JP2007098537A - Polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a smooth mirror face by preventing generation of rainbow marks caused by cutting streaks, etc. by small machining man-hours without requiring a skilled technician. <P>SOLUTION: A polishing surface 9 of a workpiece 1 is polished by impressing ultrasonic waves 4a from an ultrasonic generator 4 by storing polishing material solution 3 including a polishing material 3a in an ultrasonic washing tank 2, immersing the workpiece 1 in the polishing material solution 3 and activating the polishing material 3a by cavitation 5a by energy of the ultrasonic waves 4a. In this case, the cutting streaks, etc. can be effectively removed without damaging the polishing face 9 by using the micro polishing material 3a of a micro nano meter level to prevent defects such as rainbow marks (rainbow-colored interference light) caused by the cutting streaks. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polishing technique and, for example, relates to a polishing method for improving the appearance quality of a workpiece such as a plastic molding die that has been cut.

  Conventionally, in the molding of plastic lenses, an electroless nickel-plated layer made of Ni and P capable of ultra-precise cutting is formed on the optical mirror surface of the molding die, and this plated layer is mirror-finished by cutting with a diamond tool. It is common to process, and it is described also in patent document 1 as a general technique.

  In the above-described processing method, an optical mirror surface having a roughness Ra of several nanometers is obtained by using a diamond cutting tool having a good cutting edge outline accuracy, cutting a cutting amount of several micrometers, and a feed rate of several millimeters per minute. Obtainable.

  However, as shown in FIGS. 4 and 5, the regular cutting striation 102 created by a cutting tool such as a diamond cutting tool is formed on the processing surface of the workpiece 101 processed by the above-described processing method using the diamond cutting tool. When white light is incident on this processed surface, the reflected light becomes interference light having a rainbow color due to light interference. This interference light is a defect called a rainbow eye.

Further, the cutting streak 102 of the molding die is also transferred to the optical element that is a product at the time of molding, and rainbow eyes appear on the surface of the optical element.
Since this interference light (rainbow eye) may cause a problem in product function depending on the use of the optical element, in such a case, polishing is performed after cutting the molding die, and the cutting streak 102 is obtained. Need to be removed.

  However, since the polishing process for removing the cutting streak 102 requires maintaining the shape created by the ultra-precise cutting process so as not to damage the optical mirror surface, It is done manually by workers, and it has technical problems such as poor yield, large processing man-hours, high parts cost, quality due to manual processing, and limited number of processing workers to technicians. ing.

In addition, the above-mentioned patent document 1 forms a processing layer of electroless nickel plating composed of Ni and P on a base material, and performs a heat treatment after performing a mirror surface processing by cutting with a diamond tool, so that a high temperature can be obtained. It is intended to improve surface shape accuracy and surface roughness in glass molding, and still has the technical problems as described above.
JP-A-11-157852

  It is an object of the present invention to obtain a smooth mirror surface by preventing generation of rainbow eyes due to cutting streaks and the like at a low cost with a small number of processing steps, without requiring a skilled technician. It is to provide a polishing technique.

Another object of the present invention is to provide a polishing technique capable of obtaining a workpiece of stable quality with a high yield.
Another object of the present invention is to provide a smooth mirror surface by preventing the generation of rainbow eyes caused by cutting streaks without damaging the workpiece and without damaging the original shape of the workpiece. It is to provide a polishing technique that can be obtained.

A first aspect of the present invention provides a polishing method for polishing a workpiece by immersing the workpiece in a solution containing an abrasive and applying ultrasonic waves to the solution.
According to a second aspect of the present invention, in the polishing method according to the first aspect,
Provided is a polishing method for imparting at least one of rotational displacement and linear displacement to the workpiece so as to pass through a position where cavitation occurs in the solution.

According to a third aspect of the present invention, in the polishing method according to the first aspect,
There is provided a polishing method for changing a position of occurrence of cavitation in the solution relative to the workpiece immersed in the solution by changing a frequency of the ultrasonic wave.

According to a fourth aspect of the present invention, in the polishing method according to the first aspect,
Provided is a polishing method for changing the position of cavitation in the solution relative to the workpiece immersed in the solution by changing the pressure of the solution.

According to a fifth aspect of the present invention, in the polishing method according to the first aspect,
The abrasive provides a polishing method including cluster particles in which fine abrasive grains are aggregated.
According to a sixth aspect of the present invention, in the polishing method according to the first aspect,
Provided is a polishing method in which the abrasive is cluster particles in which abrasive grains such as diamond, alumina, cerium oxide, zirconia, or silicon oxide having a size of several tens of nanometers or less are aggregated with a size of several hundred nanometers or less. To do.

According to a seventh aspect of the present invention, in the polishing method according to the first aspect,
A polishing method is provided in which the workpiece is a plastic mold.
An eighth aspect of the present invention is a polishing method after cutting a plastic molding die, wherein an ultrasonic cleaning tank is filled with a solution in which an abrasive is uniformly dispersed, and the ultrasonic cleaning tank Is subjected to ultrasonic vibration of 20 kHz to 100 kHz, so that the workpiece is immersed in the ultrasonic cleaning tank, and in the region where cavitation occurs in the ultrasonic cleaning tank, the polishing target portion of the work stays for almost the same time. A polishing method for giving such a displacement to the workpiece is provided.

According to a ninth aspect of the present invention, in the polishing method according to the eighth aspect,
The polishing material provides a polishing method in which abrasive particles such as diamond, alumina, cerium oxide, zirconia, or silicon oxide having a size of several tens of nanometers or less are clustered particles having a size of several hundred nanometers or less. .

According to the present invention, it is possible to obtain a smooth mirror surface by preventing generation of rainbow eyes caused by cutting streaks and the like at a low cost with a small number of processing steps without requiring a skilled technician. .
In addition, it is possible to obtain a workpiece of stable quality with a high yield.

  Further, it is possible to obtain a smooth mirror surface by preventing the occurrence of rainbow eyes caused by cutting streaks without damaging the workpiece and without damaging the original shape of the workpiece. .

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a conceptual diagram illustrating an example of the configuration of a polishing apparatus that performs a polishing method according to an embodiment of the present invention. FIGS. 2 and 3 illustrate the operation of the polishing method according to the present embodiment. It is sectional drawing which shows an example.

The polishing apparatus M according to the present embodiment includes an ultrasonic cleaning tank 2, an abrasive solution 3, an ultrasonic generator 4, a control unit 10, and a holding mechanism 20.
The ultrasonic cleaning tank 2 stores the abrasive solution 3 and is provided with an ultrasonic generator 4 at the bottom. Then, the energy of the ultrasonic wave 4 a is applied to the abrasive solution 3 upward from the ultrasonic generator 4.

The operation of the ultrasonic generator 4 is controlled by the control unit 10, and for example, the wavelength and intensity of the oscillating ultrasonic wave 4a can be controlled.
The holding mechanism 20 is disposed in the upper part of the ultrasonic cleaning tank 2 and performs an operation of holding the work 1 and immersing it in the abrasive solution 3 stored in the ultrasonic cleaning tank 2. In this case, the holding mechanism 20 performs arbitrary three-dimensional displacement such as rotational displacement (rotational motion R) about the vertical direction and linear displacement (vertical motion V) that moves up and down the ultrasonic cleaning tank 2. The work 1 can be given.

  The holding operation and displacement of the work 1 by the holding mechanism 20 are controlled by the control unit 10. Therefore, the polishing operation described later in this embodiment can be automated as necessary.

  That is, the control unit 10 controls the ON / OFF timing and the oscillation wavelength of the ultrasonic wave 4 a in the ultrasonic generator 4, the immersion of the work 1 in the abrasive solution 3 by the holding mechanism 20, and the displacement of the work 1. It is possible to link such control.

  The workpiece 1 is made of, for example, a molding die, and the cutting surface 6 is present on the molding surface (polishing surface 9) to be polished by cutting. The workpiece 1 is, for example, a plastic molding die used for manufacturing an optical element by resin molding.

  The ultrasonic cleaning tank 2 in which the workpiece 1 subjected to the cutting process is immersed is filled with the abrasive solution 3 in which the abrasive 3a is uniformly dispersed. Here, as an example, a diamond cluster 7 in which diamond particles 8 having a diameter of several tens of nanometers or less have a size of several hundreds of nanometers or less (maximum diameter when aggregated) and are agglomerated with a weak bonding force is used as an abrasive 3a It explains as what is used as.

  As the abrasive 3a, in addition to diamond, abrasive grains such as alumina, cerium oxide, zirconia, or silicon oxide having a diameter of several tens of nanometers or less have a size of several hundred nanometers or less (maximum when aggregated). Cluster particles aggregated with a diameter of (5) can also be used.

Here, when the diameter of the particle | grains of the abrasive | polishing material 3a exceeds several tens nanometer, since the damage | wound which becomes a problem on optical quality may be attached to the surface of the workpiece | work 1, it is unpreferable.
In addition, even when the maximum diameter of the cluster particles in which the abrasive grains are aggregated exceeds several hundred nanometers, the kinetic energy when the cluster particles collide with the surface of the work 1 increases, and the surface of the work 1 has a high optical quality. This is not preferable because it may cause scratches that cause problems.

The operation of the polishing apparatus M of the present embodiment having the above configuration will be described with reference to FIGS.
When an ultrasonic vibration of 20 kHz to 100 kHz is applied to the abrasive solution 3 by the ultrasonic generator 4 provided at the bottom of the ultrasonic cleaning tank 2 filled with the abrasive solution 3, the abrasive is generated by the energy of the ultrasonic wave 4a. A pressure difference occurs in the solution 3.

  The frequency of the ultrasonic generator 4 described above is a standard numerical value. When the frequency is below this range, there is a problem that the processing capability by the ultrasonic wave is low, and when it exceeds this range, the apparatus becomes large. There is a problem.

  The low pressure portion is vaporized and small bubbles 5 are generated. The bubbles 5 are crushed and collapsed by the pressure of the abrasive solution 3 in a short time, and a high-energy shock wave is generated at this time. These phenomena and the generated bubbles are called cavitation, but here, the destruction phenomenon of the bubbles 5 will be particularly defined and defined as cavitation 5a.

  When the work 1 is immersed in the ultrasonic cleaning tank 2, as illustrated in FIG. 2, the surface of the work 1 at the position where the cavitation 5 a occurs (height H from the bottom of the ultrasonic cleaning tank 2) Diamond clusters 7 of several tens of nanometers or less bonded in a size of 100 nanometers or less explosively collapse due to the shock wave of the cavitation 5a, and are scattered and scattered in all directions as shown in FIG. Among these, the diamond particles 8 scattered along the surface of the workpiece 1 particularly preferentially remove the convex portions of the cutting streaks 6 present on the polishing surface 9, so that the cutting streaks 6 disappear.

  As described above, the surface of the workpiece 1 is activated more efficiently than when the single diamond particle 8 is used due to the cavitation effect and the fracture energy of the bonded diamond cluster 7 by activating the abrasive 3a by the energy of the ultrasonic wave 4a. The cutting streaks 6 are removed to form a smooth polished surface 9. Further, since each diamond particle 8 is as small as several tens of nanometers, the surface of the work 1 is not damaged.

  On the other hand, it is known that cavitation 5a often occurs from the bottom surface of the ultrasonic cleaning tank 2 at a position of 1/2 wavelength interval of the ultrasonic wave 4a. The workpiece 1 is given a uniform vertical motion V and a rotational motion R of 10 rpm to 500 rpm so that all points on the polishing surface 9) stay for the same time. As a result, the entire surface of the workpiece 1, particularly the polishing surface 9, is uniformly polished.

  According to the polishing method of the present embodiment as described above, the cutting streak 6 is removed without damaging the surface (polishing surface 9) of the workpiece 1 and defects such as rainbow eyes (interference light) are eliminated. A smooth mirror surface can be obtained as the polished surface 9.

  Further, since the entire surface of the workpiece 1 can be uniformly polished, the original shape of the polished surface 9 created by the cutting process other than the cutting streak 6 is not impaired. As a result, a high quality workpiece 1 can be obtained with a high yield.

  Furthermore, the above-described polishing process according to the present embodiment can automatically polish the workpiece 1 by controlling the ultrasonic generator 4 and the simple holding mechanism 20 to be interlocked by the control unit 10. .

  In other words, compared with the work by hand polishing by skilled technicians, which has been required in the past, the quality and yield rate can be improved, the number of processing steps can be greatly reduced, and even workers without skills can easily perform the work 1 Polishing can be performed, and the manufacturing cost of the workpiece 1 can be reduced.

As a result, for example, when the work 1 is a resin molding die of an optical element, a high-quality optical element free from defects such as rainbow eyes can be provided at low cost.
That is, according to the present embodiment, the polishing surface 9 can be smoothly smoothed by preventing generation of rainbow eyes caused by the cutting streaks 6 and the like in the workpiece 1 with a small number of processing steps without requiring a skilled technician. It is possible to obtain a simple mirror surface.

  In addition, the generation of rainbow eyes caused by the cutting streaks 6 and the like existing on the polishing surface 9 without damaging the polishing surface 9 of the work 1 and without damaging the original shape of the polishing surface 9 of the work 1. Therefore, a smooth mirror surface can be obtained on the polished surface 9.

  In the above description, the case in which the polishing surface 9 of the workpiece 1 is uniformly passed through the cavitation 5a by giving the rotational motion R and the vertical motion V to the workpiece 1 is exemplified. 3, the position of the cavitation 5a (height H) may be relatively changed.

  That is, as described above, since the cavitation 5a is formed at the position of the ½ wavelength interval of the ultrasonic wave 4a, the position (height) of the cavitation 5a is changed by changing the wavelength of the ultrasonic wave 4a by the control unit 10. H) can be varied.

  Further, when the frequency of the ultrasonic wave 4a is constant, by changing the pressure of the abrasive solution 3 (that is, the propagation speed of the ultrasonic wave 4a in the abrasive solution 3), the wavelength of the ultrasonic wave 4a is changed, and the cavitation 5a. The position of can also be changed.

  In this case, it is possible to change the pressure of the abrasive solution 3 by making the ultrasonic cleaning tank 2 a sealed structure, filling the abrasive solution 3 inside, and pressurizing the abrasive solution 3 with a pressurizing mechanism (not shown). It is. Naturally, the pressurizing mechanism is controlled by the control unit 10.

Needless to say, the present invention is not limited to the configuration exemplified in the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, the abrasive 3a is not limited to those exemplified in the above embodiment. Needless to say, the configuration of the polishing apparatus M can be variously changed.

It is a conceptual diagram which shows an example of a structure of the grinding | polishing apparatus which implements the grinding | polishing processing method which is one embodiment of this invention. It is sectional drawing which shows an example of an effect | action of the grinding | polishing processing method which is one embodiment of this invention. It is sectional drawing which shows an example of an effect | action of the grinding | polishing processing method which is one embodiment of this invention. It is a top view which shows the cutting trace of the workpiece | work in the reference technique of this invention. It is sectional drawing which shows the cutting trace of the workpiece | work in the reference technique of this invention.

Explanation of symbols

1 Workpiece 2 Ultrasonic Cleaning Tank 3 Abrasive Material Solution 3a Abrasive Material 4 Ultrasonic Generator 4a Ultrasonic Wave 5a Cavitation 6 Cutting Strip 7 Diamond Cluster 8 Diamond Particle 9 Polishing Surface 10 Control Unit 20 Holding Mechanism 101 Work 102 Cutting Strip Mark M Polishing device R Rotational motion V Vertical motion

Claims (9)

  A polishing method characterized by polishing the workpiece by immersing the workpiece in a solution containing an abrasive and applying an ultrasonic wave to the solution. The polishing method according to claim 1, wherein
A polishing method, wherein at least one of rotational displacement and linear displacement is applied to the workpiece so as to pass through a position where cavitation occurs in the solution. The polishing method according to claim 1, wherein
A polishing method characterized by changing a position of occurrence of cavitation in the solution relative to the workpiece immersed in the solution by changing a frequency of the ultrasonic wave. The polishing method according to claim 1, wherein
A polishing method, wherein the position of cavitation in the solution is changed relative to the workpiece immersed in the solution by changing the pressure of the solution. The polishing method according to claim 1, wherein
The polishing method according to claim 1, wherein the abrasive includes cluster particles in which fine abrasive grains are aggregated. The polishing method according to claim 1, wherein
The abrasive is a cluster particle in which abrasive grains such as diamond, alumina, cerium oxide, zirconia, or silicon oxide having a size of several tens of nanometers or less are aggregated in a size of several hundred nanometers or less. Polishing method. The polishing method according to claim 1, wherein
A polishing method, wherein the workpiece is a plastic mold.   A polishing method after cutting of a plastic mold, wherein an ultrasonic cleaning tank is filled with a solution in which an abrasive is uniformly dispersed, and ultrasonic vibration of 20 kHz to 100 kHz is applied to the ultrasonic cleaning tank. And immersing the workpiece in the ultrasonic cleaning tank, and giving the workpiece a displacement so that the polishing target portion of the workpiece stays for almost the same time in the region where cavitation occurs in the ultrasonic cleaning tank. A polishing method characterized by the above. The polishing method according to claim 8, wherein
Polishing characterized in that the abrasive is cluster particles in which abrasive grains such as diamond, alumina, cerium oxide, zirconia, or silicon oxide having a size of several tens of nanometers or less are aggregated in a size of several hundred nanometers or less. Processing method.

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