JP2885992B2 - Method for manufacturing optical element and apparatus therefor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing method and an apparatus for forming a high-precision optical element such as an aspherical lens by press molding. The present invention relates to a method and an apparatus for manufacturing an optical element in which a molded product is taken out of a mold.

[0002]

2. Description of the Related Art In recent years, instead of a method of processing an optical element by grinding and polishing, a heat-softened glass material is loaded into a mold, and an optical element having a required optical function surface is directly press-molded. Attention is being paid to how to secure them.

Usually, in this type of molding, a glass material in a softened state is pressed using a molding upper and lower mold member that slides in a barrel mold, and an optical member corresponding to a molding surface formed on the mold member is pressed. The functional surface was transferred to the glass material, and then cooled, and at the stage where it was cooled to a required temperature, the mold members were separated from each other, and in some cases, one of the upper and lower mold members was formed. A procedure is taken to separate the optical element from the optical element and take out the optical element.

As a method for removing an optical element from the mold, a method described in Japanese Patent Application Laid-Open No. 63-297229 is already known. In this case, a vacuum chuck provided with a mold cooling mechanism is used. A press release device of a press-formed product is used. Then, after press molding, the upper mold member is raised, and when removing the press-formed product from the mold, a vacuum chuck equipped with a mold cooling mechanism using a cooling gas is provided above the separated lower mold member. After entering, the inside of the mold is cooled, and the molded article is taken out by the vacuum suction means when the temperature of the molded article has dropped to a predetermined temperature.

[0005]

However, in the above-mentioned conventional example, the lower mold member and the molded product are often in close contact with each other even after the upper mold member is raised after the press molding is completed. The temperature at which the close contact is released is greatly influenced by a slight change in the interface between the mold and the molded product. Therefore, conventionally, including the case of the conventional example, in order to ensure stable mold release, always, to a certain temperature to allow for safety, or cooling for a certain time or more to allow for safety,
This must be performed on the mold, and excessive cooling is performed below the temperature required for actual release. As a result, there is a problem that extra time is required to elevate the temperature of the molding die to a pressing temperature required for the next molding, and the molding cycle time becomes long.

[0006]

For this reason, the present inventors have conducted a sincere study on an appropriate removal temperature of a molded article from a molding die, and as a result, the viscosity of the molded article has a temperature corresponding to 10 ¹⁶ poises from around the glass transition point. A large number of products can be removed from the mold in the range, and the molded product that is in close contact with the lower mold member in the above temperature range is also brought into close contact by raising and lowering the temperature of the mold member and the molded product in the vicinity of the temperature. I realized that I could release my strength.

The present invention has been made in view of the above research results, and when removing a molded article from a molding die, the molded article can be reliably taken out, and the mold temperature is lowered more than necessary. An object of the present invention is to provide a method and an apparatus for manufacturing an optical element in which the time spent for raising the temperature of a molding die during the next molding is reduced as much as possible and an efficient molding cycle is achieved.

[0008]

For this reason, in the manufacturing method of the present invention, a glass material is loaded into a molding die, press-molded at a required temperature, and an optical function is applied to the glass material from the molding surface of the molding die. In the method for producing an optical element having a surface transferred, a step of taking out a molded optical element from a mold within a range of a glass viscosity and a temperature corresponding to 10 ¹⁶ poise from the vicinity of the glass transition point; Detecting whether the element has been removed from the mold, controlling the temperature of the mold within a required range if the element has not been removed, and then returning to the removal step.

Further, in the manufacturing apparatus of the present invention, the glass material is loaded into a mold, press-molded at a required temperature, and the optical function surface is transferred from the molding surface of the mold to the glass material. In an optical element manufacturing apparatus, a unit for removing a molded product from the molding die after press molding with the molding die, a unit for detecting that the molded product has been removed, and heating, maintaining and / or cooling the molding die Means to
Control means for controlling the heating, temperature holding and / or cooling means according to a required time schedule, and arithmetic means for identifying a signal output from the detection means and issuing a command to the control means. ing.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 shows a state in which a glass material is charged into a molding die, press-molded, and then subjected to a predetermined temperature (10 ^{15 in} terms of glass viscosity).
At a temperature equivalent to 〜１０10 ¹⁶ poise)
FIG. 3 schematically shows a state immediately before a molded product 5 is removed from a molding die. In this example, the molding die forms a through hole vertically penetrating in a body die 1 arranged on a bottom plate 4, and an upper portion thereof is formed. The upper mold member 2 and the lower mold member 3 are slidably fitted to the lower part, respectively.
Molding surfaces 2a and 3a corresponding to the optical function surface of the optical element to be molded are provided on the lower surface and the upper surface, respectively.

The body mold 1 has heaters 6a, 6b for heating the upper mold member 2 and the lower mold member 3;
And 6c and 6d, and an opening 1a is provided for taking out the molded article 5 and inserting the glass material.

Further, a suction hand 11 is provided outside the molding die, and a hand driving device (not shown) is provided.
Thus, the glass material can be moved in each direction shown by the arrow A, and the insertion of the glass material and the removal of the molded product 5 can be performed. The suction hand 11 is provided with a suction surface 12 and a suction suction passage 13 communicating with the suction surface 12 for suction of the glass material and the molded product 5. The suction passage 11 is provided with a spool-type electromagnetic solenoid for suction control. It is connected to a vacuum source (not shown) via a valve 25. Further, a pressure sensor 21 is provided in the middle of a pipe connecting the suction passage 13 for suction and the solenoid valve 25.

The pressure signal from the pressure sensor 21 is
The signal is supplied to a computing unit 22 via a signal line 31. At this pressure level, it is determined whether or not the suction hand 11 is in a suction state. A control signal from the computing unit 22 is guided to an operation controller 23 via a signal line 32. From the operation controller 23, an operation control output for controlling the solenoid valve 25 is transmitted via a power line 34. An operation control output that is supplied and drives another device driving mechanism (not shown)
The power is supplied via a power line 35. The computing unit 22
Thereafter, a control signal for controlling the temperature of the molding die is output to the temperature controller 24 via the signal line 33.

From the temperature controller 24, the heaters 6a, 6b, 6c, 6c
Electric power for heating d is supplied, and a control output is supplied to the cooling electromagnetic valve 26 via the power line 37. The cooling electromagnetic valve 26 is supplied with a N ₂ gas as a cooling medium from a supply source (not shown). When the N ₂ gas is opened, the N ₂ gas is supplied to the molding die via an N ₂ introduction pipe 7. N ₂ gas can be supplied. Note that the N ₂ inlet pipe 7, as illustrated, middle, respectively, are divided into an upper mold cooling pipe 7a and the lower mold cooling pipe 7b. The upper mold cooling pipe 7a is provided with a cooling hole 2 provided in the upper mold member 2.
b, the lower mold cooling pipe 7b communicates with a cooling hole 3b provided in the lower mold member 3, respectively. A thermocouple 38 is embedded in the mold,
The temperature of the mold is detected, and a detection signal is supplied to the temperature controller 24 to switch the control output of the temperature controller 24.

In this embodiment, the temperature of the entire molding die is controlled by one temperature controller. However, a plurality of temperature controllers, thermocouples, solenoid valves for cooling, and the like are provided to form the molding die. It is more preferable to separately control the upper and lower mold members from the viewpoint of maintaining a high temperature accuracy for each of the upper and lower mold members.

FIG. 2 shows an example of a temperature control program pattern incorporated in the temperature controller 24. In this example, a temperature required for a step of taking out a molded product is set for each step. The heaters 6a, 6b, 6c, 6 are set so that the mold has the set temperature.
d and the cooling electromagnetic valve 26 is controlled. The selection of each step is performed based on the temperature information output from the temperature controller 24, the operation information output from the operation controller 23, and the pressure signal output from the pressure sensor 21. Made in. FIG. 2 shows the basic ON of heating and cooling of the mold.
Although the -OFF state is shown, in practice, the temperature is preferably controlled by adopting a more advanced PID control without being limited to this.

FIG. 3 is a flow chart showing a specific example of the flow of the logic circuit of the arithmetic unit 22 when removing the molded product 5 from the molding die. here,
When the cooling of the molded article 5 is completed, the counter for counting the number of repetitions of the take-out operation (hereinafter, referred to as “retry”) is reset (n = 0), and the upper mold member 2 is raised, and FIG. The state is as shown in the figure. Thereafter, the suction hand 11 enters the opening 1a of the body die 1 and descends to suck the molded product 5 and rise. Here, if the molded product 5 is adsorbed on the suction surface 12 of the hand 11, the entrance of the suction suction passage 13 is closed, and the pressure of the suction passage 13 is greatly reduced. If the molded product 5 is not adsorbed, the pressure in the intake passage 13 does not decrease as much as the difference. The pressure at this time is detected by the pressure sensor 21 in FIG. 1, and the computing unit 22 determines whether or not the suction is performed. In the flow of FIG. 3, the pressure value, which corresponds to “adsorption OK” and serves as a criterion for determination, is determined by the shape, glass type, and the like of the molded product to be molded. Here, when it is determined that the suction is being performed, the suction hand 11 retreats, removes the molded product 5 from the molding die, moves to a molded product storage table (not shown), where the molded product 5 is removed. The suction is released and the molded product 5 is lowered. Further, the temperature controller 24
Receives a command to shift to step 1 in FIG. 2 from the computing unit 22, and enters a heating step for the next molding. Conversely, when it is determined that the suction is not being performed, once the temperature of the molding die is reduced by the intake air, dust is prevented from flowing around the molding die, and the intake line is prevented from being damaged by the continuous intake of the heating fluid. Then, the suction is released. Further, the number of retries is counted by the counter (n = n + 1). 1
At the second time, when the removal of the molded article was not executed,
n = 1, and the arithmetic unit 22 switches to the temperature controller 24
Then, a command to move to step 4 in FIG. 2 is issued, and the mold is controlled to the set temperature in step 4. Thereafter, after a certain period of time or after reaching a predetermined temperature, the suction hand 11 is lowered again and a retry is performed. When it is determined that suction has been performed in the first retry, as described above, the suction hand 11 retreats, the molded product 5 is taken out of the molding die, and the next molding is performed. If it is determined that suction has not been performed in the first retry,
Again, the adsorption is released, 1 is added to the counter, and n = 2, and the arithmetic unit 22 issues a shift command to the temperature controller 24 to step 5 in FIG.
The temperature of the mold is controlled toward the set temperature in step 5. Similarly, when it is determined that suction has been performed at the n-th retry, as described above, the suction hand 11 retreats, the molded product 5 is taken out of the molding die, and the next molding is performed. When it is determined that the suction is not performed at the n-th retry, the suction is released again, 1 is added to the counter, and n = n + 1. The temperature is controlled from the computing unit 22 to the temperature controller 24 so that the molding die is set to the set temperature in that step. The set temperature of the mold according to the number of retries and the heating / cooling state of the mold in this embodiment are as shown in FIGS.
When the number of retries is 1, the set temperature is 500 ° C,
Since the set temperature in cooling is 500 ° C., the mold is kept warm. Similarly, when the number of retries is two or three, the set temperature is 450 ° C. and the cooling state is set, and when the number of retries is four, the set temperature is 500 ° C. and the heating state is set and the number of retries is five to seven. The temperature is 400 ° C, the cooling state is reached, and the set temperature when the number of retries is 7 to 9 is 400 ° C
Then, it is kept warm. Further, when the number of retries reaches 10, the computing unit 22 determines that the molded product cannot be removed from the molding die, issues an alarm to the outside, stops the system at the same time, and stops molding. This is a measure to cope with the case where the molded product cannot be taken out due to breakage of the molded product, fusion of the molded product to the molding die, abnormality of the apparatus, and the like. Further, the retry does not need to be performed at the set temperature in each step, and may be performed during the temperature control for the set temperature as seen in this embodiment.

Next, the step of molding an optical element using the above-described system will be specifically described with reference to FIG. The optical element molded here is an aspherical lens having a diameter of 14 mm used for cameras, video cameras, and the like.
The glass material used for this was 10 when the temperature was 620 ° C.
It is SK12 having a viscosity characteristic such that the glass viscosity becomes ^9.5 poise, 10 ¹³ poise at 534 ° C., and 10 ¹⁶ poise at 480 ° C. The molding was performed in a closed furnace in an N ₂ gas atmosphere to prevent oxidation of the mold.

The solid line shown in FIG. 4 shows the temperature cycle of the mold when the molding is continuously performed by using the manufacturing method according to the present invention, and the broken line shows the conventional manufacturing method (constant temperature 32).
(The molded product is taken out at 0 ° C.).

First, when the manufacturing apparatus is operated and the molding process is started, the temperature controller 24 proceeds to step 1 according to a command from the arithmetic unit 22, and the molding die is pressed from room temperature (20 ° C.). Toward the temperature of 620 ° C, 5
Heat at a heating rate of 0 ° C./min. Simultaneously, in response to a command from the computing unit 22, the operation controller 23 moves an equipped device driving mechanism (not shown) to lift the upper mold member 2 and insert the glass material onto the lower mold member 3. .

Next, the thermocouple 3 embedded in the molding die
8, when it is detected that the temperature of the mold reaches 620 ° C., a temperature reaching signal is output from the temperature controller 24 to the arithmetic unit 22, and further, when the arithmetic unit 22 receives the temperature reaching signal, This time, on the contrary, a command to shift to step 2 is issued from the arithmetic unit 22 to the temperature controller 24, and
The temperature is maintained at 20 ° C., and at the same time, a command to start pressing is issued from the arithmetic unit 22 to the operation controller 23, and pressure is applied to the upper mold member 2 by a pressing mechanism (not shown) to start pressing.

After one minute has elapsed from the start of the press, a command to shift to step 3 is issued from the arithmetic unit 22 to the temperature controller 24, and the output to the heaters 6a, 6b, 6c, 6d is stopped. At the same time, the cooling electromagnetic valve 26 is excited,
The mold is cooled at a cooling rate of 50 ° C./min.

When the temperature of the mold reaches 500 ° C., a temperature attainment signal is output from the temperature controller 24 to the computing unit 22 in the same manner as at the start of pressing, and based on the signal, the computing unit 22 is operated. Then, a command to remove the molded product 5 is issued to the operation controller 23. Then, in response to a signal from the operation controller 23, the device driving mechanism is operated, the upper die member 2 is raised, and the suction hand 11 enters the body-shaped opening 1a to perform suction. In this case, since the molded product 5 was not sucked by the suction hand 11 and the pressure did not drop below the set value for confirming the suction, the computing unit 22 also determined that suction was not performed, and The excitation of the valve 25 is stopped, the first retry is started, and a command to shift to step 4 is issued to the temperature controller 24. As a result, the temperature of the mold becomes 500
It is kept at ° C.

Here, 30 seconds after the temperature of the mold was maintained at 500 ° C., suction was performed again. As a result, no suction was performed. 24 receives a command to shift to step 5, and the mold starts cooling at 450 ° C. at a cooling rate of 50 ° C./min. As in the case of the first time, 30 seconds after the start of cooling, when the temperature of the mold is about 475 ° C., the suction is performed again. As a result, the suction is not performed here, so the third retry is started. . Since the command to the temperature controller 24 remains at step 5, similar to the second retry,
The mold continues to cool at a cooling rate of 50 ° C / min to 450 ° C. Then, after 30 seconds, when the temperature of the mold is about 450 ° C., the suction is performed again. Here, the suction is performed, and the take-out is successful. The time required up to this time was 17 minutes and 7 seconds, including the time required for the mold to rise from room temperature, as shown in FIG. In addition, the black circle on the solid line in FIG. 4 indicates a place where the suction operation is performed.

Immediately after taking out the molded product of the first shot, the next glass material is inserted into the molding die in accordance with a command from the arithmetic unit 22, and heating of the molding die for the molding of the second shot is started. The initial temperature of the mold at the start of this heating is
As is clear from FIG. Below, 1
After performing the same process as the shot, and taking out the molded product after completion of cooling, this time, without retrying,
I was able to take it out smoothly. The time required for molding at this time was 7 minutes and 28 seconds including the time for inserting the glass material.

In the molding of the third shot, the heating of the mold was started at a temperature rise from 500 ° C., and the molded product was taken out through the same steps as in the previous shot. The adhesion state is strong, and in addition to the retry operation similar to the first shot, once from 450 ° C to about 475 ° C
After heating for about 30 seconds, the molded article was successfully taken out for the first time after cooling to about 450 ° C. for about 30 seconds. The number of retries at this time was 5 times, and the time required for molding was 9 minutes and 19 seconds.

Thereafter, the number of retries is 0, 0, and 1 and so on. In the seventh shot, the number of retries is 6, and the time required for molding is 9 minutes and 53 seconds. The molding could be completed in a much shorter time than the conventional molding time of 13 minutes and 40 seconds indicated by the broken line.

In this experiment, when the molding was further continued after that, as shown in FIG. 4, the occurrence of retries showed a tendency to gradually decrease. However, regardless of the number of molding shots, the retries suddenly occurred. Occurring states are frequently observed.

Table 1 below shows the case where 100 shots were continuously formed by taking out at a constant temperature and the case where 100 shots were continuously formed by taking out by the method of the present invention. About FIG.
The results obtained when the molding was performed 10 times each under the same molding conditions as those shown in FIG.

[0030]

[Table 1] As shown in Table 1, when continuous molding was performed using the conventional take-out method, 100 shot continuous molding was achieved only three times out of ten times, and in the worst case, At the 5th shot, the molded product and the mold come into close contact,
It was impossible to remove the molded product. Usually, in such a case, it is necessary to stop molding and forcibly remove the molded product from the mold using tweezers or the like, but in order to prevent oxidation of the mold, perform molding in an N ₂ gas atmosphere. Therefore, it is necessary to further lower the temperature to near room temperature, release the atmosphere to the atmosphere, and then take out the molded product. Therefore,
If a state occurs in which it is impossible to remove the molded article in the middle, the cooling time for manually removing the molded article and the heating time accompanying it are added to the normal molding time. (1) The average molding time per piece becomes longer than expected, and a worker for taking out is required, so that it is practically impossible to perform efficient unattended automatic molding. This became clear in the above experiment.

In comparison, the results obtained by using the method according to the present invention show that the molded article cannot be taken out even after 100 shots of continuous molding are performed 10 times, as is clear from Table 1. In the conventional method, even when the temperature cannot be taken out even if the temperature is excessively lowered, once the temperature is raised and lowered, the adhesive force generated between the molded product and the mold is released. In all cases, the molded product was automatically removed within 7 retries. Further, in this case, in Table 1, the average molding time per one shot was approximately half of the conventional time. In this example, for the purpose of comparison, continuous molding was discontinued at 100 shots. However, it is considered that continuous molding can be performed substantially without limit for taking out a molded product. It is possible to greatly improve the operation efficiency and achieve unmanned automatic continuous molding.

In this embodiment, the pressure sensor is used for detecting the suction. However, other detecting means such as a photo sensor is used.
It may be performed by a mechanical chuck means or the like. Further, in the present embodiment, the arithmetic unit, the operation controller, and the temperature controller each have an independent configuration. However, using a computer or the like, a similar circuit or system is configured by software. , May be implemented. Further, in this embodiment, the atmosphere for molding is also N ₂ gas atmosphere for the purpose of protecting the mold. However, the atmosphere is not limited to N ₂ gas. If protection is not required, it goes without saying that the same effect can be obtained even when the molding is performed in an atmosphere necessary for the molding, such as molding in the air. In this embodiment, the take-out temperature is set to 500 ° C. (about 10 ¹⁵ poise in terms of glass viscosity), but this temperature greatly depends on the glass type, mold material, shape, and the like. It is also possible to raise the transition point temperature without adverse effects. Further, in this embodiment, the retry timing is controlled by time, but the retry timing can be determined based on the temperature information of the molding die.
It goes without saying that the same effect can be obtained.

[0033]

As described above, according to the present invention, the operation of taking out a molded article from a mold and the temperature of the mold are linked to give an arbitrary temperature cycle of heat retention, cooling and heating to the mold. By repeating the take-out operation as many times as necessary, the viscosity of the glass can be reduced by 10 ¹⁶ from the glass transition point.
In a high temperature range corresponding to poise, a molded product can be reliably taken out, and the time required for molding can be significantly reduced. In addition, an excellent effect of obtaining an optical element from a glass material by press molding with extremely high production efficiency without manpower is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view of a take-out system showing one embodiment of the present invention.

FIG. 2 is a diagram of one embodiment of a temperature control program for a molding die used in the present invention.

FIG. 3 is a flowchart of one embodiment showing a flow of a logic circuit used in the present invention.

FIG. 4 is a temperature cycle diagram of a comparative example showing a temperature cycle of a mold according to a conventional removal method and a removal method according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 body mold 2 upper mold 3 lower mold 5 molded product 11 take-out hand 21 pressure sensor 22 arithmetic unit 23 operation controller 24 temperature controller 25 suction control solenoid valve 26 cooling solenoid valve

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C03B 11/16

Claims (4)

(57) [Claims] 1. A method of manufacturing an optical element, comprising loading a glass material into a molding die, press molding at a required temperature, and transferring an optically functional surface from the molding surface of the molding die to the glass material. A removal step of removing the molded optical element from the mold, detecting whether or not the optical element has been removed from the mold, controlling the temperature of the mold within a required range if not removed, And a step of returning to the take-out step. 2. The method according to claim 1, wherein when controlling the temperature of the mold up and down within a required range, the mold is alternately cooled, maintained at a constant temperature and / or heated on a required schedule. A method for manufacturing the optical element according to claim 1. 3. An apparatus for manufacturing an optical element, wherein a glass material is loaded into a molding die, press-molded at a required temperature, and an optical functional surface is transferred from the molding surface of the molding die to the glass material. Means for removing the molded article from the mold after press molding in the mold, means for detecting that the molded article has been removed, means for heating, maintaining temperature and / or cooling the mold, Temperature holding and / or
An optical element comprising: a control unit that controls a cooling unit according to a required schedule; and a calculation unit that identifies a signal output from the detection unit and issues a command to the control unit. Manufacturing equipment. 4. The apparatus for manufacturing an optical element according to claim 3, wherein a vacuum suction is used for said take-out means.