JP2006056724A - Mold press mold and optical element manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form high precision optical elements such as a glass lens extremely high in eccentricity precision, thickness precision, and profile irregularity. <P>SOLUTION: In the state where a molding raw stock P is housed between a pair of an upper mold 3 and a lower mold 4 having opposed molding surfaces 3c and 4d respectively, the upper mold 3 and the lower mold 4 are inserted to a barrel mold 2 for regulating the mutual positional relation of the upper and lower molds 3 and 4, and while pressing the upper mold 3 via an interposing member 5 which is placed on the upper surface 3d of the upper mold 3 and provided with a spherical projection 10 at almost the center of its upper surface and a vent hole 5c communicating with the upper surface 3d of the upper mold 3, the lower surface 5a of the interposing member 5 is made to abut on the upper surface 3d of the upper mold 3 and the upper surface 2a of the barrel mold 2, then the mold 1 is cooled, and the upper mold 3 is lowered by its own weight while following the volume shrinkage of the molding raw stock by cooling. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a mold press molding die for molding a high-precision optical element such as a glass lens having extremely high eccentricity accuracy, thickness accuracy, and surface accuracy, which is used for an optical pickup, a small imaging device, and the like, and manufacture of the optical element. It is about the method.

  In recent years, so-called digital products typified by CD / DVD recording / playback apparatuses and mobile phones have rapidly spread. Optical elements such as an objective lens used for an optical pickup mounted on a CD / DVD recording / reproducing apparatus and an imaging lens used for a small imaging device mounted on a cellular phone require high resolution, such as high resolution. Is extremely high. Furthermore, in order to reduce the size of the apparatus and simplify the assembly, the number of lenses used in the lens system is limited, and realization of high optical performance with a single lens is required.

  Under such circumstances, these devices often use both aspherical lenses. In particular, in a high-capacity optical recording pickup with a high recording density, it is necessary to increase the numerical aperture (for example, NA 0.6 or more) in order to increase the resolution of the objective lens. Due to the need for spherical aberration correction (for example, 450 mm or less) and the like, it is strongly required to make the lens surface an aspherical surface.

  An aspheric lens satisfying such optical performance has a smaller radius of curvature than conventional lenses, and the inclination angle of the lens surface with respect to a surface perpendicular to the optical axis passing through the apex of the lens surface increases as the numerical aperture increases. . Specifically, it may be 40 degrees or more, and in some cases 50 degrees or more. For this reason, the manufacturing tolerance of the lens is extremely strict, and in particular, the eccentricity accuracy becomes a problem, and the coincidence (coaxiality) between the axis of the first surface of the lens and the axis of the second surface must be strictly controlled.

  By the way, as a technique for manufacturing an aspheric glass lens, there is known a technique called a mold press in which a glass material (preform) is heated and pressed using a mold whose molding surface is processed into an aspheric surface. In order to manufacture an aspherical glass lens by such a method, for example, molding surfaces formed on the upper and lower molds by heating and pressurizing the preform with an upper mold and a lower mold that are coaxially inserted into the body mold. However, in order to accurately transfer without losing the coaxiality of the lens surface, it is necessary to ensure the coaxiality of the upper and lower molds with high accuracy. For this reason, when manufacturing a lens with an upper mold and a barrel mold, and a lower mold and a barrel mold with a clearance of about 1 to 10 μm and an NA of 0.8, the molding die is made by precision machining with a suppression of about 0 to 5 μm. It is required to be produced.

  For example, in Patent Document 1, the upper die is pressed from above through a push plate to slide in the guide die (body die), and the lower surface of the push plate is brought into contact with the upper surface of the guide die. The upper surface and the upper surface of the guide mold form the same plane. Thereby, the inclination of the upper mold and the lower mold can be prevented and the coaxiality of the upper and lower molds is secured, so that a lens with high surface accuracy can be obtained.

  On the other hand, in Patent Document 2, if there is a sliding fitting portion between the fixed mold (body mold) and the upper mold, it is difficult to completely match the axis of the lower mold with the axis of the upper mold. If the axis of the lower mold does not coincide with the axis of the upper mold, the centroids of both functional surfaces of the lens do not coincide with the optical axis, and the lens is decentered. For this reason, in Patent Document 2, the upper mold is pressed against an inclined ring zone provided on the trunk mold without inserting the upper mold into the trunk mold, and the pressing point at which the press load is applied to the upper mold is centered. A pressing protrusion is provided on the pressing surface of the upper mold in order to ensure the pressure contact with the inclined ring zone even if it is displaced.

Japanese Patent Publication No. 2-28460 Japanese Examined Patent Publication No. 4-42338

  However, even if the eccentric accuracy of the mold itself is strictly controlled as in Patent Document 1, it is necessary to consider the influence of a large external force such as a press load. If the relative positional relationship between the members of the mold is lost during the pressing operation due to the press load, the coaxiality of the lens surface is impaired, and a lens that satisfies the predetermined optical performance cannot be obtained.

  Furthermore, the press shaft of the press device does not always operate accurately vertically. Rather, there is often a slight tilt (tilt) between the press shaft of the press device and the axis of the mold. Further, since the tip of the press shaft is heated in the molding apparatus, it is necessary to consider thermal deformation of the press head. Thus, when a press load is applied to the mold, the press head that pressurizes the pressing plate does not necessarily contact the pressing plate from the vertical direction.

  The press head surface is pressed at an angle between the press plate and the press plate due to an inclination between the press shaft and the mold center, and the press load is applied while the press head surface is inclined with respect to the press plate. When applied, the pressing plate and the mold may be inclined due to the inclination of the press head surface. If a strong external force with components other than the axial direction is applied to the mold, the relative positional relationship between the trunk mold, the upper mold, and the lower mold is not accurately defined, and the upper mold falls within the trunk mold. The problem occurs. As a result, the coaxiality of the lens surface is lost due to the relative tilting of the upper mold and the lower mold, and the optical performance of the obtained lens is deteriorated.

  Moreover, in the shaping | molding die of patent document 2, a sliding fitting part is not provided, but the position control of the up-and-down type | mold by a trunk | drum type is not performed as a result. For this reason, there is no problem in forming a spherical lens, but it is impossible to obtain both aspherical lenses. In order to obtain both aspherical lenses, how to match the center axis that has only one molding surface of the upper mold and the molding surface of the lower mold (how to prevent the shift and tilt of the upper and lower mold axes) Although it becomes a subject, the shaping | molding die of patent document 2 is a structure which accept | permits the fall of an upper mold | type positively, Comprising: The said subject is not examined at all.

  In order to mold a high-precision aspherical lens, the upper and lower molds are centered when the position of the upper and lower molds is strictly regulated and a strong external force having components other than the axial direction is received from the press axis. Further measures are necessary to prevent the two from shifting from each other (shifting and tilting of the upper and lower axes).

  The present invention has been proposed in order to solve the problems of the conventional techniques as described above, and molds a high-precision optical element such as a glass lens having extremely high eccentricity accuracy, thickness accuracy, and surface accuracy. An object of the present invention is to provide a mold press mold and a method for manufacturing an optical element.

  The mold press mold according to the present invention regulates a horizontal positional relationship between a pair of upper mold and lower mold having opposed molding surfaces and the upper mold and lower mold by inserting the upper mold and the lower mold. A body mold that is placed on the upper surface of the upper mold, and a lower surface of the body mold that is in contact with the upper surface of the upper mold and the upper surface of the body mold by applying a press load. A mold press molding die that accommodates and press-molds a molding material between the upper die and the upper surface of the upper die and the upper surface of the barrel die are in positions where they abut against the lower surface of the interposed member. A gap allowing the lowering of the upper die is formed between the upper die and the barrel die, and the interposition member is provided with a press load application portion at substantially the center of the upper surface, and the upper surface of the upper die is provided. It is the structure which provided the vent hole connected to the space outside a type | mold.

  By adopting such a configuration, when the press load is applied, the interposition member abuts on the upper surface of the upper mold and the upper surface of the trunk mold, thereby defining the mutual position in the axial direction of the upper mold and the trunk mold, Further, by regulating the mutual inclination, vertical coaxiality is ensured. In addition to this, if the press load is applied to the press load application section provided substantially at the center of the interposition member substantially by point contact, the vertical coaxial deterioration due to the tilt angle of the press shaft is reduced. Can be prevented.

  In addition, since the press load application section is provided at the approximate center of the upper surface of the interposition member, the surrounding area must be thick enough to withstand the application of the press load. Therefore, a sealed space is formed in a portion surrounded by the upper mold and the interposed member (including a contact portion between the upper mold and the interposed member), and the lowering due to the weight of the upper mold is hindered. In the present invention, the intervening member is provided with a vent hole that allows the upper surface of the upper mold to communicate with the space outside the mold. This allows the atmosphere gas to flow into the portion surrounded by the upper mold and the intervening member, and the heating press The state in which the molding material is in close contact with the molding surface of the upper mold can be maintained without hindering the lowering of the upper mold following the volume shrinkage accompanying the cooling of the molded material.

  In the mold press mold according to the present invention, when the lower surface of the interposition member comes into contact with the upper surface of the upper mold and the upper surface of the body mold, the upper surface of the upper mold and the upper surface of the body mold are the same. From the viewpoint of processing accuracy, it is preferable to form a flat surface so as to ensure the vertical coaxiality.

  In such a mold press mold according to the present invention, it is preferable that the press load application portion includes a spherical protrusion formed substantially at the center of the upper surface of the interposition member. As a result, when the press head applies a press load to the interposition member, the press head substantially contacts the spherical protrusion at a point. For this reason, even if an inclination occurs between the press shaft and the axis of the mold, the force acting in the direction other than the axial direction is small, and the press load from the press head substantially acts on the interposition member in the axial direction. In other words, it is possible to prevent the vertical type coaxiality from being impaired.

  Further, by providing a convex portion on the upper surface of the upper mold and providing a concave portion for accommodating the convex portion on the lower surface of the interposed member, it is possible to prevent the positional displacement of the interposed member. In addition, it is possible to define the mutual positions of the cylinder and the cylinder in the axial direction, and to prevent the function of the interposition member that regulates the mutual inclination from being impaired.

  Moreover, it is preferable that the body portion is provided with a through hole that communicates the gap formed between the upper mold and the body mold and a space outside the mold. When the upper mold descends following the volume shrinkage accompanying the cooling of the molding material, the volume of the gap decreases, but by adopting the above configuration, the atmospheric gas in the gap is released to the space outside the mold through the through hole. The Thereby, the upper mold is smoothly lowered, and the state where the molding material is in close contact with the molding surface of the upper mold can be more reliably maintained.

  On the other hand, an optical element manufacturing method according to the present invention is an optical element manufacturing method in which a molding material is heated and pressed into a predetermined shape, and a pair of upper mold and lower mold having opposed molding surfaces are The molding material is inserted between the molding surfaces of the upper die and the lower die, and inserted into a body die that regulates the horizontal positional relationship between the upper die and the lower die, and then the molding material is heated. In this state, a press load is applied in a substantially point contact to a press load application section provided substantially at the center of the upper surface of the interposition member placed on the upper surface of the upper mold, and the lower surface of the interposition member is The molding material is brought into contact with the upper surface of the mold and the upper surface of the body mold, and then the molding die is cooled, and the upper mold is lowered following the volume shrinkage of the molding material by cooling, whereby the molding material is placed on the molding surface of the upper mold. It is configured to maintain a close contact state.

  With this configuration, it is possible to manufacture an optical element having excellent decentering accuracy, thickness accuracy, and surface accuracy. Even if the optical element to be manufactured is a bi-aspheric lens, the first lens surface And the second lens surface can be molded with high accuracy without impairing the coaxiality.

  Further, in the method of manufacturing an optical element according to the present invention, the interposition member is provided with a vent hole for communicating the upper surface of the upper mold with which the lower surface of the interposition member abuts with a space outside the mold, and the upper mold is a molding material. It is preferable that an atmospheric gas is caused to flow from the vent hole between the interposition member and the upper mold when descending following the volume shrinkage. This maintains the surface accuracy of the resulting optical element by maintaining the molding material in close contact with the molding surface of the upper mold without hindering the lowering of the upper mold following the volume shrinkage of the molding material. Can do.

  Further, a gap that allows the upper mold to descend is formed between the upper mold and the body mold, and a through hole that communicates the gap and a space outside the mold is formed in the body portion. When the upper mold descends following the volume shrinkage of the molding material, it is preferable to release the atmospheric gas in the gap from the through hole. By doing so, the atmospheric gas in the gap is released to the space outside the mold through the through hole, so that the upper mold can be smoothly lowered by cooperation with the vent hole provided in the interposed member. The state in which the molding material is in close contact with the molding surface of the upper mold can be more reliably maintained. This is extremely advantageous in increasing the surface accuracy of the optical element to be molded.

  According to the present invention, an optical element excellent in eccentricity accuracy, wall thickness accuracy, and surface accuracy can be manufactured by cooperation with the interposition member, the upper and lower molds, and the body mold. Even if it is a spherical lens, it can be molded with high accuracy without impairing the coaxiality between the first lens surface and the second lens surface.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an outline of an embodiment of a mold press mold according to the present invention. In the illustrated example, the mold 1 includes a body mold 2, an upper mold 3, a lower mold 4, and an interposed member 5.

  In the present embodiment, the upper surface 2a and the lower surface 2b of the body mold 2 are subjected to planar processing so that a smooth flat surface perpendicular to the axis A of the body mold 2 is formed. In addition, an upper mold insertion portion 6 having an inner peripheral surface which is composed of a large-diameter inner peripheral portion 6a and a small-diameter inner peripheral portion 6b and which is parallel to the axis A of the main die 2 is provided on the upper portion of the barrel mold 2. It is formed so as to open on the upper surface 2 a side of the mold 2. On the other hand, in the lower part of the body mold 2, a lower mold insertion part 7 having an inner peripheral surface which is composed of a large diameter inner peripheral part 7 a and a small diameter inner peripheral part 7 b and which is parallel to the axis A of the body mold 2 is provided. It is formed so as to open on the lower surface 2 b side of the mold 2. The small-diameter inner peripheral portion 6a of the upper mold insertion portion 6 and the small-diameter inner peripheral portion 7b of the lower mold insertion portion 7 are formed so as to pass through the body mold 2 and be continuous.

  In the present embodiment, the upper mold 3 is inserted into the upper mold insertion portion 6 from the upper surface 2a side of the trunk mold 2, as shown in FIG. The interposition member 5 is mounted thereon. The lower mold 4 is inserted into the lower mold insertion portion 7 from the lower surface 2 b side of the trunk mold 2.

  The lower mold 4 inserted into the lower mold insertion portion 7 from the lower surface 2b side of the body mold 2 has a shape in which three cylinders having different diameters are coaxially stacked, and has a large diameter portion 4a, a medium diameter portion 4b, and a small diameter portion. 4c. In the lower mold 4 having such a shape, a molding surface 4d corresponding to one optical surface of the optical element to be obtained is formed by precision machining on the surface facing the upper mold 3 of the small diameter portion 4c. At least the outer peripheral surfaces of the medium diameter portion 4b and the small diameter portion 4c are formed to be parallel to the central axis of the molding surface 4d.

  The outer diameters of the middle diameter portion 4b and the small diameter portion 4c of the lower mold 4 are substantially the same as the inner diameters of the large diameter inner peripheral portion 7a and the small diameter inner peripheral portion 7b of the lower mold insertion portion 7 of the trunk mold 2. Formed to be. At this time, the clearance C4 between the medium diameter part 4b and the large diameter inner peripheral part 7a of the lower mold insertion part 7 is, for example, 10 μm or less, preferably 5 μm or less. On the other hand, the clearance C3 between the small diameter portion 4c and the small diameter inner peripheral portion 7b of the lower mold insertion portion 7 is set to 50 μm or less, preferably 10 μm or less.

  Further, the height L3 of the middle diameter portion 4b of the lower mold 4 is formed to be slightly lower than the height L4 of the large diameter inner peripheral portion 7a in the lower mold insertion portion 7 of the trunk mold 2. The upper surface 4e of the large-diameter portion 4a of the lower mold 4 is flattened so that a smooth surface perpendicular to the central axis of the molding surface 4d is formed so as to be in close contact with the lower surface 2b of the body mold 2. To. Accordingly, when the lower mold 4 is inserted into the lower mold insertion portion 7 of the trunk mold 2, the lower mold 4 is formed on the lower surface 2b of the trunk mold 2 on which a smooth surface perpendicular to the axis A of the trunk mold 2 is formed. By simply bringing the upper surface 4e of the large diameter portion 4a into close contact, the mutual positional relationship between the body mold 2 and the lower mold 4 is high so that the central axis of the molding surface 4d and the axis A of the body mold 2 coincide. It can be defined with accuracy.

  On the other hand, the upper mold 3 inserted into the upper mold insertion portion 6 from the upper surface 2a side of the body mold 2 has a shape in which two cylinders having different diameters are coaxially stacked, and includes a large diameter portion 3a and a small diameter portion 3b. ing. In the upper mold 3 having such a shape, a molding surface 3c corresponding to the other optical surface of the optical element to be obtained is formed by precision machining on the surface facing the lower mold 4 of the small diameter portion 3b. And the outer peripheral surface of the large diameter part 3a and the small diameter part 3b is formed so that it may become parallel to the central axis of the molding surface 3c.

  The large-diameter portion 3a and the small-diameter portion 3b of the upper mold 3 are formed so as to have substantially the same diameter as each of the large-diameter inner peripheral portion 6a and the small-diameter inner peripheral portion 6b of the upper mold insertion portion 6 of the body mold 2. The At this time, the clearance C1 between the large-diameter portion 3a and the large-diameter inner peripheral portion 6a of the upper die insertion portion 6 is, for example, in the range of 10 μm or less, preferably 5 μm or less, and the upper die 3 slides relative to the trunk die 2. To be movable. On the other hand, the clearance C2 between the small-diameter portion 3b and the small-diameter inner peripheral portion 6b of the upper mold insertion portion 6 is set to a range of 50 μm or less, preferably 10 μm or less.

  Thereby, when the upper mold 3 is inserted into the upper mold insertion portion 6 of the trunk mold 2, the central axis of the molding surface 3 c of the upper mold 3 and the axis A of the trunk mold 2 can be matched. The body mold 2 and the upper mold 3 are slid so that the upper mold 3 slides in the body mold 2 in a state where the central axis of the molding surface 3c of the upper mold 3 and the axis A of the body mold 2 coincide with each other. Can be defined with high accuracy. Therefore, as described above, the axis A of the body mold 2 is made to coincide with the central axis of the molding surface 4d of the lower mold 4, so that the central axis of the molding surface 3c of the upper mold 3 and the molding surface of the lower mold 4 are aligned. Coaxiality with the central axis of 4d (upper and lower type coaxiality) is ensured.

  Accordingly, if the upper die 3 is flattened so that a smooth surface perpendicular to the central axis of the molding surface 3c of the upper die 3 is formed on the upper surface 3d of the upper die 3, the upper die 3 passes through the body die 2 by a predetermined amount. When sliding, the same plane is formed by the upper surface 3d of the upper mold 3 and the upper surface 2a of the body mold 2 as shown in FIG. Therefore, the press load is applied so that the upper surface 3d of the upper mold 3 perpendicular to the central axis of the molding surface 3c of the upper mold 3 and the upper surface 2a of the trunk mold 2 perpendicular to the axis A of the trunk mold 2 are in the same plane. As long as the voltage is applied, vertical coaxiality is ensured.

  At this time, even if the upper surface 3d of the upper mold 3 and the upper surface 2a of the body mold 2 are not on the same plane but are parallel planes, the shape of the interposition member 5 is processed so that the parallel relationship is maintained. By doing so, the vertical coaxiality is ensured. However, as will be described later, when the lower surface 5a of the interposition member 5 comes into contact with both the upper surface 3d of the upper mold 3 and the upper surface 2a of the trunk mold 2, the upper surface 3d of the upper mold 3 and the upper surface of the trunk mold 2 From the viewpoint of processing accuracy, it is preferable that the upper and lower molds have coaxiality so that 2a forms the same plane.

  In the present embodiment, the interposition member 5 is placed on the upper surface 3 d of the upper mold 3. The interposition member 5 is located between the press head and the upper die 3 in a press process described later. Further, the intermediate member 5 has a substantially central portion on the upper surface serving as a press load application portion, and a press load from the press head is directly applied to the press load application portion. Therefore, if the lower surface 5a of the interposing member 5 is a flat surface, both the upper surface 3d of the upper die 3 and the upper surface 2a of the trunk die 2 are changed by applying a press load to the interposing member 5. The upper surface 3d of the upper mold 3 and the upper surface 2a of the body mold 2 can be made to be in the same plane. Thereby, even the mutual inclination which can be permitted within the small clearance between the upper die 3 and the barrel die 2 is restricted, and the coaxiality of the upper and lower dies at the time of press load can be ensured.

  Further, the thickness of the molding material is once defined by the relative distance between the molding surface 3c of the upper mold 3 and the molding surface 4d of the lower mold 4 at this time. At this time, since the coaxiality of the upper and lower molds is ensured, the thickness of the molding material is accurately defined. Therefore, although the volume of the molding material shrinks in the cooling step described later, high wall thickness accuracy can be obtained by defining the wall thickness at the above stage.

  Thus, the interposition member 5 has a function of making the upper surface 3d of the upper mold 3 and the upper surface 2a of the body mold 2 in the same plane so that the coaxiality of the upper and lower molds is ensured when a press load is applied. Have. Accordingly, it is preferable that the lower surface 5a of the interposition member 5 is in contact with at least an adjacent portion of the upper surface 3d of the upper mold 3 and the upper surface 2a of the body mold 2 over the entire circumference. If the amount is insufficient, the above functions are impaired.

  For this reason, in this embodiment, as long as the function of the interposed member 5 is not impaired, as shown in FIG. It is preferable to prevent the interposition member 5 from being displaced by providing the lower surface 5a with a concave portion 5b for accommodating the convex portion 9. Thereby, for example, when the mold 1 is transported by a high-speed robot, the displacement of the interposed member 5 and the slipping-off are completely prevented.

  Furthermore, by forming the convex portion 9 on the upper surface 3d of the upper mold 3, for example, when the molding die 1 is assembled by a robot, the convex portion 9 can function as a handle of the upper mold 3. By processing with high positional accuracy, it can also be used as a position detection unit when the upper mold 3 is inserted into the body mold 2.

  Further, in the present embodiment, a spherical protrusion 10 as shown in FIG. 1 is formed at substantially the center of the upper surface of the interposed member 5. The spherical protrusion 10 functions as a press load application unit, and a press load is applied to the interposition member 5 when the press head contacts the spherical protrusion 10. Here, the spherical protrusion 10 refers to a protrusion having a surface that can substantially make point contact with the press head. In this embodiment, a part of a sphere (or a substantially spherical solid) is cut off in a horizontal plane. The protrusion has a shape.

  By forming such a spherical protrusion 10 on the upper surface of the interposition member 5, the press head substantially contacts the spherical protrusion 10 at a point when the press head applies a press load to the interposition member 5. For this reason, even if an inclination occurs between the press shaft and the axis of the mold, the force acting in the direction other than the axial direction is small, that is, the press load from the press head acts in the radial direction of the spherical protrusion 10. However, at this time, the component orthogonal to the axial direction becomes smaller. Therefore, the press load from the press head substantially acts in the axial direction with respect to the interposition member 5, and it is possible to prevent the upper and lower molds from being damaged.

  Furthermore, in the present embodiment, the height L1 of the large-diameter portion of the upper mold 3 is relatively lower than the height L2 of the large-diameter inner peripheral portion 6a in the upper mold insertion portion 6 of the trunk mold 2. Form. That is, as shown in FIG. 1, when the upper surface 2a of the body mold 2 and the upper surface 3d of the upper mold 3 are positioned on the same plane, the lower surface 3e of the large-diameter portion 3a of the upper mold 3 and the body mold 2 A gap G is formed between the bottom surface 6 c of the large-diameter inner peripheral portion 6 a in the upper mold insertion portion 6. At this time, in the vicinity of the height where the gap G of the body mold 2 is formed, in order to release the atmospheric gas in the space G, a through hole 8 for venting gas that penetrates the body mold 2 in the thickness direction is provided. Keep it.

  In a pressing process to be described later, a molding material such as a glass preform that is sandwiched between the molding surface 3c of the upper mold 3 and the molding surface 4d of the lower mold 4 and molded into a predetermined shape is cooled after the pressing process is completed. However, if such a gap G is formed, the upper die 3 is lowered by its own weight or the like as the volume shrinks due to cooling of the molding material, and the molding surface 3c of the upper die 3 is kept in close contact with the molding material. can do. Thereby, the shape of the molding surface 3c can be accurately transferred to the molding material, and the surface accuracy of the obtained optical element can be maintained well.

  By the way, in the present embodiment, as described above, the lower surface 5a of the interposed member 5 is brought into contact with the upper surface 3d of the upper mold 3 in close contact with each other. A portion surrounded by the member 5 (specifically, a contact portion between the lower surface 5a of the interposed member 5 and the upper surface 3d of the upper die 3 and a recess 5b provided on the lower surface 5a of the interposed member 5; The volume of the space formed between the convex portion 9 provided on the upper surface 3d of the upper mold 3 is increased and the portion is in a negative pressure state, preventing the upper mold 3 from descending following the volume shrinkage of the molding material. End up.

  In particular, since the spherical protrusion 10 is formed in the center of the upper surface of the interposing member 5 and a press load is applied to the spherical protrusion 10, the wall thickness around the spherical protrusion 10 is sufficient to withstand the application of the press load. Must be kept. For this reason, the part enclosed by the upper mold | type 3 and the interposition member 5 will necessarily become a sealed space. For this reason, in this embodiment, the intervening member 5 is provided with a vent hole 5c that penetrates the interposition member 5 in the thickness direction and communicates the upper surface 3d of the upper mold 3 with the space outside the mold. That is, the vent hole 5c that penetrates the interposition member 5 in the thickness direction, has one end opening toward the outside of the mold 1 and the other end opening toward the upper surface 3d of the upper mold 3. Is provided on the interposing member 5.

  By providing such an air hole 5c in the interposition member 5, the portion surrounded by the upper mold 3 and the interposition member 5 does not become a sealed space, and atmospheric gas can be allowed to flow into the portion. Thereby, the state where the molding surface 3c of the upper mold 3 is in close contact with the molding material can be maintained without hindering the lowering of the upper mold 3. The vent hole 5c provided in the interposition member 5 is not limited to the form shown in FIG. 1, and a groove or a cut is formed in the lower surface 5a of the interposition member 5 as long as the surface contact with the upper surface 3d of the upper mold 3 is not impaired. The vent hole 5c can be provided by forming a notch.

  Next, a method for manufacturing an optical element according to an embodiment of the present invention will be described by taking as an example a case where an optical element is molded using the mold 1 described above. FIG. 2 is a schematic diagram illustrating an example of a molding step in the method for manufacturing an optical element according to an embodiment of the present invention.

  In order to manufacture an optical element according to the method for manufacturing an optical element according to the present embodiment, a molding material P such as a glass preform is supplied into the mold 1 prior to molding. Specifically, the upper mold 3 is inserted into the upper mold insertion portion 6 of the trunk mold 2 and the interposed member 5 is placed thereon, the lower mold 4 is lowered and extracted from the trunk mold 2. Then, the molding material P is supplied onto the molding surface 4d of the lower mold 4 by, for example, an unillustrated auto hand with a suction pad (FIG. 2A). At this time, the molding material P may be supplied at room temperature or may be supplied after being heated to a predetermined temperature.

  Next, the lower mold 4 is raised and inserted into the lower mold insertion portion 7 of the trunk mold 2 from the lower surface 2b side (FIG. 2B), and the upper surface 4e of the large-diameter portion 4a of the lower mold 4 is used as the lower surface of the trunk mold 2. Adhere to 2b. At this time, due to the thickness of the molding material P, the upper surface 3d of the upper mold 3 protrudes upward with respect to the upper surface 2a of the body mold 2, and the interposition member 5 is placed on the upper mold 3 ( FIG. 2 (c)). Thereafter, the entire mold 1 is placed on a horizontal placing table (not shown).

When the supply of the molding material P into the molding die 1 is completed, the molding die 1 containing the molding material P is sent to the heating process. The heating conditions in the heating step vary depending on the molding material P to be used, but the temperature of the molding material P is a temperature range suitable for press molding, for example, a viscosity equivalent to 10 ⁶ to 10 ⁹ dPa · s. It is a condition. After the heat treatment in the heating process is performed, the mold 1 placed on the horizontal placing table is sent to the pressing process as it is.

In the pressing step, the pressing means is provided with a press head (not shown) driven by an air cylinder or a hydraulic cylinder, and the press head is brought into contact with the interposition member 5 from above the mold 1 to apply a press load. The press load at this time is usually about 50 to 200 kgf / cm ² . Since the molding material P is sufficiently softened by the heat treatment in the heating process, the upper mold 3 is pushed down while sliding in the body mold 2. Thus, the molding material P sandwiched between the upper mold 3 and the lower mold 4 is molded into a predetermined shape by transferring the shapes of the molding surfaces 3c and 4d.

  When the lower surface 5a of the interposition member 5 comes into contact with the upper surface 2a of the body mold 2, the pressing of the molding material P by the upper mold 3 is substantially stopped, and the thickness of the molding material P is determined with good reproducibility. Is done. At this time, since the upper surface 3d of the upper mold 3 and the upper surface 2a of the trunk mold 2 form the same plane, the tilt of the upper mold 3 with respect to the trunk mold 2 is substantially zero (FIG. 2 (d)). . As a result, the thickness accuracy of the obtained optical element can be improved.

  At this time, by applying a press load, the body mold 2 is strongly pressed against the large-diameter portion 4a of the lower mold 4, and the mutual positional relationship between the lower mold 4 and the body mold 2 is accurately maintained. As a result, the tight pressure contact due to the application of the press load determines the mutual positional relationship between the lower die 4 and the barrel die 2 and the mutual positional relationship between the barrel die 2 and the upper die 3, and the upper and lower dies are coaxial. Secured.

  Furthermore, since the spherical protrusion 10 is formed at substantially the center of the upper surface of the interposition member 5, the press head and the interposition member 5 are substantially in contact with each other at a point. For this reason, even if there is an inclination between the press shaft and the axis of the mold, the press load from the press head substantially acts on the interposition member 5 in the axial direction. Tight pressure contact between each member at the time of applying a press load also functions effectively, and it is possible to prevent the upper and lower molds from being damaged. Thereby, the eccentric accuracy of the obtained optical element can be made favorable.

  Thereafter, the molding die 1 is cooled in a state in which the molding material P is accommodated, and the temperature is lowered to a temperature near or below the glass transition point of the molding material P (FIG. 2 (e)). At this time, the molding material P in the molding die 1 is cooled and its volume shrinks. At this time, if the adhesion between the molding material P and the molding surface is released, the surface accuracy deteriorates.

  However, as described above, a gap G is formed between the lower surface 3e of the large-diameter portion 3a of the upper mold 3 and the bottom surface 6c of the large-diameter inner peripheral portion 6a of the upper mold insertion portion 6 of the trunk mold 2, A through hole 8 is provided in the vicinity of this position. For this reason, the atmospheric gas in the gap G whose volume decreases as the upper mold 3 descends can be released through the through hole 8. On the other hand, the upper surface 3d of the upper mold 3 and the lower surface 5a of the interposition member 5 are in close contact with each other, but the interposition member 5 is provided with a vent hole 5c that allows inflow of atmospheric gas. For this reason, the space surrounded by the upper mold 3 and the interposition member 5 does not become negative pressure, and the upper mold 3 smoothly descends following the contraction of the molding material P (see FIG. 2E). Thereby, since it cools in the state which maintained close_contact | adherence with the shaping | molding raw material P and the shaping | molding surfaces 3c and 4d of an up-and-down type | mold, surface precision can be maintained favorable.

  After finishing such a cooling step, the lower mold 4 is lowered and extracted from the body mold 2 (FIG. 3 (f)), and the molded body S on the molding surface 4d of the lower mold 4 is taken out. By molding the molding material P with such a mold press, an optical element having excellent eccentricity accuracy, thickness accuracy, and surface accuracy can be manufactured. Even if it exists, it can shape | mold with high precision, without impairing the coaxial property of a 1st lens surface and a 2nd lens surface. In particular, high-precision molding that satisfies the optical performance required for precision optical elements such as an optical pickup objective lens having an NA of 0.6 or more and an imaging lens for a small imaging device is possible.

  Next, a modification of the present embodiment will be described with reference to the drawings. FIG. 3 is a sectional view showing an outline of the first modification, and FIG. 4 is a sectional view showing an outline of the second modification.

  In the example shown in FIG. 1, the convex portion 9 is provided on the upper surface 3 d of the upper mold 3, and the concave portion 5 b that accommodates the convex portion 9 is provided on the lower surface 5 a of the interposition member 5. The convex part 9 can also be abbreviate | omitted as needed, as shown in FIG.

  In the example shown in FIG. 1, the spherical protrusion 10 is formed at substantially the center of the upper surface of the interposition member 5 so that the press head and the interposition member 5 are in contact with each other when a press load is applied. In the present embodiment, even if the press head substantially contacts the press load application portion at the center of the upper surface of the interposition member 5 at a point and an inclination occurs between the press shaft and the axis of the molding die, For example, instead of providing the spherical protrusion 10 on the upper surface of the interposition member 5, as shown in FIG. 4, a spherical protrusion 11b is provided at substantially the center of the press surface 11a of the press head 11, as long as the coaxiality of the mold can be prevented. May be provided. In this case, the press load application part on the upper surface of the interposition member 5 is formed in a plane as shown in FIG.

  Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention. Nor.

  As described above, according to the present invention, an optical element such as a glass lens having extremely high eccentricity accuracy, thickness accuracy, and surface accuracy, which is used for an optical pickup, a small imaging device, and the like can be manufactured with high accuracy.

It is sectional drawing which shows the outline of one Embodiment of the mold press molding die which concerns on this invention. It is the schematic which shows an example of the shaping | molding process in the manufacturing method of the optical element which concerns on this invention. It is sectional drawing which shows the outline of the 1st modification of one Embodiment of the mold press molding die which concerns on this invention. It is sectional drawing which shows the outline of the 2nd modification of one Embodiment of the mold press molding die which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Molding die 2 Body die 2a Upper surface 3 Upper die 3c Molding surface 3d Upper surface 4 Lower die 4d Molding surface 5 Interposition member 5a Lower surface 5b Recessed portion 5c Venting hole 8 Through hole 9 Protruding portion 10 Spherical protrusion A Axis center G Gap

Claims (8)

A pair of upper and lower molds having opposing molding surfaces; a body mold into which the upper mold and the lower mold are inserted to restrict the horizontal positional relationship between the upper mold and the lower mold; and an upper surface of the upper mold The lower surface of the upper die and the upper surface of the barrel die by an application of a press load, and a molding material is accommodated between the upper die and the lower die. A mold press mold for press molding,
When the upper surface of the upper mold and the upper surface of the trunk mold are in contact with the lower surface of the interposition member, a gap allowing the lowering of the upper mold is between the upper mold and the trunk mold. Formed,
A mold press molding die characterized in that the interposed member is provided with a press load application portion at substantially the center of the upper surface, and a vent hole for communicating the upper surface of the upper die with a space outside the die.   2. The mold press according to claim 1, wherein the upper surface of the upper mold and the upper surface of the barrel mold form the same plane when the lower surface of the interposition member contacts the upper surface of the upper mold and the upper surface of the barrel mold. Mold.   3. The mold press mold according to claim 1, wherein the press load application section includes a spherical protrusion formed substantially at the center of the upper surface of the interposition member.   The mold press mold according to any one of claims 1 to 3, wherein a convex portion is provided on an upper surface of the upper mold, and a concave portion for accommodating the convex portion is provided on a lower surface of the interposition member.   The mold press molding die in any one of Claims 1-4 which provided the through-hole which connects the said space | gap formed between the said upper mold | type and the said trunk | drum, and the space outside a type | mold in the said trunk | drum. . A method of manufacturing an optical element that heats and presses a molding material into a predetermined shape,
A pair of upper and lower molds having opposed molding surfaces are inserted into a barrel mold that regulates the horizontal positional relationship between the upper mold and the lower mold, and between the molding surfaces of the upper mold and the lower mold. Supply molding materials to
Next, in a state where the molding material is heated, a press load is applied substantially by point contact to a press load application unit provided at substantially the center of the upper surface of the interposition member placed on the upper surface of the upper mold. The lower surface of the interposition member is brought into contact with the upper surface of the upper mold and the upper surface of the trunk mold,
After that, the molding die is cooled, and the upper die is moved down following the volume shrinkage of the molding material due to cooling, thereby maintaining the state where the molding material is in close contact with the molding surface of the upper die. Production method.   The interposition member is provided with a vent hole that communicates the upper surface of the upper mold with which the lower surface of the interposition member abuts the space outside the mold, and when the upper mold descends following the volume shrinkage of the molding material, The method for manufacturing an optical element according to claim 6, wherein an atmospheric gas is caused to flow from the vent hole between the interposition member and the upper mold.   A gap that allows the upper mold to descend is formed between the upper mold and the trunk mold, and a through hole that communicates the gap and a space outside the mold is formed in the trunk portion, and the upper mold The manufacturing method of the optical element according to claim 6 or 7, wherein when the gas descends following the volume shrinkage of the molding material, the atmospheric gas in the gap is released from the through hole.

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