JP2004203740A - Production method of glass optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an effective production method of a glass optical element. <P>SOLUTION: The production method of the glass optical element is composed of a feeding step wherein a glass raw material to be molded is dropped from the top on a molding surface of a lower mold of a mold consisting of an upper mold and the lower mold. The glass raw material to be molded melted by heating, is transported on the molding surface of the lower mold. The glass raw material to be molded is dropped on the molding surface of the lower mold, by putting a guide means having a through-hole, between a position for transporting the glass raw material to be molded and the lower mold, wherein a dropping path of the glass raw material to be molded is formed before or after transporting said above, or simultaneously as transporting. Instantly after being dropped, the glass raw material to be molded is press-molded by moving the guide means back from the top of the lower mold. Also, the glass raw material having a viscosity of 10<SP>5.5</SP>-10<SP>8</SP>poise is press-molded with the mold having a temperature where this glass raw material to be molded shows the viscosity of 10<SP>8</SP>-10<SP>10.5</SP>poise (wherein, the temperature of the glass raw material to be molded is higher than the temperature of the mold). <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a method for supplying a glass material to be formed into a mold and an apparatus for use in the method. Further, the present invention relates to a method for producing a glass optical element including a glass optical element such as a high-precision lens, which does not require grinding or polishing after press molding, using the method of the present invention. In particular, the present invention relates to a method for manufacturing a glass optical element having higher surface accuracy with high production efficiency.

  In recent years, there have been various molding methods for glass optical elements such as high-precision lenses, which do not require softening glass and do not require grinding or polishing after press molding, using a mold that has been precision-machined from a mold material capable of mirror finishing. Has been developed. In order to obtain a required lens by press molding, it is necessary to satisfy specifications such as wall thickness, outer diameter, and eccentricity, as well as surface shape accuracy and surface quality (smooth surface roughness). Of course, the internal quality such as the refractive index and the transmittance is good.

  Furthermore, in putting such a glass optical element molding method into practical use, it is a major problem how much productivity can be obtained. In other words, it is a major problem to be able to produce more glass optical elements in a shorter time. One of the means for improving the productivity is to process a plurality of glass materials in parallel, and the other is to reduce the time for one processing. Various improvements have been proposed for each. In order to shorten one processing time, it is necessary to further shorten the cycle of heating and cooling the molding die. For this reason, among the molding conditions, various conditions have been devised for the temperature of the glass material and the temperature of the molding die during molding.

For example, Japanese Unexamined Patent Publication No. 7-10556 (Patent Document 1) discloses that a glass material having a viscosity in the range of 10 ⁷ to 10 ⁹ poise is molded into a mold having a temperature at which the glass material exhibits a viscosity of 10 ¹⁰ to 10 ¹² poise. And a method of pressure molding. Japanese Patent Application Laid-Open No. Hei 9-12317 (Patent Document 2) discloses a glass material having a viscosity in the range of 10 ^5.5 to 10 ⁹ poise and a glass mold having a temperature at which the glass material exhibits a viscosity of 10 ⁸ to 10 ¹² poise. However, there is described a method of performing pressure molding using a mold at a temperature lower than the temperature of the glass material. In each method, the temperature of the mold is not unnecessarily increased, thereby shortening the time required for raising and lowering the temperature and shortening the cycle time.

  As described above, a method of molding a glass optical element such as a high-precision lens using a molding die precisely processed from a mold material that can be mirror-finished without melting the softened glass has attracted attention in recent years and has been variously developed. I have. Further, in any of the methods, in order to prevent deterioration of the molding surface of the molding die, the glass material heated and softened at a place other than the molding die is transferred to the molding die before molding and molded. For example, the glass material to be molded is usually in the form of a spherical or marble-shaped (flattened spherical) preform, which is transferred by a floating plate, a suction pad, or the like, above the lower mold of the mold, and then dropped to form the glass. Supplied to the mold.

For example, Japanese Unexamined Patent Publication No. 6-340430 (Patent Document 3) discloses that a molten glass is conveyed by a floating plate formed of a split mold that can be opened and closed in a horizontal direction, which ejects gas from the surface of a porous member, and forms the glass. A method is disclosed in which a split mold is opened on a mold and glass is supplied to the mold. Japanese Patent Application Laid-Open No. 8-133758 (Patent Document 4) discloses that a glass preform has an opening diameter smaller than, equal to, or larger than the diameter of the glass preform, and supplies an airflow to the bottom thereof. Using a floating jig provided with one pore, heat-softens while floating by airflow from the pore, or a porous floating jig having a spherical surface or a plane approximating the curvature of the outer diameter of the glass press. A method is disclosed in which the glass preform is softened by heating while being floated by an airflow from a porous material, and the heated and softened glass preform is supplied to a molding die. Japanese Patent Application Laid-Open No. 8-259242 (Patent Document 5) discloses that a glass preform is blown out from a plurality of small holes near the center using a floating jig having a trumpet-shaped upper opening. A method is disclosed in which a glass preform that is heated and softened while being rotated and floated by an air current is supplied to a mold by dropping the heated and softened glass preform.
JP-A-7-10556 JP-A-9-12317 JP-A-6-340430 JP-A-8-133758 JP-A-8-259242

  However, when the glass material to be molded is naturally dropped and supplied to the molding die (lower mold) as in the above method, there are the following problems depending on the shape and size (weight) of the glass material to be molded. Was. For example, a relatively small glass material to be molded may not fall onto the molding surface of the lower mold but may jump out of the molding mold due to the state of airflow during the fall or contact with a floating plate or the like. . Alternatively, in the case of a non-spherical glass material to be molded, even if it falls on the lower mold, its position may be shifted from the center of the molding surface, and when molding is performed in such a state, the molding material is uniformly distributed in the mold. In some cases, uneven wall thickness occurs, and the molding material protrudes from the mold, resulting in defective products. In particular, the glass preform that is floating due to the air current is rotating or vibrating slightly up, down, left and right, so when dropping such a glass preform, the glass preform at the start of the fall is In an unstable state. Therefore, in such a case, the above problem is likely to occur.

  Therefore, an object of the present invention is to provide a method and an apparatus capable of preventing a glass material to be molded from falling out of the molding die during dropping and supplying the glass material to a molding die by dropping the glass material. Still another object of the present invention is to provide a method and an apparatus capable of positioning a glass material to be formed substantially at the center of a molding surface of a lower mold when supplying the glass material to the forming die by dropping the glass material to be formed. It is in. Another object of the present invention is to provide a method of manufacturing a glass optical element in which a glass material to be formed is prevented from jumping out of a mold and the occurrence of defective products using the above method.

  The present invention is a method of supplying a glass material to be molded by dropping it from above onto a molding surface of a lower mold of a molding die comprising an upper mold and a lower mold, and a guide means for dropping the glass material to be molded. And the guide means is provided at a position where the glass material to be molded falls on the molding surface of the lower mold (hereinafter, referred to as "supply method 1"). I do.

  Further, the present invention is a method for supplying a glass material to be molded onto a molding surface of a lower mold of a molding die composed of an upper mold and a lower mold, after supplying the glass material to be molded onto the molding surface of the lower mold. A method of supplying a glass material to be molded, wherein the position of the glass material to be molded is corrected so that the vertical center of the glass material to be molded substantially coincides with the center point of the molding surface of the lower mold. (Hereinafter referred to as “supply method 2”).

  Further, the present invention is a guide means used in a method of supplying a glass material to be molded by dropping from above onto a molding surface of a lower mold of a molding die comprising an upper mold and a lower mold, wherein A guide means is provided, which has a guide portion that forms a material passage and that allows a glass material to be formed to fall.

  Further, the present invention is a means used in a method for correcting the position of a glass material to be supplied on a molding surface of a lower mold of a molding die including an upper mold and a lower mold, It has a molded glass material abutting portion for abutting and moving, and the molded glass material abutting portion has an opening end surface having a ring shape or having a projection arranged on a concentric circle. Characteristic position correcting means is provided.

  Further, the present invention provides a glass optical element wherein the glass material to be molded supplied onto the molding surface of the lower mold is pressure-formed by using the method 1 or 2 for supplying the glass material to be molded according to the present invention. And a method for producing the same.

  Advantageous Effects of Invention According to the present invention, it is possible to provide a method and an apparatus which can prevent a glass material to be formed from falling out of the molding die during dropping and supplying the glass material to a forming die by dropping the glass material. Further, according to the present invention, there is provided a method and an apparatus capable of positioning a glass material to be formed substantially at the center of a molding surface of a lower mold when supplying the glass material to be formed by dropping the glass material to be formed. Can be. By using the method and the apparatus for supplying an optical element molding material of the present invention, an optical element having good quality can be stably produced.

(Supply method 1)
The supply method 1 of the present invention is a method in which a glass material to be formed is supplied by being dropped from above, preferably naturally, onto a molding surface of a lower mold of an upper mold and a lower mold. There is no particular limitation on the type, shape, material, etc. of the mold to which the glass material is supplied. There is no limitation on the material and shape of the glass material to be formed, and the shape may be, for example, a spherical shape or a marble shape. The glass material to be molded can be, for example, a glass preform or a glass gob, and may be in a state of being softened by heating or in a state of not being heated. However, since the supply of the molded glass material onto the molding surface of the lower mold by dropping is effective in a heated and softened state, the supply method of the present invention is also particularly effective in the case of a heated and softened molded glass material. It is. Dropping from above the molded glass material, for example, by placing or moving the suction pad that has absorbed the molded glass material above the lower mold, and then releasing the suction, or due to the airflow that ejects the molded glass material This can be done by placing or moving the held splittable floating plate above the lower mold, and then splitting the floating plate.

  In the method of the present invention, the glass material to be molded is dropped, and the glass material to be molded is preferably dropped substantially vertically. In the method of the present invention, guide means for dropping the glass material to be formed substantially vertically is used, and the guide means is provided at a position where the glass material to be formed falls on the molding surface of the lower mold. Specifically, the guide means may have a guide portion that forms a falling path for the glass material to be formed and allows the glass material to be dropped substantially vertically. The guide portion of the guide means, which forms the falling path of the glass material to be molded, may have any structure and shape as long as it can guide the glass material to be molded onto the molding surface of the lower mold. For example, it may be plate-shaped (see FIGS. 1 and 2) provided with a through hole, tubular (see FIG. 3), funnel-shaped (see FIG. 4), ring-shaped with legs (see FIG. 5), and the like. The guide means will be described later in detail.

The guide means is interposed between the lower position and the transfer position of the glass material before or after the glass material is transferred above the lower mold, or simultaneously with the transfer. The guide means is preferably arranged close to the lower mold from the viewpoint that the glass material to be molded can be effectively prevented from jumping out of the mold. Further, it is preferable to use the guide means while heating it in order to maintain the temperature of the glass material to be molded. In particular, when the glass material to be molded is heated and softened to about 10 ^5.5 to 10 ⁸ poise, the glass material to be molded is heated to a temperature at which a so-called chill mark is not formed on the glass surface by contact with the guide means. For example, the temperature is preferably higher than the temperature of (glass transition point -200 ° C.) of the glass material to be formed. Further, from the viewpoint of preventing fusion between the guide means and the glass material to be molded, for example, around the glass transition point of the glass material to be molded (glass transition point ± 100 ° C., more preferably ± 50 ° C.), or Preferably it is less than that.

(Guiding means)
The guide means of the present invention has a guide portion which forms a falling passage for the glass material to be molded and allows the glass material to be molded to fall substantially vertically. The guide means also has means for moving the guide portion. The falling path of the glass material to be molded preferably has an inner diameter slightly larger than the diameter of the glass material to be molded. A passage whose inner diameter decreases downward and whose minimum inner diameter is slightly larger than the diameter of the glass material to be molded is more preferable. The shape of the guide means is not limited as long as the guide means has a passage for the glass material to be formed and has a guide portion capable of regulating the falling position of the glass material to be formed in the horizontal direction. The guide portion may be, for example, a thick plate body provided with a through hole (see FIG. 1). The through-hole preferably has a funnel shape that at least partially narrows downward (FIG. 2). Further, the guide portion may be a substantially cylindrical member (see FIG. 3). Furthermore, the guide portion may be a funnel-shaped member that at least partially narrows downward (see FIG. 4). Further, the guide portion may be formed by projecting three or more leg members on the ring. Preferably, each leg member is inclined toward the center of the ring from the base to the tip (see FIG. 5).

  As shown in FIG. 6, a plurality of upper dies (not shown) and a plurality of lower dies 3 are assembled to an upper mother die (not shown) and a lower mother die 2, respectively. In the case of molding a molded product, the guide portion 1 has a shape substantially following the upper surface shape of the mother die, and a plurality of through holes are located at a lower die assembling position. (See FIG. 6). Also in this case, it is preferable that at least a part of the through hole has a funnel shape that narrows downward (see FIG. 7). The material of the guide means is not particularly limited as long as it is a heat-resistant material. For example, it can be a metal, ceramic, or carbon material. The falling path of the glass material to be molded of the guide means may be subjected to a surface treatment in order to allow the glass material to be molded to slide. In order to guide the glass material to be molded more smoothly and to prevent the glass material to be molded from being scratched, it is preferable that the corners present in each of the above shapes are curved.

  In the present invention, the guide means applies the drag including the vector component toward the position (center of the molding die) to be landed at a predetermined timing in the process of dropping the glass material to be molded, thereby bringing the glass material to the desired position. It is to land. Therefore, the position of the guide means used in the present invention is also important in order to make such correction at a predetermined timing. For example, the operation of the guide means of the present invention is as follows. When the glass material to be molded is a material that has floated by an air current before falling, the glass material to be molded often makes a rotational motion and a vibrational motion. At this time, when the molded glass material is released from the floating due to the gas in order to drop, the molded glass material is subjected to the inertial force based on the rotational motion and the vibrational motion, and is shifted in a horizontal direction from the opened position. You will land at the location. Moreover, since the direction of action of the kinetic energy of the glass material to be formed changes regularly or irregularly, the magnitude of the shift and the direction of the shift differ depending on the state when the glass material is opened. However, when the guide means is used, a drag having a horizontal vector component toward a position to be landed (the center of the molding die) is given to the horizontal inertial force which is the cause of the displacement, so The position can be adjusted. Here, the timing at which the drag is applied can be selected by selecting the height and shape of the guide unit. That is, by providing the guide means at a relatively high position, the drag can be applied to the glass material to be formed at a relatively early stage during the fall. In addition, by providing the guide means at a relatively low position, the above-described drag can be applied to the glass material to be formed at a stage relatively near the end during the fall.

  At this time, the provision of a plurality of guide means and the use of the guide means having a large vertical direction make the glass material to be formed come into contact with the guide means (that is, the glass material to be formed receives the drag from the guide means). Work in a direction to increase timing. For example, the timing at which the guide means gives the drag to the glass material to be molded tends to be greater in the guide means of FIG. 3 than in the guide means of FIG. Further, the shape and material of the guide means affect the direction of the drag and the magnitude of the drag. At this time, increasing the vertical size of the guide means can increase the range of the height at which the drag is applied.

(Supply method 2)
The supply method 2 of the present invention is a method of supplying a glass material to be formed on a molding surface of a lower mold of an upper mold and a lower mold. It is almost the same. However, this method is particularly effective when the shape of the glass material to be formed is a substantially spherical shape other than a true sphere. Even if the true spherical glass material is not supplied to the center of the molding surface, it may rotate and move naturally to the center of the molding surface depending on the state of the glass. On the other hand, in the case of a spherical shape other than a true sphere, for example, a flat spherical shape such as a marble shape, if not supplied to the center of the molding surface, it will rotate and move naturally to the center of the molding surface. Because it is difficult. The glass material to be formed can be supplied to the lower mold by a known method such as dropping from a suction pad, a floating dish, or the like, and is preferably performed by the supply method 1 of the present invention.

  In the supply method 2 of the present invention, after supplying the glass material to be molded onto the molding surface of the lower mold, the position of the glass material to be molded is adjusted to the center in the vertical direction of the glass material to be molded and the center of the molding surface of the lower mold. Is modified to substantially match. This prevents uneven thickness because the glass material to be formed spreads evenly in the mold, thereby preventing the glass material to be formed from sticking out of the mold and causing defective products. The correction of the position of the molded glass material is performed, for example, using a position correcting means having a molded glass material contact portion having a ring-shaped molded glass material contact portion or a projection portion arranged on a concentric circle. Can be done. The structure and the like of the position correcting means will be described later in detail.

  The correction of the position is performed such that the vertical center of the molded glass material abutting portion is aligned with the center point of the molding surface of the lower mold, and the molded glass material abutting portion is brought into contact with the molded glass material. This can be done by descending vertically. That is, after supplying the glass material to be molded onto the molding surface of the lower mold, the position correcting means is arranged above the lower mold so that the center of the glass material contacting portion coincides with the center point of the molding surface of the lower mold. Or move. Next, the position can be corrected by lowering the position correcting means so that the position correcting means is brought into contact with the vicinity of the uneven thickness portion of the glass material to be molded, and further lowering the position correcting means while making contact. The position correcting means may be, for example, a means having a ring 4 having a diameter slightly larger than the diameter of the glass material to be formed as shown in FIG. In this case, the position can be corrected as follows. The ring 4 is arranged such that its center coincides with the center 6b of the molding surface 6a of the lower die 6 (see FIG. 8A). Next, the ring 4 is lowered vertically to make contact with the glass material 5 to be molded (see FIG. 8B). Further, by lowering while pressing the curved surface of the glass material 5 to be molded by the ring 4, the center 5a of the glass material 5 to be molded can be moved so as to approach the center 6b of the molding surface 6a (see FIG. 8C).

  The contact member of the position correcting means with the glass material to be formed is, in addition to the ring shape as described above, for example, a glass material to be formed such as a glass material contact portion having projections arranged on concentric circles. Any shape may be used as long as it can be brought into contact with the lower die at a position concentric with the lower die. The structure of the position correcting means will be described in detail below. Further, it is preferable to use the position correcting means while heating it in order to maintain the temperature of the glass material to be formed. The heating temperature of the position correcting means is not limited, but may be, for example, lower than the glass transition point of the glass material to be molded.

(Position correction means)
The position correcting means may be of any shape as long as it comes into contact with the glass material to be formed at a position on a concentric circle with the lower mold, and has, for example, a ring or a projection arranged on a concentric circle. It may have a glass material abutting portion to be formed. Also, the position correcting means can be arranged on the lower mold by a suitable lifting means and reciprocating means.

  The position correcting means may be, for example, a ring 4 having an inner diameter smaller than or substantially equal to the diameter of the glass material to be formed (see FIG. 9A). The cross-sectional shape of the ring may be rectangular, but it is preferable that the contact portion with the glass material to be molded is tapered (see FIG. 9B) or circular (see FIG. 9C). In this case, as described above, the ring 4 is arranged so that the center thereof coincides with the horizontal center of the lower die 6 (see FIG. 8A), and is then lowered vertically to contact the glass material 5 to be molded. Then, by lowering while pressing the curved surface of the glass material to be molded, the position of the glass material to be molded can be corrected (see FIG. 8C). As long as the position correcting means of any shape exemplified below is in contact with the glass material to be formed and the lower mold at a position of a concentric circle, the position can be corrected by basically the same method.

  The position correcting means may be, for example, a cylinder whose inner diameter is larger than or equal to the diameter of the glass material to be formed. The position correcting means may have a cylindrical shape whose inner diameter increases toward the lower end and at least one portion of the inner diameter is the same as the diameter of the glass material to be molded. In this case, even if the diameter of the glass material to be corrected whose position is to be corrected fluctuates somewhat, it can be dealt with. That is, as shown in FIG. 10, when the diameter is substantially equal to the diameter of the glass material to be molded, the position is corrected in a lower portion of the cylinder 7, and as shown in FIG. Is small, the position is corrected in the upper part of the cylinder.

  The position correcting means may be formed by forming a bowl-shaped depression or a frustum-shaped depression whose diameter becomes narrower upward on the lower surface of the thick plate (see FIGS. 12 and 13). The position correcting means may be a member formed by projecting three or more leg members concentrically on a ring, a plate, or the like. Preferably, each leg member extends from the base to the tip (see FIG. 14). In the case where the molding die is formed by assembling a plurality of upper dies and lower dies with each of the upper mother die and the lower mother die, the position correcting means may include a cross section substantially following the cross sectional shape of the mother die. It may have a shape, and a plurality of through holes, bowl-shaped depressions or truncated cone-shaped depressions may be formed at the lower die assembly position so that all the depressions are concentric with the lower die at the time of setting ( See FIG. 15).

  In addition, when the molding die is one in which a plurality of upper dies and lower dies are assembled to each of the upper mother dies and the lower mother dies, the position correcting means includes a plurality of rings at the lower die assembling positions. At the time of setting, all the rings may be connected so as to be concentric with the lower mold (see FIG. 16). The member of the position correcting means is not particularly limited as long as the member has a certain heat resistance. For example, it can be a metal, ceramic, or carbon-based material. The portion of the position correcting means which comes into contact with the glass material to be molded is preferably subjected to a surface treatment so as to allow the glass material to be molded to slide. Further, in order to prevent the glass material to be formed from being scratched or the like, it is preferable that the corners present in the above shapes are curved.

Further, it is preferable to use the position correcting means while heating it in order to maintain the temperature of the glass material to be formed. In particular, when the glass material to be molded is heated and softened to about 10 ^5.5 to 10 ⁸ poise, the glass material to be molded is heated to a temperature at which a so-called chill mark is not formed on the glass surface by contact with the position correcting means. For example, the temperature is preferably higher than the temperature of (glass transition point -200 ° C.) of the glass material to be molded. Furthermore, from the viewpoint of preventing fusion between the position correcting means and the glass material to be molded, for example, around the glass transition point of the glass material to be molded (glass transition point ± 100 ° C., more preferably ± 50 ° C.) Alternatively, it is preferably less than that.

  The supply methods 1 and 2 of the present invention, and the guide means and the position correcting means are, for example, described in JP-A-6-340430, JP-A-8-133758, and JP-A-8-259242. The present invention can be applied to any method for supplying a softened glass preform to a mold.

(Method of manufacturing glass optical element)
The method for manufacturing a glass optical element according to the present invention includes the glass material to be molded supplied onto the molding surface of the lower mold by the supply method 1 according to the present invention, or the glass to be molded whose position has been corrected by the supply method 2 according to the present invention. The method is characterized in that a raw material or a glass material to be formed which is supplied onto a molding surface of a lower mold by the supply method 1 of the present invention and whose position is corrected by the supply method 2 of the present invention is pressure-formed. There is no particular limitation on the method of press-molding the glass material to be molded or the method of preheating the glass material to be molded.

For example, a method of pressure molding the glass molding material, the temperature molding of indicating the viscosity of this the glass molding material 10 ⁸ to 10 ^10.5 poises of the glass molding material having a viscosity in the range of ^105.5 to ¹⁰⁸ poises A step of initial pressurizing with a mold (however, the temperature of the glass material to be molded is higher than the temperature of the mold), and lowering the temperature of the mold and the molded glass (hereinafter referred to as molded glass) below the transition point of the glass. And removing the molded glass from the mold.

In this method, the glass material is softened by heating to a temperature corresponding to a viscosity of the glass material in the range of 10 ^5.5 to 10 ⁸ poise. When the viscosity of the glass material is 10 ⁸ poise or less, the glass material can be sufficiently deformed and molded by a mold preheated to a temperature corresponding to a viscosity of 10 ⁸ to 10 ^10.5 poise. Further, when the viscosity of the glass material is 10 ^5.5 poise or more, it is possible to prevent the glass material from being largely deformed by its own weight before molding. In order to stably perform good molding by setting the temperature of the molding die to a relatively low temperature, it is appropriate to heat the glass material preferably to a temperature corresponding to 10 ^6.5 to ^107.6 poise. The preheating temperature of the molding die is a temperature at which the viscosity of the glass material corresponds to 10 ⁸ to 10 ^10.5 poise. If the viscosity is lower than the temperature corresponding to 10 ^10.5 poise, it becomes difficult to greatly expand the glass material to obtain a glass molded body having a small edge thickness, and it is difficult to obtain high surface accuracy, and the viscosity corresponds to 10 ⁸ poise. At a temperature higher than the temperature, the cycle time of molding becomes longer than necessary, and the life of the mold becomes shorter. The temperature of the preheating of the mold is preferably a temperature at which the viscosity of the glass material corresponds to 10 ⁸ to ^109.6 poise. The temperature of the mold is set lower than the temperature of the glass material to be molded. By doing so, the cycle time can be reduced, and the life of the mold can be extended.

  Further, it is particularly preferable to set the upper mold temperature lower than the lower mold temperature at the start of the initial pressure molding, from the viewpoint of preventing the molded article from sticking to the upper mold at the time of mold release. More specifically, it is appropriate to lower the upper mold temperature by 5 to 20 ° C. lower than the lower mold temperature.

As the mold used in the present invention, a conventionally known mold can be used as it is. However, it is preferable to use a mold whose molding surface is made of an amorphous and / or crystalline carbon film made of a single component layer or a mixed layer of graphite and / or diamond. In a mold having a molding surface made of a carbon film as described above, even if the temperature of the mold is equal to or higher than the glass transition point of the glass material, fusion (fixation) of glass does not occur. The carbon film is formed by means such as a sputtering method, a plasma CVD method, a CVD method, and an ion plating method. When a film is formed by a sputtering method, the substrate temperature is 250 to 600 ° C., the RF power density is 5 to 15 W / cm ² , the sputtering degree is 5 × 10 ^{−4 to} 5 × 10 ⁻¹ torr, and the sputtering gas is Ar. It is preferable to sputter an inert gas as described above using graphite as a sputter target. When the film is formed by the microwave plasma CVD method, methane gas and hydrogen gas are used as source gases under the conditions of a substrate temperature of 650 to 1000 ° C., a microwave power of 200 W to 1 kW, and a gas pressure of 10 ^{−2 to} 600 torr. It is preferred to film. When formed by the ion plating method, it is preferable that the substrate temperature is 200 to 450 ° C. and the benzene gas is ionized. These carbon films include those having a C—H bond.

  In addition, the glass material to be molded supplied on the molding surface of the lower mold is softened by heating the glass material to be molded while floating by airflow, and by dropping the glass material to be heated and softened. It can be supplied to the mold. In particular, it is preferable that the glass material to be molded is heated and softened while being floated by an air current, and the heated and softened glass material to be molded is dropped and transferred to a preheated mold. In a low-viscosity region where the glass material to be formed is deformed by its own weight, it is not easy to prevent fusion of the glass with a jig holding the glass material to be formed during heating. In the present invention, for example, a gas to be molded is floated by an air current by ejecting gas from the inside of the jig. A gas layer is formed on both the jig surface and the glass surface, so that the jig and the glass can be heated and softened without reacting. Further, when the glass material to be molded is a preform, it can be softened by heating while substantially maintaining the shape of the preform. In addition, even if the glass material to be molded is a glass gob and has an irregular shape and surface defects such as wrinkles, it is possible to fix the shape and erase the surface defects by floating by airflow while heating and softening. It is possible.

  In the present invention, there is no particular limitation on the gas used as an air flow for floating the glass material to be formed. However, from the viewpoint that the heated glass material does not react with the jig, and further from the viewpoint of preventing deterioration of the heated jig due to oxidation, it is preferably a non-oxidizing gas, for example, nitrogen or the like. Appropriate. A reducing gas, for example, hydrogen gas or the like can be added. The flow rate of the air flow can be changed as appropriate in consideration of the shape of the opening from which the air flow is blown out, the shape and weight of the glass material to be formed, and the like. Usually, a gas flow rate in the range of 0.005 to 20 liters / minute is suitable for floating the glass material to be molded. However, if the gas flow rate is less than 0.005 liter / min, if the weight of the glass material to be molded is 300 mg or more, the glass material to be molded may not be able to sufficiently float. Further, when the gas flow rate exceeds 20 liters / minute, even if the glass weight is 2000 mg or more, the glass on the floating jig shakes greatly, and when the glass material to be molded is a preform at the time of heating, the shape is changed. This is because it may change. Further, the conditions for softening the glass material to be heated by heating can be appropriately changed depending on the type of glass and the like, and are adjusted so as to have a viscosity required for the softened glass material to be molded.

Hereinafter, the present invention will be described with reference to examples.

Example 1
In a forming apparatus for supplying a glass material to be formed by the method of the present embodiment, an upper main mold and a lower main mold having a long shape are attached to an upper main shaft and a lower main shaft of a press, respectively. The upper mold (not shown) and the lower mold 12 are attached to the lower mold 11 and the lower mold 11, respectively, and these long shapes are formed around the upper mold and the lower mold. The induction heating coil 13 wound in a similar shape is provided at two locations, that is, around the upper matrix and the lower matrix (see FIG. 17). A gap of 20 mm was provided between the upper coil and the lower coil. With this apparatus, barium borosilicate glass (transition point: 514 ° C., yield point: 545 ° C.) is pressed to form a biconvex lens having an outer diameter of 10 mm.

  Six split mold floating trays 15 (arranged at equal intervals between the upper and lower dies) are arranged in a line in a straight line on the support arm 14 that can be opened and closed, as shown in FIG. (Made of glassy carbon), and was floated and heated and softened by an air current ejected from below. Thereafter, the support arm 14 was inserted between the upper and lower induction heating coils 13, and was disposed immediately above the plurality of lower dies 12. At the same time, a guide means 17 formed by forming six funnel-shaped through holes 16 in the long plate shown in FIG. 19 was interposed between the support arm 14 and the lower mold 12. Then, by quickly opening the support arm 14, the plurality of floating plates 15 are divided into right and left, and a plurality of molded glass materials are simultaneously dropped from the floating plates 15 onto the corresponding lower molds 12, thereby lowering the glass material. It was supplied on the mold 12 (see FIG. 20). The glass material to be molded was all supplied to the center of the lower mold 12. The guide means 17 was set at 400 ° C. lower than the glass transition temperature (514 ° C.) of the glass material to be molded, and the glass material to be molded was not fused to the guide means 17. Thereafter, the support arm and the guide means were immediately retracted from above the lower mold, the high-frequency power was turned off, and the lower mold was raised to perform pressing. The above operation was repeated 1,000 times, and a stable and high-quality lens was obtained without the glass material to be molded jumping out of the molding die.

Example 2
A biconvex lens made of barium borosilicate glass was molded using the same mold as in Example 1. However, in the present embodiment, a glass material to be formed (diameter 7 mm, height 4.5 mm) hot-formed into a marble shape is used as the glass material to be formed, and guide means are used in the same manner as in Example 1; Next, after the glass material to be formed was dropped from the divided floating plate to the lower mold, the position was corrected by the position correcting means. As the position correcting means, one obtained by connecting six rings having an inner diameter slightly larger than the diameter of the glass material to be formed as shown in FIG. 16 was used. First, as shown in FIG. 21, the position correcting means 18 was arranged such that the center of each ring was aligned with the center of the corresponding lower die (see FIG. 19). Thereafter, the ring was lowered toward the lower mold 20 set on the lower mold 19, and each ring was brought into contact with the glass material 21 on the lower mold 20. When the position correcting means 18 is further lowered, the glass material 21 slides toward the center of the lower mold, whereby the center of the glass material 21 and the center of the lower mold 20 are aligned, and the position correction is completed. Next, press molding was performed in the same manner as in Example 1. A lens of good quality was obtained under any of the conditions shown in Table 1.

温度：℃、粘度：ポアズ

Temperature: ° C, viscosity: Poise

It is sectional drawing which shows the guide means of the 1st form of this invention. It is sectional drawing which shows the guide means of other form of this invention. It is sectional drawing which shows the guide means of other form of this invention. It is sectional drawing which shows the guide means of other form of this invention. FIG. 9 is a perspective view showing a guide unit according to another embodiment of the present invention. It is sectional drawing which shows the guide means of other form of this invention. It is sectional drawing which shows the guide means of other form of this invention. FIG. 5 is a diagram showing a use form of the position correcting means of the present invention. It is a figure showing the position amendment means of the first form of the present invention. FIG. 11 is a diagram illustrating a use form of a position correcting unit according to another embodiment of the present invention. FIG. 11 is a diagram illustrating a use form of a position correcting unit according to another embodiment of the present invention. It is sectional drawing which shows the position correction means of other form of this invention. It is sectional drawing which shows the position correction means of other form of this invention. FIG. 11 is a perspective view showing a position correcting unit according to another embodiment of the present invention. It is sectional drawing which shows the position correction means of other form of this invention. It is a top view which shows the position correction means of other form of this invention. FIG. 2 is a cross-sectional view showing a molding apparatus used in the method according to one embodiment of the present invention. FIG. 3 is a top view showing a divided floating dish used in the method of one embodiment of the present invention. FIG. 3 is a top view showing a position correcting means used in one embodiment of the present invention. FIG. 4 is a cross-sectional view illustrating a method according to one embodiment of the present invention. FIG. 6 is a cross-sectional view illustrating a method according to another embodiment of the present invention.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Guide part 3, 6 Lower mold 4 Position correcting means 5 Glass material to be molded

Claims (3)

A method for manufacturing a glass optical element, comprising a step of supplying a glass material to be molded by being dropped from above onto a molding surface of a lower mold of a molding die composed of an upper mold and a lower mold,
The glass material to be molded softened by heating is transferred onto the molding surface of the lower mold,
Before or after the transfer, or at the same time as the transfer, a guide means having a through-hole, which can form a falling path of the glass material to be formed and allow the glass material to be dropped substantially vertically, is provided. Inserted between the molding glass material transfer position and the lower mold,
Drop the glass material to be molded onto the lower mold forming surface,
Immediately retract the guide means from above the lower mold and perform pressure molding,
In addition, a molding glass material having a viscosity in the range of 10 ^5.5 to 10 ⁸ poise is molded with a molding die having a viscosity of 10 ⁸ to 10 ^10.5 poise (however, the temperature of the molding glass material is Pressure molding at a temperature higher than the temperature of the mold). The manufacturing method according to claim 1, wherein the softened glass material to be molded, which is floated by an air current, is supplied by being dropped. The manufacturing method according to claim 1, wherein the glass material to be formed is spherical.

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