JP2011083851A - Polishing method of metal die for molding optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing method of a metal die for molding an optical element in which skillful technique is not required and quality more easily becomes constant. <P>SOLUTION: In the polishing method, a molded surface 101 is polished in a mirror surface form by blasting an abrasive grain 20 made of a diamond onto the molded surface 101 while rotating the metal die 10 for molding the optical element. Average surface roughness of the molded surface 101 immediately before the abrasive grain 20 made of the diamond is blasted is made to 15-30 nm, and the abrasive grain 20 made of the diamond is a coagulation body in which single grains of 0-1 μm are coagulated to a size of 0.2-0.5 mm. In the polishing method of the metal die for the molding the optical element, the blasting is performed such that a blast speed of the abrasive grain made of the diamond is 1,300-1,800 m/min and a blast angle of the abrasive grain 20 made of the diamond is retained to 25-35°. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for polishing an optical element molding die.

The optical element molding die can be obtained by forming the molding surface by cutting and polishing the surface of the base material.
Cutting is generally an operation of machining a base material using a diamond cutting tool with good edge contour accuracy, a cutting amount of several micrometers, and a feed rate of several millimeters per minute. Since cutting striations at regular intervals are created on the surface of the base material after cutting, it is necessary to polish the surface in order to remove the cutting streaks. Conventionally, this polishing has been performed manually by skilled technicians (see, for example, Patent Document 1).

JP 2007-253272 A

  However, since polishing is a manual work even if it is performed by a skilled technician, the yield is poor, and the time and labor are increased, resulting in an increase in cost, and the quality varies due to manual processing. There was a problem. In recent years, the molding surface of the mold has a tendency to increase in size, and these problems have become more prominent.

The present inventor has intensively studied and does not require any skill as long as it is a polishing method for blasting diamond abrasive particles having a specific particle diameter on a molding surface having a specific surface roughness at a specific blast speed and blast angle. The inventors have found that the quality can be made easier and constant, and the present invention has been completed.
The present invention includes the following (1) to (3).
(1) A polishing method in which a diamond polishing particle is blasted on a molding surface of an optical element molding die while the molding surface is rotated, and the molding surface is polished into a mirror surface, immediately before blasting the diamond polishing particle. The molding surface has an average surface roughness of 15 to 30 nm, and the diamond abrasive particles are aggregates in which single particles of more than 0 and 1 μm or less are aggregated to a size of 0.2 to 0.5 mm, and the diamond A polishing method for an optical element molding die, wherein the blasting speed of the abrasive particles is 1300 to 1800 m / min, and the blasting angle of the diamond abrasive particles is maintained at 25 to 35 degrees.
(2) The polishing method for an optical element molding die according to (1), wherein the rotational speed of the optical element molding die is 50 to 150 rpm.
(3) The polishing method for an optical element molding die according to (1) or (2), wherein rotation control, blast angle control, and blast position control of the optical element molding die are performed by NC control.

  According to the present invention, it is possible to provide a polishing method for an optical element molding die that does not require skill and is simpler in quality. This polishing method can achieve these effects even when the molding surface of the mold is large.

FIG. 1 is a schematic perspective view showing a state in which diamond abrasive particles are blasted onto a molding surface of a rotating optical element molding die in the polishing method of the present invention. FIG. 2 is a schematic cross-sectional view showing a cross-section at the rotation center axis in FIG.

The present invention will be described.
The present invention is a polishing method for polishing a diamond-shaped abrasive particle on its molding surface while rotating the optical element molding die, and polishing the molding surface into a mirror-like shape, and blasting the diamond-made abrasive particle The average surface roughness of the molding surface immediately before is 15 to 30 nm, and the diamond abrasive particles are aggregates in which single grains of more than 0 and 1 μm or less are aggregated to a size of 0.2 to 0.5 mm, A polishing method for an optical element molding die, wherein the blasting speed of diamond abrasive particles is 1300 to 1800 m / min, and the blasting angle of the diamond abrasive particles is maintained at 25 to 35 degrees.
Hereinafter, such a polishing method is also referred to as “the polishing method of the present invention”.

  In the polishing method of the present invention, all of the four factors of “average surface roughness of the molding surface”, “diamond abrasive particles”, “blast speed” and “blast angle” are set within a predetermined range. Adjust and polish. The inventor has found that an excellent effect is exhibited when all of these four factors are within a specific range.

  In the polishing method of the present invention, first, the average surface roughness of the molding surface immediately before blasting the diamond abrasive particles is set to 15 to 30 nm. This average roughness is preferably 18 to 27 nm, and more preferably 21 to 24 nm.

The method for obtaining such average surface roughness is not particularly limited, and for example, a conventionally known method can be applied. For example, there is a method in which a die base material is cut and processed using a diamond cutting tool having a good cutting edge contour, a cutting amount of several micrometers, and a feed rate of several millimeters per minute. In addition, since the surface of the surface obtained by cutting with such a conventionally known cutting method creates cutting marks at regular intervals, further polishing with a conventionally known method enables the average within the above range. It can also be surface roughness.
In addition, for example, an optical element molding die after performing an operation of press molding a preform or the like to obtain an optical element may have an average surface roughness within the above range. Alternatively, diamond abrasive particles may be blasted. In the case of an optical element molding die after performing an operation to obtain an optical element by press molding a preform or the like, if the molding surface does not have an average surface roughness within the above range, a conventionally known method By polishing the surface, the average roughness within the above range can be adjusted.

  In the present invention, the average surface roughness means a value obtained by measurement using a laser interferometer.

Next, in the polishing method of the present invention, diamond abrasive particles are blasted on the molding surface while rotating the optical element molding die.
Such an operation will be described with reference to FIGS.
FIG. 1 is a schematic perspective view showing a state in which diamond abrasive particles are blasted onto a molding surface of a rotating optical element molding die in the polishing method of the present invention. FIG. 2 is a diagram (schematic cross-sectional view) showing a cross section at the center of the rotating shaft in FIG.

In FIG. 1 and FIG. 2, an optical element molding die 10 (hereinafter sometimes simply referred to as “mold 10”) is fixed to a pedestal 12, and the pedestal 12 is connected to a motor 16 via a rotating shaft 14. It is connected to a rotating shaft (not shown in the figure). Since such a configuration is provided, the mold 10 can be rotated at a desired rotation speed by rotating the motor 16.
Further, the diamond abrasive particles 20 are blown out from the pencil blasting device 22 at a desired speed, and the diamond abrasive particles 20 are sprayed and blasted to the molding surface 101 of the mold 10 in a rotated state at a desired angle α. it can. The angle α will be described in detail later.

  1 and 2 can be controlled so that a contact point P, which will be described later, is at a desired position on the X axis in the left-right direction (horizontal direction) in FIG.

  1 and 2, the rotation control, blast angle control, and blast position control of the optical element molding die can be performed by NC control. It is preferable to perform NC control, particularly CNC control, because polishing with more constant quality can be performed. The NC control will be described in detail later.

  In the polishing method of the present invention, as shown in FIGS. 1 and 2, the diamond abrasive particles 20 are blasted onto the molding surface 101 while rotating the mold 10. It is preferable to blast the diamond abrasive particles 20 from the outer peripheral side to the inner peripheral side of the molding surface 101.

The diamond abrasive particles 20 are aggregates in which single particles of more than 0 and 1 μm or less are aggregated to a size of 0.2 to 0.5 mm. This is because, when an aggregate having such a size is blasted under a specific condition, an optical element molding die having a uniform quality can be obtained more easily. It is preferably an aggregate obtained by agglomerating single grains of more than 0 and 1 μm or less in a size of 0.3 to 0.4 mm.
Here, the aggregate does not mean an aggregate in which only single particles of more than 0 and 1 μm are aggregated. It means the one in which single grains of more than 0 and 1 μm are aggregated. Specifically, the single grain of 0 to 1 μm constituting the aggregate may be 90% by mass or more.
In addition, the particle size of a single grain and an aggregate shall mean the value obtained by measuring by the laser diffraction scattering method.

Further, the abrasive particles 20 are blasted at a blasting speed of 1300 to 1800 m / min. This is because, when the agglomerates as described above are blasted under specific conditions, an optical element molding die having a uniform quality can be obtained more easily. The blast speed is preferably 1400 to 1700 m / min, and more preferably 1500 to 1600 m / min.
In the present invention, the blasting speed means an initial speed at which the abrasive particles 20 are ejected from the blasting device (pencil blasting device 22).

Further, blasting is performed so that the blast angle of the abrasive particles 20 is maintained at 25 to 35 degrees. This is because, when the agglomerates as described above are blasted under specific conditions, an optical element molding die having a uniform quality can be obtained more easily. The blast angle is preferably 27 to 33 degrees, more preferably 29 to 31 degrees, and further preferably about 30 degrees.
In the present invention, the blast angle is the smallest angle α (≦ 90) formed by the center line 201 of the flow of the diamond abrasive particles 20 blasted (sprayed) toward the molding surface 101 and the molding surface 101. °).

  Moreover, it is preferable to perform blasting at a rotational speed of the mold 10 of 50 to 150 rpm. In the polishing method of the present invention, when blasting is performed at such a rotational speed, a practically preferable quality can be obtained, but a rotational speed of 80 to 120 rpm is particularly preferable. This is because it is possible to obtain a mold for molding an optical element that is easier and more stable in quality.

  In the polishing method of the present invention, it is preferable to perform rotation control, blast angle control, and blast position control of the optical element molding die by NC control. If these are NC controlled and can be automatically polished, even if there is no skilled technique, it is possible to obtain an optical element molding die with a more uniform quality. is there. This polishing method can be applied without problems even when the molding surface of the mold is large, and provides these effects. The apparatus shown in FIGS. 1 and 2 is NC controlled.

Here, the rotation control of the optical element molding die means control for setting the rotation speed of the die 10 by the motor 16 to a desired value at 50 to 150 rpm.
The blast angle control means controlling the blast angle α described above. In the embodiment shown in FIGS. 1 and 2, the angle θ (≦ 90 °) formed by the rotation center axis S and the horizontal plane can be adjusted to a desired value as shown in FIG. It can be adjusted to a desired value within a range of ˜35 degrees.
Blast position control means controlling the position on the X axis of the contact point P between the center line 201 and the molding surface 101 to a desired value. The X axis means a horizontal axis in the left-right direction in FIG. In the apparatus shown in FIGS. 1 and 2, the contact P can be moved to a desired position on the X axis by NC control while maintaining the angle θ.

The optical element molding die was actually polished using the apparatus shown in FIGS. As the diamond abrasive particles, SP-RO 1 / 2μ manufactured by Asahi Diamond Industrial Co., Ltd. was used. The diamond abrasive particles are aggregates in which single particles of more than 0 and 1 μm or less are aggregated to a size of 0.2 to 0.5 mm.
Table 1 shows specific processing conditions (polishing conditions). In all Examples and Comparative Examples, the average surface roughness of the molding surface immediately before blasting the diamond abrasive particles was 15 to 30 nm.

  From such an experiment, it was confirmed that the processing conditions within the scope of the present invention have a good effect.

DESCRIPTION OF SYMBOLS 10 Optical element shaping | molding die 101 Molding surface 12 Base 14 Rotating shaft 16 Motor 20 Abrasive particle 201 Center line 22 Pencil blasting device P Contact S Rotating central shaft

Claims (3)

While rotating the optical element molding die, blasting diamond abrasive particles on the molding surface, polishing the molding surface in a mirror shape,
The average surface roughness of the molding surface immediately before blasting the diamond abrasive particles is 15 to 30 nm,
The diamond abrasive particles are aggregates in which single particles of more than 0 and 1 μm or less are aggregated to a size of 0.2 to 0.5 mm,
The diamond abrasive particles have a blasting speed of 1300 to 1800 m / min,
A polishing method for an optical element molding die, wherein the blasting angle of the diamond abrasive particles is kept at 25 to 35 degrees.   The method for polishing an optical element molding die according to claim 1, wherein a rotation speed of the optical element molding die is 50 to 150 rpm. The method for polishing an optical element molding die according to claim 1 or 2, wherein rotation control, blast angle control, and blast position control of the optical element molding mold are performed by NC control.

Images