JP2003063837A - Method of forming optical element and apparatus for forming the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forming apparatus and a forming method for an optical element by which the optical element does not have a substantially different temperature distribution in a cooling process for the element to be formed and the optical element of good quality can be formed. SOLUTION: The forming apparatus 1 for an optical element is provided with: a cylindrical sleeve 2C; a pair of an upper die 2a and a lower die 2b inserted into both opening parts of the sleeve; a pressure mechanism 9 for pressing the upper and the lower die; a heating furnace 6 which is mounted on the outer periphery of the sleeve and can be controlled being divided at least into two parts vertically; a pair of thermometers 19 for respectively measuring the temperatures in the vicinity of die surfaces of the upper and the lower die; and a control part 14 which individually controls the temperature lowering conditions of the upper and the lower die based on the measured data from the pair of thermometers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element molding method and apparatus for pressing an optical material that has been softened by heating to pressure-mold an optical element.

[0002]

2. Description of the Related Art As a conventional technique for molding an optical element of this type and a device therefor, Japanese Patent Laid-Open No. 5-97447 discloses a molding material disposed between an upper mold and a lower mold, which is heated by a mold. Discloses a method and apparatus for performing press molding after heating to a desired temperature by radiant heat by another heating means.

[0003]

Generally, in the case of molding an optical element (for example, a lens) having extremely different radii of curvature on both sides, a sleeve is formed by a thermal radiation heating device as in the prior art described above. If a means for uniformly applying radiant heat is used, the volume of the optical material that fills the space formed by the molding surface of the mold with a small radius of curvature becomes much more extreme than that formed by the molding surface of the mold with a large radius of curvature. When the optical element is divided into two parts, a large difference occurs in the heat capacity that can be stored.

If such an optical element is cooled in the same manner from the uniform heating state of the mold and the optical element, the movement of heat from the molding surface is substantially the same on both molding surfaces, so that the heat capacity is large (radius of curvature). The cooling of the molding surface on the side of the mold is smaller than that of the other. As a result, there is a problem that internal stress is generated due to the difference in temperature distribution between the two molding surfaces, which causes quality defects such as cracks on the molding surface.

Further, the above-mentioned prior art does not describe the method of controlling the temperature in the cooling step or the function of lowering the temperature while controlling the temperature of the mold during cooling, and it is difficult to solve the above-mentioned problems. .

The present invention has been made in view of the above circumstances, and a good quality optical element can be formed without giving a large difference in temperature distribution to the optical element in the step of cooling the optical element to be formed. An object is to provide a molding method and a molding apparatus for an optical element.

[0007]

The invention according to claim 1 is
A pair of upper molds consisting of upper and lower openings of a cylindrical sleeve,
An optical element in which a lower mold is inserted, the upper mold, the lower mold and the sleeve are heated by a heating device to heat and soften an optical material arranged between the upper mold and the lower mold, and press molding is performed to obtain an optical element. In the molding method of 1, the heating capacity of the heating device is controlled while monitoring the temperature near the surface of the upper mold and the temperature near the surface of the lower mold in the cooling step after press molding, and the upper mold temperature and the lower mold temperature are controlled. It is characterized in that the cooling state of the mold temperature is managed individually.

According to a second aspect of the invention, in the optical element molding method according to the first aspect, at least the glass transition point of the optical material to be molded is controlled for the temperature lowering state of the upper mold and the lower mold after the press molding. The feature is that the process is performed until the following.

According to a third aspect of the present invention, there is provided an optical element molding apparatus in which a cylindrical sleeve and a pair of upper and lower molds inserted into both openings of the sleeve are pressed, and an upper mold and a lower mold are pressed. Of the pressing mechanism, a heating furnace installed on the outer circumference of the sleeve and capable of being divided into at least two upper and lower parts, a pair of temperature measuring devices for respectively measuring temperatures near the mold surfaces of the upper mold and the lower mold, and a temperature measuring device. And a control unit for individually controlling the temperature lowering states of the upper mold and the lower mold based on the measurement data.

According to a fourth aspect of the present invention, in the optical element molding apparatus according to the third aspect, the controller controls the upper mold according to the material characteristics of the optical material to be molded and the shape of the optical element to be molded. And a storage unit for storing the temperature decrease pattern data of the lower mold temperature.

The operation of the optical element molding method and molding apparatus of the present invention will be described below. In the present invention, a pair of upper molds inserted from the upper and lower openings of a cylindrical sleeve,
The optical material arranged between the lower molds is heated by a heating furnace installed on the outer circumference of the sleeve, and then pressure-molded by the upper mold and the lower mold.

In the cooling step after the press molding, the heat transfer from the side having a small radius of curvature, that is, the side having a large space formed by the molding surface and having a large volume filled with the optical material to the molding die, has a large radius of curvature. To make it relatively faster than that of (the mold with a smaller radius of curvature has a lower temperature than the other mold to increase the temperature difference between the molded optical element and the mold to accelerate heat transfer) In addition, the temperature near the surface of the upper mold and the temperature near the surface of the lower mold are monitored, and the temperature near the molding surface of the mold having a large radius of curvature (for example, the lower mold) is measured by the temperature of the other mold Cool it while keeping it somewhat higher than the mold temperature.

Thus, cooling can be performed while balancing the amount of heat escaping from the molding surface having a large radius of curvature of the optical element to the lower mold side and the amount of heat escaping from the molding surface having a small radius of curvature to the upper mold side. It is possible to reduce the difference in temperature distribution inside the optical element that occurs during the process, and it is possible to mold a good quality optical element.

It is desirable that the temperature control of the upper mold and the lower mold in this cooling step be performed within the moldable range of the optical element, that is, below the glass transition point of the optical material.

In the present invention, the heating device is composed of at least two heating furnaces at the upper and lower sides, and the temperature near the molding surface of the mold is individually monitored and measured by a pair of temperature measuring devices. Based on the control unit individually controlling the heating capacity of each heating furnace, that is, the temperature lowering state of the upper mold and the lower mold, the above-described molding method can be realized.

In this case, for temperature control of the upper mold and the lower mold, temperature-decreasing pattern data determined in advance by experiments according to the material characteristics of the optical material to be molded and the shape of the optical element are stored in the storage unit, It is executed by the control unit based on the temperature decrease pattern data.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below.

(Embodiment 1) (Structure) FIG. 1 is a schematic sectional view of a molding apparatus 1 according to Embodiment 1 of the present invention, and FIG. 2 is a schematic block diagram showing a control system of the molding apparatus 1 according to Embodiment 1. It is a figure.

The molding apparatus 1 according to the first embodiment includes a molding chamber 5
A mold 2 composed of an upper mold 2a, a lower mold 2b, and a sleeve 2c for molding the optical material 22 therein, a moving table 3 for moving the mold 2, and a pressing mechanism portion 9 to press the mold 2. The main shaft 4, a heating device 6 for heating the mold 2, and a control device 14 arranged outside the mold 2 and the heating device 6 are generally configured.

The mold 2 is composed of an upper mold 2a, a lower mold 2b and a sleeve 2c, and the material thereof is cemented carbide WC or ceramics. The molding surface 7a of the upper mold 2a is the molding surface 7b of the lower mold 2b.
It has a spherical shape with an extremely small radius of curvature as compared with. Also, the molding surface 7a is formed at the axial center of the upper mold 2a and the lower mold 2b.
A pair of temperature measuring devices 19 are installed near 7b. The thermometer 19 is composed of a thermocouple, a thermistor, and a radiation thermometer.

The sleeve 2c of the die 2 has a cylindrical shape, and has an inner diameter dimension that is fitted in the outer peripheries of the upper die 2a and the lower die 2b so as to be vertically movable.

The movable table 3 is provided with an installation part 8 for installing the mold 2 on the upper part thereof, and the installed part 8 can be moved into and out of the molding chamber 5 as the movable table 3 moves up and down.

The main shaft 4 is arranged on the upper side of the molding chamber 5,
It is adapted to be connected to the pressing mechanism section 9 and to drive the main shaft 4 up and down by the pressing mechanism section 9 to apply a pressing force to the upper die 2a. The pressing mechanism unit 9 includes a drive source and a guide (not shown) such as a cylinder or a motor, and supports and drives the main shaft 4 so as to be vertically movable.

The heating device 6 is composed of four ring-shaped infrared lamps 1 arranged concentrically with the sleeve 2c.
0a, 10b, 10c, 10d and infrared lamp 10
It is composed of a pair of upper and lower infrared reflecting plates 11a and 11b arranged outside the outer periphery of a, 10b, 10c and 10d. The infrared lamps 10a, 10b, 10c and 10d are attached to the heating device 6 by metal fittings (not shown).
The infrared reflection plate 11a includes two infrared lamps 10a on the upper side,
It has a shape in which infrared rays emitted from 10b are uniformly reflected on the upper outer peripheral portion of the sleeve 2c.

Further, the infrared reflecting plate 11b has a shape that uniformly reflects the infrared rays emitted from the lower two infrared lamps 10c and 10d to the lower outer peripheral portion of the sleeve 2c.

A suction port 12 for sucking an inert gas to make the entire molding chamber 5 a non-oxidizing atmosphere and an exhaust port 13 for discharging the air inside the molding chamber 5 are provided so as to communicate with the molding chamber 5, respectively. ing. The diameter of the suction port 12 is formed larger than that of the exhaust port 13.

Next, the control device 14 will be described with reference to FIG. The control device 14 includes an upper mold 2a and a lower mold 2b.
A pair of amplifiers 15 for amplifying temperature data (signals) from the temperature measuring devices 19 installed in the infrared ray lamps 10 outside the upper mold 2a and the lower mold 2b under the control of the control unit 17 described later.
A pair of temperature adjusters 18 for adjusting light emission of a to 10d
And a pair of power regulators 16 for driving the infrared lamps 10a and 10b and the infrared lamps 10c and 10d to emit light under the control of a pair of temperature regulators 18, and an upper mold 2a and a lower mold 2b which have been experimentally obtained in advance. In addition to having a storage unit (not shown) in which the data of the cooling pattern in the cooling step is stored, the temperature information from the amplifier 15 is compared with the data of the cooling pattern, and a control command is issued to the pair of power regulators 16. And a control unit (CPU) 17 for outputting

(Operation) The operation of the molding apparatus 1 according to the first embodiment will be described by taking an example of molding an optical material 22 having a transition point of 381 ° C. and a yield point of 404 ° C. which has been spherically polished in advance to obtain an optical element. Explain.

The upper die 2a, the optical material 22, and the lower die 2b are inserted into the sleeve 2c, placed on the installation portion 8, and the moving table 3 is moved.
And the molding chamber 5 is closed (at this time, no pressing force is applied between the upper mold 2a and the lower mold 2b). The inside of the molding chamber 5 is purged with the inert gas by introducing the inert gas into the molding chamber 5 through the suction port 12 and simultaneously exhausting the internal air from the exhaust port 13.

After the completion of purging with the inert gas, the pressing mechanism 9 is further operated to apply a pressing force between the upper mold 2a and the lower mold 2b, and the infrared lamps 10a, 10b, 10
C and 10d are made to emit light, and infrared rays are uniformly irradiated to the outer circumference of the sleeve 2c. The heating device 6 is controlled so that the die 2 rises to the deformation point temperature of 404 ° C., and after holding for 20 seconds or more, the infrared ray emission is stopped and the process proceeds to the cooling step. At the time of completion of molding, the mold 2 and the optical material 22 have almost the same temperature.

In the cooling step, the molding surface 7 having a small radius of curvature is used.
Since the heat storage on the a side is larger than that on the molding surface 7b side having a large radius of curvature, the larger radius of curvature tends to cool faster.
The temperature change in the cooling process is taken into the control unit 17 via the amplifier 15 in real time by the temperature measuring device 19.

The control unit 17 includes an upper mold 2 which can minimize the heat distribution of the molded product obtained by the experiment and ensure good quality.
The data of the temperature lowering pattern of a and the lower mold 2b is stored in advance, and the difference data is calculated by comparing with the data from the temperature measuring device 19.

A control signal is sent from the control unit 17 to the pair of temperature adjusters 18 so as to always minimize the difference data.
The pair of temperature adjusters 18 are the infrared lamps 10a, 10b, the infrared lamps 10c, 1 by the pair of power adjusters 16.
Adjusting the timing of light emission drive for 0d, the upper mold 2
a, the temperature of the lower mold 2b is controlled.

The flow of temperature reduction control in the cooling process of the mold 2 will be described in detail below with reference to the flow chart shown in FIG. When entering the cooling process of the mold 2, the infrared lamp 10
All of a to 10d are driven to be turned off (step S1).

At the same time when the infrared lamps 10a to 10d are turned off, the temperature of the mold 2 begins to drop due to natural heat dissipation and heat conduction to peripheral elements. At this time, the control unit 17 controls the upper mold 2a and the lower mold 2 from the temperature measuring devices 19 installed in the upper mold 2a and the lower mold 2b.
Each temperature data near the molding surface of b is recognized in real time (about every 1 second) (step S2).

The respective temperature data of the upper mold 2a and the lower mold 2b that have been recognized are respectively compared with the data of the temperature drop pattern which is input and stored in the storage unit of the control unit 17 in advance (step S3).

When the temperature of the upper mold 2a or the lower mold 2b becomes lower than the temperature of the temperature lowering pattern (step S4), the infrared ray lamp is transferred from the controller 17 to the corresponding temperature controller 18 of the pair of temperature controllers 18. 10a, 10b or 10c,
A lighting signal of 10d is sent, which causes a fixed time (about 1
Infrared lamp 10a, 10b or 10c, 10d
Lights up and the temperature lowering state of the upper mold 2a or the lower mold 2b is adjusted (step S5).

After the processing of steps S1 to S5 is completed, the above-described processing of steps S2 to S5 is repeated until the temperature of the mold 2 and the optical material 22 becomes lower than the glass transition point temperature. Mold 2 and optical material 2
The temperature control process of No. 2 is finished (step S6).

(Effect) According to the first embodiment, when an optical element having a shape having a large difference in curvature radius and having a temperature distribution easily formed on the upper and lower surfaces of the optical material 22 at the time of cooling is used, a metal is used in the cooling step. The temperature lowering process of the mold 2 can be individually controlled by the upper mold 2a and the lower mold 2b, which makes it possible to obtain an optical element that is a good quality molded product.

(Second Embodiment) (Structure) Next, a second embodiment of the present invention will be described with reference to FIGS. In the second embodiment,
Except for the control device 14A, the other configuration is the same as that of the first embodiment, and thus the duplicated description will be omitted. The control device 14A according to the second embodiment shown in FIG. 4 includes a sequencer 20 that is a control unit that performs overall control, and an infrared lamp 10.
a, 10b and a pair of power regulators 16 for respectively driving the infrared lamps 10c, 10d to emit light, and a pair of program temperature regulators 21 for controlling the pair of power regulators 16 by setting the temperature by a program. To be done.

(Operation) In the second embodiment, the upper mold 2
The pattern of temperature decrease of the mold temperature of a and the lower mold 2b is programmed in the pair of program temperature controllers 21 in a stepwise manner such that the temperature is several degrees Celsius after a few minutes. Therefore, the cooling pattern of the mold temperature in the cooling step has a slightly wavy shape, but this can be dealt with by shortening the set interval.

FIG. 5 shows a temperature control pattern of the upper mold 2a and the lower mold 2b in the cooling process. The horizontal axis represents time and the vertical axis represents temperature. Infrared lamp 10a, 10b or infrared lamp 10
c and 10d are the temperatures (set temperature 1, set temperature 2, ...) At which the upper mold 2a or the lower mold 2b is set for each set time interval (set time 1, set time 2, ...). )become,
After that, lighting and extinguishing control are performed so as to perform natural cooling.

Such control is repeatedly continued until the upper die 2a, the lower die 2b and the optical material 22 of the die 2 reach the glass transition point or lower.

(Effect) According to the second embodiment, the same effect as that of the first embodiment is obtained by using the control device 14A having a simpler configuration than that of the first embodiment and performing a simple control process. Can be played.

[0045]

According to the present invention, cooling is performed while balancing the amount of heat escaping from the molding surface having a large radius of curvature of the optical element to the mold side and the amount of heat escaping from the molding surface having a small radius of curvature to the mold side. It is possible to reduce the difference in temperature distribution inside the optical element that occurs during the cooling step, and it is possible to provide an optical element molding method capable of molding a good quality optical element.

Further, according to the present invention, it is possible to provide an optical element molding apparatus capable of molding a good quality optical element by reducing the difference in temperature distribution inside the optical element that occurs during the cooling step.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a cross section of a part of a molding device of an optical element according to a first embodiment of the present invention.

FIG. 2 is a schematic block diagram of a control system of the optical element molding apparatus according to the first embodiment.

FIG. 3 is a flowchart showing a flow of temperature lowering processing of an upper mold and a lower mold by the optical element molding method according to the first embodiment.

FIG. 4 is a schematic block diagram of a control system of an optical element molding apparatus according to a second embodiment of the present invention.

FIG. 5 is an explanatory view showing a pattern of decreasing the mold temperature in the method of molding an optical element according to the second embodiment.

[Explanation of symbols]

1 molding equipment 2 mold 2a Upper mold 2b Lower mold 2c sleeve 3 mobile platforms 4 spindles 5 molding room 6 heating device 7a Molding surface 7b Molding surface 8 installation departments 9 Pressing mechanism 10a-10d infrared lamp 11a Infrared reflector 11b Infrared reflector 12 suction port 13 Exhaust port 14 Control device 14A control device 15 amplifier 16 Power regulator 17 Control unit 18 Temperature controller 19 Thermometer 20 sequencer 21 Program temperature controller 22 Optical material

Claims (4)

[Claims] 1. A pair of an upper mold and a lower mold are inserted from upper and lower openings of a cylindrical sleeve, and the upper mold, the lower mold and the sleeve are heated by a heating device, and a space between the upper mold and the lower mold. In the method of forming an optical element, in which the optical material placed in the mold is heated and softened to obtain an optical element by press molding, the temperature near the upper mold surface and the temperature near the lower mold surface in the cooling step after the press molding. A method for molding an optical element, characterized in that the heating capacity of the heating device is controlled while monitoring the above, and the cooling state of the upper mold temperature and the lower mold temperature are individually managed. 2. The optical element according to claim 1, wherein the temperature lowering state of the upper mold and the lower mold after the press molding is performed at least until the glass transition point of the optical material to be molded is below the glass transition point. Molding method. 3. A cylindrical sleeve, a pair of upper and lower dies inserted into both openings of the sleeve, a pressing mechanism for pressing the upper and lower dies, and a sleeve provided on the outer circumference of the sleeve. A heating furnace that can be divided into at least two upper and lower parts, a pair of thermometers that measure the temperatures near the upper and lower mold surfaces, respectively, and the temperature drop of the upper and lower molds based on the measured data of the thermometers. An optical element molding apparatus comprising: a control unit that individually controls a state. 4. The control unit includes a storage unit that stores temperature decrease pattern data of mold temperatures of the upper mold and the lower mold according to material characteristics of an optical material to be molded and shapes of optical elements to be molded. The apparatus for molding an optical element according to claim 3, wherein: