JP7304186B2 - Holding pad and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a holding pad and a manufacturing method thereof.

Conventionally, materials such as semiconductor devices and electronic parts, especially Si substrates (silicon wafers), GaAs (gallium arsenide) substrates, glass and LCD (liquid crystal display) substrates and other thin substrates (objects to be polished) surface (processed surface) ), a chemical mechanical polishing process using a polishing pad together with a slurry is performed because flatness is required. In such polishing, especially single-side polishing, a holding pad is sometimes used to hold the object to be polished. As a matter of course, the holding pad is required to be flat as well as the polishing pad.

For example, Patent Document 1 discloses a support layer and foam laminated on the support layer for the purpose of improving the flatness of a workpiece holding member that holds the workpiece and improving the quality of the workpiece. and a workpiece holding material for holding a workpiece, wherein the foam layer is formed by grinding the back surface of the foam layer formed by a wet solidification method, and the foam layer is ground. The foam layer is laminated on the support layer with the back surface of the foam layer facing the support layer, and the surface of the foam layer is used as the holding surface of the workpiece, and the height difference in the filtered waviness curve of the surface of the foam layer is , 12 μm or less.

JP-A-2008-23625

As described above, conventionally, it was thought that the quality of the holding surface of the holding pad, which holds the object to be polished, would be improved if only the flatness of the holding surface was ensured. However, as the inventors of the present invention proceeded with their studies, it was found that it is difficult to improve the flatness of the polished surface of the resulting object to be polished, even if polishing is performed using a holding pad that ensures only the flatness of the holding surface. I understand. Therefore, a means for improving the flatness of the surface to be polished is required in addition to the flatness of the holding surface. The inventors of the present invention have studied how the factors that make it difficult to improve the flatness of the surface to be polished correspond to the quality of the holding surface of the holding pad. It was confirmed that the holding pad used when it was difficult to improve the properties had color unevenness on the holding surface.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a holding pad that can improve the flatness of the surface to be polished of the object to be polished with less color unevenness on the holding surface.

As a result of intensive studies to solve the above-described problems of the prior art, the present inventors have found that a resin sheet having a holding surface for holding an object to be polished is provided, and the holding surface of the resin sheet is measured by a predetermined measuring method. Using a holding pad whose coefficient of variation (CV(ΔL*)) of the lightness index (ΔL*) calculated from them by a predetermined formula is less than 1.0 Therefore, the present inventors have found that the color unevenness of the holding surface is small and the flatness of the polished surface of the object to be polished can be improved, and the present invention has been completed.

That is, the present invention is as follows.
[1]
Equipped with a resin sheet having a holding surface for holding the object to be polished,
In the resin sheet, the coefficient of variation of the lightness index of the holding surface calculated from the following formula (1) is less than 1.0.
holding pad.
CV(ΔL*)=SD(ΔL*)/AVE(ΔL*) (1)
(In the formula, ΔL* conforms to JIS Z 8722: 2000, and in L*a*b* color space, an arbitrary reference point on the holding surface of the resin sheet and the holding surface with respect to the reference point CV (ΔL*) is the coefficient of variation of ΔL*, and SD (ΔL*) is ΔL*. , and AVE (ΔL*) indicates the arithmetic mean of ΔL*.)
[2]
The coefficient of variation is 0.9 or less,
The holding pad according to [1].
[3]
wherein the standard deviation is 0.10 or less;
The holding pad according to [1] or [2].
[4]
The arithmetic average is 0.20 or less,
The holding pad according to any one of [1] to [3].
[5]
In the resin sheet, the surface roughness of the holding surface measured in accordance with JIS B 0601:1994 is 1.0 μm or less.
The holding pad according to any one of [1] to [4].
[6]
The resin sheet contains a pigment,
The holding pad according to any one of [1] to [5].
[7]
The resin sheet contains a polyester-based polyurethane resin,
The holding pad according to any one of [1] to [6].
[8]
wherein the resin sheet contains a hydrophobic additive;
The holding pad according to any one of [1] to [7].
[9]
Further comprising a substrate on the side opposite to the holding surface of the resin sheet,
The holding pad according to any one of [1] to [8].
[10]
A method for manufacturing the holding pad according to any one of [1] to [9],
A step of preparing a resin solution containing a resin using a stirring device having a stirring blade;
and forming a resin sheet from the resin solution.
[11]
The method for producing a holding pad according to [10], wherein the shear rate of the resin solution by the stirring blade is 10 to 100/sec.
[12]
The method for manufacturing a holding pad according to [10] or [11], wherein the resin solution is stirred for 900 seconds or longer with the stirring blade.

The holding pad according to the present invention has little color unevenness on the holding surface, and can improve the flatness of the polished surface of the object to be polished.

It is a sectional view showing typically an example of a holding pad of this embodiment. FIG. 4 is a schematic diagram showing measurement points of lightness index: ΔL* with respect to the holding surface of the holding pad of the present embodiment.

Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as "this embodiment") will be described in detail with reference to the drawings as necessary, but the present invention is limited to the following embodiment. not a thing Various modifications are possible for the present invention without departing from the gist thereof. In the drawings, the same elements are denoted by the same reference numerals, and overlapping descriptions are omitted. In addition, unless otherwise specified, positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings. Furthermore, the dimensional ratios of the drawings are not limited to the illustrated ratios.

The holding pad of this embodiment includes a resin sheet having a holding surface for holding an object to be polished. Such a holding pad can be produced, for example, by attaching a double-sided tape comprising an adhesive layer and a release sheet to the side opposite to the holding surface of the resin sheet.

FIG. 1 is a cross-sectional view schematically showing an example of the holding pad of this embodiment. The holding pad 1 includes a polyurethane resin sheet 2 (hereinafter simply referred to as "resin sheet 2"). The resin sheet 2 has a holding surface P for holding the object to be polished, and the holding surface P is a contact body formed by pressurizing a film-like base material having a flat surface and being harder than the resin sheet 2 to adhere to it. is flattened by heat treatment. The rear side of the holding surface P is buffed or sliced so that the thickness of the resin sheet 2 (length in the vertical direction in FIG. 1) is substantially uniform. However, it does not have to be buffed or sliced.

The resin sheet 2 has a skin layer 4 formed with fine pores (not shown) on the holding surface P side. Formed inside the skin layer 4 are foams 3 having a rounded cross section and a substantially triangular shape along the thickness direction of the resin sheet 2 . Between the foams 3 of the resin sheet 3, foams 3 having a spatial volume larger than the micropores formed in the skin layer 4 and smaller than the foams 3 are formed. The foams 3 may be connected in a three-dimensional network with communicating pores larger than the diameter of the spatial volume of the microporous formed in the skin layer 4 . Since the back side of the holding surface P is buffed, the foam 3 is open on the buffed surface.

In addition, the holding pad 1 has a back side (buffed surface side) of the holding surface P, and one surface of the double-sided tape 7 for attaching the holding pad 1 to the polishing machine is coated with an adhesive on both sides of the base material. The other side of the double-faced tape 7 is covered with a release sheet 8. - 特許庁

In the resin sheet 2, the coefficient of variation (CV(ΔL*)) of the lightness index (ΔL*) of the holding surface P calculated from the following formula (1) is less than 1.0, preferably 0.9 or less. Yes, more preferably 0.6 or less, still more preferably 0.4 or less.
CV(ΔL*)=SD(ΔL*)/AVE(ΔL*) (1)
In the formula, CV (ΔL *) indicates the coefficient of variation of ΔL *, SD (ΔL *) indicates the standard deviation of ΔL *, AVE (ΔL *) indicates the arithmetic mean of ΔL *, ΔL * is JIS Z8722:
2000, in the L*a*b* color space, an arbitrary reference point on the holding surface P of the resin sheet 2 is moved vertically and horizontally with respect to the reference point at equal intervals of 20 cm each. Each brightness index at 20 points.
In order to obtain a holding pad in which the coefficient of variation (CV(ΔL*)) of the lightness index (ΔL*) of the holding surface is less than 1.0, the holding pad may be manufactured by the manufacturing method of the holding pad described later. .
A more specific method for measuring ΔL* will be shown in Examples described later.

When the coefficient of variation is less than 1.0, the color unevenness of the holding surface of the holding pad of the present embodiment is small and the flatness of the polished surface of the object to be polished can be improved. . However, the factor is not limited to this. Even if a conventional holding pad that ensures only the flatness of the holding surface is used, it may be difficult to improve the flatness of the surface to be polished in the object to be polished. This indicates that there are factors other than the low flatness of the holding surface of the holding pad that make it difficult to improve the flatness of the surface to be polished. As one of the main factors, it is speculated that the shape of the foam in the resin sheet causes minute and local variations in physical properties and composition on the holding surface. On the other hand, in the holding pad of the present embodiment, a plurality of lightness indices (ΔL*) are measured on the holding surface by a predetermined measurement method, and the coefficient of variation of the lightness index (ΔL*) calculated from them by a predetermined calculation formula When (CV(ΔL*)) is less than 1.0, even if minute and local physical property values and compositional variations on the holding surface, which are difficult to measure, are not directly obtained, the color unevenness of the holding surface is reduced. It is small and can improve the flatness of the surface to be polished.

In the resin sheet 2, the standard deviation of ΔL* is not particularly limited, but is preferably 0
. It is 10 or less, more preferably 0.05 or less, and still more preferably 0.02 or less. When the standard deviation of ΔL* is 0.10 or less, the color unevenness of the holding surface tends to be smaller, and the flatness of the surface to be polished can be further improved. The standard deviation of ΔL* is 0.0.
In order to obtain a holding pad of 10 or less, for example, the content of the pigment contained in the resin sheet 2 should be controlled.

In the resin sheet 2, the arithmetic mean of ΔL* is not particularly limited, but is preferably 0
. It is 20 or less, more preferably 0.15 or less, and still more preferably 0.10 or less. When the arithmetic average of ΔL* is 0.20 or less, the color unevenness of the holding surface tends to be smaller, and the flatness of the surface to be polished can be further improved. Here, ΔL* is a lightness index of the holding surface, and is a value obtained by indexing how dark it is toward black, which is the darkest color, with white, which is the brightest color, as a reference. Therefore, when the arithmetic mean of ΔL* is equal to or less than a predetermined value, it indicates that the color of the holding pad is relatively bright overall. In order to obtain a holding pad having an arithmetic mean of ΔL* of 0.20 or less, for example, the content of the pigment contained in the resin sheet 2 may be controlled.

In the resin sheet 2, the surface roughness of the holding surface P measured according to JIS B 0601:1994 is preferably 1.0 μm or less, more preferably 0.5 μm or less, and still more preferably 0.5 μm or less. 3 μm or less. When the surface roughness is 1.0 μm or less, the flatness of the surface to be polished tends to be further improved. In order to obtain a holding pad having a surface roughness of 1.0 μm or less, for example, the content of the pigment contained in the resin sheet 2 may be controlled.

Although the thickness of the resin sheet 2 is not particularly limited, it may be, for example, 0.2 to 1.5 mm, or 0.6 to 1.2 mm. The thickness of the resin sheet 2 is measured according to the measuring method described in JIS K6550:1994. That is, it is the thickness when a load of 100 g per 1 cm ² is applied (loaded) as an initial load in the thickness direction of the resin sheet 2 .

The resin sheet 2 has a plurality of bubbles 3 in a matrix-constituting material such as resin (hereinafter referred to as "matrix material"), and is formed by a so-called wet film-forming method. However, the resin sheet 2 can be changed to one formed by a known dry molding method or other molding method.

The matrix material constituting the resin sheet 2 has, for example, a composition containing the most polyurethane resin, and the resin sheet 2 contains 80 to 100% by mass of the polyurethane resin with respect to the total amount of the matrix material. There may be. The resin sheet 2 preferably contains 85 to 100% by mass, more preferably 90 to 100% by mass, and particularly preferably 90 to 95% by mass of the polyurethane resin relative to the total amount.

Polyurethane resins include, for example, polyester-based polyurethane resins, polyether-based polyurethane resins and polycarbonate-based polyurethane resins, and these may be used singly or in combination of two or more. Among these resins, polyester-based polyurethane resins are preferred from the viewpoint of achieving the object of the present invention more effectively and reliably.

The polyurethane resin may be synthesized by a conventional method, or may be commercially available. Examples of commercially available products include Crisbon (trade name, manufactured by DIC Corporation), Samprene (trade name, manufactured by Sanyo Chemical Industries, Ltd.), and Lezamin (trade name, manufactured by Dainippon Seika Kogyo Co., Ltd.). be done. Polyurethane resins are used singly or in combination of two or more.

The resin sheet 2 may contain other resins such as polysulfone resin and/or polyimide resin in addition to polyurethane resin. A polysulfone resin may be synthesized by a conventional method, or may be obtained from a commercial product. Commercially available products include, for example, Udel (trade name of Solvay Advanced Polymers Co., Ltd.). A polyimide resin may be synthesized by a conventional method, or may be obtained from a commercial product. Commercially available products include, for example, Aurum (trade name, manufactured by Mitsui Chemicals, Inc.).

The resin sheet 2 may be made of materials other than resin, such as pigments such as carbon black, hydrophilic additives such as sodium lauryl sulfate, etc. and hydrophobic additives such as polypropylene glycol, and one or more of water repellents. Furthermore, various materials such as solvents used in the manufacturing process of the resin sheet 2 may remain in the resin sheet 2 as long as they do not hinder the solution of the problems of the present invention.

The content of the pigment in the resin sheet 2 is preferably 0.1% by mass or more and 20% by mass or less, more preferably 1.0% by mass or more, relative to 100 parts by mass of the total solid content constituting the resin sheet 2. It is 15 mass % or less, more preferably 5.0 mass % or more and 10 mass % or less. When the content of the pigment is within the above range, the color unevenness of the holding surface, which is thought to be caused by disturbed uniformity of the air bubbles inside the resin sheet, tends to be smaller, and the flatness of the surface to be polished can be further improved. be.

The content of the hydrophobic additive in the resin sheet 2 is preferably 0.01% by mass or more and 20% by mass or less, more preferably 0.1% with respect to 100 parts by mass of the total solid content constituting the resin sheet 2. It is 10 mass % or more and more preferably 1.0 mass % or more and 5.0 mass % or less. When the content of the hydrophobic additive is within the above range, color unevenness on the holding surface, which is thought to be caused by disturbed uniformity of air bubbles inside the resin sheet, is reduced, and the flatness of the polished surface is further improved. tend to be able.

The content of the hydrophilic additive in the resin sheet 2 is preferably 0.01% by mass or more and 20% by mass or less, more preferably 0.1% with respect to 100 parts by mass of the total solid content constituting the resin sheet 2. % by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 3.0% by mass or less. When the content of the hydrophilic additive is within the above range, the color unevenness of the holding surface, which is thought to be caused by disturbed uniformity of the air bubbles inside the resin sheet, is reduced, and the flatness of the surface to be polished is further improved. tend to be able.

Micropores may exist in the holding surface P of the resin sheet 2 . Micropores can be formed, for example, by adding an additive that forms micropores in the holding surface (skin layer) during film formation of the resin sheet 2 .

The double-sided tape 7 may contain an adhesive or pressure-sensitive adhesive that is used in conventionally known holding pads. Materials of the double-sided tape 7 include, for example, adhesives such as acrylic, nitrile, nitrile rubber, polyamide, polyurethane, and polyester applied to both sides of a substrate. Also, the double-sided tape 7 may be of a non-support type that does not use a base material.

The release sheet 8 has a release property for preventing the double-sided tape 7 from being exposed to the surface when the holding pad 1 is transported or stored, and is not particularly limited, and can be separated from a conventional holding pad. It may be included as a template sheet. Examples of the release sheet 8 include paper in which the exposed surface Q is coated with a silicone-based or non-silicone-based release agent.

Here, the release sheet 8 in the holding pad 1 shown in FIG. 1 may be derived from the double-sided tape 7 provided therewith. The double-sided tape 7 has an adhesive layer and a release sheet containing an adhesive or a pressure-sensitive adhesive on both sides of the base material, and each adhesive layer and the base material is the double-sided tape 7, and one of the release sheets is the release sheet. It corresponds to seat 8. The other release sheet is peeled off when the double-sided tape 7 is joined to the resin sheet 2 .

Next, an example of a method for manufacturing the holding pad of this embodiment will be described. Here, a case where the resin sheet 2 is produced by a wet film-forming method will be described, but the method for producing the resin sheet 2 is not limited to this. This manufacturing method includes a step of preparing the resin sheet 2 and a step of bonding the double-sided tape 7 to the resin sheet 2 to obtain the holding pad 1 .

In the step of preparing the resin sheet 2, a resin solution containing a resin, a solvent, and optionally a pigment, a hydrophilic additive, and a hydrophobic additive is prepared using a stirring device equipped with stirring blades. It has a step (resin solution preparing step) and a step of molding the resin sheet 2 from the resin solution (molding step).
The step of forming the resin sheet 2 further includes a step of applying a resin solution to the surface of the film-forming substrate (application step) and a step of solidifying and regenerating the resin in the resin solution to form a precursor sheet. (solidification regeneration step), a step of removing the solvent from the precursor sheet to obtain the resin sheet 2 (solvent removal step), and a step of grinding and/or partially removing the resin sheet 2 by buffing or slicing (grinding・removal step). Each step will be described below.

First, in the resin solution preparation step, a resin such as the above-described polyurethane resin, a solvent capable of dissolving the resin and being mixed with the coagulating liquid described later, and, if necessary, a pigment and a hydrophilic additive are added to the resin sheet 2. And hydrophobic additives and other materials (e.g., pore-forming agents, water repellents, etc.) are mixed using a stirring device equipped with stirring blades, and if necessary, defoaming under reduced pressure to obtain a resin. Prepare the solution. Examples of the solvent include, but are not limited to, N,N-dimethylformamide (hereinafter referred to as "DMF") and N,N-dimethylacetamide. The content of the resin with respect to the total amount of the resin solution is not particularly limited, but may be, for example, in the range of 10 to 50% by mass, or in the range of 15 to 35% by mass.

The conditions for mixing using a stirring device equipped with stirring blades are not particularly limited as long as the holding pad of the present embodiment can be obtained. /sec, more preferably 20 to 80/sec, still more preferably 30 to 70/sec. The shear rate here is synonymous with the shear rate in a known stirrer equipped with stirring blades.

The shear rate can be obtained as follows. That is, the shear rate is shear rate (/ sec) = blade tip diameter (mm) of the stirring blade × circumference ratio × rotation speed (rpm) of the stirring blade / 60 / blade tip of the stirring blade and the inner wall of the mixing tank. can be obtained from the clearance (mm) of

Furthermore, the stirring time (seconds) for the resin solution with the stirring blade is preferably 900 seconds or more, more preferably 1800 to 18000 seconds, and even more preferably 3000 to 15000 seconds.

By setting the shear rate, the number of times of shearing, and the stirring time within the above ranges, the holding surface P of the resin sheet 2 has a small variation in physical property values and compositions in a minute range. Color unevenness is smaller, and the flatness of the surface to be polished tends to be more improved.

Next, in the coating step, the resin solution is applied to the surface of the belt-shaped film-forming substrate using a coating device such as a knife coater, preferably at room temperature, to form a coating film. The thickness of the resin solution applied at this time may be appropriately adjusted so that the thickness of the finally obtained resin sheet 2 is a desired thickness. Examples of materials for the film-forming substrate include resin films such as PET films, fabrics, and non-woven fabrics. Among these, a resin film such as a PET film, which hardly permeates liquid, is preferable.

Next, in the coagulation regeneration step, the coating film of the resin solution applied to the film-forming substrate is continuously guided into a coagulation liquid containing a poor solvent for the resin (for example, water in the case of polyurethane resin) as a main component. . An organic solvent such as a polar solvent such as the solvent in the resin solution may be added to the coagulation liquid in order to adjust the regeneration rate of the resin. Also, the temperature of the coagulating liquid is not particularly limited as long as it is a temperature at which the resin can be coagulated. In the coagulating liquid, first, a coating (skin layer) is formed on the interface between the coating film of the resin solution and the coagulating liquid, and countless fine pores are formed in the resin in the immediate vicinity of the coating. After that, due to the cooperative phenomenon of the diffusion of the solvent contained in the resin solution into the coagulating liquid and the infiltration of the poor solvent into the resin, regeneration of the resin, which preferably has an open-cell structure, proceeds. At this time, if the substrate for film formation is a material that does not allow the liquid to permeate easily (for example, PET film), the coagulation liquid will not permeate the substrate. , and larger pores tend to be formed in the region inside the skin layer than in the vicinity of the skin layer. Thus, a precursor sheet is formed on the film-forming substrate.

Next, in the solvent removing step, the resin sheet 2 is obtained by removing the solvent remaining in the formed precursor sheet. A conventionally known washing liquid can be used to remove the solvent. Moreover, the resin sheet 2 after removing the solvent may be dried if necessary. For drying the resin sheet 2, for example, a cylinder dryer having a cylinder with a heat source inside can be used, but the drying method is not limited to this. When using a cylinder dryer, the precursor sheet is dried by passing along the peripheral surface of the cylinder. Furthermore, the obtained resin sheet 2 may be wound into a roll.

Next, in the grinding/removal step, the back surface of the resin sheet 2, which is preferably the side opposite to the skin layer side, is ground and/or partially removed by buffing or slicing. Since the thickness of the resin sheet 2 can be made uniform by buffing or slicing, the pressure applied to the object to be polished can be made more uniform, further suppressing damage to the object to be polished and improving the flatness of the object to be polished. can be improved.

Next, the holding pad 1 is obtained by joining the double-sided tape 7 to the resin sheet 2 . In this step, for example, using a double-sided tape having a base material and an adhesive layer, the double-sided tape is bonded to the surface of one resin sheet 2 opposite to the holding surface P via the adhesive layer. Furthermore, the other adhesive layer of the double-sided tape and a release sheet are provided on the side opposite to the side where the double-sided tape is bonded to the resin sheet 2 . Thus, the holding pad 1 is obtained by laminating the double-faced sheet 7 and the release sheet 8 in this order on one surface of the resin sheet 2 .

Although the present embodiment has been described in detail above, the present invention is not limited to the above-described present embodiment. For example, in the present embodiment described above, the double-sided sheet 7 containing a base material is used as the resin sheet 2, but a non-supporting adhesive tape may be used instead. However, from the viewpoint of handleability of the holding pad, it is preferable that the holding pad of the present invention further includes a double-sided tape 7 containing a base material. Further, in the manufacturing method of the holding pad, the grinding/removing step may be omitted.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples.

(Example 1)
50 parts by mass of DMF for viscosity adjustment, 8 parts by mass of water, 44 parts by mass of a DMF dispersion containing 6.7% by mass of carbon black as a pigment, 2.5 parts by mass of polypropylene glycol as a hydrophobic additive, and 1.0 part by mass of sodium lauryl sulfate as a hydrophilic additive were mixed with a stirring blade. After stirring for 1 hour at a shear rate of 60/sec with a stirring blade, the mixture was retained in the stirring device for a predetermined time.

Next, a commercially available PET film was prepared as a substrate for film formation, and the prepared resin solution was applied thereon using a knife coater to obtain a coating film having a thickness of 1.0 mm. Next, the obtained coating film was immersed in a 18° C. coagulating bath containing water as a coagulating liquid to coagulate and regenerate the resin, together with the film-forming substrate, to obtain a precursor resin sheet. After removing the precursor resin sheet from the coagulation bath and peeling off the film-forming base material from the precursor resin sheet, the precursor resin sheet is immersed in a room-temperature cleaning liquid (desolvent bath) consisting of water, dried and wound up. rice field. Next, buffing was performed on the back surface of the resin sheet (the surface on the side where the film-forming base material was removed and the surface was in contact with the film-forming base material) to obtain a thickness of 0.8 mm. bottom.
Next, a double-faced tape composed of a commercially available PET substrate and a commercially available release sheet was attached to the buffed surface of the resin sheet to obtain a holding pad.

(Example 2)
A holding pad was produced in the same manner as in Example 1, except that the shear rate of the stirring blade was changed to 23/sec.

(Comparative example 1)
A holding pad was produced in the same manner as in Example 1, except that the shear rate of the stirring blade was changed to 8.5/sec.

(Comparative example 2)
A holding pad was produced in the same manner as in Example 1, except that the stirring time was changed from 1 hour to 5 minutes.

The lightness index (Δ
L*) and surface roughness were measured by the following methods.

(Brightness index: ΔL*)
Based on JIS Z 8722:2000, the measurement was performed using a spectral colorimeter (manufactured by Nippon Denshoku Co., Ltd., SD6000). The portion of the holding pad that was measured will be described with reference to a schematic diagram showing measurement points of the lightness index: ΔL* for the holding surface of the holding pad of the present embodiment. Here, in the holding surface of FIG. 2, the horizontal direction indicates the film formation direction of the holding pad, and the vertical direction indicates the direction perpendicular to the film formation direction.
Lightness index in CIE1976L*a*b* color space: The value of ΔL* is measured along the direction of each dotted arrow on the holding surface shown in FIG. , and 10 points moved by 20 cm at equal intervals in the vertical and horizontal directions with respect to the reference point, totaling 21 points. The measurement conditions were CIE standard light source D65, a viewing angle of 10°, and regular reflection light was excluded.

(Variation coefficient of ΔL*: CV)
From each lightness index: ΔL* obtained above, the arithmetic mean and standard deviation were calculated, and the coefficient of variation of ΔL*: CV was calculated from the following formula (1). Table 1 shows the results obtained.
CV(ΔL*)=SD(ΔL*)/AVE(ΔL*) (1)
In the formula, CV(ΔL*) indicates the coefficient of variation of ΔL*, SD(ΔL*) indicates the standard deviation of ΔL*, and AVE(ΔL*) indicates the arithmetic mean of ΔL*.

(Surface roughness (unit: μm))
Measurement was performed using a surface roughness measuring machine (Surfcom 480B, manufactured by Tokyo Seimitsu Co., Ltd.) in accordance with JIS B 0601:1994 of Japanese Industrial Standards. Specifically, five sections of the holding surface of the holding pad were measured at a measurement speed of 0.6 mm/sec and a measurement distance of 4 mm, and the average value was taken as the surface roughness (unit: μm). A cut-off value of 0.8 mm was used, and values above that were excluded from the measured values.

In Examples 1 and 2, as compared with Comparative Examples 1 and 2, the coefficient of variation: CV calculated as an index of color unevenness on the holding surface of the holding pad was small, indicating that color unevenness was suppressed.

Glass substrates were polished under the following polishing conditions using the holding pads of each example and comparative example.
(polishing conditions)
Object to be polished: Glass substrate for LCD (355 mm × 406 mm × 0.5 mm)
Polishing machine: Oscar polishing machine (manufactured by Speedfam, SP-1200)
Slurry: Cerium slurry Polishing speed (rotation speed): 61 rpm
Processing pressure: 76 gf/cm ²
Polishing time: 30min x 20 times

(flatness)
After performing the above-mentioned polishing process, when using each holding pad, the surface to be polished of the glass substrate surface after polishing process is measured from the center waviness of the filtered filter in accordance with Japanese Industrial Standards JIS B0601: '82. Flatness a was measured. In the measurement of the flatness a, a surface roughness profiler (Surfcom 480A, manufactured by Tokyo Seimitsu Co., Ltd.) was used under the following measurement conditions.

From the measurement curve obtained due to the unevenness of the surface of the glass substrate after polishing, the width W between the adjacent convex portions (mountain portions) and the height between the convex portions and the concave portions (valley portions) are determined. After calculating S, a scatter diagram was created with the width W as the horizontal axis and the height S as the vertical axis. From the obtained scatter diagram, an approximation straight line of the linear expression S=aW was obtained, and the slope a was taken as the final flatness a after polishing. In general, the higher the flatness, the larger the width W and the smaller the height S. Therefore, the smaller the slope a, the better the flatness.

In Examples 1 and 2, compared with Comparative Examples 1 and 2, it was found that the flatness a of the surface to be polished of the object to be polished can be improved.

DESCRIPTION OF SYMBOLS 1... Holding pad 2... Resin sheet 3... Foaming 4... Skin layer 7... Double-sided tape 8... Release sheet P... Holding surface B... Reference point.

INDUSTRIAL APPLICABILITY The present invention has industrial applicability as a holding pad for an object to be polished in the polishing field.

Claims (11)

Equipped with a resin sheet having a holding surface for holding the object to be polished,
In the resin sheet, the coefficient of variation of the lightness index of the holding surface calculated from the following formula (1) is 0.835 or less ,
holding pad.
CV(ΔL*)=SD(ΔL*)/AVE(ΔL*) (1)
(In the formula, ΔL* conforms to JIS Z 8722: 2000, and in L*a*b* color space, an arbitrary reference point on the holding surface of the resin sheet and the holding surface with respect to the reference point CV (ΔL*) is the coefficient of variation of ΔL*, and SD (ΔL*) is ΔL*. , and AVE (ΔL*) indicates the arithmetic mean of ΔL*.) wherein the standard deviation is 0.10 or less;
The retention pad of Claim 1 . The arithmetic average is 0.20 or less,
3. A retaining pad according to claim 1 or 2 . In the resin sheet, the surface roughness of the holding surface measured in accordance with JIS B 0601:1994 is 1.0 μm or less.
A retaining pad according to any one of claims 1-3 . The resin sheet contains a pigment,
A retaining pad according to any one of claims 1-4 . The resin sheet contains a polyester-based polyurethane resin,
A retaining pad according to any one of claims 1-5 . wherein the resin sheet contains a hydrophobic additive;
A retaining pad according to any one of claims 1-6 . Further comprising a substrate on the side opposite to the holding surface of the resin sheet,
A retaining pad according to any one of claims 1-7 . A method for manufacturing the holding pad according to any one of claims 1 to 8 ,
A step of preparing a resin solution containing a resin using a stirring device having a stirring blade;
and forming a resin sheet from the resin solution. 10. The method for producing a holding pad according to claim 9 , wherein the shear rate of the resin solution by the stirring blade is 10 to 100/sec. The method for manufacturing a holding pad according to claim 9 or 10 , wherein the resin solution is stirred for 900 seconds or longer with the stirring blade.

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