JP4034320B2 - Holding pad - Google Patents

Description

  The present invention relates to a holding pad, and more particularly to a holding pad in which one surface side is mounted on a surface plate and the other surface side is in contact with an object to be polished.

  Conventionally, materials such as flat panel display (FPD) glass substrates, color filters, indium tin oxide (ITO) film-formed substrates (polished objects) 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. By interposing the holding pad between the object to be polished and the holding surface plate, scratches and the like can be avoided. 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 solidification regeneration, micropores constituting the surface layer are densely formed on the surface of the soft plastic sheet with 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 an object to be polished, the surface opposite the surface layer of the holding pad is attached to the holding surface plate, and the surface layer contains liquid such as water and presses the object to be polished to enter 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 entered 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.

JP 2002-355755 A JP-A-8-267668

  However, in the technique of Patent Document 2, since the holding pad is mounted on the holding surface plate with the double-sided tape, air may be bitten 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 polishing as in the case where 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.

  An object of the present invention is to provide a holding pad that can be easily mounted on a surface plate and can improve the mounting workability.

To solve the above problems, the present invention is mounted one side is the surface plate, the holding pads other side abuts against the workpiece, the holding pads, two flexible plastic sheet back to each other by bonding the cage, at least one of the flexible plastic sheet of two said it has a surface layer formed of a microporous, the surface layer side surface tension of interposed water between the surface layer and the surface plate It is mounted on the surface plate.

In the holding pad of the present invention, since at least one of two flexible plastic sheet bonded has a surface layer, penetrates into the microporous surface layer Rukoto is interposed water between the surface layer and the surface plate since acting surface tension of the water, can be mounted easily platen with only water, it is possible to improve the workability of the attachment to the surface plate. Further, when replacing the holding pad, the adhesive does not remain on the surface plate as compared with the case where a conventional double-sided tape is used, so that it does not take time to remount.

In this case, if the two soft plastic sheets each have a surface layer on which micropores are formed, the surface layer is located on both sides of the holding pad, so that one surface layer side is the surface layer. The surface tension of water infiltrated into the micropore when the surface plate is attached to the surface plate with the surface tension of water interposed between the surface plate and the surface plate, and the other surface layer side is brought into contact with the object to be polished through water . Therefore, the mounting to the surface plate and the contact of the object to be polished can be easily performed. Moreover, it is preferable that the back surfaces of a soft plastic sheet are bonded together by the adhesive member which has a base material and the adhesive arrange | positioned on both surfaces of this base material. Furthermore, if the soft plastic sheets are the same, parts management becomes easy and cost reduction can be achieved. Further, if the back side of the soft plastic sheet is buffed so that the thickness of each soft plastic sheet is uniform, the thickness of the soft plastic sheet can be extended without damaging the surface layer, and the thickness of the entire holding pad can be reduced. The thickness can be made substantially uniform, and the object to be polished can be held flat. Furthermore, if the soft plastic sheet has a foam layer in which foam having a pore size larger than the microporous formed in the surface layer is formed inside the surface layer, the foam layer has elasticity. It can be held in an elastic state. In addition, the surface of the surface layer of the soft plastic sheet is further formed with a pore having a pore size larger than the micropore formed in the surface layer and smaller than the foam formed in the foam layer, and the pore is formed in the foam layer. If it communicates with the foamed air, it will be sucked into the foam of the foamed layer through the perforation even if air is caught when it is attached to the surface plate or when it comes into contact with the workpiece. Is eliminated and the object to be polished can be held flat. Such a holding pad may further include a carrier for preventing lateral displacement of the object to be polished during polishing.

According to the invention, at least one two flexible plastic sheet bonded because having a surface layer, and enters the microporous surface layer Rukoto interposed water between the surface layer and the surface plate since the surface tension of water acts, can be mounted easily platen with only water, it is possible to improve the workability of the attachment to the surface plate, the effect can be obtained as.

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

(Back pad)
As shown in FIG. 1, a holding pad (generally called a back pad, hereinafter referred to as a back pad) 1 has two homogeneous polyurethane sheets (soft plastic sheets) 2 formed of polyurethane resin. is doing. Each of the two polyurethane sheets 2 has a skin layer (surface layer) 2a and a nap layer (foamed layer) 2b inside the skin layer 2a (inside each polyurethane sheet 2). In the two polyurethane sheets 2, the back surfaces on the opposite sides of the skin layer 2 a are bonded to each other via a double-sided tape 3 (adhesive member). The double-sided tape 3 has an adhesive 5 coated on both sides of a base material 4 made of polyethylene terephthalate (hereinafter abbreviated as PET). The back pad 1 has skin layers 2a on both sides, one of which is a holding surface P that comes into contact with an object to be polished, and the other is a mounting surface Q that is mounted on a pressure (holding) surface plate of a polishing machine. The back side of the holding surface P and the back side of the mounting surface Q are buffed so that the thickness of each polyurethane sheet 2 (length in the vertical direction in FIG. 1) is uniform (details will be described later). For this reason, both surfaces of the holding pad 1, that is, the holding surface P and the mounting surface Q are substantially flat.

  In the skin layer 2a of the polyurethane sheet 2, dense micropores (not shown) are formed. In the nap 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 so that the holding surface P and the mounting surface Q side are smaller than the holding surface P and the back surface side of the mounting surface Q, respectively. In the polyurethane resin between the foams 7, foam (not shown) having a pore diameter larger than that of the micropore formed in the skin layer 2 a and smaller than that of the foam 7 formed in the nap 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 holding surface P and the mounting surface Q (surface of the skin layer 2a) of the polyurethane sheet 2, a porous 8 communicating with the foam 7 formed on the nap layer 2b is further formed. The pore diameter of the pore 8 is larger than the micropore formed in the skin layer 2a and smaller than the foam 7 formed in the nap layer 2b. The hole diameter of the communication hole that communicates the pore 8 and the foam 7 is formed larger than the diameter of the microporous hole of the skin layer 2a. The pores 8 are formed by a pore forming agent added to the polyurethane resin solution when the polyurethane sheet 2 described later is formed.

(Manufacture of back pads)
The back pad 1 is manufactured through each process shown in FIG. First, in the preparation step, polyurethane resin, N, N-dimethylformamide (hereinafter abbreviated as DMF), a water-miscible organic solvent capable of dissolving polyurethane resin, an additive and a pore-forming agent are mixed to form polyurethane resin. Dissolve. For the polyurethane resin, a polyester resin, a polyether resin, a polycarbonate resin or the like having a 100% modulus (tension when pulled twice) of 20 MPa or less is used. For example, the polyurethane resin is 30%. Dissolve in DMF. As the additive, a pigment such as carbon black for controlling the size and amount (number) of foam 7, a hydrophilic activator for promoting foaming, a hydrophobic activator for stabilizing solidification regeneration of polyurethane resin, and the like are used. it can.

  As the pore-forming agent, a predetermined amount of a cellulose derivative that is soluble in DMF for dissolving 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 this cellulose derivative is set according to the pore diameter of the porous 8 on the surface of the skin layer 2a. The obtained solution is filtered to remove aggregates and the like, and then defoamed under vacuum to obtain a polyurethane resin solution.

  In the coating process, coagulation regeneration process, and washing / drying process, the polyurethane resin solution obtained in the preparation process is continuously applied to the film-forming substrate and immersed in an aqueous coagulation liquid to coagulate and regenerate the polyurethane resin, followed by washing. After drying, a polyurethane sheet is obtained. 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 skin layer 2a. Thereafter, the polyurethane resin is coagulated and regenerated on one surface 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 skin layer 2 a and the film forming substrate 43. Along with the replacement of the coagulating liquid 25 by the removal of DMF, the foam layer 7 and communication holes that connect the foam layer 7 in a three-dimensional network shape are formed inside the skin layer 2a to constitute the nap layer 2b. Since the thickness of the skin layer 2a is about several μm, the nap layer 2b is formed in the majority of the coating thickness of the polyurethane resin solution 45. Therefore, the thickness of the nap layer 2b is larger than the thickness of the skin layer 2a. Become. 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 does not allow water to permeate the film-forming substrate 43 of the PET film, so that desolvation occurs on the surface side (skin layer 2a side) of the polyurethane resin solution 45 and the film-forming substrate 43 side is formed 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 8 is larger than the micropore of the skin layer 2a and smaller than the foam 7 of the nap layer 2b, and the pore diameter of the communication hole connecting the pore 8 and the foam 7 is larger than the pore diameter of the micropore.

  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.

  In the back surface buffing process, buffing is performed on the back surface (back surface) side of the holding surface P (mounting surface Q) of the polyurethane sheet after drying. As shown in FIG. 4A, the polyurethane sheet 2 wound up by the winding roller 42 is formed on a PET film of 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 becomes flat by holding the surface of the pressing roller 65 with the flat surface against the holding surface P, thereby holding the holding surface P flat. Unevenness appears on the back N side of the surface P. 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. In FIG. 4C, the holding surface P and the back surface N ′ are shown flat for easy understanding. However, in the single sheet of the polyurethane sheet 2, the thickness of the polyurethane sheet 2 is uniform on both surfaces. The holding surface P and the mounting surface Q are flattened by bonding the back surfaces N ′ of the two polyurethane sheets 2 together with the double-sided tape 3.

  As shown in FIG. 2, in the bonding step, the back surface of the holding surface P and the back surface of the mounting surface Q of the two buffed polyurethane sheets 2 are bonded together. For the bonding of the polyurethane sheet 2, a double-sided tape 3 in which a pressure-sensitive adhesive 5 is applied to both sides of the base material 4 is used. At this time, after one polyurethane sheet 2 is bonded to one side of the double-sided tape 3, another polyurethane sheet 2 is bonded to the other side of the double-sided tape 3. A flexible film such as PET can be used for the substrate 4, and examples of the usable pressure-sensitive adhesive 5 include an acrylic pressure-sensitive adhesive. After cutting into a desired shape and size such as a circle in the cutting process, the back pad 1 is completed by performing inspections such as confirming that there is no adhesion of dirt or foreign matter.

  When polishing an object to be polished, the back pad 1 is mounted on the mounting surface Q side of a pressure surface plate of a single-side polishing machine, and the object to be polished is brought into contact with and held on the holding surface P. As shown in FIG. 5, the single-side polishing machine 70 includes a polishing surface plate 71 that can rotate downward, and a pressure surface plate 72 that presses an object 78 to be polished. The upper surface of the polishing surface plate 71 and the lower surface of the pressure surface plate 72 are both formed flat. A polishing cloth 75 for polishing the workpiece 78 is affixed to the upper surface of the polishing surface plate 71, and the back pad 1 is attached to the lower surface of the pressure surface plate 72. When the back pad 1 is mounted on the pressure platen 72, an appropriate amount of water is included in the mounting surface Q of the back pad 1 and pressed against the pressure platen 72. The surface tension of the water that has entered the micropores of the skin layer 2a on the attachment surface Q side acts between the back pad 1 and the pressure surface plate 72, and the back pad 1 is pressurized by the adhesiveness of the polyurethane resin of the polyurethane sheet 2. Mounted on the surface plate 72. When holding the object to be polished 78, the object to be polished 78 is pressed by adding an appropriate amount of water to the holding surface P of the back pad 1. Since the surface tension of the water that has entered the micropores of the skin layer 2a on the holding surface P side acts between the back pad 1 and the object to be polished 78, the object to be polished 78 is held. During polishing, a polishing liquid containing abrasive particles is supplied between the object to be polished 78 and the polishing cloth 75, and the polishing surface plate 71 is rotated while applying pressure to the object to be polished 78 by the pressure surface plate 72. The lower surface (processed surface) of the workpiece 78 is polished.

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

  In the back pad 1 of this embodiment, the back surfaces opposite to the skin layers 2a of the two polyurethane sheets 2 are bonded together. For this reason, since the skin layer 2a in which micropores are formed is located on both sides, the surface of one skin layer 2a, that is, the holding surface P is in contact with the object to be polished 78, and the surface of the other skin layer 2a, that is, The mounting surface Q side is mounted on the pressure platen 72. When holding the object to be polished 78 and mounting it on the pressure platen 72, the surface tension of the water that has entered microporously acts by adding a small amount of water to the skin layer 2a. Can be easily performed. Therefore, even when air is bitten, misaligned, or the like when attached to the pressurizing surface plate 72, it can be easily pasted, so that it can be attached flatly and easily without requiring skill in the attaching operation. Further, since the object to be polished 78 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 78 can be suppressed without using a carrier (formwork) during polishing. Can do.

  Also, with conventional back pads, double-sided tape is used for mounting on a pressure platen, so in order to peel off the backpad once applied from the pressure platen, it peels with a force greater than the adhesive strength of the double-sided tape. In some cases, the adhesive may remain (glue residue) on the pressure platen during peeling. If the adhesive remains, the remaining adhesive portion rises when a new back pad is applied, and the flatness of the surface (holding surface) of the back pad is impaired. In order to avoid this, when replacing the back 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 pressure platen. This reduces the workability of wearing. On the other hand, since the back pad 1 of the present embodiment can be attached to the pressure platen only with water, it can be easily peeled off and no adhesive remains. For this reason, since it can peel easily and cleaning of the pressurization surface plate 72 at the time of peeling can be simplified, the workability | operativity of the removal | desorption and mounting | wearing of the back pad 1 can be improved without taking time.

  Further, in the back pad 1 of the present embodiment, a double-sided tape 3 in which an adhesive 5 is applied to both surfaces of a base material 4 is used for bonding two polyurethane sheets 2. A PET film is used. For this reason, the polyurethane sheet 2 can be bonded to the double-sided tape one by one, and the bonding operation can be easily performed. Further, even if the surface of the pressure platen 72 has a slight distortion, the nap layer 2b on which the foam 7 is formed has elasticity, so that the polyurethane sheet on the pressure platen 72 side through the base 4 2 is pressed against the pressure platen 72, so that the nap layer 2b is deformed, and the distortion of the pressure platen 72 can be reduced. Further, since the nap layer 2b has elasticity, it can be held in an elastic state without giving an impact to the object to be polished 78.

  Furthermore, in the back pad 1 of the present embodiment, the back surface of the holding surface P of the polyurethane sheet 2 and the back surface of the mounting surface Q are buffed so that the thickness of each polyurethane sheet 2 is uniform. . For this reason, since the thickness of each polyurethane sheet 2 becomes substantially uniform, the thickness of the entire back pad 1 becomes substantially uniform. As a result, the holding surface P becomes substantially flat when mounted on the flat pressure platen 72, so that the workpiece 78 can be held flat. Therefore, the flatness of the workpiece 78 can be improved by polishing.

  Furthermore, in the back pad 1 of this embodiment, a polyurethane resin having a 100% modulus of 20 MPa or less is used for the polyurethane sheet 2. For this reason, since the surface of the polyurethane sheet 2 closely adheres to the shape of the object to be polished and exhibits adhesiveness, the object 78 can be held and attached to the pressure platen 72 with certainty. . In the back pad 1 of the present embodiment, two homogeneous polyurethane sheets 2 are used. For this reason, the polyurethane sheet 2 formed into a film on the same conditions can be used, and parts management can be made easy. Thereby, the manufacturing cost of the back pad 1 can be reduced.

  Further, in the back 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 of the nap layer 2b. For this reason, when the skin layer 2a is soaked with water and attached to the single-side polishing machine 70, the elastic polyurethane sheet 2 is deformed and the foam 7 of the nap layer 2b is deformed when the object 78 is brought into contact. . Thus, even if air is caught between the pressurizing surface plate 72 and the holding pad 1 and between the holding pad 1 and the workpiece 78, air is accommodated in the foam 7 through the porous 8 communicating with the foam 7 ( Therefore, it is possible to prevent air from being stored between the pressurizing platen 72 and the holding pad 1 and between the holding pad 1 and the workpiece 78. At this time, since water is contained in the skin layer 2a, air cannot enter into the micropores of the skin layer 2a, but air can enter into the pores 8 because the pore diameter is larger than the micropores. Therefore, since the workpiece 78 can be held substantially flat without storing air, the workpiece 78 can be pressed substantially evenly during the polishing process, and the processed surface of the workpiece 78 becomes the polishing cloth. Since the surface is polished approximately evenly at 75, the flatness of the processed surface can be improved.

  Further, in the back pad 1 of the present embodiment, since the pore diameter of the foam 7 formed in the nap layer 2b is larger than the porous 8, the air bitten between the skin layer 2a and the object to be polished 78 can be surely accommodated. Can do. Moreover, since the hole diameter of the communication hole which connects the porous 8 and the foam 7 is larger than the microporous hole diameter of the skin layer 2a, the bitten air can be accommodated smoothly. Furthermore, since the foam 7 is communicated in a three-dimensional network through the communication holes, the entire foam 7 formed in the nap layer 2b can be accommodated even if the air biting amount is large.

  In conventional backpads, double-sided tape is used when attaching the back side of one polyurethane sheet with a skin layer to the pressure platen. The agent remains, and on the other hand, the holding pad is wrinkled and cannot be used. For this reason, it is difficult to attach the back pad, and particularly in the case of a large back pad, considerable skill is required. Further, even when the replacement is performed due to the service life or the like, the adhesive remains on the pressure platen, so that a cleaning operation for peeling off the remaining adhesive is required. For this reason, since the cleaning work takes time, the workability of attaching the back pad to the pressure surface plate is considerably lowered. The present embodiment is a back pad that can solve these problems.

  In addition, in the back pad 1 of this embodiment, although the same thing which made 100% modulus of the polyurethane resin 20 MPa or less was illustrated in the two polyurethane sheets 2, this invention is not limited to this. For example, two different resin sheets may be bonded to each other according to the characteristics of the pressure platen 72 on which the back pad 1 is mounted or the workpiece 78 to be held, and the thickness may be different. Examples of the resin that can be used include a polyester resin. If the 100% modulus is 20 MPa or less, the wet-formed resin sheet closely adheres to the shape of the object to be polished. It is possible to improve the retention of objects. If a polyurethane resin is used, the skin layer 2a can be easily formed by a wet film forming method. Furthermore, in the back pad 1 of the present embodiment, the example in which the skin layer 2a is provided on the holding surface P side and the mounting surface Q side is shown, but the present invention is not limited to this, and at least the mounting surface Q side. Need only have the skin layer 2a. In this case, the holding surface P side may be subjected to buffing or the like to improve flatness, for example. Moreover, in the back pad 1 of this embodiment, the example which does not use the carrier which prevents the lateral deviation of a to-be-polished object at the time of a grinding | polishing process was shown, However, By using a carrier, the prevention of the lateral deviation of an to-be-polished object can be strengthened. .

  Moreover, in the back pad 1 of this embodiment, although the double-sided tape 3 which apply | coated the adhesive 5 to both surfaces of the base material 4 was illustrated for bonding of the two polyurethane sheets 2, this 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 convenience of work, it is preferable to use the double-sided tape 3. Moreover, it is also possible to bond only with the adhesive 5 without using the base material 4, and furthermore, the resin itself without using the adhesive 5 by bonding the surfaces to be bonded of the polyurethane sheet 2 while heating. You may stick together by the adhesiveness of. 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. Moreover, in this embodiment, although the film made from PET was illustrated for the base material 4, this invention is not limited to this, You may use a nonwoven fabric, a woven fabric, etc.

  Furthermore, in the back pad 1 of the present embodiment, an example in which the back surface N side is continuously buffed while the pressure roller 65 is pressed against the holding surface P and the mounting surface Q in the back surface buffing process is shown. It is not limited to this. For example, after the polyurethane sheet before buffing is cut into a desired size, a flat plate having a flat surface may be pressed against the holding surface P and the mounting surface Q to buff the back surface N side.

  Furthermore, in the back pad 1 of the present embodiment, the cellulose derivative is exemplified as the pore-forming agent for forming the pores 8, but the present invention is not limited to this, and the organic solvent used for dissolving the polyurethane resin is used. What is necessary is just to be soluble and 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 cellulose derivative added to the polyurethane resin solution 45.

  Furthermore, in the present embodiment, an example in which a PET film is used for the film forming substrate 43 is shown, but the present invention is not limited to this, and for example, a nonwoven fabric or a woven fabric may be used. . 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.

  In the present embodiment, the knife coater 46 is exemplified for the application of the polyurethane resin solution 45. However, for example, a reverse coater, a roll coater, or the like may be used. There is no particular limitation. Moreover, in this embodiment, although the cylinder dryer 50 was illustrated for drying of a polyurethane resin, this invention is not limited to this, For example, you may use a hot air dryer etc.

  Further, in this embodiment, the wet-formed polyurethane sheet 2 is buffed on the back surface of the holding surface P and the mounting surface Q with a buffing machine or the like, but the buffing amount is in the range R of the thickness of the polyurethane sheet 2. It is desirable to buff the thickness twice or more. 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 sheet 2 is improved by increasing the adjustment accuracy of the coating thickness of the polyurethane resin solution 45 at the time of film formation, the two polyurethane sheets 2 are bonded together without buffing. It is also possible.

  Hereinafter, examples of the back pad 1 manufactured according to the present embodiment will be described. In addition, it describes together about the back pad of the comparative example manufactured for the comparison.

Example 1
In Example 1, a polyester MDI (diphenylmethane diisocyanate) polyurethane resin having a 100% modulus of 10 MPa was used as the polyurethane resin. 0.2 parts of cellulose acetate butyrate as a cellulose derivative was added to 100 parts of a DMF solution containing 30% polyurethane resin. Further, 50 parts of DMF for viscosity adjustment and 20 parts of a DMF dispersion containing 30% of pigment carbon black were mixed to prepare a polyurethane resin solution 45. At this time, since cellulose acetate butyrate is a solid (solid), it was previously dissolved in a small amount of DMF for viscosity adjustment and added in order to mix uniformly. When applying the polyurethane resin solution 45, the clearance of the coating device was set to 1 mm. In order to enhance the washing effect in the washing step, washing after coagulation regeneration was performed with warm water. The thickness variation of the obtained polyurethane sheet 2 had a standard deviation σ of 0.013 mm. In the back surface buffing process, sandpaper of buff count # 180 was used and the buffing amount was 0.25 mm. The back pad 1 of Example 1 was manufactured by bonding the two polyurethane sheets 2 with the double-sided tape 3. In this back pad 1, two polyurethane sheets 2 formed under the same conditions are bonded together. Strictly speaking, the formation position and size of the fine pores of the skin layer 2a, the foam 7 of the nap layer 2b, etc. Because they are slightly different from each other, they cannot be said to be the same, but are made of the same quality.

(Example 2)
In Example 2, it replaced with the double-sided tape 3, and it carried out similarly to Example 1 except sticking together the two polyurethane sheets 2 only with the adhesive 5. FIG.

(Comparative Example 1)
In Comparative Example 1, a polyurethane sheet 2 is prepared in the same manner as in Example 1 except that cellulose acetate butyrate is not added and back surface buffing is not performed, and one side of a double-sided tape is bonded to the surface opposite to the skin layer. The back pad of Comparative Example 1 was manufactured. Therefore, the back pad of Comparative Example 1 is a conventional back pad that uses a double-sided tape for mounting on a surface plate.

(Evaluation)
Next, with respect to the back pads of the examples and comparative examples, the thickness, the air storage status, and the polished object retention were measured. The thickness was measured using a dial gauge (minimum scale 0.01 mm) and applying a load of 100 g / cm ² . Read back pad 1 of 1 m in length and 1 m in width to 10/10 (0.001 mm) of the minimum scale at a pitch of 10 cm in length and width, and find the average value of thickness, standard deviation σ, and the difference between the maximum thickness and the minimum thickness The range R was obtained. The retention property of the object to be polished was measured by the following method. As shown in FIGS. 6A and 6B, after spraying water on the mounting surface Q of the back pad 1 with a spray, the surface water was lightly removed with a wiper and mounted on a surface plate 81 having a substantially flat surface. . After spraying water on the holding surface P of the back pad 1 with a spray, the surface water is lightly removed with a wiper. Next, a 10 cm long × 10 cm wide glass plate 82 is placed on the polyurethane sheet 2, and a weight 83 is placed on the glass plate 82 so that a load of 80 g / cm ² is applied. After 1 minute, the weight 83 is removed, and the air storage state is visually determined. Then, the glass plate 82 is pulled in the horizontal (horizontal) direction (arrow A direction), and the peak value of the tensile force when the glass plate 82 is displaced. (Maximum value) was measured. The measurement was performed 5 times, and the average value was calculated to evaluate the retention of the workpiece. Table 1 shows the measurement results of thickness, air storage, and workpiece retention. In Table 1, the retention property indicates the retention property of the object to be polished. Table 1 also shows the thickness measurement results for the polyurethane sheet after wet film formation and before buffing. About the thickness of the back pad of the comparative example 1, the numerical value calculated | required by subtracting the thickness of the release paper is shown, including the release paper of the double-sided tape.

  As shown in Table 1, in the back pad of Comparative Example 1 that was not buffed, the thickness range R was 0.049 mm, the standard deviation σ was 0.012 mm, and air retention was also observed. For this reason, the glass substrate or the like cannot be held flat in the back pad of Comparative Example 1, and the thickness variation is large. Therefore, the polishing progresses in a thick place, and the thickness variation of the back pad is transferred to the object to be polished. Therefore, it is not possible to expect a high level of flatness of the workpiece after polishing. On the other hand, in the back pads 1 of Example 1 and Example 2 in which the holding surface P and the back surface N side of the mounting surface Q are buffed, the thickness range R is a numerical value smaller than that of the polyurethane sheet of Comparative Example 1. The standard deviation σ was 0.003 mm and 0.006 mm, respectively, and no air retention was observed. Further, the holding properties were 714N and 729N, respectively, which were the same values as the back pad of Comparative Example 1. From this, it was found that even if the porous layer 8 is formed in the skin layer 2a, the retention of air can be prevented without affecting the retention of the object to be polished. It was found that by buffing the back N side, the thickness accuracy of the polyurethane sheet 2 can be improved and the thickness of the entire back pad 1 can be made uniform. Furthermore, in the back pads 1 of the first and second embodiments, the air accumulation can be eliminated even between the back pad 1 and the surface plate 81 when the back pad 1 is mounted on the surface plate 81. In the back pad of Comparative Example 1 that is attached to the surface plate 81 with a double-sided tape (the adhesive applied to the base material is generally a pressure-sensitive type), it cannot be eliminated if air bites occur. Therefore, a partial swell (convex portion) occurred. If the polishing process is performed in this state, the flatness of the object to be polished will be impaired. Therefore, the air accumulated by opening a hole with a needle or the like is removed, or the back pad is reapplied (the removed back pad is discarded and replaced with a new back pad). ) Was required.

  Moreover, in the back pad 1 of Example 1 and Example 2, the same thing is used for the two polyurethane sheets 2 bonded together. For this reason, it is considered that the adhesive force (adsorptive force) between the mounting surface Q of the back pad 1 and the surface plate 81 is also equivalent to the retainability of the workpiece. As a result of polishing the glass substrate with an Oscar polishing machine using the back pad 1 of Example 1 and Example 2, peeling of the back pad 1 from the pressure surface plate and peeling of the glass substrate from the back pad 1 were performed. None were observed, and no problem with retention occurred. Also, the back pad 1 could be easily attached and detached.

  Furthermore, in the back pad of Comparative Example 1, since double-sided tape was used for mounting on the surface plate 81, wrinkles occurred when reapplied, and it took time and effort to mount flatly. When the back pad of Comparative Example 1 was replaced after the measurement of the workpiece retention, adhesive remained on the surface plate 81, and it took time and effort to remove the remaining adhesive. On the other hand, in the back pad 1 of Example 1 and Example 2, since only water was used for mounting, it could be easily mounted flat even after re-attaching. Even when the back pad 1 of Example 1 and Example 2 was replaced, only the remaining water was wiped off, and it took little effort. Therefore, the back pad 1 in which the two polyurethane sheets 2 are bonded together can be easily and surely attached to the surface plate 81 by the action of water contained in the skin layer 2a, and the glass plate 82 and the like are substantially flat. Can be held in.

  Since the present invention provides a holding pad that can be easily mounted on a surface plate and can improve the workability of mounting, it contributes to the manufacture and sale of the holding pad, and thus has industrial applicability.

It is sectional drawing which shows the back pad of embodiment which concerns on this invention. It is process drawing which shows the manufacturing process of a back pad. It is a front view which shows schematic structure of the film-forming apparatus used for manufacture of the polyurethane sheet of a back pad. It is sectional drawing which shows the change of the polyurethane sheet in a back surface buff processing process, (A) is a polyurethane sheet formed in the film-forming base material, (B) is a polyurethane when the holding surface and the mounting surface are pressed against the pressure roller Sheet (C) shows the polyurethane sheet after the back surface buffing. It is sectional drawing which shows the part holding the to-be-polished object of the single-side polish machine equipped with the back pad. The positional relationship of a back pad, a surface plate, and a to-be-polished object when evaluating the to-be-polished object holding | maintenance of a back pad is shown typically, (A) is a top view, (B) is sectional drawing.

Explanation of symbols

P Holding surface Q Mounting surface 1 Back pad (holding pad)
2 Polyurethane sheet (soft plastic sheet)
2a Skin layer (surface layer)
2b Nap layer 4 PET film 5 Adhesive

Claims (8)

One side is attached to the base, the holding pads other side abuts against the workpiece, the holding pad is bonded is back to back the two flexible plastic sheet, at least the flexible plastic sheet of the two sheets said one has a surface layer formed of a microporous, and characterized in that said surface layer side surface tension of interposed water between the surface layer and the surface plate is mounted on the plate To hold pad. Each of the two soft plastic sheets has a surface layer in which the micropores are formed, and one surface layer side is a surface tension of water interposed between the surface layer and the surface plate. The holding pad according to claim 1, wherein the holding pad is mounted on a surface plate, and the other surface layer side abuts on the object to be polished through water .   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.   The holding pad according to claim 1, wherein the soft plastic sheets are homogeneous.   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.   6. The soft plastic sheet has a foam layer in which foam having a pore size larger than a microporous formed in the surface layer is formed inside the surface layer. The holding pad according to any one of the above.   The soft plastic sheet is further formed on the surface layer with a pore having a pore size larger than the micropore formed in the surface layer and a pore size smaller than the foam formed in the foam layer. The holding pad according to claim 6, wherein the holding pad communicates with 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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