JP4141983B2 - Mold press molding method and optical element manufacturing method - Google Patents

Description

The present invention relates to a mold press molding method and an optical element for heating and softening a molding material (preliminarily preformed preform or the like) in a manufacturing process of an optical element or the like, and press molding with a molding die to mold the optical element or the like. It relates to the manufacturing method .

A molding material in a heat-softened state, for example, a glass material, is press-molded in a mold that is precisely processed into a predetermined shape and heated to a predetermined temperature, and the molding surface is transferred to the glass material. An optical element with high surface accuracy and shape accuracy can be obtained without processing. In this case, after the press molding, when the optical element is released from the mold, it is necessary to cool the mold to an appropriate temperature and release it. For this reason, in order to mass-produce optical elements continuously by press molding, it is necessary for the mold to perform a heat cycle in a predetermined temperature range at least between the press temperature and the mold release temperature.
In such a case, if induction heating is used, the coil itself, which is a heating means, does not generate heat, and the heated object (heating element) is directly heated, so that rapid heating is possible and rapid cooling is also possible. Therefore, it is advantageous in terms of shortening the molding cycle time.
Therefore, it is known that in a precision press of a glass optical element, high-frequency induction heating that provides a rapid and sufficient heating capacity is used as a means for heating a mold.

  On the other hand, when the upper mold and the lower mold have the same temperature or a predetermined temperature difference between the upper mold and the lower mold, it is precisely controlled according to a predetermined temperature rise / fall schedule that the surface accuracy of the optical element to be molded It is very important in improving the shape accuracy. In controlling the upper mold and the lower mold to a predetermined temperature, a molding apparatus that heats the separated molds by high frequency induction heating has been proposed.

  As such a molding apparatus, for example, there is an apparatus for controlling the temperature of the upper and lower molds by moving a heating coil provided around the upper and lower molds in parallel with the moving direction of the mold (see, for example, Patent Document 1). ).

  Further, there is also disclosed an apparatus for heating a mold at a separated position when a movable mold of the upper and lower molds is separated from a pressurizing position for taking out a molded product or supplying a material ( For example, see Patent Document 2).

JP-A-5-310434 JP-A-11-171564

  However, the molding apparatus described in Patent Document 1 requires a large-scale apparatus for moving the heating coil into the molding chamber, and in order to supply the molding material, the lower mold is greatly lowered to the outside of the coil. There is a problem that the lower mold temperature is lowered at this time, and it takes time to raise the mold.

  Moreover, since the apparatus described in Patent Document 2 has an interval that allows the material to be supplied between the molding surfaces of the upper and lower molds that are separated from each other, heat is easily taken away by the surrounding atmosphere. In addition, if a member (sleeve, etc.) for precise positioning of both protrudes from the molding surface of the upper and lower molds, the heating efficiency for these members will deteriorate, the thermal deformation will become uneven, and positioning will occur. There was a case where a poor fitting of the members occurred.

  In particular, in order to increase productivity, in a device in which the shape of the mother die is long and a plurality of forming dies are arranged in a straight line and a plurality of simultaneous presses are performed, if the heating distribution is poor, the mother die is heated. It becomes non-uniform and heat deformation (warping) is likely to occur in the matrix. And when thermal deformation occurs in the master mold, the individual molds lose the upper and lower coaxiality, and tilting occurs in the molded optical element (for example, a lens) to deteriorate the eccentricity accuracy and the thickness is not uniform. become.

The inventor has made various studies in order to solve the above problems. As a result, heating for the next press is started with respect to the mold located at a separated position in order to take out the molded product (optical element), and it is in the proximity or contact position for preheating the die after taking out the molded product. It has been found that when the mold is continuously heated, the heating efficiency of the positioning member and the like is improved, the deformation of the mother die is prevented, and the fitting failure of the positioning member can be prevented.
However, a new problem has arisen here. That is, when heating is performed by placing a heating coil in both the position where the molded product is taken out and the position where the mold is close (including the case of contact, the same applies hereinafter), the mold is supported when the mold is in the close position. It has been found that the shaft (main shaft) for this purpose is heated by a heating coil at the molded product take-out position, causing thermal deformation, resulting in a decrease in accuracy of the molded product.
Further, when the upper and lower molds are heated by a single coil, the temperature near the center of the coil, that is, the opposing surface of the upper and lower mother molds, is most easily heated, and it is also found that the warp as shown in FIG. It was.

Therefore, the present inventors have further studied earnestly. As a result, the heating coil is arranged separately for the upper mold heating and the lower mold heating, and for the movable mold, the heating coil is disposed at both the proximity position and the molded product take-out position, and further, at the movable mold position. It has been found that the above problem can be solved by switching the supply (energization) of current to both heating coils accordingly. The present invention is based on the above knowledge, a mold press molding method and an optical device capable of stably producing an element having high eccentricity accuracy and thickness accuracy in a short production cycle time by preventing thermal deformation of the shaft (main shaft). An object is to provide a method for manufacturing an element .
In addition, the present invention provides a high-precision mold press molding method capable of obtaining necessary optical performance without requiring post-processing such as polishing after press molding .
Furthermore, the present invention provides a mold press molding method with high production efficiency for simultaneously molding a plurality of optical elements, and a method for producing an optical element by this mold press molding method.

In order to achieve the above object, a mold press molding method of the present invention includes a stationary mold and a movable mold, which are arranged to face each other in a molding chamber, and the movable mold, wherein the movable mold approaches or contacts the stationary mold. A movable main shaft that is moved between one position and a second position at which the movable mold is separated from the fixed mold by a predetermined distance, and is stopped at the first position and the second position, respectively, and the fixed mold and the movable mold. A heating coil for induction heating is provided , and a current is supplied to each of the heating means for the fixed mold and the heating means for the movable mold installed in the molding chamber, and the heating coil provided for the heating means for the fixed mold and the heating means for the movable mold. and a provided independently to supply power, the mobile heating means, a first heating coil for heating the movable die when in the first position, in said second position When Molding using a mold press molding apparatus having a second heating coil for heating the movable mold, and a switching means for selectively energizing the current from the power source to the first heating coil and the second heating coil. materials Upon press molding, wherein Ri mobile said first position near said the Rutoki said periphery of the movable head second heating coil is not ready to be wound, energized thereby to the second heating coil Instead, the heating coil of the fixed mold heating means and the first heating coil are energized at different frequencies with a ratio of the transmission frequencies of 1: 1.5 to 1: 7, or for the fixed mold. The heating coil of the heating means and the first heating coil are energized in a time-sharing manner. When the movable mold is in the second position, the heating coil of the fixed mold heating means and the second heating coil are energized simultaneously. I will do it , There a method to switch the energization of the second heating coil and the first heating coil.

With such a method, the energization of the first heating coil and the second heating coil is switched depending on the position of the moving mold, so that the fixed mold and the moving mold can be located close to each other and separated from each other. However, the fixed mold and the movable mold can be continuously heated, and a molding element (optical element) with high surface accuracy and shape accuracy can be molded in a short production cycle time. In other words, regardless of the timing of supplying the molding material and taking out the molded product, the most efficient heating schedule is selected by switching to the first or second heating coil and energizing it in accordance with the movement of the movable mold. Is possible.

The mobile type Ri first position near the periphery of the movable head to the second heating coil is not ready to wound Rutoki, since the second heating coil so that not energized, moves the mobile The shaft ( movable main shaft) for heating is not heated, and the surface accuracy and shape accuracy of the molding element (optical element) are not lowered.
At this time, it is preferable to start energization to the second coil after a predetermined interval after the current to the first heating coil is cut off. In this way, heating of the second heating coil can be stopped while the movable mold is moving.

In addition to this, for the heating coil and the first heating coil of the stationary heating means located close to each other, the ratio of the respective transmission frequencies is set to 1: 1.5 to 1: 7 at different frequencies. By energizing or energizing in a time-sharing manner, the fixed mold and the movable mold are each set to a predetermined temperature while suppressing the interference of oscillation between the fixed mold heating means and the movable mold heating means. Can be heated. In addition, since the fixed mold and the movable mold can be heated at close positions, it contributes to shortening of the molding cycle time.
Further, when energizing the heating coils that are not close to each other, there is no problem of interference. Therefore, when the movable mold is in the second position, the heating coil and the second heating coil of the heating means for the stationary mold are used. It is made to energize at the same time, and thereby high-frequency induction heating can be performed at the same time to increase the heating efficiency.
If it does as mentioned above, a movable type will be in the heated state, and heating efficiency will improve regardless of a position, and will not destroy the temperature balance of a fixed type and a movable type. Even if the mold moves , the mold is always heated, so that the mold is not cooled and efficient production can be performed in a short cycle time.

Further, in the mold press molding apparatus used in the mold press molding method of the present invention, a power source provided independently to supply current to each of the heating coils provided in the stationary mold heating means and the movable mold heating means. It is set as the structure which has.
With this configuration, it becomes possible to control the temperature of the upper mold and the lower mold independently of each other, and it is possible to perform control corresponding to the heat capacity of the movable mold and the fixed mold and the set temperatures of the upper mold and the lower mold. The mold can be brought to the desired temperature.

Here, it is preferable that the distance between the upper die heating coil and the lower die heating coil in the first position is 0.7 to 2 times the pitch of the heating coil. The pitches of the upper die heating coil and the lower die heating coil are preferably equal and substantially uniform, but if not uniform, it is preferably 0.7 to 2 times the average pitch of both heating coils.
If the distance between the upper and lower heating coils is less than 0.7 times the coil pitch, the opposing surface temperature of the upper and lower molds is excessively raised between the upper and lower heating coils, and the upper and lower molds are likely to warp. On the other hand, when the upper and lower mother dies are heated in the upper and lower heating coils, the positioning member is less likely to be heated when the upper and lower mother dies are heated in the upper and lower heating coils, particularly when a positioning member is provided. Easy to break. This prolongs the heating time and lengthens the cycle time, or causes the molding material to grow poorly.

  The optical element manufacturing method of the present invention includes a mold heating step of heating the upper mold and the lower mold in a state of being close to each other, and an optical element in which the upper mold and the lower mold are opened and heated and softened in advance between them. A material supply step for supplying the material, a molding step for press-molding the optical element by pressurizing the upper mold and the lower mold, and an extraction process for opening the upper mold and the lower mold and taking out the molded optical element therebetween In the manufacturing method of the optical element containing these, it is as a method of manufacturing an optical element using the said molding method.

Specifically, the movable mold in the first position and the fixed mold are heated to a predetermined temperature, and the movable mold and the fixed mold are also moved when the movable mold moves to the second position. This is a method of heating to a predetermined temperature and supplying the material between these molds. In the mold heating step, the second heating coil is not energized, and the heating coil of the stationary mold heating means and the first heating coil are energized at different frequencies, respectively, or the stationary mold The heating coil of the heating means and the first heating coil are energized in a time-sharing manner, and in the material supply step, the heating coil of the stationary mold heating means and the second heating coil are energized simultaneously. it can.

  In this way, it is possible to suitably perform temperature control of the upper mold and the lower mold in at least the mold heating process, the material supply process, and the take-out process, and the optical with high surface accuracy and shape accuracy is achieved with a short production cycle time. An element can be manufactured.

  According to the present invention, by switching and heating the movable heating coil, the movable heating can be performed in the element material supplying step or the molded product taking out step. The arrival time can be shortened and the molding cycle time can be shortened.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the following, the present invention will be described with reference to an embodiment in which the present invention is applied to a glass optical element manufacturing apparatus. However, the present invention is not limited to this embodiment. It can also be applied to the manufacture of parts other than resin optical elements.

[Glass optical element manufacturing equipment]
FIG. 1 is a schematic cross-sectional view when the mold press molding apparatus according to the present invention is applied to a glass optical element manufacturing apparatus.
The manufacturing apparatus shown in FIG. 1 presses a spherical glass preform to manufacture a small collimator lens. In general, a plurality of (four in the illustrated example) spherical glass preforms are simultaneously fed into the manufacturing apparatus housing, pressed by a mold, cooled, and softened by heating. It is carried out to. By repeating this, a large number of collimator lenses are continuously manufactured.

As shown in FIG. 1, the glass optical element manufacturing apparatus 10 includes a heating chamber 20 and a molding chamber 40. The heating chamber 20 and the molding chamber 40 are communicated with each other through a passage 60 provided with an opening / closing valve 61, and the heating chamber 20, the molding chamber 40 and the passage 60 form a single sealed space that is blocked from the outside. ing. The outer wall of the sealed space is formed of stainless steel or other members, and the hermeticity is maintained by a sealing material. The sealed space formed by the heating chamber 20, the molding chamber 40, and the passage 60 is set to an inert gas atmosphere when the glass optical element is molded. That is, the air in the space is exhausted by a gas exchange device (not shown) and filled with an inert gas instead. As the inert gas, it is preferable to use nitrogen gas or a mixed gas of nitrogen and hydrogen (for example, N ₂ +0.02 vol% H ₂ ).

The heating chamber 20 is an area for preheating prior to pressing the glass preform to be supplied. In this area, a preform supply device 22, a preform transport device 23, and a preform heating device 24 are installed. The In addition, a supply preparation chamber 21 for supplying the glass preform from the outside into the heating chamber 20 is installed.
In the supply preparation chamber 21, four trays (not shown) are arranged, and four glass preforms are placed thereon using a robot arm (not shown). The glass preform on the tray is adsorbed by the suction pad of the preform supply device 22 installed in the supply preparation chamber 21 and is carried into the heating chamber 20. In order to prohibit the inflow of air into the heating chamber 20, the supply preparatory chamber 21 is sealed and replaced with an inert gas atmosphere after the glass preform is placed on the receiving tray.

The preform conveying device 23 receives the glass preform carried in from the supply preparation chamber 21, conveys it to the heating region by the preform heating device 24, and further conveys the heat-softened glass preform to the molding chamber 40. The preform conveying device 23 includes four dishes 26 at the tip of the arm 25, and holds the glass preform thereon.
In the embodiment, the arm 25 including the dish 26 is horizontally supported by the drive unit 23a fixed in the heating chamber 20, and the arm 25 is rotated in the horizontal direction with a rotation angle of approximately 90 degrees. In addition, the arm 25 is configured to be capable of withdrawing and retracting in the radial direction with the drive unit 23 a as the center, and thereby, the held glass preform is conveyed to the molding chamber 40.

The preform transport device 23 includes an arm opening / closing mechanism (not shown) in the drive unit 23a, thereby opening the tip of the arm 25 and dropping the glass preform on the tray 26 onto the mold.
When the glass preform is preheated and transported in a softened state, if the glass surface is defective due to contact with the transport jig, the shape accuracy of the optical element after molding is impaired. Is preferably provided with a levitation jig for conveying the glass preform in a gas levitation state. For example, as shown in FIG. 6, it is possible to use a split type floating dish that is supported by a separable arm.
In order to automatically take out the molded optical element from the spaced apart dies, it is preferable to include a suction conveyance device including a suction pad.

The preform heating device 24 is for heating the supplied glass preform to a temperature corresponding to a predetermined viscosity. In order to stably raise the temperature of the glass preform to a certain temperature, it is preferable to use a heating device (for example, an Fe—Cr heater) by resistance heating using a resistance element. The preform heating device 24 has a substantially U-shape when viewed from the side, and includes heater members on the upper and lower surfaces thereof. As shown in FIG. 1, the preform heating device 24 is installed on the movement locus of the glass preform held on the arm 25.
The arm 25 is placed in the preform heating device 24 except when the glass preform is received from the preform supply device 22 and when it is transported to the molding chamber 40. The heater temperature of the preform heating device 24 can be about 1100 ° C., and the atmosphere in the furnace, that is, the atmosphere between the upper and lower heaters can be about 700 to 800 ° C. In the present embodiment, the arm 25 is prevented from warping in the vertical direction by providing a temperature difference between the upper and lower heaters.

  On the other hand, the molding chamber 40 is a region for pressing the glass preform preliminarily heated in the heating chamber 20 to mold a glass optical element of a desired shape. An element carry-out device 42 is installed. Further, a take-out preparation chamber 43 is provided for carrying out the press-molded glass optical element to the outside.

  The pressing device 41 simultaneously receives four glass preforms conveyed from the heating chamber 20 by the preform conveying device 23 and presses them to obtain a glass optical element having a desired shape. The press device 41 includes an upper die and a lower die, and simultaneously presses the four glass preforms supplied therebetween with their molding surfaces. The four glass preforms on the arm 25 of the preform conveying device 23 are dropped onto the lower mold by opening the tip of the arm, and immediately after the arm is retracted from between the molds, the lower mold Ascending toward the upper mold, the glass preform sandwiched therebetween is pressed.

Around the mold, an induction heating coil 410 using a high frequency for heating it is installed. Prior to pressing the glass preform, the mold is heated by the induction heating coil 410 and maintained at a predetermined temperature. The temperature of the mold during pressing may be approximately the same as or lower than the temperature of the preheated glass preform.
Preferably, the temperature of the mold is lower than the temperature of the glass preform, thereby shortening the molding cycle time and controlling the deterioration of the mold.
The heating control by the induction heating coil 410 is performed independently for each of the upper mold and the lower mold, as will be described in detail later.

The carry-out device 42 delivers the glass optical element pressed by the press device 41 to the take-out preparation chamber 43. The carry-out device 42 includes four suction pads 42c at the tip of an arm 42b that is rotatably supported with respect to the drive unit 42a. The suction pad 42c vacuum-sucks the four glass optical elements on the lower mold of the molding die and enables the transport by the carry-out device 42. The glass optical element adsorbed by the rotation of the arm 42b is transported under the take-out preparation chamber 43 and placed on a lifting means (not shown) installed here. After the arm 42 b is retracted, the elevating means is raised, and the glass optical element is delivered to the take-out preparation chamber 43.
In this embodiment, the lens mounting surface of the elevating means closes the opening of the take-out preparation chamber 43 that communicates with the molding chamber 40, thereby disabling gas exchange between the take-out preparation chamber 43 and the molding chamber. Become. By opening the upper part of the take-out preparation chamber 43, the glass optical elements inside the robot arm and other carrying-out means are sequentially carried out to the outside. After carrying out the glass optical element, the take-out preparation chamber 43 is sealed and filled with an inert gas.

[Pressing equipment]
Next, a press apparatus will be described.
FIG. 2 is a schematic plan view of a pressing device of the glass optical element manufacturing apparatus according to the present embodiment, and FIG. 3 is a side sectional view showing the main part structure. FIG. 3 also shows a schematic configuration of the power source and the temperature control means.
In this press apparatus, the upper mold and the lower mold each have a mother mold and a mold. The upper mother die 411a and the lower mother die 411b are long and attached to the upper main shaft 412a and the lower main shaft 412b, respectively. Two to ten (four in the drawing) upper mold 413a and lower mold 413b are attached to the upper mold 411a and the lower mold 411b.

The upper master die 411a is attached to the upper main shaft 412a, and the upper main shaft 412a is fixed to the apparatus main body. The lower mother die 411b is attached to a movable main shaft 412b that is driven by a servo motor (not shown). Thereby, in each process (mold heating process, raw material supply process, pressurization process, mold release process, take-out process) of the molding process, the lower mother mold 411b is placed above the first position where the upper and lower molds 413a and 413b are close to each other. While moving between the shaping | molding die 413a and the 2nd position spaced apart by predetermined distance, it can be made to stop in a 1st position and a 2nd position, respectively.
The upper and lower mother dies 411a and 411b are brought into and out of contact with each other by sending a drive signal to a servo motor by a molding control unit (not shown) in accordance with a predetermined molding cycle.
In the press device of this embodiment, only the lower mother die can be moved, but only the upper mother die or both the upper and lower mother dies may be moved.

  An upper induction heating coil (upper heating coil) 410a around which the upper mother die 411a is wound is disposed at a position where the upper mother die 411a is fixed. In addition, for the lower mother die 411b, when the lower mother die 411b stops at the first position and the second position, the lower mother die 411b is wound around the first position and the second position so as to be wound around the first die. An induction heating coil (first heating coil) 410b-1 and a second induction heating coil (second heating coil) 410b-2 are provided. Moreover, the lower mold | type heating coil has the switch 420 for selectively heating the 1st heating coil 411b-1 and the 2nd heating coil 411b-2.

The vertical distance (vertical direction) separation distance S between upper die heating coil 410a and lower die heating coil 410b-1 is preferably 0.7 to 2 times the average coil pitch P of the upper and lower heating coils. It is preferably 8 to 1.5 times. If the distance between the upper die heating coil 410a and the lower die first heating coil 410b-1 in the vertical direction (vertical direction) is made smaller than the above range, the upper die is likely to warp due to the temperature rise of the upper and lower die facing surfaces. On the other hand, if it is larger than the above range, when the lower mold is heated at the first position, the upper and lower molds do not come close to each other, and the heating efficiency of the opposing surfaces of the upper and lower molds deteriorates.
In this embodiment, since the upper heating coil 410a and the lower first heating coil 410b-1 are arranged close to each other, both coil separation distances are substantially the same as the average coil pitch.

Note that, as will be described in detail later, the upper die heating coil 410a and the lower die heating coil 410b are connected to independent power sources and temperature control units, respectively, and their outputs can be controlled independently. .
Thereby, even if the heat capacities of the upper mother die 411a and the lower mother die 411b are considerably different, the same temperature can be controlled, and conversely, a desired temperature difference between the upper mother die 411a and the lower mother die 411b is given. It can also be provided. In addition, the number of turns and the arrangement range of the upper die heating coil 410a and the lower die first and second heating coils 410b-1, 410b-2 are determined in consideration of the heat capacities of the upper mother die 411a and the lower mother die 411b. .

  In addition, when the upper mother die 411a and the lower mother die 411b are heated by the independent power source and the heating coil in this way, compared to the case where they are heated by a single coil, the upper mother die 411a and the lower mother die 411b are opposed to each other on the opposite surface side. The lens can prevent the temperature from rising further and prevent the base mold from warping. Therefore, the high precision lens that causes the problem of decentration accuracy (tilt of upper and lower mold optical axis tilt) due to warpage. Is particularly advantageous. Furthermore, the prevention of warpage enables the positioning of the upper and lower mother molds to be accurately performed, and is effective in improving the eccentricity accuracy (horizontal deviation of the upper and lower mold optical axes: decentering).

The materials of the upper and lower mother dies 411a and 411b generate heat by induction heating and use heat-resistant heating elements. For example, a tungsten alloy or a nickel alloy can be used as the heating element. For the upper and lower molds 413a and 413b, for example, a ceramic such as silicon carbide or silicon nitride, or a cemented carbide can be used.
Here, as the heating elements of the upper and lower mother dies 411a and 411b, it is preferable to use one having a coefficient of thermal expansion close to that of the forming dies 413a and 413b. For example, when ceramic is used as the mold material, it is preferable to use a tungsten alloy or the like as the heating element.
A release film can be provided on the molding surfaces of the upper and lower molding dies 413a and 413b. As the release film, a film mainly composed of noble metals (Pt, Ir, Au, etc.) or carbon can be applied. A carbon film is particularly suitable because it is inexpensive and has an excellent release effect.

In addition, since the upper and lower mother dies 411a and 411b are configured to be completely separated at the time of material supply and product removal, when the upper and lower mother dies 411a and 411b are brought close to each other at the time of pressing, the upper and lower mother dies 411a and 411b are precise. Positioning is required. Therefore, guide pins 415a and guide holes 415b for positioning the upper and lower mother dies 411a and 411b are provided. In this embodiment, a guide pin 415a is projected from the upper mother die 411a, and a guide hole 415b is provided in the lower mother die 411b.
Further, sleeves 414a are provided on the outer periphery of the four upper molding dies 413a, and sleeve holes 414b for fitting with the sleeves 414a are provided on the outer periphery of the four lower molding dies 413b. Thus, when the upper and lower mother dies 411a and 411b approach each other, the sleeve 414a of the upper mold 413a slides and fits with the lower mold 413b with a narrow clearance, so that the upper and lower molds 413a and 413b can be positioned more precisely. Done. As a result, the eccentricity accuracy (decenter and tilt) can be maintained within a predetermined range.

The clearance between the guide pin 415a and the guide hole 415b for positioning the upper and lower mother dies 411a and 411b is preferably 10 to 40 μm, and the boss diameter of the sleeve 414a of the upper mold 413a and the boss diameter of the lower mold 413b The clearance is preferably 1 to 10 μm. In either case, if the clearance is smaller than the above range, the sliding does not go smoothly, and if the clearance is larger than the above range, the rattling occurs and the positioning accuracy is lowered.
The upper and lower mold positioning members are not limited to the above example, and a protruding member may be provided on the lower mother mold (lower mold) side, or only one of the guide member and the sleeve member may be provided. It may be provided.

As shown in FIG. 3, the heating coils 410a and 410b in the present embodiment include independent power sources (upper power source 416a and lower power source 416b) and temperature control units (upper mold temperature control unit 417a and lower mold temperature control unit). 417b). The upper mold power source 416a independently supplies current to the upper mold heating coil 410a, and the lower mold power supply 416b independently supplies current to the lower mold heating coil 410b.
In the present embodiment, the upper mold heating coil 410a, the upper mold power source 416a, and the upper mold temperature control unit 417a constitute an upper mold heating means, and the lower mold heating coils 410b (410b-1, 410b-2), The lower mold power source 416b, the lower mold temperature controller 417b, and the switch 420 constitute a lower mold heating means.

The oscillation frequencies of the upper mold heating coil 410a and the lower mold first heating coil 410b-1 are made different. Here, the ratio of the upper mold heating coil 410a and the lower mold of the first heating coil 410b-1 of the oscillation frequency: 1.5 to 1: 7 and is Ru can be.
If the oscillation frequency of the upper mold side and the lower mold side are greatly different, the heating environment such as the penetration depth of induction heating and the energy transfer efficiency from the coil will be different, and the upper and lower press molding conditions will be different. In this range, the upper and lower heating environments are substantially the same, which is preferable. In addition, within the above range, the oxidation of the matrix due to heating is also at the same level, so the heat radiation conditions that are affected by the surface state are also substantially the same. More preferably, it is 1: 1.5 to 1: 3, and particularly preferably 1: 1.5 to 1: 2.
The oscillation frequency of the upper mold heating coil 410a and the lower mold first heating coil 410b-1 may be increased on either side, but is supplied to the coil having the smaller heat capacity of the upper mold and the lower mold. It is preferable to increase the frequency of the power supply.

Both the upper mold power source 416a and the lower mold power source 416b preferably have an oscillation frequency in the range of 15 to 100 kHz. This is because when the frequency of the power source exceeds 100 kHz, the penetration depth of induction heating becomes small (shallow), only the surface portion of the mother die becomes high temperature, the radiation heat loss to the surroundings is large, and it is arranged in the mother die. This is because the heating efficiency of the mold is reduced. A high frequency is not preferable in terms of cost.
On the other hand, if the oscillation frequency is less than 15 kHz, an audible frequency band is obtained, resulting in an unpleasant sound or noise. For example, the oscillation frequency of the upper mold power supply 416a and the lower mold power supply 416b can be set to 15 to 30 kHz for one and 20 to 50 kHz for the other.

  The frequency of the lower heating coil 410b-2 can be set as appropriate, but when the first heating coil 410b-1 and the second heating coil 410b-2 are operated by a single power source as in this embodiment. It is preferable to oscillate at the same frequency. In this case, the oscillation frequency of the second heating coil 410b-2 is also preferably in the range of 15 to 100 kHz, for example, 20 to 50 kHz. In addition, it is preferable to take noise countermeasures (shield, noise filter, etc.) on the circuit of the upper and lower heating means.

When the lower mother die 411b is in the first position close to the upper mother die 411a, the lower die heating means supplies current to the first heating coil 410b-1 by the switch 420, and the lower mother die 411b becomes the upper mother die. When in the second position separated from 411a, current is supplied to the second heating coil 410b-2. Thus, when the lower master die 411b is in the first position, the lower main shaft 412b is prevented from being damaged or expanded by heating by the second heating coil 410b-2, and also efficient in terms of power consumption. Is. At the time of switching, it is preferable to leave a certain time (for example, 0.5 to 2 seconds) after the current of the first heating coil 410b-1 is interrupted until the current is supplied to the second heating coil 410b-2. . If it does in this way, heating of heating coil 410b-2 can be stopped while a lower mother die is moving.
The separation distance between the first heating coil 410b-1 and the second heating coil 410b-2 is determined by the vertical movement distance of the lower mold, but if this distance is too large, the lower mold movement distance becomes longer. The molding surface of the mold falls due to the moving atmosphere. On the other hand, if the separation distance is too small, it interferes with the supply of the preform and the removal of the molded optical element. Therefore, the distance L between the first heating coil 410b-1 (lower end) and the second heating coil 410b-2 (upper end) is set to 20 to 80 mm, for example.

  The temperature control of the upper mold 413a and the lower mold 413b is performed by controlling the outputs of the upper mold temperature sensor (thermocouple) 418a and the lower mold sensor (thermocouple) 418b provided in the respective mother molds 411a and 411b, respectively. It is input by the control unit 417a and the lower mold temperature control unit 417b and performed by, for example, PID control so that the set temperature is reached. Even when the capacities of the upper and lower mother dies 411a and 411b are significantly different, the upper mold 413a and the lower mold 413b are independently controlled in temperature according to the heat capacity and power supply capacity of the mother die to reach the target temperature. be able to. Further, by adjusting the outputs of the upper and lower mold power supplies 416a and 416b in accordance with the heat capacity ratio of the upper and lower mother dies 411a and 411b, the upper mold 413a and the lower mold 413b can be set at the target temperature with substantially the same temperature rise time. Can be reached.

The upper and lower mother dies 411a and 411b are contacted and separated by sending a drive signal to a servo motor by a molding control unit (not shown) according to a predetermined molding cycle. That is, when supplying the glass preform, the lower mother die 411b is stopped at the second position spaced apart from the upper mother die 411a, and the upper and lower mother dies 411a and 411b are brought close to each other in order to set the upper and lower die to a predetermined temperature. It can be stopped at the first position. When the glass preform is supplied, the glass preform is supplied to the upper part of the lower mold 413b by the transport device 23 from between the upper and lower mother dies 411a and 411b. Further, when pressure-molding the glass preform, the lower mother die 411b is pressed against (adhered to) the upper mother die 411a and a predetermined load is applied.
Further, when taking out the pressed optical element, the lower mother die 411b is lowered to the second position and stopped. Then, the optical element molded by the carry-out device 42 is taken out between the upper and lower mother dies 411a and 411b. Here, the lower base mold position when supplying the glass preform and the lower base mold position when taking out the pressed optical element are the same position (second position). However, this position is not necessarily the same. Any position that can be sufficiently heated by the second heating coil that winds the lower mother die may be used.

  The upper mold heating coil 410a and the lower mold first heating coil 410b-1 may be energized in a time-sharing manner. In this case, as shown in FIG. 4, the time division control unit 430 controls the energization time of the upper die power source and the lower die power source. The upper heating coil 410a and the lower first heating coil 410b-1 are alternately energized by the gate signal from the time division control unit 430. An example of the gate signal at this time is shown in FIG. The energization time can be about 0.75 seconds, and the energization stop time can be about 0.1 seconds.

[Glass optical element manufacturing method]
An embodiment of a method for producing a glass optical element according to the present invention using the glass optical element producing apparatus having the above configuration will be described with reference to FIG.
(A) Mold heating process Since the upper and lower molds in the state where the previous molding cycle has been completed are cooled to a temperature near or below Tg, it is necessary to heat them to a temperature suitable for press molding. Therefore, the lower mother die 411b is moved to a first position close to the upper mother die 411a and stopped. At this time, since the lower mother die 411a is wound around the first heating coil, an electric current is passed through the first heating coil 410b-1 and the heating coil 410a winding the upper die to cause the upper and lower mother die to generate heat. The upper and lower molds are heated to a predetermined temperature by this heat conduction (see FIG. 7A). At this time, it is important to minimize the variation in temperature among the plurality of molds.
The temperature setting values of the upper and lower molds are usually the same for both the upper and lower molds, but a temperature difference may be provided between the upper and lower molds depending on the shape and diameter of the lens to be molded.
In addition, since the heat capacities of the upper and lower mother dies are different and the heating efficiency is often different, the number of high-frequency coil turns and the output range are determined in consideration of this point.

  In the molding apparatus of the present embodiment, the upper die heating coil 410a and the lower die first heating coil 410b-1 are arranged close to each other in order to heat the upper and lower mother dies at the close positions. As described above, the distance between the heating coils 410a and 410b-1 is preferably 0.7 to 2 times the coil pitch. When these heating coils 410a and 410b are separated from each other by a large distance with respect to the coil pitch, when the upper and lower mother dies 411a and 411b are heated, the sleeves 414a and the like projecting on the opposing surfaces of the upper and lower mother dies 411a and 411b, etc. The member is not easily heated and heat is easily taken away. This causes the heating time to be extended and the cycle time to become longer, and causes the poor fitting when the sleeve 414a is positioned by fitting with the lower mold 413b and the poor elongation of the molding material. It becomes.

In the case of the present embodiment, the protruding members such as the sleeve 414a and the guide pin 415a provided on the upper mother die 411a are brought into contact with or fitted into the sleeve hole 414b and the guide hole 415b of the lower mother die 411b in the die heating process. It can be in a state. In this way, when the mold heating is performed by contacting or fitting the protruding member such as the sleeve 414a and the guide pin 415a and the sleeve hole 414b and the guide hole 415b, the exposed portion of the protruding member is reduced, and cooling by the atmosphere is suppressed. Heating of the protruding portion is sufficiently performed.
However, even if they are not in contact with each other, it is sufficient that a space capable of preventing convection of the atmospheric gas can be formed by the upper and lower opposing surfaces and the protruding member.

The temperature setting values of the upper and lower mother dies 411a and 411b may be the same in the upper and lower sides or may be provided with a temperature difference. For example, depending on the shape and diameter of the optical element to be molded, the lower base 411b is set to a higher temperature than the upper base 411a, or the lower base 411b is set to a lower temperature than the upper base 411a. The temperature of the upper and lower mother dies 411a and 411b can be equivalent to 10 ⁸ to 10 ¹² poise in terms of the viscosity of the glass preform. In the case of providing a temperature difference between the upper and lower mother dies 411a and 411b, a range of 2 to 15 ° C. is preferable.
The temperature control of the upper and lower mother dies 411a and 411b is performed by using the outputs of the upper die temperature sensor (thermocouple) 418a and the lower die sensor (thermocouple) 418b provided in the respective mother dies 411a and 411b as the upper die temperature controller 417a. And it inputs into the lower mold | type temperature control part 417b, for example, performs PID control so that it may become preset temperature.
When the target temperature is approached, the current supplied may be reduced to reduce the output of the heating coil.

As described above, by making the oscillation frequency of the upper mold heating coil 410a and the lower mold first heating coil 410b-1 different from each other, the unstable heating due to mutual interference even if they oscillate simultaneously at close positions. And unpleasant noise can be prevented. Further, when the upper die heating coil 410a and the lower die first heating coil 410b-1 oscillate in a time-sharing manner, mutual interference can be further reduced.
The mold heating process can be performed for an arbitrary time depending on the size (heat capacity) of the master mold and the power supply capacity, and is, for example, about 20 to 40 seconds.
In this manner, the upper and lower mold temperature control can be performed independently and quickly.

(B) Material supply process The lower mother mold 411b heated in the mold heating process is lowered to the second position, and the upper mold and the lower mold are separated. The preform (glass material) is conveyed and supplied from there and placed on the lower mold.
Here, when the heating in the mold heating process is completed, the switching unit 420 cuts off the supply of current to the first heating coil 410b-1. When the lower mother die 411b moves to the second position and stops, the switching device 420 supplies a current to the second heating coil 410b-2 disposed at the second position, thereby causing the second heating coil to move. Heat. Therefore, the lower mold mother 411b is heated without interruption even when the mold is opened for supply of the material and stopped at the second position, so that the time required to reach the desired temperature can be minimized. .
In addition, since the upper and lower mother molds approach the target temperature in the mold heating process, the heating output in the material supply stage can be made lower than that in the mold heating process (see FIG. 7B). At this time, the temperature distribution generated in the mother die becomes small, and it is possible to achieve a uniform temperature between the plurality of molding dies.

The glass material is supplied by using a glass material that has been pre-formed into a predetermined shape with an appropriate weight and softened to a viscosity suitable for molding, or a glass material that is lower than the temperature suitable for molding. May be supplied between the upper mold and the lower mold and further heated in the mold. When the glass material is heated to a temperature higher than the set temperature of the mold in advance to supply a softened glass material (so-called non-isothermal press), it is necessary to precisely control the mold temperature. It is preferred to implement. This also shortens the molding cycle time and improves production efficiency.
The temperature of the glass material at this time is set to a temperature less than 10 ⁹ poise, preferably 10 ⁶ to 18 ⁸ poise.
When the softened glass material is transported and placed on the lower mold, if the glass material comes into contact with the transport member and a defect occurs on the surface, the surface shape of the optical element to be molded is affected. It is preferable to use a jig that conveys the glass material that has been floated by gas and drops the glass material onto the lower mold.
The material supply step is preferably as short as possible, but is, for example, about 1 to 5 seconds.

(C) Pressurization process The upper mold, the lower mold, and the glass material are in a predetermined temperature range, and the glass material is heated and softened, the lower base mold 411b is raised to the first position, and the upper and lower molds are pressed ( The glass optical element having a predetermined surface shape is formed by applying pressure and transferring the molding surface of the upper and lower molds. The lower mold is raised by operating a driving means (for example, a servo motor). When the glass material is supplied in a heated and softened state, pressurization is performed immediately after the supply.
The ascending stroke of the lower mold for pressurization is a value set in advance from the thickness of the optical element to be molded, and is set to an amount that is determined in consideration of heat shrinkage of the glass in the subsequent cooling step. The pressurization schedule can be arbitrarily set according to the shape and size of the optical element to be molded. After initial pressurization, the load is released and then secondary pressurization is performed. A pressurizing method can also be employed.
When the pressurization process is started, it is preferable to cut off the current supply to the heating coils 410a and 410b in order to shorten the production cycle time (see FIG. 7C). Thereby, the temperature rise of the upper and lower mother dies can be stopped and the cooling can be started.
The pressurizing step is preferably as short as possible, but for example, about 1 to 10 seconds.

(D) Cooling / Release Step While maintaining the pressurization or reducing the pressurization, the molded glass optical element and the mold are kept in close contact, and the viscosity of the glass reaches a temperature equivalent to 10 ¹² poise. After cooling down to mold release. The mold release temperature is preferably equal to or lower than the temperature corresponding to 10 ^12.5 poise, and more preferably in the temperature range corresponding to 10 ^12.5 to 10 ^13.5 poise from the viewpoint of shortening the production cycle time. Also in this case, the lower mother die 411b is in the first position, but current supply to the first heating coil 410b-1, that is, heating is not performed. Note that the upper mother die 411a is not heated (see FIG. 7D).
On the other hand, depending on the composition of the glass material (phosphate glass, borate glass, etc.) or depending on the shape of the optical element (concave meniscus lens, etc.), when forming an optical element that is prone to cracking After the pressurization process is started, the temperature can be lowered while continuing to supply current to the heating coils 410a and 410b-1. In such a case, the effect of the heating device of the present invention, which can freely control the temperature while the upper and lower mother dies are in contact, is remarkable.
The time required for the cooling step is arbitrarily set according to the shape, thickness, diameter, required surface accuracy, and the like of the optical element, and is, for example, about 25 to 40 seconds.

(E) Taking-out process The glass optical element shape | molded from between the spaced apart upper and lower shaping | molding molds is automatically taken out by the taking-out arm etc. which provided the adsorption | suction member. At this time, the lower mother die 411b is lowered to the second position. Then, the current is again supplied from the upper mold power source 416a to the upper mold heating coil 410a, and the current is also supplied from the lower mold power supply 416b to the lower mold second heating coil 410b-2 via the switch 420. The upper mother die and the lower mother die are heated by the heating coil. That is, the temperature rise of the upper and lower mother dies is started for the next molding cycle (see FIG. 7E).
The taking-out process is, for example, about 1 to 6 seconds.

Continuous press molding is performed by repeating the above steps. The time required for this molding cycle is preferably about 45 to 95 seconds, for example.
In this embodiment, the upper mold is fixed and the lower mold is movable. However, the upper mold may be movable and the lower mold may be fixed, or both the upper mold and the lower mold may be movable. .

  The optical element produced by the method of the present invention can be, for example, a lens, and there is no particular limitation on the shape, and it can be a biconvex, concave meniscus, convex meniscus, or the like. In particular, even when the lens has a medium outer diameter of about 15 to 25 mm, the thickness and the eccentricity accuracy can be maintained well. For example, the thickness accuracy is within ± 0.03 mm. As for the eccentricity accuracy, the present invention can be suitably applied to the manufacture of a tilt within 2 minutes and a decenter within 10 μm.

Next, the result of the Example which manufactured the glass optical element using the shaping | molding apparatus and manufacturing method of this invention is shown.
Example 1
1-3, press the flat sphere preform of barium borosilicate glass (transition point 515 ° C., yield point 545 ° C.) by the steps of FIGS. An example in which a biconvex lens having a diameter of 18 mm (one surface is spherical, the other surface is aspheric, the spherical radius of curvature is 50 mm, the aspherical paraxial radius of curvature is 28.65 mm, and the center thickness is 2 mm) is shown below.
This lens has a brim-shaped flat portion around the periphery, and by comparing the maximum thickness and the minimum thickness of this portion, the tilt of the upper mold and the lower mold, that is, the molding tilt can be measured.

Four sets of this biconvex mold and sleeve were attached to the upper and lower mother dies. The volume ratio (= heat capacity ratio) of the upper and lower molds was 10: 7. The upper power supply of this apparatus had a maximum output of 30 kW and a frequency of 18 kHz, and the lower power supply had a maximum output of 30 kW and a frequency of 35 kHz.
In the heating step (a), the upper and lower mother molds are heated, and at the same time, the glass preform is heated in a separate furnace (not shown) in a split-type floating dish (glassy plate on the openable / closable support arm shown in FIG. (Made of carbon) and softened by heating while being levitated by an air current ejected from below. The preform was dropped and supplied to the lower mold by dividing the floating dish. At this time, the preheating temperature of the preform and the mold was 625 ° C. (corresponding to 10 ⁷ poise in terms of glass viscosity) and 580 ° C. (corresponding to 10 ^8.5 poise in terms of glass viscosity). Immediately after the drop supply, the support arm was moved backward to raise the lower mother die and the press (pressure was 150 kg / cm ² ) was started.
After the pressurization was started, heating was performed without heating until the upper and lower mother molds contacted each other. Next, at the same time as nitrogen gas was injected onto the side surface of the mother body, nitrogen gas was circulated in the mother mold and cooling was started.

  Then, while maintaining the contact between the mold and the glass, it is cooled to a temperature below the transition point, the lower base mold is lowered, heating by the lower mold second heating coil is started, and a press-molded product is provided by a take-out device equipped with a suction pad. The lens was taken out. Immediately after removal, heating of the upper and lower matrixes was started and the next press cycle was continued. In this apparatus, the heating rate of the upper and lower mother dies was almost the same, and the molding cycle time was 60 seconds. Table 1 shows the performance of the four molded lenses.

  Here, the molding tilt is the lens eccentricity caused by the inclination of the upper die and the lower die, and the molding decenter is the lens eccentricity caused by the horizontal shift of the upper die and the lower die. The aspherical eccentricity was measured using a known aspherical measuring machine, and the molding tilt was calculated from the difference between the minimum thickness and the maximum thickness of the flat portion around the molded lens and the press diameter of the lens. The relationship between the aspherical eccentricity, the molding tilt, and the molding decenter is as shown in FIG. 9, and the molding decenter was obtained from this relationship. All four satisfy the specifications including surface accuracy.

As described above, even if a plurality of (four in the above example) molds were provided on the long base and four presses were performed simultaneously, good results could be obtained. In other words, even if the mother die grows in order to mold a large number of lenses with a single press, heating of the mother die, particularly the moving mother die, is efficiently performed via a plurality of heating coils and a switch. Therefore, it is possible to perform molding while maintaining high eccentricity accuracy (tilt, decenter).
In addition, since the upper and lower heating means are independent, warpage of the mother die is suppressed, and the optical performance of the lens by the molds at both ends is not deteriorated, enabling stable production.
In addition, since the thermal deformation of the mother die is suppressed, even if the clearance of the positioning member when the upper and lower dies approach each other, poor fitting and friction do not occur. As a result, the coaxiality of the upper and lower molds was improved, and the eccentric accuracy of the molded lens could be further increased.
Therefore, for example, the present invention can also be applied to an objective lens of an optical pickup having extremely strict decentration accuracy.

FIG. 1 is a schematic plan view showing an embodiment of a mold press forming apparatus to which the present invention is applied. FIG. 2 is a schematic plan view of the pressing apparatus in FIG. FIG. 3 is a diagram showing a schematic side section of the pressing apparatus shown in FIG. 2 and a power supply circuit. FIG. 4 is a diagram showing a schematic side section and a power supply circuit when a time-sharing device is added to the pressing device shown in FIG. FIG. 5 is a diagram showing an energization state to each heating coil during time-division heating. FIG. 6 is a schematic plan view of the levitation pan / support arm. FIG. 7 is a diagram showing the relationship between the mold and the heating coil during heating, and the relationship between the energized state of each heating coil and the mold temperature. FIG. 8 is a diagram showing thermal deformation (warping) of the mother die. FIG. 9 is a diagram showing the relationship between the molding eccentricity and the aspherical type.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical glass manufacturing apparatus 20 Heating chamber 40 Molding chamber 41 Press apparatus 410a Upper mold heating coil 410b-1 Lower mold first heating coil 410b-2 Lower mold second heating coil 411a, 411b Mother mold 413a, 413b Molding mold 416a, 416b High frequency power source 417a, 417b Temperature controller 410a, 418b Temperature sensor 420 Switch 430 Time division controller

Claims (4)

And fixed and mobile, which are disposed to face in the molding chamber, said mobile, said first position and said moving type mobile is close to or in contact with the fixed mold is separated a predetermined distance from the fixed mold A movable main shaft that is moved between the second position and stopped at the first position and the second position, and a heating coil that induction-heats the fixed mold and the movable mold, respectively, are installed in the molding chamber . A stationary mold heating means and a movable mold heating means; and a power source provided independently to supply current to each of the heating coils provided in the stationary mold heating means and the movable mold heating means, It said mobile heating means, a first heating coil for heating the movable die when in the first position, and a second heating coil for heating the movable die when in the second position, the first One heating coil To said second heating coil, when the molding material is press-molded using a press molding device having a switching means for selectively energizing current from said power source,
The mobile is Ri said first position near said the Rutoki said periphery of the movable head second heating coil is not ready to be wound, without energizing the second heating coil, for the fixed The heating coil of the heating means and the first heating coil are energized at different frequencies with a ratio of the transmission frequencies of 1: 1.5 to 1: 7, or the heating coil of the stationary mold heating means and the first heating coil Energize the first heating coil in a time-sharing manner,
When the movable mold is in the second position, the heating coil of the fixed mold heating means and the second heating coil are energized simultaneously,
A mold press molding method characterized by switching energization to the first heating coil and the second heating coil.   2. The mold press forming method according to claim 1, wherein after the current to the first heating coil is interrupted, energization to the second coil is started at a predetermined interval. 3. A mold heating process for heating the upper mold and the lower mold in a state of being close to or in contact with each other; a material supply process for opening the upper mold and the lower mold and supplying a preheated optical element material; and In a method of manufacturing an optical element, including a molding step of press-molding an optical element by pressurizing a mold and a lower mold, and an extraction step of opening the upper mold and the lower mold and taking out the molded optical element from between the upper mold and the lower mold,
An optical element manufacturing method, wherein the optical element is manufactured using the mold press molding method according to claim 1. In the mold heating step, the second heating coil is not energized, and the heating coil of the stationary mold heating means and the first heating coil are energized at different frequencies, respectively, or the stationary mold heating means The heating coil and the first heating coil are energized in a time-sharing manner,
4. The method of manufacturing an optical element according to claim 3, wherein in the material supplying step, the heating coil and the second heating coil of the fixed mold heating unit are energized simultaneously.

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