JP2954427B2 - Glass forming method - Google Patents

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 in which a glass material is put between a pair of forming mold members, and the glass material is heated to form a glass molded product with the pair of forming mold members. Things.

[0002]

2. Description of the Related Art In recent years, as a method of processing an optical element such as a glass lens, a method of press-molding a heat-softened glass material using a pair of upper and lower molding dies has attracted attention instead of a method of grinding and polishing. When an optical element such as a glass lens is processed by press molding in this manner, first, a glass material is supplied between upper and lower mold members, and the pair of mold members are moved in a direction of approaching each other to form a glass. Press the material. After the pressing step is completed, the glass material is cooled and cooled to a predetermined temperature, and then the molded optical element is taken out of the pair of mold members by an automatic hand or the like.

Here, in the conventional method of processing an optical element by molding, for example, Japanese Patent Laid-Open No. 1-2
As disclosed in JP-A-57140 and JP-A-3-55419, when the process shifts from the step of pressing the glass material to the step of cooling, the timing is determined by the elapsed time from the start of pressing. Had been decided.
That is, in the step of pressing the glass material, a time period from when the molded article is started to be pressed under a predetermined press pressure until the molded article is completely pushed is set, and after the set time has elapsed, the process is switched to the cooling step. I was

[0004]

However, when the time from the start of the press to the end of the press is set to a certain time and the cooling process is started after the elapse of the certain time, the press from the start of the press to the press The time up to the end varies depending on variations in the shapes of the individual pressing mold members and glass blanks. Therefore, it is necessary to set the set time from the start of the press to the end of the press to be longer in view of a margin enough to absorb the variation.

If the time from the start of the press to the end of the press is set to the last minute, in some cases, the process shifts to the cooling step before the glass material is completely pushed out (before the press is completely completed). It is possible that As described above, when the process shifts to the cooling step in a state where the glass material cannot be completely pushed out, not only the completed optical element such as a glass lens cannot be finished to a desired thickness, but also the inclination of the optical axis and the like can be reduced. Occurs, and the optical performance of the optical element is greatly reduced.

Therefore, the set time from the start of the press to the end of the press must be set to be longer than the time actually required for the press operation, and if the same lens is mass-produced, the tact time is reduced. However, there is a problem that the production efficiency is reduced. on the other hand,
If the pressure applied to the glass material becomes zero after the pressing process is completed, the shape accuracy of the optical function surface transferred to the glass material will decrease if the mold and the glass material have good release properties. May be. Therefore, there has been proposed a method in which a small press pressure is applied to the glass material when the process moves to a cooling step after the mold member is pressed and the press is completed, thereby preventing the deterioration of the shape accuracy of the glass lens.

[0007] In view of this point, as described above, if the time from the start of the press to the end of the press is set longer,
A time lag occurs between the time when the mold member is completely pushed and the time when cooling is started, and during this time lag, the glass material is left unloaded and the finished lens There is a problem that the shape accuracy is deteriorated. Therefore, reducing the time lag from the end of pressing to the start of cooling not only prevents the tact time from becoming long, but also improves the shape accuracy of the completed lens.

On the other hand, apart from the above-mentioned problems, when molding an optical element such as a glass lens, it is important to finish the optical functional surface with high precision and to finish the wall pressure with high precision. As a method for precisely finishing the optical function surface of the optical element as described above, Japanese Patent Application Laid-Open No.
As disclosed in Japanese Patent Publication No. 27, when the optical element becomes thick in anticipation of the amount of shrinkage to the glass transition temperature upon cooling, the press pressure is reduced to lower the temperature, and the maximum pressure is applied near the glass transition point. There is known a method of improving the surface transfer property by reducing the pressing force at the time when a desired thickness is obtained, gradually cooling to a transition point, and further cooling.

As a method for accurately finishing the wall pressure of an optical element, as disclosed in Japanese Patent Application Laid-Open No. 61-136927, after the thickness deformation speed of a molded product becomes a predetermined speed or less. There is known a method of forming an optical element to a desired thickness by increasing a pressing force. In the former method among the above conventional examples, when detecting the position of the mold member when the temperature is lowered by weakening the pressing force, the detection position varies in the micron order due to the thermal expansion of the mold and the press rod. Will happen. Then, since the maximum pressure is applied so as to absorb the variation near the glass transition point, there is a problem that the thickness variation increases.

Further, in the latter method among the above-mentioned conventional examples, since a large pressure is applied to a place where the deformation speed is lowered, an excessive force is applied to the glass member,
There were problems such as fusion of the glass to the mold member, deformation of the mold member, and cracking of the molded product. Accordingly, the present invention has been made in view of the above-mentioned problems, and a main object of the present invention is to provide a glass forming method capable of shortening a molding tact time and improving productivity.

Another object of the present invention is to provide a glass forming method capable of improving the shape accuracy and the thickness accuracy of the optical function surface of a molded product without applying excessive force to the molded product. It is.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and achieve the object, a glass forming method of the present invention comprises placing a glass material between a pair of forming mold members and heating the glass material. In a glass forming method for forming a glass molded product with the pair of forming mold members in a state in which the molding is performed, a pressing step of closing the pair of mold members and transferring a molding surface of the mold member to the glass material, A detection step of detecting the approach speed of the pair of mold members, and a state in which the approach operation of the pair of mold members is substantially completed when the approach speed detected in the detection step is 1 μm / sec or less. And a transition step of immediately judging the press-off state and immediately transitioning the mold member to a cooling step.

Further, in the glass forming method according to the present invention, in the pressing step, one of the pair of mold members is moved closer to the other mold member that does not move. First for glass materials
Is applied, and in the cooling step, the other mold member is moved closer to the one mold member whose movement has been completed, whereby the second
Is applied.

Further, in the glass forming method according to the present invention, the second pressing pressure P2 is set so as not to exceed the first pressing pressure P1 in the initial stage of P2 application in the cooling step. Is characterized by being gradually increased without being limited to P1.

[0015]

[0016]

As described above, the glass forming method according to the present invention is constituted, so that by detecting the moving speed of the mold member and starting cooling based on the detected moving speed, the tact time of forming can be shortened, and the productivity can be reduced. Can be improved.

Further, by applying a pressing pressure to the glass material at the time of cooling, it is possible to prevent the accuracy of the shape of the optically functional surface from being lowered, and by gradually increasing the pressing pressure in the cooling process, When the temperature of the initial glass material is high, an excessive pressing pressure is not applied to the glass material, so that the glass material is not deformed more than necessary and the wall thickness accuracy can be improved.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing a configuration of a molding die 12 to which the optical element molding method according to one embodiment is applied. FIG. 1 shows a configuration of a molding die 12 for molding a convex lens.
And the pressing operation of the glass material 40 by the lower mold member 18 is completed, and the molding of the glass lens is substantially completed.

In FIG. 1, a body mold 14 constituting an outer shell of a molding die 12 is placed on a molding apparatus main body 10 of an optical element via a support substrate 20. The body mold 14 is formed in the shape of a prism having a substantially square shape when viewed from the top, and a through hole 14
a is formed. Above the through hole 14a, an upper mold member 16 formed in a columnar shape is slidably inserted along the up and down direction in a fitted state. A disc-shaped flange portion 16a is formed at an upper end portion of the upper die member 16, and the lower surface of the flange portion 16a comes into contact with the upper surface 14c of the trunk die 14 from above through the spacer 17, whereby the upper portion is formed. The mold member 16 is prevented from moving further downward, thereby defining a downward press stroke of the upper mold member 16. Also, the upper mold member 1
On the lower surface of 6, a molding surface 16b for pressing the glass material 40 and transferring a desired shape to the surface to form an optical function surface is formed.

An air cylinder 22 for generating a pressing pressure applied to the glass material 40 is disposed above the upper mold member 16 while being supported by a support member (not shown). A piston rod 22a is disposed below the air cylinder 22 along the up-down direction, and a lower end of the piston rod 22a is connected to an upper end surface of the upper die 16. Accordingly, when the air cylinder 22 is operated and the piston rod 22a is pushed downward, the pressing pressure P1 is applied to the glass material 40.
Is applied.

Also, beside the piston rod 22a,
A protrusion 22b is formed, and the protrusion 22b
As the piston rod 22a moves downward, it comes into contact with the tracing stylus 28a of the displacement sensor 28 arranged on the side of the piston rod 22a. Projection 22
b comes into contact with the upper end of the stylus 28a,
Of the piston rod 22a.
Is measured by the displacement sensor 28.

The displacement sensor 28 is connected to an arithmetic unit 30 for calculating the moving speed of the piston rod 22a from the output signal of the displacement sensor 28. The arithmetic unit 30 controls the operation of the entire forming apparatus. Connected to a controller 32 for performing the operations. Since the displacement sensor 28 needs to perform position measurement in units of microns, a highly accurate linear sensor or the like is used.

On the other hand, a lower mold member 18 formed in a columnar shape like the upper mold member 16 is slidably inserted in the vertical direction in a fitted state below the through hole 14a. I have. A disc-shaped flange portion 18a is provided at a lower portion of the lower mold member 18.
Are formed, and the lower surface 18c of the flange portion 18a is formed.
Is in contact with the upper surface of a support substrate 20 on which the body mold 14 is placed via a spacer 19. The support substrate 20 is configured to receive a downward pressing pressure P1 applied to the lower mold member 18 from the upper mold member 16 via the glass material 40. On the upper end surface of the lower mold member 18, a molding surface 18b for transferring a desired shape to the lower surface of the glass material 40 to form an optical function surface is formed.

Accordingly, on the upper surface of the glass material 40, an optical function surface 40a on which the surface shape of the molding surface 16b of the upper die member 16 is transferred is formed, and on the lower surface, the molding surface 18b of the lower die member 18 is formed. The optical function surface 40b to which the surface shape is transferred is formed. As described above, the thickness of the formed convex lens (glass material 40) is such that the lower surface of the flange portion 16a of the upper die member 16 is
The thickness of the convex lens (40) does not change each time it is processed.
In addition, if the spacer 17 is replaced with one having a different thickness, the thickness of the convex lens (40) can be adjusted.

An air cylinder 24 is fixed to the lower surface of the molding apparatus main body 10.
The piston rod 24a is connected to the lower surface 18c of the lower die member 18 via a through hole 10a formed in the molding apparatus body 10 and a through hole 20a formed in the support substrate 20 in order. The air cylinder 24 is provided with a lower mold member 18 in order to prevent the shapes of the optical functional surfaces 40a and 40b of the convex lens (40) from being collapsed in a cooling process after the molding operation of the convex lens (glass material 40) is completed. Is pushed upward to apply a pressure P2 to the convex lens (40).

On the other hand, an opening hole 14d
Is formed, the glass material 40 is supplied into the molding die 12 through the opening hole 14d, and the convex lens (40) whose molding has been completed is taken out of the molding die 12. In addition, on both sides of the body mold 14, the body mold 14, the upper mold member 16 and the lower mold member 18 are heated in a state where they are arranged vertically, and the body mold 14, the upper mold member 16 and the lower mold 16 are heated. A heater 26 for heating the glass material 40 via the member 18 is provided.

Next, the molding die 12 constructed as described above is used.
The general procedure for molding a convex lens will now be described.
First, the upper rod 16 is slid upward with respect to the body die 14 by retracting the piston rod 22 a of the air cylinder 22, and is released from the lower die 18. In this state, the glass material 40 heated to a predetermined high temperature is supplied onto the molding surface 18b of the lower mold member 18 by an automatic hand or the like through the opening hole 14d of the body mold 14. When a convex lens is formed, the glass material 40 supplied at this time is formed into a spherical shape or a shape close to the completed shape of the convex lens. The body mold 14, the upper mold member 16 and the lower mold member 18 are
To a temperature corresponding to a predetermined molding condition.

After the glass material 40 has been supplied onto the molding surface 18b of the lower mold member 18, the piston rod 22a of the air cylinder 22 is pushed out, and the molding surface 16b of the upper mold member 16 is placed on the upper surface of the glass material 40. To apply a press pressure P1 to the glass material 40. This press pressure P
When 1 is applied and the upper mold member 16 gradually moves downward, the glass material 40 is gradually crushed in the horizontal direction, and finally, the state shown in FIG. 1 is obtained. In this state, optical function surfaces 40a and 40b on which the shapes of the molding surface 16b of the upper mold member 16 and the molding surface 18b of the lower mold member 18 are transferred are formed above and below the glass material 40, respectively. The thickness of the glass material 40 is formed to a desired thickness.

Thereafter, the formed convex lens (glass material 40) is gradually cooled. In this cooling process,
The air cylinder 24 is actuated to push up the lower mold member 18 so that the shape of the formed convex lens (40) does not collapse, and a pressure P2 is applied to the convex lens (40) from below. Then, when the temperature drops to a predetermined temperature, the air cylinder 22 is again drawn in, and the upper mold member 16 moves upward. This convex lens is moved by an automatic hand or the like.
It is taken out through the opening hole 14d of the body mold 14.

The above is a schematic operation for forming the convex lens (40). Next, as a specific example, a case where a glass material SK12 is used as the glass material 40 and a biconvex lens having an outer diameter of φ14 is formed will be described. I do. First, the upper mold member 16 and the lower mold member 18 are heated by the heater 26 via the body mold 14.
Is heated to a pressing temperature of 630 ° C. During the temperature rise of the mold member at this time, the glass material 40 is placed on the molding surface 18b of the lower mold member 18 and the glass material 40 is heated together with the mold members 16 and 18. Glass material 4
When the temperature of 0 became approximately 600 ° C., the piston rod 22a of the air cylinder 22 was pushed out, and
Pressing of the glass material 40 is started with a pressing pressure of P1 = 300 kg. Then, the flange portion 16 of the upper die member 16
The pressing step is completed when the lower surface of “a” comes into contact with the upper surface of the spacer 17 (pushed out state).

Here, the flange portion 16a of the upper die member 16
The output of the displacement sensor 28 is used to detect that the lower surface of the spacer abuts on the upper surface of the spacer 17 and is completely pushed out. As described above, the displacement sensor 28 is configured such that the tracing stylus 28a provided at the upper end thereof
The vertical position of the piston rod 22a is detected by being pushed up and down by the protrusion 22b provided on the 2a. The displacement signal output from the displacement sensor 28 is
Input to the arithmetic unit 30, the arithmetic unit 30 calculates the downward moving speed of the piston rod 22a from the displacement signal. The calculation result of the moving speed is sent to the controller 32.

In this embodiment, when the downward moving speed of the piston rod 22a becomes 1 μm / sec, it is determined that the upper die member 16 has been pushed completely. When the controller 32 determines that the upper mold member 16 has been completely pushed, the controller 32 immediately stops heating the heater 26, shifts to a cooling step of cooling the mold member by a cooling means (not shown), and pushes out the air cylinder 24. By operating, a pressing pressure P2 is applied to the convex lens (glass material 40) from below. In addition,
The cooling rate by the cooling means at this time is -50 ° C / mi.
n.

The pressing pressure P2 is set at 50 kg in the initial stage of the cooling process, and thereafter is gradually increased with the lapse of time to 200 kg when the mold member is cooled to 590 ° C. It has become. Thereafter, the value of the pressing pressure P2 is maintained at 200 kg until the temperature of the mold member drops to 530 ° C. When the temperature of the mold member has dropped to 530 ° C., the operation of the air cylinder 24 is released, and the cooling process is continued to open the mold when the temperature of the mold member reaches 500 ° C.
Take out the molded product.

The convex lens (4
0) indicates that the surface accuracy is about 4 to 5 Newton rings,
In the same way, the habit was processed with good accuracy, with less than one Newton ring, the inclination of the optical axis being less than 50 ″, and the thickness variation being less than 5 μm. However, in this example, it was shortened to 60 seconds.

As described above, according to the present embodiment, since the cooling process is started immediately after the press-out state is detected, it is not necessary to set the press time in advance, and it takes more press time than necessary. Since there is no necessity, the molding tact time is shortened. In addition, it is possible to perform molding in accordance with variations in the weights of the respective molds and blanks, and the thickness accuracy, the inclination accuracy of the optical axis, and the like are reliably ensured.

Further, immediately after the press is completely pushed out, the pressure P
Since 2 is added to the molded product, the surface accuracy must be improved because the mold and the glass material are always in close contact with each other in the cooling process, especially in the case of a combination with good mold release properties between the mold member and the glass material. Can be. In addition, since the pressing pressure at the time of cooling is applied to the glass material by the mold member opposite to the mold member moving in the pressing process, continuous pressing can be performed immediately after the pressing process is completed, The shape accuracy of the product can be improved. Also, during the press,
Since the molded product is once mechanically pushed, the thickness of the molded product at this time is once assured, and a molded product with a desired thickness can be easily obtained. Also, when mechanically pushed out,
Since the inclination of the upper mold member is corrected by the flange portion of the upper mold member abutting on the spacer, the inclination accuracy of the optical axis of the molded product is reliably ensured.

Further, in a state in which the glass material is at a high temperature immediately after the pressing, the pressing pressure P2 is set to a low value, and the value of P2 is increased as the temperature of the glass material decreases. Further, the glass material is not deformed more than necessary in a high temperature range, and the final wall pressure of the molded product can be stabilized. Further, by applying the pressing pressure P2 to the glass material in this manner, it is possible to prevent the mold member and the glass material from peeling off during the transfer of the optical function surface shape,
A molded product having a highly accurate surface shape can be obtained.

It should be noted that the present invention can be applied to a modification or modification of the above embodiment without departing from the gist of the invention. For example, in the above embodiment, the cooling process is described to start immediately when the upper die member is completely pushed.However, when forming a thick lens, the temperature distribution in the lens immediately after pressing is uniform. After a certain period of time, the process may shift to the cooling step. Thus, the temperature distribution during cooling can be minimized, and the accuracy of the lens can be improved. Of course, even during this fixed time, the pressure P2
Is given.

In the above embodiment, the case of forming a convex lens has been described. However, the present invention is not limited to this, and optical elements having other shapes, such as a concave lens, a meniscus lens, a flat optical element, etc. It is needless to say that the present invention can also be applied to the molding of.

[0040]

As described above, according to the glass forming method of the present invention, by detecting the moving speed of the mold member and starting cooling based on the detected speed, the tact time of forming can be reduced, and the production time can be reduced. Performance can be improved.

Further, by applying a pressing pressure to the glass material at the time of cooling, it is possible to prevent the accuracy of the shape of the optically functional surface from being degraded. When the temperature of the initial glass material is high, an excessive pressing pressure is not applied to the glass material, so that the glass material is not deformed more than necessary and the wall thickness accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a view showing a structure of a mold to which a molding method of an optical composition according to an embodiment is applied.

[Explanation of symbols]

 REFERENCE SIGNS LIST 12 Molding die 14 Body die 16 Upper die member 17 Spacer 18 Lower die member 19 Spacer 20 Support substrate 22, 24 Air cylinder 26 Heater 28 Displacement sensor 30 Arithmetic unit 32 Controller 40 Glass material

Claims (3)

(57) [Claims] 1. A glass forming method in which a glass material is put between a pair of forming mold members and the glass material is heated to be formed into a glass molded article by the pair of forming mold members. A pressing step of closing a mold member and transferring a molding surface of the mold member to the glass material; a detecting step of detecting an approach speed of the pair of mold members; and an approach speed detected in the detecting step is 1 μm. / Se
c, when the pair of mold members approach each other,
A glass forming method, comprising: determining a pressed-off state, which is a substantially completed state, and immediately shifting the mold member to a cooling step. 2. In the pressing step, a first pressing force P1 is applied to the glass material by causing one of the pair of molding members to move closer to the other stationary molding member. In the cooling step, a second pressing pressure P2 is applied to the glass material by causing the other mold member to move closer to the one mold member that has finished moving. The glass forming method according to claim 1, wherein 3. In the cooling step, the second press pressure P2 is set so as not to exceed the first press pressure P1 in an initial stage of application of P2, and thereafter is gradually limited to P1. The glass forming method according to claim 2, wherein the number is increased.