JP2005161849A - Mold for molding optical element, optical element molding method and optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that though the conventional simultaneous molding of optical elements such as a plurality of lenses by an injection molding method is suitable for mass production because their molded optical elements have the same optical characteristics, but in the case of the limited production of diversified elements, for example, when a required optical characteristic is composed of a group lens, a plurality of expensive molds for molding such elements are needed. <P>SOLUTION: In a plurality of cavities of the mold for molding the optical element, the shape different optical formation faces are formed to simultaneously mold the optical elements having at least two different optical characteristics. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a molding die, a molding method, and an optical element for high-precision optical elements such as lenses, prisms, and mirrors used in optical equipment such as a digital video disk player.

  Conventionally, as a method for molding an optical element such as a lens used in an optical device, as disclosed in Patent Document 1, resin pellets, which are molding materials for the optical element, are heated and kneaded and melted, and this is molded. There is an injection molding method in which molding is performed by injection filling into a cavity formed in the above.

  An optical element obtained by a general conventional mold and molding method will be described below with reference to FIGS.

  FIG. 7 is a schematic cross-sectional view of an injection molding machine that simultaneously molds a plurality of optical elements by an injection molding method. 15 is a hopper, 16 is a molding material made of resin pellets, 17 is an injection cylinder, 18 is a heating cylinder, 19 is a screw, 20 is a nozzle, 21 is a fixed die plate, 22 is a movable die plate, 23 is a clamping cylinder, 5 is a fixed-side optical element mold, 10 is a movable-side optical element mold, 4 is a sprue, 3 is a runner, 2 is a gate, and 1 is an optical element being molded.

  First, the molding material 16 is put into the hopper 15, and the molding material 16 moves in the direction of the nozzle 20 as the screw 19 rotates. The molding material 16 is heated and kneaded and melted by the screw 19 and the heating cylinder 18. Then, the nozzle 20 passes through the sprue 4, the runner 3, and the gate 2, and is injected and filled into the cavities of the optical element molds 5 and 10 on which the necessary optical forming surfaces are formed. The optical element molds 5, 10 are set to a predetermined temperature, for example, near the deflection temperature under load of the molding material 16, and when the optical element 1 is molded, cooled, and ready for removal, the optical element mold 10 Is opened, gate cut is performed, the sprue 4, the runner 3, and the gate 2 are separated, and the molded optical element 1 is taken out.

FIG. 8A is a schematic top view of a molded product 30 in which six optical elements having the same optical characteristics are molded by the above-described injection molding method, and FIG. 8B is a schematic cross-sectional view thereof. 4 is a sprue, 3 is a runner extending radially from the sprue 4, 2 is a gate at the tip of each runner 3, and 1 is an optical element formed radially at the tip of each gate 2.
JP-A-5-177725

  A plurality of insert molds are attached to the above-mentioned conventional fixed side and movable side optical element molding dies, and the shape of the cavity and the optical forming surface of each insert mold are the same, so that the injection molding method is used. Since the obtained optical element has the same optical characteristics, that is, one type of optical element, it is suitable for mass production. However, when it is necessary to construct a small amount of other varieties or a combination lens that combines a plurality of lenses as optical characteristics required for optical equipment, for example, it is necessary to prepare a mold for each optical element. It is uneconomical to prepare a plurality of expensive optical element molds. In addition, it takes time and effort to set the mold for each optical element and its injection molding conditions, and to switch the mold for each optical element, resulting in poor equipment availability and work efficiency. The obtained optical element becomes very expensive.

  The present invention solves the above-described conventional problems by simultaneously molding at least two types of optical elements having different optical characteristics.

  According to the present invention, the number of expensive molding dies is reduced and the number of injection molding conditions set is also reduced. Therefore, the production of a combination lens combining a plurality of lenses with a small amount of other types of production and optical characteristics, etc. In addition, there is an advantage that the operating rate and work efficiency of the equipment are improved, and the optical element can be provided at a low cost.

  The injection molding machine in each embodiment described below is the same type as the injection molding machine that simultaneously molds a plurality of optical elements described with reference to FIG. The description is omitted. Moreover, about each component part, such as an optical element shaping | molding die and a molded product, the same code | symbol is attached | subjected about the same component part as a prior art example, and description of the duplication part is abbreviate | omitted.

(Embodiment 1)
First, Embodiment 1 of the present invention will be described with reference to FIGS.

  FIG. 1 is a schematic sectional view of an optical element molding die according to Embodiment 1 of the present invention, and FIG. 2 is a schematic top view of a molded product 30 molded by the injection molding method according to Embodiment 1.

  The optical element forming molds 5 and 10 shown in FIG. 1 are made of pre-hardened steel, stainless steel (S55C, HPM, NAK) or the like, and are attached to recesses or the like formed in the forming molds 5 and 10 to obtain a desired optical surface. As the insert mold (not shown) having an optical forming surface for forming an optical element having the above, a cemented carbide material was used. Needless to say, the optical element molds 5 and 10 may be made of any material other than the materials described above as long as it can be used for injection molding. In addition, the insert type material is made by processing, for example, an electroless nickel-plated surface using stainless steel (STAVAX) as a base material if an optical element having desired optical characteristics can be molded. It may be used as a mold. However, when the strength is considered, it is preferable to use a cemented carbide as the base material. Further, a protective film or the like may be applied to the surface in order to improve releasability and prevent mold oxidation and corrosion.

  The present invention is to mold at least two types of optical elements having different optical characteristics by simultaneous molding, and FIG. 2 shows an example of the molded product 30. Here, the three optical elements 1a are groups having the same optical characteristics, and the other three optical elements 1b are groups having the same optical characteristics. However, the group of optical elements 1a has a smaller diameter and a different volume than the group of optical elements 1b, and has different optical characteristics from the group of optical elements 1b.

  In the molded product 30, 2a and 2b are gates, 3a and 3b are runners, and 4 is a sprue. These are injected into the optical element molds 5 and 10 for molding the optical elements 1a and 1b. The sprue 4 is integrally molded around the passage of the molding material.

  A cavity formed by a plurality of pairs of insert molds provided in the optical element molds 5 and 10 for molding the molded article 30 is a large-diameter cavity 31 for molding the large-diameter optical element 1b, and more than that. A small-diameter cavity 32 for molding the small-diameter optical element 1a is constructed, and these optical forming surfaces are designed and manufactured to form desired optical surfaces on the optical elements 1a and 1b. The volume difference between 31 and 32 is 2: 1.

  In the optical element molds 5 and 10 according to the first embodiment, the cavities 31 and 32 are radially arranged so that six optical elements are molded in one molding process as described above, and the cavity balance is adjusted. For this purpose, cavities having different volumes (different types) are alternately arranged. That is, the reason why the cavities 32 for molding the optical elements 1a having different volumes and the cavities 31 for molding the optical elements 1b are alternately arranged is that the molding material generated when the molding material is filled into the cavities in the optical element molds 5 and 10. Balance of the temperature difference transmitted to the optical element molds 5 and 10 due to the amount difference, and balance of the force to open the optical element molds 5 and 10 with the cavity internal pressure increased by the different filling force of the molding material In addition, the optical element forming molds 5 and 10 are made uniform in the mold closing force so that optical elements having different volumes can be stably formed. The optical elements in the case where the mold shown in this embodiment is used and molding is performed without alternately arranging cavities having different volumes, some optical elements did not obtain desired characteristics, but the volumes are different. The optical elements obtained by alternately forming the cavities were excellent in performance of all the optical elements.

  In the optical element molds 5 and 10, in the simultaneous molding of two types of optical elements having different cavity volumes, in addition to the injection molding conditions such as the injection conditions, filling conditions, holding pressure conditions, molding mold temperature conditions of the molding material, In order to balance the cavities of different volumes, the runner forming portion 5a of the optical element mold 5 is made to be larger than the runner forming portion 5b of the optical element 1b so that the shape of the runner 3a of the optical element 1a having a small cavity is larger. As shown in the figure, it is formed wide in the left-right direction so that the volume difference of the cavity of each optical element 1b with respect to each optical element 1a is absorbed by the increase in the volume of the runner forming portion 5a. Therefore, the runner forming part 5a also serves as a volume difference absorbing part.

  As described above, the means for changing the volume of the runner forming portion is used to change the volume difference between the cavities for molding the optical elements 1a and 1b, and the optical characteristics of the two types of optical elements molded thereby are the best and stable molding. Get the optimal conditions under which is done.

  Next, molding of two types of optical elements using the above-described optical element mold will be described. As the injection molding machine, a conventional general molding machine shown in FIG. 7 is used, and the melted and kneaded molding material is injected and filled into the cavities 31 and 32 of the optical element molding dies 5 and 10 incorporated therein. . As the molding material, a polyolefin-based resin (glass transition point Tg = 150 ° C., heat distortion temperature Tt = 125 ° C.) was used.

  As a result of molding each optical element under conditions that seem to be optimal as injection molding conditions (injection conditions, filling conditions, holding pressure conditions, mold temperature conditions, etc.), the optical characteristics of the optical elements, that is, the respective aberrations are as follows: It became like Table 1. The unit of aberration is mλ, and the optical property evaluation method is to measure the transmitted wavefront aberration (measurement wavelength λ = 632.8 nm) using an interferometer, and to obtain representative optical properties such as astigmatism and coma. Aberration and spherical aberration were confirmed. Each aberration is preferably as small as possible, but here, the standard range of each aberration is set to 35 mλ or less, and good optical characteristics are assumed.

  In Table 1 below, the three optical elements 1a are indicated by 1a-1, 1a-2, and 1a-3, respectively, and the three optical elements 1b are indicated by 1b-1, 1b-2, and 1b-3, respectively. .

  As shown in Table 1, all the aberrations of the optical elements 1a and 1b having two different optical characteristics were able to satisfy the standard.

  When high performance optical characteristics are required, optical elements having different optical characteristics with as little cavity volume difference as possible may be simultaneously molded.

  In the above example, the runner forming portion 5a also serves as a volume difference absorbing portion. However, the gate 2 portion may be provided with a volume difference absorbing portion as long as it is a passage for a molding material.

  Here, as a comparative example of the first embodiment, the runner forming portion 5a is not provided with a volume absorbing portion, that is, the gates 2a, 2b, the runners 3a, 3b, etc. are respectively formed in the same shape and the same two types of cavities as described above. Table 2 below shows the optical characteristics of the optical elements 1a and 1b molded by the above method, that is, the respective aberrations. The optical property evaluation method in this comparative example is the same as that in the first embodiment.

  In Table 2, the three optical elements 1a are indicated by 1a-1, 1a-2, and 1a-3, respectively, and the three optical elements 1b are indicated by 1b-1, 1b-2, and 1b-3, respectively. Yes.

  As apparent from Table 2 above, the group of optical elements 1a satisfies the standards for all aberrations, but the group of optical elements 1b does not meet the standards for all aberrations.

  In this comparative example, by providing a stopper for stopping the inflow of the molding material at each gate portion of the optical element molding die, only the optical element having the same optical characteristics is molded by operating this stopper, or only the necessary optical element. Can be selected and molded.

(Embodiment 2)
Next, a second embodiment will be described with reference to FIGS. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and differences from the first embodiment will be described.

  First, in the molded product 30 shown in FIG. 4, an extending portion 33 that does not affect the optical characteristics of each optical element 1a is integrally provided around each optical element 1a. As shown in FIG. 3, the extending portion 33 is formed by a volume difference absorbing portion 32a in which the diameter of the cavity 32 in the portion that does not affect the optical forming surface is increased in order to absorb the volume difference of the cavity 32 with respect to the volume of the cavity 31. It is the part which was done.

  As described above, by providing the volume difference absorbing portion 32a in the cavity 32, the optical elements 1a and 1b having different optical characteristics can be simultaneously molded as in the first embodiment.

  In addition, since the extension part 33 formed in the optical element 1a does not affect the optical characteristic at all, it may be mounted on the optical apparatus as it is, or may be separated as necessary.

(Embodiment 3)
This Embodiment 3 is demonstrated with reference to the molded article 30 of FIG. In this description, the same components as those in the first embodiment are denoted by the same reference numerals, and different portions will be described.

  In FIG. 5, like the first embodiment, the three optical elements 1a have the same optical characteristics, and the three optical elements 1b have optical characteristics different from those of the optical element 1a. The optical element 1a group and the optical element 1b group have substantially the same shape and volume for the optical elements 1a and 1b, the gates 2a and 2b, and the runners 3a and 3b, respectively. In the optical element molds 5 and 10, the cavities 31, 32, the gate 2, and the runner 3 are formed in substantially the same shape and volume.

  The cavities 31 of the group of optical elements 1a have the same shape of the optical formation surface, and the cavities 32 of the group of optical elements 1b have the same shape of the optical formation surface. However, the shape of the optical formation surface of the cavity 31 of the group of optical elements 1a is different from the shape of the optical formation surface of the cavity 32 of the group of optical elements 1b.

  Even with such a configuration, optical elements having different optical characteristics can be molded simultaneously, the number of expensive molds is reduced, and the number of injection molding conditions set is also reduced. It is most suitable for molding a combination lens that combines a plurality of lenses having different optical characteristics.

  In each of the above-described embodiments, two types of optical elements having different optical characteristics are molded. However, the number is not limited to the above-described number.

(Embodiment 4)
Next, a fourth embodiment will be described with reference to FIG. In the fourth embodiment, for example, in the molding of the optical elements 1a and 1b in the first embodiment, the width of the gate part that affects the optical performance of the optical element is defined. Since it is the same as that of Embodiment 1, this is used and the description is omitted. In the fourth embodiment, as in the first embodiment, the shape of the runner 3a of the small optical element 1a molded with a small cavity is increased so as to balance the cavities of different volumes. As shown in FIG. 1, the runner forming portion 5a is formed wider in the left-right direction than the runner forming portion 5b of the optical element 1b formed with a large cavity, and the volume difference of the cavity of each optical element 1b with respect to each optical element 1a is determined. Absorption is performed by increasing the volume of the runner forming portion 5a. Therefore, the runner forming part 5a also serves as a volume difference absorbing part.

  Further, similarly to the first embodiment, three cavities 31 having the same volume and cavities 32 having the same volume different from each other are radially arranged so that six optical elements are molded, and cavity balance is achieved. In order to achieve this, cavities of different volumes are alternately arranged.

  6 (a) and 6 (b) are plan views showing the shape of a molded body including optical elements 1a and 1b of different sizes formed by the cavities 32 and 31, and each of the optical elements 1a and 1b. The outer diameters are L1 and L2, the widths of the gate portions 2a and 2b are G1 and G2, and the total volume from the outer end of the optical elements 1a and 1b to a predetermined dimension including each gate portion and the runner portion is T1. , T2. The mold was designed so that the volumes T1 and T2 from the outer edges of the optical elements 1a and 1b to the length of the dimension X = 15 mm are substantially the same.

  Using such an optical element mold, three optical elements 1a having a diameter of 4 mm and three optical elements 1b having a diameter of 8 mm are formed with the gate portions 2a and 2b having the same width as that of the first embodiment. Changed and molded. For the optical element 1a (G1 / L1 = K1) having a small outer diameter and the optical element 1b (G2 / L2 = K2) having a large outer diameter, the performance of the optical surface as these optical elements was evaluated by transmission wavefront aberration. As shown in (a) and (b) of Table 3, the non-defective range of optical performance was 0.1 <G / L <0.4 in both the optical element 1a and the optical element 1b.

  As described above, the gate width affects the optical performance of the optical element to be molded, that is, aberration, because the internal pressure of the cavity when the resin molding material is filled into the cavity during molding depends on the size of the gate width. If the gate width is too small with respect to the outer diameter of the optical element, the internal pressure of the cavity becomes too high, whereas if the gate width is too large, the internal pressure of the cavity Is presumably due to the fact that the value becomes too lower than the appropriate value.

  From the above evaluation results, in the molding method for molding optical elements having different volumes at the same time, a volume difference absorbing portion that absorbs the volume difference between the plurality of cavities is provided, and the volume including the sprue and the runner portion is substantially the same volume. In addition, by molding using a mold in which the relationship between the outer diameter L of the optical element and the gate width G is 0.1 <K <0.4, it is possible to obtain a plurality of optical elements having different optical volumes and different optical volumes. it can.

  In the fourth embodiment, two types of optical elements have been studied. However, the present invention is not limited to this, and when three or more types of optical elements having different volumes are simultaneously molded with the same molding die, the molding die can be similarly designed. An optical element with good optical performance can be obtained.

  As described above, since the present invention can simultaneously mold at least two types of optical elements having different optical characteristics, it is possible to produce a small amount of other kinds of products, molding a combination lens combining a plurality of optical elements having different optical characteristics, etc. Ideal for.

1 is a schematic cross-sectional view of an optical element mold according to Embodiment 1 of the present invention. Schematic top view of a molded product in Embodiment 1 of the present invention Schematic cross-sectional view of an optical element mold according to Embodiment 2 of the present invention Schematic top view of a molded product in Embodiment 2 of the present invention Schematic top view of a molded product in Embodiment 3 of the present invention Schematic top view of the molded product in Embodiment 4 of the present invention Schematic cross-sectional view of an injection molding machine used for manufacturing optical elements Schematic top view and schematic cross-sectional view of a conventional molded product

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b Optical element 2a, 2b Gate 3a, 3b Runner 4 Sprue 5, 10 Optical element shaping | molding die 5a Runner formation part (volume difference absorption part)
31, 32 Cavity 32a Volume difference absorption part 33 Extension part

Claims (8)

An optical element molding die for injecting and filling a molding material melted by heating and kneading into a plurality of cavities, and simultaneously molding a plurality of optical elements by an optical forming surface formed in the plurality of cavities. An optical element molding die, wherein the optical forming surface formed in the cavity has at least two types of shapes having different optical characteristics of the optical element formed thereby. An optical element molding die for injecting and filling a molding material melted by heating and kneading into a plurality of cavities, and simultaneously molding a plurality of optical elements by an optical forming surface formed in the plurality of cavities. An optical element molding die characterized in that the cavity has at least two types of shapes having different volumes together with the optical forming surface, and is provided with a volume difference absorbing portion that absorbs the volume difference between the at least two types of cavities. . 3. The optical element according to claim 2, wherein the volume difference absorbing portion is provided in a portion of the plurality of cavities having a smaller volume, which does not affect the optical surface of the optical element molded thereby. Mold. The optical element molding die according to any one of claims 2 to 3, wherein the volume difference absorbing portion is provided in a gate portion or a runner portion adjacent to the gate. 5. The mold for an optical element according to claim 2, wherein cavities having different volumes are alternately arranged. This is an optical element molding method in which a heat-kneaded and melted molding material is injected and filled into a plurality of cavities, and at least two types of optical elements having different optical characteristics are simultaneously molded depending on the optical formation surfaces formed in the plurality of cavities. The method for molding an optical element is characterized in that at least two types of optical elements having different optical characteristics are molded by optical formation surfaces having different shapes formed in a cavity. A molding method in which a heat-kneaded and melted molding material is injected and filled into a plurality of cavities having different volumes, and a plurality of optical elements are simultaneously molded by an optical forming surface formed in the plurality of cavities. The volume difference absorbing part for absorbing the volume difference of each of the cavities is provided so that the volume including the sprue and the runner part is substantially the same volume, and the relationship between the outer diameter L of each optical element and the width G of the gate part is 0.1. <G / L <0.4. A method for molding an optical element, wherein: An optical element molding die according to any one of claims 1 to 5 or an optical element molded by the method for molding an optical element according to claim 6 to at least two types of optical elements having different optical characteristics.

Images