JP2015208818A - Polishing tool and polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing tool capable of reducing a spinout of a polishing object material in processing, capable of also coping with a polishing surface of the large area, and capable of fixed abrasive grain processing, by simultaneously realizing high processing efficiency, while maintaining a high processing surface quality (scratch free and high shape precision).SOLUTION: A polishing tool comprises a first elastic layer formed of an elastic body having ASKER C hardness of 40 or less and a plurality of projection parts projectingly provided on the opposite side of the first elastic layer from a flat plate part and having the tip positioned on the same plane, and is constituted by successively laminating a second elastic layer being 60-77 in a value for expressing flexibility measured by using an ASKER C rubber harness gauge and a polishing sheet installed on the plane by one surface and fixing a plurality of abrasive grains to the other surface, on an opposite side surface of the projection part forming side of the flat plate part.

Description

  The present invention relates to a polishing tool for finishing hard and brittle materials such as glass, ceramics, and silicon, and a polishing apparatus equipped with such a polishing tool.

  Polishing using loose abrasive grains is performed to flatten parts made of various hard and brittle materials such as silicon wafers and glass disks. While this flattening process can provide good polished surface roughness, it has been pointed out that problems such as warpage, drooling, surface stepping, and the like are likely to occur and the machined surface shape accuracy deteriorates. In order to improve the flatness of the polishing surface, a hard resin material is used for the polishing tool, mainly the polishing pad, and further, the flatness of the surface of the polishing pad is improved by a dressing technique in order to suppress contact between pieces. It has responded by.

  However, in recent years, with the increase in wafer size, the limit of improvement has been seen only by the dressing technique on the surface of the polishing pad. In addition, discharge of waste liquid or the like that occurs when loose abrasive grains are used is another issue of environmental impact. On the other hand, the development of fixed abrasive processing tools, such as abrasive tapes, that can achieve excellent surface roughness equivalent to conventional polishing finishes with little waste liquid, and that can easily achieve high shape accuracy in various fields. It is active. In addition to the line contact progressive tape polishing method using an abrasive tape, a processing method using an abrasive sheet (ultra-precision abrasive sheet) illustrated in FIG. 10 is also widely performed.

  In the example shown in FIG. 10, the polishing sheet 10 formed by fixing abrasive grains on one surface (polishing surface) of a sheet (including a film) is fixed on a base substrate (surface plate) 5. Yes. Further, the workpiece (workpiece) 20 is rotated by a motor or the like (not shown) via a shaft 8 provided above the base substrate 5, and in this example, a head portion that can be moved up and down. 6 is attached. Also, unlike this example, a polishing method with a reverse layout in which the polishing sheet 10 is arranged on the upper side and the material 20 to be polished is fixed on the base substrate 5 below the polishing sheet 10 is also known.

In the case of such a polishing method, the following problems may occur.
(1) Per edge at the edge portion of the material to be polished As a typical problem, the surface to be polished of the material to be polished 20 is in contact with the polishing surface of the polishing sheet 10 as shown in FIG. "Per piece" is mentioned. Although the same occurs with a polishing pad in loose abrasive processing, it is difficult to achieve a solution by a dressing technique unlike a polishing pad in the case of a polishing sheet. For this reason, various devices have been devised on the polishing apparatus side in order to solve this problem. As an example, a technology to attach a universal joint-shaped air chamber to the rotating spindle has been developed, and with this member, the polished surface of the material to be polished follows the polished surface of the polishing tool (grinding stone, polishing sheet). To do. However, if the material to be polished is large, it is difficult to completely eliminate the contact.

  On the other hand, as a method for attaching the polishing sheet, a method has been proposed in which the polishing sheet is not directly attached to the base substrate but is attached via a backing material such as a sponge-like material. However, with this method, it is very difficult to select the hardness of the backing material. If the backing material is too soft, pressure during polishing is not applied, and the polishing efficiency is significantly reduced. On the other hand, if the backing material is too hard, it becomes a state close to the case where the abrasive sheet is directly attached to the base substrate, and it is difficult to obtain a sufficient hit prevention effect by the backing material.

(2) Per-piece at a portion other than the edge portion of the material to be polished Another problem in the technique shown in FIG. 10 is a per-edge portion at a portion other than the edge portion of the material to be polished. That is, when local undulations or protrusions exist on the surface to be polished of the material to be polished, even if it is a place other than the edge of the material to be polished in the above problem (1), )) May occur. Originally, the flattening process is a process performed for the purpose of removing such undulations and protrusions. However, in the case of fixed abrasive processing using a polishing sheet, if such stress concentration occurs, deep processing scratches on the surface to be polished will occur. Or scratches. Even if the swell and protrusion are eliminated by polishing, scratches and scratches may remain on the surface.

(3) Adhesion of the polishing sheet to the polishing surface of the material to be polished Further, in addition to the above problems, the adhesion of the polishing material to the polishing surface can be mentioned. That is, as the surface to be polished of the material to be polished is flattened by polishing, the adhesion between the material to be polished and the polishing sheet increases. During cooling, water or the like is generally supplied to the material to be polished for cooling. As shown in a model in FIG. 13, the water 11 causes the material 20 to be polished and the polishing sheet 10 to be separated. A thin water film is formed between them. And it becomes easy to produce the phenomenon that a to-be-polished material and a grinding | polishing sheet closely_contact | adhere with surface tension and external pressure. In particular, in recent years, the size of materials to be polished such as silicon wafers has increased, and this phenomenon has become more prominent. Due to this phenomenon, not only the processing efficiency is remarkably lowered, but in some cases, the spin-out of the material to be polished 20 (the material to be polished is detached from the polishing apparatus. At this time, the material to be polished is damaged and cannot be used). An accident may occur.

  Here, the same problem also exists in the case of processing using loose abrasive grains. Here, in the case of processing using loose abrasive grains, in addition to the above-described dressing technique, the following various ideas are applied to the configuration of the polishing pad.

  The most typical example is the use of a CMP pad / IC1000 / SUBA laminated pad series manufactured by Nita Haas. This pad has a laminated structure of two layers, and is used by being disposed between a material to be polished and a surface to which the material to be polished is attached of a polishing apparatus. Then, a layer of hard foamed urethane is laminated on a portion in contact with the polishing material, and a soft non-woven fabric is laminated on the opposite side, the polishing apparatus side.

  With this configuration, the soft non-woven fabric suppresses vibration of the workpiece during processing, maintains stable polishing characteristics, and the hard urethane foam layer provides polishing flatness on the surface of the workpiece. ing. However, the effect is not sufficient, it is still likely to occur per piece, and improvement is required.

  Further, Patent Document 1 proposes the use of a polishing pad with flexibility. This polishing pad includes a base material layer and a polishing layer made of an abrasive material and provided on one surface side of the base material layer. The polishing layer has a plurality of base portions, a plurality of tip portions, and a plurality of groove groups. The plurality of base portions are arranged on the base material layer so as to be spaced apart from each other, and the tip portions are columnar or frustum-like and are spaced apart from each other on the base portion. Further, the groove group is provided so that the base material layer is exposed between the base portions. With such a configuration, the surface of the polishing pad is made discontinuous to improve flexibility. However, even if this pad is used, stress concentration may occur somewhere in the polishing area, and high processing surface quality is not maintained, accuracy is low, and scratches and scratches may remain on the surface. It remained.

  On the other hand, in the case of the fixed abrasive processing technique, improvements such as the above-mentioned loose abrasive polishing pad have hardly progressed. In particular, when using an abrasive sheet, the so-called “tape polishing” style, which is a roll-to-roll progressive feed type, is performed while making the abrasive surface of the abrasive sheet in the form of an infinite belt with a pressing roller in line contact with the material to be polished. . In this method, since the entire polished surface cannot be polished simultaneously, the shape accuracy is rather deteriorated as compared with the case of using loose abrasive grains. However, when the abrasive sheet is applied to the base substrate or the pad as in the case of using the above-mentioned free abrasive grains, the problem as described above becomes rather serious. For this reason, the present condition is that the large area abrasive processing which utilizes the characteristic of an abrasive sheet has not yet been put into practical use.

  In this way, while suppressing per-piece of the material to be polished and maintaining high processing surface quality, high processing efficiency is achieved, and at the same time, the spin-out of the material to be polished can be reduced during processing, and a large area polishing surface There has been a demand for a polishing tool that can handle fixed abrasive grains.

  The present invention solves the above-mentioned conventional problem, that is, it enables to achieve high machining efficiency while suppressing per-piece of the workpiece and maintaining high machining surface quality, and spins out the workpiece during machining. It is an object of the present invention to provide a polishing apparatus that can perform fixed abrasive processing that can reduce the above.

  In order to solve the above-mentioned problems, the polishing tool of the present invention has a first elastic layer formed of an elastic body having an ASKER C hardness of 40 or less and a flat plate shape on the first elastic layer side, as described in claim 1. And a plurality of convex portions protruding from the flat plate portion to the opposite side of the first elastic layer, and having tips at the same plane, and forming the convex portion of the flat plate portion. A value representing the flexibility measured with an ASKER C rubber hardness tester with respect to the surface opposite to the side, a second elastic layer having a value of 60 or more and 77 or less, and one surface attached to the plane; and A polishing sheet having a plurality of abrasive grains fixed on the other surface is sequentially laminated.

  The polishing tool of the present invention includes a first elastic layer formed of an elastic body having an ASKER C hardness of 40 or less, a flat plate portion on the first elastic layer side, and the first elastic layer from the flat plate portion. A plurality of convex portions protruding on the opposite side and having tips on the same plane, and an ASKER C rubber hardness tester on the surface of the flat plate portion opposite to the convex portion forming side. A second elastic layer having a value representing flexibility measured by using 60 or more and 77 or less, and a polishing sheet attached to one surface of the plane and a plurality of abrasive grains fixed to the other surface, Since it is configured by sequentially laminating, it is possible to achieve high machining efficiency while maintaining high machining surface quality (scratch-free, high shape accuracy) while suppressing the per-abrasion of the material to be polished, and at the same time during machining Fixed abrasive that can reduce the spin-out of the workpiece Allows processing.

FIG. 1 is a model cross-sectional view showing a configuration of an example A of the polishing tool of the present invention. FIG. 2 is a top view of the model viewed from the convex portion side of the second elastic layer of the polishing tool A of FIG. FIG. 3 is a model side view showing a state in which the polishing tool A of FIG. 1 is attached to the polishing apparatus. In the figure, θ is the angle between the polished surface and the surface to be polished. FIG. 4 is an explanatory view showing a model of the function of the polishing tool of the present invention. FIG. 5A is a diagram showing the results of examining the distribution of locations where there was a large pressure change when pressing the polishing tool against the polishing tool, assuming the time of polishing, in Comparative Example 1. FIG. FIG. 5B is a diagram showing the result of examining the distribution of locations where there was a large pressure change when pressing the polishing tool against the polishing tool, assuming the time of polishing, in Comparative Example 1. FIG. 6 is a graph showing the results of examining the influence of the ASKER C hardness of the elastic body constituting the first elastic layer on the piece. FIG. 7 is a diagram showing the results when the thickness of the flat plate portion of the second elastic layer is 0.6 mm. FIG. 8 is in accordance with the ASKER C hardness measurement, which is a measure of the flexibility of the second elastic layer when the height of the flat portion of the second elastic layer is constant and the height of the convex portion is changed in Example 2. It is a graph which shows the influence on the measured value. FIG. 9A shows a case where the ratio of the convex part height / flat plate part thickness is 0.88, and FIG. 9B shows a case where the ratio of the convex part height / flat part thickness is 5.8. It is the figure which showed the distribution of the part with a large pressure change, respectively. FIG. 10 is a diagram showing an example of a conventional polishing method using a polishing sheet. FIG. 11 is an explanatory diagram of a model showing the contact of the polishing sheet with the edge portion of the material to be polished. FIG. 12 is an explanatory diagram of a model showing the contact of the polishing sheet with a portion other than the edge portion of the material to be polished. FIG. 3 is an explanatory diagram of a model showing a state where the surface to be polished of the material to be polished and the polishing surface of the polishing sheet are in close contact with water.

  The present invention will be described below with reference to the drawings. FIG. 1 is a model cross-sectional view of an example of the polishing tool of the present invention.

  This example is a polishing tool configured by sequentially laminating a first elastic layer 2, a second elastic layer 1, and a polishing sheet 3. The first elastic layer 2 is formed of an elastic body having an ASKER C hardness (Asker C hardness) of 40 or less. The second elastic layer 1 is provided so as to project from the flat plate portion 1b on the first elastic layer 2 side to the opposite side of the first elastic layer 2 from the flat plate portion 1b, and the tip is on the same plane 1c. And a plurality of convex portions 1a. Further, the second elastic layer 1 has a value measured by using an ASKER C rubber hardness tester on the surface of the flat plate portion opposite to the convex portion forming side, which is 60 or more and 77 or less. . The polishing sheet 3 is attached to the flat surface 1c with one surface 3a, and a plurality of abrasive grains are fixed to the other surface (polishing surface) 3b.

  Here, if the ASKER C hardness of the elastic body constituting the first elastic layer 2 is too high, it is difficult to obtain a reduction effect per piece. A preferred ASKER C hardness range is 40 or less. The elastic body constituting the first elastic layer 2 is preferably a porous material such as foamed polyethylene or foamed urethane because the foaming rate can be freely adjusted and the hardness can be easily controlled.

  The thickness of the first elastic layer 2 is preferably 5 mm or more and 50 mm or less. If it is too thin, the elastic layer cannot be sufficiently deformed, and if it is too thick, the pressurizing force necessary for processing is absorbed and processing tends to be difficult. A more preferable range is 10 mm or more and 30 mm or less.

  The elastic body constituting the second elastic layer 1 is preferably a solid (non-porous) rubber because the effects of the second elastic layer 1 can be sufficiently obtained. Examples of rubber include natural rubber, silicone rubber, and nitrile butadiene rubber.

  The flat plate portion 1b of the second elastic layer 1 has a function of determining the arrangement of the plurality of convex portions 1a of the second elastic layer 1 and maintaining their distribution state. That is, creation of the polishing tool of the present invention is facilitated by the flat plate portion 1b. The thickness is preferably 0.5 mm or less, and more preferably 0.4 mm or less. If the thickness of the flat plate portion 1b is too large, sufficient flexibility cannot be obtained in the second elastic layer, and the convex portion may not be able to effectively cope with the irregularities on the surface to be polished of the material to be polished.

  In FIG. 2, the model top view seen from the convex part 1a formation side of the 2nd elastic layer 1 of this example is shown. As shown in FIG. 2, the convex portion 1a has a cylindrical shape. The arrangement of these convex portions 1a is a staggered arrangement of 60 °. That is, there are six closest cylinders each centered on one cylinder (in this example, the distance between the axes is 3 mm), and these cylinders are arranged at positions that are 60 ° different from each other as viewed from the center cylinder. ing.

  Here, the shape of the convex portion 1a is not limited to a cylindrical shape, but is a columnar shape such as a quadrangular prism shape, a triangular prism shape, an elliptical prism shape, or the like. Alternatively, a frustum shape such as a square frustum or an elliptic frustum may be used. Alternatively, a combination of these may be used.

  Thus, by making the shape of the convex part 1a into a columnar shape or a frustum shape, the polishing sheet 3 and the polishing surface of the material to be polished are brought into point contact at the time of polishing, and the polishing pressure is reliably ensured. Can do. Furthermore, with the flattening of the polishing surface of the material to be polished, it is possible to suppress the occurrence of the problem (3) described in the description of the background art, that is, the problem that the polishing sheet and the film surface are in close contact with each other. It becomes.

  Moreover, it is preferable that the height of a convex part is 1 to 5 times the thickness of the said flat plate part. If the convex portions are too low, the individual convex portions are not easily deformed, and it is difficult to cope with the irregularities present on the polished surface of the material to be polished. On the other hand, if the height is too high, the convex portion tends to fall (sleep) with respect to the polishing surface, and at this time, it is difficult to cope with unevenness present on the polishing surface of the material to be polished. A more preferable range is 1 to 3 times.

  Further, the thickness and arrangement density of the convex portions are the processing conditions such as the hardness of the elastic body of the second elastic layer 1, the required polishing speed, the type of abrasive grains used, the size of the material to be polished, the polishing pressure, and the rotational speed. Since it varies depending on the situation, etc., it should be determined in advance by examination.

  Here, as a measure of the flexibility of the second elastic layer 1, the value representing the flexibility measured with an ASKER C rubber hardness tester on the surface of the flat plate portion opposite to the convex portion forming side is 60 or more. Various parameters are determined to be 77 or less. Specifically, these parameters include the material, the thickness and arrangement density of the convex portions, the thickness of the second elastic layer, the additive, the presence or absence of crosslinking, and the crosslinking conditions.

  Here, the evaluation of the flexibility of the second elastic layer is performed using an ASKER C rubber hardness meter used for measuring the ASKER C hardness of the Japan Rubber Association Standard (SRIS). However, as an object to be determined, not a normal rubber bulk product, but a molded product formed for the second elastic layer and provided with a plurality of convex portions integrally on a flat plate body is used. Then, the pusher of the Asker rubber hardness meter C is measured so as to be perpendicular to the flat surface (the surface on which the concave portion is not formed) of the molded product. In addition, since the convex part is partially formed in the back surface of the plane, the measurement value varies depending on the measurement location. For this purpose, the measurement was performed at 10 randomly selected locations, and the average value of these values was determined in the present invention using the “ASKER C rubber hardness tester” of the molded product and the second elastic layer. Value representing sex ”. This value is also referred to as “a value measured according to the ASKER C rubber hardness measurement”.

  If the value measured according to the ASKER C hardness of the second elastic layer is too low, the polishing pressure tends to decrease and the processing efficiency tends to decrease. On the other hand, if the hardness is too high, it is difficult to obtain the effect of eliminating one piece. The preferred ASKER C hardness range is 60 or more and 77 or less.

  According to the configuration of the present invention, the convex portions can be deformed independently, and the overall flexibility is improved. Furthermore, it can handle both small and large irregularities on the surface to be polished of the material to be polished. These can be effectively eliminated.

  The polishing sheet 3 is fixed on the polishing surface side such that abrasive grains protrude from the binder layer composed of, for example, various binders, and the back surface is the tip of the convex portion of the second elastic layer 1. It is fixed in contact with.

  The first elastic layer 2, the second elastic layer 1, and the polishing sheet 3 may be bonded, adhered, or bonded together using an adhesive, an adhesive, a double-sided adhesive tape, or the like. Also, the first elastic layer 2 and the second elastic layer 1 are formed integrally by forming one in advance and storing the other in the mold when forming the other. At this time, no adhesive or adhesive material or labor is required.

  FIG. 3 shows a model diagram of a polishing apparatus in which the example A of the polishing tool of the present invention is attached to the base substrate 5.

  As shown in FIG. 3, when the surface to be polished 9 and the polishing surface of the polishing sheet 3 are not parallel, first, the first elastic layer 2 adjacent to the base substrate portion is deformed, and the material to be polished is Eliminate per piece. On the other hand, since the second elastic layer 1 in contact with the polishing sheet 3 has a high hardness, the deformation is smaller than that of the first elastic layer, so that a reduction in polishing pressure at the polishing processing point can be suppressed and high processing efficiency can be realized. .

Here, the function of the polishing tool of the present invention is summarized in FIG.
As shown in FIG. 4A, it is assumed that the material 9 to be polished is in contact with the polishing sheet 3 at an angle, and the surface of the material 9 to be polished is wavy and has protrusions.

  FIG. 4B shows a first state in which the workpiece 9 is pressed from above. At this time, the first elastic layer 2 is deformed and follows the surface shape of the material to be polished, so that the contact between the pieces is prevented.

  FIG. 4C shows a second state where the pressure is further pressed from above. At this time, the columnar structure of the convex portion of the second elastic layer 1 is slightly deformed along the waviness of the surface to be polished of the material to be polished, and the polishing sheet 3 and the surface to be polished of the material to be polished are completely fitted (matched). To do. What is indicated by an arrow in the figure is a portion where the convex portion is greatly deformed, that is, a portion where stress is concentrated. However, the difference from the conventional example shown as a model in FIG. 12 is that the polishing sheet 3 is in contact with the surface to be polished of the material to be polished 9 in parts other than those indicated by the arrows, and the stress concentration is greatly relaxed. ing. That is, it is possible to obtain an effect that the surface to be polished can be flattened with respect to the protrusions on the surface to be polished, and the generation of deep scratches can be suppressed. In this model example, it is shown over time according to a hypothesis, but in the case of actual polishing, it does not always proceed in this order, but even in that case, the same effect can be obtained.

  While the present invention has been described with reference to the preferred embodiment, the polishing tool and the polishing apparatus of the present invention are not limited to the configuration of the above embodiment.

  A person skilled in the art can appropriately modify the polishing tool and the polishing apparatus of the present invention in accordance with conventionally known knowledge. Of course, such modifications are also included in the scope of the present invention as long as the configuration of the polishing tool and the polishing apparatus of the present invention is provided.

  Hereinafter, the present invention will be specifically described by way of examples.

[Example 1]
First, the second elastic layer was produced. Natural rubber (ASKER C hardness: 85) was used as the material of the elastic body to be used. The thickness of the flat plate portion 1b constituting the second elastic layer was 0.35 mm, and a plurality of (many) cylindrical convex portions 1a were formed integrally with the flat plate portion 1b thereon. The diameter of the convex part 1a was 2 mm, and as shown in FIG. 2, the distance between the axes (horizontal pitch interval) was 3 mm and the height was 1 mm in a staggered arrangement of 60 °. The second elastic layer was formed by pouring natural rubber into a stainless steel mold having such dimensions, releasing the mold from the mold after molding, and integrally molding the flat portion 1b and the plurality of convex portions. With respect to the flexibility of the second elastic layer thus obtained, the value measured according to the ASKER C hardness measurement of the second elastic layer was 73.

  As the first elastic layer, a foamed EVA (ethylene / vinyl acetate copolymer resin) having a thickness of 30 mm (commercially available 10-fold independent foamed product: 2A10 manufactured by Mifuku Kogyo Co., Ltd.) was prepared. The sponge had an ASKER C hardness of 35.

  Such a 1st elastic layer and the plate-shaped part of the said 2nd elastic layer were fixed using the double-sided tape, and were integrated.

  Next, in order to measure the in-plane pressure distribution of the glass workpiece, the composite elastic layer obtained in this way is fixed on the base substrate 5 as schematically shown in FIG. In addition, a pre-scale Prescale 4LW for fine pressure manufactured by Fuji Film Co., Ltd. was fixed instead of the polishing sheet.

  A glass substrate (100 mm × 70 mm) is fixed to the head portion 6 above the base substrate 5 (see FIG. 3), which can be rotated by a shaft 8 and can be raised and lowered in the vertical direction, as an alternative to the material 9 to be polished. .

  Further, the head portion is a mechanism that can be inclined with respect to the upper surface of the base substrate 5 by the angle adjusting mechanism 7. In this embodiment, the head portion 6 is moved up and down with the angle θ in FIG. 3 being 1 ° and the surface to be polished is inclined with respect to the polishing surface, and the glass substrate of this head portion is not rotated, and 30 kPa. The pressure was held on the prescale so that the pressure was maintained for 10 seconds.

  At this time, in FIG. 5 (a), the portion measured by the prescale and greatly changed in pressure by pressing is shown in dark color.

  As described above, when the pressure-changed portion was image-processed (binarized) and darkened and examined, the area of the dark-colored portion was 95% or more of the entire size within the range of the glass substrate size of 100 × 70 mm. Met. In addition, if the area in which the pressure is greatly changed is 75% or more of the whole, it is determined that there is no contact of the material to be polished and the entire surface is in contact.

[Comparative Example 1]
As in Example 1, except that a polyethylene foam sponge having an ASKER C hardness of 60 was used as the first elastic layer. FIG. 5B shows the state of the portion where the pressure has changed. In FIG. 5 (b), the pressure-changed portion (dark color portion) is as small as 42%, and it is understood that the suppression effect per piece of the material to be polished cannot be sufficiently obtained.

  Furthermore, FIG. 6 shows the results of examining the relationship between the hardness and the area of the portion where the pressure has greatly changed when a foamed sponge having different hardness is used as the first elastic layer.

  It can be seen from FIG. 6 that if the ASKER C hardness is 40 or less, a sufficient anti-periphery effect can be obtained. In addition, when the ASKER C hardness is 25 or less, it is considered that the dark area ratio is slightly lower than the case of 30 because of the following reason. That is, when such a too soft sponge is used as the first elastic layer, the pressing force at the time of evaluation is absorbed by this sponge, making it difficult to detect a pressure change due to the prescale, and a slightly lower value. It is thought that.

[Comparative Example 2]
Evaluation was performed in the same manner as in Example 1 except that the thickness of the flat plate portion of the second elastic layer was 0.6 mm. The results are shown in FIG.

  As can be understood from FIG. 7, the upper and lower corners on the right side of the drawing are dark in color and become thinner toward the left. Thus, as the thickness of the flat plate portion increases, the per-side increases. Here, when the thickness of the flat plate portion was similarly examined with the thicknesses of 0.5 mm, 0.25 mm, and 0.1 mm, all the same results as in Example 1, that is, the area of the portion where the pressure was greatly changed. Was over 80% of the total.

[Example 2]
Next, the influence of the height of the convex part of the second elastic layer was examined. As in Example 1 (the thickness of the flat plate portion is fixed at 0.35 mm), however, only the height of the convex column was changed.

  In FIG. 8, the horizontal axis represents the ratio of the height of the convex portion / the thickness of the flat plate portion, and the vertical axis represents the value measured according to the ASKER C hardness measurement.

  It is understood that the rubber hardness decreases as the height of the convex portion increases with respect to natural rubber (ASKER C hardness: 85). FIG. 9 (a) shows a pre-scale detection situation when the ratio of the convex portion height / flat plate portion thickness is 0.88. As described above, when the ratio of the height of the convex portion / thickness of the flat plate portion is smaller than 1, it is understood that pressure is received from the polishing sheet surface only at the four corners and no pressure is applied to the polishing sheet surface at the center of the material to be polished. Is done.

  On the other hand, FIG. 9B shows a distribution state of a portion where the pressure greatly changes when the ratio of the convex portion height / flat plate portion thickness is 5.8. In this figure, it seems that the entire surface is under pressure from the surface of the polishing sheet, but there is actually partial unevenness. This is presumed to be caused by the fact that the ratio of the height of the convex portion / thickness of the flat plate portion is large, that is, because the height of the convex portion is high, the convex portion collapses or is crushed during pressing. The Here, when the second elastic layer having the convex portions of various heights was created and examined, the ratio of the convex portion height / the flat plate portion thickness was detected in the prescale in the range of 1 to 5. All dark color area ratios were 75% or more.

  As can be understood from the results of these Examples and Comparative Examples, in order to efficiently suppress the contact of the material to be polished, the hardness of the elastic body forming the first elastic layer is important. In the second elastic layer, the thickness of the flat plate portion, the ratio of the height of the convex portion / thickness of the flat plate portion, and the ASKER C hardness measurement of the second elastic layer, which is a measure of the total flexibility of the second elastic layer The measured value is important.

[Example 3]
As in Example 1, however, instead of the press scale, a polishing film prepared by fixing the abrasive grains disclosed in Patent Document 2 to the polishing surface with a binder was fixed to the surface of the composite elastic layer. As a result of processing an optical glass disk (borosilicate crown glass (BK7 equivalent)) having a diameter of 100 mm, adjusted so that the maximum height roughness Rt is 2 μm, the maximum height roughness Ry without scratches is 5 minutes. A mirror surface of 30 nm or less could be obtained. The polishing conditions at this time were a platen rotational speed of 60 rpm, a processing pressure of 30 kPa, and a supply amount of pure water as cooling water to the polishing surface of 200 ml / min. When the thickness of the 10 parts of the material to be polished was measured after the polishing, the difference was within 0.5 μm, and it was confirmed that the polishing was performed with sufficiently high accuracy. Further, the polishing work was continued for 10 minutes on the material to be polished, but no spin-out of the material to be polished occurred.

[Comparative Example 3]
As in Example 3 above, the material to be polished was polished for 5 minutes. When the polishing operation was further performed without the second elastic layer, that is, with the polishing film fixed directly to the first elastic body, the material to be polished was spun out within 2 minutes.

  The reason for the occurrence of this spin-out is considered as follows. That is, after the surface to be polished of the material to be polished is sufficiently flattened and polished without the second elastic layer, the adhesion between the material to be polished and the polishing sheet is increased and supplied. A thin water film is formed between the material to be polished and the polishing sheet by the water that is applied. Then, due to the surface tension and the external pressure, the material to be polished and the film are in close contact with each other, and as a result, the material to be polished is detached from the base substrate and spinout occurs.

DESCRIPTION OF SYMBOLS 1 2nd elastic layer 1a Convex part 1b Flat plate part 1c Plane 2 1st elastic layer 3 Polishing sheet 3a One side 3b The other side 5 Base base material 7 Angle adjustment mechanism 9 To-be-polished material

Japanese Unexamined Patent Publication No. 2014-018883 Japanese Patent No. 3990936

Claims (4)

A first elastic layer formed of an elastic body having an ASKER C hardness of 40 or less,
A flat plate portion on the first elastic layer side;
A plurality of convex portions that protrude from the flat plate portion to the opposite side to the first elastic layer, and whose tips are located on the same plane, and are opposite to the convex portion forming side of the flat plate portion A value representing the flexibility measured with an ASKER C rubber hardness meter with respect to the second elastic layer of 60 or more and 77 or less, and one surface attached to the plane; and
A polishing sheet having a plurality of abrasive grains fixed on the other surface;
A polishing tool characterized in that a plurality of layers are sequentially laminated. The thickness of the flat plate portion is 0.5 mm or less,
The shape of the convex part is a columnar shape, or the flat plate part side is a thick frustum, and
The polishing tool according to claim 1, wherein the height of the convex portion is 1 to 5 times the thickness of the flat plate portion.   The polishing tool according to claim 1 or 2, wherein the first elastic layer is made of a foam, and the second elastic layer is made of a solid rubber.   A polishing apparatus comprising the polishing tool according to claim 1.