JP6582057B2 - Polishing pad, polishing method using the polishing pad, and method of using the polishing pad - Google Patents

Description

  The present invention relates to a hard resin foam polishing pad that is excellent in polishing characteristics and reusability and polishes the surface of an object to be processed, a polishing method using the polishing pad, and a method of using the polishing pad.

  Conventionally, polishing processing of thin plate members such as magnetic disks and semiconductor wafers in hard disk drives (HDDs) requires processing that does not cause microscopic scratches or latent scratches on the surface of the object to be processed. While supplying the contained slurry, smooth mirror surface processing is performed using a non-woven or foamed polishing pad. In particular, polishing in which a chemical action is combined with a mechanical polishing method is called chemical mechanical polishing (CMP) and is widely used in the field of ultraprecision processing.

  As a polishing pad used in such a polishing process, for example, there is a polishing pad which is a suede-like polishing cloth and has a base material portion made of a nonwoven fabric and a nap layer made of a polyurethane resin (Patent Document 1). In this polishing pad, by setting the thickness (nap length) of the nap layer to 500 μm or more, the nap layer in contact with the object to be processed can maintain an appropriate elasticity or can cause scratches. However, it is considered that it can be taken into the nap layer having a long nap length, thereby preventing the occurrence of minute scratches.

  As another conventional polishing pad, a polishing pad having a foam made of polyurethane resin has been proposed (Patent Document 2). In this polishing pad, the polyurethane resin foam can realize polishing with excellent flatness, and the foam reacts with the epoxy group in the epoxy group-containing urethane prepolymer and the amine-based curing material. Since it has the generated hydroxyl group, the retention of the slurry can be improved by the hydroxyl group, and the polishing rate can be improved.

JP 2002-59356 A JP 2013-252584 A

  However, in the conventional suede-like polishing pad, the polishing rate is not constant because the polyurethane resin nap layer is worn and gradually shortened by continuous use. In particular, since the polishing rate at the start of polishing is smaller than the polishing rate in a steady state, preliminary polishing must be performed until the polishing rate becomes substantially constant, which is complicated. In addition, in the production process, there is a desire to make the polishing time for all the objects to be processed on the production line as constant as possible from the viewpoint of efficiency, but if the polishing time is made constant, it is processed at the initial stage. Further, there is a problem that the polishing of the object to be processed becomes insufficient and the reliability of the polishing process is lowered.

  In addition, although other conventional foamed polishing pads are disclosed that the polishing rate is good when a polyurethane resin foam is used, the difference between the polishing rate at the start of polishing and the polishing rate in a steady state is disclosed. Is not disclosed, and the problems associated with the differences are not disclosed.

  The object of the present invention is to realize simple polishing by eliminating the time for preliminary polishing or shortening it as much as possible, and by continuously polishing at an excellent polishing rate from the initial stage, it is efficient and reliable. An object of the present invention is to provide a polishing pad having a hard resin foam made of a thermoplastic resin that can be polished with high performance and excellent in re-polishing properties, a polishing method using the polishing pad, and a method of using the polishing pad.

  As a result of intensive studies to achieve the above object, the present inventors have paid attention to the three-dimensional structure in the polishing pad of a high-rigidity thermoplastic resin foam, and the cell diameter and cell wall of the cell forming the resin foam By defining the ratio of the thickness and the cell diameter to the cell wall thickness within a predetermined range, an excellent polishing rate can be realized from the initial stage of polishing and the polishing rate can be continuously expressed and the product after polishing It was found that the surface quality was excellent. Furthermore, the present inventors have found that a highly rigid thermoplastic resin foam that is less likely to decrease in flexural modulus due to water absorption during polishing and that is excellent in reusability after polishing is interrupted. The present invention has been made based on such findings.

That is, the present invention is achieved by the following.
(1) having a resin foam made of a thermoplastic resin having a three-dimensional cell structure configured by being partitioned by a cell wall so that a plurality of cells and these cells have mutually independent partitions; Tensile strength is 50MPa to 90MPa and bending strength is 90MPa to 140MPa as mechanical properties of the wall portion of the cell wall constituting the three-dimensional cell structure of the foam as mechanical properties of the resin sheet material before foaming. Thus, both the tensile elastic modulus and the bending elastic modulus satisfy 2400 MPa or more, the average cell diameter is 4 μm to 50 μm, the average cell wall thickness is 1 μm to 5 μm, and the ratio of the average cell diameter to the average cell wall thickness is 4. A polishing pad in the range of -10.
(2) The polishing pad according to (1) above, wherein the resin foam is made of any one of polyphenylene sulfide resin, polyethylene terephthalate resin and polycarbonate resin.
(3) The polishing pad according to (2) above, wherein the resin foam is made of any one of a polyphenylene sulfide resin and a polyethylene terephthalate resin.
(4) The tensile strength is 70 MPa to 90 MPa, the bending strength is 120 MPa to 140 MPa, the tensile strength is 70 MPa to 90 MPa, and the mechanical properties of the cell wall portion of the resin foam are expressed as the mechanical properties of the resin sheet material before foaming. The polishing pad according to (3) above, wherein both the elastic modulus and the bending elastic modulus satisfy 3000 MPa to 4200 MPa.
(5) having a resin foam made of a thermoplastic resin having a three-dimensional cell structure configured such that a plurality of cells and these cells are partitioned by a cell wall so as to have mutually independent partitions; The foam is made of hydrophobic polyphenylene sulfide resin, and the tensile modulus is the flexural modulus as the mechanical property of the cell wall of the resin foam is expressed by the mechanical property of the resin sheet material before foaming. Larger, the tensile elastic modulus is 3000 MPa to 3500 MPa, the bending elastic modulus is in the range of 3800 MPa to 4200 MPa, the bending elastic modulus does not decrease due to water absorption or 10% or less, and the average cell diameter is 4 μm to 50 μm, The average cell wall thickness is 1 μm to 5 μm, and the ratio of the average cell diameter to the average cell wall thickness is in the range of 4 to 10. Head.
(6) Any of the above (1) to (5), wherein the polishing pad can be used without a cushion layer, and can be polished at a higher speed than a polishing pad made of a hard urethane foam structure. A polishing pad according to claim 1.
(7) The polishing pad according to any one of (1) to (6) above, wherein the polishing pad has a water absorption of 0.02 to 0.20% and is excellent in reusability.
(8) The lowering of the bending elastic modulus after water absorption with respect to the bending elastic modulus before water absorption in the immersion test at 25 ° C. for 48 hours of the resin sheet material before foaming for the polishing pad is 20% or less, The polishing pad according to any one of (1) to (6).
(9) The object to be processed is a hard material of any one of a glass plate for hard disk drive, a silicon wafer, a liquid crystal glass, a sapphire substrate, a compound semiconductor, a GaN substrate, and a SiC substrate. The polishing pad according to any one of (1) to (8) above.
(10) The polishing pad according to any one of (1) to (9) above, further comprising a cushion layer disposed on the opposite side of the polishing surface of the resin foam.
(11) In the polishing pad according to (10), the compression elastic modulus of the cushion layer is smaller than the compression elastic modulus of the polishing pad, and the thickness of the cushion layer is greater than that of the cushion layer and the resin foam. A polishing pad having a thickness within 10 to 40% of the total thickness of the body.
(12) Using the polishing pad having no cushion layer according to any one of (1) to (9), the surface of the object to be processed in a state in which the resin foam of the polishing pad and the object to be processed are pressed against each other Is polished while supplying a polishing liquid containing abrasive grains to the resin foam.
(13) Using the polishing pad including the cushion layer according to (10) or (11) above, the surface of the object to be processed is in a state where the resin foam of the polishing pad and the object to be processed are pressed against each other. A polishing method comprising polishing while supplying a polishing liquid containing a resin to the resin foam.
(14) The polishing method according to (12) or (13) above, wherein the abrasive grains are any of alumina particles, zirconia particles, colloidal silica particles, and ceria particles.
(15) When the use of the polishing pad according to any one of (1) to (11) above is temporarily suspended and then reused, the surface of the polishing pad is merely washed and re-polishing is not performed. A method of using a polishing pad, wherein the polishing pad is reused.

  According to the present invention, there is provided a resin foam made of a thermoplastic resin having a three-dimensional cell structure configured by being partitioned by a cell wall so that a plurality of cells and these cells have mutually independent partitions. The tensile strength is 50 MPa to 90 MPa, the bending strength is a value representing the mechanical properties of the wall portion of the cell wall constituting the three-dimensional cell structure of the resin foam as the mechanical properties of the resin sheet material before foaming 90 MPa to 140 MPa, both the tensile modulus and the flexural modulus are 2400 MPa or more, the average cell diameter of the resin foam is 4 μm to 50 μm, the average thickness of the cell wall is 1 μm to 5 μm, and the average cell of the average cell diameter A highly rigid structure is formed in the vicinity and inside of the polished surface whose ratio to the wall thickness is in the range of 4-10. Therefore, an excellent polishing rate can be realized from the polishing start stage. Here, from the viewpoint of manufacturability and cell structure stability, the cell diameter is preferably 4 μm to 40 μm.

  Therefore, it is possible to realize simple polishing by eliminating the time for preliminary polishing or shortening it as much as possible, and by performing continuous polishing at an excellent polishing rate from the initial stage, efficient and reliable polishing. Can be realized. Here, the ratio of the average cell diameter of the resin foam to the average cell wall thickness needs to be in the range of 4-10.

  Further, if the tensile strength of the cell wall portion of the resin foam is 70 MPa to 90 MPa, the bending strength is 120 MPa to 140 MPa, and the tensile elastic modulus and the bending elastic modulus are both 3000 MPa to 4200 MPa, the polishing rate is high. Fine polishing can be realized. As such a resin foam, polyphenylene sulfide resin or PET resin having high strength and high rigidity is preferable.

  Here, when the resin foam is made of a hydrophobic polyphenylene sulfide resin, the mechanical properties of the wall portion of the cell wall of the resin foam are expressed as mechanical properties of the resin sheet material before foaming, The bending elastic modulus is larger than the tensile elastic modulus, the tensile elastic modulus is 3000 MPa to 3500 MPa, the bending elastic modulus is in the range of 3800 MPa to 4200 MPa, the average cell diameter is 4 μm to 50 μm, and the average cell wall thickness is 1 μm to 5 μm. Since the ratio between the average cell diameter and the average cell wall thickness is in the range of 4 to 10, the cell structure is stable and stable polishing is possible. In addition, there is no decrease in the flexural modulus due to water absorption or it is 10% or less, and the secondary particles are less likely to aggregate inside the cell, so that a pad with excellent reusability can be obtained.

  In particular, if the resin foam is molded from a resin such as polyphenylene sulfide resin, a better polishing rate can be obtained from the initial stage, and the average cell diameter, the average cell wall thickness, and the unit area It becomes possible to easily produce a resin foam having the number of cells. Moreover, by using polyphenylene sulfide resin, it is excellent in chemical resistance and heat resistance, and polishing corresponding to the liquid composition of many slurries can be realized. Here, if a polishing pad of polyphenylene sulfide resin foam is used, the rise time at the initial polishing until the polishing rate becomes about 1.30 μm / min can be realized about 25 minutes or less, and the polishing rate in a steady state Can be 1.3 μm / min or more and less than 1.4 μm / min.

  Furthermore, since the polishing pad made of a polyphenylene sulfide resin foam is hydrophobic, the abrasive particles are adsorbed or reacted inside the cell when the polishing pad is reused after polishing. Alternatively, secondary particles are hardly formed and remain, and the reusability is excellent. In addition, since the polyphenylene sulfide resin has almost no decrease in elastic modulus due to water absorption, it is not necessary to polish and remove a layer having a decreased elastic modulus by reuse. The polishing pad of the present invention has a low water absorption rate, so there is almost no variation in surface quality due to water absorption on the polishing surface during polishing, and since it has a high elastic modulus and high rigidity, it can be used as a polishing pad without a cushion layer. it can.

  As described above, the polishing pad of the present invention can be used without a cushion layer, and the use of the polishing pad without a cushion layer is the greatest purpose, but it can also be used with a cushion layer provided. By disposing the cushion layer on the side opposite to the polishing surface of the resin foam, the pressure applied to the object to be processed is dispersed, and local polishing can be suppressed and more uniform polishing can be realized. Further, by providing the cushion layer, it is possible to stably perform the polishing with the resin foam and at the same time suppress the abrasion of the polishing surface while maintaining the polishing rate of the polishing pad. Here, as the cushion layer, it is desirable to use a material having a smaller compression elastic modulus than the resin foam of the present invention. The reason for this is that unless the compression modulus is smaller than that of the resin foam, the effect of relieving stress generated during polishing cannot be obtained.

  Here, the thickness of the cushion layer is preferably equal to or less than the thickness of the resin foam (polishing layer), and is preferably 10% to 50% of the total thickness of the cushion layer and the resin foam, preferably Is 10-40%. If the thickness of the cushion layer is less than 10%, the effect of adding the cushion layer cannot be sufficiently obtained. If the thickness of the cushion layer exceeds 50%, the cushion layer is too thick, and the resin foam The features of the invention of using can not be sufficiently obtained.

  As the cushion layer, it is desirable to use a resin having a compression modulus smaller than that of the resin foam of the present invention, and a polymer resin foam, rubber resin, photosensitive resin, or the like can be used. In addition to the above, non-woven fabrics such as non-woven fabrics such as polyester non-woven fabric, nylon non-woven fabric, acrylic non-woven fabric and polyester non-woven fabric impregnated with polyurethane can also be used.

It is a perspective view showing roughly the composition of the polisher with which the polishing pad concerning the embodiment of the present invention was attached. It is the electron microscope image which expanded a part of polishing pad of Drawing 1, (a) shows the surface by the side which polishes, and (b) shows the section near the surface. It is the electron microscope image which expanded a part of conventional suede-like polishing pad, (a) shows the surface by the side to polish, and (b) shows the section near the surface. It is a figure which shows the relationship between the grinding | polishing time and grinding | polishing speed in each polishing pad, (X) is a PPS hard resin foam polishing pad which is an example of this invention, (Y) is a hard urethane foam polishing pad, (Z) Shows a conventional suede-like hard urethane polishing pad. It is a fragmentary sectional view showing typically the polish pad of the present invention at the time of polish processing, (a) shows an initial state, and (b) shows a state after progress for a predetermined time. It is a fragmentary sectional view showing typically the conventional suede-like polishing pad at the time of polish processing, (a) shows an initial state, and (b) shows a state after progress for a predetermined period.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view schematically showing a configuration of a polishing machine to which a polishing pad according to an embodiment of the present invention is attached. The polishing pad of the present invention is used in a polishing machine that polishes a thin plate member (object to be processed) such as a glass plate for HDD, and is mounted, for example, on the upper and lower surface plates of a 3B polishing machine. In addition, the length, width, or thickness of each component in FIG. 1 shows an example, and the length, width, or thickness of each component in the polishing pad of the present invention is limited to that in FIG. Absent.

  Specifically, the polishing machine 10 includes a pair of disk-shaped surface plates 11 and 12 disposed substantially concentrically in the vertical direction, polishing pads 1 and 2 disposed on the inner surface of each surface plate, and the polishing There are provided four spur gears 13 (carriers) disposed on the upper surface of the pad at approximately 90 ° intervals, and external gears 14 disposed substantially at the center positions of the four spur gears and engaged with the spur gears. . Further, in the vicinity of the outer peripheral surfaces of the surface plates 11 and 12, an internal gear (not shown) that engages with each spur gear is provided. That is, the polishing machine has a planetary gear mechanism in which four spur gears 13 revolve around the shaft gear 14 while rotating.

  The surface plate 11 has a function as a mounting table for the object D, and the object D is mounted on the upper surface of the surface plate 11 via the polishing pad 1. The surface plate 12 has a function as a weight at the time of polishing, and is placed on four spur gears 13 after the workpiece D is placed in each through-hole described later. The surface plate 12 is provided with a plurality of slurry holes 12a for supplying the polishing liquid to each object to be processed at the time of polishing, and the polishing liquid is supplied from a pipe 15 disposed above the surface plate 12. A is supplied. As the polishing liquid used in the present invention, for example, a slurry containing abrasive grains such as cerium oxide particles having a primary particle diameter of 0.5 μm to 1.0 μm can be preferably used. It is desirable to use a slurry of 1.0 μm or less, preferably 0.8 μm or less. In addition to the above, as the polishing slurry, alumina-based slurry, zirconia-based slurry, and colloidal silica-based slurry can be used. In particular, when polishing the workpiece D of hard material, in addition to cerium oxide, an alumina-based slurry or a zirconia-based slurry is often used. For example, a slurry containing abrasive grains as finer abrasive particles such as colloidal silica can be used. In the present invention, for example, a cerium oxide abrasive manufactured by Mitsui Kinzoku Co., Ltd. can be used.

  The spur gear 13 is provided with a plurality of through holes 13a. During polishing, the lower opening of the through hole 13a is closed by the polishing pad 1, and the upper opening of the through hole 13a is closed by the polishing pad 2. Further, the object to be processed D is held in the through hole 13a in a state of being in pressure contact with the polishing pads 1 and 2.

  In the polishing process using this polishing machine, first, a plurality of spur gears 13 are placed on the polishing pad 1, and the object D is placed in the through hole 13a of each spur gear. Thereafter, the surface plate 12 is placed so that the polishing pad 2 is positioned on the lower surface, and the object to be processed D is held in the through hole 13a. Thereby, the resin foam of the polishing pad 1 and the to-be-processed object D are press-contacted. Then, the polishing liquid A is supplied from above through the slurry hole 12a, then the external gear 14 is rotated, and the surface plate 11 is rotated clockwise and the surface plate 12 is rotated counterclockwise by a gear mechanism (not shown). Rotate. The spur gear 13 itself rotates as the spur gear 13 revolves clockwise around the external gear 14 by the rotation of the external gear 14. As a result, friction is generated between the upper surface of the polishing pad 1 and the lower surface of the object D, and friction is generated between the lower surface of the polishing pad 2 and the upper surface of the object D. The lower surface is polished simultaneously. After a predetermined time has elapsed from the start of polishing, the rotation of the external gear 14 is stopped, the object to be processed is taken out, and the polishing is completed. Thereafter, a new object D is placed and the same operation as described above is repeated.

  Here, in order to perform uniform and good polishing processing in the production process of the object to be processed, it is necessary to use a polishing pad that can continuously realize good polishing satisfying certain quality conditions. In particular, since both the polishing pads 1 and 2 are in pressure contact with the workpiece D in the polishing process, good polishing is continuously performed under a predetermined pressure from the start of polishing to the pad replacement timing. There is a need for a polishing pad that can be realized.

  2A and 2B are enlarged scanning electron microscope images of a part of the polishing pad 1 of the present invention. FIG. 2A is a surface on the side to be polished (× 200 times), and FIG. ). FIG. 3 is an enlarged electron microscope image of a part of a conventional suede-like polishing pad. (A) is a surface on the polishing side (× 200 times), and (b) is a cross section near the surface (× 500). Times).

  As shown in FIGS. 2 (a) and 2 (b), the polishing pads 1 and 2 of the present invention are composed of a plurality of cells (closed cells) and cell walls (resin portions formed between closed cells). It has a resin foam. This hard resin foam has a three-dimensional cell structure constituted by a cell wall so that a plurality of cells and these cells have mutually independent partitions, and is made of a thermoplastic resin. In the polishing pads 1 and 2, the wall portion of the cell wall satisfies predetermined tensile elastic modulus and bending elastic modulus, and has a predetermined size, an average cell diameter of 4 μm to 50 μm, and an average cell wall thickness Is a structure of 1 μm to 5 μm, and the ratio of the average cell diameter to the average cell wall thickness is in the range of 4 to 10. When the average cell diameter is smaller than 4 μm, the number of abrasive grains held in the cell is reduced, the polishing rate is lowered and a stable polished surface cannot be obtained. When the average cell diameter exceeds 50 μm, the strength of the cell wall is increased. Insufficient and stable surface quality cannot be obtained, and the surface quality deteriorates. At the same time, a large amount of abrasive particles accumulate in the cell and secondary particles are generated, and surface defects such as scratches are likely to occur. The average cell diameter is preferably 4 μm to 40 μm. By setting the average cell diameter in this range, the cell structure is further optimized, so that the polishing start-up property can be improved and the steady-state polishing rate can be increased. If the ratio of the average cell diameter to the average cell wall thickness is less than 4, the number of abrasive grains as abrasive particles held inside the cell decreases, the polishing rate decreases, and a stable polished surface cannot be obtained. If it exceeds 1, the strength of the cell wall is insufficient, and a stable polishing state cannot be obtained, resulting in a reduction in the polishing rate.

  Preferably, as the hard resin foam, a sheet foam made of hard resin such as polyphenylene sulfide resin (PPS resin), polyethylene terephthalate (PET resin), polycarbonate resin (PC resin) can be suitably used. Hereinafter, polyphenylene sulfide resin, polyethylene terephthalate resin, and polycarbonate resin are referred to as PPS resin, PET resin, and PC resin, respectively. Here, the tensile strength of these resins is 50 MPa to 90 MPa, the bending strength is 90 MPa to 140 MPa, and the tensile elastic modulus and the bending elastic modulus are both 2400 MPa or more. Since the mechanical property value of the hard resin foam of the present invention does not change before and after foam molding, the tensile strength, bending strength, tensile elastic modulus, bending elastic modulus indicating the mechanical properties of the structure after foaming. Such values are not significantly changed from the value of the resin before foaming, and are presumed to be the same as before foam molding. In other words, when the mechanical characteristic values of the resin before foam molding correspond to, for example, high strength and high rigidity, the same machine is used even in the microstructure such as the cell wall in the structure after foaming of the resin. Characteristic value. Similarly, in the conventional hard urethane foam structure, the tensile elastic modulus, which is the mechanical property value of the microstructure such as the cell wall in the foam structure, is almost the same as that of the hard urethane resin before foaming. It is thought that it has a rate. Therefore, for example, when the tensile elastic modulus of the cell wall of the PPS resin foam is compared with the tensile elastic modulus of the cell wall of the hard urethane pad, the tensile elastic modulus of the cell wall of the PPS resin foam is the tensile elastic modulus of the hard urethane pad. Will be more expensive. Therefore, if both of them are foamed at the same expansion ratio and the hard resin foam constituting the PPS resin foam and the hard urethane pad have the same three-dimensional cell structure, stress is applied to the PPS resin foam from the outside. When applied, the PPS resin foam can provide a cell structure with less deformation compared to a hard urethane foam.

  Therefore, by using the hard resin foam of the present invention, by designing the average cell diameter and the average cell wall thickness, and the ratio of the average cell diameter to the average cell wall thickness within a predetermined range, the predetermined cell diameter , A hard resin foam having a preferable cell wall thickness and a preferable three-dimensional cell structure in which the ratio of the average cell diameter to the average cell wall thickness is within a predetermined range, and having good polishing characteristics A polishing pad made of a foam can be obtained.

In the present invention, reducing the deformation of the three-dimensional cell structure during polishing secures the polishing stability of the hard resin foam. Therefore, the mechanical characteristic value of the polishing pad used in the present invention is reduced. Of these, particularly important are the tensile modulus and the flexural modulus, but it is desirable to increase the tensile strength and the bending strength in order to make the material difficult to plastically deform.
The hard resin foam constituting the polishing pad of the present invention has a tensile strength as a value representing the mechanical properties of the wall portion of the cell wall constituting the three-dimensional cell structure by the mechanical properties of the resin sheet material before foaming. Of 50 MPa to 90 MPa, a bending strength of 90 MPa to 140 MPa, and a tensile elastic modulus and a bending elastic modulus of 2400 MPa or more must be satisfied. Preferably, the tensile strength is 70 MPa to 90 MPa, and the bending strength is 120 MPa. The tensile modulus and the flexural modulus both satisfy 3,000 MPa to 4200 MPa at ˜140 MPa.

  Here, the reason why the bending strength and the bending elastic modulus are important in addition to the tensile strength and the tensile elastic modulus in the present invention will be considered. The three-dimensional cell structure of the polishing pad is subjected to stress in the vertical direction from the upper surface plate to the lower surface plate during polishing. At this time, the three-dimensional cell structure constitutes a three-dimensionally complex continuous body. Therefore, there is no cell wall that is completely perpendicular to the upper surface (or lower surface) of the surface plate. That is, in each cell, there is a cell wall in which components in various directions are mixed with respect to the main surface of the polishing pad, and any cell wall receives a compressive load from the surface plate to each cell. Tensile strain and bending strain occur. In addition, the frictional force received from the object to be processed (the material to be cut) of the polishing apparatus acts on the tip of the cell structure, that is, the end of the cell wall at the polishing surface position. Bending distortion due to. Therefore, in the present invention, by increasing the bending strength and bending elastic modulus of the polishing pad, it is possible to suppress the occurrence of bending distortion, and as a result, a stable polishing state can be obtained. In order to prevent microscopic stress concentration on the cell wall, it is necessary to increase both the lower limit value of the tensile modulus and the lower limit value of the flexural modulus.

The material of the foam in the present invention is not limited as long as it is a hard resin foam made of a thermoplastic resin capable of forming the above three-dimensional structure, but the viewpoint of stability, ease of molding, and reusability of the three-dimensional cell structure. Therefore, as described above, the PPS resin is preferably used.
Moreover, chemical resistance and heat resistance can be improved by using PPS resin. The reason why the PPS resin is particularly preferably used is that the structure has high rigidity and low water absorption. Particularly, since the water absorption is low, abrasive grains as abrasive particles adhere to the cell wall surface inside the cell. It is difficult to form secondary particles. Further, the polishing pad made of PPS resin has extremely low water absorption, so that there is almost no decrease in elastic modulus due to water absorption. Therefore, when polishing is performed again after one end polishing, the secondary particles remaining inside the cell of the hard resin foam can be reused without being removed, and the layer having a reduced elastic modulus is removed. Therefore, it can be reused without performing preliminary polishing such as dressing. The water absorption may not be equal to that of the PPS resin, and may be a hard foam made of a thermoplastic resin capable of forming the three-dimensional structure of the present invention, and if the water absorption is 0.02 to 0.20%. The polishing pad is reusable, but preferably has a water absorption of 0.02 to 0.10%.

  Moreover, in this embodiment, the polishing pads 1 and 2 are comprised with the resin foam, and the cushion layer is not provided in either of these polishing pads. As described above, the polishing pads 1 and 2 are made of a hard urethane foam structure, and can be used without a cushion layer, thereby enabling high-speed polishing. Moreover, a polishing pad may be comprised by the resin foam and the cushion layer arrange | positioned on the opposite side to the grinding | polishing surface of this resin foam. By providing a cushion layer on the resin foam, the pressure applied to the object to be processed D is dispersed, local polishing can be suppressed, more uniform polishing can be realized, and the polishing rate of the polishing pad can be increased. It can be relaxed and the steady state can be maintained for a longer time, and the polishing pad can be used for a longer time.

  The polishing pads 1 and 2 of the present invention are manufactured, for example, by the following method. First, an unfoamed resin molded body having predetermined characteristics is prepared. Then, the compact is sealed in a high-pressure container, an inert gas is injected into the high-pressure container, and the inert gas is allowed to permeate the compact under pressure. Examples of the inert gas include nitrogen, oxygen, carbon dioxide, argon, hydrogen, methane, and chlorofluorocarbon-based gases. In particular, considering the permeability (penetration time, solubility) to the unfoamed resin sheet material, carbon dioxide is used. It is preferable to use it.

  Next, after releasing the pressure in the pressure vessel, the molded body (resin sheet material) is heated and foamed, and the molded body is further cooled to obtain a resin foam. Details regarding these steps will be described later.

  The object D to be polished by the polishing pads 1 and 2 is made of a hard member, such as a hard disk drive glass plate, silicon wafer, liquid crystal glass, sapphire substrate, compound semiconductor, GaN substrate, and SiC substrate. The polishing pad of the present invention can be suitably used for such a hard member.

<Relationship between polishing time and polishing speed>
(Steady state polishing rate)
FIG. 4 shows a polishing time and a polishing rate when a polishing pad corresponding to Example 2, Comparative Example 5 and Comparative Example 7, which will be described later, is polished using a polishing machine 10 as a representative example of the present invention. It is a graph which shows the relationship. In the figure, the graph with the highest polishing rate in the steady state shows a hard resin foam polishing pad (solid line X in the drawing) made of a material corresponding to Example 2 (Table 1) described later in the present invention, and the polishing rate in the steady state. Is a medium urethane value, a hard urethane foam polishing pad made of hard urethane corresponding to Comparative Example 7 (Table 2) described later (dotted line Y in the figure), the graph with the smallest polishing rate in the steady state, A conventional suede-like soft urethane polishing pad (dotted line Z in the figure) made of a material corresponding to Comparative Example 5 (Table 2) described later is shown. In the test, the polishing rate was measured under the same conditions for all materials except that different polishing pads were used. As shown in FIG. 4, in the steady state of polishing, it can be seen that the polishing rate of the hard resin foam polishing pad of the present invention is the highest, and then the hard urethane foam polishing pad and the suede-like soft urethane polishing pad increase in this order. .

(Relationship between polishing speed and steady-state speed after 15 minutes from the start of polishing)
When the hard resin foam polishing pad corresponding to Example 2 was used, the polishing rate was about 1.30 μm / min in 15 minutes after the start of polishing, and then approximately 1.35 μm / min until the polishing time passed 17 hours. Min is maintained. Although not particularly shown, the polishing pads corresponding to the other examples exhibited the same behavior as that of the example 2 equivalent. On the other hand, when a conventional suede-like soft urethane polishing pad equivalent to Comparative Example 5 is used, the polishing rate at about 15 μm / min especially after the start of polishing is about 0.6 μm / min, compared with the case where the polishing pad of the present invention is used. There is a big difference. Further, in the case where the hard urethane foam polishing pad corresponding to Comparative Example 7 was used, the polishing rate at 15 minutes after the start of polishing was 0.8 μm / min, compared with the case where the suede-like soft urethane polishing pad was used. It can be seen that the rising rate of the polishing rate in 15 minutes after the start of polishing is excellent, but the rising rate of the polishing rate is inferior to that of the hard resin foam polishing pad corresponding to Example 2 of the present invention.

(Polishing of polishing at the initial stage of polishing)
Focusing on the rising property of the polishing rate in the initial stage of each material, the hard resin foam polishing pad of the present invention (Example 2) has a polishing rate of about 1 in only 15 minutes (0.25 hours) after the start of polishing. 30 μm / min, and then 1.35 μm / min until 30 minutes (solid line X in the figure). Further, the above polishing rate is substantially maintained until 4 hours have elapsed from the start of polishing.

Next, when the hard resin foam polishing pad of the present invention is compared with the hard urethane foam polishing pad of Comparative Example 7, the hard urethane foam polishing pad has a polishing rate immediately after the start of polishing and a steady state polishing rate. Both showed the intermediate | middle behavior of the hard resin foam polishing pad of this invention, and a suede-like soft urethane polishing pad (the dashed-dotted line Y in a figure). That is, in the hard urethane foam polishing pad, it takes about 1 hour from the rising to the steady state, and the polishing rate in the steady state is 1,25 μm / min. It can be seen that both the polishing rate immediately after the start of polishing and the steady state polishing start rate are slightly lower than those of the pad. On the other hand, with the conventional suede-like soft urethane polishing pad of Comparative Example 5, the polishing rate was not stable even after 0.25 hours had elapsed from the start of polishing (dotted line Z in the figure). In addition, after about 2 hours from the start of polishing, the polishing rate was about 1.10 μm / min, and then the polishing rate was almost the same 1.10 μm / min, and the steady-state polishing rate remained constant. . The time required from the start of polishing until the polishing rate becomes constant is 15 minutes (0.25 hour) in the present invention, whereas it is 2 hours in the suede-like soft urethane polishing pad, and the time difference is 1 .75 hours, there is a big difference of 8 times in terms of ratio.
Therefore, when the hard resin foam polishing pad of the present invention is used, the polishing rate can be sharply increased in the initial stage of the polishing process, and a polishing rate that reaches a steady state can be obtained in a relatively short time from the start of polishing. It can be seen that the period during which the polishing rate is constant can be obtained longer. As a result, it can be seen that preliminary polishing can be reduced and stable polishing can be realized.

  The schematic diagram explaining the microstructure of the polishing pad which consists of a hard resin foam of this invention is shown.

  FIG. 5 is a partial cross-sectional view schematically showing a polishing pad during the polishing process of the present invention, where (a) shows an initial state and (b) shows a state after a predetermined time has elapsed. FIG. 6 is a partial cross-sectional view schematically showing a conventional polishing pad, where (a) shows an initial state and (b) shows a state after a predetermined time has elapsed.

  As shown in FIG. 5A, the polishing pad 1 of the present invention includes a plurality of minute cells 61 and cell walls 62 formed between adjacent minute cells 61, 61. Although the structures are different and do not necessarily have a fixed shape, the cell walls 62 are three-dimensionally continuous so that the cell walls directed in a random direction with respect to the main surface of the polishing pad 1 surround each cell. The formed structure is formed.

  In this three-dimensional structure, each cell is surrounded by a cell wall 62, and the cell wall 62 is a three-dimensional continuous structure that continuously forms a network. By forming such a three-dimensional cell structure, there is an effect of dispersing stress. In the three-dimensional cell structure of the present invention, the material forming the structure uses a high-strength and high-rigidity resin, the average cell diameter and the average cell wall thickness each satisfy a predetermined value, and the average cell diameter Since the ratio to the average cell wall thickness satisfies a predetermined range, the structure is excellent in rigidity. Therefore, it is presumed that, under a predetermined pressure, moderate elasticity can be exhibited from the initial stage of polishing and good polishing can be realized.

  Further, a plurality of end faces 63 a of the cell wall 62 are exposed on the upper surface of the polishing pad 1, and these end faces form the polishing surface 1 a of the polishing pad 1. When polishing using a foam, it is necessary to have a cell wall end surface having an action of cutting the surface of the workpiece D. In the present invention, the polishing surface of the foam having a dense three-dimensional structure is used. 1a has an end face 63a of the cell wall 62 having an average cell diameter of 4 μm to 50 μm and an average cell wall thickness of 1 μm to 5 μm (FIG. 2A). Therefore, it is presumed that there are many continuous structures of the cell wall 62 supported on the end surface 63a of the cell wall 62 on the polishing surface 1a, and thereby high-definition cutting can be realized on the polishing surface 1a. Further, by setting the average cell diameter to 4 μm to 50 μm, a large amount of slurry containing abrasive grains M having an average primary particle size of about 1 μm can be held in the minute cells 61 on the polishing surface 1a, thereby increasing the polishing rate. It is assumed that it can be made. The average particle diameter of the abrasive grains M is preferably 1 μm or less, for example, abrasive grains having an average particle diameter of 0.6 to 0.8 μm.

Here, the ratio of the average cell diameter to the average cell wall thickness needs to satisfy the range of 4-10.
If this ratio is less than 4, the primary particles in the slurry in the cell is insufficient and the polishing rate is not stable, and if the ratio exceeds 10, the cell diameter becomes too large and the strength of the cell is insufficient. During the polishing, the microcells 61 are deformed and stable polishing cannot be performed, or secondary particles of abrasive grains are easily formed in the microcells 61. For this reason, the ratio of the average cell diameter to the average cell wall thickness is in the range of 4-10. Furthermore, this ratio is more preferably in the range of 4-8. By setting the ratio of the average cell diameter to the average cell wall thickness within this range, as will be described later, the polishing start-up property and the steady-state polishing rate become more excellent.

  In addition, when a predetermined pressure is applied to the polishing surface 1a via the workpiece D during the polishing process, the pressure is distributed almost uniformly on the cell wall 62 via the end surface 63a of the cell wall, and within the polishing pad 1 A substantially uniform compressive stress is generated in the plane direction. As a result, more uniform polishing in the planar direction of the polishing pad 1 is possible, and it is presumed that the non-polished surface of the non-processed body D hardly causes uneven polishing in the planar direction, and a good flat surface can be obtained. In addition, the polishing pad made of the highly rigid thermoplastic foam of the present invention has not only a tensile elastic modulus but also a flexural modulus higher than that of a hard urethane polishing pad or the like. 62 can reduce both the bending deformation caused by the polishing load and the bending deformation caused by the friction force of the polishing machine at the cell wall end on the polishing surface side, and the cell structure of the foam can be obtained even when polishing at high polishing pressure and high rotation speed. stable. For this reason, the polished surface has high finishing accuracy and can maintain a stable polishing state.

  FIG. 5B shows a cross-section of the pad that has been reduced by a predetermined thickness due to abrasion of the polishing pad 1 after a predetermined time has elapsed since the start of polishing. At this time, end surfaces 63 a ′ of a plurality of different cell walls 62 ′ are exposed on the newly exposed upper surface of the polishing pad 1, and these end surfaces form the polishing surface 1 a ′ of the polishing pad 1. Since the three-dimensional cell structure of the polishing pad 1 is substantially constant in the thickness direction of the foam regardless of the position in the thickness direction, the three-dimensional cell in the vicinity of the top surface of the foam after a predetermined time has elapsed since the start of polishing. The structure is also substantially constant and has a three-dimensional cell structure that is substantially the same as the initial state shown in FIG. 5A except that the thickness is reduced. When both the thickness and the ratio of the average cell diameter to the average cell wall thickness satisfy a predetermined value within a predetermined range, a dense and uniform cell structure can be secured. Therefore, it is considered that the same high rigidity as in the initial state is maintained. Further, in a plan view of the polishing surface 1a ′, the state of the end surface 63a ′ of the cell wall 62 ′ is almost the same as the initial stage when the end surface is viewed as a whole, and it is assumed that a good polishing rate can be maintained. The Accordingly, the polishing pad 1 has substantially the same polishing rate after a predetermined time as the initial state, and a good polishing rate can be realized from the initial stage.

  On the other hand, in the partial cross-sectional view of FIG. 6A, the suede-like polishing pad 100 is composed of a flange 101 and a gap 102 formed between the adjacent flanges 101, 101. Since the flange 101 extends substantially perpendicular to the main surface of the polishing pad 100, the rigidity in the direction parallel to the main surface of the polishing pad 100 (lateral direction) is relatively low. Therefore, when a predetermined pressure is applied to the polishing surface 100a via the workpiece D in the initial stage of the polishing process, the ridge 101 is flexed by the pressure, and the end surface 101a of the ridge 101 is The friction with the lower surface slightly swings in the lateral direction, and the pressure perpendicular to the polishing surface applied to the polishing surface 100a decreases. This is presumed to reduce the initial polishing rate. That is, in the suede-shaped polishing pad shown in FIG. 6A, the pressure applied during polishing is easily absorbed by deformation of the pad itself, and it is difficult to increase the polishing rate. In addition, after a predetermined time has elapsed since the start of polishing, the polishing rate increases and maintains a substantially constant value. This is because, as shown in FIG. This is presumed to be due to the fact that the rigidity is gradually increased and the amount of swinging is relatively reduced by shortening the length. Furthermore, in the case of a suede-like polishing pad, since the space in which abrasive grains M as abrasive particles are accumulated is large, a predetermined amount of abrasive grains M in the slurry is stably accumulated between adjacent walls, It is presumed that it takes time to perform steady polishing by supplying abrasive grains M as polishing particles according to the supply amount supplied to the polishing surface in a substantially constant state by the pressing force during polishing. . Here, when the suede-like polishing pad is polished once and reused, the amount and size of particles in the slurry remaining between the adjacent walls 101 and 101 are not constant, or 2 Since the next particles are formed, preliminary polishing is required again.

  As described above, according to the present embodiment, the polishing pad 1 is configured by being partitioned by the cell walls 62 such that the plurality of micro cells 61 and these micro cells 61 have independent partitions. Further, it has a resin foam made of a thermoplastic resin having a three-dimensional cell structure. Then, the tensile strength is 50 MPa to 90 MPa, the bending strength is a value representing the mechanical characteristics of the wall portion of the cell wall constituting the three-dimensional cell structure of the resin foam as the mechanical characteristics of the resin sheet material before foaming. The tensile modulus and the flexural modulus are both 2400 MPa or more. Further, the average cell diameter of the hard resin foam is 4 μm to 50 μm, the average thickness of the cell wall 62 is 1 μm to 5 μm, and a highly rigid structure is formed in the vicinity and inside of the polishing surface. Can be stably held inside the cell structure, and a large number of high-strength, high-rigidity cell wall end faces 62a are present on the polished surface, thereby providing an auxiliary cutting action. Therefore, an excellent polishing rate can be realized from the polishing start stage. Therefore, it is possible to realize simple polishing by eliminating the time for preliminary polishing or shortening it as much as possible, and by performing continuous polishing at an excellent polishing rate from the initial stage, efficient and reliable polishing. Can be realized.

  Furthermore, since the ratio of the average cell diameter to the average cell wall thickness of the cells 61 on the polishing surface 1a of the resin foam is in the range of 4 to 10, the cell structure has high rigidity and can stably hold the abrasive particles. Therefore, high-definition polishing can be realized.

In particular, if the resin foam is molded from any of high-rigidity PPS resin, PET resin, or PC resin with high tensile strength, flexural strength, tensile modulus, and flexural modulus, better polishing from the initial stage It is possible to obtain characteristics, and it is possible to easily manufacture a dense hard resin foam having the cells 61 having the above dimensions, the cell walls 62 having the above dimensions, and the number of cells per unit area.
Further, since the strength and tensile modulus of the cell wall of the resin foam are high, the stability of the three-dimensional cell structure formed by the cell wall of the foam during polishing is high, and the bending elastic modulus is high. Since the amount of bending strain related to the cell wall at the polishing surface position at the tip of the cell structure is small, a stable polishing state can be obtained.

  More specifically, the friction force of the polishing machine is applied to the cell wall end on the polishing surface side of the resin foam at the interface between the open cell wall end on the polishing surface side of the foam and the workpiece (work material). As a result, the amount of bending deformation of the cell wall end portion is small, and a stable polished state can be obtained.

  Although the polishing pad and the polishing method according to this embodiment have been described above, the present invention is not limited to the described embodiment, and various modifications and changes can be made based on the technical idea of the present invention.

  The present invention will be described in detail based on the following examples. In addition, this invention is not limited to the Example shown below.

(Examples and comparative examples)
First, an unfoamed resin molded body described later was prepared, and this molded body was sealed in a high-pressure container. Next, for example, an inert gas was injected into the high-pressure vessel, and carbon dioxide gas was infiltrated into the compact at a pressure of 60 kg / cm ^{2 for} 8 hours. Next, after releasing the pressure in the pressure vessel, the molded body was heated and foamed, and the molded body was further cooled to obtain a dense hard resin foam. In addition to the above, in order to obtain each example material and each comparative example material having different microstructures shown in Tables 1 and 2, the pressure during gas penetration, the holding time in the pressure vessel, the pressure after release By appropriately adjusting the holding temperature and the like, it is possible to obtain foams having cell structures with different microstructures in which the average of the average cell diameter (bubble size) and the average cell wall thickness is changed. In order to stabilize the cell diameter distribution, the heating temperature after releasing the pressure should be below the glass transition temperature for amorphous resins and below the crystallization temperature for each resin or not exceed the crystallization temperature for crystalline resins. It is desirable to mold the foam under various conditions. In addition, in order to obtain a foam having a large cell diameter by foaming, not only adjustment of the pressure at the time of gas penetration, the holding time in the pressure vessel, and the holding temperature after releasing the pressure, but also, for example, two-stage foaming, etc. It is desirable to perform molding. Thus, by performing foam molding a plurality of times, a foam having a cell diameter exceeding 40 μm to 50 μm can be obtained. Here, in the case of two-stage foaming, unlike the case of single-stage foaming, the foaming ratio can be increased by holding at a high temperature exceeding the crystallization temperature.

  Here, the polishing pads of Examples and Comparative Examples were sliced to a thickness of 0.6 mm and subjected to a polishing test. The suede type soft urethane pad shown in Comparative Example 5 was purchased from a commercially available urethane pad.

This hard resin foam was attached to the upper and lower surface plates of a 3B polishing machine (manufactured by Taisei Corporation, apparatus name “3B double-side polishing device”), and three carriers were fixed to the lower surface plate. Next, three discs having an area of 6.0 cm ² (3 cm × 2 cm) were prepared as processing test pieces, and one disc was placed in each carrier hole. After setting the upper surface plate on the lower surface plate, the slurry containing 10 wt% of the cerium oxide-based abrasive (trade name “MIREK (registered trademark) E05” manufactured by Mitsui Kinzoku Co., Ltd.) is supplied at 250 ml / min, The disc and the three carriers were rotated to polish the disc. One set of three disks was subjected to a sufficient polishing process, and then each disk was taken out and subjected to a polishing process for another set that had not been polished, and this operation was repeated thereafter. During the polishing treatment, the weight of the upper surface plate was 5700 gf, the pressure on the polishing surface was 317 g / cm ² , and the load applied per carrier was 1900 gf. The rotation speed of the lower surface plate was 60 rpm, the rotation speed of the upper surface plate was 20 rpm, the revolution speed of the carrier was 20 rpm, and the rotation speed was 10 rpm.

(Structural evaluation of cell structure foam)
The hard resin foam obtained as described above is subjected to image analysis, and for each material, an average cell diameter within a predetermined field of view at an arbitrary position and an average of cell wall thicknesses are measured, and (average cell diameter) / The ratio of (average cell wall thickness) was determined.

  In the present invention, the average cell diameter representing the average bubble size of the resin foam structure, the average thickness of the cell walls partitioning the bubbles, the ratio of the average cell diameter to the average cell wall thickness, unit area The number of cells per hit can be determined by observing the surface at an arbitrary position of the polishing layer, but these values in the present invention are average values of results obtained by measuring each of the five resin foam structures. It is what was used. In the present invention, the three-dimensional cell structure defined based on the cell diameter, the cell wall thickness, and the ratio thereof, and the mechanical property values of the three-dimensional cell structure are basic components. In order to ensure these, it is important that minute cells exist independently in the three-dimensional cell structure. Therefore, when these materials were confirmed by observing the structure of a three-dimensional cell structure, it was confirmed that the cell structure was basically composed of independent microcells.

  Except for the suede-like polishing pad of Comparative Example 5, the pads made of the hard resin foams of Examples and Comparative Examples were confirmed by a calculation method based on the ASTM D2856-94-C method. It was confirmed that

  As an evaluation of the cell structure, the average cell diameter and the average cell wall thickness were obtained by image processing of a structural photograph of the resin foam structure observed with a scanning electron microscope manufactured by JEOL.

  Here, the measurement of the bubble diameter is the maximum for each bubble by selecting only those that contain the outline of the cell of the bubble in the observation field, except for the case where the cell defect is present in the field of view. The diameter and the minimum diameter were determined, and the average value was determined for each material.

  In addition, the thickness of the cell wall consists of a part where two cells in the field of view are adjacent to form a cell wall, and a part where three to four cells are adjacent to form a cell wall. The cell wall thickness varies depending on these parts. However, from the viewpoint of the micro-strength as a structure, since the thickness of the cell wall in the portion where these two cells are adjacent is the thinnest and the strength is low, pay attention to the portion where the two cells are adjacent. It is considered important to evaluate the cell wall thickness by averaging. From this, in the field of view of the scanning electron micrograph at 200 times the polished surface, the average value of the cell wall thicknesses in the portion where two cells are adjacent to each other was taken as the cell wall thickness in the present invention. Specifically, the cell wall thickness of the central part in the longitudinal direction of the cell wall in the part where two cells are adjacent to each other was determined for all the target parts of all cells in the field of view and the average value was obtained. . In the present invention, in order to eliminate variation due to the observation field of view, five test pieces are cut out from the same foam of each material and observed, and the cell wall thickness where two cells are adjacent by the above method is obtained. The average cell wall thickness was obtained by enlarging the magnification to 500 times.

(Evaluation of mechanical properties of resin sheet)
The tensile strength, tensile elastic modulus, bending strength, and bending elastic modulus in Examples and Comparative Examples were determined by cutting out test pieces having a predetermined shape from each resin sheet before foaming and conducting a tensile test and a bending test. The tensile test was performed according to JIS K7161, and the bending test was performed based on JIS K7171. Here, since the material of the comparative example 5 purchased and used the commercially available soft urethane pad, the mechanical characteristic was not calculated | required.

<Evaluation of polishing test results>
(Measurement of initial polishing rate and steady-state polishing rate)
Here, the polishing rate is determined by measuring the weight of the glass plate before and after polishing with an analytical electronic balance (manufactured by A & D, apparatus name “Electronic Balance GR-202”), and using the density of each glass plate. Then, after calculating the amount of change in thickness before and after polishing, the value calculated using the value obtained by dividing the amount of change in thickness by the polishing time. It was speed.

(Evaluation of polishing rate in steady state)
Further, here, the polishing rate in the steady state is evaluated by the above method, and when the polishing rate is 1.3 μm / min or more and less than 1.4 μm / min, the pass is “」 ”, the polishing rate in the steady state is When the polishing rate was 1.2 μm / min or more and less than 1.3 μm / min, the test was “good”.

(Surface quality of the polished surface)
After polishing, the fine waviness of the polished surface was measured for 10 polished surfaces on the glass surface using a surface shape measuring device (manufactured by Phase Shift, device name “Optiflat”). For example, among hard materials that require surface polishing, the surface quality of a glass substrate for a storage medium with severe surface quality is required to have a microwaviness of 0.5 nm or less. Here, the minute undulation refers to an arithmetic average undulation Wa in a region of a wavelength of 1.5 to 5.0 mm on the main surface.

  Therefore, also in the present invention, a fine undulation of 0.5 nm or less was regarded as acceptable “◯”, and a fine wave exceeding 0.5 nm was regarded as unacceptable “x”.

(Measurement of surface defects such as scratches)
About the evaluation of a scratch, the following evaluation was performed with respect to five glass plates. In order to easily generate scratches, the polishing pressure was doubled and the slurry flow rate was reduced to 20%, and polishing was performed under severe conditions. Thereafter, the number of scratches having a size of 0.16 μm or more on the surface of the polished glass plate was measured using a measuring apparatus (manufactured by KLA-Tencor, apparatus name “Surfscan SP1”). In all the five glass plates, the number of scratches having a size of 0.16 μm or more was 10 or less per glass plate, and the result was “good”. Even if one of the five glass plates had more than 10 scratches with a size of 0.16 μm or more, a failure was indicated as “x”.

(Measurement of water absorption before foaming)
For the water absorption, a non-foamed resin block was prepared, a sample (resin sheet) having a thickness of 2 mm × (20 mm) sq was cut out from the block to obtain a test piece, and the sample was immersed in distilled water at 20 ° C. for 24 hours. From the weight change before and after immersion, the water absorption was calculated as follows.
Water absorption (%) = [(weight after immersion) − (weight before immersion) / (weight before immersion)] × 100.

(Measurement of bending elastic modulus before and after water supply and its decrease rate)
The change in flexural modulus due to water absorption was obtained by cutting out a material of 2 mm thickness x 1 mm width x 3 mm length from the above non-foamed resin block and using an Instron tabletop testing machine system. The flexural modulus was measured under the following conditions.

Here, the sample was immersed at 25 ° C. for 48 hours, and the bending elastic modulus before and after immersion was compared between the test piece subjected to immersion and the test piece not subjected to immersion. Here, the rate of change in flexural modulus before and after water absorption after immersion was determined by the following formula.
Decrease rate of flexural modulus (%) = [(flexural modulus before immersion−flexural modulus after immersion) / flexural modulus before immersion]
Here, the evaluation of the rate of decrease in the flexural modulus is almost no decrease in the flexural modulus or 10% or less is acceptable “「 ”, and the decrease in the flexural modulus is more than 10% and less than 20%. Those with a pass of “◯” and those with a decrease in flexural modulus of 20% or more were evaluated as “failed” with an “x”.

(Reusability of polishing pad)
The case where secondary particles are difficult to form during polishing and the pad surface can be washed and reused without re-polishing is acceptable. “Yes”, secondary particles are easily formed during polishing and the pad surface is dried and polished after use. In order to prevent agglomeration of the abrasive grains as particles, the pad was stored in running water, and in addition, in order to remove the layer of reduced bending rigidity due to water absorption, the case where it was used after re-polishing was rejected as “x”.

  Here, the resin foam constituting the polishing pads of Examples 1 to 7 is a PPS resin sheet (PPS (1)) having a tensile strength of 80 MPa, a tensile elastic modulus of 3300 MPa, a bending strength of 138 MPa, and a bending elastic modulus of 3900 MPa. Is obtained under different conditions to obtain a foam having the cell structure shown in Table 1, and the resin foam constituting the polishing pad of Example 8 has a tensile strength of 85 MPa, a tensile modulus of 3500 MPa, It was obtained by foaming another PPS resin (PPS (2)) having a bending strength of 138 MPa and a flexural modulus of 4100 MPa. The resin foam constituting the polishing pad of Example 9 has a tensile strength of 52 MPa, Example 1 was obtained by foaming a PET resin foam (PET (1)) having a tensile elastic modulus of 2800 MPa, a bending strength of 100 MPa, and a bending elastic modulus of 2400 MPa. The resin foam constituting the polishing pad of Example 11 is obtained by foaming a PET resin foam (PET (2)) having a tensile strength of 73 MPa, a tensile elastic modulus of 4100 MPa, a bending strength of 130 MPa, and a bending elastic modulus of 3100 MPa. The resin foam constituting the polishing pad of Example 12 was obtained by foaming a PC resin having a tensile strength of 62 MPa, a tensile elastic modulus of 2400 MPa, a bending strength of 92 MPa, and a bending elastic modulus of 2400 MPa. Compared with PPS resin and PET resin, it is a foam of PC resin that has a slightly lower strength and lower rigidity.

Table 1 shows the evaluation results of the examples.
From the results of Table 1, as shown in Example 1 to Example 12, the tensile strength of the wall portion of the cell wall constituting the three-dimensional continuous cell structure of the hard resin foam is 52 to 85 MPa, the bending strength. The tensile modulus and the flexural modulus are both 2400 MPa or more, the average cell diameter of the resin foam is 4.8 μm to 46 μm, the average cell wall thickness is 1.1 μm to 4.9 μm, the average When the polishing pad includes a ratio of the cell diameter and the average cell wall thickness in the range of 4.4 to 9.4, the polishing rate reaches a steady state in a relatively short time within 30 minutes from the start of polishing, It was found that the polishing speed rising characteristics were good.

  In addition, in the evaluation of the examples, in order to evaluate the superiority or inferiority of each characteristic between the inventive materials, the test result between the materials is evaluated for each characteristic. It was confirmed whether there were inferior characteristics and test results.

<Evaluation test results of examples>
(Polishing of polishing)
In the case of Examples 10 and 11 which are PPS resin and PET resin of Examples 1 to 8, both rise times at the time of initial polishing were 25 minutes or less. In the case of the PC resin of Example 12, the strength and rigidity are inferior to those of the materials of Example 1 to Example 8, so that the rising time of polishing was 26 minutes and 30 minutes, both exceeding 25 minutes, but 30 minutes or less. It was. As described above, the materials of Examples 1 to 12 of the present invention are excellent in the polishing start-up property as compared with the comparative examples described later, although there is a slight difference in the polishing start-up property between the materials. As a result. Here, in the range of Example 1 to Example 7 in which the material before foaming is the same material (PPS (1)), the ratio of the average cell diameter to the average cell wall thickness exceeds 8 and the average The rise time at the initial polishing in Example 4 in which the cell diameter exceeds 40 μm and the ratio of the average cell diameter to the average cell wall thickness exceeds 8 is set to 20 minutes or less at the initial polishing in the other examples. On the other hand, it exceeded 20 minutes, and Examples 3 and 4 resulted in slightly inferior start-up properties during initial polishing. Therefore, it is considered that the average cell diameter is preferably in the range of 4 to 40 μm, and the ratio of the average cell diameter to the average cell wall thickness is preferably in the range of 4 to 8.

(Steady state polishing rate)
In addition, the steady-state polishing rate of the PPS resin of Examples 1 to 8 and the PET resins of Example 10 and Example 11 is 1.30 μm / min to 1 in the steady-state polishing rate. In the range of .4 μm / min, the evaluation is acceptable “◎”, and the steady-state polishing rates of Example 9 and Example 12 are 1.25 μm / min and 1.22 μm / min. This is an evaluation. In Examples 9 and 12, the steady-state polishing rate was slightly inferior to the other examples.

  Here, among Examples 1 to 8, Example 8 has a large steady-state polishing rate, and the material before foaming excluding Example 8 is the same material (PPS (1)). In Example 1 to Example 7, the ratio of the average cell diameter to the average cell wall thickness is more than 8, and the average cell diameter is more than 40 μm and the ratio of the average cell diameter to the average cell wall thickness is also The steady-state polishing rates of Example 4 exceeding 8 are 1.32 μm / min and 1.30 μm / min and less than 1.35 μm / min, respectively, and the steady-state polishing rates of Examples 3 and 4 are other Compared to Example materials 1, 2, 5, 6, and 7 in FIG. This reason is considered to be caused by the holding ability of the abrasive grains due to the strength of the cell wall. In addition, there is no significant difference in the steady-state polishing rate between the other examples, and the behavior of the polishing rate in the steady state in Examples 1 to 7 has the same tendency as the rising rate of the polishing rate. Is recognized.

(Surface quality and surface defects)
Regarding the surface quality of the polished surface of the example material, in Examples 1 to 12, the state of micro undulation on the surface satisfies 0.5 nm or less, and a uniform polished surface is obtained. The reason for this is considered to be due to the high stability of the microcell structure, although the materials of Examples 1 to 12 have high rigidity such as tensile elastic modulus and bending elastic modulus. In particular, it is considered that the PPS resins shown in Examples 1 to 8 have high tensile elastic modulus and flexural elastic modulus of the resin material, and the highest stability of the three-dimensional cell structure at the time of polishing. Further, since the PPS resin has a remarkably low water absorption rate, the variation in flatness due to water absorption on the pad surface during polishing is small, which is considered to improve the surface quality of the polished surface.

  Also, regarding the presence or absence of scratches on the polished surface, the materials of Examples 1 to 12 do not contain a hard reinforcing material like the glass fiber reinforced resin shown in Comparative Example 8, so that the base resin and the reinforcing material There was little occurrence of scratches.

(Decrease in flexural modulus due to water absorption)
Regarding the decrease in the flexural modulus due to water absorption in the immersion test at 25 ° C. for 48 hours, in the case of the PPS resin and the PET resin of the materials of Examples 1 to 11, there is almost no decrease in the flexural modulus and a decrease is recognized. In some cases, it is 10% or less. On the other hand, in the case of the PC resin of Example 12, a decrease in the flexural modulus in the range of more than 10% and less than 20% was observed, but in the case of the PC resin, compared to the case of the hard urethane pad, The amount of decrease in flexural modulus is small, and the flexural modulus exceeds 1920 MPa even after water absorption when the flexural modulus is decreased. Here, since the bending elastic modulus of the hard urethane pad is 1200 MPa, the pad made of the resin foam of the present invention has a lower bending elastic modulus due to water absorption than the bending elastic modulus of the hard urethane pad before water absorption. Even maintaining a high elastic modulus. Therefore, it has sufficient rigidity at the time of reuse, and pre-polishing for dressing was not required.

(Reusability of polishing pad)
Since the materials of Examples 1 to 12 have low water absorption, when repolishing after interrupting polishing once, it is only necessary to wash the pad surface with water, and polishing is performed by the surface tension accompanying drying of the cell surface. Secondary particles in which abrasive grains as particles are aggregated are difficult to be adsorbed on the inner wall of the cell. Although the PET resin of Examples 9 to 11 and the PC resin of Example 12 have higher water absorption than those of the PPS resins of Examples 1 to 7 and 8, the particles are aggregated to form secondary particles. Even when the secondary particles were adsorbed on the cell walls, the secondary particles could be removed only by washing with water. In addition, the tendency for a secondary particle to be hard to form in order of PPS resin, PET resin, and PC resin was recognized. When both the ease of forming secondary particles and the adsorption of secondary particles are combined, it is considered that the PPS resin is most excellent in reusability.

  Table 2 shows the evaluation results of the comparative examples.

  Comparative Examples 1 to 4 are pads obtained by foaming the same resin sheet (PPS (1)) as the materials of Examples 1 to 7, but the structure of the PPS resin foam is within the scope of the present invention. Outside. Specifically, in Comparative Example 1, the average cell diameter and the average cell wall thickness exceed the upper limit of the specified range of the present invention. In Comparative Example 2, the average cell diameter and the ratio of the average cell diameter to the average cell wall thickness are smaller than the lower limit value of the specified range of the present invention. In Comparative Example 3, the average cell diameter and the average cell wall thickness satisfy the range of the present invention, but the ratio of the average cell diameter to the average cell wall thickness exceeds the upper limit of the specified range of the present invention. In Comparative Example 4, the average cell diameter satisfies the range of the present invention, but the average cell wall thickness is larger than the upper limit value of the specified range of the present invention, and the ratio of the average cell diameter to the average cell wall thickness is the present invention. It is smaller than the lower limit of the specified range. Comparative Example 5 is a soft urethane suede-like polishing pad (soft PUR), and Comparative Examples 6 and 7 are pads obtained by foaming thermoplastic hard urethane with changed mechanical properties such as strength and elastic modulus (hard PUR ( 1), (2)), and Comparative Example 8 are pads (30 mass% GF-containing PPS) obtained by foaming a glass fiber reinforced hard PPS resin obtained by adding 30 mass% of glass fiber to PPS resin.

  And in the PPS resin foam of Comparative Example 1, the size of the average cell diameter exceeds the range of the present invention, and in the PPS resin foam of Comparative Example 3, the ratio of the average cell diameter to the average cell wall thickness is remarkably large. Since both are outside the scope of the present invention, the polishing start-up property and the steady-state polishing rate are acceptable, but the cell structure lacks rigidity and is excellent in reusability, but the surface of the polishing surface Due to the low quality, it was out of the scope of the present invention. In particular, in the case of Comparative Example 1 having a large average cell diameter of 60 μm, secondary particles were generated in the minute cells, and scratches that were surface defects occurred due to the influence of peeling of the secondary particles.

  In Comparative Example 2, the average cell diameter is smaller than the lower limit of the present invention, and the average cell wall thickness satisfies the scope of the present invention, but the ratio of the average cell diameter and the average cell wall thickness is outside the scope of the present invention. Since the number of abrasive grains that can be held in the cell is small, the rising property of polishing was low, and a polished surface with good surface quality could not be obtained.

  Although the average cell diameter of the PPS resin material of Comparative Example 4 satisfies the range of the present invention, the average cell wall thickness exceeds the range of the present invention, and the ratio of the average cell diameter to the average cell wall thickness is within the range of the present invention. Below. Moreover, since the number of abrasive grains that can be stably held inside the cell is reduced as a whole polishing surface, the supply amount of abrasive on the polishing surface is insufficient, the rising characteristics of the polishing rate, and the steady-state polishing rate are inferior . Further, although there is no decrease in the flexural modulus due to water absorption and excellent reusability, the surface quality of the polished surface is low and a stable polished surface cannot be obtained, which is outside the scope of the present invention.

  Further, in Comparative Example 5, the material is a suede polishing pad made of a soft urethane resin, the polishing rate in the initial stage is greatly reduced to about 1/2 of the polishing rate in the steady state, and the rising characteristic of the polishing rate is inferior. It was. Moreover, the arrival time to the steady state was as long as 2 hours, and the polishing rate in the steady state was inferior to other materials. In addition, the surface quality of the polished surface is excellent, the rate of occurrence of scratches is low, and the polishing characteristics are excellent, but secondary particles are easily formed, and soft urethane is highly water-absorbing and has a large decrease in flexural modulus after water absorption. Therefore, it was inferior in reusability.

  In Comparative Example 6, a thermoplastic hard polyurethane resin (hard PUR (1)) was used as the resin foam. In Comparative Example 6, since the average cell diameter, the average cell wall thickness, and the ratio thereof also satisfy the scope of the present invention, the steady-state polishing rate and the like satisfy the scope of the present invention, but the bending strength of the hard urethane resin. In addition to the low tensile elastic modulus and flexural modulus, the rate of decrease in flexural modulus after water supply is large. The surface quality of the surface was inferior to the polishing pad of the present invention.

  In addition, pads made of hard urethane have high water absorption and have a large decrease in flexural modulus after water absorption. Therefore, it is necessary to perform re-polishing for dressing when reused. There was also a management problem such as having to. Therefore, it was inferior to the examples in terms of the surface quality of the polished surface, the decrease in flexural modulus due to water supply, and reusability.

  Comparative Example 7 is another urethane resin (hard PUR (2)) in which the tensile elastic modulus and bending elastic modulus are set slightly higher than those of Comparative Example 6, but in Comparative Example 7, Also, since the rate of decrease in the flexural modulus after water absorption is large, the results are almost the same as in Comparative Example 6, and in terms of the surface quality of the polished surface, the decrease in the flexural modulus due to water supply, and the reusability, from the examples inferior.

  Comparative Example 8 is a foam of glass fiber reinforced PPS resin obtained by adding 30% by mass of glass fiber to PPS resin, and has a tensile strength of 155 MPa, a tensile elastic modulus of 9300 MPa, a bending strength of 220 MPa, and a bending elastic modulus of 8500 MPa. Further, the average cell diameter, the average cell wall thickness, and the ratio thereof satisfy the scope of the present invention, so that the glass fiber is contained in terms of the polishing rate rising property and the steady-state polishing rate and reusability. The same result as that of the non-PPS resin can be obtained, but when the reinforcing glass fiber is contained in the PPS resin, scratches are generated on the surface of the disk, which is a processed test piece, and unevenness due to the separation of the glass fiber occurs. Due to the occurrence, the surface quality of the polished surface was inferior. Therefore, it was found that the fiber-reinforced PPS resin of Comparative Example 8 is not suitable for a polishing pad, although it has excellent polishing start-up property and steady-state polishing rate.

  The polishing pad of the present invention is characterized by excellent polishing start-up property and reusability, and a workpiece to be processed that requires high-definition polishing, such as a magnetic disk or semiconductor wafer mounted on various electric / electronic devices. It is preferably used in a polishing process such as

DESCRIPTION OF SYMBOLS 1 Polishing pad 1a Polishing surface 1a 'Polishing surface 2 Polishing pad 10 Polishing machine 11 Surface plate 12 Surface plate 12a Slurry hole 13 Spur gear 13a Through hole 14 External gear 15 Piping 61 Cell 61' Cell 62 Cell wall 62 'Cell wall 63a End face of cell wall 63a 'End face of cell wall

Claims (15)

A plurality of cells and a resin foam made of a thermoplastic resin having a three-dimensional cell structure configured by being partitioned by cell walls such that these cells have mutually independent partitions;
The tensile strength is 50 MPa to 90 MPa, the bending strength is a value representing the mechanical properties of the wall portion of the cell wall constituting the three-dimensional cell structure of the resin foam as the mechanical properties of the resin sheet material before foaming. 90 MPa to 140 MPa, both the tensile elastic modulus and the bending elastic modulus satisfy 2400 MPa or more,
A polishing pad having an average cell diameter of 4 μm to 50 μm, an average cell wall thickness of 1 μm to 5 μm, and a ratio of the average cell diameter to the average cell wall thickness of 4 to 10.   The polishing pad according to claim 1, wherein the resin foam is made of any one of a polyphenylene sulfide resin, a polyethylene terephthalate resin, and a polycarbonate resin.   The polishing pad according to claim 2, wherein the resin foam is made of either polyphenylene sulfide resin or polyethylene terephthalate resin. The mechanical properties of the wall of the cell walls of the resin foam as a value expressed in mechanical properties of the foam before the resin sheet material, tensile strength 70MPa～90MPa, bending strength 120MPa～140MPa, tensile elastic 4. The polishing pad according to claim 3, wherein both the elastic modulus and the bending elastic modulus satisfy 3000 MPa to 4200 MPa. A plurality of cells and a resin foam made of a thermoplastic resin having a three-dimensional cell structure configured by being partitioned by cell walls such that these cells have mutually independent partitions;
The resin foam is made of a hydrophobic polyphenylene sulfide resin,
The mechanical properties of the wall of the cell walls of the resin foam as a value expressed by the mechanical properties of the foam before the resin sheet material, greater than the bending modulus of tensile modulus, tensile modulus at 3000MPa~3500MPa Further, the bending elastic modulus is in the range of 3800 MPa to 4200 MPa, the bending elastic modulus does not decrease due to water absorption or is 10% or less, the average cell diameter is 4 μm to 50 μm, the average cell wall thickness is 1 μm to 5 μm, The polishing pad, wherein the ratio of the average cell diameter to the average cell wall thickness is in the range of 4 to 10.   The polishing pad according to any one of claims 1 to 5, wherein the polishing pad can be used without a cushion layer, and can be polished at a higher speed than a polishing pad made of a hard urethane foam structure. Polishing pad.   The polishing pad according to claim 1, wherein the polishing pad has a water absorption of 0.02 to 0.20% and is excellent in reusability. 25 ° C. before Symbol onset foam before the resin sheet material, and wherein the decrease in flexural modulus after water absorption for flexural modulus before water absorption at 48 hours immersion test is 20% or less, according to claim 1 to 6 The polishing pad according to any one of the above.   The object to be processed is a hard material of any one of a hard disk drive plate, silicon wafer, liquid crystal glass, sapphire substrate, compound semiconductor, GaN substrate, and SiC substrate. The polishing pad according to any one of 1 to 8.   The polishing pad according to claim 1, further comprising a cushion layer disposed on a side opposite to a polishing surface of the resin foam.   The polishing pad according to claim 10, wherein the compression elastic modulus of the cushion layer is smaller than the compression elastic modulus of the polishing pad, and the thickness of the cushion layer is the thickness of the cushion layer and the resin foam. A polishing pad having a thickness within 10 to 40% of the total.   A polishing pad having no cushion layer according to any one of claims 1 to 9, wherein the surface of the object to be processed is coated with abrasive grains in a state where the resin foam of the polishing pad and the object to be processed are in pressure contact with each other. A polishing method comprising polishing while containing a polishing liquid contained in the resin foam.   A polishing pad comprising the cushion layer according to claim 10 or 11, wherein the surface of the object to be processed is polished containing abrasive grains in a state where the resin foam of the polishing pad and the object to be processed are pressed against each other. A polishing method comprising polishing while supplying a liquid to the resin foam. The polishing method according to claim 12 or 13 , wherein the abrasive grains are any of alumina particles, zirconia particles, colloidal silica particles, and ceria particles.   When the polishing pad according to any one of claims 1 to 11 is used after being temporarily suspended, the surface of the polishing pad is simply cleaned and reused without repolishing. A method for using a polishing pad.

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