JPH08290356A - Abrasive and grinding method - Google Patents

Abstract

PURPOSE: To provide an abrasive capable of compatibly achieving the high grinding speed and the excellent grinding precision, and a grinding method using the abrasive. CONSTITUTION: An abrasive has the composition consisting of, by weight, 85-50% matrix of polyurethane resin whose Shore hardness specified by ASTM-D2240 is D60-83, and 15-50% abrasive grains diffused in the matrix, the expansion ratio being 2-17 times. The abrasive is stuck to an upper surface plate 1 and a lower surface plate 2, and used to grind each face of a work 5 to be ground which is stored in a hole of a carrier 4 between the surface plates.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abrasive material and a polishing method suitable for precision polishing of a metal such as an aluminum substrate for a hard disk of a computer, a hard plastic, and an object to be polished such as an optical component such as a lens. .

[0002]

2. Description of the Related Art Conventionally, in polishing an aluminum substrate for a hard disk of a computer, a polishing apparatus having a carrier 4 arranged between an upper surface plate 1 and a lower surface plate 2 as shown in FIG. 1 has been widely used. Has been. The carrier 4 of this polishing apparatus is, for example, a disk-shaped carrier, and has a hole for holding the aluminum substrate 5. The outer periphery of the carrier 4 is configured to rotate and revolve by meshing with an internal gear and a side gear (not shown). Grinding stones 3 are attached to the upper and lower surface plates 1 and 2, respectively, and the upper and lower surface plates 1 and 2 are normally configured to rotate in mutually opposite directions.

The carrier 4 having the aluminum substrate 5 housed in the hole is rotated and revolved while the grindstone 3 and the aluminum substrate 5 are rotated.
While the polishing liquid is being supplied from the upper surface plate 1 during this period, the upper and lower surface plates 1 and 2 are rotated in opposite directions to polish the aluminum substrate 5.

[0004]

In this polishing process, the surface of the aluminum substrate 5 obtained after polishing is a highly accurate smooth surface in response to the recent demand for increasing the capacity of computer memory. There is a strict demand for quality such as cutting off the peripheral edge, so-called less surface sag. On the other hand, there is an increasing economic demand for increasing the polishing rate to improve the productivity during polishing and to provide the aluminum substrate 5 at low cost. Therefore, it is an important issue to satisfy these requirements in the polishing process.

By the way, in JP-A-60-80565 and JP-A-62-297072, when abrasive grains are mixed in polyurethane resin, a grindstone having elasticity is obtained, and these grindstones have unevenness. It is disclosed that the polishing surface of a certain object to be polished can be well followed to perform efficient polishing. However, although the grindstones disclosed in these prior arts are suitable for polishing hard-to-grind materials such as titanium nitride-based cermets and high hardness materials such as steel materials with low accuracy, they are not suitable for computer memory members and optical It is not suitable for the purpose of polishing a low hardness material such as an aluminum substrate 5 used as a member or the like with high accuracy and smoothness.

Further, Japanese Patent Laid-Open No. 4-256581 discloses that
As the abrasive 3 for the aluminum substrate 5, a grindstone in which abrasive grains are dispersed in a synthetic resin composed of a thermosetting resin and a polyvinyl acetal resin and these abrasive grains are bonded is disclosed. However, since the dispersion density (blending amount) of the polishing abrasive grains is set to be extremely large in order to improve the polishing rate, the dispersion of the polishing abrasive grains becomes non-uniform, and a uniform polishing effect can be exerted. There is a problem that there is no.

The present invention has been made in order to solve the above-mentioned problems in the conventional abrasive, and the abrasive 3
Even if the compounding amount of polishing abrasive grains is kept low in order to improve the moldability of No. 3, it is possible to polish the object 5 to be polished such as an aluminum substrate with high accuracy, and the polishing material 3 having a good polishing rate is used. An object is to provide a polishing method. In addition, it is also an object to provide an abrasive having excellent stability of the above polishing rate and polishing accuracy even if continuous polishing is performed for a long time.

[0008]

In order to achieve the above-mentioned object, in the present invention, ASTM (American standa
rd for Testing and Materials) -D2240 (198
85-50% by weight matrix of polyurethane resin having a hardness of Shore D60-83 specified in May, 2006)
And polishing abrasive grains 15 to 5 dispersed in the matrix
0% by weight, and an expansion ratio of 2 to 17 times, especially an expansion ratio of 6 to 1
Two times more abrasive is provided.

Further, in the present invention, the above-mentioned abrasives are respectively provided on the surfaces of the upper surface plate and the lower surface plate which are opposed to each other, and a carrier for holding an object to be polished is arranged between the abrasives. A polishing method is provided, which comprises rotating a lower platen with respect to an object to be polished to polish both surfaces of the object to be polished.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The polyurethane resin forming the matrix may be any one that is obtained by reacting an active hydrogen-containing compound with an isocyanate compound and is generally used as a polyurethane material for foams. Here, as the active hydrogen-containing compound, those obtained by mixing a polyol and a chain extender and exhibiting a liquid state at room temperature can be used. If necessary, water, a blowing agent such as CFC, a catalyst such as triethylenediamine or triethylamine, a silicone surfactant (foam stabilizer), and the like may be added thereto.

The above-mentioned polyol has two or more, preferably three functional groups (OH group or NH ₂ ) in one molecule.
A group having a molecular weight of 1000 to 4000 is suitable, and examples thereof include polyethylene adipate, polypropylene glycol, polyethylene glycol and the like. As the chain extender,
Contains two or more functional groups in one molecule and has a molecular weight of 50-
Those of 5000 are preferable, and, for example, diethylene glycol, trimethylpropane and diaminodiphenylmethane can be mentioned as preferable examples.

Further, as the above-mentioned isocyanate compound,
Contains two or more isocyanate functional groups in one molecule,
Those that are liquid at room temperature or slightly heated are preferable, and for example, 4,4′diphenylmethane diisocyanate is a preferable example. Examples of the abrasive grains dispersed in the matrix include cerium oxide, diamond, cubic boron nitride, alumina, silica, silicon carbide, etc., but both a high polishing rate and high-precision smoothness of the polished surface are achieved. In consideration of the above, alumina, silica, and silicon carbide are preferable.

In order to disperse the abrasive grains in the matrix, for example, a predetermined amount of the abrasive grains is previously charged in a chemically stable active hydrogen-containing compound and sufficiently mixed and dispersed using a stirrer or the like. It is preferable to mix the above-mentioned isocyanate compound here. In the abrasive of the present invention, the reason why the hardness of the polyurethane resin as the matrix is limited to Shore D60 to D83 is that when the hardness is less than Shore D60, the hardness as the abrasive is too low, and as shown in FIG. In addition, due to the pressure applied at the time of polishing, the object to be polished 5 sinks too much into the polishing material 3 and the vicinity of the outer peripheral surface (peripheral part) of the object to be polished 5 is easily scraped. This is because the thickness becomes thinner, so-called surface sagging occurs and the quality is impaired.

If the hardness exceeds Shore D83, the elastic force of the matrix is poor, and therefore the effect of the abrasive grains is greatly exerted, and the smoothness of the object 5 to be polished after polishing is lowered. This is also to impair the quality. The hardness of the polyurethane resin is obtained by blending a polyol and a chain extender in a functional group equivalent ratio in the range of polyol: chain extender = 1: 2 to 1:25 to obtain an active hydrogen-containing compound. It is possible to adjust the shore D60 to 83 by blending the hydrogen-containing compound and the isocyanate in a functional group equivalent ratio in the range of active hydrogen-containing compound: isocyanate = 1: 1.04 to 1: 1.2. is there.

The reason why the expansion ratio of the polyurethane resin as the matrix is limited to 2 to 17 times is that if the expansion ratio is less than 2 times, the cell structure becomes too fine and the polishing characteristics deteriorate. Because it becomes
If it exceeds 7 times, most of the resulting abrasive will be occupied by bubbles and its strength will decrease,
This is because problems such as damage to the abrasive material occur during the polishing process. The expansion ratio is preferably 6 to 12 times.

When the expansion ratio is less than 6 times, no deterioration in polishing characteristics is observed, but when continuous polishing is performed for a long time, the polishing material itself or the object to be polished, for example, may be used. There is a problem that shavings of an aluminum substrate are filled in air bubbles and clogging is likely to occur, and polishing characteristics become unstable, and when it exceeds 12 times, there is a fear that the above-mentioned strength of the polishing material is lowered. There is.

The expansion ratio referred to here is the bulk density calculated from the weight and size of a resin composition containing abrasive grains which is used to produce a non-foamed cured product without adding a foaming agent. and D _1, the resin composition obtained by dispersing the same abrasive grains by blending a foaming agent to produce a cured product obtained by foaming, the bulk density calculated from the weight and dimensions is taken as D _2, D ₁ /
The value represented by D ₂ .

The expansion ratio can be adjusted 2 to 17 times by changing the amount of the foaming agent, for example, the amount of water in the range of 0.06 to 0.6% by weight based on the total weight. is there. Further, in the abrasive material of the present invention, the reason why the amount of the abrasive grains dispersed in the matrix of the polyurethane resin is limited to 15 to 50% by weight based on the total weight is that the amount of the abrasive grains is less than 15% by weight. In this case, the polishing rate becomes slow and desired productivity cannot be obtained.
On the other hand, if it exceeds 50% by weight, the fluidity of the liquid polyurethane resin that becomes the matrix is significantly reduced during the production of the abrasive, which makes it difficult to produce the abrasive having the desired shape. .

In the polishing method of the present invention, the above-mentioned abrasive 3 is placed on the upper surface plate 1 and the lower surface plate 2 of the polishing apparatus shown in FIG. 1, and the carrier 4 holding the object to be polished 5 therebetween. The upper and lower stools 1 and 2 described above may be rotated with respect to the object 5 to be polished. At this time, a conventional polishing liquid containing a surfactant as a main component may be used together. The abrasive of the present invention is most suitable for polishing an aluminum substrate, but the object to be polished is not limited to this, and various substrates, metals, plastic molded products, and lenses for which precise polishing is required. It can be used for polishing an object to be polished such as optical parts.

[0020]

【Example】

Examples 1 to 12, Comparative Examples 1 to 7 Polyether polyol having a molecular weight of 2400, an OH value of 47, and a functional number of 2 to 3 (manufactured by Sumitomo Bayer Co., Ltd., trade name: Desmophen 0331), a molecular weight of 450, an OH value of 376, and a functional group number of 3 Chain extender A: Polyol (Sumitomo Bayer,
Product name: Sumifene ™), molecular weight 62, OH number 181
0, a chain extender having 2 functional groups B: ethylene glycol, an isocyanate compound having an isocyanate (NCO) group content of 22.7% (Sumitomo Bayer Co., Ltd., trade name: Sumidule P
F), water, an amine catalyst (manufactured by Sankyo Air Products Co., Ltd., trade name: Dubco 33LV), a silicone foam stabilizer (manufactured by Nippon Unicar Co., Ltd., trade name: L-5420) and abrasive grains are shown in Tables 1 to 3, respectively. The liquid resin compositions having various compositions were prepared by mixing in the proportions (parts by weight) shown.

Next, these liquid resin compositions were poured into a mold of a predetermined size and left at room temperature for 30 to 60 minutes to foam and simultaneously cure. Then, the thin film on the surface of each of the obtained cured products is removed using a grinder or a slicer, and a bubble structure (irregularities) is exposed on the surface.
To obtain an abrasive. Using these abrasives, with a polishing machine shown in Fig. 1, diameter 95mm (inner diameter 25mm), thickness 1.0mm
The aluminum substrate 5 of No. 1 was polished as follows.

Various abrasives 3 are attached to the surfaces of the upper and lower surface plates 1 and 2 with an adhesive tape, and the aluminum substrate 5 is housed in the hole provided in the carrier 4, so that the carrier 4 is rotated and revolved. On the other hand, the upper and lower surface plates 1 and 2 were rotated in opposite directions to simultaneously polish both surfaces of the aluminum substrate 5. The polishing conditions at this time are as follows. [Polishing conditions] Surface pressure of the upper and lower surface plates 1 and ² : 700 g / cm ² Rotational speed of the upper and lower surface plates 1 and 2 and the carrier 4: 20 rpm On the other hand, in order to examine the hardness of the polyurethane resin which is the matrix of the abrasive material 3, Of the liquid resin compositions shown in Tables 1 to 3, only a polyol, a chain extender, an isocyanate compound and a catalyst were respectively mixed to produce a cured product of a polyurethane resin component alone which was cured under the same conditions, and a Shore D hardness was obtained. The hardness was measured using a meter. Table 1
3 to 3 to produce a cured product by removing water from the liquid resin composition without foaming, and to obtain a polishing material 3 having a bulk density D1 determined from its volume and weight and a combination of Tables 1 to 3. Using the bulk density D2 obtained from the volume and the weight, D1 / D2
The foaming ratio was determined by the following formula.

Further, the ratio (% by weight) of the polyurethane resin and the abrasive grains in each of the obtained abrasives was calculated by calculating the respective weight ratios with respect to the total weight of the abrasive 3.
Next, at the time of polishing, the thickness of the aluminum substrate 5 ground per minute was measured, and the polishing rate was calculated. For the smoothness of the surface of the aluminum substrate 5, a surface roughness measuring instrument (manufactured by Wyco, USA, trade name: Toppo 3D type) was used, and for surface sag, a flatness measuring instrument (Trovel, USA: Supersort). 3/5 type). The results are shown in Tables 1 to 3.

The smoothness measured here means a value (R) calculated by the following equation. That is, when the roughness curve representing the irregularities on the surface of the aluminum substrate 5 is f (x) and the length of the measurement range is L, the following formula:

[0025]

[Equation 1]

It is a value indicated by In other words, it is an average value obtained by integrating the unevenness of the surface of the aluminum substrate 5 with a certain line and integrating it, and dividing the integrated value by the length of the measurement range. Further, the surface sag is, as shown in FIG. 3, from the peripheral edge portion 5a of the aluminum substrate 5 toward the center portion 3.
A point A at a surface position of 264 mm and a point B at a surface position of 0.635 mm are connected to form a line 1, and a line 2 parallel to the line 1 and contacting the surface of the aluminum substrate 5 at a point C is drawn. Sometimes, it means the distance between the line 1 and the line 2. That is, the larger this value, the larger the surface sag.

A conventional grindstone (PVA-WP, J manufactured by Fujimi Incorporated) was used instead of the above-mentioned abrasive.
The aluminum substrate was polished under the same conditions as those of the example by using the WP type) to obtain a conventional example. Also in the case of this grindstone, the polishing rate, smoothness, and surface sag were determined in the same manner as in the examples. The above results are collectively shown in Tables 1 to 3.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

As is apparent from Tables 1 to 3, Examples 1 to 1
By using 12 abrasives, the polishing rate is faster (2.6 μm / min or more), the polishing accuracy is higher (smoothness 9.0 × 10 ⁻³ μm or less, surface sag 7. 6 × 10 ^-2 μ
m or less). On the other hand, in Comparative Examples 1, 6, and 7, the polyurethane resin had a Shore D hardness of 6
Since it is as low as less than 0, a high polishing rate cannot be obtained, and Comparative Example 6
Since the hardness is too low, the polishing hardly progresses, and the state before the polishing remains on the aluminum substrate 5. Further, the pressure applied during the polishing process causes the aluminum substrate 5 to sink more than necessary into the polishing material 3, so that the surface sag of the aluminum substrate 5 is significantly increased. Further, in the case of Comparative Example 2, since the Shore D hardness of the polyurethane resin exceeds 83 and has a high hardness, the aluminum substrate 5 after polishing is remarkably inferior in smoothness.

Further, in the case of Comparative Example 3, since the content of the abrasive grains in the abrasive was too small, the polishing hardly proceeded. In the case of Comparative Example 4, the content of the abrasive grains in the abrasive was too small. There are too many abrasives to be manufactured. In the case of Comparative Example 5, the foaming ratio is 1.6 times, which is too small, so that the desired polishing rate cannot be obtained. Examples 13 to 25, Comparative Examples 8 to 16 Indicated ratio of each component used in Examples 1 to 12 (parts by weight)
Were mixed to prepare liquid resin compositions of various compositions, and using this, abrasives were manufactured in the same manner as in Examples 1-12.
With respect to each of these abrasives, the hardness (Shore D) of the polyurethane resin, the expansion ratio, and the ratio (% by weight) of the polyurethane resin and the abrasive grains were measured in the same manner as in Examples 1-12.

Next, each polishing material was adhered to the upper and lower surface plates 1 and 2 of the polishing apparatus shown in FIG. 1, and 12 aluminum substrates 5 were accommodated in the holes of the carrier 4 for each batch. 1 to
100 batches of polishing processing were performed under the same polishing conditions as 12. The polishing rate, smoothness, and surface sag of the obtained aluminum substrate were measured, and the average value and standard deviation of each were obtained.
The above results are collectively shown in Tables 4 to 7.

[0034]

[Table 4]

[0035]

[Table 5]

[0036]

[Table 6]

[0037]

[Table 7]

As is clear from Tables 4-7, Example 13
When polishing is performed using the abrasives of ~ 25, a high polishing rate (2.6 μm / min or more) and a high polishing accuracy (smoothness of 9.0)
X10 ⁻³ μm or less and surface sag 7.6 × 10 ⁻² μm or less). Moreover, even after 100 batches of continuous polishing, the standard deviation of the polishing rate was 0.81 μm / min or less, the standard deviation of the smoothness was 0.55 × 10 ⁻³ μm or less, and the standard deviation of the surface sag was 0.19. It is less than × 10 ^-2 µm, and the variation is small in all cases, and polishing is progressing in a stable state.

On the other hand, in the case of the abrasive of the comparative example, although the high polishing rate and the high polishing accuracy are shown,
Nos. 9, 11, 12, 14, and 15 have a foaming ratio of less than 6 times, so clogging occurs due to the accumulation of polishing dust in the bubbles, and after 100 batches of continuous polishing, Has a standard deviation of polishing rate of 0.95 μm / min or more, a standard deviation of smoothness of 2.80 × 10 ⁻³ μm or more, or a standard deviation of surface sag of 1.0 × 10 ⁻² μm or more. Sometimes occurs, and the polishing process is unstable. Further, in Comparative Examples 10, 13, and 16, the expansion ratio is too large, and therefore, there is a situation in which it breaks during polishing.

After polishing for 100 batches, the abrasive was removed from the apparatus and the appearance was observed. As a result, in Examples 15, 18 and 21, the surface edge (peripheral edge) was 1 mm.
It was lacking to some extent. It is considered that this is because the foaming ratios of the abrasives of these examples were as large as 15 times.

[0041]

As is apparent from the above description, claim 1
The abrasive 3 is composed of 85 to 50% by weight of a matrix of polyurethane resin having a hardness of Shore D60 to 83 defined by ASTM-D2240, and 15 to 50% by weight of abrasive grains dispersed in the matrix. Since the expansion ratio is 2 to 17 times, even if the compounding amount of polishing abrasive grains is suppressed to be low in order to improve the moldability of the polishing material, it is possible to realize polishing processing in which a high polishing rate and high polishing accuracy are compatible. You can In particular, if the expansion ratio is set to 6 to 12, even if continuous polishing is carried out for a long time, there is no possibility that the polishing material will be damaged in the polishing process, and further polishing rate, smoothness, surface sag, etc. All the characteristics are excellent, and stable polishing can be realized.

In the polishing method of claim 3, the polishing material 3 of claim 1 is provided on the surfaces of the upper surface plate 1 and the lower surface plate 2 facing each other, and the object 5 to be polished is held between the polishing materials 3. The carrier 4 is disposed, and the upper and lower surface plates 1 and 2 and the workpiece 5 are polished.
Since the carrier 4 for holding is rotated to polish both sides of the object to be polished 5, the object to be polished can be polished at a high polishing rate and with high polishing accuracy, and even in continuous polishing for a long time It can be polished with stable properties.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of a polishing apparatus.

FIG. 2 is a partial cross-sectional view of FIG.

FIG. 3 is a cross-sectional view of an aluminum substrate for explaining the definition of the surface sag that has been removed in the embodiment.

[Explanation of symbols]

 1 Upper surface plate 2 Lower surface plate 3 Abrasive material 4 Carrier 5 Object to be polished (aluminum substrate) 5a Peripheral part of aluminum substrate

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area C08L 75/04 NFY C08L 75/04 NFY // (C08G 18/08 101: 00)

Claims (3)

[Claims] 1. A foam comprising a polyurethane resin matrix 85 to 50% by weight having a hardness of Shore D60 to 83 defined by ASTM-D2240, and 15 to 50% by weight of abrasive grains dispersed in the matrix. A polishing material having a magnification of 2 to 17 times. 2. The abrasive according to claim 1, wherein the expansion ratio is 6 to 12 times. 3. The polishing material (3) according to claim 1 is provided on the facing surfaces of an upper surface plate (1) and a lower surface plate (2), respectively, and an object to be polished is provided between the polishing material (3). A carrier (4) holding (5) is arranged, and the upper and lower surface plates (1, 2) are arranged.
Is rotated with respect to the object to be polished (5) to polish both surfaces of the object to be polished (5).