JP2016107366A - Abrasive cloth - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abrasive cloth excellent in a polishing rate and surface roughness property of a surface to be polished.SOLUTION: An abrasive cloth comprises a flexible plastic sheet including a polishing surface to polish a surface to be polished. A total elastic modulus, which is an elastic modulus in a direction perpendicular to the polishing surface of the abrasive cloth, is 4300 gf/cmor less. In the flexible plastic sheet, the elastic modulus in a direction perpendicular to the polishing surface of the abrasive cloth, is getting greater as a portion thereof is getting further from the polishing surface in a direction perpendicular to the polishing surface.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an abrasive cloth.

  For polishing of optical materials such as reflection mirrors and lenses, magnetic recording medium substrates, silicon wafers for semiconductor devices, glass substrates for liquid crystal displays, etc. A cloth is used.

  For example, Patent Document 1 discloses a polishing cloth that can improve the flatness by suppressing the occurrence of scratches and roll-off of an object to be polished. Specifically, in a polishing cloth including a soft plastic sheet having a polishing surface for polishing an object to be polished and an elastic body bonded to the opposite side of the polishing surface, the soft plastic sheet is more elastic than the elastic body. It has a large compressibility and small hardness, the elastic body has a compression ratio of 1% or more and a hardness of 90 degrees or less, and both the soft plastic sheet and the elastic body have a thickness of 0.2 mm or more. An abrasive cloth is disclosed.

JP 2009-83014 A

  However, the polishing cloth disclosed in Patent Document 1 has a problem that the polishing rate is not sufficient and the productivity is lowered. Although the polishing cloth disclosed in Patent Document 1 has an effect of improving the flatness, in recent years, further improvement of the flatness has been demanded for the object to be polished, and the effect is not sufficient. It was.

  In view of the above-described problems of the related art, an object of one aspect of the present invention is to provide a polishing cloth excellent in polishing rate and surface roughness characteristics of a surface to be polished.

In one embodiment of the present invention to solve the above problems, a polishing cloth including a soft plastic sheet layer having a polishing surface for polishing a surface to be polished,
The overall elastic modulus, which is the elastic modulus in the direction perpendicular to the polishing surface, of the polishing cloth is 4300 gf / cm ² or less,
In the soft plastic sheet layer, there is provided a polishing cloth in which an elastic modulus of the polishing cloth in a direction perpendicular to the polishing surface is increased in a direction away from the polishing surface.

  According to one embodiment of the present invention, a polishing cloth excellent in polishing rate and surface roughness characteristics of a surface to be polished can be provided.

The schematic diagram of the cross-section of the polishing cloth which concerns on embodiment of this invention. Explanatory drawing of the grinding | polishing method using the polishing cloth which concerns on embodiment of this invention

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and the following embodiments are not departed from the scope of the present invention. Various modifications and substitutions can be made.

  In this embodiment, a configuration example of a polishing cloth will be described.

  The polishing cloth (polishing pad) of this embodiment can include a soft plastic sheet layer having a polishing surface for polishing the surface to be polished.

And it is preferable that the whole elasticity modulus which is an elasticity modulus of a polishing cloth perpendicular | vertical direction is 4300 gf / cm < ² > or less. Further, in the soft plastic sheet layer, the elastic modulus of the polishing cloth in the direction perpendicular to the polishing surface can be increased in the direction away from the polishing surface.
FIG. 1 shows a schematic diagram of a cross-sectional structure in a plane perpendicular to the polishing surface 11a of the polishing pad 10 of the present embodiment.

  As shown in FIG. 1, the polishing cloth 10 of this embodiment can include a soft plastic sheet layer 11. The soft plastic sheet layer 11 has a polishing surface 11a. The flexible plastic sheet layer 11 can include, for example, a polyurethane resin.

  The structure of the flexible plastic sheet layer 11 is not particularly limited, and may be a structure that does not include bubbles or the like, for example, or may have a foam structure in which bubbles are formed inside.

  In particular, it is preferable that the soft plastic sheet layer 11 includes a polyurethane resin having a foam structure in which a wet film is formed and bubbles are formed therein. Thus, when the soft plastic sheet layer 11 has a foamed structure in which bubbles are formed, the polishing cloth can easily hold the abrasive supplied to the polishing surface side. For this reason, the polishing rate is particularly improved, and the surface to be polished can be particularly uniformly polished. When the soft plastic sheet layer 11 has a foam structure, the size and distribution of the bubbles contained therein are not particularly limited. For example, the bubbles on the polishing surface side are smaller than the surface side opposite to the polishing surface. It is preferable that the size of the device is configured to be small.

And it is preferable that the abrasive cloth of this embodiment is 4300 gf / cm < ² > or less in the whole elastic modulus which is an elastic modulus of the abrasive cloth in the direction perpendicular to the polishing surface.

  In the case of the polishing cloth 10 shown in FIG. 1, the elastic modulus (overall elastic modulus) in the direction perpendicular to the polishing surface of the polishing cloth is the direction perpendicular to the polishing surface 11a in the polishing surface 11a, that is, the Z axis in the drawing. The elastic modulus in the direction is shown. Therefore, the elastic modulus in the direction perpendicular to the polishing surface of the polishing cloth means the elastic modulus of the entire polishing cloth, and the initial state measured before partially removing the soft plastic sheet layer described later by grinding. It means the elastic modulus at. As will be described later, the polishing pad 10 can also include layers other than the soft plastic sheet layer 11 such as the elastic layer 12. When the polishing pad 10 includes a layer other than the soft plastic sheet layer 11 such as the elastic body layer 12, the overall elastic modulus indicates the elastic modulus of the entire polishing pad 10 including the layers other than the soft plastic sheet layer 11. Hereinafter, the elastic modulus of the polishing cloth in the direction perpendicular to the polishing surface is also simply referred to as the total elastic modulus.

Here, a method for evaluating the overall elastic modulus will be described.
First, a pressing jig is applied to the polishing surface 11a and pushed into the polishing cloth 10 at a predetermined speed. When a predetermined load is applied to the polishing cloth 10, the pressing jig is stopped. Then, the elastic modulus can be calculated by dividing the change in stress at that time by the sinking amount of the polishing pad 10.

  In the polishing cloth 10 of this embodiment, in the soft plastic sheet layer 11, the elastic modulus of the polishing cloth 10 in the direction perpendicular to the polishing surface 11a increases in the direction away from the polishing surface 11a. .

  The elastic modulus of the abrasive cloth 10 in the soft plastic sheet layer 11 in the direction perpendicular to the abrasive surface 11a (hereinafter also simply referred to as “elastic modulus of the abrasive cloth in the soft plastic sheet layer”) is perpendicular to the abrasive surface 11a. A method for evaluating the change along the line will be described with reference to FIG.

  The change in the elastic modulus of the polishing cloth in the soft plastic sheet layer along the direction perpendicular to the polishing surface 11a is obtained by grinding and removing the soft plastic sheet layer 11 by an arbitrary thickness from the polishing surface 11a side, and measuring the elastic modulus. It can be obtained by repeatedly performing the operation.

  A method for measuring the elastic modulus at this time will be described. For example, when the soft plastic sheet layer 11 is removed to the dotted line 111 in FIG. 1 by grinding, the pressing jig is first applied to the surface of the exposed dotted line 111 and pressed into the polishing pad 10 at a predetermined speed. Next, the pressing of the pressing jig is stopped when a predetermined load is applied to the polishing pad 10. Then, by dividing the change in stress at that time by the sinking amount of the polishing pad 10, the elastic modulus in the direction perpendicular to the polishing surface 11a of the polishing pad 10 on the surface of the dotted line 111 can be calculated.

  Next, for example, when the soft plastic sheet layer 11 is ground to the dotted line 112 in FIG. 1 by grinding, for example, the abrasive cloth 10 on the surface of the dotted line 112 is the same except that the pressing jig is applied to the exposed surface of the dotted line 112. The elastic modulus in the direction perpendicular to the polishing surface 11a can be calculated.

  Then, from the total elastic modulus before thinning the soft plastic sheet layer 11, for example, the polishing cloth 10 on the surface of the dotted line 111, the elastic modulus in the direction perpendicular to the polishing surface 11a, and the polishing cloth 10 on the surface of the dotted line 112 is polished. The change to the elastic modulus in the direction perpendicular to the surface 11a can be a change in the elastic modulus of the polishing pad in the soft plastic sheet layer along the direction perpendicular to the polishing surface 11a.

  As described above, the polishing pad 10 of the present embodiment is such that the elastic modulus in the direction perpendicular to the polishing surface 11a of the polishing pad 10 is away from the polishing surface 11a in the direction perpendicular to the polishing surface 11a. It is preferable that it is large. That is, when the soft plastic sheet layer 11 is ground from the polishing surface 11a side to reduce the thickness of the soft plastic sheet layer 11, the operation of measuring the elastic modulus of the polishing cloth is performed a plurality of times. It is preferable that the polishing pad has an elastic modulus that increases as the thickness of the polishing pad decreases.

  Thus, when the elastic modulus of the polishing pad 10 as a whole increases as the thickness of the soft plastic sheet layer 11 decreases, the soft plastic sheet layer 11 extends along the direction perpendicular to the polishing surface 11a, that is, along the Z-axis direction. It means that it is harder. Since the soft plastic sheet layer 11 is configured to become harder in a direction away from the polishing surface 11a in a direction perpendicular to the polishing surface 11a, the polishing rate of the polishing pad 10 can be improved.

  In the soft plastic sheet layer 11, the aspect is not particularly limited to the extent that the elastic modulus in the direction perpendicular to the polishing surface 11 a of the polishing pad 10 increases in the direction away from the polishing surface 11 a.

  For example, in the flexible plastic sheet layer 11, the elastic modulus in the direction perpendicular to the polishing surface 11a of the polishing pad 10 can be configured to change substantially linearly in a direction away from the polishing surface 11a. . That is, after the soft plastic sheet layer 11 is ground from the polishing surface 11a side to reduce the thickness of the soft plastic sheet layer 11, the elastic modulus is reduced when the operation of measuring the elastic modulus of the polishing cloth is performed a plurality of times. It can comprise so that it may change in a substantially linear form with respect to the grinding amount of a sheet | seat layer.

  Note that the elastic modulus of the polishing pad does not need to change over the entire soft plastic sheet layer 11, and it is sufficient if the elastic modulus of the polishing pad is changed at least partially.

  Further, in the soft plastic sheet layer 11, for example, the elastic modulus in the direction perpendicular to the polishing surface 11a of the polishing pad 10 may be configured to increase discontinuously in a direction away from the polishing surface 11a. it can.

In particular, the elastic modulus obtained by subtracting the overall elastic modulus from the elastic modulus in the direction perpendicular to the polishing surface of the polishing pad when 25% of the thickness of the soft plastic sheet layer 11 is removed is 700 gf / cm ² or more. are preferred, more preferably 1000 gf / cm ² or more, and particularly preferably 1500gf / cm ² or more.

This point will be described with reference to FIG. First, in FIG. 1, the thickness h ₁₁ of the soft plastic sheet layer 11 is set to 1, the thickness of the soft plastic sheet layer 11 from the polishing surface 11a to the dotted line 112 is set to h ₁₁₂ , and the thickness h ₁₁ and the thickness h are set. The ratio to ₁₁₂ is 0.25. When the soft plastic sheet layer 11 is removed up to the dotted line 112 (this removal amount is hereinafter also referred to as “removal amount 0.25”), the elastic modulus in the Z-axis direction in the drawing on the surface of the dotted line 112 of the polishing pad. but the polishing cloth prior to the removal, it is more preferable modulus in the Z-axis direction, i.e. it is preferably 700 gf / cm ² or more greater than the overall modulus of elasticity, 1000 gf / cm ² or more larger in the polishing surface 11a, It is particularly preferably 1500 gf / cm ² or more.

In addition, when 25% of the thickness of the soft plastic sheet layer is removed, the elastic modulus of the polishing cloth in the direction perpendicular to the polishing surface (elasticity when the removal amount is 0.25) is 4900 gf / cm ² or more. It is preferably 5000 gf / cm ² or more.

  Since the elastic modulus of the polishing cloth has the above-described configuration, the soft plastic sheet layer 11 included in the polishing cloth has a structure in which the polishing surface 11a side is soft and the inside is sufficiently hard compared to the polishing surface 11a. Become. Therefore, when polishing an object to be polished, it is possible to obtain a polishing cloth that is excellent particularly in polishing rate, polishing uniformity, and surface roughness characteristics of the surface to be polished.

  The configuration of the soft plastic sheet layer 11 for increasing the elastic modulus in the direction perpendicular to the polishing surface 11a of the polishing cloth 10 in the direction away from the polishing surface 11a in the soft plastic sheet layer 11 is particularly limited. It is not something.

  For example, the soft plastic sheet layer may include a single layer of the soft plastic sheet and a material for adjusting the hardness of the soft plastic sheet. In this case, the material for adjusting the hardness of the soft plastic sheet can be applied to the soft plastic sheet, for example.

  According to the study by the inventors of the present invention, polyimide can be preferably used as a material for adjusting the hardness of the soft plastic sheet. By applying polyimide to the polishing surface 11a of the soft plastic sheet layer 11 by spraying or the like, the coated polishing surface 11a side is soft, and the surface 11b opposite to the polishing surface 11a can be relatively hard. For this reason, in the soft plastic sheet layer 11, the elastic modulus in the direction perpendicular to the polishing surface 11a of the polishing pad 10 can be increased along the direction perpendicular to the polishing surface 11a.

  In addition, the material for adjusting the hardness of a soft plastic sheet can also be contained in a soft plastic sheet by mixing with a soft plastic sheet. In addition, a material for adjusting the hardness of the soft plastic sheet may be included in the soft plastic sheet by impregnating the soft plastic sheet with a material for adjusting the hardness of the soft plastic sheet.

  The soft plastic sheet layer can also be configured by laminating and bonding a plurality of soft plastic sheets having different elastic moduli in the direction perpendicular to the polishing surface depending on the size of bubbles contained, the content of bubbles, and the like. By laminating a plurality of soft plastic sheets having different hardnesses from the polishing surface side in advance, the entire soft plastic sheet layer can be a layer whose hardness changes from the polishing surface side. For this reason, in the soft plastic sheet layer 11, the elastic modulus in the direction perpendicular to the polishing surface 11a of the polishing pad 10 can be configured to increase in the direction away from the polishing surface 11a.

  Since it can manufacture especially easily, it is preferable that a soft plastic sheet layer is a form containing one layer of soft plastic sheet. In this case, as described above, for example, a material that adjusts the hardness of the soft plastic sheet such as polyimide is applied from the polishing surface side, and the elastic modulus in the direction perpendicular to the polishing surface 11a of the polishing pad 10 is set in the soft plastic sheet layer 11. Further, it can be configured to increase along the direction perpendicular to the polishing surface 11a.

  The polishing pad 10 of this embodiment can include other layers in addition to the soft plastic sheet layer 11. For example, as shown in FIG. 1, it can further have the elastic body layer 12 comprised from an elastic body.

  The elastic body layer 12 can be comprised by elastic bodies, such as a nonwoven fabric, a polyurethane, PET (polyethylene terephthalate), for example.

  The characteristic of the elastic body layer 12 is not specifically limited, What is necessary is just to be comprised so that the soft plastic sheet layer 11 may be supported. However, from the viewpoint of increasing the polishing rate, the elastic layer 12 preferably has a larger elastic modulus than the soft plastic sheet layer 11. For this reason, for example, the elastic layer 12 alone of the polishing pad 10 including the soft plastic sheet layer 11 and the elastic layer 12 according to the present embodiment has an elastic modulus in the polishing surface 11a perpendicular to the polishing surface 11a. It is preferable that the elastic modulus in the direction perpendicular to the polishing surface 11a is larger.

  The elastic layer 12 can be disposed, for example, on the lower surface side of the soft plastic sheet layer 11, that is, on the surface 11b opposite to the polishing surface 11a. The elastic body layer 12 can be joined to the soft plastic sheet layer 11.

  The thicknesses of the soft plastic sheet layer 11 and the elastic body layer 12 are not particularly limited, and can be any thickness. However, since wet film formation of the soft plastic sheet layer 11 may be difficult, for example, both the soft plastic sheet layer 11 and the elastic body layer 12 preferably have a thickness of 2.0 mm or less. More preferably, the thickness is 1.0 mm or less.

  Although the lower limit of the thickness of the soft plastic sheet layer 11 and the elastic body layer 12 is not particularly limited, for example, from the viewpoint of imparting sufficient durability to the polishing pad 10, for example, the soft plastic sheet layer 11 and the elastic layer The body layer 12 preferably has a thickness of 0.2 mm or more, and more preferably 0.4 mm or more.

Incidentally, the thickness h ₁₁ of flexible plastic sheet layer 11, the thickness h ₁₂ of the elastic layer 12, may be the same or may be different.

The polishing cloth of this embodiment described above has a soft plastic sheet layer having a polishing surface as described above. The elastic modulus of the polishing cloth in the direction perpendicular to the polishing surface is 4300 gf / cm ² or less. In the soft plastic sheet layer, the elastic modulus in the direction perpendicular to the polishing surface of the polishing cloth is along the direction perpendicular to the polishing surface. It gets bigger in the direction of going away. For this reason, it can be set as the polishing cloth excellent in the polishing rate, the polishing uniformity, and the surface roughness characteristics of the surface to be polished.

  FIG. 2 shows an example of a polishing method using the polishing cloth of this embodiment. The polishing method using the polishing cloth of this embodiment is not particularly limited. For example, first, the polishing cloth 10 of this embodiment is placed on the surface plate 21, and the polishing surface of the polishing cloth 10 of this embodiment is disposed on the polishing surface. The surface to be polished 22 is pressed by a weight 23 via a holder (not shown). Then, polishing can be performed by rotating the surface plate 21 along the arrow A with the workpiece 22 pressed against the polishing cloth 10 and simultaneously rotating the workpiece 22 along the arrow B by the weight 23. . The polishing can be performed while supplying the abrasive 24 onto the polishing pad 10 as shown in FIG.

  The kind of abrasive 24 used at this time is not particularly limited, and can be arbitrarily selected depending on the material of the workpiece 22 and the like. As the abrasive 24, for example, a slurry of cerium oxide, zirconium oxide, iron oxide, manganese oxide, silicon oxide, or the like can be used.

  The object to be polished using the polishing cloth of this embodiment is not particularly limited, and various kinds of objects to be polished can be polished.

  However, as described above, the polishing cloth of this embodiment is a polishing cloth excellent in polishing rate, polishing uniformity, and surface roughness characteristics of the surface to be polished. For this reason, for example, it can be more suitably used when it is required to improve the flatness of the surface to be polished of the object to be polished and to particularly improve the surface roughness characteristics of the surface to be polished. Specifically, it can be suitably used for polishing optical materials such as reflection mirrors and lenses, magnetic recording medium substrates, silicon wafers for semiconductor devices, glass substrates for liquid crystal displays, and the like.

  Further, for example, in the manufacturing method of an optical material such as a reflecting mirror and a lens, a substrate for a magnetic recording medium, a silicon wafer for a semiconductor device, a glass substrate for a liquid crystal display, etc. An abrasive cloth can be used suitably.

  Specific examples will be described below, but the present invention is not limited to these examples.

First, polishing cloth characteristics when polishing is performed in the following experimental examples and a method for evaluating the polishing characteristics of the polishing cloth will be described.
(Measurement of thickness of soft plastic sheet layer and elastic layer)
First, the cross section of the polishing cloth before polishing of each experimental example was photographed with a microscope (Keyence Corporation model: VHX-900). Subsequently, five thicknesses of the soft plastic sheet layer were measured from the photographed cross-sectional photograph of the polishing pad, and the average value was defined as the thickness h ₁₁ of the soft plastic sheet layer of the polishing pad.

It was calculated thickness h ₁₂ of the elastic layer in the same manner for the elastic layer.
(Measurement of elastic modulus in the direction perpendicular to the polishing surface of the polishing cloth on the polishing surface)
The case of the polishing pad 10 shown in FIG. 1 will be described as an example.

A 100 mmφ platen was attached to the surface 12a of the polishing pad 10 opposite to the polishing surface 11a. Next, a 50 mmφ platen is disposed at a substantially central portion of the polishing surface 11a of the polishing cloth 10, and the platen is placed on the polishing cloth 10 in a direction perpendicular to the polishing surface 11a (Z-axis direction in the drawing) at a speed of 0.5 mm / min. When the load was applied to the polishing pad 10 at a load of 100 g / cm ² , the pressing of the platen was stopped. Then, the elastic modulus was calculated by dividing the change in stress until the pressing of the platen was stopped by the amount of depression of the platen into the polishing cloth.

  In each experimental example, a total of 10 measurements were performed according to the above-described procedure, and the average of the 10 measurements was used as the elastic modulus of the polishing cloth on the polishing surface in the direction perpendicular to the polishing surface.

In Table 1, the elastic modulus of the polishing cloth in the direction perpendicular to the polishing surface is shown as “total elastic modulus”. The same applies to the following description.
(Measurement of elastic modulus in the direction perpendicular to the polishing surface of the polishing cloth in the soft plastic sheet layer)
The case of the polishing pad 10 shown in FIG. 1 will be described as an example.

  A polishing cloth was set in a small single-side polishing machine, dressing was performed using water as a coolant, and the soft plastic sheet layer 11 was removed from the polishing surface 11a side to a dotted line 111 or a dotted line 112 to a predetermined thickness.

  And the elastic modulus was measured about the polishing cloth after removing the predetermined thickness of the soft plastic sheet layer. The elastic modulus was measured except that the platen was placed on the surface exposed by polishing, specifically the surface of the dotted line 111 or the surface of the dotted line 112, and the platen was pushed in the direction perpendicular to the polishing surface. The measurement was performed in the same manner as the measurement of the elastic modulus of the polishing cloth in the direction perpendicular to the polishing surface. Therefore, the measurement was also performed 10 times in total on the surface of the dotted line 111 or the surface of the dotted line 112, and the average value was defined as the elastic modulus of the polishing cloth on the surface in the direction perpendicular to the polishing surface.

For each experimental example, when the thickness h of the soft plastic sheet layer 11 is 1, the soft plastic sheet layer 11 is removed up to the dotted line 111 where h ₁₁₁ is 0.15, and the polishing cloth on the surface of the dotted line 111 is removed. The elastic modulus in the direction perpendicular to the polished surface was measured. The elastic modulus at this time is shown as “elastic modulus at the removal amount of 0.15” in Table 1. The same applies to the following description.

  When the soft plastic sheet layer 11 was removed up to the dotted line 111, dressing was performed for 10 minutes using a # 325 diamond dresser, followed by dressing for 30 minutes using a # 800 dresser.

Further, for each experimental example, when the thickness h of the soft plastic sheet layer 11 is 1, the soft plastic sheet layer 11 is removed up to the dotted line 112 where h ₁₁₂ becomes 0.25, and the polishing cloth on the surface of the dotted line 112 is removed. The elastic modulus in the direction perpendicular to the polished surface was measured. The elastic modulus at this time is indicated as “elastic modulus at the removal amount of 0.25” in Table 1. The same applies to the following description.

When removing the soft plastic sheet layer 11 up to the dotted line 112, the dressing was performed for 120 minutes using a # 325 diamond dresser, and then the dressing was performed for 60 minutes using a # 800 dresser.
(Change rate of elastic modulus in the direction perpendicular to the polishing surface of the polishing cloth in the soft plastic sheet layer)
The overall elastic modulus, the elastic modulus at the removal amount of 0.15, and the elastic modulus at the removal amount of 0.25 evaluated for the polishing cloth of each experimental example were perpendicular to the polished surface of the surface where each elastic modulus was measured. Was plotted against the distance, and this was linearly approximated by the method of least squares. The slope of the straight line at this time is shown in Table 1 as “the rate of change in the elastic modulus of the soft plastic sheet layer in the direction perpendicular to the polishing surface of the polishing pad”.

In addition, the distance in the direction perpendicular to the polished surface of the surface where each elastic modulus was measured was 0 for the overall elastic modulus, 0.15 for the removal amount 0.15, and 0.15 for the removal amount 0.25. Plotted as 0.25.
(Polishing rate, polishing rate ratio, polishing rate evaluation)
Pure water was added to cerium oxide to prepare an abrasive slurry having a solid content of 10 wt%. Then, the quartz substrate was polished with the polishing cloth of each experimental example and the abrasive slurry, and the polishing rate at this time was evaluated.

The quartz substrate was polished using a single-sided small polishing machine. Specifically, first, as shown in FIG. 2, the polishing cloth 10 of each experimental example was fixed on the surface plate 21 so that the polishing surface faced the upper surface side. Next, three 30 mm square quartz substrates having a thickness of 1.3 mm were set on the polishing surface of the polishing pad 10 as the object to be polished 22, and these quartz substrates were held by a holder (not shown) and pressed by a weight 23. Then, polishing was performed for 15 minutes under the conditions of a polishing pressure of 100 g / cm ² , a platen rotation speed of 60 rpm, and a slurry flow rate of 25 ml / min. At this time, the polishing rate in the first test was calculated from the weight reduction amount of the three glass substrates. Thereafter, a total of three tests including the first test were performed under the same conditions, and the average value of the polishing rates in the three tests was defined as the polishing rate of the polishing pad.

  Also, the polishing rate ratio was calculated for the polishing rate of each experimental example with the polishing rate of the experimental example of Example 4 described later, which is a polishing cloth generally used at present, as a reference, that is, 1.000.

The polishing rate evaluation is A when the polishing rate ratio is greater than 3, the polishing rate evaluation is B when the polishing rate ratio is greater than 1 and 3 or less, and the polishing rate is when the polishing rate ratio is 1 or less. Evaluation was C.
(Surface roughness, surface roughness index, surface roughness evaluation)
When the polishing rate was evaluated, the surface roughness of the polished surface of the quartz substrate that had been polished three times in total as described above was measured. The surface roughness was measured using a white interference microscope (Model: Zygo NewView 7300, manufactured by Zygo).

  In the evaluation of the polishing rate, the three quartz substrates were polished, but the measurement was performed on one quartz substrate selected from the three polished quartz substrates.

  In each experimental example, the surface roughness of the surface to be polished at the time of polishing using the polishing cloth of the experimental example of Example 4 to be described later, which is a polishing cloth generally used at present, is set as a reference, that is, 1.00. A surface roughness index was calculated for the surface roughness of the polished surface of the polished quartz substrate.

  When the surface roughness index is less than 0.8, the surface roughness evaluation is A, and when the surface roughness index is 0.8 or more and less than 0.9, the surface roughness evaluation is B. When the index was 0.9 or more, the surface roughness evaluation was C.

Next, the polishing cloth in each experimental example will be described. Examples 1 to 3 are examples, and examples 4 to 6 are comparative examples.
[Example 1]
As shown in FIG. 1, an abrasive cloth 10 in which a soft plastic sheet layer 11 was placed on and bonded to an elastic body layer 12 was used.

  The elastic body layer 12 is composed of a nonwoven fabric which is an elastic body having a thickness of 826 μm.

  The soft plastic sheet layer 11 is formed into a wet film having a thickness of 593 μm, and includes a single layer of polyurethane resin having a foamed structure including bubbles inside. Then, a polyimide solution using a mixture of dimethyl ether, methyl ethyl ketone, acetone, cellosolve acetate as a solvent is sprayed on the polyurethane resin contained in the soft plastic sheet layer 11 from the polishing surface 11a side, and dried to soft plastic. A sheet layer 11 was formed.

The above-described evaluation was performed on the polishing cloth. The evaluation results are shown in Table 1.
[Example 2]
A polishing cloth was prepared and evaluated in the same manner as in Example 1 except that the amount of the polyimide solution applied to one layer of polyurethane resin contained in the soft plastic sheet layer 11 was halved.

The evaluation results are shown in Table 1.
[Example 3]
A polishing cloth was applied in the same manner as in Example 1 except that the amount of the polyimide solution applied to one layer of polyurethane resin contained in the soft plastic sheet layer 11 was less than that in Example 2 and extremely small. Fabricated and evaluated.

The evaluation results are shown in Table 1.
[Example 4]
A polishing cloth was prepared and evaluated in the same manner as in Example 1 except that the polyimide solution was not applied to one layer of polyurethane resin contained in the soft plastic sheet layer 11.

The evaluation results are shown in Table 1.
[Example 5]
As in the case of Example 1, the polishing pad 10 in which the soft plastic sheet layer 11 was disposed on and bonded to the elastic body layer 12 was used.

  However, the elastic body layer 12 is made of an elastic nonwoven fabric having a thickness of 495 μm, the soft plastic sheet layer 11 is wet-formed with a thickness of 1186 μm, and is a single layer polyurethane having a foam structure containing bubbles inside Consists of resin. Moreover, the polyimide solution was not applied to the polyurethane resin contained in the soft plastic sheet layer.

The above-described evaluation was performed on the polishing cloth. The evaluation results are shown in Table 1.
[Example 6]
A polishing cloth was prepared and evaluated in the same manner as in Example 1 except that only a mixture of dimethyl ether, methyl ethyl ketone, acetone, and cellosolve acetate was applied to a single layer of polyurethane resin contained in the soft plastic sheet layer 11. went.

  The evaluation results are shown in Table 1.

例１〜例４の実験例を比較すると、軟質プラスチックシート層１１、及び弾性体層１２の厚さ同じであるが、全体弾性率は例４から順に例３、例２、例１の順番で小さくなっている。

When the experimental examples of Examples 1 to 4 are compared, the thicknesses of the soft plastic sheet layer 11 and the elastic body layer 12 are the same, but the overall elastic modulus is in the order of Example 3, Example 2, and Example 1 in order from Example 4. It is getting smaller.

  And the value of the surface roughness of the surface to be polished of the object to be polished decreases in the order of Example 3, Example 2, and Example 1 in order from Example 4, and shows the same tendency as the above-mentioned overall elastic modulus. I can confirm.

In particular, it was confirmed that the surface roughness values of Examples 1, 2, and 3 having an overall elastic modulus of 4300 gf / cm ² or less were very small, 0.17 nm, 0.18 nm, and 0.20 nm. .

In addition, although Examples 1 to 4 were compared here, the surface roughness of the polished surface of the object to be polished was about 0.22 nm for Example 5 and Example 6 in which the overall elastic modulus exceeded 4300 gf / cm ² . It has confirmed that it was very large compared with Example 1-3.

  About the experimental examples of Examples 1 to 4, when the rate of change in elastic modulus in the soft plastic sheet layer in the direction perpendicular to the polishing surface of the polishing pad is compared, the order of Example 3, Example 2, and Example 1 increases in order from Example 4. It has become. In particular, in Examples 1 to 3, the change rate of the elastic modulus in the direction perpendicular to the polishing surface of the polishing pad in the soft plastic sheet layer is positive, and Example 4 is negative.

  It should be noted that the “elastic modulus at the removal amount of 0.25” and “(elastic modulus at the removal amount of 0.25) − (overall elastic modulus)” are also in the order of Example 3, Example 2, and Example 1 in order from Example 4. You can see that it is getting bigger.

  That is, in the soft plastic sheet layers of Examples 1 to 3, the change rate of the elastic modulus in the direction perpendicular to the polishing surface of the polishing cloth, the elastic modulus at the removal amount of 0.25, and the elastic modulus at the removal amount of 0.25 From the value of-) (total elastic modulus), it can be confirmed that the polishing cloths of Examples 1 to 3 have a structure in which the polishing surface side is soft and becomes harder as the distance from the polishing surface in the soft plastic sheet layer increases in the vertical direction. . Furthermore, it turns out that the change of the hardness of a perpendicular direction becomes larger from the grinding | polishing surface in a soft plastic sheet layer in order of Example 3 to Example 2, Example 1. FIG.

  On the other hand, in Example 4, in the soft plastic sheet layer, the rate of change of the elastic modulus in the direction perpendicular to the polishing surface of the polishing pad, and (elastic modulus at the removal amount of 0.25) − (overall elastic modulus) are negative. It has become. For this reason, in Example 4, it can be confirmed that the soft plastic sheet layer has a structure that becomes softer as it goes away from the polishing surface in the vertical direction.

  When the polishing rate evaluation of the polishing characteristics is seen, the evaluation for Example 1 and Example 2 is A, the evaluation for Example 3 is B, and the evaluation for Example 4 is C. It was confirmed that Therefore, the polishing rate is the change rate of the elastic modulus in the direction perpendicular to the polishing surface of the polishing cloth in the above-described soft plastic sheet layer, “elastic modulus at the removal amount of 0.25”, and “(removal amount at 0.25 hour). It can be confirmed that the same tendency as the numerical value of “elastic modulus of (b)-(total elastic modulus)” is shown.

  From these results, it is possible to improve the polishing rate by having a structure in which the elastic modulus of the soft plastic sheet layer in the direction perpendicular to the polishing surface of the polishing cloth increases in the direction away from the polishing surface in the vertical direction. Was confirmed.

In Example 5, in the soft plastic sheet layer, the rate of change of the elastic modulus in the direction perpendicular to the polishing surface of the polishing pad, and (elastic modulus when the removal amount is 0.25) − (overall elastic modulus) are negative. Nevertheless, the evaluation of the polishing rate was A. This is because the overall elastic modulus is as very large as 6600 gf / cm ^{2. Although} the polishing rate evaluation is improved, the performance of the polishing uniformity and the surface roughness characteristics of the surface to be polished is lowered. Thus, it was confirmed that the surface roughness evaluation of the polished surface was deteriorated.

As described above, the overall elastic modulus is 4300 gf / cm ² or less, and in the soft plastic sheet layer, the elastic modulus of the polishing cloth in the direction perpendicular to the polishing surface increases in the direction away from the polishing surface in the vertical direction. In Example 3, it was confirmed that the polishing rate at the time of polishing was excellent and the surface roughness of the surface to be polished could be reduced. When the polishing cloths of Examples 1 to 3 are used, the surface roughness of the surface to be polished can also be reduced. Therefore, the polishing cloths of Examples 1 to 3 are excellent in polishing uniformity and surface roughness characteristics of the surface to be polished. Can be confirmed to be a polishing cloth

DESCRIPTION OF SYMBOLS 10 Polishing cloth 11 Soft plastic sheet layer 12 Elastic body layer 11a Polishing surface

Claims (8)

A polishing cloth including a soft plastic sheet layer having a polishing surface for polishing a surface to be polished,
The overall elastic modulus, which is the elastic modulus in the direction perpendicular to the polishing surface, of the polishing cloth is 4300 gf / cm ² or less,
A polishing cloth in which the elastic modulus of the polishing cloth in the direction perpendicular to the polishing surface is increased in a direction away from the polishing surface in the soft plastic sheet layer. The polishing cloth according to claim 1, wherein when 25% of the thickness of the soft plastic sheet layer is removed, an elastic modulus in the direction perpendicular to the polishing surface of the polishing cloth is 4900 gf / cm ² or more. The elastic modulus obtained by subtracting the overall elastic modulus from the elastic modulus in the direction perpendicular to the polishing surface of the polishing pad when removing 25% of the thickness of the soft plastic sheet layer is 700 gf / cm ² or more. The polishing cloth according to claim 1 or 2.   The abrasive cloth according to any one of claims 1 to 3, wherein the soft plastic sheet layer includes a polyurethane resin having a foam structure in which a wet film is formed and bubbles are formed therein.   The polishing cloth according to any one of claims 1 to 4, further comprising an elastic layer composed of an elastic body.   The polishing cloth according to claim 5, wherein both the soft plastic sheet layer and the elastic body layer have a thickness of 1.0 mm or less.   A glass substrate polishing method using the polishing cloth according to claim 1.   The manufacturing method of the glass substrate which has a grinding | polishing process using the grinding | polishing method of the glass substrate of Claim 7.

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