JP2004351574A - Precise polishing tool and precise polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a precise polishing tool and a precision polishing method capable of rapidly polishing a nonaxisymmetric and aspheric surface with high surface precision. <P>SOLUTION: With the usage of the precise polishing tool 1 having an elastic polishing body 3 expanded in a shape of a dome or formed in the shape of the dome, a surface to be polished and the elastic polishing body 3 are respectively rotated while pressing the elastic polishing body 3 onto almost all the surface to be polished, and a slurry type polishing agent 10 is supplied to the elastic polishing body 3 to polish the surface to be polished. A surface roughness average value Ra of the elastic polishing body 3 is preferably 0.1 μm or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a precision polishing tool and a precision polishing method for finishing a surface of a lens or the like to a mirror surface.
[0002]
[Prior art]
NC control cutting technology has advanced, and it has become possible to form non-axisymmetric aspheric surfaces such as lenses by cutting. In optical products, it is necessary to polish the created cut surface to a desired smooth optical mirror surface. In recent years, the performance of lenses has been improved, and the requirements for shape accuracy and surface accuracy for mirror polishing have become strict.
[0003]
Conventionally, as shown in Patent Document 1, a hollow dome-shaped polisher head made of a rubber-like elastic material has been used for mirror polishing of a non-axisymmetric aspheric surface. In the polishing method, a polishing pad is attached to the surface of the polisher head, compressed air is introduced into the polisher head to give tension to the dome-shaped portion, and a slurry-like abrasive is supplied to the polisher head and the object to be polished. These are rubbed together while rotating to effect mirror polishing.
[0004]
Further, a partial polishing method using a small dome-shaped elastic polishing body that is in contact with a part of a surface to be polished of a polishing object is known. In this partial polishing method, a maximum curvature is obtained from the shape of the surface to be polished, a dome-shaped elastic polishing body having a curvature larger than the maximum curvature is selected, and a part of the surface to be polished is rotated while rotating the elastic polishing body. Then, the entire surface to be polished is polished by scanning the entire surface to be polished with the elastic polishing body.
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. H11-77503
[Problems to be solved by the invention]
However, in the polishing performed by attaching a polishing pad to the surface of a hollow dome-shaped polisher head made of an elastic material, a non-axisymmetric aspheric surface is excellent in shape followability, but for example, a surface having a high surface roughness of about 2 nm. There is a problem that it cannot be finished with high accuracy.
[0007]
Further, the partial polishing method has a problem that a long polishing time is required because the entire polishing surface is polished by a small polishing head, and the manufacturing cost is high.
[0008]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a precision polishing tool capable of rapidly polishing a non-axisymmetric aspheric surface with high surface accuracy.
[0009]
Another object of the present invention is to provide a precision polishing method capable of rapidly polishing a non-axisymmetric aspheric surface with high surface accuracy.
[0010]
[Means for Solving the Problems]
The inventor of the present invention has conducted intensive studies to achieve the above object, and as a result, a conventional polishing method in which a polishing pad is attached to the surface of a hollow dome-shaped polisher head made of an elastic material disclosed in Patent Document 1 The reason that the optical mirror surface having the expected surface roughness could not be obtained was considered to be due to the polishing pad. Conventionally, a desired optical mirror surface may be obtained by modifying the surface of a polishing pad with sandpaper or the like and then performing a polishing operation, but this is inefficient. This polishing pad is usually in the form of a petal and has a function of holding a polishing liquid and the like, and a gap between protruding petals of the polishing pad functions as a passage for supplying abrasive grains and water and discharging polishing waste. It was considered to be a necessary member for mirror polishing.
[0011]
However, when the polishing was performed by directly applying a hollow dome-shaped polisher head made of an elastic material to the surface to be polished without attaching a polishing pad, this polisher head could not be expected to have a function of holding an abrasive. It was found that an optical mirror surface having the expected surface roughness was obtained. In addition, the surface roughness obtained by polishing is affected by the surface roughness of the elastic polishing body, and by setting the average value Ra of the surface roughness of the elastic polishing body to 0.1 μm or less, an optical mirror surface having sufficiently high surface accuracy can be obtained. It has been found that it can be formed. In this polishing method, the polishing is performed while pressing the dome-shaped elastic abrasive body against almost the entire surface to be polished, so that the elastic abrasive body uniformly deforms the entire surface to be polished while deforming following the curved surface of the surface to be polished. Therefore, the polishing rate is extremely high as compared with the partial polishing method.
[0012]
When the elastic polishing body, which is the portion for polishing the surface to be polished, is expanded in a dome shape or is formed of an elastic sheet formed in a dome shape, the range of polishing conditions such as the internal pressure of the elastic polishing body and the hardness of the elastic sheet is reduced. It becomes large, and appropriate polishing can be performed.
[0013]
In order to keep the internal pressure of the dome-shaped elastic polishing body constant, it is preferable to form a sealed space inside the dome-shaped elastic polishing body and provide a check valve for keeping the pressure in the sealed space constant.
[0014]
The average particle size of the abrasive is preferably in the range of 5 nm to 5 μm.
[0015]
Therefore, the invention according to claim 1 is characterized in that the elastic polishing body is made of an elastic material which expands in a dome shape or is formed in a dome shape and has an average surface roughness Ra of 0.1 μm or less; And a support jig provided with a mounting portion attached to a chuck of the polishing apparatus.
[0016]
According to a second aspect of the present invention, in the precision polishing tool according to the first aspect, the elastic polishing body is formed of an elastic sheet, and the support jig and the elastic polishing body form a sealed space. Provide precision polishing tools.
[0017]
According to a third aspect of the present invention, in the precision polishing tool according to the second aspect, a check valve connected to the sealed space, for introducing a pressurized fluid into the sealed space and maintaining the sealed state is provided on the support jig. Provided is a precision polishing tool that is attached to a polishing tool.
[0018]
According to a fourth aspect of the present invention, the surface to be polished and the elastic polishing body are respectively rotated while pressing the surface to be polished against the elastic polishing body expanded or formed into a dome shape, and the slurry-like polishing is performed. A precision polishing method, characterized in that a polishing agent is supplied to the elastic polishing body to polish the surface to be polished.
[0019]
According to a fifth aspect of the present invention, there is provided the precision polishing method according to the fourth aspect, wherein an average value Ra of the surface roughness of the elastic polishing body is 0.1 μm or less.
[0020]
The invention according to claim 6 provides the precision polishing method according to claim 4, wherein the abrasive has an average particle diameter of 5 nm to 5 μm.
[0021]
According to a seventh aspect of the present invention, in the precision polishing method according to any one of the fourth to sixth aspects, the elastic polishing body is formed of an elastic sheet, and a pressure is applied to an inner surface of the elastic sheet by a pressure fluid to thereby form the elastic polishing body. Provided is a precision polishing method characterized by polishing while applying tension to a sheet.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the precision polishing tool and the precision polishing method of the present invention will be described, but the present invention is not limited to the following embodiments.
[0023]
FIG. 1 is a cross-sectional view illustrating a precision polishing tool according to an embodiment of the present invention and a precision polishing method using the tool.
[0024]
This precision polishing tool 1 has a structure in which an elastic polishing body 3 is attached to a support jig 2. The support jig 2 is made of a metal such as stainless steel, and has a disk-shaped support jig main body 21 and a mounting portion 22 provided integrally with a lower surface center of the support jig main body 2 to be attached to a polishing apparatus. And a ring-shaped pressing member 23 separate from the supporting jig main body 21. The pressing member 23 is fixed to the outer peripheral surface of the upper surface of the support jig body 21 by a crimping jig (not shown).
[0025]
The elastic polishing body 3 is made of an elastic sheet and has a flat circular sheet shape or a hollow dome shape having a dome-shaped portion 32 provided with a ring-shaped flange portion 31 on the outer periphery as shown in FIG. It is formed in the shape of. The outer peripheral portion or the flange portion 31 of the elastic polishing body 3 is press-fitted like a packing between the outer peripheral surface of the upper surface of the support jig body 21 and the ring-shaped pressing member 23 so as to be attached to the support jig body 21. I have. Thereby, the outer peripheral portion or the flange portion 31 of the elastic polishing body 3 is pressed against the upper surface of the support jig main body 21 so that the space between the elastic polishing body 3 and the support jig main body 21 can form the sealed space 4. Has become.
[0026]
In addition, a pipe 5 that penetrates the support jig body 21 and introduces a pressure fluid into the sealed space 4 is provided, and the pipe 5 is provided with a check valve 6. The check valve 6 has a function of keeping the pressure of the pressurized fluid in the sealed space 4 constant. By introducing the pressurized fluid into the sealed space 4, the flat sheet-like elastic polishing body 3 can be expanded and formed into a dome shape. In addition, the elastic polishing body 3 formed in a dome shape can be given tension to maintain the dome shape. The shape of the hollow elastic abrasive body 3 composed of an elastic sheet can be changed to some extent by the pressure of the pressure fluid.
[0027]
The elastic polishing body 3 of such a precision polishing tool 1 is formed of the elastic sheet shown in FIG. 1 and is formed of an elastic material in a dome-shaped block in addition to a dome-shaped shape maintained by the internal pressure of the pressure fluid. Or a dome-shaped elastic sheet whose hollow portion is filled with another elastic material. The thickness of the elastic sheet is preferably 0.1 to 10 mm, particularly preferably 0.2 to 5 mm, JIS A hardness (type A durometer) 10 to 100, Young's modulus 10 ² to 10 ³ N · cm ⁻² , heat resistance temperature Preferably have physical properties of 100 ° C. or higher. The elastic sheet or elastic material is made of natural rubber, chloroprene rubber, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), rubber such as silicone rubber, fluorine rubber, thermoplastic resin such as polyethylene, nylon, or styrene. And urethane-based thermoplastic resin elastomers.
[0028]
Further, in the precision polishing tool 1 of the present invention, the average value Ra of the surface roughness of the outer surface of the elastic polishing body 3 is 0.1 μm or less, preferably 0.09 μm or less. The lower the average value Ra of the surface roughness, the better. If the surface roughness of the elastic polishing body 3 is rougher than this, it becomes difficult to polish the surface to be polished with sufficient surface accuracy. In order to set the surface roughness of the elastic polishing body to such a surface roughness, for example, a method of transferring the surface roughness of the mold to the elastic sheet by setting the surface roughness of the mold for forming the elastic sheet to 0.1 μm or less. Alternatively, a method of polishing the surface of the elastic sheet can be employed. The surface of the elastic abrasive body may be worn during use as the abrasive body, resulting in the above surface roughness.
[0029]
The elastic polishing body 3 used in the present invention preferably has a larger area than the surface to be polished. This makes it possible to perform polishing by bringing the elastic polishing body 3 into contact with almost the entire surface to be polished. In addition, by making the area of the elastic polishing body larger than the area of the surface to be polished, the peripheral speed of the rotation of the elastic polishing body is increased to improve the polishing speed, and the shape following property of the elastic polishing body is improved. Can be done. It is desirable that the diameter of the dome-shaped portion of the elastic polishing body be 1.1 to 10 times, preferably 1.5 to 5 times the diameter of the surface to be polished.
[0030]
As the surface to be polished to be subjected to the precision polishing tool 1 and the precision polishing method of the present invention, anything requiring mirror polishing is to be polished. For example, convex and concave surfaces of various lenses having curved surfaces such as spherical surfaces, axisymmetric aspheric surfaces, and non-axisymmetric aspheric surfaces, molds, optical products, etc. are applicable, and materials such as plastic, glass, carbide, and steel are limited. There is no.
[0031]
A precision polishing method using the precision polishing tool 1 will be described. As shown in FIG. 1, the elastic polishing body 3 having a predetermined thickness, hardness, dome curvature, and the like selected is mounted on the support jig 2. A pressure fluid such as compressed air is introduced from a pipe 5 into a sealed space 4 between the elastic polishing body 3 and the support jig body 2 via a check valve 6 through a check valve 6. The pressure of the pressure fluid at that time is selected so that the elastic polishing body 3 uniformly contacts the entire surface of the workpiece 7 to be polished. A polishing pad is not attached to the elastic polishing body 3. When the pressure in the sealed space 4 reaches a predetermined pressure, the introduction of the pressure fluid is stopped, and the precision polishing tool 1 is mounted on the chuck of the polishing apparatus via the mounting portion 22.
[0032]
One of the objects to be polished 7 is fixed to the mounting jig 8 on the side opposite to the surface to be polished via a bonding material such as wax, and mounted on the chuck of the polishing apparatus via the mounting jig 8.
[0033]
Then, the elastic polishing body 3 is directly pressed onto almost the entire surface to be polished of the object 7 to be polished, and a predetermined load is applied to the object 7 or the precision polishing tool 1 to apply the polishing pressure to the predetermined position. The object to be polished 7 is rotated at a predetermined number of revolutions while rotating at a predetermined number of revolutions, and rubs against each other. Polishing is performed while a slurry 10 containing an abrasive is supplied from the nozzle 9 to the surface of the elastic abrasive body 3.
[0034]
In this case, the internal pressure applied to the elastic polishing body 3 is, for example, 0.2 to 1.2 kgf / cm ² , the rotation speed of the elastic polishing body 3 is, for example, 10 to 200 rpm / min, and the rotation speed of the workpiece 7 is, for example, The polishing can be performed under the polishing conditions of 10 to 100 rpm / min and the polishing pressure of, for example, 1 to 8 kgf.
[0035]
The precision polishing tool 1 of the present invention uses the elastic polishing body 1 having a predetermined surface roughness and presses the elastic polishing body 3 on almost the entire surface to be polished of the work 7 to be polished. Are rotated to supply a slurry-like abrasive to the elastic polishing body 3 to polish the surface to be polished, so that the elastic polishing body 3 follows the curved surface of the surface to be polished, for example, the average value Ra of the surface roughness. Can quickly obtain a mirror-polished surface of about 2 to 10 nm.
[0036]
The reason why the polishing can be rapidly performed with extremely high surface accuracy using the elastic polishing body 3 having a smooth surface without using a polishing pad is not clear. The average value Ra of the surface roughness of the rubber sheet constituting the elastic abrasive body measured by the surface roughness meter is about 0.0786 μm to 0.0857 μm, but about 0.5 μm for those not used for polishing. There are protrusions and depressions of up to 1.5 μm. In the one used for polishing, the average value Ra of the surface roughness is reduced to about 0.064 μm, and fine irregularities of about 0.25 μm to 0.5 μm are present. It is considered that the fine irregularities hold the abrasive having an average particle size of about 1 μm and are a path for the cut fine particles.
[0037]
As a polishing apparatus to which the precision polishing tool 1 is attached, means for rotating the workpiece 7 at a predetermined rotation speed, means for rotating the precision polishing tool 1 at a predetermined rotation speed, What is necessary is just to have a pressurizing means for bringing the polishing object 7 into close contact with the predetermined polishing pressure.
[0038]
For example, the polishing head 101 of the NC controlled partial polishing apparatus 100 shown in FIG. 2 may be replaced with the precision polishing tool 1 of the present invention. This partial polishing apparatus 100 performs polishing by controlling the polishing axis so as to be directed in the normal direction to the processing surface by 4-axis NC control. As the polishing head 101, for example, a polishing head with a polishing pad attached to the surface of a spherical elastic body is used. The partial polishing apparatus 100 includes an X-axis table 102 for controlling the horizontal position of the work, a tilt table 103 for controlling the inclination of the work 110, and a Z-axis for controlling the vertical position of the polisher head 101. Polishing is performed on four axes of a lifting table 104 and a rotary table 105 that controls the rotation position of the work 110. The polishing head 101 is driven to rotate while being pressed against the work 110 with a predetermined load by pressure control of the air cylinder 106.
[0039]
For example, the polishing head 101 of the partial polishing apparatus 100 is replaced with the precision polishing tool 1 of the present invention, the tilt table 103 is set horizontal, and the rotation axis of the polishing head 101 is set in the vertical direction, and the work 110 is rotated at a predetermined rotation speed. At the same time, the polishing can be performed by a method in which the precision polishing tool 1 is pressed against a workpiece with a predetermined load while being rotated at a predetermined rotation speed.
[0040]
In the description of the precision polishing tool, a check valve is used to keep the pressure in the sealed space constant.However, a passage that can introduce a pressure fluid is provided at the center of the mounting portion, and a communication with the pressure fluid side is provided. Thereby, the inside of the sealed space may be maintained at a constant pressure. In the above description, the polishing is performed while applying the elastic polishing body to almost the entire surface to be polished. However, the polishing may be performed while applying the elastic polishing body to a part of the surface to be polished.
[0041]
【Example】
Polishing was performed by replacing the polisher head of the NC controlled partial polishing apparatus shown in FIG. 2 with the precision polishing tool of the present invention.
[0042]
<Example 1>
The workpiece is made of an optical glass lens having a shot S-3 and an outer diameter of 40φ, and the convex side of the optical glass lens is aspherically processed by a grinding device, the concave side is spherically processed, and the optical mirror surface (average surface roughness Ra: 0.003 μm), and the convex surface was used as the surface to be polished.
[0043]
The concave side of this optical glass lens was melted with a drier using wax and bonded to a mounting jig.
[0044]
As the elastic abrasive body 3, an NBR rubber sheet having a thickness of 1 mm and a hardness of HS90 formed in a 120R dome shape was used. The average value Ra of the surface roughness of the rubber sheet is about 0.0786 to 0.0857 μm.
[0045]
The abrasive was prepared as a slurry having a specific gravity of 1.07 ± 0.01 using cerium oxide (cerox average particle diameter 1 μm) and pure water as a diluent.
[0046]
Polishing conditions were as follows: polisher rotation speed: 30 rpm, work rotation speed: 60 rpm, polishing load: 3.5 kgf, polishing time: 5 min.
[0047]
The average value Ra of the surface roughness of the convex surface of the optical glass lens after polishing was 0.0027 μm. The average value Ra of the surface roughness of the elastic polishing body used for 3 hours was about 0.064 μm.
[0048]
<Comparative Example 1>
The same elastic polishing body as in Example 1 was used, and a cerium sheet having a thickness of 0.8 mm was attached as a polishing pad to the surface thereof.
[0049]
Polishing was performed using the same NC polishing apparatus and the same polishing agent as in Example 1 under the same polishing conditions and for the same time.
[0050]
The surface roughness Ra of the convex surface of the optical glass lens after polishing was 0.0193 μm.
[0051]
<Example 2>
The workpiece is made of an optical glass lens having a material of BK-7 and an outer diameter of 40φ. The convex side is aspherically processed by a grinding device, the concave side is spherically processed, and the optical mirror surface (average surface roughness Ra: 0) .003 μm), and the convex surface was used as the surface to be polished.
[0052]
Polishing was performed using the same elastic polishing body as in Example 1, using the same NC polishing apparatus as in Example 1, using the same abrasive, and under the same polishing conditions for the same time. As a result, the average surface roughness Ra of the convex surface of the optical glass lens after polishing was 0.0077 μm.
[0053]
<Comparative Example 2>
Using the same workpiece as in Example 2, using an elastic polishing body to which a cerium sheet having a thickness of 0.8 mm was adhered as a polishing pad as in Comparative Example 1, using the same NC polishing apparatus as in Example 1, Polishing was performed under the same polishing conditions for the same time using an abrasive. As a result, the average value Ra of the surface roughness of the convex surface of the optical glass lens after polishing was 0.0114 μm.
[0054]
<Example 3>
The workpiece is made of an optical glass lens having a material of BK-7 and an outer diameter of 28φ, the convex side of which is aspherically processed by a grinder, the concave side of which is spherically processed by a grinder, and the optical mirror surface (surface roughness average Ra). : 0.003 μm), and the convex surface was used as the surface to be polished.
[0055]
Polishing was performed using the same elastic polishing body as in Example 1, using the same NC polishing apparatus as in Example 1, using the same abrasive, and under the same polishing conditions for the same time. As a result, the average value Ra of the convex surface roughness of the optical glass lens after polishing was 0.0068 μm.
[0056]
<Comparative Example 3>
Using the same workpiece as in Example 3, using an elastic polishing body to which a cerium sheet having a thickness of 0.8 mm was adhered as a polishing pad as in Comparative Example 1, using the same NC polishing apparatus as in Example 1, Polishing was performed under the same polishing conditions for the same time using an abrasive. As a result, the average value Ra of the convex surface roughness of the polished optical glass lens was 0.0161 μm.
[0057]
【The invention's effect】
ADVANTAGE OF THE INVENTION The precision polishing tool of this invention can obtain | require a highly polished surface with high surface precision quickly by directly grind | polishing a to-be-polished surface with an elastic polishing body, without a polishing pad.
[0058]
According to the precision polishing method of the present invention, a polished surface with high surface accuracy can be quickly obtained by directly polishing the surface to be polished with an elastic polishing body without using a polishing pad.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a precision polishing tool according to an embodiment of the present invention and a precision polishing method using the same.
FIG. 2 is a schematic configuration diagram illustrating an outline of an NC-controlled partial polishing apparatus.
[Explanation of symbols]
1: precision polishing tool 2: support jig 21: support jig main body 22: mounting portion 23: holding jig 3: elastic polishing body 4: sealed space 5: piping 6: check valve 7, polishing object 8: mounting Jig 9: Nozzle 10: Slurry containing abrasive

Claims (7)

An elastic polishing body having an average surface roughness Ra of 0.1 μm or less, which is formed of an elastic material that expands in a dome shape or is formed in a dome shape; a chuck for the polishing device that supports the elastic polishing body; And a support jig having a mounting part attached to the tool. The precision polishing tool according to claim 1,
The precision polishing tool, wherein the elastic polishing body is formed of an elastic sheet, and the support jig and the elastic polishing body form a sealed space. The precision polishing tool according to claim 2,
A precision polishing tool connected to the sealed space, wherein a check valve for introducing a pressurized fluid into the sealed space and maintaining the seal is attached to the support jig. The surface to be polished and the elastic polishing body are rotated while pressing the surface to be polished against the elastic polishing body expanded or shaped like a dome, and a slurry-like abrasive is supplied to the elastic polishing body. And polishing the surface to be polished. In the precision polishing method according to claim 4,
A precision polishing method, wherein the average value Ra of the surface roughness of the elastic polishing body is 0.1 μm or less. In the precision polishing method according to claim 4,
A precision polishing method, wherein the abrasive has an average particle size of 5 nm to 5 μm. The precision polishing method according to any one of claims 4 to 6,
The precision polishing method, wherein the elastic polishing body is formed of an elastic sheet, and a pressure is applied to an inner surface of the elastic sheet with a pressure fluid to grind the elastic sheet while applying tension thereto.

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