JPH04175229A - Method for molding glass - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a glass forming method. INDUSTRIAL APPLICATION This invention is effectively applied to the continuous molding of optical elements, such as an aspherical lens, for example.

[Problems to be solved by conventional techniques and inventions] In recent years,
A material for molding an optical element, such as a glass blank preformed to a certain degree of shape and surface accuracy, is placed in a mold with a predetermined surface accuracy, and press-molded under heat. BACKGROUND ART A method for manufacturing an optical element having a high-precision optical functional surface that does not require post-processing has been developed.

In such a press molding method, an upper mold member for molding and a lower mold member for molding are generally arranged slidably opposite each other within a molding body member, and these upper mold member, lower mold member, and body mold member Introduce the molding material into the cavity formed by
To prevent oxidation of the mold member, the atmosphere is set to a non-oxidizing atmosphere, such as a nitrogen atmosphere, and the mold member is heated to a moldable temperature, for example, a temperature at which the molding material becomes 10" to 1012 poise. The mold is closed and pressed for an appropriate time. The surface shape of the mold member is transferred to the surface of the molding material, the temperature of the mold member is cooled to a temperature sufficiently lower than the glass transition temperature of the molding material, the press pressure is removed, and the mold is opened to take out the molded optical element.

The above-mentioned optical element press molding method and its apparatus are disclosed in, for example, JP-A-58-84134 and JP-A-49-97.
Publication No. 009, British Patent No. 378199,
JP-A-63-11529, JP-A-59-1507
This method is disclosed in Japanese Patent Publication No. 28, Japanese Patent Application Laid-Open No. 61-26528, and the like.

Furthermore, in Japanese Patent Application Laid-Open No. 1-105713, a heater is provided partially in the longitudinal direction of the barrel member, and a cooler is partially provided in the longitudinal direction of the barrel member, thereby forming a temperature distribution in the longitudinal direction of the barrel member. , moving the cavity position by moving the upper mold member and the lower mold member with respect to the body mold member, thereby controlling the temperature of the molding material and the molded optical element,
A press molding die device is disclosed which aims to shorten the time required for one cycle of press molding.

By the way, in the conventional molding apparatus for the above-mentioned press, the molding material may be preheated to a moldable temperature before being introduced into the mold cavity, but in this case, special means for conveying the softened material is required. The equipment required for preheating is large-scale, which impedes miniaturization of the equipment, and the material may be deformed during transportation or foreign matter may adhere to the surface of the material, resulting in a decrease in appearance and shape accuracy. . In addition, there are cases where the material is heated by heating the mold member after introducing the molding material into the mold cavity. Because heating was performed with the mold cavity left open through the opening, thermal energy was not used to heat the material with sufficient efficiency, resulting in long heating times and making it difficult to shorten the press cycle.

Therefore, the present invention has good thermal energy utilization efficiency, can shorten the press cycle, can perform press forming repeatedly and continuously, can downsize the equipment, and can produce molded products of good quality. The object of the present invention is to provide a glass forming method that can obtain the following.

[Means for Solving the Problems] According to the present invention, in order to achieve the above object, a lower mold member for molding and an upper mold member for molding are provided in the molding trunk member, respectively. A method of molding glass using a glass molding device in which a mold cavity is formed by these three mold members, and the molding material is heated to a temperature lower than its glass transition point. The lower mold member for molding and the upper mold member for molding are inserted into the mold cavity while maintaining the interval between the lower mold member and the upper mold member to be larger than the interval during pressing. The mold cavity is closed by sliding it in the longitudinal direction of the mold member, and based on the heating of the lower mold member, upper mold member, and body mold member (radiation heat and conduction from these mold members). Heat the molding material to a moldable temperature,
There is provided a method for forming glass, which is characterized in that the upper mold member and the lower mold member are then brought close together and pressed.

In the present invention, there is an embodiment in which a temperature distribution is imparted to the molding body member in its longitudinal direction, and when the mold cavity is closed, the cavity is positioned on the high temperature side.

Further, in the present invention, there is an aspect in which the molding material is spherical.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic vertical cross-sectional view showing the schematic configuration of an embodiment of a molding apparatus for carrying out the glass molding method according to the present invention, and FIG. 2 is a partially omitted partially enlarged view thereof. This example is an example of use in press molding of an optical element.

In the figure, reference numeral 2 denotes a pedestal, and a body-shaped support 4 is attached to the pedestal so as to be slidable in the vertical direction. A cylinder 6 is attached to the pedestal 2 below the support 4, and its piston rod is connected to the lower end of the support 4.

A vertical column 8 is attached to the upper part of the pedestal 2, and the support table 4 engages with the column 8 so as to be slidable in the vertical direction. An upper flat plate 10 is provided at the upper end of the pillar 8.
is fixed, and a cylinder holder 12 is attached to the flat plate.

The lower end of the barrel chamber member 20 is attached to the barrel-shaped support base 4. The barrel chamber member is arranged in the vertical direction, and a lower mold member 22 and an upper mold member 24 are arranged in the barrel mold member so as to be slidable in the vertical direction. The upper end surface of the lower mold member 22 and the lower end surface of the upper mold member 24 are transfer surfaces for forming an optically functional surface of an optical element (lens) to be molded, and are finished to a desired surface precision. A mold cavity is formed by these transfer surfaces and the inner surface of the barrel chamber member 20.

A support rod 23 in the vertical direction is provided at the bottom of the lower mold member 22.
is attached, and the lower end of the rod is fixed to the upper surface of the pedestal 2. Further, a vertical support rod 25 is attached to the upper part of the upper mold member 24, and the upper end of the rod extends into the cylinder holder 12 through the upper flat plate 10. It is attached to the flat plate 10 so as to be slidable in the vertical direction. The upper part of the rod 25 is connected to the lower end of the piston rod of the cylinder 26 held by the cylinder holder 12.

An airtight bellows 28 is attached around the rod 23 between the upper surface of the pedestal 2 and the lower surface of the support base 4, and is vertically expandable and retractable. Similarly, an airtight bellows 30 that is vertically expandable and retractable is attached around the rod 25 between the upper end of the body chamber member 20 and the lower surface of the flat plate 10.

An opening 20a for feeding a molding material, an opening 20b for taking out a molded optical element, an opening 20c for introducing a non-oxidizing gas, and an opening 20d for degassing are formed on the side of the body chamber member 20. These include a molding material feeding vibe 21a, a molded optical element extraction pipe 21b, a non-oxidizing gas introduction vibe 21c, and a deaeration vibe 21d.
is connected. Each of these vibrators 21a to 21d includes a flexible portion.

A heater 32 is attached to the upper outer periphery of the body chamber member 20, a heater 34 is built in the lower mold member 22, and a heater 36 is built in the upper mold member 24. Although not shown, a cooler, such as an air blower type, may be attached to the outside of the lower part of the body chamber member 20. Each of them can be equipped with a cooler such as a cooling water circulation type. Also, the body chamber member 20, the lower mold member 22, and the upper mold member 24 are each equipped with a thermocouple for temperature detection. I can do it.

The material feeding pipe 21a is formed with a material feeding side atmosphere replacement section 42, and as shown in FIG. 2, a heater 42 for heating the forming material is provided therein.
a and a thermocouple 42b for temperature detection. The atmosphere exchanging section has ball valves 40, 44 on both sides through which the molding material can pass, and is connected to a vacuum source (not shown) via a vibrator 43 to enable degassing.

A molded optical element extraction side atmosphere device exchange part 48 is formed in the molded optical element extraction vibe 21b.

The atmosphere exchange part has ball valves 46, 50 on both sides through which molded optical elements can pass, and a vibrator 49.
It is connected to a depressurization source (not shown) via a .

The inert gas introducing vibe 21c is connected via a valve 52 to a nitrogen gas source, which is a non-oxidizing gas. Similarly, the deaeration vibe 21d is connected to a reduced pressure source via a valve 54.

Next, the operation of the apparatus of the above embodiment will be explained. FIGS. 3 to 8 are schematic diagrams to emphasize the parts that change as the operation progresses. In these figures, the same members as in FIGS. 1 and 2 are given the same reference numerals.

First, as shown in FIG. 3, the operating position of the cylinder 26 is set, and the distance between the lower mold member 22 and the upper mold member 24 is set to be sufficiently larger than the desired thickness of the optical element. Furthermore, the cylinder 6 is operated to set the vertical position of the barrel chamber member 20 so that the molding material feed opening 20a is just above the upper end surface of the lower mold member 22.

In the cavity including the cavity in the body member 20, in the bellows 28, 30, and in the vibrators 21a, 2.
A closed system can be formed inside lb, 21c, and 2ld. Initially, the valves 40, 46° 52 are closed, and the temperature inside the closed system is set to, for example, 1×10-” Torr.
Degas until After that, the valve 54 is closed, and the valve 52 is closed.
is opened to introduce nitrogen gas into the closed system.

Then, the valve 52 is closed, the valve 44 is opened, and the material is supplied from the external magazine (not shown) to the atmosphere replacement section 42.
Put the molding material G inside and close the valve 44. Then, the molding material G is heated to an appropriate temperature below the glass transition point by the heater 42a. The introduction of the molding material G into the replacement section 42 is detected by a sensor (not shown), and the subsequent steps are sequentially controlled based on this.

The molding material G1 has a spherical shape having a volume equivalent to that of the desired optical element, and its surface is mirror-finished. Then, the inside of the atmosphere replacing section 42 is degassed via the vibrator 43, and the valve 40 is opened.

In this state, the vibrator 21a is connected to the atmosphere replacing section 42.
A slope is formed that gradually becomes lower from the side toward the body mold member 20 side, and the molding material G is supplied into the mold cavity (above the lower mold member 22) by rolling. Then, valve 40 is closed.

In this step, the temperatures of the lower mold member 22 and the upper mold member 24 are set to a temperature within the range of about ±200° C. of the glass transition point by heaters 34 and 36, respectively. That is, the temperature of the molding member near the heater 32 is maintained within a range of about ±200° C. from the glass transition point of the molding material by heating with the heater. A temperature distribution is formed in which the temperature is higher in the upper part and lower in the lower part.

Next, as shown in FIG. 4, the cylinder 6 is operated to move the barrel chamber member 20 downward, and the mold cavity is placed above the barrel member (at a height corresponding to the heater 32). position.

By controlling the heaters 32, 34, and 36, the upper part of the body chamber member 20, the lower mold member 22, and the upper mold member 24 are heated.
is the desired temperature for molding. As a result, the molding material G in the mold cavity closed by these three mold members rises to a moldable temperature higher than the glass transition point of the molding material G due to radiant heat and conduction heat from these mold members. . This heating can be started at the same time as the barrel chamber member 20 starts lowering.

Next, as shown in FIG. 5, the cylinder 26 is operated to move the upper mold member 24 downward, press the molding material to form the optical element G2, and maintain this pressed state. Maintain it for an appropriate amount of time. Press pressure is, for example, 3 in surface pressure.
~100Kg/Cm".

A displacement sensor is attached to the cylinder 26, and the progress of the press can be grasped from the output of the sensor. That is, it can be determined that the material is filled into the cavity when the output of the displacement sensor is saturated.

At the end of pressing, the temperatures of the body mold member 20, the lower mold member 22, and the upper mold member 24 are approximately the same, and the clearance between the inner surface of the body mold member and the outer surfaces of the lower mold member and the upper mold member becomes sufficiently small.

After maintaining the press state for the appropriate time, the application of press pressure by the cylinder 26 is removed, and only the dead weight of the upper die member 24 is applied. Then, if desired, the heating of the lower mold member 22 and the upper mold member 24 by the heaters 34 and 36 is stopped, and the temperature of these mold members is set to a temperature lower than the glass transition temperature.

Next, as shown in FIG. 6, the cylinder 6 is operated to move the barrel member 20 upward. As a result, the influence of heating by the heater 32 on the optical element G2 is reduced, and as described above, the lower mold member 22 and the upper mold member 24
Coupled with the fact that the set temperature is lower than the glass transition temperature, the temperature of the optical element G2 gradually decreases. Further, the lower part of the body member 20 can be cooled by the cooler 33 if necessary. Thereby, the temperature can be set such that the optical element G2 can be taken out.

Note that in this step, heating by the heater 32 can also be stopped. According to this, the cooling time can be shortened.

Next, as shown in FIG. 7, the cylinder 26 is operated to move the upper die member 24 upward. As a result, the optical element G2 is peeled off from the upper mold member 24 and positioned on the lower mold member 22.

Next, as shown in FIG. 8, after opening the valve 46, the valve 52 is opened to introduce nitrogen gas, thereby peeling off the optical element G2 on the lower mold member 22 and blowing it away. The inside of 21b is moved to the degassed atmosphere replacement section 48.

Thereafter, the valves 46 and 52 are closed and the valve 50 is closed.
Open it and take out optical element G2. And valve 50
is closed, and the inside of the atmosphere replacement section 48 is degassed.

Subsequently, by repeating the steps shown in FIG. 3 and thereafter, the next press cycle can be performed immediately.

It should be noted that the degassing of the closed system described in connection with FIG. 3 above may be performed in the first cycle, and is not necessary in the second and subsequent cycles by always maintaining a nitrogen gas atmosphere thereafter. However, it goes without saying that the closed system may be degassed for each cycle.

Next, a specific example in which an optical lens was actually manufactured by press molding using the apparatus of the above embodiment will be shown below.

A spherical material made of optical glass SF8 (glass transition point: 445° C.) was used as the molding material.

The outer diameter of the lower mold member and upper mold member was 25 mm, and the material was MoB-based ceramics subjected to HIP treatment, with a coefficient of thermal expansion of 80 x 10-'/''C.The molding surface forming the optical surface was ground. It was finished to a predetermined shape accuracy by polishing and polishing, and the outer diameter accuracy and eccentricity were 3 μm or less.

The body member has a length of about 180 mm, and its material is TiN.
It is a type cermet with a coefficient of thermal expansion of 45X 10-'/
"C.The inner surface that slides on the lower mold member and upper mold member was machined sufficiently well, and the roundness and inner diameter variation was 1 μm.
It was within

The time required for degassing the closed system to lXl0-2 Torr and filling the closed system with nitrogen gas to atmospheric pressure is 3
It was within 0 seconds. When replacing the atmosphere in the entire molding chamber of a conventional batch-type machine for press-molding glass equivalent to that of this example, the time required for the atmosphere replacement is approximately 6 hours.
~7 minutes, which was a sufficient time reduction in this example.

The temperature conditions and results of specific press experiments are shown with reference to Table 1 below.

The temperature of the upper part of the body mold member, the temperature of the upper mold member, and the temperature of the lower mold member during standby (that is, before introducing the molding material into the mold cavity) were set as follows.

・Temperature of upper part of body part: 350℃ or 490℃.

・Temperature of upper mold member and lower mold member temperature: 250°C, 350°C or 510°C.

Immediately after introducing the molding material into the mold cavity, the temperature of the upper part of the body mold member, the temperature of the upper mold member, and the temperature of the lower mold member all reach 51.
The temperature was set at 0°C.

The preheating temperature of the molding material introduced into the mold cavity was 25°C, 300°C, or 480°C.

Then, when the temperature of the upper part of the body mold member, the temperature of the upper mold member, and the temperature of the lower mold member all exceeded 490° C., pressing was started. Press pressure is 15 per unit area of molding material
Kg, and the press pressure application time was 18 seconds.

Continuous press molding was performed 10 to several tens of times by appropriately combining the above-mentioned standby temperature of the upper part of the body mold member, temperature of the upper mold member, temperature of the lower mold member, and preheating temperature of the molding material.

The time required for the molding material to transform into its final shape is approximately 1
It was stable for 3-15 seconds.

After the molding was completed, the temperature of the upper part of the body mold member was set to the above-mentioned standby temperature. Additionally, power supply to the heaters for the lower mold member and the upper mold member was stopped.

The temperature of the lower part of the body-shaped member was about 200°C, and this part was cooled by air blowing. The molded optical element became fully removable in about 20 seconds, and was removed by blowing nitrogen gas.

After taking out the molded optical element, the power supply to the heaters for the lower mold member and the upper mold member was restarted, and the set temperature of these mold members was set to the above-mentioned waiting temperature.

The time from introducing the molding material into the mold cavity to the start of pressing, that is, the time required to heat the molding material (
1) and one cycle time (T) during continuous press molding were measured, and the quality of the molded products was also examined.

Table 1 In Table 1, "OK" indicates good condition, rNGIJ indicates conspicuous stains on the surface layer of the molded product, and rNG2--J indicates unfilled occurrence rate. This unfilled condition refers to a case where the molding material hardens without completely filling the inside of the mold cavity.

As mentioned above, the time required for each molding cycle is approximately 50 to 8
This time was 0 seconds, which was a sufficient time reduction compared to the time required for one cycle (about 1 hour) in a conventional batch type device.

From the results in Table 1 above, it was found that when the molding material was preheated to 480''C and introduced into the mold cavity, the surface layer of the molded product became stained.

This is because the surface layer of the molding material in the introduction pipe picks up dirt during transfer when introducing the molding material into the mold cavity. Therefore, it is desirable that the preheating temperature of the molding material be below the glass transition point, preferably below 400°C.

Thus, the above experiment No. 3.6, 9, 12°15.1
No. 8, 21 and 24 are comparative examples outside the scope of the present invention.

It should be noted that in Experiment No. 17 and Experiment No. 20, some unfilling occurred, but this was within an acceptable range from the viewpoint of manufacturing yield.

The above-mentioned unfilled state is caused by when the molding material is introduced into the mold cavity, it collides with the mold member and loses its spherical shape, or it is stuck to the mold member and is no longer located in the center of the lower mold member. considered to be a thing.

This unfilling occurs as the temperature of the mold member, especially the lower mold member, increases.
Furthermore, the higher the preheating temperature of the molding material, the higher the incidence. Therefore, from this point of view as well, it is desirable that the preheating temperature of the molding material is below the glass transition point, preferably below 400°C, and furthermore, the standby temperature of the lower mold member is also preferably below the glass transition point of the material, preferably 400°C. It is desirable to keep it below ℃.

On the other hand, of course, the above and T become shorter as the standby temperature of the mold member and the preheating temperature of the molding material are higher, and the press cycle can be further shortened.

In the above embodiments, the molding material has a spherical shape, but the method of the present invention also includes cases where the molding material has a shape other than a spherical shape, for example, a shape close to the shape of the final molded product.

Furthermore, in the above embodiment, a configuration is used in which a temperature distribution is imparted to the molding body member in its longitudinal direction so that when the mold cavity is closed, the cavity is located on the high temperature side. It may be in other forms.

In the above embodiment, the copper members are arranged vertically, and the lower mold member and the upper mold member are respectively arranged vertically within the body mold member, but the present invention is not limited to this. The direction of the copper members can be set as appropriate, and the lower mold member and the upper mold member do not necessarily have to be arranged one above the other as long as they are arranged slidably within the body mold member (for example, they can be arranged horizontally). This shall also include those that have been

[Effects of the Invention] As explained above, according to the method of the present invention, a molding material is introduced into a mold cavity at a temperature lower than its glass transition point, and a lower mold member and an upper mold member are formed. The mold cavity is closed by sliding the lower mold member and the upper mold member against the molding body mold member in the longitudinal direction while maintaining the interval larger than the pressing time interval, and the mold cavity is closed. The molding material is heated to a moldable temperature by the radiant heat and conductive heat from these mold members based on the heating of the lower mold member, the upper mold member for molding, and the body mold member for molding, and then the upper mold member for molding and the molding body mold member are heated. Since the lower mold member is pressed in close proximity to the lower mold member, thermal energy is used efficiently, the press cycle can be shortened, press forming can be performed continuously and repeatedly, and the equipment can be made smaller. Good quality molded products can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view showing the schematic configuration of an embodiment of a molding apparatus for carrying out the glass molding method according to the present invention, and FIG. 2 is a partially omitted partially enlarged view thereof. In this embodiment, an optical element is press-molded. FIGS. 3 to 8 are schematic diagrams to emphasize the parts that change as the operation of the apparatus of the embodiment progresses. 6.26: Cylinder, 20: Copper member, 21a: Pipe for feeding the molding material, 21b = Pipe for taking out the molded optical element, 21C: Pipe for introducing non-oxidizing gas, 21d: Pipe for degassing, 22: Lower mold member, 24: Upper mold member, 28.30
: Airtight bellows, 32.34, 36, 42a: Heater, 42.48: Atmosphere replacement part, G1: Molding material, G: Molded optical element. Agent Patent Attorney Jo Taira Yamashita Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (3)

[Claims] (1) A lower mold member and an upper mold member are accommodated in the molding body member so as to be slidable in the longitudinal direction of the molding body member, and these three mold members form the mold cavity. A method of molding glass using a glass molding device in which a molding material is introduced into a mold cavity at a temperature lower than its glass transition point, and a lower mold member for molding and an upper mold member for molding are formed. The lower molding mold member and the upper molding molding member are slid against the molding body mold member in the longitudinal direction thereof while maintaining the interval between them to be larger than the pressing time interval to close the mold cavity, and the mold cavity is closed. The molding material is heated to a moldable temperature by the radiant heat and conduction heat from these mold members based on the heating of the lower mold member, the upper mold member for molding, and the body mold member for molding, and then the molding material is heated with the upper mold member for molding. A glass forming method characterized by pressing a lower mold member in close proximity to each other. (2) The glass molding method according to claim 1, wherein a temperature distribution is imparted to the molding body member in its longitudinal direction, and when the mold cavity is closed, the cavity is positioned on the high temperature side. (3) The glass molding method according to claim 1, wherein the molding material has a spherical shape.