JP5121553B2 - Optical element molding method - Google Patents

Description

  The present invention relates to a method for molding an optical element that is heat-treated when molding an optical element material.

A method for molding an optical element in the prior art will be described below with reference to FIG.
FIG. 7 is a block diagram showing the concept of a conventional optical element molding method. As shown in FIG. 7, a mold for molding an optical element material 13 made of, for example, glass or the like is divided into upper and lower parts to form a first mold 14 and a second mold 15, and the first mold 14, An optical element enclosed in the first and second molds 14 and 15 by putting the optical element material 13 between the second molds 15 and conducting heat from the heated first and second molds 14 and 15. By heating the material 13, high precision molding is to be realized.

Generally, the first and second molds 14 and 15 are heated by bringing the heater block 16 such as a heater cartridge using a heating wire and the first and second molds 14 and 15 into contact with each other, thereby heating the heater block. Heat is transferred from 16 to the first and second molds 14 and 15, or the first and second molds 14 and 15 themselves are heated by induction heating, or the first and second molds are heated by a heating lamp. There is a method of heating 14 and 15 themselves.
JP 2007-099527 A

  However, in the conventional optical element molding method as described above, the optical element material 13 is heated by the heat transfer action by heating the molds 14 and 15 in any of the cases described above. The temperature of the element material 13 is the same as or lower than that of the molds 14 and 15. Furthermore, since the optical element material 13 and the molds 14 and 15 are heated from the part in contact, the temperature distribution unevenness also occurs in the optical element material 13 itself.

  At this time, the surface of the optical element material 13 has a high temperature, but the inside is in a low temperature state. When the optical element material 13 is large, the temperature at which the internal temperature of the optical element material 13 can be molded (transition point). When the temperature rises, the surface temperature becomes too high, and the shape of the optical element material 13 has already reached the freezing point temperature (10 to 30 ° C. higher than the transition temperature) before molding, or further melting begins. For this reason, the surface of the optical element material 13 may be locally deformed, the bubbles may be entrained due to non-uniform elongation of the optical element material 13 due to the temperature, or the appearance of white fogging due to the modification of the surface of the optical element material 13 due to high temperature Cause a bug.

  Further, even when the optical element material 13 is small, as in the case of a spherical optical element material as shown in FIG. Since it starts, it becomes difficult to maintain a spherical shape until pressing, and furthermore, the optical element material 13 is fixed with the first mold 14 and the second mold 15, and the contact point with the molds 14 and 15. The surface is rapidly heated to modify the surface of the optical element material 13 to generate minute cracks, or to cause compositional irregularities such as stria peculiar to glass by once melting and re-solidifying. In addition, the optical characteristics and appearance quality may be adversely affected.

  On the other hand, as disclosed in Patent Document 1 described above, in order to make the temperature of the optical element material 13 uniform, a predetermined weight or volume is dropped from the molten optical element material 13 and induction heating is performed. There is a method of maintaining the temperature, but there is a difficulty in stabilizing the shape of the optical element material 13 when it is dropped and when it is received by a mold or the like.

  The present invention solves the above-mentioned conventional problems, can suppress deformation of the optical element material during the heat treatment during molding of the optical element material, and further improve the shape and appearance quality during molding. Provided is a method for molding an optical element.

In order to solve the above-described problem, the method for molding an optical element according to claim 1 of the present invention is the method in which each of the molding die including the first die and the second die is brought close to and heated. A method for molding an optical element, wherein an optical element material is inserted into a mold, and the optical element material inserted into the mold is sandwiched between the first mold and the second mold. Before inserting the optical element material into the mold, a heating drum in which spiral grooves are formed in the circumferential direction of the inner wall is moved to a predetermined position by an induction heating coil wound around the outer periphery of the heating drum. The surface temperature of the optical element material is changed by rotating the optical element material while being heated to a temperature and moving the optical element material while rolling along the groove . Internal temperature At low temperature state than, characterized by inserting an optical element material within said mold.

Further, the optical element molding method according to claim 2 of the present invention is the optical element molding method according to claim 1 , wherein a minute protrusion is provided on at least one of the bottom surface and the side surface of the groove, The optical element material is prevented from being fused to the inner wall of the heating drum.

The optical element molding method according to claim 3 of the present invention is the optical element molding method according to claim 1 , wherein a plurality of induction heating coils are wound around the heating drum, and the induction heating coil is used. The temperature distribution in the longitudinal direction of the heating drum is changed by controlling induction heating.

The optical element molding method according to claim 4 of the present invention is the optical element molding method according to claim 3 , wherein the optical element material in the heating drum is used as the temperature distribution of the heating drum. The temperature of the take-out port side is set lower than that of the central portion of the heating drum, and the temperature of the central portion of the optical element material is set higher than that of the surface portion.

The optical element molding method according to claim 5 of the present invention is the optical element molding method according to claim 1 , wherein the optical element material heated to the predetermined temperature is taken out. The optical element material is allowed to pass through the heating drum for a predetermined time while rolling.

  As described above, according to the present invention, by rotating the heating drum in which the spiral grooves are formed by induction heating, the spherical shape is maintained well with respect to the optical element material before molding. Can be heated.

  As a result, it is possible to suppress deformation of the optical element material during the heat treatment during molding of the optical element material, and it is possible to further improve the shape and appearance quality at the time of molding.

Hereinafter, a method for molding an optical element according to an embodiment of the present invention will be specifically described with reference to the drawings.
Before describing the optical element molding method of the present embodiment, first, an optical element material molding apparatus used in the present embodiment will be described.

  FIG. 1 is a block diagram showing the concept of an optical element material molding apparatus used in the optical element molding method of the present embodiment. As shown in FIG. 1, the optical element material forming apparatus used here encloses an optical element material 1 (hereinafter referred to as a glass material 1), and is subjected to shape processing to form it into a predetermined shape. It consists of a first mold 2 and a second mold 3.

  The first mold 2 and the second mold 3 are heated by the heat transfer action from the heater block 4 in contact with each of them, and further the glass material 1 heated to a predetermined temperature (above the transition temperature) by the heating unit 5. The first mold 2 and the second mold 3 are placed between the first mold 2 and the second mold 3, reheated or cooled by heat transfer from the first mold 2 and the second mold 3, and the first mold 2 and the second mold. The glass material 1 is crushed and cooled by applying pressure while approaching the distance 3 to form a predetermined shape.

  At this time, it is desirable that the glass material 1 has a spherical shape or a rollable shape. As for the method of crushing the glass material 1, the method of cooling the glass material 1 by crushing it with a pressing force and forming it into a predetermined shape can also be applied while setting the temperature of the glass material 1> the mold temperature. It is also possible to use a method of forming over.

At this time, the heater block 4 may be a heater cartridge using a heating wire or a cartridge by induction heating.
Next, the heating method of the glass material 1 by the heating unit 5 will be described with reference to FIG.

  FIG. 2 is a conceptual diagram showing a structural example of the heating unit in the optical element molding method of the present embodiment, and the center diagram is a cross section when the heating unit is viewed from the direction perpendicular to the rotation axis of the heating drum. The structure on the left side shows the structure when the heating unit shown in the center is viewed from the left side of the drawing, and the figure on the right side shows the structure when the heating unit shown in the center is viewed from the right side of the drawing. Show.

  As shown in FIG. 2, the heating unit 5 shown in FIG. 1 includes a heating drum 6 for uniformly heating the glass material 1, a temperature sensor 7 for measuring the temperature of the heating drum 6, and a heating drum 6 at a predetermined temperature. An induction heating coil 8 for heating the heating drum 6, a driving portion 9 for rotating the heating drum 6, and a guide roller 10 that is a supporting portion of the heating drum 6.

  A controller is attached to the drive unit 9 so that the heating drum 6 can be rotated at a predetermined rotational speed by a motor or the like. The guide roller 10 regulates the rotation axis J1 of the heating drum 6 so as not to shift, and it is preferable to use a heat insulating material or the like in consideration of the heating drum 6 becoming high temperature.

  On the inner wall side of the heating drum 6, a spiral groove M1 is provided in the circumferential direction. Considering the expansion of the glass material 1 due to heating, the spiral groove M1 is preferably the same as or slightly larger than the spherical glass material radius, and preferably has an arc-shaped cross section. If the diameter of the glass material 1 is 2 to 3 mm, the radius R is preferably about 2 mm. As for the heating drum 6, the inner diameter is about 10 to 20 times the diameter of the glass material 1 to be supplied.

  Next, when the spherical glass material 1 is supplied to the charging port of the heating drum 6, the heating drum 6 is rotated so that the glass material 1 rotates along the spiral groove M1 while the glass material 1 itself rotates. Proceed through 6. At this time, the heating condition of the glass material 1 is determined by the temperature of the heating drum 6, the number of rotations of the heating drum 6, and the lead of the spiral groove M <b> 1 in the heating drum 6.

  However, the groove M1 in the heating drum 6 only needs to have sufficient time to sufficiently heat the spherical glass material 1, and the time for passing through the heating drum 6 is about 1 to 2 minutes. What is necessary is just to set the rotation speed of a lead | read | reed and the heating drum 6. FIG. In order to prevent the glass material 1 and the heating drum 6 from being fused, it is preferable to increase the number of revolutions of the heating drum 6 and increase the number of leads in the groove M1.

  Further, at this time, by making the bottom surface of the spiral groove M1 uneven and / or sandy, the rotation of the glass material 1 is promoted and the glass material 1 and the heating drum 6 are prevented from being fused. It is also possible. By rotating the glass material 1, heat transfer from the heating drum 6 to the glass material 1 can be evenly applied to the surface of the glass material 1, and heating can penetrate into the inside of the glass material 1 if the passage time is long.

Next, a method for uniformly heating the heating drum 6 will be described.
The heating drum 6 prevents fusion of the glass material 1 by using a magnetic stainless steel or a non-magnetic stainless steel or ceramic coated with a magnetic film 12 as shown in FIG. By selecting a material with good thermal conductivity, uneven temperature distribution in the circumferential direction of the heating drum 6 can be prevented.

  Furthermore, as shown in FIG. 2, by winding the induction heating coil 8 around the outer periphery of the heating drum 6 in a non-contact manner, the heating drum 6 can be heated and a uniform temperature distribution can be obtained on the circumference. At this time, as the induction heating coil 8, a copper thin tube is wound, or cooling water and a heat insulating material are arranged on the inner periphery, and a coil wire is wound several times thereon, thereby heating the magnetic material with less power. The drum 6 can be efficiently heated.

  The induction heating coil 8 includes a control circuit for controlling the heating drum 6 to a predetermined temperature by measuring the temperature of the surface of the heating drum 6 with the temperature sensor 7. The temperature sensor 7 is preferably a non-contact type by measuring far infrared rays or the like, but can also be measured by a contact type such as a thermocouple.

  Further, as shown in FIG. 2, since the drive unit 9 for rotating the heating drum 6 is required, vibration due to rotation and expansion of the heating drum 6 itself due to heating can be considered. Because of the contact heating, there is an advantage that the same power can be applied even if the rotation axis J1 is displaced.

  Considering that the heating drum 6 itself expands and deforms, as shown in FIG. 4, the portion of the heating drum 6 in which the spiral groove M1 is dug is made of a magnetic material, and the outer peripheral surface of the heating drum 6 It is also possible to suppress heat conduction to the heating part 5 itself by covering the whole with the heat insulating material 12 and covering it.

  Further, by arranging two or more induction heating coils as in the induction heating coil 8 and the induction heating coil 11 shown in FIG. 3, the temperature distribution can be arbitrarily set in the direction of the rotation axis J1 (longitudinal direction) of the heating drum 6. Can be set. At this time, in order to suppress electromagnetic interference between the plurality of induction heating coils 8 and 11, it is preferable to dispose a cage formed using a copper plate or ferrite between the coils.

Next, an embodiment of the heating profile will be described with reference to FIG.
FIG. 5 is an explanatory diagram of a heating profile in the optical element molding method of the present embodiment. As shown in FIG. 5, when the spherical glass material 1 in a room temperature state is put into a heating drum 6, it is heated from the surface of the glass material 1. At this time, the heating drum 6 is set to be 5 to 10 ° C. higher than the glass transition point (Tg point) temperature of the glass material 1. About a glass transition point, although it changes with the materials of the glass material 1, many things are 500-600 degreeC. The set temperature is not limited to this depending on the molding state.

  After the glass material 1 is fed, the temperature of the glass material surface contacting the heating drum 6 rises first while the glass material 1 rolls in the heating drum 6, and the temperature inside the glass material rises with a delay, and heats for a predetermined time. Thus, the temperature of the glass material 1 can be set uniformly. At this time, the heating time is determined depending on the size and material of the glass material 1, but for the spherical glass material 1 having a diameter of about 3 mm, the heating time is about 1 to 2 minutes. At this time, since the heating drum 6 is rotating, a spherical shape can be maintained even at a temperature setting exceeding the transition point.

  Further, although the temperature difference between the heating drum 6 and the glass material 1 that has been charged is large, the heating drum 6 rotates, so that a specific portion of the glass material 1 is not rapidly heated, and the surface of the glass material 1 is heated evenly. Therefore, there is also an advantage that no minute cracks are generated on the surface of the glass material 1.

Furthermore, a plurality of glass materials 1 can be put into the heating drum 6 and heated.
When the glass material 1 heated by the heating drum 6 is molded, the relationship of the temperature of the mold <the glass material temperature can be realized, the press molding can be performed while cooling with the mold, and the heat of the glass material 1 can be reduced. It is possible to shorten the molding time by molding while absorbing heat with the molding die.

In addition, an embodiment of a heating profile when a plurality of induction heating coils 8 and 11 are used will be described with reference to FIG.
FIG. 6 is an explanatory diagram of another heating profile in the optical element molding method of the present embodiment. After the temperature of the surface and the inside of the glass material 1 becomes uniform as shown in FIG. 5, the vicinity of the outlet of the heating drum 6 is set to a temperature several degrees lower than the Tg point by another induction heating coil as shown in FIG. Accordingly, the glass material temperature can be set such that the surface temperature is less than the internal temperature at an arbitrary location inside the glass material 1.

  Further, between the first mold 2 and the second mold 3, the glass material 1 having the above surface temperature <internal temperature is introduced, and a predetermined temperature (below the Tg point or near the glass material internal temperature). ) Is controlled while being cooled and pressurized by the first mold 2 and the second mold 3 controlled to prevent local deformation of the surface portion of the glass material 1, and the elongation of the glass material 1 due to temperature is uneven. It becomes possible to prevent the entrainment of bubbles due to becoming and to form with high accuracy.

Furthermore, the glass material shape before molding can be maintained, and the center of the glass material is hot, so that the pressing time during molding can be shortened.
Further, since there is no local rapid heating from the contact point with the molds 2 and 3, the surface of the optical element material 1 is modified to generate micro cracks, or once melted and locally re-solidified. By doing so, composition irregularities such as stria peculiar to the case where the optical element material 1 is glass can be generated, and an adverse effect on optical characteristics and appearance quality can be prevented.

  At the time of pressurization, the glass material 1 is cooled between the first mold 2 and the second mold 3 in the above example. However, depending on the type of the glass material 1 and the amount of deformation caused by the molding, the first metal mold 1 may be used. The mold 2 and the second mold 3 may be pressure-molded while being heated.

  The optical element molding method of the present invention can suppress deformation of the optical element material during the heat treatment during the molding of the optical element material, and can further improve the shape and appearance quality during molding. Thus, the present invention can be applied to a molding technique such as a glass lens used in an optical instrument.

The block diagram which shows the concept of the shaping | molding method of the optical element of embodiment of this invention Configuration conceptual diagram showing an example of the structure of the heating unit in the optical element molding method of the embodiment Configuration conceptual diagram showing another structural example of the heating unit in the optical element molding method of the same embodiment Configuration conceptual diagram showing still another structural example of the heating unit in the optical element molding method of the same embodiment Explanatory drawing of the heating profile in the shaping | molding method of the optical element of the embodiment Explanatory drawing of the other heating profile in the shaping | molding method of the optical element of the embodiment Configuration diagram showing the concept of a conventional optical element molding method

Explanation of symbols

1 (Spherical) optical element material (glass material)
2 First mold 3 Second mold 4 Heater block 5 Heating unit 6 Heating drum 7 Temperature sensor 8, 11 Induction heating coil 9 Driving unit 10 Guide roller 12 Heat insulating material J1 (heating drum) rotating shaft M1 (spiral-shaped) )groove

Claims (5)

The optical element material is inserted into the mold while the respective molds composed of the first mold and the second mold are brought close to each other and heated, and the optical element material inserted into the mold is In a method for molding an optical element, which is sandwiched between a first mold and a second mold to mold the optical element material,
Before inserting the optical element material into the mold, a heating drum having spiral grooves formed in the circumferential direction of the inner wall is brought to a predetermined temperature by an induction heating coil wound around the outer periphery of the heating drum. By rotating in a heated state, the optical element material is moved while rolling along the groove, and the optical element material is heated during that time, so that the surface temperature of the optical element material becomes the internal temperature of the optical element material. A method for molding an optical element, comprising inserting an optical element material into the mold at a lower temperature. A method for molding an optical element according to claim 1 ,
Providing minute protrusions on at least one of the bottom and side surfaces of the groove,
The optical element material is prevented from being fused to the inner wall of the heating drum. A method for molding an optical element according to claim 1 ,
A plurality of induction heating coils are wound around the heating drum,
A method of molding an optical element, wherein the temperature distribution in the longitudinal direction of the heating drum is changed by controlling induction heating by the induction heating coil. A method for molding an optical element according to claim 3 ,
As the temperature distribution of the heating drum,
The temperature of the optical element material take-out side of the heating drum is set lower than the center part of the heating drum, and the temperature of the central part of the optical element material is set higher than that of the surface part. A method for forming an optical element. A method for molding an optical element according to claim 1 ,
In order to take out the optical element material heated to the predetermined temperature,
The optical element material is passed through the heating drum for a predetermined time while rolling the optical element material.

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