JP2002348126A - Method for moulding optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of surely detecting the exfoliation of a glass material from a mould member by a simple apparatus, preventing an optically functioning surface of an optical element from being scraped and damaged, preventing the generation of a defective mould releasing and shortening the tact time. SOLUTION: The method comprises cooling a mould member and a glass material while applying such a minute rotation torque to the axis of a press, so as not to forcibly exfoliate the mould member from the glass material, during the cooling process, detecting the exfoliation of the mould member from the glass material by opening the mould at the moment that the mould member is exfoliated from the glass material and the rotation torque is released, and thus moulding an optical element in the shortest possible time that does not generate defective mould releasing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding an optical element having a complicated shape, such as an aspherical lens, which can be press-molded with high precision while preventing cracks and mold release defects. It is about the method.

[0002]

2. Description of the Related Art In a recently proposed method of manufacturing an optical element by inserting an optical element material into a molding die having a predetermined surface accuracy and press-molding the same, a method of opening a mold member to take out the optical element is required. In addition, there is a problem in that the mold member and the glass material adhere to each other, and the optical element is cracked.

On the other hand, in Japanese Patent Application Laid-Open No. 4-317426, the ultrasonic flaw detection method is used to detect the release of the close contact between the mold member and the glass material from the change in the ultrasonic waveform. A method of opening the mold to prevent a mold release failure has been proposed.

[0004]

However, in the method of the above-mentioned conventional example (Japanese Patent Laid-Open No. 4-317426), the ultrasonic flaw detector must be attached to the hot press shaft, so that complete cooling of the shaft is necessary. Therefore, the configuration becomes complicated as a device. Also, depending on the installation condition of the ultrasonic flaw detector and the shape of the target optical element, the ultrasonic waveform image may be buried in noise, and it may be difficult to detect the separation between the mold member and the glass material.

Accordingly, an object of the first invention according to the present application is to
An object of the present invention is to more reliably detect separation between a mold member and a glass material with a device having a simpler configuration.

A second object of the present invention is to prevent the optical function surface of the optical element from being scratched and damaged due to rotation of the press shaft.

Another object of the third invention according to the present application is to reduce tact time.

[0008]

In order to achieve the above object, a first invention according to the present application is to provide a cooling device, comprising:
It is characterized in that cooling is performed while applying rotational torque to the press shaft.

In the above configuration, the means of the first invention is:
The release of the rotational torque applied to the shaft, which occurs when the mold member and the glass material are separated, acts to detect the separation of the two.

[0010] In order to achieve the above object, a second invention according to the present application provides a rotating torque of 50 kgf.
It is characterized by the following.

In the above configuration, the means of the second invention comprises:
In a high-temperature range where the strength of the glass material is low, the rotational torque applied to the shaft forcibly separates the mold member and the glass material, and prevents the optical function surface of the optical element from being scratched and damaged by the mold member I do.

In order to achieve the above object, a third invention according to the present application provides a mold opening operation at the moment when the rotating torque applied by releasing the mold member and the glass material during the cooling step is released. Is performed.

[0013] In the above configuration, the means of the third invention comprises:
By opening the mold immediately after the mold member and the glass material are peeled off, it acts so as to perform the molding in the shortest time in which no mold release failure occurs.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In this embodiment, a case in which a heavy meniscus optical element shown in FIG. 1 is formed using heavy crown glass (SK12) as a glass material will be described.

FIG. 2 shows the configuration of a molding barrel 1 for molding a concave meniscus lens, and shows a state in which the molding of the glass lens is substantially completed.

In FIG. 2, a through-hole is formed in a state in which the shaping die 1 is vertically penetrated, and a cylindrical upper mold member 2 is fitted in the upper through-hole. And is slidably inserted in the vertical direction. A disc-shaped flange portion is formed at the upper end of the upper mold member 2, and this flange portion comes into contact with the upper surface of the molding die 1 from above via a spacer for adjusting the thickness of the lens. Defines the press stroke of the upper die member 2. On the lower surface of the upper mold member 2, a molding surface for pressing the glass material 4 to transfer a desired shape to the surface to form an optical function surface is formed.

On the other hand, a lower mold member 3 formed in a columnar shape like the upper mold member 2 is slidably inserted in the up-down direction along the lower through-hole.

On the upper end surface of the lower mold member 3, a molding surface for transferring a desired shape to the lower surface of the glass material 4 to form an optical function surface is formed.

The thickness of the molded concave meniscus lens (glass material 4) is defined by the flange portion of the upper die member 2 being in contact with the upper surface of the molding die 1, as described above. The thickness of the concave meniscus lens (glass material 4) does not change every time the operation is performed.

On the other hand, an opening hole is formed in the side surface of the molding die 1, through which the glass material 4 is supplied into the molding die 1 and the completion of the molding. Molded meniscus lens (glass material 4)
Taken out from inside.

In the molding die 1, the molding die 1, the upper die member 2 and the lower die member 3 are heated while being positioned at the four corners, and the molding die 1, A heater 5 for heating the glass material 4 via the upper mold member 2 and the lower mold member 3 is provided.

Next, an actuator for press and another actuator for rotation direction are mounted on the upper shaft, so that the glass material 4 can be compressed and the shaft itself can be rotated. I have. An actuator for pressing is also mounted on the lower shaft.

A concave meniscus lens is molded by the molding process according to the present invention using the above-described mold configuration. FIG. 3 shows a process diagram of the lower mold temperature and the weight.

First, the upper mold member 2 is slid upward with respect to the shaping die 1. In this state, the glass material 4 heated to a predetermined temperature is supplied onto the molding surface of the lower mold member 3 by an automatic hand or the like. Further, the molding die 1, upper mold member 2, and lower mold member 3 are heated to a temperature corresponding to predetermined molding conditions. In this embodiment, the temperature of the lower mold member 3 has a temperature corresponding to ¹⁰ 9.5 dPa · s in viscosity of the glass material 4 (620 ℃). In the present embodiment, a rotating load is applied to the upper die member 2 via a press shaft after the end of the cooling press applied during a cooling step described later.
Thus, the separation between the mold member and the glass material is detected, and the separation between the two occurs first between the upper mold member 2 and the glass material 4 and between the lower mold member 3 and the glass material 4. It is supposed to happen. Whichever comes first, if either one is peeled off, the optical element (glass material 4) will not break and will not be a mold release defect. Mold member 2
If the optical element (glass material 4) is in close contact with the substrate, it cannot be taken out, and cooling must be performed until the close contact is naturally separated.

That is, in terms of molding tact, the upper mold member 2
It is desirable to be able to detect the separation of the glass material 4 from the glass material 4.
Therefore, in the present embodiment, the temperature of the upper mold member 2 is always controlled to be lower by 10 ° C. than the temperature of the lower mold member 3. Thereby,
The separation always occurs first between the upper mold member 2 and the glass material 4.

Next, the glass material 4 is pressed by applying a load of 4000 N in the present embodiment, and the glass material 4 is gradually crushed in the horizontal direction.
The state is as shown in FIG. In this state,
Optical function surfaces on which the shapes of the molding surface of the upper mold member 2 and the molding surface of the lower mold member 3 are transferred are formed above and below the glass material 4.

Thereafter, the molded concave lens (glass material 4) is cooled. In this cooling process, in this embodiment, the viscosity of the glass material 4 is equivalent to 10 ^10.5 dPa · s in order to prevent the glass material 4 from being unevenly peeled between the upper and lower mold members 2 and 3. Temperature (600
C.), the glass material 4 was cooled to a temperature (550 ° C.) corresponding to a viscosity of 10 ¹² dPa · s or more with a load of 3200 N applied.

Here, first, the load of 3200N is unloaded from the lower mold member 3, and then the load of 4000N is unloaded from the upper mold member 2.

At this point, no compressive force is applied to the glass material 4 from the mold member, and the mold members 2 and 3 and the glass material 4 are connected only by the adhesion between them.

Next, while applying a rotational load to the upper mold member 2 via a press shaft, cooling is further advanced. At this time, if the applied rotational load is too large, the mold member and the glass material 4 are peeled off by a forced shearing force. Then, the mold member and the optically functional surface of the glass material 4 are rubbed, which is very undesirable as a lens. Therefore, in the present embodiment, the rotation load is set to a very small load of 50 kgf. If it is more than this, forced peeling occurs as described above, which is not desirable. If the load is less than this, there is no problem, but when the mold member and the glass material 4 are separated,
The rotating load is released momentarily and drops sharply. It is necessary to select a load value and a sensor capable of sensing the change.

In this embodiment, a load cell having a general performance with a resolution of 1 kgf and a sampling period of 1 sec is used.

When the cooling was advanced with the rotating load applied, when the temperature of the lower mold member 3 was about 530 ° C., a sharp decrease in the rotating load was detected. Then, the rotation load was unloaded as it was, and further cooled to 510 ° C., the mold was opened, and the optical element (glass material 4) was taken out.

The optical element (glass element 4) is taken out by an automatic hand or the like. In the present embodiment, the temperature of the lower mold member 3 is a temperature (500 ° C.) corresponding to 10 ¹⁴ dPa · s in viscosity of the glass material 4. Took out the concave meniscus lens.

As described above, good molding was made possible without the occurrence of mold release defects such as cracking of the glass material.

Further, as a result of continuously forming the concave meniscus lens by the method of the present invention, it was confirmed that no mold release failure occurred at all in 500 shots.

(Other Embodiments) As a second embodiment, a glass material was made of flint glass (F8), and the optical element to be formed was formed into a convex meniscus shape as shown in FIG.

Since the shape of the lens to be molded is different from that of the first embodiment, the molding apparatus used is different in the molding surface shape of the optical function surfaces of the upper mold member 2 'and the lower mold member 3' as shown in FIG. However, other parts are the same.

Molding was performed using the above-described mold structure. First
Compared with the embodiment, the glass material 4 'is made of flint glass (F
Since it is 8), it can be molded sufficiently at 520 ° C. and 3000 N load.

The optical element of the present embodiment cannot be cooled in a state where a temperature difference is provided between the upper and lower mold members 2 'and 3' during the cooling step due to the accuracy of the optical function surface. Therefore, the first
By the method of the embodiment, the upper mold member 2 'and the glass material 4' are surely formed.
Cannot be peeled off first. Therefore, in the present embodiment, as shown in FIG. 6, the projection 6 is provided on the optical function surface transfer portion of the lower mold member 3 '. However, the protrusion 6 is located outside the effective beam diameter of the optical element to be molded. At the time of pressing, the glass material 4 ′ is deformed, and is formed in a shape in which the projections 6 bite. As a result, when a subsequent rotational load is applied, no slip occurs between the lower mold member 3 'and the glass material 4' even if they are separated. Therefore, a sharp decrease due to release of the rotational load is limited only when peeling occurs between the upper mold member 2 ′ and the glass material 4 ′. For the above reason, in the present embodiment, the upper and lower mold members 2 'and 3' are controlled to the same temperature to perform cooling.

Next, when the temperature reaches 500 ° C., 150
Cooling was performed to 465 ° C. with a load of 0 N applied. At that time, the load 1500N of the lower mold member 3 'was unloaded, then the load of the upper mold member 2' was unloaded, and then a rotational load of 50 kgf was applied to the upper mold member 2 'to further cool.

In this embodiment, when the temperature of the upper and lower mold members 2 'and 3' reached about 430 ° C., the rotational load suddenly decreased, and the upper mold member 2 'and the glass material 4' were separated.
Immediately thereafter, the mold was opened and the optical element (glass element 4 ′) was taken out.

As described above, good molding was possible without causing mold release defects such as cracking of the glass material.

Further, as a result of continuously forming a convex meniscus lens by the method of the present invention, it was confirmed that no mold release failure occurred at all in 500 shots.

[0045]

As described above, according to the first aspect of the present invention, the separation between the mold member and the glass material can be more reliably detected by a device having a simpler configuration. Become.

According to the second aspect of the present invention, it is possible to prevent the press shaft from rotating and the optical functional surface of the optical element from being rubbed and damaged.

Further, according to the third aspect of the present invention, it is possible to prevent a mold release defect and shorten the molding tact.

[Brief description of the drawings]

FIG. 1 is a schematic view of an optical element shape formed in a first embodiment.

FIG. 2 is a configuration diagram of a molding body die of the first embodiment.

FIG. 3 is a process diagram of temperature and load in the first embodiment.

FIG. 4 is a schematic view of an optical element shape formed in a second embodiment.

FIG. 5 is a configuration diagram of a molding drum of a second embodiment.

FIG. 6 is a schematic diagram of a lower mold member of a second embodiment.

FIG. 7 is a process diagram of temperature and load in the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molding die 2 Upper mold member 3 Lower mold member 4 Glass material 5 Heating heater 6 Projection

Claims (3)

[Claims] In a press forming method for obtaining an optical element by pressing a glass material in a softened state using two or more forming mold members, cooling is performed while applying a rotational torque to a press shaft during a cooling step. Press molding method for an optical element. 2. The press-forming method for an optical element according to claim 1, wherein the applied rotational torque is 50 kgf or less. 3. The method for press-molding an optical element, wherein a mold opening operation is performed at a moment when the rotating torque applied by releasing the mold member and the glass material during a cooling step is released. A method for press-molding an optical element according to claim 1.