JP2005281106A - Mold press forming apparatus and method for manufacturing optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a forming stock from inverting upside down at feeding the forming stock by dropping it onto a lower mold. <P>SOLUTION: The subject mold press forming apparatus for press-forming the forming stock by means of an upper mold 10 and the lower mold 20 respectively having forming faces 11 and 21 opposing each other is equipped with a forming-stock feeding means 30 for feeding the forming stock by dropping it onto the lower mold 20, and a guide means 50 for controlling the posture of the forming stock in a falling passage. This guide means 50 prevents the forming stock from inverting by making the forming stock on the way of falling once come to rest and then fall again. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a precision mold press molding technology for press molding a molding material such as a glass material using a precision machined mold based on the shape of an optical element to be obtained, and in particular, a mold for performing precision mold press molding. The present invention relates to a press molding apparatus and a method for manufacturing an optical element obtained by press molding using the press molding apparatus.

  In recent years, by using a mold that has been precisely processed based on the shape of the optical element to be obtained, press molding a molding material softened by heating (for example, a glass material made of optical glass), problems such as fusion Various methods have been developed for molding high-precision optical elements (for example, glass lenses) without causing any problems (for example, see Patent Documents 1 to 6).

  In order to obtain a desired lens by such press molding, various standards such as appearance, surface shape, thickness, outer diameter, and eccentricity must be satisfied. Furthermore, in putting such a glass optical element forming method into practical use, productivity becomes a big problem. In other words, a major issue is how many glass optical elements can be produced in a shorter time.

  As a method for producing a glass material used for press forming, hot forming is known. This is a method of forming a glass lump by dropping or flowing a predetermined amount of molten glass into a receiving mold. The glass material that has been hot-formed in this way can achieve the desired volume and surface properties without the need for processing such as polishing, and has high production efficiency. Is advantageous.

  In Patent Document 1, in the hot forming of the glass material as described above, in order to prevent the occurrence of sink marks on the upper surface of the molten glass gob, or the glass gob corresponds to the radius of curvature of a forming die used in press forming. For this purpose, a process of raising the upper surface of the molten glass is described.

  Further, there are the following two methods for improving the productivity (cost efficiency) of precision mold presses. One of them is to increase the number of unit-time machining per apparatus, which is to increase the number of parallel processes per apparatus or to shorten the time required for one machining. Another method is to reduce various costs required for processing, and this includes reductions in device manufacturing costs, operating costs, molded member costs, and the like.

In order to improve the number of processing per unit time, that is, to shorten the processing time per time, it is necessary to shorten the heating / cooling cycle of the mold, and the molding conditions for that purpose, especially the glass material and the temperature of the mold during molding. Various proposals have been made regarding conditions.
For example, Patent Document 2 describes a method in which a glass material heated to a viscosity of 10 ⁷ to 10 ⁹ poise is pressure-molded with a mold having a temperature at which the glass material exhibits a viscosity of 10 ¹⁰ to 10 ¹² poise. ing.

Patent Documents 3 to 5 describe a method in which a glass material is heated and softened while being floated by an air current, and is dropped and supplied to a mold.
Furthermore, Patent Document 6 discloses a position correcting means for moving the molding to be dropped supplied onto the molding surface to the center of the molding surface.
According to these configurations, the problem that the glass material is fused to the support member at the time of heating, transfer, drop supply, and the problem that the molding accuracy is lowered due to the positional deviation of the glass material with respect to the molding surface are solved. Therefore, the yield is improved and the cost is advantageous.
JP 2001-163627 A Japanese Patent Laid-Open No. 7-10556 JP-A-8-139758 JP-A-6-340430 JP-A-8-259242 JP 2003-104741 A

  In the press molding as described above, press conditions (press load, temperature, and schedule thereof) are optimized in order to ensure the accuracy of the optical element to be obtained. However, even if continuous pressing is performed under optimized pressing conditions, if the conditions of individual glass materials are different, surface shape accuracy, appearance performance, and the like may become unstable.

  That is, even if the volume of the glass material is constant, if there are individual differences in the curvatures of the upper surface and the lower surface that are deformed by pressing, reproducibility of pressing accuracy cannot be obtained strictly. In addition, when individual glass materials are preheated and then supplied to the mold, if there is an individual difference in temperature distribution due to preheating, the press conditions are not constant.

  Furthermore, a high-precision glass optical lens is formed into a lens having a predetermined shape by using a spherical or aspherical concave or convex shape and pressing a heat-softened glass material. In principle, it is necessary to use materials that conform to the following restrictions.

(1) In the case of a concave shape die, the surface shape of the glass material that is in close contact with the concave shape die is a convex shape having a radius of curvature equal to or less than that of the concave shape die.
(2) In the case of a convex shape mold, the surface shape of the glass material in close contact with the convex shape mold is a planar shape, a convex shape, or a concave shape having a curvature radius equal to or greater than the curvature radius of the convex shape mold. To do.

  This is a restriction for preventing generation of atmospheric gas pools on the surface of the molded product during press molding. For example, when the surface shape of the glass material in close contact with the concave lower mold 20 is a convex shape having a radius of curvature equal to or greater than the curvature of the lower mold 20, as shown in FIG. A closed space S is formed between them. And since gas will remain in this closed space S, a gas mark will arise in a shaping | molding lens and it will become a molded product with a shape defect. Therefore, it is required to use a glass material such as a flat plate shape, a spherical shape, or a biconvex curved shape as appropriate according to the shape of the mold so as to satisfy the restriction.

  However, the biconvex curved glass material often does not have the same radius of curvature on the upper and lower surfaces. Also, in the optical element to be obtained, it is rare that the upper surface and the lower surface have the same shape, and the upper and lower molds usually have molding surfaces with different curvature radii. Therefore, when both the upper and lower molds are taken into consideration, the following matters are further required as restrictions on the shape of the glass material.

(3) One surface of the glass material has a radius of curvature that satisfies the restrictions of the upper mold, the other surface has a radius of curvature that satisfies the restrictions of the lower mold, and when the glass material is supplied to the lower mold, Place the glass material on the lower mold so that the orientation of the lower surface is always constant.

  In addition, in the technique of patent document 1, it is made hard to produce a gas pool by raising the surface of a glass raw material, but since the shape of the upper and lower surfaces of a glass raw material is not symmetrical, it is partially at the time of supply to a shaping | molding die. If reversal occurs, the press molding conditions will not be constant, and depending on the upper and lower mold shapes, there will be poor gas accumulation in the reversed ones.

By the way, with the technique of patent document 2, the time required for temperature rise and temperature fall can be shortened and cycle time can be shortened by not raising the temperature of a shaping | molding die unnecessarily. In the technique of Patent Document 3, the glass material is heated and softened to a viscosity of 10 ^5.5 to 10 ^9.0 poise in a floating state, and transferred to a forming die by dropping, whereby a gap between the jig and the glass is obtained. It is possible to form a gas layer to prevent the reaction between the jig and the glass, and to soften by heating while maintaining the shape of the glass material.

  As described above, when glass materials heated and softened in places other than the mold are transferred and supplied to the mold before molding, not only the cycle time can be shortened, but also the contact time between the glass material and the mold at a high temperature is shortened. Therefore, it is effective in preventing the deterioration of the mold.

  In order to place the glass material on the lower mold, a drop supply is advantageous. In particular, when the glass material in the softened state as described above is arranged in the mold, it is necessary to take care not to cause fusion or surface defects between the transfer jig and the glass material. Therefore, a supply method is advantageous in which the glass material is floated and held by a jig so as to be substantially non-contact, and dropped from the state onto the lower mold.

Under the circumstances described above, the present inventor has conducted intensive research to reduce the incidence of defective products, and found that the glass material tends to be turned upside down when dropped from the floating state. It was. That is, when a glass material is dropped and supplied, the glass material rotates in the dropping path and may be reversed when falling on the lower mold. Therefore, when the shape of the upper surface and the lower surface of the glass material is not the same, there is a possibility that the reversal of the glass material may cause variations in the press conditions or deviate from the above-mentioned restrictions and cause a gas accumulation in the molded product.
In Patent Document 6, the position of the glass material is corrected on the molding surface of the lower mold, but the upside down of the glass material cannot be corrected.

  The present invention was made by paying attention to the phenomenon that the glass material is easily reversed when it is dropped and supplied. When molding materials having different shapes on the upper and lower surfaces are dropped and supplied onto the lower mold, this molding material is used.・ Stable supply so that the top and bottom surfaces are always in a constant arrangement makes the pressing conditions constant and prevents inconvenience of gas accumulation in the molded product, resulting in a high yield of optical elements with high surface accuracy. It is an object of the present invention to provide a mold press molding apparatus and an optical element manufacturing method that can be produced well.

To achieve the above object, the mold press molding apparatus of the present invention is a mold press molding apparatus that press-molds a molding material with an upper mold and a lower mold having molding surfaces facing each other, and the molding material on the lower mold. And a guide means for controlling the posture of the molding material by the dropping path when the molding material is dropped and supplied onto the lower mold.
With this configuration, when a molding material having different top and bottom surface shapes is dropped and supplied onto the lower mold, the top and bottom surfaces are always arranged in a constant manner by controlling the posture of the molding material through the dropping path. In addition, the molding material can be stably supplied onto the lower mold.

Moreover, the mold press molding apparatus of the present invention is configured such that the guide means stops the molding material at least once in the dropping path.
If constituted in this way, not only can the posture of the molding material be corrected once in the middle of dropping, but also the substantial falling distance of the molding material can be shortened, effectively preventing reversal of the molding material. be able to.

Further, in the mold press molding apparatus of the present invention, the guide means comprises a member that opens and closes along the dropping path, and the molding material is stationary in a closed state, and the molding material is dropped again by a subsequent opening operation. It is as.
If comprised in this way, not only the molding material which falls can be received reliably by a plurality of members, but also the molding material can be dropped again without disturbing the posture by the opening operation of the plurality of members.

Moreover, the mold press molding apparatus of this invention is set as the structure by which the said guide means is provided in the position correction means which corrects the position of the said shaping | molding raw material which fell on the said lower mold | type. Furthermore, the guide means may be provided in the supply means for dropping and supplying the molding material onto the lower mold.
If comprised in this way, reduction of a number of parts and simplification of a structure can be aimed at by sharing a guide means and a position correction means or a guide means and a molding raw material supply means.
Moreover, in the molding apparatus provided with the position correcting means, it becomes possible to provide the guide means without extending the dropping distance of the molding material, so that the effect of preventing the reversal of the molding material can be enhanced.

Further, the optical element manufacturing method of the present invention uses an upper mold and a lower mold having molding surfaces facing each other, and manufactures an optical element obtained by continuously press-molding a molding material softened by heating. In the method, when the molding material is dropped on the lower mold, the attitude of the molding material is controlled by the molding material dropping path so that the attitude of the molding material dropped on the lower mold is constant. There is a way to do it.
At this time, it is preferable that the posture control is performed so that the posture of the molding material after the drop supply matches the posture of the molding material before the drop supply.

  With such a method, the molding material can be stably supplied onto the lower mold so that the upper and lower surfaces are always in a constant arrangement. As a result, it is possible to make the pressing conditions constant, prevent the inconvenience of gas accumulation in the molded product, and produce an optical element with high surface accuracy with high yield.

  Note that the optical element manufacturing method of the present invention is particularly effective when applied under the following conditions.

The molding material is dropped and supplied onto the lower mold while being heated to a temperature corresponding to a viscosity of less than 10 ⁹ poise.

  The molding material is made into a preformed glass material by dropping or flowing molten glass into a receiving mold.

  When the molding material is supplied onto the lower mold in a predetermined posture, it is supplied onto the lower die in an upside down orientation without creating a closed space with the molding surface during press molding. In such a case, a closed space is formed between the molding surface and the molding surface during press molding.

  The molding material is preformed into a biconvex curved shape, and the biconvex curved surfaces are curved surfaces having different curvatures.

The optical element to be obtained is a biconvex lens in which the curvature radii of the first surface and the second surface are RL1 and RL2, respectively, and the curvature radii of the biconvex curved surfaces of the corresponding glass materials are R1 and R2, respectively. When
RL1 ≧ R1
RL2 ≧ R2
And RL1 <R2 or RL2 <R1
Meet.

  As described above, according to the present invention, even when molding materials having different shapes of the upper and lower surfaces are dropped and supplied onto the lower mold, the upper and lower surfaces are controlled by controlling the posture of the molding material through the dropping path. It is possible to stably supply the molding material onto the lower mold so that the arrangement is always constant. As a result, it is possible to make the press conditions constant, prevent the molded product from causing gas accumulation, and produce an optical element with high surface accuracy with high yield.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Mold press molding equipment]
First, a mold press molding apparatus according to an embodiment of the present invention will be described with reference to FIGS.
1 is a cross-sectional view of a main part of a mold press molding apparatus according to an embodiment of the present invention, FIG. 2 is a plan view of a lower mold, FIG. 3A is a plan view of a molding material supply means, and FIG. ) Is a plan view of the position correcting means, FIG. 4A is a plan view of a guide member provided in the position correcting means, and FIG. 4B is an XX cross-sectional view of the guide member.

As shown in these drawings, the mold press molding apparatus has an upper mold 10 and a lower mold 20 for pressing a glass material (molding material). The upper die 10 and the lower die 20 have an upper mother die 22 and a lower mother die 22 made of an alloy material such as nickel or tungsten, and have a shape that is long in the lateral direction. Further, molding surfaces 11 and 21 made of carbide (WC) or ceramics (Si ₃ N ₄ , SiC) for transferring a predetermined shape to a glass material are provided on the opposing surfaces of the upper mold 10 and the lower mold 20. A plurality are formed.

  The upper mold 10 and the lower mold 20 are attached to an upper main shaft (not shown) and a lower main shaft (not shown) on the side opposite to each facing surface. The upper main shaft is fixed to an apparatus frame (not shown), and the lower main shaft is driven in the vertical direction by a motor (not shown). In other words, the upper mold 10 and the lower mold 20 are moved toward and away from each other by driving the lower spindle. In addition, an induction heating coil C is provided around the upper mold 10 and the lower mold 20 for high frequency induction heating of these.

  The mold press apparatus includes a molding material supply means 30 that transfers a glass material softened by heating between the upper mold 10 and the lower mold 20 and supplies the glass material to the lower mold 20 by dropping. The molding material supply means 30 includes a long support arm 31 formed of a metal having high heat resistance (for example, a stainless alloy) and a plurality of floating dishes 32 arranged in a line along the longitudinal direction. ing. The levitation plate 32 has a mortar-shaped receiving portion, and holds a glass material here. As the material of the levitating dish 32, a material in which the surface of high-density carbon is glassy carbon can be used.

  Inside the support arm 31, a gas hole 31 a for sending an inert gas from below is formed with respect to the receiving part of the floating dish 32. Due to the pressure of the gas, the glass material is transported while slightly floating in the floating tray 32. The support arm 31 and the levitation plate 32 are divided into two at the center line in the width direction, and are opened and closed in a parallel direction by an opening / closing drive means (not shown). That is, by opening the support arm 31 and the floating tray 32 at an upper position of the lower mold 20, the glass material that is floated and held by the receiving portion of the floating dish 32 is dropped and supplied onto the molding surface 21 of the lower mold 20.

The mold press apparatus is provided between the molding material supply means 30 and the lower mold 20 and includes a position correction means 40 for correcting the position of the glass material. The position correcting means 40 includes a guide arm 41 that is long in the lateral direction and a plurality of guide members 42 that are arranged in a line in the longitudinal direction. As with the molding material supply means 30, the guide arm 41 and the guide member 42 are divided into two at the center line in the width direction, and are opened and closed in parallel by an opening / closing drive means (not shown).
The guide arm 41 and the guide member 42 are preferably made of a material having high heat resistance, like the molding material supply means 30.

  The guide member 42 has a separable cylindrical shape (for example, a cylindrical shape), and an inner diameter thereof is set to be equal to or slightly larger than the outer diameter of the glass material. Immediately after the glass material is dropped and supplied onto the lower mold 20, the guide member 42 is in an open state, and then the closing operation is performed. When the guide member 42 is closed, the inner peripheral surface thereof contacts the outer periphery of the glass material, and the glass material is moved to the center position of the molding surface of the lower mold 20. Thereby, the position of the glass material is corrected, and high-precision press molding becomes possible.

  The mold press apparatus of the present invention includes guide means 50 for controlling the orientation of the glass material by its dropping path and preventing the glass material from being reversed when the glass material is dropped and supplied onto the lower mold 20. As such a guide means 50, it is preferable that the falling glass material is stopped at least once. If the drop distance is long, the probability of reversal increases, so it is preferable to temporarily stop the glass material at a short drop distance. Moreover, once the glass material that is falling is stopped, the glass material that has started to lose its posture due to irregular rotation can be returned to the posture before dropping. Therefore, it is preferable that the guide means 50 for stopping the glass material temporarily supports the glass material so that the glass material assumes a posture before dropping.

  It is preferable that the guide means 50 temporarily stops the glass material in the dropping path, then opens the dropping path by a retreat operation, and drops the glass material again. At this time, it is preferable that the guide means 50 has a plurality of members, and these are retracted at an isotropically equal speed so as not to give an irregular rotational force to the glass material. For example, a convex portion to be the guide means 50 is formed on the inner peripheral upper portion of the guide member 42 provided in the position correcting means 40, and the glass material is stopped and re-dropped using the opening / closing operation of the guide member 42. it can. In this case, with the plurality of members closed, the falling glass material is received by contact with a part thereof, and then the plurality of members are opened and retracted from the dropping route to open the dropping route. Glass material can be dropped again.

  The plurality of members constituting the guide means 50 are preferably in contact with only the peripheral portion of the glass material. For example, when the member that supports the peripheral portion of the glass material and then drops again is configured by a hollow stepped shape, the longest diameter of the hollow portion is X, the horizontal outermost diameter of the glass material is Y, When the open / close amount in the guide horizontal direction is Z, the outermost diameter in the horizontal direction of the glass material can satisfy the relationship of X <Y <X + Z. If it does in this way, the guide means 50 can make a glass raw material stand still reliably, and can make it fall again reliably.

  Here, it is preferable that the longest diameter X of the hollow portion of the guide means 50 is not excessively small in consideration of the optical effective diameter of the optical element to be obtained. That is, when the effective diameter of the optical element is D, if the diameter of the glass material in the corresponding portion is D ′, X> D ′ is preferable. If it does in this way, a surface defect will not be given to a portion which becomes in the effective diameter of an optical element.

  As for the member which comprises the guide means 50, it is preferable that the part which contacts a glass raw material at least is a shape which does not damage a glass raw material. For example, if the contact surface with the glass material is an appropriate inclined surface (for example, 30 °) or a curved surface, damage to the glass material at the time of contact can be avoided.

  Further, as shown in FIG. 5, an inert gas may be ejected from the contact surface with the glass material to float and hold the glass material. For example, when the guide means 50 is provided in the position correcting means 40, the glass material can be obtained by forming the gas holes 41 a and 42 a in the guide arm 41 and the guide member 42 and connecting them to the gas supply source of the molding material supply means 30. An inert gas can be ejected from the contact surface. In this way, the damage probability of the glass material can be further reduced.

  One guide means 50 may be provided on the dropping path to divide the falling distance into two, and when the dropping path is long, it may be provided at two places and divided into three. That is, if the N guide means 50 are provided, the glass material falling path can be divided (N + 1) in the vertical direction. For example, as shown in FIG. 6A, if the three guide means 50 are provided in the glass material dropping path, the dropping path can be divided into four. In this case, it is preferable that the guide means 50 has a larger amount of protrusion toward the lower side, and the guide means 50 is retracted at a low speed when it is dropped again. In this way, the glass material can be dropped step by step while the guide means 50 is retracted.

  The installation height of the guide means 50 can be arbitrarily set according to the distance of the fall path. For example, as shown in FIG. 6B, when the distance of the dropping path is long, the guide means 50 can be provided in the middle or lower side of the guide member 42 to shorten the dropping distance at the time of dropping again.

  Further, when the glass material has a long drop distance, as shown in FIG. 6C, the height of the guide means 50 itself may be increased so as to contact the glass material in a wide range in the height direction. . At this time, if the contact surface of the guide means 50 is set to an appropriate inclined surface (for example, 45 °) and the guide means 50 is retracted at a low speed when it is dropped again, the glass material is removed in the process of retracting the guide means 50. It can be gradually moved downward.

In order to reduce the reversal probability of the glass material, it is conceivable to reduce the fall distance itself, but this is not always easy or advantageous.
For example, when the glass material is floated and dropped, a gas supply path is provided in the molding material supply means 30 in order to transfer the glass material to the lower mold 20 in a floating state. Thickness is required. Also, the thickness of the molding material supply means 30 is necessary to suppress thermal deformation of the molding material supply means 30 itself.

  In addition, in order to obtain surface shape accuracy that precisely matches the product standard, the glass material must be precisely adjusted so that the horizontal center position of the heat-softened glass material matches the horizontal center position of the molding surface of the lower mold 20. Need to be placed. This is because when a glass material is press-molded at a biased position on the molding surface, defective shape and poor surface accuracy occur due to uneven thickness and uneven press load. Therefore, it is effective to provide the position correcting means 40 for precisely correcting the position of the molding material on the molding surface immediately after being supplied onto the molding surface. For this reason, a predetermined interval is required between the molding material supply means 30 for dropping the glass material and the lower mold 20.

  On the other hand, it is not preferable that the drop distance is further extended by providing the guide means 50 of the present invention. Therefore, it is effective to provide the guide means 50 of the present invention in the position correcting means 40. In this case, the opening / closing driving means of the guide means 50 can also serve as the opening / closing driving means of the position correcting means 40.

  For the above reason, it is also effective to provide the guide means 50 of the present invention in the molding material supply means 30. In this case, the opening / closing drive means of the guide means 50 can also be used as the opening / closing drive means of the molding material supply means 30. When the guide means 50 is provided in the molding material supply means 30, for example, as shown in FIG. can do. In this case, the glass material is dropped, stopped, and dropped again by opening the molding material supply means 30 in stages.

[Molding material]
The molding material used in the present invention can be a glass material, and optical glass having desired properties is processed into a shape such as a flat plate shape, a column shape, a spherical shape, a plano-convex shape, a plano-concave shape, or a biconvex shape. However, the present invention is particularly suitable for those in which the shapes of both surfaces (upper and lower surfaces when arranged on a plane) are asymmetric. Note that the present invention can also be applied to the case where the upper and lower surface shapes are symmetrical (for example, a spherical shape), and the following effects can be obtained. The effect of the present invention is extremely remarkable in the shape of a biconvex curved surface whose upper and lower surfaces are asymmetric, which will be described below as an example.

The glass material can be obtained by dropping or flowing molten glass into a receiving mold.
For example, a concave receiving mold having a predetermined radius of curvature is prepared, and molten glass is dropped or flown down in a state in which a floating gas is ejected from the bottom of the receiving mold, and a glass lump is formed while holding it floating. be able to. As a result, the glass material can be molded in a substantially non-contact state with the receiving mold, and a high-quality glass material having no surface defects can be obtained.

  The shape of the glass material can be determined based on the shape of the optical element to be obtained, that is, the shape of the upper and lower mold surfaces used for press molding. That is, it is preferable that when a glass material is arranged in the mold and the upper and lower molds are brought close to each other, no closed space is generated between any of the upper and lower molds and the glass material. In particular, the effect of the present invention is remarkable when the glass material and the upper and lower mold shapes have the following relationship.

  When the preformed molding material is placed in the mold and the upper and lower molds are brought close to each other so that the molding surface of the upper and lower molds is in contact with the molding material, the molding material is placed between the molding surface of the upper and lower molds and the molding material. No closed space is created in the shape, but when the molding material is turned upside down, a closed space is created between one of the molding surfaces of the upper and lower molds and the molding material.

  In the case of press molding using such a glass material, the stage of supplying individual glass materials onto the lower mold, even if the vertical orientation of the glass material is controlled in advance and placed on the tray when it is subjected to pressing When the glass material is turned upside down, gas accumulation occurs during pressing, resulting in a defective lens. Such a relationship between the upper and lower mold shapes and the molding material can be applied to all cases where the lens to be obtained is a biconvex lens, a biconcave lens, a concave meniscus lens, a convex meniscus lens, or a deformed lens.

For example, the optical element to be obtained is a biconvex lens, and the radii of curvature (or paraxial radii of curvature) of the first surface and the second surface are RL1 and RL2, respectively, and the biconvex curved surface of the glass material corresponding thereto. When the radius of curvature (or the paraxial radius of curvature when the portion corresponding to the optical axis of the optical element to be obtained is used as an axis) is R1 and R2, respectively,
RL1 ≧ R1
RL2 ≧ R2
And RL1 <R2 or RL2 <R1
Is the case.

  In the case of the biconvex lens as described above, for example, if R1 and R2 of the biconvex curved surface of the glass material are made as small as possible, the probability of occurrence of gas accumulation is reduced. However, at the time of hot forming of the glass material, the curvature of the glass lump after dropping / falling the molten glass cannot be easily controlled. In particular, the free surface on the upper surface side that is not restricted by the shape of the receiving mold is difficult to control the shape such as the radius of curvature due to the relationship between gravity and viscosity. Therefore, the fact that R1 and R2 can be increased within a range that matches the shape of the optical element to be molded increases the degree of freedom in molding the glass material, and has great advantages in mass production.

The optical element to be obtained is a biconcave lens, and the curvature radii (or paraxial curvature radii) of the first and second surfaces of the lens are RL3 and RL4, and the corresponding glass material is a biconcave surface. When the curvature (or the paraxial radius of curvature with the portion corresponding to the optical axis of the optical element to be obtained as the axis) in the case (the curvature radius in the case of a plane is ∞) is R3, R4,
RL3 ≦ R3
RL4 ≦ R4
And RL3> R4 or RL4> R3
There are cases where

Further, when the optical element to be obtained is a meniscus lens such as a convex meniscus lens or a concave meniscus lens, the concave surface side of the lens is the first surface, the concave surface side is the second surface, and the respective curvature radii are RL5, 5L6, The curvature radius (or the portion corresponding to the optical axis of the optical element to be obtained) of the both curved surfaces (which may be flat surfaces in this case, the curvature radius is ∞) of the glass material corresponding to these axes When the paraxial radius of curvature is R5 and R6,
R5 surface is concave or flat (curvature = ∞), R6 surface is convex, RL5 ≦ R5, and RL6 ≧ R6
If it is,
R5 surface and R6 surface are convex surfaces, RL6 ≧ R6, and RL6 <R5
This is the case.

Further, the optical element to be obtained is a biconcave lens, and the curvature radii (or paraxial curvature radii) of the first and second surfaces of the lens are RL7 and RL8, and both curved surfaces ( When the radius of curvature is R7, R8 in the case of a plane, the radius of curvature = ∞)
R7 surface is concave, R8 surface is convex or flat, and RL7 ≦ R7 <RL8
Is the case.

  Even if the shape of the upper and lower surfaces of the glass material is symmetric, the present invention is significant. That is, the glass material can be preheated when supplied to the mold, but the temperature distribution due to preheating may be biased. If the preheated glass material is press-molded in a certain direction (in the vertical direction), the press conditions will all be equal, but if the reverse is mixed after preheating, the temperature conditions of the press molding will vary. As a result, the lens performance after molding cannot be controlled uniformly. Therefore, it is beneficial to control the attitude of the glass material according to the present invention.

[Method for Manufacturing Optical Element]
The glass material preformed as described above can be supplied to the molding die by being transferred and dropped onto the lower die by a floating jig (molding material supply means) or the like.
The temperature of the glass material when dropped on the lower mold is preferably a temperature at which the viscosity is 10 ⁹ poise or less. More ^preferably in the range of 10 5.5 ^{to 10 9.0} poise. On the other hand, the mold temperature comprising the upper and lower molds is preferably in the temperature range where the viscosity of the glass material is 10 ⁸ poise or more. The temperature when the glass material is dropped may be equal to the mold temperature, and may be further heated after the glass material is supplied into the mold, but more preferably, a glass material that is hotter than the mold is molded. Supply to the mold and start press molding immediately. The mold temperature is more preferably in the range of 10 ⁹ to 10 ¹² poise. By selecting such a temperature range, molding in a short cycle time is possible, and sufficient surface accuracy of the optical element can be ensured. The upper and lower mold temperatures may be the same or different. It can be determined according to the lens shape to be press-molded and the material.

  Prior to press molding, the glass material is heated outside the mold to a desired temperature by a known heating device. Preferably, the glass material is placed in a heating furnace for a predetermined time in a state where it is levitated with an inert gas, and is heated. Thereafter, the glass material can be dropped and supplied onto the lower mold by being transferred to the lower mold while being placed on the floating jig and dividing the floating jig.

  In the present invention, the glass material is supplied by dropping from above onto the molding surface of the lower mold, and the attitude of the glass material is controlled along the dropping path so that the attitude of the glass material is not reversed by the fall. That is, the posture of the glass material dropped on the lower mold is set to be the same as the posture before dropping. Preferably, the falling glass material is stopped at least once during the dropping. As a result, even if the glass material rotates in an indefinite direction during the fall, it can be corrected to the same posture as before the fall when stationary. Then, after the stationary, the molding material is dropped again.

The glass material dropped and supplied onto the lower mold is pressed by the approach of the upper mold and the lower mold, and formed into a desired optical element shape. Cooling is started at an arbitrary time after the start of press molding, and when the glass viscosity becomes 10 ¹² poise or less, the upper and lower molds are separated and released. Preferably, the mold release temperature is when the viscosity is 10 ¹³ to 10 ¹⁴ poise.

  Next, the embodiment of the present invention will be specifically described using examples. The following are merely examples of the present invention and do not limit the technical scope of the present invention.

[Example]
The optical element was molded by the procedure shown in FIGS. 8 and 9 using the mold press molding apparatus shown in FIGS. Specifically, barium borosilicate glass (transition point 514 ° C., yield point 545 ° C.) was press-molded to form a biconvex bispherical lens having an outer diameter of 25 mm. The curvature radius of the lower mold surface was 20 mm, and the curvature radius of the upper mold surface was 40 mm.

  On the other hand, four biconvex curved glass materials (outer diameter is 19 mm, upper surface side radius of curvature is about 30 mm, lower surface side radius of curvature is about 15 mm) are hot-formed by dropping from a molten state onto a receiving mold. Prepared. The glass material once solidified is supplied and arranged on a floating tray 32 on a support arm 31 that can be opened and closed, and is floated by an air current ejected from below each floating tray 32 in a heating furnace (not shown). And heated. At this time, the glass material was floated and softened by heating so that the upper surface side (the one to be pressed by the upper mold forming surface) of the glass material was the upper portion. At this time, the lower mother die, the support arm 31, and the guide arm 41 are moved to the origin position (S100).

After heating the molding material to a predetermined temperature (glass viscosity, equivalent to 10 ⁷ poise), the support arm 31 is inserted between the upper and lower molds, and four glass materials are placed on the upper parts of the four lower molds 20. (S102 in FIG. 8). At substantially the same time, the guide arm 41 was inserted between the support arm 31 and the lower mold 20 so as to be approximately 2 mm below the support arm 31 (S101 in FIG. 8). After raising the lower mold 20 to below the guide arm 41 (S103 in FIG. 8, (A) in FIG. 9), the guide arm 41 is closed while the support arm 31 is quickly opened, so that a plurality of levitation The plate 32 was divided into left and right, and a plurality of glass materials were dropped from the floating plate 32 (S104 in FIG. 8, (B) in FIG. 9). Each glass material came into contact with the guide means 50 provided on the guide member 42 of the guide arm 41 and temporarily stopped here.

  Thereafter (with a delay of 1 second), the ejection of the levitation gas was stopped (S105 in FIG. 8), and the guide arm 41 was opened by 4 mm, thereby widening the abutting surface interval of the plurality of guide members 42 by 4 mm (S106 in FIG. 8). (C) of FIG. By this operation, the glass material was supplied onto the lower mold 20 ((D) of FIG. 9). Next (immediately), the position of the glass material supplied onto the lower mold 20 was corrected by closing the guide arm 41 (S107 in FIG. 8, (E) in FIG. 9). Thereafter, the support arm 31 and the guide arm 41 were immediately retracted from above the lower mold 20 (S108 to S113 in FIG. 8), and then the lower mother mold was raised and pressed (S114 in FIG. 8). It was cooled to below the transition point, released from the mold, and the molded glass lens was taken out.

  The above operation was repeated 182 times for each mold. That is, a total of 728 pieces were processed. As a result, when the glass material is supplied to the lower mold 20, the glass material is never supplied so that the upper surface of the glass material is downward, and as a result, a gas pool is generated in the glass optical lens. There was nothing at all. The defect rate due to the occurrence of gas accumulation through the processing of a total of 728 pieces was 0%.

Note that the guide arm 41 is opened and closed in two stages, the glass material is supported by the guide means 50 in the closed state, the glass material dropping path is opened in the open state, and further, the glass arm is closed. The glass material was corrected in the horizontal center position of the lower mold 20. For this reason, it is preferable to appropriately select the inner diameter of each part of the guide member 42 in the open, closed, and each state. Furthermore, it is possible to open and close the guide arm 41 in multiple stages. In this case, the position correction surface and the inner diameter of the guide means 50 may be the same. The guide member 42 is preferably preheated to a temperature corresponding to 10 ⁷ to 10 ⁹ poise before insertion.

[Comparative example]
A glass lens having the same shape was molded using the same apparatus as in the above example. The same glass material was also used. However, instead of the guide member shown in FIG. 4, a guide member 60 without guide means 50 as shown in FIG. 10 was used, and molding was performed according to the procedure shown in FIG. That is, the guide arm 41 was inserted between the support arm 31 and the lower mold 20 so as to be about 2 mm below the support arm 31 ((A) of FIG. 11). Thereafter, in a state where the guide arm 41 is open, the support arm 31 is quickly opened ((B) in FIG. 11), so that the plurality of floating dishes 32 are divided into left and right, and the plurality of glass materials are respectively separated from the floating dishes 32. Was supplied onto the lower mold 20 corresponding to ((C) of FIG. 11). Next, the position of the glass material supplied onto the lower mold 20 was corrected by closing the guide arm 41 ((D) of FIG. 11). Thereafter, the support arm 31 and the guide arm 41 were immediately retracted from above the lower mold 20, and then the lower mold 20 was raised and pressed.

  The above operation was repeated 154 times for each mold. That is, a total of 616 pieces were processed. As a result, when the glass material is supplied to the lower mold 20, it is generated that 336 pieces are supplied so that the upper surface of the glass material is downward, and as a result, a gas pool is generated in the glass optical lens. 336 were also generated. The defective rate due to the occurrence of gas accumulation through the processing of a total of 616 pieces was 54.5%.

  The present invention is applied to a precision mold press molding technique that press-molds a molding material such as a glass material by using a molding die that is precisely processed based on the shape of an optical element to be obtained. In particular, it is effective when dropping and supplying molding materials with different top and bottom shapes onto the lower mold, and by pressing the molding material stably so that the top and bottom surfaces are always in a constant arrangement, While keeping the conditions constant, it is possible to prevent inconvenience of gas accumulation in the molded product, and to produce an optical element with high surface accuracy with a high yield.

It is principal part sectional drawing of the mold press molding apparatus which concerns on embodiment of this invention. It is a top view of a lower mold. (A) is a plan view of the molding material supply means, and (B) is a plan view of the position correction means. (A) is a top view of the guide member provided in a position correction means, (B) is XX sectional drawing of a guide member. (A) And (B) is principal part sectional drawing which shows the other example of a guide means. (A)-(C) are principal part sectional drawings which show the other examples of a guide means. It is principal part sectional drawing which shows the other example of a guide means. It is a flowchart which shows the operation | movement procedure at the time of the press molding by the mold press molding apparatus of this invention. (A)-(E) are explanatory drawings which show the operation | movement procedure at the time of the press molding by the mold press molding apparatus of this invention. (A) is a top view of the guide member used by the comparative example, (B) is XX sectional drawing of a guide member. It is explanatory drawing which shows the operation | movement procedure of a comparative example. It is explanatory drawing which shows the generation | occurrence | production principle of a gas pool.

Explanation of symbols

10 Upper mold 11 Molding surface 20 Lower mold 21 Molding surface 22 Lower master mold 30 Molding material supply means 31 Support arm 31a Gas hole 32 Floating dish 40 Position correcting means 41 Guide arm 41a Gas hole 42 Guide member 50 Guide means 60 Guide member C Induction heating coil

Claims (12)

In a mold press molding apparatus that press-molds a molding material by an upper mold and a lower mold having molding surfaces facing each other,
Molding material supply means for dropping the molding material onto the lower mold;
A mold press molding apparatus comprising: guide means for controlling a posture of the molding material by a dropping path when the molding material is dropped and supplied onto the lower mold.   The mold press molding apparatus according to claim 1, wherein the guide means stops the molding material at least once in the dropping path.   The said guide means consists of a member which opens and closes in the said fall path | route, makes the said molding raw material stand still in a closed state, and makes the said molding raw material fall again by the subsequent opening operation | movement. Mold press molding equipment.   The mold press molding apparatus according to claim 1, wherein the guide unit is provided in a position correction unit that corrects a position of the molding material dropped on the lower mold.   The mold press molding apparatus according to any one of claims 1 to 3, wherein the guide unit is provided in the supply unit that drops and supplies the molding material onto the lower mold. In the method of manufacturing an optical element obtained by continuously press-molding a molding material in a softened state by heating, using an upper mold and a lower mold having molding surfaces facing each other,
When the molding material is dropped and supplied onto the lower mold, the posture control of the molding material is performed along the dropping path of the molding material so that the attitude of the molding material dropped onto the lower mold is constant. A method for manufacturing an optical element.   The method of manufacturing an optical element according to claim 6, wherein the posture control is performed so that the posture of the molding material after dropping supply matches the posture of the molding material before dropping supply. The method for manufacturing an optical element according to claim 6 or 7, wherein the molding material is dropped and supplied onto the lower mold in a state where the molding material is heated to a temperature corresponding to a viscosity of less than 10 ⁹ poise.   The method for manufacturing an optical element according to any one of claims 6 to 8, wherein the molding material is a glass material preformed by dropping or flowing molten glass into a receiving mold.   When the molding material is supplied onto the lower mold in a predetermined posture, a closed space is not formed between the molding surface and the molding surface at the time of press molding, and is supplied onto the lower die in an upside down posture. 10. The method of manufacturing an optical element according to claim 6, wherein a closed space is formed between the molding surface and the molding surface during press molding.   11. The molding material according to claim 6, wherein the molding material is preformed into a biconvex curved shape, and the biconvex curved surfaces are curved surfaces having different curvatures. A method for manufacturing an optical element. The optical element to be obtained is a biconvex lens in which the curvature radii of the first surface and the second surface are RL1 and RL2, respectively, and the curvature radii of the biconvex curved surfaces of the corresponding glass materials are R1 and R2, respectively. When
RL1 ≧ R1
RL2 ≧ R2
And RL1 <R2 or RL2 <R1
The method for manufacturing an optical element according to claim 6, wherein:

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