JP2007331311A - Optical element molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element molding method which enables the suppression of a performance degradation accompanying the anisotropy of a shape deviation and a density deviation of an optical element molded article produced by the shape deviation of a premolding raw material. <P>SOLUTION: According to an aspect of the invention, the optical element molding method comprises: a first process of injection molding the premolding raw material 100 consisting of a lens constitution surface 120 and a flange portion 110 provided on the outer edge of the lens constitution surface, and projecting a gate part 130 at one end of the flange portion; a second process of cutting off one end of the flange portion containing the gate part as a cut part 112, and at the same time, of cutting off the other end of the flange portion as a shape compensation part 114 such that the shape of the flange portion become axisymmetric to the light axis of the lens constitution surface; and a third process of press molding in a state in which the premolding raw material molded in the second process is heat softened, and of molding the optical element molded article 150. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical element molding method.

  2. Description of the Related Art In recent years, various optical elements used in optical systems have been developed with the reduction in size and weight and the increase in functionality of optical devices. In particular, in products using optical disk lenses such as DVDs (Digital Versatile Disks) such as pickup lenses used in optical equipment, a high numerical aperture of optical elements is required. In addition, Blu-ray discs (large-capacity phase-change optical discs), which are considered to be the “next-generation DVD” standard, use a high numerical aperture lens together with a short wavelength blue-violet laser to realize high-density data recording. The demand for higher numerical apertures for elements is expected to increase further in the future.

  As a method for molding an optical element, precision press molding is known in which an optical element is molded by placing a preforming material such as a preform on a press mold and press-molding the preform in a heat-softened state. The lens surface of the optical element molded by precision press molding does not require post-processing such as grinding and polishing, and can form a desired shape with high precision. It is excellent in that it can be molded with high precision.

  The preforming material is made of, for example, a synthetic resin material such as polyolefin resin or acrylic resin, and includes a lens forming surface and a flange portion provided on an outer edge of the lens forming surface as shown in Patent Document 1 below. May be injection molded. In the injection molding of the preformed material, first, the molten material is injected and filled into the cavity of the injection mold having the surface shape required for the lens forming surface of the preformed material through the gate on the side surface of the mold. Then, the melted material in the cavity is cooled and cured in a state where a predetermined mold clamping force is applied from the molding die, so that a preform material having a predetermined shape is formed. Furthermore, since the preform material after cooling and hardening is integrated with the material (gate portion) filled in the gate via the flange portion, it is separated using a cutting means such as a nipper. Here, for example, a part of the flange part including the gate part is cut off and separated from the preforming material.

JP 2004-188972 A

  In the conventional optical element molding method, an optical element molded product is molded by press-molding the separated preformed material placed on a press mold and heat-softened. However, when a part of the flange portion including the gate portion is cut off at the time of separation, there may be a shape deviation in the preform material before press forming. And when the preforming material in such a state is press-molded, the press pressure acting on the preforming material from the press mold tends to be non-uniform. As a result, in an optical element molded product obtained by press molding, density deviation and shape deviation easily occur due to thermoplastic deformation, and aberration due to anisotropy of the lens surface occurs, resulting in inferior optical performance. Has occurred. In particular, in order to satisfy the performance requirements of a high numerical aperture lens, it is necessary to make the radius of curvature of the lens surface smaller (increase the surface curvature), and therefore aberrations due to the anisotropy of the lens surface may be noticeably generated. It was a problem.

  The present invention has been made in view of the above problems, and its purpose is to suppress performance deterioration due to anisotropy such as density deviation and shape deviation of an optical element molded product caused by a shape deviation of a preforming material. Another object of the present invention is to provide a new and improved optical element molding method.

  According to the first aspect of the present invention, a first molding material is formed by injection molding a preforming material comprising a lens forming surface and a flange portion provided at an outer edge of the lens forming surface, and a gate portion protruding from one end of the flange portion. And cutting one end of the flange portion including the gate portion as a cut portion, and using the other end of the flange portion as a shape compensating portion so that the shape of the flange portion is axisymmetric with respect to the optical axis of the lens forming surface. Provided is an optical element molding method including a second step of cutting, and a third step of molding an optical element molded product by press molding the preformed material molded in the second step in a heat-softened state. Is done.

  According to this optical element molding method, in the first step, the melted material is injected and filled into the injection mold through the gate, and is cooled and cured in a state where a predetermined clamping force is applied, so that the preformed material is obtained. Is injection molded. Here, the material (gate part) with which the gate was filled is projected integrally at one end of the flange part. In the second step, one end of the flange portion including the gate portion is cut as a cut portion, and the other end of the flange portion is cut as a shape compensation portion. Here, the shape compensator is formed so that the shape of the flange portion is axisymmetric with respect to the optical axis of the lens forming surface. In the third step, the preforming material molded in the second step is press-molded in a heat-softened state, and an optical element molded product is molded. Thus, since the shape compensation portion is formed, the shape deviation generated in the preform material is suppressed, and the press pressure acting on the preform material from the press mold is likely to be uniform. As a result, in optical element molded products obtained by press molding, anisotropy such as density deviation and shape deviation due to thermoplastic deformation is unlikely to occur, and aberration is caused due to anisotropy of the lens surface. The problem of poor performance is less likely to occur.

  According to the second aspect of the present invention, the lens includes a lens forming surface and a flange portion provided on the outer edge of the lens forming surface, the gate portion protrudes from one end of the flange portion, and the shape compensation is performed at the other end of the flange portion. A gate portion and a flange portion at one end of the flange portion so that the shape of the flange portion is axisymmetric with respect to the optical axis of the lens forming surface; A second step of cutting at least a part of the cut portion as a cut portion, and a third step of forming an optical element molded article by press-molding the preformed material molded in the second step in a heat-softened state, An optical element molding method is provided.

  According to this optical element molding method, in the first step, the melted material is injected and filled into the injection mold through the gate, and is cooled and cured in a state where a predetermined clamping force is applied, so that the preformed material is obtained. Is injection molded. Here, a material (gate part) filled in the gate is integrally projected at one end of the flange part, and a shape compensating part is provided in advance at the other end of the flange part. In the second step, at least a part of the gate part and the flange part is excised as an excision part. Here, the cut portion is formed such that the shape of the flange portion is axially symmetric with respect to the optical axis of the lens forming surface. In the third step, the preforming material molded in the second step is press-molded in a heat-softened state, and an optical element molded product is molded. Thus, since the shape compensation portion is formed, the shape deviation generated in the preform material is suppressed, and the press pressure acting on the preform material from the press mold is likely to be uniform. As a result, in an optical element molded product obtained by press molding, anisotropy such as density deviation and shape deviation due to thermoplastic deformation is difficult to occur, and aberration occurs due to anisotropy of the lens surface. The problem of poor performance is less likely to occur. Further, since the shape compensation portion is formed in advance by injection molding, it is not necessary to cut off the other end of the flange portion during press molding.

  As described above, according to the present invention, there is provided an optical element molding method capable of suppressing performance deterioration due to anisotropy such as density deviation and shape deviation of an optical element molded product caused by a shape deviation of a preformed material. can do.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
First, an optical element molding method according to the first embodiment of the present invention will be described.

  According to the optical element molding method according to the first embodiment of the present invention, first, in the first step, the lens forming surface includes a lens forming surface and a flange portion provided on the outer edge of the lens forming surface. A preforming material that protrudes from the gate portion is injection-molded. Next, in the second step, one end of the flange portion including the gate portion is cut out as a cut-out portion, and the flange portion other than the flange portion is formed so that the shape of the flange portion is axisymmetric with respect to the optical axis of the lens forming surface. The end is cut off as a shape compensation part. Further, in the third step, the optical element molded product is molded by press molding the preformed material molded in the second step in a heat-softened state.

  In the following, “preliminary material” is also referred to as “preform”. The preform is obtained by preforming a molding material into a shape such as a spherical shape, a biconvex curved surface shape, a disk shape, or a cylindrical shape. Usually, it is desirable that the preform has a shape close to the shape of the optical element molded product (lens molded product) to be obtained, from the viewpoint of ease of precision press molding.

  First, an optical lens molding method according to an embodiment of the present invention will be described. FIG. 1 shows an outline of injection molding of a preform according to this embodiment, and FIG. 2 shows an outline of a precision press molding apparatus for optical lens molding.

  First, in the first step, for example, an injection molding apparatus 400 as shown in FIG. 1 is used. In the injection molding apparatus 400 used for preform injection molding, for example, a cavity 412 of an injection mold 410 having a surface shape required for the lens forming surface 120 of the preform 100 is provided on the side surface of the injection mold 410. The melted material is injected (a) and filled (b) from the gate 414 formed. Here, since the predetermined mold clamping force and the filling pressure from the gate 414 act from the injection molding die 410 to the molten material in the cavity 412, a preform having a predetermined shape is formed by cooling and curing the molten material. .

  Accordingly, in the first step, for example, as shown in FIG. 2, a preform 100 including a substantially convex lens forming surface 120 and a flange portion 110 provided on the outer edge of the lens forming surface 120 is formed. . The lens forming surface 120 of the preform 100 is molded such that the angle between the normal line of the lens forming surface 120 and the optical axis XX ′ is equal to or greater than a predetermined angle θ1 (for example, 60 °). Compared to θ2 of the lens surface 170 of the lens molded product 150, the radius of curvature may be small (surface curvature is large), and a curved surface with a sharp curve may be formed (see FIG. 4B). In addition, since the shape of the preform 100 molded in the first step shrinks after cooling and hardening, an injection mold 310 designed in advance so as to compensate for the shrinkage is generally used.

  Next, in the second step, as will be described in detail later, the preform 100 integrated with the material (gate portion 130) filled in the gate 414 via the flange portion 110 is used as a cutting means such as nippers. Used to separate.

  Further, in the third step, for example, a precision press molding apparatus 300 as shown in FIG. 2 is used. Here, the precision press molding apparatus 300 is disposed, for example, on the outer periphery of the press mold 310, the barrel mold 320, the support portion 350 and the support base 340, the sealed tube 370 for accommodating them, and the sealed tube 370. A thermocouple 380 is included. Here, the press mold 310 includes a pair of an upper die 312 and a lower die 314, and is provided with an optical function transfer portion 316 having an optical function transfer surface formed on at least one of them, and the flange portion 110 of the preform 100. Is provided with a flange support portion 318.

  In the precision press molding apparatus 300, for example, the preform 100 is placed between a pair of press molds 310, and the thermocouple 380 of the heating apparatus and the like are maintained in a state where the inside of the sealed tube 370 is maintained in an atmosphere of a predetermined gas configuration. Is energized to heat the inside of the sealed tube 370. Then, in a state where the internal temperature of the press mold 310 is set to a predetermined temperature exceeding the yield point of the material, for example, the glass transition temperature + approximately 20 ° C., the press member 330 is lowered and the upper mold 312 is pressed to press. The preform 100 placed in the mold 310 is press-molded. Further, after the press molding, the molding pressure is lowered and the preform 100 is brought into contact with the press mold 310 and gradually cooled to a predetermined temperature below the glass transition temperature of the preform material, and then rapidly cooled to room temperature. Remove from the press mold 310.

  In the third step, for example, a press mold 310 having an optical function transfer portion 316 having a radius of curvature R2 larger than the radius of curvature R1 of the lens forming surface 120 of the preform 100 and having an optical function transfer surface formed thereon. The optical function transfer surface is transferred to the lens forming surface 120 of the preform 100 by placing the preform 100 and press-molding the preform 100 in a heated and softened state. Here, the optical function transfer unit 316 of the press mold 310 is configured so that the lens forming surface 120 of the preform 100 placed on the press mold 310 is accompanied by a high-precision optical function surface and the lens of the lens molded product 150. The surface is designed with high accuracy so that the surface 170 can be formed into a desired shape.

  By the way, in the conventional optical lens molding method, the lens preform 250 is molded by press-molding the separated preform 200 placed on the press mold 310 and softened by heating. . However, since part of the flange portion 210 including the gate portion 230 is cut off at the time of separation, a shape deviation occurs in the preform 200. Therefore, when the preform 200 in such a state is press-molded, the press-molding die The press pressure acting on the preform 200 from 310 tends to be uneven. Accordingly, in the preform after press molding, that is, the lens molded product 250, density deviation and shape deviation easily occur due to thermoplastic deformation, and aberration due to anisotropy of the lens surface 270 is generated, so that lens molding is performed. There was a problem that the optical performance of the product 250 was inferior. In particular, in order to satisfy the performance requirements of a high numerical aperture lens, it is necessary to make the radius of curvature of the lens surface 270 smaller (increase the surface curvature), so that aberrations due to the anisotropy of the lens surface 270 are prominently generated. That was a problem.

  The aberration refers to a deviation from ideal image formation in the optical system. For example, ideal image formation is "a point object creates a point image", "a plane object perpendicular to the optical axis creates a plane image", "a figure on a plane perpendicular to the optical axis is similar to it A state that satisfies the three conditions of “creating a figure of a simple image” is referred to. The aberration includes the following five types of monochromatic aberrations mainly due to the shape of the lens, that is, Seidel's five aberrations called spherical aberration, coma aberration, astigmatism, field curvature, and distortion. It is. Here, since the aberration fluctuates in proportion to the numerical aperture and the factorial of the field of view, it is particularly noticeable in a high numerical aperture lens.

  On the other hand, the optical lens molding method according to the present embodiment includes a step (second step) of compensating for a shape deviation generated in the preform 100 before press molding at the time of separation, so that the preform 150 after press molding is included. It is possible to suppress the occurrence of density deviation and shape deviation associated with thermoplastic deformation.

  FIG. 3 is a view showing a preform and a preform molding method (first and second steps) according to the present embodiment, and FIG. 3 (a) shows the shape of the preform formed by injection molding, and FIG. ) To (d) show the forming methods.

  As shown in FIG. 3A, the preform 100 includes a lens forming surface 120 and a flange portion 110 provided on the outer edge of the lens forming surface 120. The lens forming surface 120 has, for example, a disk shape and functions as the lens surface 170 in the lens molded product 150. The flange 110 is formed integrally with the lens forming surface 120, and the lens molded product 150 itself is an optical device. It is used for attaching to a lens holding part or the like. In the preform 100 shown in FIG. 3A, the flange portion 110 is formed in an annular shape on the outer edge of the lens forming surface 120. However, for example, it may be formed on a part of the outer edge.

  As shown in FIG. 3A, a cutout portion 112 is formed at one end of the outer edge of the flange portion 110. The cut portion 112 is formed by cutting off one end of the flange portion 110 together with the gate portion 130 at the time of separation. Here, as shown in FIG. 3A, the cut portion 112 is preferably formed by cutting one end of the flange portion 110 obliquely with respect to the optical axis X-X ′. Thereby, since the shape of the upper surface or the lower surface of the flange portion 110 is maintained in the separated preform 100, the lens molded product 150 is attached to the lens holding portion or the like through the portion where the shape is maintained. Can be done.

  In addition, as shown in FIG. 3A, a shape compensating portion 114 is formed at the other end of the outer edge of the flange portion 110. The shape compensator 114 is formed by cutting away the other end of the flange 110 so that the shape of the flange 110 is symmetric with respect to the optical axis X-X ′ of the lens forming surface 120.

  In forming the preform 100, first, as shown in FIG. 3B, a molded product that does not include the cut portion 112 and the shape compensating portion 114 in the flange portion 110 is formed. For example, as shown in FIG. 1, an injection mold 410 having a surface shape required for the lens forming surface 120 of the preform 100 is prepared, and a molten material is injected and filled from the gate 414 into the cavity 412 of the mold 410. Then, after the mold is clamped, the preform 100 is molded by cooling and curing. In the preform 100 after cooling and hardening, a gate portion 130 is integrally formed at one end of the outer edge of the flange portion 110.

  Then, as shown in FIG. 3C, the preform 100 is separated by cutting off one end of the flange portion 110. At the time of separation, a part of one end of the flange portion 110 is cut out together with the gate portion 130 using a cutting means such as a nipper. By cutting off, a cut portion 112 is formed at one end of the flange portion 110 of the preform 100.

  Furthermore, as shown in FIG. 3D, the other end of the flange portion 110 is shaped-compensated 114 so that the shape of the flange portion 110 is axisymmetric with respect to the optical axis XX ′ of the lens forming surface 120. As excised. In the method of forming the preform 100, the cut portion 112 and the shape compensation portion 114 may be formed at the same time.

  FIG. 4 is a diagram showing a molding method (third step) of a lens molded product according to the present embodiment in comparison with a conventional molding method, and FIG. 4 (A) is a conventional molding method, and FIG. B) shows the forming method according to this embodiment.

  First, a conventional molding method of the lens molded product 250 will be described with reference to FIG. FIGS. 4A and 4A show a preform 200 formed by an injection molding apparatus 400 as shown in FIG. 1, for example. Here, the injection-molded preform 200 is accompanied by a shape deviation in which the shape of both ends of the flange portion 210 is different due to the cut portion 212 being formed at one end of the flange portion 210 when being separated.

  FIGS. 4A and 4B show a state where the preform 200 is placed on a press mold 310 and press-molded in a heat-softened state. Here, since the optical function transfer portion 316 of the lower mold 314 has a radius of curvature larger than the curvature radius of the lens formation surface 220 of the preform 200, the lens formation surface 220 of the preform 200 and the optical function transfer portion of the lower mold 314. A predetermined clearance is ensured between 316 and 316. A similar clearance is secured between both ends of the flange portion 220 and the body mold 320. Further, the lower surface of the flange portion 220 is supported by abutting against a contact surface of a flange support portion 318 formed on the lower mold 314.

  When the preform 200 in this state is pressed by the upper mold 312, for example, the upper flat surface of the preform 200 is pressed by the upper mold 312. Here, the flatness of the pressurizing surfaces of the preform 200 and the upper mold 312 that are in contact with each other, and the molding accuracy including the placement accuracy of the preform 200 and the installation accuracy of the molding die 310 are ensured. If the reform 200 is not accompanied by a shape deviation other than the formation of the cut portion 212, a uniform press pressure P acts on the pressure surface of the preform 200. Thereby, in the preform 200 in the heat-softened state, thermoplastic deformation due to the press pressure P occurs.

  4A and 4B conceptually show the direction of occurrence of thermoplastic deformation assumed in each part of the preform 200. The lens forming surface 220 is deformed so as to fill a clearance with the optical function transfer unit 316. Further, both ends of the flange portion 210 are compressed between the contact surface of the flange support portion 318 and the upper die 312, thereby reducing the member thickness (height in the axis XX ′ direction) and A deformation that expands to the edge side occurs. Here, at one end of the flange portion 210 where the cut portion 212 is formed, for example, a downward deformation is likely to occur at the tip portion where the member thickness is small. On the other hand, since the member thickness is substantially the same at the other end of the flange portion 210, a change similar to that at one end of the flange portion 210 is unlikely to occur. However, for example, if the extension of the flange portion 210 to the outer edge side does not fit within the clearance secured between the flange portion 210 and the barrel mold 320, the lens forming surface 220 is formed at the boundary portion between the flange portion 210 and the lens forming surface 220. The region A having a relatively high filling property (high density) as compared with other portions is formed. Note that the above description only shows one cause when the density deviation occurs, and is not limited to the case where the occurrence factor is applied.

  4A and 4C show the preform 200 'when the thermoplastic deformation by press molding is substantially completed. The preform 200 ′ undergoes thermoplastic deformation due to the press pressure acting on the outer edge from the mold 310. Here, due to the shape deviation at the time of injection molding that the shapes of both ends of the flange portion 210 are different, other portions of the lens forming surface 220 ′ at the boundary portion between the flange portion 210 ′ and the lens forming surface 220 ′. A region A having a relatively high filling property (high density) is generated.

  4A and 4D show a lens molded product 250 obtained by removing the preform 200 ′ after press molding from the mold 310. Since the lens molded product 250 molded by such a conventional molding method is accompanied by a density deviation accompanying the thermoplastic deformation, an aberration due to the anisotropy of the lens surface 270 occurs.

  Next, a molding method (third step) of the lens molded product 250 according to the present embodiment will be described with reference to FIG. In addition, about the matter which becomes substantially the same as the conventional shaping | molding method, in order to avoid duplication description, description is abbreviate | omitted.

  FIGS. 4B and 4A show a preform 100 molded by an injection molding apparatus 400 as shown in FIG. 1, for example. Here, in the injection-molded preform 100 according to the present embodiment, the cut portion 112 is formed at one end of the flange portion 110 and the shape compensation is performed at the other end of the flange portion 110 in the second step. By forming the portion 114, the shapes of both ends of the flange portion 110 are substantially the same, and there is almost no shape deviation.

  For example, when the preform 100 according to this embodiment is pressed by the upper mold 312, the upper flat surface of the preform 100 is pressed by the upper mold 312. Here, if the flatness of the pressurizing surface where the preform 100 and the upper mold 312 are in contact with each other, and the molding accuracy including the placement accuracy of the preform 100 and the installation accuracy of the molding die 310 are secured, the preform can be obtained. Since 100 has almost no shape deviation, a uniform press pressure P acts on the pressure surface of the preform 100. Thereby, in the preform 100 in the heat-softened state, thermoplastic deformation due to the press pressure accompanying the press pressure P occurs.

  4B and 4B conceptually show the direction of occurrence of thermoplastic deformation assumed in each portion of the preform 100. FIG. The lens forming surface 120 is deformed so as to fill a clearance with the optical function transfer unit 316. Further, both ends of the flange portion 110 are compressed between the contact surface of the flange support portion 318 and the upper die 312, thereby reducing the member thickness (height in the axis XX ′ direction) A deformation that expands to the edge side occurs. Here, since there is no shape deviation at both ends of the flange portion 110, a uniform change is likely to occur. As a result, as described with respect to the conventional molding method, the boundary portion between the flange portion 110 and the lens forming surface 120 has a relatively high filling property (high density) compared to other portions of the lens forming surface 120. ) Generation of a region can be suppressed.

  FIGS. 4B and 4C show the preform 110 ′ when the thermoplastic deformation by press molding is substantially completed. The preform 100 ′ undergoes thermoplastic deformation due to the press pressure acting on the outer edge from the mold 310. Here, since the preform 100 after the injection molding has almost no shape deviation, the preform 100 ′ after the press molding does not have a region having relatively different filling properties.

  FIGS. 4B and 4D show a lens molded product 150 obtained by removing the preform 100 ′ after press molding from the mold 310. Since the lens molded product 150 molded by the molding method according to this embodiment is hardly accompanied by a density deviation due to thermoplastic deformation, the occurrence of aberration due to the anisotropy of the lens surface 170 can be suppressed.

  In the above description, the case where the anisotropy of the lens surface 170 occurs due to the density deviation associated with the thermoplastic deformation during press molding has been described. However, the cause of the anisotropy is not limited to the density deviation. For example, when considering the case where one end of the flange portion 110 is cut out by a predetermined amount or more at the time of separation, a low filling density region (low density) occurs in the preform 100 ′ after press molding, and a desired lens forming surface is formed. It is also conceivable that the lens molded product 150 has a shape deviation because 120 ′ (lens surface 170) is not formed. Even in such a case, if the shape deviation of the preform 100 before press molding can be removed as much as possible, the shape deviation of the lens molded product 150 can be suppressed.

(Second Embodiment)
Next, an optical element molding method according to the second embodiment of the present invention will be described. For example, the outline of the injection molding of the preform shown in FIG. 1 and the outline of the precision press molding apparatus for molding the optical lens shown in FIG. 2 are substantially the same as those in the first embodiment. In order to avoid duplication of explanation, explanation is omitted.

  According to the optical element molding method according to the second embodiment of the present invention, first, in the first step, a lens forming surface and a flange portion provided on the outer edge of the lens forming surface are formed, and one end of the flange portion is provided. A preforming material that protrudes from the gate portion and is previously provided with a shape compensation portion at the other end of the flange portion is injection-molded. Next, in the second step, at least a part of the gate portion and the flange portion is cut as a cut portion at one end of the flange portion so that the shape of the flange portion is axisymmetric with respect to the optical axis of the lens forming surface. The Further, in the third step, the optical element molded product is molded by press molding the preformed material molded in the second step in a heat-softened state.

  FIG. 5 is a diagram showing an example of a preform and a preform molding method (first and second steps) according to the present embodiment, and FIG. 5 (a) shows the shape of an injection molded preform, FIG. (B)-(c) shows a shaping | molding method to each.

  5A, the preform 100a is configured by forming a flange portion 110a on the outer edge of the lens forming surface 120a, like the preform 100 according to the first embodiment described above. As shown in FIG. 5A, a part of the gate portion 130a remains as a gate remaining portion 112a at one end of the outer edge of the flange portion 110a. The gate remaining portion 112a is formed by leaving a part of one end of the gate portion 130a remaining without being cut off.

  Further, as shown in FIG. 5A, a convex shape compensating portion 114a is formed at the other end of the outer edge of the flange portion 100a. The shape compensating part 114a is projected and formed at the other end of the flange part 110a so that the shape of the flange part 110a is axisymmetric with respect to the optical axis X-X 'of the lens forming surface 120a.

  When forming the preform 100a, first, as shown in FIG. 5B, a molded product in which a convex shape compensating portion 114a is provided in advance at the other end of the flange portion 110a is formed. For example, after an injection mold 310a having a surface shape required for the lens forming surface 120a of the preform 110a is prepared, and after a molten material is injected and filled from the gate 414 into the cavity 312a of the mold 310a, the mold is clamped. The preform 100a is molded by being cooled and cured. Here, the mold 310a includes a lens forming surface 120a and a flange portion 110a of the preform 100a, and a portion for forming a convex shape compensating portion 114a at the other end of the outer edge of the flange portion 110a. In the preform 110a after cooling and hardening, a gate portion 130a is integrally formed at one end of the outer edge of the flange portion 110a.

  Then, as shown in FIG. 5 (c), the preform 100a is cut off by cutting off a part of the gate portion 130a at one end of the flange portion 110a. At the time of separation, a part of one end of the gate part 130a is cut off from the other part of the gate part 130a using a cutting means such as a nipper. By the separation, a gate remaining portion 112a is formed at one end of the flange portion 110a of the preform 100a. Here, the gate remaining portion 112a is formed by cutting a part of the gate portion 130a so that the shape of the flange portion 110a is axisymmetric with respect to the optical axis XX ′ of the lens forming surface 120a. The

  FIG. 6 is a view showing another example of the preform molding method (first and second steps) according to the present embodiment. FIG. 6 (a) shows the shape of the preform formed by injection molding, and FIG. ) To (c) show molding methods. In addition, according to the shaping | molding method of this example, as shown to Fig.6 (a), the preform similar to the preform shown to Fig.3 (a) can be shape | molded.

  In forming the preform 100b, first, as shown in FIG. 6B, a molded product in which a concave shape compensating portion 114b is provided in advance at the other end of the flange portion 110b is formed. For example, after an injection mold 410b having a surface shape required for the lens forming surface 120b of the preform 100b is prepared, and after a molten material is injected and filled from the gate 414b into the cavity 412b of the mold 410b, the mold is clamped. The preform 100b is formed by being cooled and cured. Here, the mold 410b includes a lens forming surface 120b of the preform 100b and a flange portion 110b, and a portion for forming a concave shape compensating portion 114b at the other end of the outer edge of the flange portion 110b. In the preform 100b after cooling and hardening, a gate portion 130b is integrally formed at one end of the outer edge of the flange portion 110b.

  Then, as shown in FIG. 6C, the preform 100b is cut off by cutting off part of the flange portion 110b together with the gate portion 414b at one end of the flange portion 110b. At the time of separation, a part of one end of the flange portion 110b is cut off from the flange portion 110b using a cutting means such as a nipper together with the gate portion 130b. By cutting off, a cut portion 112b is formed at one end of the flange portion 110b of the preform 100b. Here, a part of the flange part 110b is cut off together with the gate part 130b so that the shape of the flange part 110b is axisymmetric with respect to the optical axis XX ′ of the lens forming surface 120b. Formed with.

  Note that the molding method (third step) of the lens molded products 150a and 150b according to the present embodiment is provided in the flange portions 110a and 110b as compared with the molding method according to the first embodiment described above. The structure of the gate remaining portion 112a or the cut portion 112b and the shape compensating portions 114a and 114b is different. However, since the action state of the press pressure P at the time of press forming and the phenomenon at the time of thermoplastic deformation are conceptually almost the same, the description is omitted to avoid redundant description.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, this invention is not limited to the example which concerns. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs to.

  In the above embodiment, the cut portions 112 and 112b or the gate remaining portion 112a and the shape compensating portions 114, 114a and 114b are formed at one end and one end of the flange portions 110, 110a and 110b, respectively. Although described, application of the present invention is not limited to such a case. That is, in the present invention, within the range in which the flange portions 110, 110 a, 110 b are formed so as to be an axial object with respect to the optical axis XX ′ of the lens forming surfaces 120, 120 a, 120 b, for example, the cutout portion 112. 112b or the remaining gate portion 112a and the shape compensating portions 114, 114a, 114b can be applied as a forming method when formed at two or more locations on one end and the other end of the flange portions 110, 110a, 110b.

  In the above embodiment, the case where the preforms 100, 100a, and 100b are arranged on the lower mold 314 of the press mold 310 and pressed by the movable upper mold 312 has been described. However, the present invention is applied. The present invention is not limited to the case, and for example, it can be applied as a molding method in the case of pressing with a movable lower mold 314 or movable upper and lower molds 312 and 314.

  In the above embodiment, the optical function transfer surface formed on the optical function transfer portion 316 of the lower mold 314 of the press mold 310 is transferred to the lens forming surfaces 120, 120a, 120b of the preforms 100, 100a, 100b. However, application of the present invention is not limited to such a case. That is, the present invention is formed, for example, on the optical function transfer surface formed on the optical function transfer portion 216 ′ of the upper mold 212 or on the optical function transfer portions 216, 216 ′ of both the upper mold 212 and the lower mold 214. It can also be applied as a molding method when the optical function transfer surface is transferred to the lens forming surfaces 120, 120a, 120b of the preforms 100, 100a, 100b.

It is a figure which shows the outline of injection molding of the preform which concerns on embodiment of this invention. It is a figure which shows the outline of the precision press molding apparatus for optical lens shaping | molding which concerns on embodiment of this invention. It is a figure which shows the shaping | molding method of the preform which concerns on the 1st Embodiment of this invention, and a preform. It is a figure which shows the shaping | molding method of the lens molded product which concerns on the 1st Embodiment of this invention in contrast with the conventional shaping | molding method. It is a figure which shows an example of the shaping | molding method of the preform which concerns on the 2nd Embodiment of this invention, and a preform. It is a figure which shows the other example of the shaping | molding method of the preform which concerns on the 2nd Embodiment of this invention, and a preform.

Explanation of symbols

100, 100a, 100b Preform 110, 110a, 110b Flange part 112, 112b Cut part 112a Gate remaining part 114, 114a, 114b Shape compensation part 120, 120a, 120b Lens forming surface 130, 130a, 130b Gate part 150, 150a, 150b Lens molded product

Claims (2)

An optical element molding method for press molding an injection molded preform material,
A first step of injection molding the preforming material comprising a lens forming surface and a flange portion provided on an outer edge of the lens forming surface, and a gate portion protruding from one end of the flange portion;
One end of the flange portion including the gate portion is cut as a cut portion, and the other end of the flange portion is shaped-compensated so that the shape of the flange portion is axisymmetric with respect to the optical axis of the lens forming surface A second step of cutting as
A third step of molding the optical element molded article by press molding in a state where the preforming material molded in the second step is softened by heating;
An optical element molding method comprising: An optical element molding method for press molding an injection molded preform material,
The spare comprising: a lens forming surface and a flange portion provided on an outer edge of the lens forming surface, wherein a gate portion projects from one end of the flange portion, and a shape compensation portion is provided in advance at the other end of the flange portion. A first step of injection molding a molding material;
A second step of cutting off at least a part of the gate portion and the flange portion at one end of the flange portion so that the shape of the flange portion is axisymmetric with respect to the optical axis of the lens forming surface; When,
A third step of molding the optical element molded article by press molding in a state where the preforming material molded in the second step is softened by heating;
An optical element molding method comprising:

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