JP2011011292A - Holding pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a holding pad that stabilizes the foam shape so as to improve flatness of an object to be polished.SOLUTION: The holding pad 10 has a foam sheet 2 made of a urethane resin. The foam sheet 2 has a continuous foam structure formed by a wet film-forming method. The foam sheet 2 contains aggregates 5 in which carbon-black structures 9 are aggregated. The aggregate 5 is covered with an ABS resin of a dispersant. The aggregate 5 is configured such that a dispersion state measured by a grind-gauge distribution chart method is limited to ≤3.0 μm. The aggregates 5 are approximately uniformly dispersed without forming large aggregates, respectively, which are formed due to further agglomeration of the aggregates 5 during the wet film-formation.

Description

  The present invention relates to a holding pad, and more particularly to a holding pad provided with a urethane resin foam sheet formed by a wet film forming method.

  Conventionally, in materials that are required to have flatness with high accuracy, such as optical materials such as lenses, parallel flat plates, and reflective mirrors, aluminum substrates for hard disks, silicon wafers for semiconductor devices, and glass substrates for liquid crystal displays, Polishing using a polishing pad is performed. In semiconductor devices, miniaturization and multilayer wiring for the purpose of increasing the density of semiconductor circuits have progressed, and techniques for flattening silicon wafers have become important. As the size of liquid crystal displays increases, higher flatness of glass substrates is required. Usually, for polishing these objects to be polished, a single-side polishing machine for polishing the objects to be polished one side at a time, a double-side polishing machine for simultaneously polishing both surfaces of the objects to be polished, and the like are used. In a single-side polishing machine, one surface of the object to be polished is held on a holding surface plate having a flat surface, and the other surface side of the object to be polished is supplied with a polishing liquid by a polishing pad attached to the surface plate having a flat surface. Polishing is performed on the (processed surface).

  Generally, in a polishing process using a single-side polishing machine, a soft cloth or the like is used on the holding surface plate in order to avoid scratches (scratches) on the surface of the object to be polished, which are caused when the object is in direct contact with a metal holding surface plate The holding pad is installed. Usually, a urethane resin foam sheet formed by a wet film forming method is used for the holding pad. In the wet film forming method, a resin solution in which a urethane resin is dissolved in a water-miscible organic solvent is applied to a sheet-shaped film forming substrate, and then the resin is solidified and regenerated into a sheet form in an aqueous coagulating liquid. In the obtained foamed sheet, a large number of foams are formed in the interior due to the solidification regeneration of the urethane resin. That is, it has a surface layer (skin layer) in which micropores are formed on the surface (holding surface) side of the foam sheet, and foam is continuously formed inside the surface layer. Since the surface layer in which micropores are densely formed has a flat surface and excellent contact with the object to be polished, the object to be polished can be held. In such a foam sheet, when the foam size variation formed inside or uneven foam formation occurs, physical properties such as elasticity of the foam sheet are not stable, and high flatness of the workpiece can be obtained. It becomes difficult. In order to stabilize foam formation, an additive such as carbon black may be added to the resin solution.

  On the other hand, in the case of a holding pad using a foam sheet formed by a wet film formation method, in order to reinforce its physical strength and facilitate handling, a foam sheet is directly placed on a rigid support instead of a film formation substrate. May form. However, the foam sheet has a weak bonding force with the rigid support and peels off. This is thought to be caused by the fact that carbon black or the like is blended in the urethane resin that is inherently adhesive in order to stabilize the foamed shape. That is, in carbon black, it is known that active oxygen-containing groups such as carboxyl group, phenol group, carbonyl group, and quinone group exist on the surface, and this active oxygen-containing group interacts with urethane resin, Moreover, since the cohesion force between the urethane groups of the urethane resin becomes strong, the bonding force of the urethane resin to the rigid support is reduced.

  In order to prevent the foamed sheet from peeling off from the rigid support, the foamed sheet produced on the film-forming substrate was forcibly peeled off from the film-forming substrate and reattached to the rigid support with an adhesive. In this case, since the foam sheet is laminated on the rigid support through the adhesive, it is difficult to improve the polishing accuracy of the wafer due to variations in the application thickness of the adhesive used and lack of flatness. Disadvantages arise. On the other hand, a foamed sheet directly bonded to a rigid support having excellent thickness accuracy (for example, polyethylene terephthalate) is prepared by blending a vinyl polymer together with carbon black in a urethane resin solution. A technique is disclosed (see Patent Document 1). With this technology, it is not necessary to peel the foam sheet from the film-forming substrate and re-adhere it to another rigid support, and the active groups on the surface of the carbon black are consumed by the interaction between the carbon black and the vinyl polymer. The urethane group does not interact with the active group on the surface of the carbon black, and the cohesive force of the urethane group is weakened by the vinyl group. For this reason, the number of urethane groups in which the ester groups and van der Waals forces on the polyethylene terephthalate surface of the rigid support are bonded by hydrogen bonding increases, and a strong bonding force is obtained between the foamed sheet and the rigid support. Moreover, in addition to blending carbon black with urethane resin, a technique for hydrophilizing (wetting) the surface of a silicon wafer by blending a vinyl polymer is disclosed (for example, see Patent Document 2). .

Japanese Patent Publication No. 5-20268 JP 2004-335713 A

  However, although the technique of Patent Document 1 can suppress peeling between the foam sheet and the rigid support, the carbon black to be blended with the urethane resin is not limited. For this reason, since the carbon black contained in the obtained foamed sheet has an active group on the surface as described above and easily forms an aggregate of particles, the primary aggregate in which several to several tens of carbon black particles are aggregated is formed. In addition to forming aggregates (aggregates), secondary aggregates (agglomerates) in which primary aggregates further aggregate may be formed. The secondary agglomerates are usually several tens to several hundreds of μm in size, and when such secondary agglomerates are contained in the foamed sheet, the dispersibility of the agglomerates deteriorates and the size of the foam is reduced. Variation and uneven foam formation may occur. Moreover, although the technique of patent document 2 can achieve surface hydrophilization of a to-be-polished object, there exists a problem similar to patent document 1 by mix | blending carbon black. In other words, the foamed sheet having a variation in the foamed structure does not exhibit elasticity evenly, and there is a risk that flatness may be impaired when the object to be polished is held through the foamed sheet and polished.

  An object of the present invention is to provide a holding pad capable of stabilizing the foam shape and improving the flatness of an object to be polished in view of the above-mentioned cases.

  In order to solve the above problems, the present invention provides a holding pad including a urethane resin foam sheet formed by a wet film formation method, wherein the foam sheet has an aggregate of amorphous carbon particles agglomerated. It is contained, The said aggregate is coat | covered with the dispersing agent which disperse | distributes the said aggregate in the said foam sheet, It is characterized by the above-mentioned, It is characterized by the above-mentioned.

  In the present invention, the foamed sheet made of urethane resin contains agglomerated aggregates of amorphous carbon particles in the foamed sheet and is coated with a dispersing agent in a substantially uniformly dispersed state. Since the foamed shape can be stabilized and the object to be polished is held substantially flat, the flatness of the object to be polished can be improved.

  In this case, the size of the aggregate is preferably 3.0 μm or less. Amorphous carbon may be carbon black. Carbon black may be at least one selected from channel black, furnace black, and acetylene black. The dispersant may be at least one selected from acrylonitrile / styrene / butadiene resin, polyurethane, styrene / butadiene resin, cellulose acetate, and vinyl compound. At this time, the vinyl compound can be a non-halogen compound. The aggregate may be formed by agglomerating a primary aggregate formed by agglomeration of carbon black particles.

  According to the present invention, the foamed sheet made of urethane resin contains agglomerated aggregates of amorphous carbon particles in a foamed sheet and is coated with a dispersant in a substantially uniformly dispersed state. Therefore, the foamed shape can be stabilized, and the object to be polished is held substantially flat, so that the flatness of the object to be polished can be improved.

It is sectional drawing which shows typically the holding pad of embodiment to which this invention is applied. It is explanatory drawing which shows typically the structure of the carbon black particle contained in the holding pad of embodiment. It is process drawing which shows the outline of the manufacturing process of the holding pad of embodiment.

  Hereinafter, embodiments of a holding pad to which the present invention is applied will be described with reference to the drawings.

(Holding pad)
As shown in FIG. 1, the holding pad 10 of the present embodiment includes a foam sheet 2 formed of urethane resin. The foam sheet 2 has a substantially flat holding surface P for holding an object to be polished.

  In the foamed sheet 2, a dense micropore (not shown) is formed on the holding surface P side, and a skin layer 4 having micro flatness is formed. Inside the skin layer 4 (inside the urethane resin), a foam 3 having a triangular cross section rounded along the thickness direction of the foam sheet 2 is formed. The size of the foam 3 is smaller on the holding surface P side than on the surface side opposite to the holding surface P. In the urethane resin between the foams 3, foams that are larger than the micropores formed in the skin layer 4 and smaller than the foams 3 are omitted. The foam 3 and the foam (not shown) are connected in a mesh pattern with communication holes (not shown) larger than the microporous diameter formed in the skin layer 4. That is, the foam sheet 2 has a continuous foam structure formed by a wet film forming method. The foamed sheet 2 contains an aggregate 5 in which carbon black particles are aggregated. Aggregate 5 is dispersed substantially uniformly in foam sheet 2.

  Here, the carbon black aggregate 5 will be described. As shown in FIG. 2, carbon black has a complicated structure in which a plurality of spherical carbon black particles are fused, and in this example, a structure in which these particles are connected (primary aggregate) is referred to as a structure 9. . This is because active functional groups such as hydroxyl groups and carboxyl groups are present on the surface of the carbon black particles, and interaction between these functional groups works. In the structure 9, several to several tens of carbon black particles are usually aggregated and have a size of several tens to several hundreds of nanometers. The structure 9 is further aggregated to form an aggregate 5 (secondary aggregate).

  The size of the structure 9 is indirectly represented by the oil absorption amount of Japanese Industrial Standard (JISK6217-4, carbon black for rubber-basic characteristics-Chapter 4: Determination of oil absorption amount (including compressed sample)). . In the structure 9, the porosity and the size have a positive correlation. That is, since the voids increase as the number of carbon black particles constituting the structure 9 increases, the amount of oil absorbed in the voids of the structure 9 (oil absorption amount) also increases. An absorption meter is used to measure the oil absorption, and dibutyl phthalate (hereinafter abbreviated as DBP) or paraffin oil is used as the oil. In this example, the size of the structure 9 is represented by the DBP absorption amount measured using DBP.

  The aggregate 5 in which the structures 9 are aggregated is dispersed substantially uniformly in the foamed sheet 2, which is the aggregate 5 in the mixed liquid of the aggregate dispersion liquid and the urethane resin solution prepared in the preparation step (details will be described later). It is determined by the distributed state. In other words, the dispersion state of the aggregates 5 can be improved by suppressing the aggregation of the structures 9. This dispersion state is expressed in units of length according to a grind gauge distribution projection method of Japanese Industrial Standard (JIS K5600-2-5, Paint General Test Method-Part 2: Properties and Stability of Paint-Section 5: Dispersion). For example, it can be expressed by μm). In the grind gauge distribution projection method, measurement is performed using a gauge in which grooves (for example, 15, 25, 50, or 100 μm) having a uniform depth gradient from one end to the other end of zero depth are formed in the longitudinal direction.

  In the measurement of the dispersed state, a urethane resin solution is filled in the groove of the gauge using a scraper, and a scale indicating the depth of the groove at a position where particles are observed on the liquid surface is read. As a result, the dispersion state of the aggregate 5 present in the urethane resin solution is measured. In this example, the dispersion state of the aggregates 5 is adjusted to 3.0 μm or less by the grind gauge distribution projection method. Since the aggregate 5 is formed by the aggregation of the structure 9, when the size of the structure 9, that is, the DBP absorption amount increases, the dispersion state of the aggregate 5 may exceed 3.0 μm. For this reason, in Structure 9, it is preferable that the DBP absorption amount is 150 ml / 100 g or less.

  As the size of the structure 9 (DBP absorption amount) becomes smaller, the cohesive force becomes stronger and the dispersed state of the aggregate 5 becomes larger. For this reason, the aggregate 5 is coated with a dispersant for dispersing the aggregates. In the aggregate 5 coated with the dispersant, the active groups on the surface are consumed by the dispersant, so that the aggregate 5 is dispersed almost uniformly without further aggregation. That is, when the aggregate 5 is coated with the dispersant, the dispersion state becomes 3.0 μm or less. As the dispersant, one selected from acrylonitrile / butadiene / styrene (hereinafter abbreviated as ABS) resin, polyurethane, styrene / butadiene resin, cellulose acetate, and vinyl compound can be used. In this example, ABS resin is used as the dispersant.

  In addition, the holding pad 10 is bonded to the surface of the support 6 that supports the foamed sheet 2 on the surface opposite to the holding surface P. In this example, a sheet made of polyethylene terephthalate (hereinafter abbreviated as PET) is used as the support 6. On the other surface side of the support 6, the other surface side of the double-sided tape 7 having the release paper 8 on one surface side (the lowermost surface side) for attaching the holding pad 10 to the polishing machine is bonded.

(Manufacture of holding pads)
As shown in FIG. 3, the holding pad 10 is manufactured by laminating the foamed sheet 2 produced through each process of the wet film forming method to the support 6 and the double-sided tape 7 in the laminating process. In the wet film formation method, first, an aggregate dispersion obtained by mixing the aggregate 5 in which carbon black is aggregated in the preparation step and an ABS resin as a dispersant, and a water-miscible organic solvent N, N capable of dissolving the urethane resin. A urethane resin solution in which a urethane resin is dissolved in dimethylformamide (hereinafter abbreviated as DMF) is prepared. In the coating step, the aggregate dispersion liquid and the urethane resin solution are mixed, and the mixed liquid is applied to the film forming substrate. In the coagulation regeneration process, the urethane resin is coagulated and regenerated into a sheet. In the washing / drying step, the sheet-like polyurethane resin is washed and dried. The foam sheet 2 is produced through these steps. Hereinafter, it demonstrates in order of a process.

  In the preparation step, an aggregate dispersion liquid in which the aggregate 5 of carbon black and the ABS resin as a dispersant are mixed is prepared. The size of the aggregate 5 is preferably 3.0 μm or less. The amount of carbon black added is set to 5 to 20% by weight. The ABS resin is set to 0.2 to 2.0 times the amount of carbon black added. At this time, if the addition amount of the ABS resin is too small, improvement of the dispersion state of the aggregate 5 is hindered, and if it is too large, the physical properties of the foamed sheet 2 may be deteriorated. On the other hand, urethane resin, DMF and additives are mixed to dissolve the urethane resin. The urethane resin is selected from 100% modulus (tension when pulled twice) of a polyurethane resin such as polyester, polyether, polycarbonate, etc. having a viscosity of 20 Mpa or less. For example, the urethane resin is 30%. Dissolve in DMF. As the additive, a hydrophilic activator that promotes foaming, a hydrophobic activator that stabilizes the coagulation regeneration of the urethane resin, and the like can be used. The resulting solution is degassed under vacuum to obtain a urethane resin solution.

  In the coating process, a mixed liquid is prepared by mixing the aggregate dispersion liquid prepared in the preparation process and the urethane resin solution. By mixing the aggregate dispersion liquid in which the aggregates 5 are dispersed and the urethane resin solution, the aggregates 5 are dispersed in a state of being coated with the ABS resin in the obtained mixed liquid. The dispersion state of the aggregate 5 in the mixed solution is measured by the above-described grind gauge distribution method. In the mixed liquid of this example, the aggregate 5 was 1.5 μm or less. This mixed solution is applied substantially uniformly to the belt-shaped film forming substrate by a knife coater or the like at room temperature. At this time, the application thickness (application amount) of the urethane resin solution is adjusted by adjusting the gap (clearance) between the knife coater and the film forming substrate. Although the resin-made nonwoven fabric and film, such as PET resin, can be used for the film-forming substrate, in this example, the film-forming substrate is described as a PET sheet.

  In the coagulation regeneration step, the mixed solution applied to the film forming substrate is immersed in a coagulation solution containing water as a main component, which is a poor solvent for the urethane resin. In the coagulation liquid, first, micropores are formed on the surface side of the applied mixed liquid, and a skin layer having a thickness of about several μm is formed. Thereafter, the urethane resin coagulates and regenerates into a sheet form on the film forming substrate by the progress of substitution between the DMF in the mixed solution and the coagulating solution. When DMF is desolvated from the mixed liquid and DMF and the coagulating liquid are replaced, foam 3 and foam not shown are formed in the urethane resin inside the skin layer, and foam 3 and foam not shown are formed. It communicates in a mesh shape. At this time, since the PET sheet of the film forming substrate does not permeate water, desolvation occurs on the surface side (skin layer side) of the mixed solution, and a foam 3 having a larger film forming substrate side than the surface side is formed.

  In the washing / drying step, the urethane resin coagulated and regenerated in the coagulation regeneration step is washed in a cleaning solution such as water to remove DMF remaining in the urethane resin. After washing, the urethane resin is dried with a cylinder dryer to obtain the foam sheet 2. The cylinder dryer includes a cylinder having a heat source therein. The urethane resin is dried by passing along the peripheral surface of the cylinder.

  In the laminating step, the surface opposite to the holding surface P of the foam sheet 2 and one surface side of the support 6 are bonded together, and the release paper 8 is placed on the other surface side of the support 6 on the one surface side (lowermost surface side). Affix the affixed double-sided tape 7 together. The holding pad 10 is completed by performing an inspection such as confirming that there is no adhesion of dirt or foreign matter.

(Function)
Next, the operation and the like of the holding pad 10 of this embodiment will be described.

  In a holding pad provided with a foam sheet conventionally formed by a wet film formation method, carbon black is added to a resin solution at the time of wet film formation in order to stabilize foaming. However, since carbon black has an active functional group on the particle surface, it has the property of easily forming an aggregate. For this reason, large aggregates of carbon black are formed in the resin solution during wet film formation, and the large aggregates are unevenly distributed in the obtained foamed sheet. In a holding pad using such a foam sheet, variation in foam size and uneven foam formation may occur. For this reason, even if the object to be polished is held on the surface plate of the polishing apparatus via the holding pad, the elasticity of the foamed sheet is not stable during polishing, and it becomes difficult to hold the object to be polished flat. As a result, it is difficult to perform stable polishing, and the polishing efficiency is reduced. The present embodiment is a holding pad that can solve these problems.

  In the holding pad 10 of this embodiment, the aggregate 5 in which the structures 9 are aggregated is contained in the foamed sheet 2 in a state of being coated with the ABS resin as the dispersant. For this reason, since the aggregate 5 is dispersed substantially uniformly in the foam sheet 2 without forming a large aggregate that is further aggregated during wet film formation, the foam formation is stabilized and the size of the foam is equalized. The Thereby, since the foam sheet 2 is formed substantially uniformly, the object to be polished can be held substantially flat, and stable polishing can be performed without impairing the polishing efficiency.

  Further, in the holding pad 10 of the present embodiment, the size of the structure 9 is limited to 150 ml / 100 g or less in terms of DBP absorption, and the dispersion state of the aggregate 5 is further limited to 3.0 μm or less. Since the aggregates 5 are coated with the dispersant, the aggregates 5 are dispersed substantially uniformly without forming aggregates when the foamed sheet 2 is produced. Thereby, since physical properties, such as elasticity of the foam sheet 2, are stabilized, the flatness improvement of a to-be-polished object can be aimed at.

  Furthermore, in the holding pad 10 of this embodiment, since the dispersed state of the aggregates 5 is equalized in the foam sheet 2, foam formation can be stabilized. Thereby, since the tensile elongation of the foamed sheet 2 is improved, the breakage during the polishing process is suppressed, and the life of the holding pad 10 can be extended.

  In this embodiment, the carbon black (structure 9) aggregate is exemplified as the aggregate 5 to be contained in the foamed sheet 2, but the present invention is not limited to this, and an amorphous carbon material is used. I just need it. For example, amorphous carbon coal may be used instead of carbon black. In addition, there are various types of carbon black, such as channel black, furnace black, and acetylene black, depending on the production method thereof, but the present invention is not limited to the production method of carbon black, and any of these may be used. Also good. It is also possible to use a mixture of carbon blacks having different manufacturing methods.

  Further, in the present embodiment, an example in which the dispersion state of the aggregate 5 is measured by a grind gauge distribution projection method is shown, but the present invention is not limited to this. For example, a general particle size measurement method may be used as long as it can be confirmed that the dispersion state of the aggregate 5 is 3.0 μm or less. In consideration of confirming the dispersion state of the aggregate 5 during the manufacturing process, it can be easily confirmed by a grind gauge distribution projection method. Furthermore, in the present embodiment, an example in which the dispersion state of the aggregate 5 is set to 3.0 μm or less is shown. However, in consideration of further improving the dispersion state of the aggregate 5, the aggregate 5 is 1.5 μm or less. It is preferable that In this way, since the size of the aggregate 5 is further limited, the size of foaming and the stability of foam formation can be improved, and the flatness of the object to be polished can be further improved. Moreover, in this embodiment, although the example which represented the magnitude | size of the structure 9 by DBP absorption amount was shown, this invention is not restrict | limited to this, The magnitude | size of the structure 9 is 150 ml / 100g or less in DBP absorption amount. Anything can be used as long as it can be evaluated. The DBP absorption amount of the structure 9 is preferably 140 ml / 100 g or less, particularly preferably 130 ml / 100 g or less, considering the dispersion state of the aggregate 5.

  Furthermore, in this embodiment, although the example which uses an ABS resin as a dispersing agent was shown, this invention is not limited to this. For example, the above-described effects can be obtained even when polyurethane, styrene-butadiene resin, cellulose acetate, or vinyl compound is used in place of the ABS resin. Of course, two or more of these dispersants may be mixed and used. Moreover, when using a vinyl compound as a dispersing agent, it is preferable to use the non-halogen compound in which a halogen molecule is not contained. In this way, it is possible to reduce the influence on the environment when the holding pad is discarded.

  In the present embodiment, the urethane resin is solidified and regenerated by using the film-forming base material at the time of producing the foam sheet 2, and then the film-forming base material is peeled off to form the urethane foam 2 and the PET support 6. However, the present invention is not limited to this. For example, the urethane foam 2 may be directly coagulated and regenerated on the support 6 by using the support 6 instead of the film forming substrate during wet film formation. Since the aggregate 5 contained in the foamed sheet 2 is coated with the ABS resin, the influence of active groups present on the particle surface of the carbon black (structure 9) forming the aggregate 5 can be suppressed. That is, when the active group on the particle surface interacts with the urethane resin, the adhesive force between the urethane resin and the PET of the support 6 may be reduced and may be peeled off during polishing. On the other hand, in the aggregate 5 which is coated with ABS resin and suppresses the influence of the active group, the interaction with the urethane resin is reduced, so that the adhesive force between the foam sheet 2 and the support 6 can be secured. it can. The material of the support 6 is not limited to PET, and any material can be used as long as it is made of a resin having rigidity.

  Hereinafter, examples of the holding pad 10 manufactured according to the present embodiment will be described. The holding pad of the comparative example manufactured for comparison is also shown.

Example 1
In Example 1, a polyester MDI (diphenylmethane diisocyanate) polyurethane resin having a 100% modulus of 10 Mpa was used as the urethane resin. A urethane resin solution was prepared by dissolving 30% by weight of this polyurethane resin in DMF. Further, 20% by weight of the aggregate 5 and 20% by weight of the ABS resin were mixed with DMF to prepare an aggregate dispersion. The DBP absorption amount of the structure 9 forming the aggregate 5 was 130 ml / 100 g. 40 parts of the aggregate dispersion were mixed with 100 parts of the obtained urethane resin solution to obtain a mixed liquid. As a result of measuring the dispersion state of the aggregate 5 of this mixed liquid using a grind gauge distribution diagram, it was 1.5 μm or less. The foamed sheet 2 was produced from the obtained mixed solution by a wet film forming method, and the holding pad 10 was produced.

(Comparative Example 1)
In Comparative Example 1, a urethane resin solution in which the same polyurethane resin as in Example 1 was dissolved in DMF at 30% by weight was prepared. Further, 20% by weight of the aggregate 5 and 20% by weight of the ABS resin were mixed with DMF to prepare an aggregate dispersion. The DBP absorption of the structure forming the aggregate was 200 ml / 100 g. 40 parts of the aggregate dispersion were mixed with 100 parts of the obtained urethane resin solution to obtain a mixed liquid. As a result of measuring the dispersion state of the aggregate of the mixed solution using a grind gauge distribution projection method, it was 40 μm or less. A holding pad of Comparative Example 1 was produced in the same manner as in Example 1 except that this urethane mixed solution was used.

(Evaluation)
For each example and comparative example, the tensile strength and tensile elongation of the foamed sheet after wet film formation were measured. For the measurement, a tensile elongation measuring device (manufactured by A & D Co., Ltd., Tensilon universal testing machine RTC) was used. The measuring method was measured by a method according to Japanese Industrial Standard (JIS K6550). Moreover, the size of the aggregates when the surface of the skin layer of the foamed sheet after wet film formation was observed with a scanning electron microscope (SEM) was measured. The measurement results of tensile strength, tensile elongation and aggregate size are shown in Table 1 below.

As shown in Table 1, in the holding pad of Comparative Example 1, the foam sheet had a tensile strength of 0.10 kg / mm ² and a tensile elongation of 97%. For this reason, in the holding pad of Comparative Example 1, the foamed sheet may be broken during polishing. Moreover, in the foam sheet used in Comparative Example 1, the dispersion state of the contained aggregates was 40 μm or less, and the size of the aggregates when observed by SEM after wet film formation was 20 μm. The foamed sheet of Comparative Example 1 has an unstable foam shape due to low dispersibility of aggregates, and the object to be polished cannot be held substantially flat during polishing, and high-precision flatness is expected. difficult. In contrast, in the holding pad 10 of Example 1, the foamed sheet 2 has a tensile strength of 0.19 kg / mm ² and a tensile elongation of 221%, which is improved as compared with Comparative Example 1. It was. Moreover, in the foam sheet 2 used in Example 1, the dispersion state of the aggregate 5 was 1.5 μm or less, and the size of the aggregate 5 when observed by SEM after the wet film was 0.5 μm. This is presumably because the dispersibility was improved as compared with Comparative Example 1, the aggregates 5 were dispersed substantially uniformly, and the foam size and foam formation were stabilized. Therefore, it can be expected that the object to be polished is held substantially flat in the holding pad 10 and the flatness is improved. Such a holding pad 10 can be suitably used as a holding pad in polishing processing of a liquid crystal glass substrate or the like, for example.

  Since the present invention provides a holding pad that can stabilize the foam shape and improve the flatness of the object to be polished, it contributes to the manufacture and sale of the holding pad, and thus has industrial applicability. .

P holding surface 2 foam sheet 5 aggregate 10 holding pad

Claims (7)

  In a holding pad provided with a urethane resin foam sheet formed by a wet film-forming method, the foam sheet contains an aggregate in which amorphous carbon particles are aggregated, and the aggregate is the foam A holding pad, which is coated with a dispersing agent for dispersing the agglomerates in a sheet and dispersed substantially uniformly.   The holding pad according to claim 1, wherein the aggregate has a size of 3.0 μm or less.   The holding pad according to claim 1, wherein the amorphous carbon is carbon black.   The holding pad according to claim 3, wherein the carbon black is at least one selected from channel black, furnace black, and acetylene black.   The holding pad according to claim 1, wherein the dispersant is at least one selected from acrylonitrile / styrene / butadiene resin, polyurethane, styrene / butadiene resin, cellulose acetate, and vinyl compound.   The holding pad according to claim 5, wherein the vinyl compound is a non-halogen compound.   The holding pad according to claim 3, wherein the aggregate is formed by aggregating primary aggregates formed by aggregation of the carbon black particles.

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