 20 that are adjacent in the radial direction. The hatched area in the annular wall 20 is the end surface of the annular wall 20 other than the communication groove 22, and is the portion that contacts the mold. In this case, hatching does not mean a cross section.

A labyrinth-like cooling fluid flow path 23 is formed as a whole by the plurality of concentric annular grooves 21 and the plurality of radial communication grooves 22 which have alternating phases. . As a result, the cooling gas can be made to flow evenly on the back surface of the mold, and the mold and thus the flattened glass material can be effectively cooled.

The indenter shown in FIG. 5 is constructed as follows.

At the center of the indenter body 10, the cooling fluid outlet 1
1 is formed. A large number of columnar pin portions 24 are formed in a matrix on one side surface of the indenter body 10 at predetermined intervals. A cooling fluid channel 25 is provided between the pin portions 24. The hatching indicates the end face of the pin portion 24 that contacts the mold. Hatching does not mean cross section. By providing a large number of pin portions 24, a large total contact area with the mold on the end surface of the pin portion and a large total contact area with the cooling gas flowing in the cooling fluid flow passage 25 on the peripheral surface of the pin portion are secured. There is. As a result, the cooling gas can be made to flow evenly on the back surface of the mold, and the mold and thus the flattened glass material can be effectively cooled.

[0063]

As described above, according to the present invention, the glass material flattened by heating and pressurizing the glass material from the back surface of the mold by the flow of the cooling fluid in the cooling fluid passage of the indenter before the mold release. Since it actively and effectively cools through forced cooling of the mold, the time until the flattened glass material cools below the glass softening point temperature, compared to the conventional method of natural cooling,
It can be greatly shortened. Therefore, throughput can be improved and productivity can be improved.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view showing a schematic configuration of a glass forming apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view showing details of an indenter in the glass forming apparatus according to the embodiment of the present invention.

FIG. 3 is a partially cutaway sectional view showing a state during a molding operation by heating and pressurizing the glass molding apparatus according to the embodiment of the present invention.

FIG. 4 is a plan view showing another form of the indenter in the glass forming apparatus according to the embodiment of the present invention.

FIG. 5 is a plan view showing still another form of the indenter in the glass forming apparatus according to the embodiment of the present invention.

FIG. 6 is a schematic diagram showing the configuration of a press molding machine used in a conventional glass molding method.

[Explanation of symbols]

1 base 2 support pillars 3 Top plate 4 Device frame 5 hydraulic cylinder 6a, 6b indenter 7a, 7b mold 8a, 8b heater 9 Support stand 10 Indenter body 11 Cooling fluid outlet 12 grooves 13 Radiation fin 14 Cooling fluid flow path 15 Mold body 16 Projected molding surface 17 joints 18 Cooling fluid supply hose 19 glass 20 ring wall 21 annular groove 22 communication groove 23 Cooling fluid flow path 24-pin part 25 Cooling fluid flow path

Claims (7)

[Claims] 1. A step of heating and pressing a glass material into a flat plate shape by a pair of molds, a step of reducing the applied pressure and stopping heating after the flattening step, and then a step of releasing the mold. A glass forming method comprising: a step of supplying a cooling fluid to an indenter supporting the mold after the step of reducing the pressure and stopping the heating and before the step of releasing the mold. A glass forming method comprising cooling a mold from the back side thereof and forcibly cooling the flattened glass material. 2. The glass according to claim 1, wherein, in the step of cooling the mold, the cooling fluid is radially diffused and flowed from a central portion of the mold along a back surface of the mold. Molding method. 3. A glass forming apparatus comprising: a pair of dies that can approach and separate from each other, a pair of indenters that respectively support the dies, and a drive unit that moves at least one of the indenters. The glass forming apparatus is characterized in that a cooling fluid flow path for flowing a cooling fluid is formed along the back surfaces of the molds in each of the indenters. 4. The indenter includes a cooling fluid lead-out path for leading out the cooling fluid to the center of the indenter body, and a plurality of grooves for radially flowing the cooling fluid from the cooling fluid lead-out path. The glass forming apparatus according to claim 3, wherein: 5. The glass forming apparatus according to claim 4, wherein the indenter is configured by a radiating fin whose wall that divides the radial groove is thin. 6. The indenter includes a cooling fluid lead-out path for leading out the cooling fluid to the center of the indenter body, and a plurality of annular walls forming concentric annular grooves around the cooling fluid lead-out path.
The glass forming apparatus according to claim 3, further comprising: a communication groove formed so as to communicate between adjacent annular grooves at a plurality of circumferential positions of the annular wall. 7. The indenter includes a cooling fluid lead-out path for leading out the cooling fluid to the center of the indenter body, and a plurality of pin portions distributed around the cooling fluid lead-out path at appropriate intervals. The glass forming apparatus according to claim 3, wherein the glass forming apparatus is provided.