JP2008213213A - Mold manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold manufacturing method which enables the molding of a molding surface having a free curved surface with high surface precision. <P>SOLUTION: The mold manufacturing method has the shape forming process of forming the free curved surface to the molding surface of a mold used for molding an optical article having the free curved surface on the molding surface, the plating process of plating the molding surface having the free curved surface formed thereto and the polishing process of polishing the molding surface plated in the plating process. The polishing process is constituted inclusive of an elastomer 6 having a dome part 6A having a hollow dome shape and polishing cloth 7 comprising a cellulose long fiber nonwoven fabric attached so as to cover the dome outer surface of the dome part 6A of the elastomer 6 and a polishing tool 4 wherein a pressure fluid of 0.01-0.02 MPa is injected in the dome part 6A is brought into contact with the plated molding surface to polish the same to manufacture the mold. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a mold, and particularly relates to a method for manufacturing a mold having a free-form surface on a molding surface.

2. Description of the Related Art Conventionally, optical articles such as spectacle lenses and mirrors having an aspheric surface (free curved surface) having a non-rotation axis symmetry or a rotation axis symmetry have been widely used. Such an optical article is manufactured by using a mold in which a free-form surface corresponding to the optical article is formed on the molding surface.
In order to obtain such a free-form surface regardless of the material type of the mold, a creation process for forming a free-form surface on the molding surface of the mold, a plating process for plating the molding surface, and contact with the molding surface There is known a manufacturing method of a mold including a polishing step of polishing using a polishing tool including a hollow dome-shaped elastic body having a polishing member attached to a surface (see, for example, Patent Document 1).

  A holding unit that holds the workpiece; a polishing unit that contacts and polishes the dome-shaped elastic body against the surface of the workpiece; and a driving unit that rotationally drives either the holding unit or the polishing unit; A support unit that supports the other of the holding unit and the polishing unit is provided, and either one of the rotationally driven holding unit or the polishing unit is rotated by the power of one rotation, and the support unit includes a support unit. A polishing apparatus is proposed that can be efficiently polished without breaking the shape of the surface of the workpiece on which a free-form surface is created, to which a rotation restricting portion that restricts the rotation of the workpiece is connected (for example, Patent Document 2). reference).

JP 2005-40977 A JP 2005-169520 A

However, according to the method for manufacturing a mold of Patent Document 1, a molding surface having a certain degree of surface accuracy (shape accuracy and surface roughness) can be obtained, but an optical device having a free-form surface having higher performance optical characteristics. In order to obtain an article, higher surface accuracy is required on the molding surface of the mold.
Then, this invention is made | formed in view of such a situation, and it aims at providing the manufacturing method of the shaping | molding die which can shape | mold the shaping | molding surface provided with the free-form surface with high surface accuracy. .

  In order to solve the above problems, a method for manufacturing a molding die according to the present invention is a method for manufacturing a molding die used for molding an optical article having a free-form surface on a molding surface, wherein the free-form surface is provided on the molding surface. A shape creation step to be formed, a plating step for plating the molding surface on which a free-form surface is formed, and a polishing step for polishing the plated molding surface, the polishing step comprising a hollow dome shape And a polishing tool made of a cellulose non-woven fabric attached so as to cover the outer dome of the hollow dome-shaped elastic body, and abutting the plating tool on the molding surface that is plated It is characterized by polishing.

  According to this mold manufacturing method, a free-form surface is formed in the shape creation process, and a plating process is performed in the plating process to eliminate minute tool marks on the shape creation surface and crystal grain boundaries or crystal steps in the metal material. In the polishing step, a polishing tool including a hollow dome-shaped elastic body and an abrasive cloth made of a long-fiber cellulose non-woven fabric attached so as to cover the outer surface of the hollow dome-shaped elastic body is applied to the molded surface. By polishing in contact with each other, a molding die capable of molding a molding surface having a free curved surface with high surface accuracy is obtained.

Moreover, in the manufacturing method of the shaping | molding die of this invention, it is preferable that the polishing cloth which consists of a cellulose long fiber nonwoven fabric which comprises the said polishing tool is a gauze type provided with the mesh structure.
According to this, the polishing cloth made of the cellulose non-woven fabric constituting the polishing tool is a gauze type having a mesh structure, so that the molding surface (plated film surface) and the polishing tool ( The polishing agent supplied to the polishing cloth) is retained in the mesh structure and cools the heat generated between the plating film surfaces, and the polishing performance is improved by the synergistic action with the polishing agent.

  Moreover, in the manufacturing method of the shaping | molding die of this invention, the pressure fluid of 0.01 Mpa-0.02 Mpa is inject | poured and used for the hollow dome-shaped elastic body which comprises the said polishing tool. preferable.

  According to this, in the polishing step, the polishing tool in which the pressure fluid of 0.01 Mpa to 0.02 Mpa is injected into the hollow dome of the elastic body is abutted against the molding surface subjected to the plating process and polished. Thus, a molding die that can mold a molding surface having a free-form surface with high surface accuracy is obtained. When the pressure is less than 0.01 MPa, when the molded surface subjected to the plating process is polished, the elastic body 6 is not sufficiently stretched and is attached so as to cover the outer surface of the dome-shaped elastic body. Polishing unevenness occurs on the polishing surface (molding surface) without the adhered polishing cloth being in close contact with the molding surface. On the other hand, when the pressure exceeds 0.02 Mpa, waviness occurs on the polished surface.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. This embodiment exemplifies the case of a mold that manufactures an aspherical mirror used in a projector that projects an image as the mold.

  The aspherical mirror used in the projector is disposed between the projection lens of the optical engine and the screen, and has a function of enlarging and displaying the image light emitted from the projection lens on a screen located at a short distance. In such a projector, the image light emitted from the projection lens is obliquely projected onto the convex reflecting surface of the aspherical mirror and displayed in an enlarged manner, and the image light emitted from the projection lens via the light collecting means is displayed. There is a configuration in which an enlarged display is performed by oblique projection onto the concave reflecting surface of the aspherical mirror.

  This embodiment will be described in the case of a molding die used for injection molding a base material for an aspherical mirror that uses a concave surface formed with a non-rotating axisymmetric aspheric surface (free curved surface) as a reflecting surface. To do.

FIG. 1 is a schematic cross-sectional view of a mold base on which a mold is set.
In FIG. 1, the mold base 1 includes a fixed mold 2 and a movable mold 3. The fixed mold 2 includes a fixed mold 21 and a concave mold 22 fitted as a nest in the fixed mold 21. The movable mold 3 includes a movable mold 31 and a convex mold 32 fitted as a nest in the movable mold 31.

The concave mold 22 includes a molding surface 22A on which a free curved surface having a plurality of inflection points corresponding to the aspherical mirror to be molded is generated. On the other hand, the convex mold 32 includes a molding surface 32A formed so as to substantially conform to the shape of the molding surface 22A of the concave mold 22.
In the mold base 1 configured as described above, the space S formed between the molding surface 22A of the concave mold 22 of the fixed mold 2 and the molding surface 32A of the convex mold 32 of the movable mold 3 forms a mold part. Then, the mold part (space S) is filled with the plastic resin, and the aspherical mirror substrate 10 shown later is formed.

First, a method for processing the concave mold 22 will be described. FIG. 2 is a perspective view of the concave mold base 20, and FIG. 3 is a perspective view of the concave mold 22.
The concave mold 22 shown in FIG. 3 is completed by processing the substantially conical concave mold base 20 shown in FIG. 2 and then cutting it into a predetermined outer shape. In addition, the conical surface 20A of the concave mold base 20 is formed with a shape including a molding surface 22A made of a non-rotating axially symmetric aspheric surface (free curved surface) of the concave mold 22. Therefore, hereinafter, the surface 20A may be expressed as a molding surface 20A.

  The concave mold base 20 includes a shape creation step of cutting a metal material to form a molding surface including a free curved surface having a plurality of inflection points, and a base including a molding surface (cutting surface) on which the free curved surface is formed. Processing is performed including a plating step of plating the surface of the material and a polishing step of polishing the plated molding surface (plated coating surface).

  The metal material used for the concave mold base 20 is not limited as long as it is a metal, but in consideration of workability in the shape creation process, soft metal materials such as copper, copper alloy, aluminum, and aluminum alloy are used. Is preferred. In the case of this embodiment, for example, a round bar of an aluminum alloy (AL-Mg alloy 5056B) having a diameter of 250 mm is used.

In the shape creation process, a metal material is cut using a CNC machine that is numerically controlled by a computer, for example, a four-axis control CNC lathe equipped with a machining center, and one surface of the concave mold base 20 is formed. A conical surface (molding surface) 20A including a free-form surface is formed.
Cutting is performed in two steps: rough cutting and finish cutting. In rough cutting, a metal material is cut to form a molding surface including a free curved surface such as a predetermined aspheric coefficient. In the finish cutting process, a precision finish cut is performed on a rough-processed molding surface (cut surface) using a single crystal diamond round blade tool.

  As a specific example of finish cutting, for example, while supplying an ultrafine oil mist in which vegetable oil is mixed with high-pressure air to a cutting point of a workpiece rotating at 5000 rpm, a tip radius of about 2 mm, a rake angle Precision cutting is performed with a 0 ° single crystal diamond round cutting tool at a cutting amount of about 2 μm and a feed rate of about 5 mm / min. The surface accuracy (PV) on the molding surface after finish cutting is about 0.02 μm.

In the shape creation step, an NC milling machine or an aspherical processing machine can be used in addition to the CNC lathe. A preferable example of the aspheric processing machine is ULG100 (trade name, manufactured by Toshiba Machine Co., Ltd.).
Then, the concave mold base 20 that has been subjected to the cutting process moves to a plating step.

In the plating step, a plating process is performed on the entire surface of the concave mold base 20 that has been cut. A preferable plating treatment includes electroless nickel plating.
The electroless nickel-plated coating film is easy to obtain a substantially uniform film thickness, and also provides high adhesion to the substrate, excellent wear resistance, and high corrosion resistance. A known plating method can be used as the electroless nickel plating method. In addition, before the electroless nickel plating, a catalytic treatment with a two-component catalyst solution or the like is performed.

The plating thickness applied to the molding surface (cutting surface) 20A of the concave mold base 20 is preferably about several tens of μm to 200 μm. Electroless nickel plating is applied to the surface of the concave mold base 20 to eliminate minute tool marks (bite cutting marks) on the molding surface 20A and crystal grain boundaries or crystal steps in the amorphous metal material. can do. Moreover, the durability of the surface of the concave mold base 20 made of a soft metal material of an aluminum alloy (AL-Mg alloy) can be improved.
And the concave-surface mold base 20 on which the electroless nickel plating is applied moves to the polishing step.

In the polishing step, the molding surface (plated film surface) 20A of the concave mold base 20 that has been plated in the plating step is polished. The plating film surface is polished by attaching a polishing tool including a hollow dome-shaped elastic body to a polishing apparatus having at least a mechanism for rotating a workpiece and a mechanism for rotating a polishing tool.
First, the polishing tool will be described.

FIG. 4 is a cross-sectional view showing a schematic configuration of a polishing tool used in the polishing step.
The polishing tool 4 shown in FIG. 4 includes a rotary support 5, an elastic body 6, a polishing cloth 7, and a pressing member 8, and a sealed space 9 is formed between the rotary support 5 and the elastic body 6. Yes.

  The rotary support 5 includes a disk-shaped support 5A having a substantially flat surface to which the elastic body 6 and the polishing pad 7 are attached, and the center of the support 5A on the other surface side of the disk-shaped support 5A. It includes a mounting rotary shaft 5B protruding from the portion and a check valve 5C. The mounting rotation shaft 5B is a mounting portion on which the rotary support 5 is mounted on the mounting portion of the polishing apparatus main body, and a screw that engages with the mounting portion of the polishing apparatus main body is engraved on the outer peripheral surface of the mounting rotating shaft 5B. Has been.

  The check valve 5C is attached through the disk-like support portion 5A at a position in the region of the sealed space 9 of the support portion 5A. The check valve 5 </ b> C has a function of introducing a pressure fluid into the sealed space 9 and keeping the pressure of the pressure fluid in the sealed space 9 constant.

  The elastic body 6 is composed of a sheet-like elastic body, and includes a dome portion 6A having a hollow dome shape, and a flange portion 6B provided in a bowl shape around the edge of the dome portion 6A. The dome shape of the dome portion 6A is shown as an example in the case of a hemispherical shape as shown in FIG. 4, but the dome shape in this embodiment is a hemispherical shape or a part of a spherical shape of a hemispherical shape. It may be a partial spherical shape.

  As a material of the elastic sheet, for example, nitrile rubber (NBR) having a thickness of about 1 mm and a hardness of about 45 (JIS-A) is used, and the dome portion 6A has a hollow dome shape with a curvature radius of about 45 mm. In addition to NBR, natural rubber, silicon rubber, styrene rubber, butadiene rubber, fluorine rubber, chloroprene rubber, or the like can be used as the material for the elastic sheet.

The polishing cloth 7 is a cellulose long-fiber nonwoven fabric, and is attached so as to cover the dome outer surface of the dome portion 6A of the elastic body 6 formed in a hollow dome shape.
The long-fiber nonwoven fabric of cellulose is a cloth in which short fibrous cellulose collected from cotton or pulp is laminated with fibers that have been subjected to chemical treatment and regenerated into a long fibrous form.

The polishing cloth 7 is a gauze type having a mesh structure of about 1.5 mm, and is composed of approximately four long-fiber nonwoven fabric nonwoven fabrics made of cellulose having a thickness of about 0.2 mm. That is, the thickness of the polishing pad 7 is about 0.8 mm. A long-fiber nonwoven fabric made of gauze-type cellulose has a strength that is difficult to break, but in order to exert a sufficient polishing effect due to its thin thickness, a plurality of sheets (about 2 to 6 sheets) are used in an overlapping manner. Is preferred.
Specific examples of the preferred long-fiber nonwoven fabric made of cellulose used for the polishing cloth 7 include high-grade wipers BEMCOT (registered trademark) M3 and M1 (trade name, manufactured by Asahi Kasei Fibers Co., Ltd.).

  The pressing member 8 is a ring-shaped member made of a metal such as stainless steel. The pressing member 8 sandwiches the flange portion 6B of the elastic body 6 and the polishing cloth 7 between the flat surface of the disk-like support portion 5A of the rotary support 5 so that the support portion 5A of the rotary support 5 is supported. Are fixed to the flat surface of the support portion 5A by fixing screws (not shown). As a result, the flange portion 6B of the elastic body 6 functions like a packing so as to be in close contact with the flat surface of the support portion 5A of the rotary support body 5, and the sealed space 9 is interposed between the support portion 5A and the elastic body 6. Can be formed.

  The polishing tool 4 configured in this manner is used by injecting a pressure fluid into the sealed space 9 from a check valve 5C attached to the support portion 5A of the rotary support 5. For example, compressed air is injected as the pressure fluid. By injecting compressed air into the sealed space 9, the elastic body 6 formed in a hollow dome shape is tensioned by internal pressure, and the hollow dome shape of the dome portion 6 </ b> A can be maintained. That is, the polishing cloth 7 attached so as to cover the dome outer surface of the dome portion 6A can be held in a hollow dome shape.

  In addition, the pressure of the compressed air inject | poured in the sealed space 9 is the range of 0.01 Mpa-0.02 Mpa. When the pressure is less than 0.01 MPa, the dome portion 6A of the elastic body 6 is not sufficiently stretched when the molded surface (plated film surface) subjected to the plating process is polished, and the dome portion 6A The polishing cloth 7 attached so as to cover the outer surface of the dome does not adhere to the molding surface, and polishing unevenness occurs on the polishing surface. On the other hand, when the pressure exceeds 0.02 Mpa, waviness occurs on the polished surface.

Then, the polishing tool 4 in which air is injected into the sealed space 9 and held in the shape of a hollow dome is mounted on a polishing apparatus, and the plating film surface is polished.
A polishing apparatus used for polishing includes a rotation mechanism for rotating a polishing tool mounted on a mounting portion and a direction along a rotation axis (see FIG. 1 of Patent Document 1 (Japanese Patent Laid-Open No. 2005-40977)) ( A moving mechanism that moves in the Z-axis direction), a rotating mechanism that rotates the workpiece (concave mold base 20) attached to the holding portion, a Y-axis direction and a Y-axis direction that are orthogonal to the rotating axis of the polishing tool. A so-called four-axis NC controlled polishing apparatus is used, which includes a moving mechanism for moving the workpiece to the right and a tilting mechanism for tilting the workpiece left and right with the Y-axis direction as the rotation axis. Specific examples of the 4-axis NC control polishing apparatus include, for example, super polishing machines KRP-2200F and FKP-1020F (both are trade names, manufactured by Kuroda Seiko Co., Ltd.).

The polishing tool 4 is mounted on the mounting portion of such a polishing apparatus. On the other hand, the concave mold base 20 is attached to the holding part of the polishing apparatus with the conical surface 20A facing the polishing tool 4 side.
Then, the concave mold base 20 rotates at a rotational speed of about 30min ^-1, the polishing tool 4 while rotating at a rotational speed of about 100 min ^-1, made a conical concave mold base 20 to rotate The plating film surface is polished by contacting the surface 20A (plating film surface) with a constant pressing load of about 3.8 kg and sliding the plating film surface and the polishing cloth 7 of the polishing tool 4 together. .

  In the polishing of the plated film surface, the entire rotation of the conical surface 20A of the concave mold base 20 attached to the holding portion is polished by CNC control of the rotating mechanism, moving mechanism and tilting mechanism of the polishing apparatus.

  In this polishing process, it is preferable to polish by supplying an abrasive between the plating film surface of the concave mold base 20 and the polishing cloth 7 of the polishing tool 4. A preferred abrasive is colloidal silica. Colloidal silica is a sol-like abrasive obtained by dialysis after allowing dilute hydrochloric acid to act on silicate. As a specific example, COMPOL 80 (manufactured by Fujimi Incorporated) can be mentioned.

By using the abrasive, the heat generated between the polishing cloth 7 and the plated film surface is cooled, and a polished surface with better surface accuracy can be obtained. Moreover, since the polishing cloth 7 is a gauze type having a mesh structure of about 1.5 mm, a sol-like abrasive is retained in the mesh structure, and the polishing performance is improved.
In the polishing step, the plating film surface formed on the conical surface 20A of the concave mold base 20 is polished to complete the concave mold base 20.

Next, the surface accuracy for each processing step of the processed concave mold base 20 will be described.
The surface accuracy for each processing step is determined by using a three-dimensional surface structure analysis microscope (ZYGO, NewView (registered trademark) 6300) as the processing surface of the concave mold base 20 at the end of processing in the cutting step, plating step, and polishing step. Using this, surface roughness (surface accuracy) was measured.

  FIG. 5A shows a surface shape curve of the concave mold base after the cutting process, and FIG. 5B shows a surface shape perspective curve of the concave mold base after the cutting process. Similarly, FIG. 6A shows a surface shape curve of the concave mold base after the plating step, and FIG. 6B shows a surface shape perspective curve of the concave mold base after the plating step. FIG. 7A shows the surface shape curve of the concave mold base after the polishing step, and FIG. 7B shows the surface shape perspective curve of the concave mold base after the polishing step.

  The surface shape perspective curves shown in FIGS. 5B, 6B, and 7B show the concave mold 22 that is completed by cutting the concave mold base 20 after each processing step. This is a result of setting a region of 70.5 μm × 53.0 μm in a substantially central portion of the molding surface 22A (see FIG. 3) as a measurement range. Each surface shape curve shown in FIGS. 5 (a), 6 (a) and 7 (a) shows a surface shape in the 70.5 μm direction of the measurement region of the surface shape perspective curve.

  Table 1 shows the measurement results of the surface accuracy of the molding surface for each of the processing steps shown in FIGS. The surface accuracy of the processed surface after each processing step is indicated by three parameters of PV (wavefront error), RMS (root mean square roughness), and Ra (center line average roughness).

In the surface accuracy results shown in Table 1, the conical surface 20A of the concave mold base material 20 cut to a surface accuracy of PV value 0.018 μm has electroless nickel plating on the surface of the cutting surface in the plating step. By being applied, the waviness and level difference of the cutting surface are eliminated, but the PV value spreads to 0.077 μm due to the partial abnormal precipitation of the deposited nickel. This partial abnormal precipitation of nickel can be prevented to some extent by delicate control of the oxidation-reduction potential and reaction rate in the plating solution, but it is difficult to eliminate it at all.

  However, in the polishing step, such a plating film surface is polished by using a polishing tool to which a polishing cloth 7 made of a cellulose non-woven fabric is attached so as to cover the dome outer surface of the dome portion 6A of the elastic body 6. A very smooth polished surface (molded surface) with surface accuracy of PV 1.574 nm, RMS 0.216 nm, and Ra 0.268 nm was obtained without breaking the surface shape (free-form surface shape). This is an abrasive cloth 7 made of an electroless nickel-plated coating film formed on the surface of the cutting surface, a dome-shaped elastic body 6 and a cellulose long fiber nonwoven fabric attached to cover the outer surface of the dome of the elastic body 6; Further, it is presumed that this is an effect obtained by the synergistic action of the abrasive with colloidal silica.

  Then, the completed concave mold base 20 is cut into a predetermined outer shape to complete the concave mold 22 shown in FIG. In FIG. 3, a molding surface (polishing surface) 22A having a free curved surface formed on the concave molding die 22 is a molding surface that forms a concave reflection surface of an aspherical mirror (aspherical mirror substrate) to be molded. Become.

  On the other hand, the convex surface molding die 32 (see FIG. 1) for molding the convex surface of the aspherical mirror (aspherical mirror substrate) cuts at least a metal material to form a cutting surface including the molding surface 32A. After the process and the plating process of plating the surface of the base material including the cutting surface, the convex mold 32 having the molding surface 32A is completed by cutting into a predetermined outer shape.

  The cutting process and the plating process for processing the convex mold 32 can be performed in the same manner as the concave mold 22. However, since the convex surface side of the aspherical mirror (aspherical mirror substrate) is a surface that is not used as a mirror, the convex shape in the cutting process is not a free-form surface having a plurality of inflection points, but a concave mold 22. It suffices to have a curved surface shape along the molding surface 22A. Therefore, the polishing process for polishing the plated film surface can be omitted.

  Then, as shown in FIG. 1, the completed concave mold 22 is fitted into the fixed side mold plate 21 as a nest, and the fixed mold 2 is set. Further, the convex mold 32 is fitted into the movable mold 31 as a nest, and the movable mold 3 is set. And the fixed mold | type 2 and the movable mold | type 3 are assembled | attached, and it becomes the mold base 1 which injection-molds the base material for aspherical mirrors.

  A plastic resin raw material is injected into a space S formed between the molding surface 22A of the concave mold 22 of the mold base 1 and the molding surface 32A of the convex mold 32, and the aspherical mirror substrate is molded. Is done. The raw material of the plastic resin is not limited as long as it has characteristics such as heat resistance and low hygroscopicity. For example, a cycloolefin polymer can be preferably used.

FIG. 8 shows a perspective view of the aspherical mirror substrate 10 molded using the mold base 1 (molding die). In the molded aspherical mirror substrate 10, a molding surface 22A made of a free curved surface having excellent surface accuracy of the concave mold 22 is transferred to the molding surface 10A.
Thereafter, the molded aspherical mirror substrate 10 is formed on at least the surface of the concave molding surface 10A on which a free-form surface is formed by using a dry method such as plasma treatment, sputtering, or ion plating. An aspherical mirror is completed by depositing a thin film such as nuume or chrome.

  According to the mold manufacturing method of the present embodiment described above, in the shape creation step, the molding surface 20A of the concave mold base 20 including the molding surface 22A having the free curved surface of the concave mold 22 is cut. A formed surface (plated film surface) 20A that has been formed and plated in the plating process and has eliminated fine tool marks and metal crystal grain boundaries or crystal steps due to cutting is formed into a hollow dome shape in the polishing process. A polishing tool 4 including an elastic body 6 having a dome portion 6A having the shape of the above and an abrasive cloth 7 made of a cellulose long-fiber nonwoven fabric attached so as to cover the dome outer surface of the dome portion 6A is abutted and polished. Thus, the concave mold 22 that can mold the molding surface 22A having a free-form surface with high surface accuracy is obtained.

  Further, since the polishing cloth 7 made of a cellulose non-woven fabric constituting the polishing tool 4 is a gauze type having a mesh structure, a molding surface (plating coating surface) 20A and The abrasive supplied between the polishing tool 4 (abrasive cloth 7) is retained in the mesh structure of the abrasive cloth 7 to cool the heat generated between the molding surfaces 20A and synergize with the abrasive. The polishing performance is improved by the action.

  Further, in the polishing step, the polishing tool 4 in which a pressure fluid of 0.01 Mpa to 0.02 Mpa is injected into the dome portion 6A having a hollow dome shape of the elastic body 6 is formed by plating. By polishing in contact with the surface (plated film surface) 20A, a concave mold 22 is obtained that can mold the molding surface 22A having a free-form surface with high surface accuracy without causing uneven polishing or waviness. It is done.

In the above embodiment, the case of the concave mold 22 used for injection molding the aspherical mirror substrate 10 has been described as the mold, but the present invention is not limited to this, and various optical glass lenses having a free curved surface. The same applies to the mold used for cast molding and the like, and the reheat press mold.
Moreover, although the case where the molding surface 22A of the concave mold 22 is provided with a non-rotation-axisymmetric aspheric surface (free-form surface) is not limited to this, it may be a rotation-axis-symmetric aspheric surface. Etc.

In the above embodiment, instead of the polishing tool 4 used in the polishing step, the polishing portion (31) proposed in Patent Document 2 (Japanese Patent Laid-Open No. 2005-169520) is supported and attached to the mounting portion. The polishing part (31) of the polishing tool (3) having a configuration including the attached support part (32) and a rotation restricting part (33) between the support part and the polishing part is formed into a hollow dome shape in the present embodiment. It is preferable to use a polishing tool having a configuration in which a polishing cloth 7 made of a long-fiber cellulose non-woven fabric is attached so as to cover the elastic body 6 having the shape and the dome outer surface of the dome portion 6A of the elastic body 6.
By using the polishing tool having this configuration, it is possible to prevent an excessive frictional force from being applied to the surface of the plating film surface of the concave mold base 20 to be polished, and to obtain a molding surface with better surface accuracy.

Further, in the above embodiment, the concave mold 22 used for injection molding the aspherical mirror substrate 10 is cut into a predetermined outer shape after processing the substantially conical concave mold base 20. In the case of being completed, the case where the above-described series of processing is performed using a base material having an outer shape cut in advance to the concave mold 22 at the time of completion, or at least the concave mold base 20 is included. After performing the above-described series of processing on the outer shape base material, it may be cut into a predetermined shape and used as the concave mold 22.
In addition, as shown in the embodiment, when the concave surface molding die 22 is processed using the substantially conical concave surface molding die base material 20, a large number of concave surface molding dies can be simultaneously formed from one concave surface molding die base material 20. 22 can also be manufactured.

The cross-sectional schematic diagram of the mold base in which the shaping | molding die was set. The perspective view of a concave surface mold base material. The perspective view of a concave surface shaping | molding die. Sectional drawing which shows schematic structure of a polishing tool. (A) Surface shape curve of concave mold base material after cutting process, (b) Surface shape perspective curve of concave mold base material after cutting process. (A) Surface shape curve of concave mold base after plating step, (b) Surface shape perspective curve of concave mold base after plating step. (A) Surface shape curve of concave mold substrate after polishing step, (b) Surface shape perspective curve of concave mold substrate after polishing step. The perspective view of the base material for aspherical mirrors shape | molded using the shaping | molding die.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Mold base, 2 ... Fixed type, 3 ... Movable type, 4 ... Polishing tool, 5 ... Rotation support body, 5A ... Support part, 5B ... Mounting rotary shaft, 5C ... Check valve, 6 ... Elastic body, 6A ... Dome portion, 6B ... flange portion, 7 ... polishing cloth, 8 ... pressing member, 9 ... sealed space, 10 ... base material for aspherical mirror, 20 ... concave surface mold base material, 20A ... conical surface, 21 ... fixed Side mold plate, 22 ... concave mold, 22A, 32A ... molding surface, 31 ... movable side mold, 32 ... convex mold.

Claims (3)

A method for producing a molding die used for molding an optical article having a free-form surface on a molding surface,
A shape creation step for forming a free curved surface on the molding surface, a plating step for plating the molding surface on which a free curved surface is formed, and a polishing step for polishing the plated molding surface,
The polishing step includes
A polishing tool comprising: a hollow dome-shaped elastic body; and a polishing cloth made of a long-fiber cellulose nonwoven fabric attached so as to cover an outer dome surface of the hollow dome-shaped elastic body,
A method for producing a mold, wherein the mold is brought into contact with the plated surface and polished. In the manufacturing method of the shaping | molding die of Claim 1,
The manufacturing method of the shaping | molding die characterized by the abrasive cloth which consists of the said cellulose long fiber nonwoven fabric which comprises the said abrasive tool being a gauze type provided with the mesh structure. In the manufacturing method of the shaping | molding die of Claim 1 or 2,
The hollow dome-shaped elastic body constituting the polishing tool is:
A manufacturing method of a mold, wherein a pressure fluid of 0.01 Mpa to 0.02 Mpa is injected into the hollow dome.