Polishing pad

Abstract

The present invention provides a polishing pad that maintains a polishing rate above a certain level while also providing a polishing pad with a low surface roughness on the workpiece after polishing. [Solution] An abrasive pad comprising a base material and an abrasive portion disposed on the base material, wherein the abrasive portion comprises a resin, abrasive particles, and a filler, the abrasive particles include diamond abrasive grains, and the filler comprises a first filler having a Mohs hardness of 1 or more and 2 or less, and a second filler having a Mohs hardness of 4 or more and 5 or less.

Description

Technical Field

[0001] The present invention relates to a polishing pad.

Background Art

[0002] Glass is used as a material for magnetic disks such as hard disk drives, glass substrates used as substrates for reflective masks in lithography using extreme ultraviolet (EUV light), and liquid crystal substrates and cover glasses of mobile terminals such as smartphones and tablets. The surfaces of various glass materials are required to have high smoothness and extremely few microdefects. Generally, a polishing pad with fixed abrasive grains is used for such surface processing of glass.

[0003] For example, Patent Document 1 discloses a polishing pad including a sheet-shaped substrate and a polishing layer laminated on one surface side of the substrate, aiming to provide a polishing pad with improved maintainability of the polishing rate with respect to the polishing time. The polishing layer includes abrasive grains, a filler, and a binder, and a polishing pad in which the ratio of the average particle size of the filler to the average particle size of the abrasive grains is 1.0 or more is disclosed. Patent Document 1 describes that by adjusting the average particle sizes of the abrasive grains and the filler and setting the Mohs hardness of the filler to 4 or more, the maintainability of the polishing rate can be further improved, and high polishing performance can be exhibited with respect to glass.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the inventors' investigations revealed that with conventional polishing pads, including those described in Patent Document 1, maintaining a constant polishing rate results in increased pressure when the diamond abrasive particles contact the workpiece, causing deep scratches. As a result, the surface roughness of the workpiece after polishing becomes high.

[0006] This invention has been made in view of the above-mentioned problems, and aims to provide a polishing pad that maintains a polishing rate above a certain level and has a low surface roughness of the workpiece after polishing. [Means for solving the problem]

[0007] As a result of diligent research to solve the above problems, the inventors of the present invention have found that the above problems can be solved by an abrasive pad containing a first filler having a Mohs hardness of 1 or more and 2 or less, and a second filler having a Mohs hardness of 4 or more and 5 or less, and have completed the present invention.

[0008] In other words, the present invention is as follows: [1] comprising a base material and a polishing part disposed on the base material, The polishing part includes resin, polishing particles, and a filler. The abrasive particles include diamond abrasive grains. The filler comprises a first filler having a Mohs hardness of 1 or more and 2 or less, and a second filler having a Mohs hardness of 4 or more and 5 or less. Polishing pad. [2] The content of the filler is 20% by mass or more and 60% by mass or less with respect to the total amount of the polished portion. [1] The polishing pad described above. [3] The content of the first filler is 20% by mass or more and 75% by mass or less of the total content of the first filler and the second filler. [1] The polishing pad described above. [4] The average particle size of the first filler is 1 μm or more and 30 μm or less, The average particle size of the second filler is 1 μm or more and 30 μm or less. The ratio of the average particle diameter of the second filler to the average particle diameter of the first filler is 1.0 or more and 1.5 or less. [1] The polishing pad described above. [5] The abrasive particles are composite particles in which diamond abrasive grains and matrix particles are bonded together, The average particle size of the diamond abrasive grains is 3 μm or more and 10 μm or less. The average particle diameter of the composite particles is 10 μm or more and 120 μm or less. [1] The polishing pad described above. [6] The first filler is one or more selected from the group consisting of talc and kaolinite, The second filler is wollastonite. [1] The polishing pad described above. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a polishing pad that maintains a polishing rate above a certain level while also providing a polishing pad with a low surface roughness of the workpiece after polishing. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic perspective view showing an example of the polishing pad of the present invention. [Figure 2] This is a schematic cross-sectional view showing a part of an example of the polishing pad of the present invention. [Modes for carrying out the invention]

[0011] The following describes in detail an embodiment of the present invention (hereinafter referred to as "this embodiment"), but the present invention is not limited thereto, and various modifications are possible without departing from its essence. In the drawings, the same elements are denoted by the same reference numerals, and redundant explanations are omitted. Furthermore, unless otherwise specified, positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings. Moreover, the dimensional ratios in the drawings are not limited to those shown.

[0012] 1. Polishing pad The polishing pad of the present embodiment includes a base material and a polishing portion disposed on the base material. The polishing portion includes a resin, abrasive particles, and a filler. The abrasive particles include diamond abrasive grains, and the filler includes a first filler having a Mohs hardness of 1 or more and 2 or less, and a second filler having a Mohs hardness of 4 or more and 5 or less.

[0013] FIG. 1 shows a schematic perspective view showing the polishing pad of the present embodiment. As shown in FIG. 1, this polishing pad 10 includes a base material 11 and a polishing portion 12 disposed on the base material 11. In FIG. 1, the polishing portion 12 is disposed on the base material 11, and a plurality of convex portions 15 are disposed on the surface of the polishing portion 12 to form an uneven pattern.

[0014] The polishing portion 12 may constitute an uneven pattern as shown in FIG. 1, or may be a layer having a uniform thickness without an uneven pattern. Further, the uneven pattern may be an uneven pattern in which concave portions are formed between a plurality of convex portions by disposing a plurality of convex portions. Alternatively, the uneven pattern may be a pattern (negative pattern) in the polishing portion in which a concave portion is formed by punching out a layer of resin having a uniform thickness in a dot shape, and the portion that is not punched out becomes a convex portion, or any other arbitrary pattern.

[0015] FIG. 2 is a schematic cross-sectional view showing a part of the polishing pad 10 of the present embodiment. (a) shows the state of the polishing pad 10 before polishing, and (b) shows the state of the polishing pad 10 during polishing. As shown in (a) of FIG. 2, the polishing particles 14 of the present embodiment are preferably uniformly distributed in the polishing portion 12. Since the polishing particles 14 contain diamond abrasive grains, the polishing pad of the present embodiment exhibits a high polishing rate due to the polishing ability of the diamond abrasive grains. Further, the polishing portion 12 contains a first filler and a second filler having different Mohs hardnesses as fillers, so that the disintegration property is controlled. As a result, as polishing progresses, the polishing surface of the polishing portion 12 is gradually worn away, the polishing particles 14 embedded in the polishing portion 12 are exposed, and a new polishing surface is formed. Therefore, the polishing pad can maintain a polishing rate of a certain level or more. Furthermore, by including the first filler having a Mohs hardness of 1 or more and 2 or less, the polishing stress is appropriately dispersed inside the pad during polishing. As a result, the pressing force when the polishing portion 12 contacts the workpiece to be polished does not become too strong, so that the surface roughness of the workpiece after polishing can be reduced.

[0016] Hereinafter, each component of the polishing pad 10 of the present embodiment will be described in detail.

[0017] 1.1. Substrate The substrate 11 is a member for forming the polishing portion 12 thereon, and may be attached to a polishing apparatus via an adhesive layer or the like described later.

[0018] The substrate 11 may be in a sheet shape, and its material is not particularly limited. For example, polyesters such as polyethylene terephthalate (PET), polypropylene terephthalate, and polybutylene terephthalate; polyolefins such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polycarbonate, and acrylic resin can be mentioned. Among these, acrylic resin is preferable from the viewpoints of chemical resistance, heat resistance, and economy.

[0019] 1.2. Polishing portion The polishing portion 12 contains resin, diamond abrasive grains, and a filler. The polishing portion 12 has a polishing surface for contacting the object to be polished. The polishing portion 12 may be formed as a layer of uniform thickness on the surface of the base material 11, or it may be formed to form an uneven pattern, either alone or together with the base material 11.

[0020] In particular, from the viewpoint of supplying or discharging liquid components such as coolant used during polishing to the polishing surface and efficiently discharging polishing debris, it is preferable for the polishing section 12 to have an uneven pattern, and more preferably a regular uneven pattern. Having a regular uneven pattern enables more uniform polishing and can achieve polishing with even better surface quality. A "regular pattern" refers to a pattern obtained by arranging multiple small patterns in a regular manner. The polishing surface is located on the surface of the polishing section 12 opposite to the base material 11.

[0021] The uneven pattern is not particularly limited as long as it has parts that come into contact with the workpiece (convex parts) and parts that do not come into contact with the workpiece (concave parts). Examples include a positive pattern (a pattern with dot-shaped convex parts) in which the polishing parts 12 are independently formed on the base material 11, as shown in Figure 1; a negative pattern (a pattern with dot-shaped concave parts) in which the polishing parts 12 are continuously formed on the base material 11; a pattern with donut-shaped convex parts; a pattern with roughly C-shaped convex parts; a pattern with parts that come into contact with the workpiece and parts that do not come into contact with the workpiece in a concentric pattern; a pattern with parts that come into contact with the workpiece and parts that do not come into contact with the workpiece in a grid pattern; a pattern with parts that come into contact with the workpiece and parts that do not come into contact with the workpiece in a radial pattern; a pattern with parts that come into contact with the workpiece and parts that do not come into contact with the workpiece in a spiral pattern; and patterns that are constructed by combining these. Among these, the pattern with dot-shaped convex parts is preferred. Having such an uneven pattern tends to further improve the discharge of polishing debris.

[0022] In the case of a pattern having dot-shaped protrusions, the three-dimensional shape of the dots is not particularly limited and can be, for example, hemispherical, approximately hemispherical, spherical cap-shaped, approximately spherical cap-shaped, spherical band-shaped, approximately spherical band-shaped, semi-ellipsoidal, approximately semi-ellipsoidal, columnar (e.g., cylindrical, approximately cylindrical, elliptical columnar, approximately elliptical columnar, and polygonal columnar), and frustum-shaped (e.g., frustum-shaped cone, approximately frustum-shaped cone, elliptical frustum-shaped, approximately elliptical frustum-shaped, and polygonal frustum-shaped). Of the above, the frustum-shaped may be a frustum that widens from the substrate side toward the polished surface side, or a frustum that widens from the polished surface side toward the substrate side. Also, in the case of a pattern having dot-shaped recesses, the three-dimensional shape of the space in the recesses can be similar to that of a pattern having dot-shaped protrusions. Furthermore, when a curable composition is poured into a mold and cured as described later, it is desirable that the three-dimensional shape be such that the molded body after curing can be demolded from the mold.

[0023] 1.2.1. Resin The resins are not particularly limited, but thermosetting resins and photocurable resins are preferred. Examples include polyurethane resins such as polyurethanes and polyurethane polyureas having ether or ester bonds in the molecule; acrylic resins such as monofunctional acrylates, difunctional acrylates, polyfunctional acrylates, polyester acrylates, polyurethane acrylates, epoxy acrylates, acrylic phenol resins and polyacrylonitrile; vinyl resins such as polyvinyl chloride, polyvinyl acetate and polyvinylidene fluoride; polysulfone resins such as polysulfone and polyethersulfone; acylated cellulose resins such as acetylated cellulose and butyrylated cellulose; polyamide resins; polystyrene resins; unsaturated polyester resins; phenol resins; urea resins; melamine resins; polyimide resins; alkyd resins; phenol-modified alkyd resins; and cellulose resins.

[0024] Among these, acrylic resins, polyurethane resins, unsaturated polyester resins, and phenol-modified alkyd resins are preferred, with three-dimensionally crosslinked acrylic resins being more preferred. Using such resins tends to further suppress excessive wear of the polishing pad and improve durability. The resin included in the polishing section 12 may be used alone or in combination of two or more types.

[0025] 1.2.2. Abrasive particles The abrasive particles 14 in this embodiment include diamond abrasive grains. Because diamond abrasive grains have high polishing ability, the polishing rate is improved, and a constant polishing rate can be maintained at a higher level. The abrasive particles 14 may consist only of diamond abrasive grains, or they may be particles to which other abrasive grains and auxiliary particles are bound together.

[0026] The average particle size of the abrasive particles 14 is preferably 10 μm to 120 μm, more preferably 15 μm to 110 μm, and even more preferably 20 μm to 100 μm. Because the average particle size is within the above range, the abrasive particles 14 are less likely to separate from the abrasive pad, allowing a higher level of a constant polishing rate to be maintained, and tending to result in a lower surface roughness of the workpiece after polishing.

[0027] In this invention, "average particle diameter" refers to the average particle diameter weighted by volume. The average particle diameter can be determined, for example, as follows. First, the particle diameter of individual particles is measured by observing them using laser diffraction scattering, dynamic light scattering, or an electron microscope. Assuming there are n1, n2, ni, and nk particles with particle diameters d1, d2, ...di, ...dk, and the volumes of each particle are v1, v2, ...vi, ...vk, the average particle diameter MV can be calculated using the following formula. MV=(v1·d1+v2·d2+··vi·di+··vk·dk) / (v1+v2+··vi+··vk)=Σ(vi·di) / Σ(vi)

[0028] The content of abrasive particles 14 is preferably 1.5% by mass or more and 20% by mass or less, more preferably 2.5% by mass or more and 18% by mass or less, and even more preferably 4.0% by mass or more and 15% by mass or less, relative to the total amount of abrasive portion 12. When the content of abrasive particles 14 is 1.5% by mass or more, the polishing rate tends to improve further. Also, when the content of abrasive particles 14 is 20% by mass or less, the surface roughness of the workpiece after polishing tends to be lower.

[0029] 1.2.2.1. Abrasive grains In this embodiment, the abrasive particles 14 include diamond abrasive grains. Because diamond abrasive grains have excellent polishing ability, the polishing rate is improved and a constant polishing rate can be maintained at a high level. The abrasive particles 14 may also contain abrasive grains other than diamond abrasive grains. Examples of components constituting such abrasive grains include cubic boron nitride, green silicon carbide, silicon carbide, cerium oxide, silicon carbide, boron carbide, silicon oxide, zirconium oxide, iron oxide, aluminum oxide, manganese oxide, magnesium oxide, zinc oxide, titanium oxide, zirconium silicate, boron nitride, silicon nitride, barium carbonate, and calcium carbonate.

[0030] The average particle size of the diamond abrasive grains is preferably 1.0 μm to 20.0 μm, more preferably 2.0 μm to 15.0 μm, and even more preferably 3.0 μm to 10.0 μm, depending on the workpiece and process. Having an average particle size within the above range tends to allow for a higher level of consistent polishing. Furthermore, the formation of deep scratches on the workpiece by the abrasive particles 14 is further suppressed, resulting in a lower surface roughness of the workpiece after polishing.

[0031] The diamond abrasive content is preferably 0.5% to 3% by mass, more preferably 0.7% to 2% by mass, and even more preferably 0.8% to 1.8% by mass, relative to the total amount of the polishing section 12. By having the diamond abrasive content within the above range, a constant polishing rate can be maintained at a higher level, and the surface roughness of the workpiece after polishing tends to be lower.

[0032] 1.2.2.2. Composite particles The abrasive particles 14 are preferably composite particles in which diamond abrasive grains and matrix particles are bonded together. With such abrasive particles 14, as polishing progresses, the matrix particles wear down, allowing new abrasive grains to be exposed from within. This makes it difficult for the diamond abrasive grains to fall off, and tends to maintain a constant polishing rate at a higher level. The composite particles may also contain abrasive grains other than diamond abrasive grains. In this embodiment, the matrix particles are a solid dispersion medium for the dispersed abrasive grains. In the manufacturing process, they are in particulate form, so for convenience they are called "matrix particles," but in the composite particles of this embodiment, the matrix particles are fused together and do not necessarily have to be particles. In other words, the abrasive grains may be dispersed within the fused matrix particles.

[0033] The average particle size of the composite particles is preferably 10 μm to 120 μm, more preferably 15 μm to 110 μm, and even more preferably 20 μm to 100 μm. Because the average particle size is within the above range, the composite particles are less likely to detach from the polishing pad, allowing a constant polishing rate to be maintained at a higher level, and the surface roughness of the workpiece after polishing tends to be lower.

[0034] The average particle size of the diamond abrasive grains forming the composite particles depends on the workpiece and process, but is preferably 1.0 μm to 20.0 μm, more preferably 2.0 μm to 15 μm, and even more preferably 3.0 μm to 10.0 μm. Having an average particle size within the above range tends to allow for maintaining a consistent polishing rate at a higher level. Furthermore, the formation of deep scratches on the workpiece by the abrasive particles 14 is suppressed, resulting in a lower surface roughness of the workpiece after polishing.

[0035] The ratio of the average particle diameter of the diamond abrasive grains to the average particle diameter of the composite grains (average particle diameter of diamond abrasive grains / average particle diameter of composite grains) is preferably 0.01 to 0.40, more preferably 0.03 to 0.30, and even more preferably 0.05 to 0.20. When the ratio of average particle diameters is within the above range, the abrasive particles 14 are less likely to detach from the polishing pad, a constant polishing rate can be maintained at a higher level, and the surface roughness of the workpiece after polishing tends to be lower.

[0036] The diamond abrasive content is preferably 3% to 30% by mass, more preferably 4% to 20% by mass, and even more preferably 5% to 15% by mass, relative to the total amount of composite particles. By having the diamond abrasive content within the above range, a constant polishing rate can be maintained at a higher level, and the surface roughness of the workpiece after polishing tends to be lower.

[0037] 1.2.2.3. Matrix Particles The components constituting the matrix particles are not particularly limited, but examples include silicon dioxide, boron oxide, zinc oxide, boric acid, sodium tetraborate, aluminum oxide, magnesium oxide, calcium carbonate, strontium carbonate, barium carbonate, potassium carbonate, lithium carbonate, silver carbonate, potassium nitrate, copper(I) oxide, copper(II) oxide, silver oxide, bismuth oxide, and titanium oxide. Among these, silicon dioxide, boron oxide, and zinc oxide are preferred, and it is more preferable to use glass frit obtained by melting and molding a glass material mainly composed of silicon dioxide, boron oxide, and zinc oxide, and then grinding it into a powder. By using such matrix particles, the pulverization of the matrix particles due to conditioning during polishing becomes less likely, and the fragmentation of the composite particles becomes less likely. Therefore, the retention force of the polishing particles 14 is improved, so that a constant polishing rate can be maintained at a higher level, and the surface roughness of the polished workpiece after polishing tends to be lower. These matrix particles may be used individually or in combination of two or more types.

[0038] The average particle size of the matrix particles is preferably 1.0 μm to 20 μm, more preferably 2.0 μm to 12.5 μm, and even more preferably 3.0 μm to 10 μm. When the average particle size of the matrix particles is similar to that of the polishing particles 14, the distribution within the composite particles tends to be more uniform, and the variation in polishing ability between the composite particles is reduced, resulting in a tendency for the surface roughness of the polished workpiece to be lower after polishing.

[0039] The ratio of the average particle diameter of the matrix particles to the average particle diameter of the composite particles (average particle diameter of matrix particles / average particle diameter of composite particles) is preferably 0.01 to 0.40, more preferably 0.03 to 0.30, and even more preferably 0.05 to 0.20. When the ratio of average particle diameters is within the above range, the abrasive grains are more easily fixed by the composite particles, so a constant polishing rate can be maintained at a higher level, and the surface roughness of the workpiece after polishing tends to decrease further.

[0040] The matrix particle content is preferably 25 to 60 parts by mass, more preferably 30 to 50 parts by mass, and even more preferably 35 to 45 parts by mass, per 100 parts by mass of composite particles. When the matrix particle content is within the above range, the abrasive grains are more easily fixed by the composite particles, so a constant polishing rate can be maintained at a higher level, and the surface roughness of the workpiece after polishing tends to decrease further.

[0041] 1.2.2.4. Auxiliary Particles The composite particles may include auxiliary particles that prevent the composite particles from bonding together. The components of the auxiliary particles are not particularly limited, but examples include white alumina abrasive grains, brown alumina abrasive grains, black silicon carbide abrasive grains, green silicon carbide abrasive grains, barium sulfate, and cerium oxide. Using auxiliary particles containing such components can further suppress the bonding of the composite particles, thus tending to maintain a higher polishing rate. These auxiliary particles can be used individually or in combination of two or more. Furthermore, the auxiliary particles can also function as abrasive grains.

[0042] The average particle size of the auxiliary particles is preferably 0.5 μm to 4.5 μm, more preferably 0.7 μm to 4.0 μm, and even more preferably 0.9 μm to 3.5 μm. By having the average particle size within the above range, the bonding between composite particles can be more effectively suppressed, a constant polishing rate can be maintained at a higher level, and the surface roughness of the polished workpiece after polishing tends to be lower.

[0043] The content of auxiliary particles is preferably 10.0% to 60.0% by mass, more preferably 20.0% to 55.0% by mass, and even more preferably 30.0% to 50.0% by mass, relative to the total amount of composite particles. By having the content of auxiliary particles within the above range, the bonding of composite particles can be more effectively suppressed, a constant polishing rate can be maintained at a higher level, and the surface roughness of the polished workpiece after polishing tends to be lower.

[0044] 1.2.3.Filling material The filler material should have a lower Mohs hardness than the abrasive grains. Examples include silicate minerals such as potassium aluminum silicate (Mohs hardness 6), diatomaceous earth (Mohs hardness 6-7), wollastonite (Mohs hardness 4.5-5), talc (Mohs hardness 1-2), and kaolinite (Mohs hardness 1-2); metal oxides such as iron oxide (Mohs hardness 6), titanium oxide (Mohs hardness 6.5), zinc oxide (Mohs hardness 4), and alumina (Mohs hardness 9); metal carbonates such as calcium carbonate (Mohs hardness 3) and magnesium carbonate (Mohs hardness 3.5); and metal sulfates such as calcium sulfate (Mohs hardness 3.5) and barium sulfate (Mohs hardness 3-3.5). The shape of the filler material is not particularly limited, but examples include whisker-like, columnar, flaky, and scaly shapes.

[0045] In particular, the filler in this embodiment includes a first filler with a Mohs hardness of 1 to 2 and a second filler with a Mohs hardness of 4 to 5. Because the polishing section 12 contains such fillers, its disintegration is controlled, and as polishing progresses, the polishing surface of the polishing section 12 is gradually worn away, exposing the polishing particles 14 embedded in the polishing section 12 and forming a new polishing surface, thus enabling the maintenance of a constant polishing rate at a higher level. Furthermore, by including the first filler with a Mohs hardness of 1 to 2, the polishing stress is appropriately distributed inside the pad during polishing, and the contact with the workpiece does not become too strong, thus reducing the surface roughness of the workpiece after polishing.

[0046] The filler content is preferably 20% to 60% by mass, more preferably 22.5% to 57.5% by mass, and even more preferably 25% to 55% by mass, relative to the total amount of the polishing portion 12. When the filler content is within the above range, the polishing particles 14 are appropriately dispersed in the polishing portion 12, which tends to result in a lower surface roughness of the workpiece after polishing.

[0047] 1.2.3.1.First filler The first filler is a filler having a Mohs hardness of 1 or more and 2 or less. Examples of the first filler include those listed as examples of fillers, which have a Mohs hardness of 1 or more and 2 or less. Among these, talc and kaolinite are preferred. Furthermore, the shape of the first filler is preferably a thin plate. By using such a first filler, the dispersibility of the abrasive particles 14 is further improved, and the surface roughness of the workpiece after polishing tends to be lower.

[0048] The average particle size of the first filler is preferably 1.0 μm or more and 30 μm or less, more preferably 10.0 μm or more and 20.0 μm or less, and even more preferably 11.0 μm or more and 15.0 μm or less. When the average particle size is within the above range, it is about the same as that of the abrasive particles 14, so the distribution of abrasive particles 14 and the first filler in the abrasive section 12 tends to be uniform. As a result, the variation in abrasive ability throughout the abrasive section 12 is reduced, and the surface roughness of the workpiece after abrasive polishing tends to be lower.

[0049] The content of the first filler is preferably 20% to 75% by mass, more preferably 30% to 60% by mass, and even more preferably 40% to 55% by mass, based on the total amount of the first and second fillers. When the content of the first filler is 20% by mass or more, the polishing stress can be further dispersed, thereby lowering the surface roughness of the workpiece after polishing. Furthermore, when the content of the first filler is 75% by mass or less, the durability of the polishing pad can be further improved.

[0050] The content of the first filler is preferably 5% by mass or more and 60% by mass or less, more preferably 20% by mass or more and 50% by mass or less, and even more preferably 25% by mass or more and 35% by mass or less, relative to the total amount of the polished portion 12. When the content of the first filler is within the above range, the surface roughness of the workpiece after polishing tends to be lower.

[0051] 1.2.3.2.Second filler The second filler is a filler with a Mohs hardness of 4 or more and 5 or less. Examples of the second filler include those listed as examples of fillers with a Mohs hardness of 4 or more and 5 or less. Among these, wollastonite is preferred.

[0052] The average particle size of the second filler is preferably 1.0 μm or more and 30 μm or less, more preferably 10.0 μm or more and 20.0 μm or less, and even more preferably 11.0 μm or more and 15.0 μm or less. When the average particle size of the second filler is within the above range, it is about the same as that of the abrasive particles 14, so the distribution of abrasive particles 14 and the second filler in the abrasive section 12 tends to be uniform. As a result, the variation in abrasive ability throughout the abrasive section 12 is reduced, and a constant abrasive rate tends to be maintained at a higher level.

[0053] The content of the second filler is preferably 25% to 80% by mass, more preferably 40% to 70% by mass, and even more preferably 45% to 60% by mass, relative to the total amount of the first and second fillers. Having the content of the second filler within the above range tends to maintain a certain polishing rate at a higher level.

[0054] The content of the second filler is preferably 5% by mass or more and 60% by mass or less, more preferably 20% by mass or more and 50% by mass or less, and even more preferably 25% by mass or more and 35% by mass or less, relative to the total amount of the polished portion 12. When the content of the second filler is within the above range, the surface roughness of the workpiece after polishing tends to be lower.

[0055] The ratio of the average particle diameter of the second filler to the average particle diameter of the first filler (average particle diameter of the second filler / average particle diameter of the first filler) is preferably 1.0 to 1.5, more preferably 1.05 to 1.4, and even more preferably 1.1 to 1.3. When the ratio of average particle diameters is within the above range, it tends to be possible to maintain a constant polishing rate at a higher level.

[0056] 1.3.Adhesive layer The polishing pad of this embodiment may further include an adhesive layer on the surface of the base material 11 opposite to the surface on which the polishing portion 12 is positioned, for attaching the polishing pad to the polishing platen of the polishing machine. The adhesive layer may contain an adhesive or tack agent that is used in conventionally known polishing pads.

[0057] Examples of materials for the adhesive layer include various thermoplastic adhesives such as acrylic adhesives, nitrile adhesives, nitrile rubber adhesives, polyamide adhesives, polyurethane adhesives, polyester adhesives, and silicone adhesives. The adhesive layer may also be double-sided tape.

[0058] 1.3. Method for manufacturing polishing pads The polishing pad of this embodiment can be manufactured, for example, as follows.

[0059] When using composite particles as abrasive particles, first, diamond abrasive particles and matrix particles are mixed to prepare a mixture. If necessary, a binder resin, solvent, and dispersant may be added to form a slurry.

[0060] The binder resin is preferably a resin that can bind diamond abrasive grains and matrix particles and decomposes thermally when fired, and more preferably a water-soluble resin. Examples of such binder resins include dextrin, polyvinyl alcohol, polyethylene glycol, polyacrylic acid, and polyacrylamide, with dextrin being even more preferred. These binder resins can be used individually or in combination of two or more.

[0061] Examples of solvents include water and alcohols such as methanol and isopropanol, with water being preferred. These solvents may be used individually or in combination of two or more.

[0062] The dispersant is not particularly limited, but examples include quaternary ammonium salts, polycarboxylic acid-based surfactants, and maleic anhydride-based surfactants. Commercially available dispersants may also be used, such as Celna D-735 (product name, manufactured by Chukyo Oil Co., Ltd.). These dispersants may be used individually or in combination of two or more.

[0063] In addition to the above-mentioned components, other additives may be included. Examples of other additives include surfactants. These additives may be used individually or in combination of two or more.

[0064] Next, the mixture obtained above is granulated to obtain a composite particle precursor. The granulation method is not particularly limited, but one example is a method using a spray dryer or similar spray drying machine. In this method, the slurry of the mixture is sprayed into heated air, and the solvent (dispersion) is evaporated to obtain particles of the composite particle precursor. The granulation conditions are not particularly limited and can be set as appropriate depending on the desired composite particle.

[0065] Next, the composite particle precursor obtained above is calcined to produce composite particles. At this time, auxiliary particles may be mixed in before calcination.

[0066] The firing temperature depends on the type of matrix particles, but is preferably 500°C to 700°C, more preferably 530°C to 670°C, even more preferably 550°C to 650°C, and even more preferably 560°C to 630°C. When the firing temperature is within the above range, the bonding of the composite particles can be suppressed, thus preventing the composite particles from becoming irregularly shaped. As a result, the ability of the polishing pad to hold the composite particles is improved, and a constant polishing rate tends to be maintained at a higher level.

[0067] The firing time may be adjusted as appropriate to obtain the desired composite particles, but is preferably 0.5 hours or more and 30 hours or less, more preferably 1 hour or more and 10 hours or less, and even more preferably 2 hours or more and 7 hours or less.

[0068] The atmosphere during firing is not particularly limited, but is preferably an atmospheric atmosphere. In an atmospheric atmosphere, the variation in the strength of the composite particles is more stable, so the surface roughness of the workpiece after polishing tends to be lower when used as a polishing pad.

[0069] Next, a curable composition containing resin, composite particles, and filler is placed in a mold such as an intaglio plate and molded. Then, a substrate is placed in contact with the curable composition, and the curable composition is cured to obtain a polishing pad comprising a substrate and a polishing surface. The curing method is not particularly limited, but examples include photocuring and thermocuring, and can be selected according to the resin used.

[0070] The curable composition may optionally contain a polymerization initiator. While not particularly limited, examples of polymerization initiators include photopolymerization initiators and thermal polymerization initiators.

[0071] The photopolymerization initiator is not particularly limited, but examples include benzophenone compounds, acetophenone compounds, and thiothisanthone compounds. Commercially available photopolymerization initiators may also be used, such as Irgacure 819 (bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, product name, manufactured by BASF Japan) and Anthracure UVS-581 (product name, manufactured by Kawasaki Chemical Industries, Ltd.).

[0072] Examples of thermal polymerization initiators include azo compounds such as 2,2'-azobisbutyronitrile and peroxides such as benzoyl peroxide (BPO).

[0073] When curing a curable composition, after it has hardened to a certain extent, the molded body may be removed from the mold and further cured by heating it in a drying oven.

[0074] After curing, if necessary, a portion of the curable composition and the polished area may be removed to form the desired textured pattern. One method of removal is, for example, cutting. [Examples]

[0075] The present invention will be described more specifically below using examples and comparative examples. The present invention is not limited in any way by the following examples.

[0076] [Example 1] (Fabrication of composite particles) A slurry was prepared by mixing 12 parts by mass of dextrin (manufactured by Tokai Dextrin), 40 parts by mass of purified water, 1 part by mass of the dispersant Celna D-735 (product name, manufactured by Chukyo Oil & Fat Co., Ltd.), 42.3 parts by mass of glass frit with an average particle size of 2.8 μm, and 4.7 parts by mass of diamond powder with an average particle size of 4 μm. The slurry was then spray-dried using a spray dryer to form a composite particle precursor. Next, the composite particle precursor was mixed with white alumina (manufactured by Fujimi Co., Ltd., average particle size of 3 μm) in a 5:5 mass ratio. The resulting mixture was calcined at 600°C for 4 hours to obtain composite particles with an average particle size of 21.7 μm.

[0077] (Preparation of curable composition) A precursor composition was prepared by mixing 96.9 parts by mass of the resin composition SR368D (product name, a mixture of trimethylolpropane triacrylate and tris(2-hydroxyethyl) isocyanurate triacrylate in a mass ratio of 70:30, manufactured by Sartomer), 1.6 parts by mass of the dispersant Solspers 32000 (product name, manufactured by Lubrizol Nippon), 1 part by mass of the photopolymerization initiator Irgacure 819 (product name, manufactured by BASF Japan), and 0.5 parts by mass of the photopolymerization initiator UVS-581 (product name, manufactured by Kawasaki Chemical Industries, Ltd.).

[0078] Next, a curable composition was prepared by mixing 37.2 parts by mass of the above precursor composition, 12.06 parts by mass of composite particles, 12.06 parts by mass of white alumina (manufactured by Fujimi Co., Ltd., average particle size 3 μm), 7.74 parts by mass of talc SSS (talc, product name, manufactured by Nippon Talc Co., Ltd., average particle size 12 μm, thin plate form), which is the first filler, and 30.94 parts by mass of wollastonite K-400 (wollastonite, product name, manufactured by Keiwa Fine Material Co., Ltd., average particle size 13.5 μm), which is the second filler.

[0079] (Making polishing pads) The resulting curable composition was poured into a silicone molding plate consisting of a rectangular prism recess with a depth of 2 mm, a cavity opening of 2.6 mm x 2.6 mm, and a spacing of 1 mm between adjacent openings. A PET substrate was then placed so as to be in contact with the upper surface of the curable composition. The curable composition was then cured by irradiating it with ultraviolet light using an ultraviolet irradiation machine. After that, the resulting molded body was removed from the molding plate, and the side that had been in contact with the molding plate was irradiated with ultraviolet light to obtain the polishing pad of Example 1.

[0080] [Example 2] The polishing pad of Example 2 was obtained in the same manner as in Example 1, except that the amount of talc SSS, which is the first filler, was changed to 19.34 parts by mass, and the amount of wollastonite K-400, which is the second filler, was changed to 19.34 parts by mass.

[0081] [Example 3] The polishing pad of Example 3 was obtained in the same manner as in Example 1, except that the amount of talc SSS, the first filler, was changed to 29.01 parts by mass, and the amount of wollastonite K-400, the second filler, was changed to 9.67 parts by mass.

[0082] [Example 4] The polishing pad of Example 4 was obtained in the same manner as in Example 1, except that 7.74 parts by mass of talc RA-3 (product name, manufactured by Nippon Talc Co., Ltd., average particle size 5 μm) was used as the first filler, and the amount of wollastonite K-400 added as the second filler was changed to 30.94 parts by mass.

[0083] [Example 5] The polishing pad of Example 5 was obtained in the same manner as in Example 1, except that 7.74 parts by mass of talc MS-KY (product name, manufactured by Nippon Talc Co., Ltd., average particle size 21 μm) was used as the first filler, and the amount of wollastonite K-400 added as the second filler was changed to 30.94 parts by mass.

[0084] [Comparative Example 1] A polishing pad for Comparative Example 1 was obtained in the same manner as in Example 1, except that the first filler was not used, and 38.68 parts by mass of wollastonite K-400, which is the second filler, was used.

[0085] [Comparative Example 2] An attempt was made to prepare a curable composition in the same manner as in Example 1, except that the second filler was not used, and 38.68 parts by mass of the first filler, talc SSS, was used. As a result, the mixture formed into lumpy aggregates during the mixing process, making it impossible to pour it into the intaglio plate, and thus no polishing pad could be obtained.

[0086] [Polishing test] For each example and comparative example, a glass polishing test was performed on the polishing pads under the following test conditions, and the surface roughness of the glass and the polished mass were measured after 70 minutes.

[0087] (polishing conditions) Testing machine: Speedfam Friction and Wear Testing Machine (Product name, surface plate size 305mmφ) Dresser: White Alundum (WA) Sharpening Stone #1000 Dressing time: 5-20 minutes Load: 200g / cm 2 Rotation speed: 80 rpm Time: 10 minutes / batch x 7 batches Lubricant: 10x diluted aqueous solution of Sabrelbe 9016 (product name, manufactured by Chemetall). Lubricant flow rate: 30 mL / min Material to be polished: Glass (50mm x 50mm)

[0088] (Surface roughness Sa of the workpiece) The surface roughness Ra of the polished workpiece was measured using a ZygoNewView5010 optical interferometer (manufactured by Canon) after polishing. (Evaluation Criteria) A: The surface roughness Sa of the glass is less than 40 nm. B: The surface roughness Sa of the glass is between 40nm and 45nm. C: The surface roughness Sa of the glass is 45 nm or greater.

[0089] (Abrasive mass of non-abrasive material) The polishing mass was calculated from the difference in weight of the workpiece before and after polishing and evaluated according to the following criteria. (Evaluation Criteria) A: The amount of glass polishing is 35 mg or more. B: The amount of glass polishing is 30 mg or more but less than 35 mg. C: The amount of glass polishing is less than 30 mg.

[0090] [Table 1]

[0091] In Examples 1-4, where both the first and second fillers were used, the surface roughness of the workpiece after polishing was reduced despite the large amount of polishing. On the other hand, in Comparative Example 1, where only the second filler was used, the surface roughness of the workpiece after polishing was increased. It is believed that the polishing pads of Examples 1-4, which contain a first filler with a Mohs hardness of 1 to 2 and a second filler with a Mohs hardness of 4 to 5, were able to maintain a constant polishing rate at a higher level and further reduce the surface roughness of the workpiece after polishing. [Industrial applicability]

[0092] The polishing pad of the present invention has industrial applicability as a polishing pad suitable for surface processing of various glass materials. [Explanation of Symbols]

[0093] 10... polishing pad, 11... base material, 12... polishing part, 14... polishing particles, 15... protrusions.

Claims

1. It comprises a base material and a polishing part disposed on the base material, The polishing part includes resin, polishing particles, and a filler. The abrasive particles include diamond abrasive grains. The filler comprises a first filler having a Mohs hardness of 1 or more and 2 or less, and a second filler having a Mohs hardness of 4 or more and 5 or less. Polishing pad.

2. The content of the filler is 20% by mass or more and 60% by mass or less relative to the total amount of the polished portion. The polishing pad according to claim 1.

3. The content of the first filler is 20% by mass or more and 75% by mass or less of the total content of the first filler and the second filler. The polishing pad according to claim 1.

4. The average particle size of the first filler is 1 μm or more and 30 μm or less. The average particle size of the second filler is 1 μm or more and 30 μm or less. The ratio of the average particle diameter of the second filler to the average particle diameter of the first filler is 1.0 or more and 1.5 or less. The polishing pad according to claim 1.

5. The abrasive particles are composite particles in which diamond abrasive grains and matrix particles are bonded together, The average particle size of the diamond abrasive grains is 3 μm or more and 10 μm or less. The average particle diameter of the composite particles is 10 μm or more and 120 μm or less. The polishing pad according to claim 1.

6. The first filler is one or more selected from the group consisting of talc and kaolinite, The second filler is wollastonite. The polishing pad according to claim 1.

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