JP2008168380A - Holding pad - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a holding pad easily detachable from and attachable to a polishing plate, and improving efficiency of an operation for exchanging a workpiece. <P>SOLUTION: The holding pad 1 has two polyurethane sheets 2, 3 formed of polyurethane resin. The polyurethane sheets 2, 3 have different compression rates. The polyurethane sheet 2 has a surface layer 2a on a holding face P side contacting a ground material. The polyurethane sheet 3 has a surface layer 3a on a mounting face Q side mounted to a surface plate. Back faces of the polyurethane sheets 2, 3 are bonded to each other. The holding pad 1 is mounted to the surface plate on a mounting face Q of the polyurethane sheet 3 with lower compression rate, and comes into contact with a workpiece on a holding face P of the polyurethane sheet 2 with higher compression rate. Deformation of the polyurethane sheet 3 is restrained in comparison with the polyurethane sheet 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a holding pad, and in particular, the back surfaces of two soft plastic sheets having a surface layer in which micropores are formed are bonded to each other and attached to a surface plate on one surface layer side. It is related with the holding pad which the surface layer side of this contacts a to-be-polished object.

  Conventionally, materials (objects to be polished) such as glass substrates for flat panel displays (FPD), color filters, and indium tin oxide (ITO) film-formed substrates require high-precision flatness. The used polishing process is performed. In general, a single-side polishing machine that polishes an object to be polished one side at a time is used for polishing the object to be polished. In this 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 of the object to be polished is supplied with a polishing liquid by a polishing cloth affixed to the polishing surface plate having a flat surface. Polishing is performed on the side (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. Scratching and the like can be avoided by interposing the holding pad between the object to be polished and the holding surface plate. However, if the holding pad has insufficient retention of the object to be polished, A lateral shift occurs and the object to be polished cannot be held flat. In order to prevent lateral displacement of the object to be polished, a carrier (formwork) having an opening into which the object to be polished can be inserted is affixed to the surface of the holding pad, and the object to be polished is inserted into the opening of the carrier. Polishing is performed. When the carrier is used, the object to be polished is removed from the carrier after the polishing process, but the object to be polished, particularly the glass substrate, is enlarged, and it is difficult to remove it from the carrier. For this reason, a carrier-less type that does not use a carrier is required for the holding pad, and in order to prevent lateral shift or dropping of the object to be polished, improvement of the object to be polished is desired.

  Usually, a soft plastic sheet having a surface layer in which micropores are formed and a foam layer in which foaming larger than the pore size of the micropores formed in the surface layer is continuously formed is used for the holding pad. This soft plastic sheet is obtained by applying a resin solution in which a soft plastic (resin) is dissolved in a water-miscible organic solvent to a sheet-form film-forming substrate, and then coagulating and regenerating the resin in an aqueous coagulation liquid (wet formation). Manufactured by the membrane method). Along with the coagulation regeneration, micropores constituting the surface layer are densely formed on the surface of the soft plastic sheet over a thickness of about several μm, and foams constituting the foam layer are 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. When polishing the workpiece, the holding pad is attached to the holding platen on the surface opposite to the surface layer, and the surface layer contains liquid such as water and presses the workpiece to penetrate into the micropores of the surface layer. The object to be polished is held by the action of the surface tension of the liquid.

  However, when holding the object to be polished, air may be caught between the object to be polished and the holding pad. Since the liquid that has penetrated into the micropores formed in the surface layer inhibits the movement of the entrained air toward the soft plastic sheet (foamed layer), the air is stored between the object to be polished and the holding pad. If polishing is performed while air is stored, the pressure applied to the object to be polished increases in the air storage part, so that the processing surface of the part is greatly polished (the air storage part is transferred to the object to be polished) and flat. It will damage the sex. In order to reduce the biting of air between the object to be polished and the holding pad, a technique for laminating an adhesive resin layer on the surface of a soft plastic sheet and forming irregularities on the surface of the adhesive resin layer is disclosed (for example, , See Patent Document 1).

  Moreover, since the soft plastic sheet formed into a wet film has flexibility, it is difficult to handle it when mounted on a holding surface plate or during transportation. Therefore, a substrate such as a polyester film is bonded to the holding pad. Since a double-sided tape is usually used for mounting on a holding surface plate, a soft plastic sheet, a base material, and a double-sided tape are laminated on the holding pad. As such a holding pad, for example, a technique using a double-sided tape in which an adhesive is applied to both surfaces of a base material such as a polyester film is disclosed (see Patent Document 2). In this technique, one side of a double-sided tape is bonded to a soft plastic sheet, and the other side is attached to a holding surface plate. In order to facilitate attachment to a holding surface plate and improve the biting of air, the present applicant discloses a holding pad in which the back surfaces of two soft plastic sheets are bonded together (see Patent Document 3).

JP 2002-355755 A JP 2005-011972 A JP 2006-326714 A

  However, the technique of Patent Document 1 has a drawback that the adhesive resin adheres to the object to be polished because the object to be polished contacts the surface of the adhesive resin layer. Further, in the technique of Patent Document 2, since the holding pad is attached to the holding surface plate with the double-sided tape, air may be caught between the holding pad and the holding surface plate. When air biting occurs between the holding pad and the holding surface plate, the flatness of the object to be polished is impaired by the polishing process in the same manner as when the air biting occurs between the object to be polished and the holding pad described above. Re-attachment of the holding pad is required. However, if the holding pad once attached with the double-sided tape is peeled off, wrinkles or the like are generated. In particular, since a large holding pad tends to cause air biting, it requires skill to attach to a holding surface plate. Also, if the holding pad is peeled off due to re-attachment or life, etc., the adhesive remains on the holding surface plate and impairs flatness.Therefore, the cleaning work to remove the remaining adhesive from the holding surface plate is necessary to install a new holding pad. It becomes necessary and the workability of attaching the holding pad is lowered. On the other hand, in the technique of Patent Document 3, a holding pad can be attached to a holding surface plate without using a double-sided tape, and the biting of air is reduced, but the object to be polished is removed from the holding pad after polishing. In addition, the holding pad may be peeled off from the holding surface plate before the workpiece is removed. In order to perform the polishing process continuously, it is necessary to attach a new holding pad to the holding surface plate, thereby reducing the life of the holding pad and reducing the work efficiency of the entire polishing process.

  An object of the present invention is to provide a holding pad that can be easily attached to and detached from a surface plate and can improve the efficiency of exchanging an object to be polished.

    In order to solve the above-mentioned problems, the present invention is such that the back surfaces of two soft plastic sheets having a surface layer formed with micropores are bonded to each other and attached to a surface plate on one surface layer side, In the holding pad in which the other surface layer side is in contact with the object to be polished, the soft plastic sheets have different compression ratios, and the surface layer side of the soft plastic sheet having the smaller compression ratio is placed on the surface plate. It is mounted.

  In the present invention, the two soft plastic sheets having a surface layer in which micropores are formed and the back surfaces are bonded to each other have different compression ratios, and the surface layer of the soft plastic sheet having the smaller compression ratio. Since the surface is attached to the surface plate on the side, the surface layer side of the soft plastic sheet having the higher compression rate abuts on the object to be polished during polishing and the object to be polished is held on the surface plate by the holding pad. Even if an external force is applied to the holding pad when removing the workpiece after polishing, the soft plastic sheet on the side that contacts the workpiece is easily deformed by the external force. Since the soft plastic sheet is not easily deformed, the object to be polished can be easily removed without the holding pad itself being detached from the surface plate, and the efficiency of the replacement work can be improved.

  In this case, each of the two soft plastic sheets has a foam layer in which foam having a pore size larger than the microporous formed in the surface layer is formed on the inner side of the surface layer, and is attached to the surface plate. If the foam formed in the foam layer of the sheet has a smaller pore diameter than the foam formed in the foam layer of the soft plastic sheet that contacts the object to be polished, the compression rate of the soft plastic sheet mounted on the surface plate can be reduced. The compression rate of the soft plastic sheet in contact with the object to be polished can be made smaller. At this time, the compression rate of the soft plastic sheet contacting the object to be polished may be 30% or more and 70% or less, and the compression rate of the soft plastic sheet attached to the surface plate may be 1% or more and less than 30%.

  Further, if the contact angle of water with respect to the surface of the surface layer of each soft plastic sheet is 105 ° or more, the water repellency of the surface of the soft plastic sheet is increased, and the holding pad and the surface plate or the object to be polished are Since the infiltration of the liquid such as the polishing liquid can be prevented during this period, it is possible to suppress a reduction in the mounting force of the holding pad to the surface plate and the holding power of the object to be polished. Moreover, the back surfaces of the soft plastic sheet may be bonded together with an adhesive member having a base material and a pressure-sensitive adhesive disposed on both surfaces of the base material. If the back side of the soft plastic sheet is buffed so that each soft plastic sheet has a uniform thickness, the surface of the surface layer of the soft plastic sheet becomes almost flat. An object can be held substantially flat.

  In such a soft plastic sheet, a pore having a pore size smaller than the foam formed in the foam layer and larger than the micropore formed in the surface layer is further formed on the surface layer. By communicating with the foam formed on the surface of the foamed layer, air can be introduced into the foamed layer through the perforation even if air is caught when the holding pad is attached to the surface plate or when the workpiece is brought into contact with the holding pad. Since the air is sucked in, the object to be polished can be held substantially flat without air being stored between the holding pad and the surface plate or the object to be polished. Such a holding pad may further include a carrier for preventing lateral displacement of the object to be polished during polishing.

  According to the present invention, the two soft plastic sheets having a surface layer in which micropores are formed and the back surfaces thereof are bonded to each other have different compression ratios. Since it is mounted on the surface plate on the surface layer side, the surface layer side of the soft plastic sheet with the higher compression rate abuts the object to be polished during polishing, and the object to be polished is held on the surface plate by the holding pad. Even if an external force is applied to the holding pad when the workpiece is later removed, the soft plastic sheet on the side contacting the workpiece is easily deformed by the external force, whereas the soft side on the surface plate is soft. Since the plastic sheet is not easily deformed, it is possible to easily remove the object to be polished without removing the holding pad itself from the surface plate, and to improve the efficiency of the replacement work. It is possible to obtain the results.

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

(Retention pad)
As shown in FIG. 1, the holding pad 1 has polyurethane sheets 2 and 3 as two soft plastic sheets formed of polyurethane resin. The polyurethane sheets 2 and 3 have different compression ratios.

  The polyurethane sheet 2 has a surface layer 2a disposed on the holding surface P side in contact with an object to be polished, and a foam layer 2b disposed on the inner side (inside the polyurethane sheet 2) than the surface layer 2a. In the surface layer 2a, dense micropores (not shown) are formed. In the foam layer 2b, a foam 7 having a substantially triangular cross section rounded along the thickness direction of the polyurethane sheet 2 is formed. The pore diameter of the foam 7 is formed such that the size on the holding surface P side is smaller than the back side of the holding surface P. In the polyurethane resin between the foams 7, foam (not shown) having a pore diameter larger than the micropores formed in the surface layer 2 a and smaller than the foam 7 formed in the foam layer 2 b is formed. The foam 7 and the foam (not shown) are connected in a three-dimensional network via communication holes (not shown).

  On the other hand, the polyurethane sheet 3 has a surface layer 3a disposed on the mounting surface Q side to be mounted on the holding surface plate, and a foam layer 3b disposed on the inner side (inside the polyurethane sheet 3) than the surface layer 3a. ing. In the surface layer 3a, dense micropores (not shown) are formed. In the foam layer 3b, substantially spherical foams 9 having a pore diameter larger than the micropore formed in the surface layer 3a and smaller than the foam 7 formed in the foam layer 2b of the polyurethane sheet 2 are formed substantially evenly. In the polyurethane resin between the foams 9, foam (not shown) having a pore diameter larger than the micropores formed in the surface layer 3 a and smaller than the foam 9 formed in the foam layer 3 b is formed. The foam 9 and the foam (not shown) are connected in a three-dimensional network via communication holes (not shown). For this reason, when each of the polyurethane sheets 2 and 3 is pressurized, the foam 7 of the polyurethane sheet 2 is deformed more than the foam 9 of the polyurethane sheet 3, so that the compressibility of the polyurethane sheet 3 (thickness when pressed) (Percentage of thickness before pressurization of the reduced amount) becomes smaller than that of the polyurethane sheet 2. The compression rate of the polyurethane sheet 2 is set, for example, in a range of 30% or more and 70% or less, and the compression rate of the polyurethane sheet 3 is set, for example, in a range of 1% or more and less than 30%.

  On the holding surface P (surface of the surface layer 2a) of the polyurethane sheet 2 and the mounting surface Q (surface of the surface layer 3a) of the polyurethane sheet 3, the foam 7 or foam layer 3b formed on the foam layer 2b, respectively. A porous 8 communicating with the foam 9 is further formed. The pore diameter of the pores 8 is larger than the micropores formed in the surface layers 2a and 3a, and smaller than the foam 7 formed in the foam layer 2b or the foam 9 formed in the foam layer 3b. The hole diameter of the communication hole that connects the pore 8 and the foam 7 or the foam 9 is formed larger than the microporous hole diameter of the surface layers 2a and 3a. The pores 8 are formed of a pore forming agent added to the polyurethane resin solution during wet film formation of the polyurethane sheets 2 and 3 described later. Further, the polyurethane sheets 2 and 3 are buffered so that the thickness of the polyurethane sheets 2 and 3 (the length in the vertical direction in FIG. 1) is uniform on the back side of the holding surface P and the back side of the mounting surface Q, respectively. Has been processed. For this reason, both surfaces of the holding pad 1, that is, the holding surface P and the mounting surface Q are substantially flat.

  Further, the polyurethane sheets 2 and 3 are provided with water repellency on the holding surface P and the mounting surface Q. Water repellency can be imparted by adding a water repellency additive to the resin solution during wet film formation. The degree of water repellency is such that the contact angle of water with respect to the holding surface P and the mounting surface Q is adjusted to 105 ° or more. The contact angle is an angle on the side containing the liquid among the angles formed by the tangent line drawn on the liquid at the contact point of the three phases and the solid surface when the solid, liquid and gas are brought into contact with each other.

  The two polyurethane sheets 2 and 3 having different compression ratios have the back surfaces thereof, that is, the back surface of the holding surface P and the back surface of the mounting surface Q are bonded together via a double-sided tape (adhesive member) 6. The double-sided tape 6 has a pressure-sensitive adhesive 5 coated on both surfaces of a base material 4 made of polyethylene terephthalate (hereinafter abbreviated as PET). For this reason, the holding pad 1 has surface layers 2a and 3a located on both sides, and is mounted on the surface plate of the polishing machine with the mounting surface Q of the polyurethane sheet 3 having the lower compression ratio, and the one having the higher compression ratio. The holding surface P of the polyurethane sheet 2 contacts the object to be polished.

(Manufacture of holding pads)
The holding pad 1 is manufactured through the respective steps shown in FIG. 2, and the polyurethane sheets 2 and 3 formed respectively in the preparation process to the cleaning / drying process are bonded in the bonding process through the buffing process. The production of the polyurethane sheet 2 and the production of the polyurethane sheet 3 will be described in this order.

  In the preparation step, polyurethane resin, N, N-dimethylformamide (hereinafter abbreviated as DMF), a water-miscible organic solvent capable of dissolving the polyurethane resin, and water-repellent addition for imparting water repellency to the holding surface P A polyurethane resin solution is prepared by mixing an agent and a pore-forming agent for forming the pores 8 on the holding surface P. For the polyurethane resin, a polyester resin, a polyether resin, a polycarbonate resin or the like having a 100% modulus (tension when pulling twice as long) is 20 MPa or less is used. For example, the polyurethane resin is 30%. Dissolve in DMF.

  As a pore-forming agent to be mixed with the polyurethane resin solution, a predetermined amount of a cellulose derivative which is soluble in DMF for dissolving the polyurethane resin and hardly soluble or insoluble in water is added. As the cellulose derivative, at least one selected from ester derivatives, ether derivatives, ether ester derivatives and aromatic-containing derivatives can be used. Examples of ester derivatives include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose valerate, and cellulose acetate butyrate. Examples of ether derivatives include ethyl cellulose and hydroxypropyl cellulose. Examples of ether ester derivatives include acetylethyl cellulose and acetoxypropyl cellulose. The addition amount of the cellulose derivative is set according to the pore diameter of the porous 8 on the surface (holding surface P) of the surface layer 2a.

  In order to impart water repellency, for example, a silicone-based or polyether-based water-repellent additive is mixed into the polyurethane resin solution. The blending amount of the water repellent additive is adjusted so that the contact angle of water with the holding surface P of the resulting polyurethane sheet 2 is 105 ° or more. In this example, the effect of imparting water repellency is obtained, and the blending amount of the water repellency additive is set to a polyurethane resin so as not to impede the attachment of the holding pad to the surface plate and the contact of the object to be polished with a liquid such as water 0.05 to 3.0 parts, preferably 0.1 to 1.0 parts, relative to 100 parts of the solution. The obtained solution is filtered to remove aggregates and the like, and then defoamed under vacuum to obtain a polyurethane resin solution.

  In the application process, the coagulation regeneration process and the washing / drying process shown in FIG. 2, the polyurethane resin solution obtained in the preparation process is continuously applied to a film formation substrate such as a nonwoven fabric, a woven fabric, or a flexible film, The polyurethane resin is coagulated and regenerated by immersing in an aqueous coagulating liquid, and after washing, dried to obtain a polyurethane sheet 2. The coating process, the coagulation regeneration process, and the cleaning / drying process are continuously executed by the film forming apparatus shown in FIG.

  As shown in FIG. 3, the film forming apparatus 60 is filled with a pretreatment liquid 15 such as water or a DMF aqueous solution (mixed liquid of DMF and water) for pretreating a nonwoven fabric or a woven fabric of a film forming substrate. In addition, the pretreatment tank 10, the coagulation tank 20 filled with a coagulation liquid 25 mainly composed of water which is a poor solvent for the polyurethane resin for coagulating and regenerating the polyurethane resin, and the polyurethane resin after the coagulation regeneration are washed. A cleaning tank 30 filled with a cleaning liquid 35 such as water and a cylinder dryer 50 for drying the polyurethane resin are continuously provided.

  On the upstream side of the pretreatment tank 10, a substrate supply roller 41 that supplies the film forming substrate 43 is disposed. In the pretreatment tank 10, a pair of guide rollers 13 is disposed at a lower portion inside the substantially central portion in the same longitudinal direction as the film forming substrate 43 is conveyed. Above the pretreatment tank 10, guide rollers 11 and 12 are disposed on the substrate supply roller 41 side, and on the coagulation tank 20 side, an excessive pretreatment liquid contained in the pretreated film formation substrate 43. A mangle roller 18 for removing 15 is disposed. On the downstream side of the mangle roller 18, a knife coater 46 for applying the polyurethane resin solution 45 to the film forming substrate 43 substantially uniformly is disposed. A guide roller 21 is disposed on the downstream side of the knife coater 46 and above the coagulation tank 20.

  In the coagulation tank 20, a guide roller 23 is disposed at the inner lower part on the cleaning tank 30 side. A mangle roller 28 is disposed on the washing tank 30 side above the coagulation tank 20 for dehydrating the polyurethane resin after coagulation regeneration. A guide roller 31 is disposed on the downstream side of the mangle roller 28 and above the cleaning tank 30. In the cleaning tank 30, four guide rollers 33 at the upper part and five guide rollers 33 at the lower part are arranged alternately in the vertical direction in the same longitudinal direction as the transport direction of the film forming substrate 43. A mangle roller 38 for dehydrating the washed polyurethane resin is disposed on the cylinder dryer 50 side above the cleaning tank 30. In the cylinder dryer 50, four cylinders having heat sources inside are arranged in four stages. On the downstream side of the cylinder dryer 50, a take-up roller 42 that winds up the dried polyurethane resin (together with the film forming substrate 43) is disposed. The mangle rollers 18, 28, 38, the cylinder dryer 50 and the take-up roller 42 are connected to a rotation drive motor (not shown), and the film formation substrate 43 is made to be a substrate supply roller by these rotation drive forces. It is conveyed from 41 to the winding roller 42.

  When a non-woven fabric or a woven fabric is used as the film forming substrate 43, the film forming substrate 43 is pulled out from the substrate supply roller 41 and continuously introduced into the pretreatment liquid 15 through the guide rollers 11 and 12. . When the polyurethane resin solution 45 is applied by passing the film-forming substrate 43 between the pair of guide rollers 13 in the pretreatment liquid 15 and performing the pretreatment (sealing), the film-forming substrate 43 is brought into the film forming substrate 43. Of the polyurethane resin solution 45 is suppressed. After the film forming substrate 43 is pulled up from the pretreatment liquid 15, it is pressurized by the mangle roller 18 and the excess pretreatment liquid 15 is squeezed out. The pre-processed film-forming substrate 43 is conveyed in the direction of the coagulation tank 20. In the case where a flexible film made of PET or the like is used as the film forming substrate 43, pretreatment is not necessary, so that the film is directly fed from the guide roller 12 to the mangle roller 18 or in the pretreatment tank 10. The pretreatment liquid 15 may not be added. Hereinafter, in this example, the film forming substrate 43 is described as a PET film.

  As shown in FIG. 2, in the application process, the polyurethane resin solution 45 prepared in the preparation process is applied almost uniformly to the film forming substrate 43 by the knife coater 46 at room temperature. At this time, the application thickness (application amount) of the polyurethane resin solution 45 is adjusted by adjusting the gap (clearance) between the knife coater 46 and the upper surface of the film forming substrate 43.

  In the coagulation regeneration process, the film forming substrate 43 coated with the polyurethane resin solution 45 by the knife coater 46 is introduced into the coagulation liquid 25 from the guide roller 21 toward the guide roller 23. In the coagulating liquid 25, first, substitution of DMF of the polyurethane resin solution 45 and the coagulating liquid 25 proceeds on the surface of the applied polyurethane resin solution 45 to form dense micropores. The micropores are formed to a thickness of about several μm and constitute the surface layer 2a. Thereafter, the polyurethane resin is coagulated and regenerated on one side of the film forming substrate 43 by the progress of substitution of the DMF in the polyurethane resin solution 45 and the coagulating liquid 25 between the surface layer 2 a and the film forming substrate 43. Accompanying the replacement with the coagulating liquid 25 by DMF desolvation, the foam layer 7 and the communication holes that communicate the foam 7 in a three-dimensional mesh form are formed inside the surface layer 2a to constitute the foam layer 2b. Further, at the time of solvent removal, the porous 8 is formed by the cellulose derivative added to the polyurethane resin solution 45, and a communication hole that connects the porous 8 and the foam 7 is formed. Foam 7 is formed so that the film formation substrate 43 of the PET film does not allow water to permeate, so that desolvation occurs on the surface side (surface layer 2a side) of the polyurethane resin solution 45 and the film formation substrate 43 side is larger than the surface side. Is done.

  Here, the formation of the porous 8 will be described. In the polyurethane resin solution 45, it is considered that the cellulose derivative and the polyurethane resin are poorly compatible, so that the two phases are separated. In addition, when the polyurethane resin is coagulated and regenerated, the coagulation characteristics of the cellulose derivative and the polyurethane resin in the coagulation liquid 25 are different, so that there is a difference in shrinkage, and the compatibility between the cellulose derivative and the polyurethane resin is poor. Since the interfacial bonding force is reduced and a desorption phenomenon occurs, it is considered that the porous 8 is formed. For this reason, the pore diameter of the porous 8 is larger than the fine porosity of the surface layer 2a and smaller than the foam 7 of the foamed layer 2b, and the pore diameter of the communication hole connecting the porous 8 and the foam 7 is larger than the pore diameter of the microporous.

  The solidification regeneration of the polyurethane resin is completed while the film-forming substrate 43 coated with the polyurethane resin solution 45 enters the coagulating liquid 25 and reaches the guide roller 23. The coagulated and regenerated polyurethane resin is pulled up from the coagulating liquid 25, and after the excess coagulating liquid 25 is squeezed out by the mangle roller 28, the polyurethane resin is conveyed to the cleaning tank 30 via the guide roller 31 and introduced into the cleaning liquid 35.

  In the cleaning / drying step, the polyurethane resin introduced into the cleaning liquid 35 is passed through the guide roller 33 alternately up and down to clean the polyurethane resin. After the cleaning, the polyurethane resin is pulled up from the cleaning liquid 35 and the excess cleaning liquid 35 is squeezed out by the mangle roller 38. Thereafter, the polyurethane resin is dried by passing along the circumferential surface of the cylinder alternately between the four cylinders of the cylinder dryer 50 (in the direction of the arrow in FIG. 3). The dried polyurethane resin is wound around the winding roller 42 together with the film forming substrate 43.

  Next, production of the polyurethane sheet 3 will be described, but the description of the same steps, conditions, and film forming apparatus as those of the polyurethane sheet 2 described above will be omitted, and only different steps will be described.

  In the preparation step, an adjustment organic solvent for adjusting foaming is blended in the polyurethane resin solution. After mixing the polyurethane resin, DMF, water repellent additive, and pore-forming agent to dissolve the polyurethane resin, a predetermined amount of an adjusted organic solvent is added to delay the replacement of DMF with water during coagulation regeneration, and the resin emulsion 49 Get. As the adjustment organic solvent, one having a solubility in water smaller than that of DMF and capable of being uniformly mixed or dispersed in a solution in which the polyurethane resin is dissolved without solidifying (gelling) the polyurethane resin dissolved in DMF is used. Specific examples include ethyl acetate and isopropyl alcohol. By changing the addition amount of the adjustment organic solvent, the size and amount (number) of foams 9 formed inside the polyurethane sheet 3 can be controlled, and the compression rate of the polyurethane sheet 3 can be adjusted. In this example, in order to set the compressibility of the polyurethane sheet 3 in the above-described range, it is preferable that the amount of the adjusted organic solvent is in the range of 20 to 45 parts with respect to 100 parts of the resin emulsion 49.

  In the coagulation regeneration process, the film forming substrate 43 coated with the resin emulsion 49 is introduced into the coagulation liquid 25 to coagulate and regenerate the polyurethane resin. In the coagulation liquid 25, first, the surface layer 3a is formed on the surface of the resin emulsion 49 in the same manner as the polyurethane sheet 2. However, since the adjustment organic solvent is added to the resin emulsion 49, the DMF and the resin emulsion 49 The progress of substitution between the adjusted organic solvent and the coagulation liquid 25 is slowed. For this reason, the foam 9 having a pore diameter larger than the micropore formed in the surface layer 3a and smaller than the foam 7 formed in the foam layer 2b of the polyurethane sheet 2 is formed substantially uniformly inside the surface layer 3a.

  Here, formation of the foam 7 of the polyurethane sheet 2 and the foam 9 of the polyurethane sheet 3 will be described. DMF used for dissolving the polyurethane resin is a solvent generally used for dissolving the polyurethane resin, and can be mixed in an arbitrary ratio with respect to water. For this reason, in the production of the polyurethane sheet 2, when the polyurethane resin solution 45 is immersed in the coagulation liquid 25, first, substitution of DMF and coagulation liquid 25 (coagulation regeneration of the polyurethane resin) occurs on the surface of the polyurethane resin solution 45, and the surface layer 2a. Micropores are formed. Thereafter, since the coagulating liquid 25 enters the polyurethane resin solution 45 from the part where the surface layer 2a easily enters, a part where the substitution of the DMF and the coagulating liquid 25 proceeds rapidly and a part where the replacement is delayed are generated. 7 is formed. Since a PET film into which the coagulation liquid does not permeate is used for the film formation substrate 43, DMF is eluted only from the surface layer 2a side of the polyurethane resin solution 45. Therefore, the foam 7 is greatly rounded on the film formation substrate 43 side. It becomes a triangular pyramid shape.

  On the other hand, in the production of the polyurethane sheet 3, the adjusted organic solvent is added after the polyurethane resin is dissolved to obtain the resin emulsion 49. When the resin emulsion 49 is immersed in the coagulation liquid 25, the surface layer 3a is microporous on the surface of the resin emulsion 49 in the same manner as the surface layer 2a of the polyurethane sheet 2. Since the adjusted organic solvent has a solubility in water smaller than that of DMF, elution into water (coagulating liquid 25) is slower than in DMF. In addition, in the resin emulsion 49, the amount of DMF is reduced by adding the adjustment organic solvent. For this reason, since the replacement speed of the DMF and the adjustment organic solvent and the coagulation liquid 25 is slowed, the formation of the foam 7 such as the polyurethane sheet 2 is suppressed, and the foam 9 is distributed almost uniformly inside the surface layer 3a. Formed. Therefore, the pore diameter of the foam 9 is smaller than the foam 7 of the foam layer 2b of the polyurethane sheet 2 and larger than the micropore of the surface layer 3a. Further, since the foam 9 is formed along with the removal of DMF and the adjustment organic solvent, the foam 9 is communicated in a three-dimensional mesh shape with communication holes smaller than the pore diameter of the foam 9.

  In the buffing process, buffing is performed on the back side of the holding surface P of the polyurethane sheet 2 and the back side of the mounting surface Q of the polyurethane sheet 3. As shown in FIG. 4A, the polyurethane sheet 2 wound up by the winding roller 42 is formed on the film forming substrate 43. Since the thickness of the polyurethane sheet 2 varies during film formation, the holding surface P is uneven. After the film-forming substrate 43 is peeled off, as shown in FIG. 4B, the holding surface P is flattened by pressing the surface of the pressing roller 65 having a flat surface against the holding surface P. Concavities and convexities appear on the back N side. Unevenness appearing on the back N side is removed by buffing. In this example, since the continuously manufactured polyurethane sheet 2 has a band shape, the back surface N side is continuously buffed while pressing the pressing roller 65 against the holding surface P. As a result, as shown in FIG. 4C, the thickness variation of the polyurethane sheet 2 in which the back surface N side is buffed to form a flat back surface N ′ is eliminated. The polyurethane sheet 3 is similarly buffed. In FIG. 4C, the holding surface P and the back surface N ′ are shown flat for easy understanding. However, in the case of the polyurethane sheet 2 alone, the unevenness in which the thickness of the polyurethane sheet 2 is uniform on both surfaces. Presents. By attaching the back surfaces of the polyurethane sheets 2 and 3 together with the double-sided tape 6, the holding surface P and the mounting surface Q become substantially flat.

  As shown in FIG. 2, in the bonding step, the buffed surfaces of the polyurethane sheets 2 and 3, that is, the back surface of the holding surface P and the back surface of the mounting surface Q are bonded together. For the bonding of the polyurethane sheets 2 and 3, a double-sided tape 6 in which an adhesive 5 is applied to both sides of the base material 4 is used. After cutting into a desired shape and size such as a circle in the cutting process, an inspection is performed to confirm that there is no adhesion of dirt or foreign matter, and the holding pad 1 is completed.

(Action etc.)
Next, the operation and the like of the holding pad 1 of the present embodiment will be described.

  In the holding pad 1 of the present embodiment, since the pore diameter of the foam 9 formed substantially uniformly in the polyurethane sheet 3 is larger than the micropore of the surface layer 3a and smaller than the foam 7 of the polyurethane sheet 2, the compressibility of the polyurethane sheet 3 is It becomes smaller than the compressibility of the polyurethane sheet 2. In this example, the compression ratio of the polyurethane sheet 2 is set in a range of 30% to 70%, and the compression ratio of the polyurethane sheet 3 is set in a range of 1% to less than 30%. For this reason, the amount of deformation of the polyurethane sheet 3 with respect to the external force is smaller than that of the polyurethane sheet 2, in other words, the polyurethane sheet 2 is easily deformed with respect to the external force, and the polyurethane sheet 3 is not easily deformed. Thereby, even if an external force is applied when the object to be polished that comes into contact with the polyurethane sheet 2 is removed after polishing, deformation of the polyurethane sheet 3 is suppressed compared to the polyurethane sheet 2. Therefore, since the adhesiveness between the polyurethane sheet 3 and the holding surface plate is maintained, only the object to be polished can be easily removed without the holding pad 1 itself being detached from the holding surface plate. Efficiency can be improved.

  In addition, when a liquid such as a polishing liquid enters between the conventional holding pad and the object to be polished, the holding power of the object to be polished decreases, and the back surface of the object to be polished (the surface contacting the holding pad) is likely to be burned. There is a risk of damaging the workpiece. In the holding pad 1 of this embodiment, the contact angle of water with respect to the holding surface P and the mounting surface Q of the polyurethane sheets 2 and 3 is adjusted to 105 ° or more. For this reason, since the holding surface P and the mounting surface Q have water repellency, even if polishing liquid or the like enters between the holding pad 1 and the holding surface plate or the object to be polished during polishing, the holding surface plate rotates. It becomes easy to discharge | emit to the outer peripheral side of the holding pad 1 by the centrifugal force accompanying. Accordingly, since the adhesion between the holding pad 1 and the holding surface plate or the object to be polished is maintained, a decrease in the mounting force of the holding pad 1 to the holding surface plate and the holding force of the object to be polished is suppressed. be able to. Furthermore, it becomes difficult for the polishing liquid or the like to enter the holding pad 1 during the polishing process, and it is possible to suppress a reduction in the life of the holding pad.

  Furthermore, in the holding pad 1 of the present embodiment, the polyurethane sheet 2 has the foam layer 2b in which the foam 7 having a pore size larger than the microporous formed in the surface layer 2a is formed inside the surface layer 2a. Exhibits elasticity. For this reason, the object to be polished can be held in an elastic state while the polyurethane sheet 2 is deformed, and the flattened holding surface P is pressed almost evenly on the entire surface of the object to be polished. Thereby, since the pressing force applied to the processed surface of the object to be polished is equalized, the flatness of the object to be polished can be improved. Since it is expected that the objects to be polished will be increased in size and quality, the flatness of the objects to be polished is expected to be higher than ever. . Even in such a case, it can be expected that the required quality is satisfied by using the holding pad 1 of the present embodiment.

  Furthermore, in the holding pad 1 of this embodiment, the back surface of the holding surface P of the polyurethane sheet 2 and the back surface of the mounting surface Q of the polyurethane sheet 3 are bonded together. For this reason, since the surface layers 2a and 3a in which micropores are formed are located on both sides of the holding pad 1, the surface of the surface layer 3a, that is, the mounting surface Q is attached to the holding surface plate, That is, the holding surface P contacts the object to be polished. Since the surface layer 2a, 3a contains a small amount of water in the mounting to the holding surface plate or the contact of the object to be polished (holding on the holding surface plate), the surface tension of the water infiltrated into the micropores acts. It can be easily attached and abutted only with water. Therefore, even when air is bitten, misaligned, or the like when attached to the holding surface plate, it can be easily reattached, so that it can be attached flatly and easily without requiring skill in the attaching operation. Further, since the object to be polished is held by the action of the surface tension of water and the adhesive force of the polyurethane sheet 2, lateral displacement of the object to be polished can be suppressed without using a carrier (formwork) during polishing. .

  Further, in the holding pad 1 of the present embodiment, the holding surface P and the mounting surface Q are each formed with a porous 8 communicating with the foam 7 or the foam 9. For this reason, when the surface layers 2a and 3a are soaked with water and mounted on the holding surface plate, when the object to be polished comes into contact, the surface between the holding surface plate and the holding pad 1, and between the holding pad 1 and the object to be polished. Even if the air bites occur, the air is contained (sucked) in the foam 7 and the foam 9 through the perforations 8, so that the air between the holding surface plate and the holding pad 1 and between the holding pad 1 and the object to be polished is retained. Storage can be prevented. At this time, since the surface layers 2a and 3a contain water, air cannot enter the micropores of the surface layers 2a and 3a. However, since the pore diameter is larger than the micropores in the porous 8, the air enters. be able to. Therefore, since the object to be polished can be held substantially flat without air being stored, the object to be polished can be pressed substantially evenly during the polishing process, and the flatness of the processed surface of the object to be polished is improved. be able to.

  Further, in the holding pad 1 of the present embodiment, since the pore diameters of the foam 7 and the foam 9 are larger than the porous 8, the air entrained between the holding surface plate and the holding pad 1 and between the holding pad 1 and the object to be polished is ensured. Can be accommodated. Moreover, since the hole diameter of the communication hole which connects the porous 8 and the foam 7 or the foam 9 is larger than the microporous hole diameter of the surface layers 2a and 3a, the bitten air can be accommodated smoothly. Furthermore, since the foam 7 and the foam 9 are communicated in a three-dimensional mesh shape through the communication holes, the entire foam layers 2b and 3b can accommodate air even if the amount of air biting is large.

  Furthermore, in the conventional holding pad, since the double-sided tape is used for mounting on the holding surface plate, in order to peel off the holding pad once pasted from the holding surface plate, it is peeled with a force more than the adhesive force of the double-sided tape, Adhesive may remain on the holding surface plate during peeling (glue residue). If the adhesive remains, the remaining adhesive portion rises when a new holding pad is applied, so that the flatness of the surface (holding surface) of the holding pad is impaired. In order to avoid this, when replacing the holding pad or reattaching it due to its service life, etc., it is necessary to perform a cleaning operation to completely remove the adhesive remaining on the holding surface plate. Reduces workability of installation. On the other hand, since the holding pad 1 of this embodiment can be attached to the holding surface plate with only water, it can be easily peeled off and no adhesive remains. For this reason, since it can peel easily and cleaning of the holding surface plate when it peels can be simplified, the work efficiency of removal | desorption and mounting | wearing of the holding pad 1 can be improved without taking time and effort.

  Furthermore, in the holding pad 1 of the present embodiment, a double-sided tape 6 in which an adhesive 5 is applied to both surfaces of the base material 4 is used for bonding the polyurethane sheets 2 and 3. A PET film is used. For this reason, the polyurethane sheets 2 and 3 can be bonded to the double-sided tape 6 one by one, and the bonding operation can be easily performed. Moreover, since the foamed layer 2b in which the foam 7 of the polyurethane sheet 2 is formed has elasticity, the foamed layer of the polyurethane sheet 2 can be interposed through the base material 4 even if the surface of the holding surface plate has some distortion. The deformation of 2b can relieve the distortion of the holding surface plate. Furthermore, since the foam layer 2b has elasticity, it can be held in an elastic state without giving an impact to the object to be polished.

  Furthermore, in the back pad 1 of the present embodiment, the thickness of the polyurethane sheets 2 and 3 is uniform on the back surface of the holding surface P of the polyurethane sheet 2 and the back surface of the mounting surface Q of the polyurethane sheet 3. Buffed. For this reason, since the thickness of the polyurethane sheets 2 and 3 becomes substantially uniform without impairing the surface layer, the thickness of the entire holding pad 1 can be made substantially uniform. Accordingly, the holding surface P becomes substantially flat by mounting the holding pad 1 on a flat holding surface plate, so that the object to be polished can be held substantially flat. Accordingly, the flatness of the object to be polished can be improved by polishing.

  In the holding pad 1 of this embodiment, a polyurethane resin having a 100% modulus of 20 MPa or less is used for the polyurethane sheets 2 and 3. For this reason, since the surface of the polyurethane sheet 2 closely adheres to the shape of the object to be polished and the surface of the polyurethane sheet 3 adheres to the holding surface plate and exhibits adhesiveness, the object to be polished and held to the holding surface plate Can be reliably installed.

  In the conventional holding pad, a double-sided tape is used when the back side of one polyurethane sheet having a surface layer is mounted on a holding surface plate. For this reason, air may be caught between the holding pad and the holding surface plate. In this case, since the flatness of the object to be polished is impaired by the polishing process, it is necessary to reattach the holding pad. However, if the attachment fails and reapplying, the adhesive remains on the holding surface plate, and on the other hand, the holding pad is wrinkled and cannot be used. For this reason, it is difficult to mount the holding pad, and in particular, in the case of a large holding pad, considerable skill is required. Further, even when the replacement is performed due to the life, etc., the adhesive remains on the holding surface plate, so that a cleaning operation is required to peel off the remaining adhesive. For this reason, since the cleaning work is time-consuming, the efficiency of the work of attaching the holding pad to the holding surface plate is considerably reduced. There is also a technique to attach the holding pad to the holding surface plate without using double-sided tape, but when removing the object to be polished from the holding pad after polishing, the holding pad is held and fixed before the object to be polished is removed. It may come off from the board. In this case, it is necessary to attach a new holding pad to the holding surface plate, which may reduce the life of the holding pad and reduce the efficiency of the entire polishing process. The present embodiment is a holding pad that can solve these problems.

  In the holding pad 1 of the present embodiment, an example in which the compression rate of the polyurethane sheet 2 is in the range of 30% to 70% and the compression rate of the polyurethane sheet 3 is in the range of 1% to less than 30% is shown. The present invention is not limited to this, and the compression rate of the polyurethane sheet 3 on the side mounted on the holding surface plate may be made smaller than the compression rate of the polyurethane sheet 2 on the side in contact with the object to be polished. When the compression ratio of the polyurethane sheet 2 is smaller than 30%, the polyurethane sheet 2 becomes hard and may give an impact to the object to be polished during the polishing process. When the compression ratio exceeds 70%, There is a possibility that the polyurethane sheet 2 is deformed by a shearing force generated at the time of polishing and the flatness is impaired. For this reason, it is preferable to set the compression rate of the polyurethane sheet 2 in the range of 30% or more and 70% or less, and more preferably in the range of 40% or more and 70% or less. On the other hand, when the compressibility of the polyurethane sheet 3 is smaller than 1%, it becomes difficult to absorb and relax the strain with the polyurethane sheet 3 when there is some strain on the holding surface plate, and the compressibility is 30% or more. In this case, the polyurethane sheet 3 is also deformed by an external force applied when the object to be polished is removed from the holding pad 1, and the holding pad 1 may be detached from the holding surface plate. For this reason, it is preferable to set the compression rate of the polyurethane sheet 3 in the range of 1% or more and less than 30%, and more preferably in the range of 5% or more and less than 30%.

  Moreover, in the holding pad 1 of this embodiment, although the cellulose derivative was illustrated as a pore formation agent which forms the porous 8, this invention is not limited to this, It is soluble in the organic solvent used for melt | dissolution of a polyurethane resin It is sufficient if it is hardly soluble or insoluble in water used for the coagulation liquid. In addition to cellulose derivatives, such pore formers include, for example, polyacrylonitrile (PAN), polyvinyl chloride, polyvinyl acetate, vinylidene chloride / vinyl chloride copolymer, polycaprolactone (PCL), polystyrene (PS), poly A polymer compound such as methyl methacrylate (PMMA) can be used. Moreover, you may use it, mixing 2 or more types of these high molecular compounds and the cellulose derivative mentioned above. Moreover, the pore diameter of the porous 8 can be adjusted by changing the amount of the pore-forming agent added to the polyurethane resin solution 45 and the resin emulsion 49. In this embodiment, an example in which a water-repellent additive for imparting water repellency to the holding surface P and the mounting surface Q is added to the polyurethane resin solution 45 and the resin emulsion 49, respectively. For this purpose, the surfaces of the polyurethane sheets 2 and 3 may be treated with a water-repellent additive such as a fluororesin. If the imparted water repellency is too strong, it is difficult to include water in the surface layers 2a and 3a when the holding pad 1 is mounted on the holding surface plate or abutted against an object to be polished. It is preferable to adjust so that the contact angle of water with respect to water is 150 ° or less.

  Furthermore, in the holding pad 1 of the present embodiment, an example in which a polyurethane resin having a 100% modulus of 20 MPa or less is used for the polyurethane sheets 2 and 3 is shown, but the present invention is not limited to this. For example, a polyester resin or the like may be used. If the 100% modulus is 20 MPa or less, the wet-formed polyurethane sheets 2 and 3 are in close contact with the object to be polished and the holding surface plate. Thus, it is possible to improve the retention of the object to be polished. If a polyurethane resin is used, the surface layers 2a and 3a can be easily formed by a wet film forming method. Furthermore, in the holding pad 1 of the present embodiment, an example is shown in which a carrier that prevents lateral shift of the object to be polished is not used during polishing, but the use of the carrier can enhance prevention of lateral shift of the object to be polished. .

  Furthermore, in the holding pad 1 of the present embodiment, the double-sided tape 6 in which the adhesive 5 is applied to both surfaces of the base material 4 is illustrated for bonding the polyurethane sheets 2 and 3, but the present invention is limited to this. It is not something. For example, the base material 4 and the pressure-sensitive adhesive 5 may be separately prepared and bonded. Considering the simplicity of work and the ease of handling during mounting on a holding surface plate or during transportation, it is preferable to use a double-sided tape 6 having a substrate 4. Moreover, it is also possible to bond only with the adhesive 5 without using the base material 4, and further, without using the adhesive 5 by bonding the surfaces of the polyurethane sheets 2 and 3 while heating. You may bond together by the adhesiveness of resin itself. It is possible to bond together while ensuring flatness by temperature control during heating. If it does in this way, the part for the cost of the base material 4 or the adhesive 5 can be reduced. In the present embodiment, a PET film is exemplified as the base material 4, but the present invention is not limited to this, and a flexible film other than PET, a nonwoven fabric, a woven fabric, or the like may be used. Good. Furthermore, examples of the pressure-sensitive adhesive 5 that can be used other than the present embodiment include an acrylic pressure-sensitive adhesive.

  Furthermore, in the holding pad 1 of the present embodiment, the wet-formed polyurethane sheets 2 and 3 are continuously formed on the back surface N side while the pressure roller 65 is pressed against the holding surface P and the mounting surface Q in the buffing process. However, the present invention is not limited to this. For example, after the polyurethane sheet before buffing is cut to a desired size, a flat plate having a flat surface may be pressed against the holding surface P and the mounting surface Q and the back N side may be buffed by a buffing machine or the like. . The buffing amount is preferably buffed to a thickness of twice or more the thickness range R of the polyurethane sheets 2 and 3. Various materials such as sandpaper and diamond buffol are used in the buffing, but any can be used as long as uniform processing (grinding removal) is possible. At this time, the higher the buff count (number indicating the roughness of the abrasive grains), the more fine the abrasive grains can be ground and the uniform buffing process can be performed. Furthermore, the thickness accuracy is improved by buffing with a low buff count (rough abrasive grains) at the first time, and buffing with a buff count higher than the first time with a lower buff count. It can also be raised. Further, for example, if the thickness accuracy of the polyurethane sheets 2 and 3 is improved by increasing the adjustment accuracy of the coating thickness of the polyurethane resin solution 45 and the resin emulsion 49 at the time of film formation, the polyurethane sheets 2 and 3 are buffed. It is also possible to paste them as they are.

  Moreover, in this embodiment, although the example which uses the film made from PET for the film-forming base material 43 at the time of wet film-forming was shown, this invention is not limited to this, For example, a nonwoven fabric and a woven fabric are used. May be. In this case, since it is difficult to peel off the film forming substrate 43 after the polyurethane resin is solidified and regenerated, the surface of the film forming substrate 43 opposite to the surface on which the polyurethane resin has been regenerated is buffed and buffed. What is necessary is just to stick together.

  Hereinafter, examples of the holding pad 1 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, polyester MDI (diphenylmethane diisocyanate) polyurethane resin (100% modulus 10 MPa) was used as the polyurethane resin for the production of the polyurethane sheets 2 and 3. In the preparation of the polyurethane sheet 2, 45 parts of DMF as a solvent, 40 parts of a DMF dispersion containing 30% of carbon black as a pigment, and 0 parts of cellulose acetate butyrate as a cellulose derivative with respect to 100 parts of a 30% polyurethane resin solution. 0.3 part of silicone oil for imparting water repellency was added and mixed to prepare a polyurethane resin solution 45. On the other hand, the production of the polyurethane sheet 3 was the same as that of the polyurethane sheet 2 except that 45 parts of ethyl acetate as an adjustment organic solvent was added. Each of the polyurethane sheets 2 and 3 was buffed, and the polyurethane 2 and the polyurethane sheet 3 were bonded together with a double-sided tape 6 to produce the holding pad 1 of Example 1. The holding pad 1 was mounted on the holding surface plate with the surface layer 3a of the polyurethane sheet 3, and the surface layer 2a side of the polyurethane sheet 2 was brought into contact with the object to be polished to hold the object to be polished on the holding surface plate.

(Comparative Example 1)
In Comparative Example 1, a polyurethane sheet 2 ′ was prepared in the same manner as in Example 1 except that no water-repellent additive was blended, and the obtained polyurethane sheet 2 ′ was bonded together to produce the holding pad of Comparative Example 1. did. The attachment to the holding surface plate and the contact of the object to be polished are both performed on the surface layer of the polyurethane sheet 2 ′.

(Comparative Example 2)
In Comparative Example 2, polyurethane sheets 2 ′ and 3 ′ were produced in the same manner as in Example 1 except that no water-repellent additive was blended, and a holding pad in Comparative Example 2 was produced in the same manner as in Example 1. For the mounting direction to the holding surface plate, the polyurethane sheet 2 ′ was on the side to be polished.

(Evaluation)
Next, for each of the examples and comparative examples, the compressibility of the polyurethane sheets 2 and 3 and the contact angle of water were measured. The compression rate was measured according to Japanese Industrial Standard (JIS L 1021-1974 compression rate and compression modulus A method). The contact angle of water was determined by using a contact angle meter / solid-liquid interface analyzer (DropMaster500: manufactured by Kyowa Interface Science Co., Ltd.) and taking a value 5 minutes after the start of measurement. Moreover, the polishing test of the glass substrate was done on the following polishing conditions using the holding pad 1. At this time, visually, the presence or absence of slurry (polishing liquid) infiltrated from the outer edge of the glass substrate into the back side of the glass substrate (between the holding pad 1 and the glass substrate), and the holding pad when replacing the glass substrate The situation of peeling was evaluated. The evaluation and measurement results are shown in Table 1 below.
(Polishing conditions)
Used polishing machine: Oscar polishing machine (SP-1200, manufactured by Speed Fam Co.)
Polishing speed (rotation speed): 61 rpm
Processing pressure: 76 gf / cm ²
Slurry: Cerium slurry Polishing object: LCD glass substrate (355 mm x 406 mm x 0.5 mm)
Polishing time: 30 min x 20 times

  As shown in Table 1, in the holding pad 1 of Example 1, the polyurethane sheet 2 has a compressibility of 40.4%, a water contact angle of 106.8 °, the polyurethane sheet 3 has a compressibility of 11.3%, and water contact A measurement result with an angle of 105.9 ° was obtained, the contact angle of water was large, and no entry of slurry was observed in the polishing test. For this reason, water repellency is sufficiently imparted, and since the infiltration of the slurry into the back side of the glass substrate is suppressed, a decrease in holding power is not recognized, and there is a possibility that damage such as burns on the glass substrate may occur. I found that there was no. In addition, since the porous sheets 2 and 3 are formed with the porous 8, no air was stored between the holding pad and the holding surface plate or the glass substrate. Further, even when the glass substrate was replaced, peeling of the holding pad 1 was not recognized, and the holding pad 1 could be maintained in a state of being mounted on the holding surface plate. Therefore, by setting the smaller one of the two polyurethane sheets 2 and 3 as the holding surface plate side, the holding pad is easily removed without removing the object to be polished such as the glass substrate after polishing. It can be removed, and the work to be polished can be easily replaced.

  On the other hand, in Comparative Example 1, a measurement result with a compression ratio of 41.2% and a water contact angle of 98.3 ° was obtained for the polyurethane sheet 2 '. Since the polyurethane 2 'is bonded to each other, the compression rate is substantially the same as that of Example 1 using the polyurethane sheet 2 on the side in contact with the object to be polished. On the side, it becomes larger than Example 1 using the polyurethane sheet 3. Moreover, since the water repellent additive was not mix | blended, it turned out that the contact angle of water becomes smaller than Example 1, and water repellency is not provided. In the polishing test using the holding pad of Comparative Example 1, when the glass substrate was replaced, it was often recognized that the holding pad itself was detached from the holding surface plate. This is presumably because the polyurethane sheet 2 ′ was deformed by an external force when the glass substrate was removed because the polyurethane sheet 2 ′ was attached to the holding surface plate. Moreover, the infiltration of the slurry was also observed, and it was found that there is a possibility that the back surface of the glass substrate may be burned. This is presumably because the water repellency is weaker than that of Example 1 and the slurry easily enters the back side of the glass substrate.

  On the other hand, in Comparative Example 2, the same polyurethane sheet 2 ′ as in Comparative Example 1 was used on the side in contact with the object to be polished. The polyurethane sheet 3 'was measured with a compression ratio of 12.4% and a water contact angle of 95.3 °. From this, it was found that the compression rate was almost the same as in Example 1, but since the water repellent additive was not blended, the contact angle of water was smaller than that in Example 1 and water repellency was not imparted. . Further, since the porous sheets 2 ′ and 3 ′ are formed with the perforations 8, as in Example 1, no air retention was observed between the holding pad and the holding surface plate or the glass substrate. In the polishing test using the holding pad of Comparative Example 2, although the peeling of the holding pad was not observed when the glass substrate was replaced, the infiltration of the slurry was recognized as in Comparative Example 1.

  The present invention provides a holding pad that can be easily attached to and detached from a surface plate and can improve the efficiency of exchanging an object to be polished, and thus contributes to the manufacture and sale of the holding pad. Have.

It is sectional drawing which shows the holding pad of embodiment to which this invention is applied. It is process drawing which shows the manufacturing process of a holding pad. It is a front view which shows schematic structure of the film-forming apparatus used for manufacture of the polyurethane sheet of a holding pad. It is sectional drawing which shows the change of the polyurethane sheet in a buff processing process, (A) is a polyurethane sheet formed in the film-forming base material, (B) is a polyurethane sheet when a holding surface is press-contacted to a pressure contact roller, (C ) Shows the polyurethane sheet after buffing.

Explanation of symbols

P Holding surface Q Mounting surface 1 Holding pad 2, 3 Polyurethane sheet (soft plastic sheet)
2a, 3a surface layer 2b, 3b foam layer

Claims (8)

  The back surfaces of two soft plastic sheets having a surface layer formed with micropores are bonded to each other, attached to a surface plate on one surface layer side, and the other surface layer side abuts the object to be polished. In the holding pad, each of the soft plastic sheets has a different compression rate, and the holding pad is attached to the surface plate on the surface layer side of the soft plastic sheet having the smaller compression rate.   Each of the two soft plastic sheets has a foam layer in which foam having a pore size larger than the micropore formed in the surface layer is formed inside the surface layer, and is attached to the surface plate. 2. The holding pad according to claim 1, wherein the foam formed in the foamed layer of the soft plastic sheet has a smaller pore diameter than the foam formed in the foamed layer of the soft plastic sheet in contact with the object to be polished.   The soft plastic sheet in contact with the object to be polished has a compression rate of 30% or more and 70% or less, and the soft plastic sheet mounted on the surface plate has a compression rate of 1% or more and less than 30%. The holding pad according to claim 2.   2. The holding pad according to claim 1, wherein a contact angle of water with respect to the surface of the surface layer is 105 ° or more in each of the soft plastic sheets.   The holding pad according to claim 1, wherein the back surfaces of the soft plastic sheets are bonded to each other with an adhesive member having a base material and a pressure-sensitive adhesive disposed on both surfaces of the base material.   2. The holding pad according to claim 1, wherein the back side of the soft plastic sheet is buffed so that the thickness of each soft plastic sheet is uniform.   Each of the soft plastic sheets is further formed with a pore having a pore size smaller than the foam formed in the foam layer and larger than the micropore formed in the surface layer on the surface layer. The holding pad according to any one of claims 1 to 6, wherein the holding pad communicates with the foam formed in the foam layer.   The holding pad according to any one of claims 1 to 7, further comprising a carrier that prevents lateral shift of an object to be polished during polishing.

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