JP4566660B2 - Polishing cloth for finish polishing and method for manufacturing polishing cloth - Google Patents

Description

The present invention relates to a polishing cloth for finishing polishing and a method for manufacturing the polishing cloth, and in particular, has a soft plastic foam produced by a wet film forming method, and a skin layer having micro-flatness is formed on the surface of the soft plastic foam. The present invention relates to a finished polishing cloth for finishing polishing and a method for producing the polishing cloth.

  Conventionally, flatness is improved in flat processing of optical materials such as lenses, parallel flat plates, reflecting mirrors, hard disk substrates, silicon wafers, liquid crystal glass, etc. that require high precision flatness (objects to be polished). In order to achieve this, a polishing process (primary polishing) is performed and then a finishing process (secondary polishing) is performed. In particular, the capacity of hard disks is being increased, and in order to improve high-density storage and reading accuracy, an aluminum substrate for next-generation hard disks of large capacity (for example, 100 to 120 gigabytes) has a higher precision. Sex is required.

  In general, a polishing cloth having a soft plastic foam is used for finishing. Soft plastic foams are manufactured by applying a resin solution in which a soft plastic is dissolved in a water-miscible organic solvent to a sheet-like substrate and then coagulating and regenerating the resin in an aqueous coagulation liquid (wet film formation method). The Inside the manufactured flexible plastic foam, many foams are formed as the resin coagulates and regenerates. On the surface, foams smaller than the size of the foam inside are densely formed. A layer (skin layer) is formed. The surface of the skin layer has micro-flatness due to the densely formed foam. Using the micro flatness of the skin layer, finishing work is performed on an object to be polished, particularly an aluminum substrate for a hard disk.

  However, in the production of flexible plastic foams, the resin solution has viscosity, resulting in variations in thickness when applied to the substrate, and foam formation during solidification regeneration (organic solvent and aqueous coagulation) due to the wet film formation method. Variation in thickness is likely to occur due to replacement with liquid. For this reason, since the macro flatness of the surface of the flexible plastic foam itself is impaired (becomes a largely wavy surface), it is difficult to improve the flatness of the object to be polished during the finishing process. In other words, in order to improve the flatness of the object to be polished, the macro flatness is reduced by reducing the thickness variation of the soft plastic foam itself while keeping the micro flatness of the skin layer used for finishing. It is important to improve.

  In order to improve the macro flatness by reducing the thickness variation of the soft plastic foam itself and improve the retention of the polishing liquid (slurry), the surface of the soft plastic foam is buffed (surface sanding). It has been subjected. For example, a suede-like polishing cloth in which the surface of a soft plastic foam is buffed to have a surface roughness of 50 μm or less and foam is opened on the surface is disclosed (see Patent Document 1). In addition, a polishing cloth is disclosed that has been subjected to surface buffing so as to prevent the foaming of the flexible plastic foam from being opened, leaving the micro flatness of the surface skin layer (see, for example, Patent Document 2).

Japanese Patent No. 3187769 JP 2001-62704 A

  However, in the polishing cloth of Patent Document 1, since foaming is open on the surface, there is a limit in reducing the surface roughness, and it is difficult to improve the flatness of the object to be polished in the above-described finishing process. . Further, in the method of Patent Document 2, although the skin layer remains on the surface, the thickness of the skin layer is partially reduced by the buffing process, so that the skin layer is worn in a short time during the finishing process and the opening becomes large. (For example, 40 μm or more), the surface roughness of the polishing cloth is deteriorated. Furthermore, since the thickness of the skin layer is only about several μm and is smaller than the variation in the thickness of the polishing cloth, the skin layer disappears when the buffing is performed to eliminate the variation in the thickness of the polishing cloth. In addition, if the skin layer is left, the variation in thickness generated during film formation remains as the variation in the thickness of the polishing cloth. Therefore, the macro flatness required in the finishing processing of the aluminum substrate for the next-generation hard disk described above, etc. It becomes difficult to satisfy sex.

  An object of the present invention is to provide a polishing cloth for finish polishing that can improve the flatness of an object to be polished and a method for manufacturing the polishing cloth.

In order to solve the above-mentioned problems, a first aspect of the present invention is a soft plastic foam produced by a wet film-forming method, and a skin layer having micro flatness is formed on the surface of the soft plastic foam. in polishing cloth for finish polishing, the soft plastic foam, as well as substantially a left thickness leaving the skin layer uniformly to remove macroscopic undulation on the surface of the skin layer, the skin layer The formed surface and the flat surface of the jig are brought into pressure contact with each other, and the surface opposite to the surface on which the skin layer is formed is buffed.

In a first aspect, to remove macroscopic undulation on the surface of the skin layer with a substantially uniform thickness while leaving the skin layer of soft plastic foam, the surface and the jig which skin layer is formed since a flat surface is pressed against the opposite side of the surface skin layer is formed of being buffed, since the irregularities appearing on the opposite side depending on the roughness of the surface of the skin layer is removed, the micro The thickness of the flexible plastic foam is almost uniform and the macro flatness is improved while leaving the skin layer having a smooth flatness, so that the flatness of the surface of the workpiece can be improved by using it for finish polishing. Can do.

The second aspect of the present invention is a polishing cloth for final polishing, comprising a soft plastic foam produced by a wet film forming method, and a skin layer having micro-flatness formed on the surface of the soft plastic foam. The soft plastic foam has a first support layer of a nonwoven fabric or a woven fabric that supports the soft plastic foam on the opposite side of the surface on which the skin layer is formed , leaving the skin layer. to remove macroscopic undulation in the soft plastic foam and a surface of said skin layer with a substantially uniform total thickness of the first support layer remains, Osamu surface of the skin layer is formed The flat surface of the tool is brought into pressure contact with the surface of the first support layer opposite to the soft plastic foam, and is buffed.

In the second aspect, the soft plastic foam has a first support layer of a nonwoven fabric or a woven fabric that supports the soft plastic foam on the opposite side of the surface on which the skin layer is formed , leaving the skin layer. and leave the total thickness of the soft plastic foam and the first support layer with a substantially uniform so as to remove the macroscopic undulation on the surface of the skin layer, the flat surface and the jig which skin layer is formed since the opposite side with soft plastic foam of the first supporting layer is pressed against the surface is buffed, since the irregularities appearing on the opposite side depending on the roughness of the surface of the skin layer is removed, the micro such the thickness of the leaving the skin layer having a flatness soft plastic foam and the first support layer is improved substantially uniform macroscopic flatness, polished by using a finish polishing It is possible to improve the flatness of the surface of the.

  1st and 2nd aspect WHEREIN: It is 1 type selected from a flexible film, a nonwoven fabric, and a woven fabric at the surface side by which the polishing cloth was buffed, and the 2nd support layer which supports a flexible plastic foam May further be included. The material of the flexible plastic foam may be polyurethane.

The third aspect of the present invention is a polishing cloth for final polishing, comprising a soft plastic foam produced by a wet film forming method, and a skin layer having micro-flatness formed on the surface of the soft plastic foam. a method of manufacturing, the flexible plastic foam to a wet film formation, the soft plastic foam surface skin layer is formed of, the skin is brought into contact with the flat surface of the jig having a flat surface The opposite surface of the surface on which the layer is formed is buffed so that the thickness of the flexible plastic foam is substantially uniform while leaving the skin layer, and the macro waviness on the surface of the skin layer is removed. Including a step.

In the third aspect, the soft plastic produced during the wet film formation is brought into contact with the surface on which the skin layer of the soft plastic foam formed by the wet film is formed by contacting the flat surface of the jig having a flat surface. are allowed to occur as uneven thickness variation of the foam on the opposite side of the surface skin layer is formed, a surface opposite to the irregularities appeared in the skin layer with a substantially uniform thickness of the soft plastic foam By buffing so as to remove macro waviness on the surface, the thickness variation of the soft plastic foam is reduced, so the thickness accuracy is improved while leaving the skin layer with micro flatness, and the macro flatness It is possible to obtain a soft plastic foam with improved properties, and thus an abrasive cloth. In this case, the method further includes a step of bonding a support layer supporting at least one of a flexible film, a nonwoven fabric and a woven fabric to the buffed surface side of the flexible plastic foam. You may make it.

According to the present invention, the surface on which the skin layer is formed and the flat surface of the jig are pressed against each other so that the thickness of the flexible plastic foam is substantially uniform and macro waviness on the surface of the skin layer is removed. Since the opposite surface side of the surface on which the skin layer is formed is buffed, the unevenness appearing on the opposite surface side is removed in accordance with the unevenness on the surface of the skin layer , so the skin having micro flatness Since the thickness of the flexible plastic foam is almost uniform with the layer remaining and the macro flatness is improved , the flatness of the surface of the object to be polished can be improved by using it for finish polishing. Obtainable.

  Embodiments of a polishing pad used for precision finish polishing to which the present invention is applicable will be described below with reference to the drawings.

(Polishing pad)
As shown in FIG. 1A, the polishing pad 1 has a polyurethane sheet 2 as a soft plastic foam formed of a polyurethane resin. The polyurethane sheet 2 is buffed so that the thickness (length in the vertical direction in FIG. 1) of the polyurethane sheet 2 is substantially uniform on the back surface (lower surface) side opposite to the polishing surface P (details). Later). For example, when the average thickness is about 0.7 mm, the polyurethane sheet 2 is formed so that the difference between the maximum thickness and the minimum thickness is about 20 μm or less. For this reason, the polyurethane sheet 2 has a flat polished surface P.

  In the polyurethane sheet 2, a fine foam (not shown) is formed on the polishing surface P side, and a skin layer 4 having micro flatness is formed. In the lower layer of the skin layer 4, the foam 3 having a substantially triangular cross section rounded along the thickness direction of the polyurethane sheet 2 is formed. The space volume of the foam 3 is formed such that the size on the polishing surface P side is smaller than the back surface side of the polishing surface P. In the polyurethane resin between the foams 3, foam (not shown) having a space volume larger than the foam formed in the skin layer 4 and smaller than the foam 3 is formed. The foam 3 and the foam (not shown) are connected in a three-dimensional mesh shape with communication holes (not shown) larger than the diameter of the space volume of the foam formed in the skin layer 4. Since the back surface side of the polishing surface P is buffed, the foam 3 and a part of the foam (not shown) are opened on the surface on the back surface side.

  Further, the polishing pad 1 has a support layer 6 as a second support layer that supports the polyurethane sheet 2 on the back surface side (buffed surface side) of the polishing surface P. For the support layer 6, at least one selected from a flexible film such as a polyethylene terephthalate (hereinafter abbreviated as PET) film, a nonwoven fabric, or a woven fabric is used. On the lower surface side of the support layer 6, a double-sided tape 7 having a release paper 8 on the other surface side (lowermost surface side) for attaching the polishing pad 1 to a polishing machine is bonded.

(Manufacture of polishing pad)
The polishing pad 1 is manufactured through each process shown in FIG. First, in the preparation step, N, N-dimethylformamide (hereinafter abbreviated as DMF), which is a water-miscible organic solvent capable of dissolving the polyurethane resin, and an additive are mixed to dissolve the polyurethane resin. As the polyurethane resin, a polyester resin, a polyether resin, a polycarbonate resin, or the like is selected and used. For example, the polyurethane resin is dissolved in DMF so as to be 30%. As the additive, a pigment such as carbon black, a hydrophilic activator that promotes foaming, and a hydrophobic activator that stabilizes the coagulation regeneration of the polyurethane resin are used to control the size and amount (number) of foam 3. be able to. 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. Thereafter, the polyurethane sheet 2 is obtained by drying. 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) that pretreats a nonwoven fabric or a woven cloth of a film forming substrate. Pretreatment tank 10, coagulation tank 20 filled with coagulation liquid 25 mainly composed of water which is a poor solvent for polyurethane resin for coagulating and regenerating polyurethane resin, water for washing polyurethane resin after coagulation and regeneration A cleaning tank 30 filled with a cleaning liquid 35 such as the above 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 a film forming substrate 43 is disposed. The pretreatment tank 10 has a pair of guide rollers 13 at the lower part inside the substantially central part in the same longitudinal direction as the transport direction of the film forming substrate 43. Above the pretreatment tank 10, guide rollers 11 and 12 are disposed on the substrate supply roller 41 side, and an excessive pretreatment liquid contained in the pretreated film forming substrate 43 is disposed on the coagulation tank 20 side. 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. The conveyance speed of the film-forming substrate 43 is set to 2.5 m / min in this example, and is preferably set in the range of 1.0 to 5.0 m / min.

  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 the present embodiment, the film forming substrate 43 will be 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 coagulation liquid 25, first, the skin layer 4 having a thickness of several μm is formed on the surface of the applied polyurethane resin solution 45. Thereafter, the polyurethane resin coagulates and regenerates on one surface of the film forming substrate 43 as the substitution of the DMF in the polyurethane resin solution 45 and the coagulating liquid 25 proceeds. This 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. When DMF removes the solvent from the polyurethane resin solution 45, foam 3 is formed in the polyurethane resin. 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 (polyurethane sheet 2) is taken up by the take-up roller 42 together with the film-forming substrate 43.

  In the back surface buffing process, the back surface side of the polishing surface P is buffed with the dried polyurethane sheet 2. 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 at the time of film formation, the polished surface P is uneven. After the film-forming substrate 43 is peeled off, as shown in FIG. 4B, the polishing surface P becomes flat by pressing the surface of the pressure roller 65 having a flat surface against the surface of the polishing surface P. Unevenness appears on the back surface Q side of the polished surface P. Unevenness appearing on the back Q side is removed by buffing. In this example, since the continuously manufactured polyurethane sheet 2 has a belt shape, the back surface Q side is continuously buffed while the pressure roller 65 is pressed against the polishing surface P. As a result, as shown in FIG. 4C, the thickness variation of the polyurethane sheet 2 on which the back surface Q side is buffed to form the flat back surface Q 'is eliminated. In FIG. 4 (C), the polishing surface P and the back surface Q ′ are shown flat for easy understanding. However, in the single body of the polyurethane sheet 2, unevenness that makes the thickness of the polyurethane sheet 2 uniform on both surfaces. The surface becomes flat when the support layer 6 is bonded or attached to a polishing machine.

  As shown in FIG. 2, in the laminating process, a support layer 6 of a PET film is bonded to the back surface Q ′ side of the buffed polyurethane sheet 2. On the opposite side of the support layer 6, a double-sided tape 7 having a release paper 8 attached to the other side is bonded. After cutting into a desired shape such as a circle in the cutting process, the polishing pad 1 is completed by performing inspections such as confirming that there is no adhesion of dirt or foreign matter.

  When polishing the object to be polished with the obtained polishing pad 1, for example, the polishing pad 1 is attached to the upper surface plate and the lower surface plate of the double-side polishing machine. In the double-side polishing machine, an object to be polished is sandwiched between two polishing pads 1 attached to an upper surface plate and a lower surface plate, and both surfaces are simultaneously polished. The surface to which the polishing pad 1 is applied, that is, the lower surface of the upper surface plate and the upper surface of the lower surface plate are both formed flat. For this reason, the polishing pad 1 affixed to the upper surface plate and the lower surface plate forms a flat surface.

(Function)
Next, the operation and the like of the polishing pad 1 of the present embodiment will be described.

  In the polishing pad 1 of this embodiment, the polyurethane sheet 2 is buffed on the back surface Q side of the polishing surface P after wet film formation. In the buffing process, the pressing roller 65 is brought into pressure contact with the polishing surface P to remove the irregularities appearing on the back surface Q side. For this reason, the thickness accuracy of the polyurethane sheet 2 can be improved without reducing the skin layer 4 having micro-flatness (thickness variation generated during film formation can be reduced). By sticking the obtained polishing pad 1 to the surface plate of the polishing machine, the polishing surface P, that is, the skin layer 4 forms a flat surface. Therefore, by using the polishing pad 1 for finish polishing, the object to be polished is polished on the surface of the flat skin layer 4, so that the flatness of the object to be polished can be improved.

  Moreover, in the polishing pad 1 of this embodiment, the support layer 6 of the PET film is bonded to the buffed back surface Q ′ side. For this reason, since the flexible polyurethane sheet 2 is supported by the support layer 6, the handling at the time of conveyance of the polishing pad 1 or attachment to a polishing machine can be facilitated. Furthermore, in the polishing pad 1 of the present embodiment, since the polyurethane sheet 2 is made of polyurethane resin and has elasticity, the polishing pad 1 and the object to be polished can be contacted substantially evenly, and the flatness of the object to be polished is improved. Can be made.

  In the conventional wet film formation method used for the production of polishing pads, there is a variation in the conveying speed when the polyurethane resin solution having viscosity is applied to the film forming substrate and the fluctuation of the coating apparatus. Variations in thickness occur. Since variation in thickness occurs at the time of application, the variation in thickness remains in the polyurethane resin that is coagulated and regenerated by being immersed in the coagulation liquid in that state. In the coagulation liquid, DMF in the polyurethane resin solution and water in the coagulation bath are replaced through a skin layer formed on the surface of the polyurethane resin solution, and foam is formed inside the polyurethane resin. When a uniform skin layer is not formed, the solvent removal becomes non-uniform and the thickness variation further increases. In order to reduce the variation in thickness, the surface of the polishing pad is buffed after the wet film formation. However, by buffing the surface, the skin layer effective for finish polishing disappears, and foaming opens on the surface of the polyurethane sheet. For this reason, there is a limit to the reduction of the surface roughness, and it is difficult to improve the flatness of the object to be polished by finish polishing. Also, since the thickness of the skin layer is smaller than the variation in the thickness of the polyurethane sheet, the variation in the thickness of the polyurethane sheet cannot be eliminated without leaving the skin layer, and the thickness of the skin layer is partially Therefore, the skin layer is worn in a short time during the flat processing, and the foam is easily opened, so that the surface state becomes uneven and the flatness of the object to be polished is lowered. The present embodiment is a polishing pad that can solve these problems.

  In the polishing pad 1 of the present embodiment, the example in which the back surface Q side is continuously buffed while the pressure roller 65 is pressed against the polishing surface P is shown, but the present invention is not limited to this. For example, after the polyurethane sheet 2 is cut into a desired size, a flat plate having a flat surface may be pressed against the polishing surface P to buff the back surface Q side.

  Moreover, in the polishing pad 1 of this embodiment, although the example which bonds the support layer 6 of the film made from PET to the buffed polyurethane sheet 2 was shown, this invention is not limited to this, For example, a nonwoven fabric Or a woven fabric or the like may be attached. Alternatively, the polyurethane sheet 2 may be attached to the polishing machine alone without attaching a PET film or the like. Furthermore, in the polishing pad 1 of the present embodiment, the example in which the foam 3 is opened on the buffed surface (back surface Q ′) side of the polyurethane sheet 2 is shown, but the thickness variation during film formation is small. If so, the thickness removed by the buffing process can be reduced, so the foam 3 does not necessarily open.

  Furthermore, in this embodiment, although the example which uses the film made from PET for the film-forming base material 43 was shown, this invention is not limited to this, For example, you may use a nonwoven fabric and a woven fabric. When a non-woven fabric or a woven fabric is used for the film forming substrate 43, it is difficult to peel off the film forming substrate 43 after the polyurethane resin is solidified and regenerated. What is necessary is just to buff so that the whole thickness with the film-forming base material 43 may become substantially uniform. At this time, the non-woven fabric or woven fabric film-forming substrate 43 may be used as it is as the first support layer, or the support layer 6 as the second support layer may be bonded to the back side of the first support layer. That is, as shown in FIG. 1B, in another embodiment of the polishing pad 1 ′ to which the present invention can be applied, the polyurethane sheet 2 is formed on one surface side of the film forming substrate 43. The other surface (back surface) side of 43 is buffed. For this reason, the first support layer is formed by the film formation substrate 43. A support layer 6 is bonded to the back surface (buffed surface) side of the film forming substrate 43, and a double-sided tape 7 with a release paper 8 is bonded to the support layer 6.

  Furthermore, in this embodiment, although the polyurethane resin was illustrated as a flexible plastic foam, this invention is not limited to this, For example, you may use a polyester resin etc. If a polyurethane resin is used, a continuous foam can be easily formed by a wet method. In the present embodiment, an example in which the polyurethane resin is dissolved in DMF so as to be 30% is shown, but the present invention is not limited to this, and the viscosity of the polyurethane resin solution 45 and the thickness of the polyurethane sheet 2 are not limited thereto. It may be appropriately changed depending on the situation.

  Furthermore, in this 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, and the substrate 43 can be applied to a substantially uniform thickness. 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.

  In the present embodiment, the obtained polyurethane sheet 2 is buffed on the opposite surface of the polishing surface P by a buffing machine or the like, but the buffing amount is 2 in the thickness range R of the sheet 2 (details will be described later). It is desirable to buff the thickness more than twice. 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.

  Hereinafter, examples of the polishing pad 1 manufactured according to the present embodiment will be described. A comparative polishing pad manufactured for comparison is also shown.

Example 1
In Example 1, polyester MDI (diphenylmethane diisocyanate) polyurethane resin was used as the polyurethane resin. To 100 parts of this DMF solution of polyurethane resin, 45 parts of DMF for viscosity adjustment, 40 parts of DMF dispersion containing 30% pigment carbon black, and 2 parts of hydrophobic activator were mixed to form a polyurethane resin solution. 45 was prepared. When applying the polyurethane resin solution 45, the clearance of the coating device was set to 0.9 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 (detailed later) of 0.008 mm. As shown in Table 1 below, the polishing pad 1 of Example 1 was manufactured by buffing using a sandpaper of buff count # 180 with the buff treatment amount of the polyurethane sheet 2 being 0.14 mm. In addition, when converted from the weight per unit area of the polyurethane sheet 2, the application amount of the polyurethane resin solution 45 is 760 g / m ² (solid conversion 170 g / m ² ).

(Example 2)
As shown in Table 1, in Example 2, the polishing pad 1 of Example 2 was produced in the same manner as in Example 1 except that the buff processing amount was 0.22 mm.

(Comparative Example 1)
As shown in Table 1, in Comparative Example 1, the polishing pad of Comparative Example 1 was produced in the same manner as in Example 1 except that the buff treatment was not performed. That is, Comparative Example 1 is a conventional polishing pad.

(Evaluation)
Next, about the polyurethane sheet 2 produced by each Example and the comparative example, the thickness and surface roughness after a buff process 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 polyurethane sheet 2 (length 1m x width 1m) at a pitch of 10cm to width 1/10 (0.001mm) of the minimum scale, and find the average thickness, standard deviation σ, and the difference between the maximum thickness and the minimum thickness. The range R was obtained. The surface roughness is measured using a surface roughness measuring machine (SURFTEST, manufactured by Mitutoyo Co., Ltd.), with a speed curve of 0.5 mm / s and a reference length of 0.8 mm. Was measured twice. From the obtained roughness curve, an average value of absolute values of deviation from the average line to the measurement curve is obtained as an average roughness Ra, and the height from the average line to the highest measurement curve and the depth to the lowest measurement curve are calculated. The total was determined as the maximum height Ry. The measurement results of the thickness and the surface roughness are shown in Table 2 below.

  As shown in Table 2, in the polyurethane sheet of Comparative Example 1 that was not buffed, the thickness range R was 0.040 mm, the average roughness Ra of the surface roughness was 0.53 μm, and the maximum height Ry was 3. 3 μm is shown. For this reason, even if finish polishing of the aluminum substrate for hard disks etc. is performed using the polyurethane sheet of Comparative Example 1, high flatness cannot be expected. On the other hand, in the polyurethane sheet 2 of Example 1 and Example 2 in which the back surface Q side of the polishing surface P was buffed, the average roughness Ra and the maximum height Ry of the surface roughness representing micro flatness are not so much. Although not changed, the thickness range R representing macro flatness is smaller than that of the polyurethane sheet of Comparative Example 1. From this, it was found that the thickness accuracy of the polyurethane sheet 2 can be improved by buffing the back surface Q side. By performing final polishing with the polishing pad 1 using this polyurethane sheet 2, it can be expected that the surface of the object to be polished is flattened with high accuracy.

  INDUSTRIAL APPLICABILITY The present invention contributes to the manufacture and sale of polishing cloths for providing a polishing cloth for finishing polishing that can improve the flatness of an object to be polished and a method for manufacturing the polishing cloth. Have sex.

It is sectional drawing which shows the polishing pad for final polishing which can apply this invention, (A) is the polishing pad of embodiment which bonded the 2nd support layer to the buffed polyurethane sheet, (B) is buff processing. The polishing pad of another aspect which bonded together the 1st support layer to the formed film-forming base material is each shown. It is process drawing which shows the manufacturing process of the polishing pad of embodiment. It is a front view which shows schematic structure of the film-forming apparatus used for manufacture of the polyurethane sheet of a polishing 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 sheet when it press-contacts to a press-contact roller, (C) is The polyurethane sheets after the buffing are respectively shown.

Explanation of symbols

P Polished surface Q Back surface (opposite surface)
1 Polishing pad (polishing cloth)
2 Polyurethane sheet (soft plastic foam)
4 Skin layer (foamed surface layer)
6 PET film (second support layer)
43 Film Formation Base 65 Pressing Roller

Claims (6)

In a polishing cloth for final polishing having a soft plastic foam produced by a wet film forming method and having a skin layer having micro-flatness on the surface of the soft plastic foam, the soft plastic foam includes the skin layer to remove macroscopic undulation on the surface of the skin layer with a substantially uniform thickness while leaving the skin and the flat surface of the surface and the jig which the skin layer is formed by pressing A polishing cloth, wherein a surface opposite to a surface on which a layer is formed is buffed. In a polishing cloth for final polishing having a soft plastic foam produced by a wet film forming method and having a skin layer having micro-flatness on the surface of the soft plastic foam, the soft plastic foam includes the skin layer On the opposite side of the surface on which the soft plastic foam is formed, the first support layer of nonwoven fabric or woven fabric supporting the soft plastic foam is provided, and the soft plastic foam and the first support are left with the skin layer left. with a substantially uniform overall thickness of the layer so as to remove the macroscopic undulation on the surface of the skin layer, the a flat surface of the surface and the jig which the skin layer is formed by pressing the An abrasive cloth, wherein the surface of the support layer 1 opposite to the soft plastic foam is buffed.   The abrasive cloth is at least one selected from a flexible film, a nonwoven fabric, and a woven cloth on the buffed surface side, and further includes a second support layer that supports the flexible plastic foam. The polishing cloth according to claim 1 or 2, characterized by the above-mentioned.   The abrasive cloth according to any one of claims 1 to 3, wherein the flexible plastic foam is made of polyurethane. A method for producing a polishing cloth for final polishing, comprising a soft plastic foam produced by a wet film-forming method and having a skin layer having micro-flatness on the surface of the soft plastic foam,
Wet film formation of the soft plastic foam,
The flat surface of a jig having a flat surface is brought into contact with the surface of the soft plastic foam on which the skin layer is formed , leaving the skin layer on the opposite side of the surface on which the skin layer is formed. And buffing so that the thickness of the flexible plastic foam is substantially uniform and macro waviness on the surface of the skin layer is removed .
The manufacturing method characterized by including a step.   The method further includes a step of bonding a support layer that supports at least one of a flexible film, a nonwoven fabric, and a woven fabric to the buffed surface side of the flexible plastic foam and that supports the flexible plastic foam. The manufacturing method according to claim 5, wherein:

Images