JP2005305797A - Optical element molding mold, optical element molding method, and optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problem: in an optical element molding mold for molding the optical element by injecting a resin molding material into at least two cavities, an insert mold constituting the cavities is produced conventionally by machining stainless steel etc., an expensive precision machine is required especially for non-spherical machining, since machining has to be done individually, machining accuracy, surface roughness, etc., are different to cause the dispersion of properties of the optical elements, and the obtained optical element is made expensive. <P>SOLUTION: The insert mold constituting the mold is manufactured by pressing a vitreous material with a mother mold. Numbers of the insert molds having uniform accuracy can be obtained to be suitable for molding a plurality of the optical elements simultaneously. <P>COPYRIGHT: (C)2006,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 disclosed in Patent Document 1, as one method for molding optical elements such as lenses used in optical equipment, resin pellets, which are molding materials for optical elements, are heat-kneaded and melted, and then molded. There is an injection molding method in which molding is performed by injection filling into a cavity formed by a mold.

  Hereinafter, a general conventional injection molding method and an optical element molded thereby will be described with reference to FIGS.

  FIG. 3 is a schematic cross-sectional view of an injection molding machine that simultaneously molds a plurality of optical elements by an injection molding method. 30 is a hopper, 31 is a resin molding material made of resin pellets, 32 is an injection cylinder, and 33 is a heating cylinder. , 34 is a screw, 35 is a nozzle, 36 is a fixed die plate, 37 is a movable die plate, 38 is a clamping cylinder, 39 is a fixed side optical element mold, 40 is a movable side optical element mold, and 41 is a sprue. , 42 is a runner, 43 is a gate, and 44 is an optical element during molding.

  First, the resin molding material 31 is put into the hopper 30, and the molding material 31 moves in the direction of the nozzle 35 as the screw 34 rotates. The resin molding material 31 is heated and kneaded and melted by the screw 34 and the heating cylinder 33, passes through the sprue 41, the runner 42, and the gate 43 from the nozzle 35, and is attached to the optical element molding dies 39 and 40, respectively. These are injected into a cavity formed by an insert mold (not shown) that forms the necessary optical forming surfaces for each, and is filled. Since the optical element molds 39 and 40 are set at a predetermined temperature, for example, near the deflection temperature under load of the resin molding material 31, the optical element 44 to which the optical forming surface of the insert mold is transferred is molded and cooled. . Then, after this is ready to be taken out, the optical element molding die 40 is retracted by the clamping cylinder 38, the cavity is opened, the molded product is taken out, and gate cutting is performed to obtain the optical element 44.

FIG. 4 is a schematic cross-sectional view of a molded product 45 formed by molding two optical elements 44 having the same optical characteristics by the injection molding method. Reference numeral 41 denotes a sprue, 42 denotes a runner extending from the sprue 41, 43 denotes a gate at the tip of each runner 42, and 44 denotes an optical element formed radially at the tip of each gate 43.
JP-A-5-177725

  Conventionally, an insert die attached to an optical element molding die and having a desired optical forming surface is used by processing a surface of which stainless steel (STAVAX) or the like is subjected to, for example, electroless nickel plating. It is common. From the viewpoint of strength, a cemented carbide may be used as a base material. Further, a protective film or the like is provided on the surface of the optical forming surface in order to improve releasability from the molded product and to prevent mold oxidation and corrosion.

  However, taking advantage of the injection molding method, when trying to mold a plurality of optical elements simultaneously by one injection molding, a plurality of optical elements having the same optical characteristics are molded simultaneously under the same molding conditions. Requires multiple insert molds with uniform processing accuracy, surface roughness, etc., and it is difficult to achieve uniform accuracy by processing them individually from stainless steel or cemented carbide. However, it is necessary to process with an expensive precision processing machine, and at the same time, there is a limit to processing each accuracy uniformly.

  In addition, even if the processing is uniform, it is easy to cause variations in the accuracy of optical elements that are difficult to judge from the processing accuracy. In addition, since many insert molds are manufactured with expensive equipment, the price of the optical elements to be molded from now on will increase. It becomes very expensive.

  The present invention is an optical element molding die for molding an optical element by heat-kneading and melting a molding material and injecting and filling the molding material into a plurality of cavities, and comprising the plurality of cavities and the optical element The insert mold for transferring the optical forming surface is an optical element mold composed of a glass material press-molded by a mother mold, and the conventional problem is solved by molding the optical element by this mold. Is.

  According to the present invention, an insert mold obtained by press-molding a glass material can be produced in a much shorter time than that produced by a processing machine. Therefore, particularly when a large number of optical elements are molded by one injection molding. It is most suitable for the production of multiple insert molds required for And insert molds obtained by press-molding glass materials can produce many molds with uniform shape accuracy using the same master mold, so the price is lower than the insert molds individually produced by conventional processing machines. There is an advantage that an optical element with high accuracy can be provided at low cost. Furthermore, the glass material has an effect that the surface of the optical formation surface is smoother than that of stainless steel or the like formed by a processing machine, and the surface roughness of the optical element is improved.

  Hereinafter, in describing the embodiment of the present invention, the injection molding machine and the optical element molding die are the same type as the injection molding machine shown in FIG. To do. Moreover, since each component of the molded product is the same as the conventional example of FIG. 4, the component is denoted by the same reference numeral and description thereof is omitted.

(Embodiment)
FIG. 1 is a schematic cross-sectional view of an optical element molding die according to an embodiment of the present invention, FIG. 2 (a) is a schematic cross-sectional view during the manufacture of an insert die according to the embodiment, and FIG. It is sectional drawing of the insert type | mold produced by a).

  The optical element molds 39 and 40 shown in FIG. 1 are made of pre-hardened steel, stainless steel (S55C, HPM, NAK) or the like, and a glass material is pressed into the recesses formed in the molds 39 and 40. Insert molds 1a, 1b, 1c, and 1d for forming an optical element having a desired optical surface are fixed, cavity 2 is formed by insert molds 1a and 1c, and insert molds 1b and 1d. Thus, the cavity 3 is formed.

  The production of the insert molds 1a, 1b, 1c, and 1d will be described with reference to FIG. The upper mold 4 and the lower mold 5 are mother molds, and the upper surface of the lower mold 5 is flat. On the lower surface of the upper mold 4, a convex portion 4 a for transferring and forming a required optical forming surface is formed. The body mold 6 regulates the outer diameter of the insert mold obtained by press molding. Between the upper mold 4 and the lower mold 5, a glass material 7 for producing an insert mold is set.

  The insert mold is manufactured by heating the upper mold 4 and the lower mold 5 with the upper and lower heater blocks 8 and 9, and pressurizing the upper mold 4 with the pressure P by the pressure cylinder 10 connected to the heater block 8. The glass material 7 is deformed by the portion 4a to produce, for example, the insert mold 1a shown in FIG.

  The insert mold 1b having the same shape as the insert mold 1a is manufactured using the same mother mold, and the insert mold 1c and insert mold 1d having the same shape are manufactured using the same mother mold.

  Here, the material used for the mother die and the body die is made of cemented carbide, and as an insert-type glass material 7 formed by press molding of the mother die, boric acid-based, phosphorous, which is a general optical glass material, is used. There are acid, lanthanum, and borosilicate. In the present embodiment, borosilicate glass (deflection point At = 553 ° C., glass transition point Tg = 516 ° C.) glass is used.

  Next, the insert molds 1a, 1b, 1c, and 1d produced as described above are fixed to the concave portions of the optical element molds 39 and 40, respectively, as shown in FIG. The molding of optical elements having the same optical performance will be described.

  As the injection molding machine, a general molding machine shown in FIG. 3 is used, and the resin molding material 31 heated and melt-kneaded is injected and filled into the cavities 2 and 3 of the optical element molding dies 39 and 40 incorporated therein. . As the resin molding material 31, a polyolefin resin (glass transition point Tg = 150 ° C., heat distortion temperature Tt = 125 ° C.) was used.

  Then, the optical element 44 is formed in the shape of the molded product 45 shown in FIG. 4 under conditions that seem to be optimal as injection molding conditions, that is, mold temperature = 130 ° C., resin temperature = 250 ° C., injection pressure = 100 MPa, cooling time = 40 sec, and the like. Then, each gate 43 was cut to obtain an optical element 44 onto which the optical forming surfaces of the insert dies 1a, 1b, 1c, and 1d were transferred.

  Table 1 below shows the optical characteristics of the optical element molded by the molding method, that is, each aberration. 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 if it is less than that, good optical characteristics are assumed.

  As shown in Table 1, all the aberrations of the optical elements 44 having the same performance satisfied the standard.

  In the above molding, pre-hardened steel, stainless steel, etc. are listed above as the base material of the optical element molding die other than the insert die made of glass material. For example, thermal expansion and contraction between these and the insert type glass material. In order to prevent the occurrence of burrs, etc. in the molded product due to the difference, and to reduce variations in optical characteristics that are affected by differences in thermal expansion and contraction, etc., the gate part, runner part, insert mold mounting part of the mold, etc. Glass members produced by processing the same glass material as the glass material used for the insert mold by means such as grinding may be attached to the inner wall.

  In addition, the difference in thermal expansion coefficient between the base material constituting the mold and the insert mold creates a clearance between the two during heating, thereby preventing the insert mold from being displaced and causing burrs or the like to occur in the molded optical element. Therefore, by using a glass material with a large thermal expansion coefficient for the glass material used for the insert mold and a material with a small thermal expansion coefficient for the base material of the mold, the difference in the thermal expansion coefficient during heating is increased. A configuration in which the clearance between them is small is desirable.

  Moreover, although the glass material 7 used for the insert mold has a cylindrical shape whose upper and lower surfaces are mirror-finished, it is not limited to this shape. Moreover, although this was heated from normal temperature with the press of the glass material 7, it may be manufactured by first heating up the glass material and then pressing it after it has melted.

  Further, in selecting the glass material 7 of the insert molds 1a to 1d, taking into consideration the linear expansion coefficient and hardness of the optical element 44 with the molding material, the thermal deformation temperature of the glass material is the mold temperature and the melting of the molding material. It is desirable to select a material that is higher than the temperature.

As insert-type glass materials, silicate glass (SiO ₂ glass), borate glass (B ₂ O ₃ glass), borosilicate glass (B ₂ O ₃ —SiO ₂ glass), etc. It may be a crystallized glass material, in which an optical element molded with an insert mold using borosilicate glass has the same characteristics as an optical element molded with an insert mold made of the optical glass material described above Had.

  The present invention provides an optical element molding die for molding an optical element by injection molding a molding material made of a resin, and by forming an insert mold for molding an optical forming surface of the optical element from a glass material by press molding. Therefore, a large number of insert molds with high accuracy can be produced easily and inexpensively, so that it is optimal as a mold for optical elements with high productivity.

Schematic sectional view of an optical element mold according to an embodiment of the present invention (A) is schematic sectional drawing which shows preparation of the insert type | mold in embodiment of this invention, (b) Sectional drawing of the insert type | mold in embodiment of this invention Schematic cross-sectional view of an injection molding machine used for manufacturing optical elements Schematic cross section of molded product

Explanation of symbols

1a, 1b, 1c, 1d Insert mold 2, 3 Cavity 4 Upper mold 5 Lower mold 6 Body mold 7 Glass material 8, 9 Heater block 10 Pressure cylinder 31 Resin molding material 39, 40 Optical element molding mold 41 Sprue 42 Runner 43 Gate 44 optical element

Claims (4)

An optical element molding die for heating and kneading and melting a molding material and injection-filling the molding material into a plurality of cavities to mold an optical element, comprising the plurality of cavities, and an optical forming surface on the optical element An optical element molding die characterized in that the insert die for transferring the material is made of a glass material press-molded by a mother die. 2. The optical element molding die according to claim 1, wherein the insert-type glass material is made of crystallized glass or optical glass material. An optical element characterized in that an optical element is formed by injection-filling a heat-kneaded and melted resin molding material into a plurality of cavities formed in the optical element molding die according to claim 1 or 2. Molding method. An optical element molded by the optical element molding method according to claim 3.

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