Polishing pad and method for manufacturing the same

Abstract

To provide a polishing pad which enables provision of an object to be polished having low surface roughness while improving self dressing properties and maintaining a stable polishing rate, and a method for manufacturing the same.SOLUTION: A polishing pad includes a base material, and a polishing part arranged on the base material, wherein the polishing part contains a resin and composite fine particles, the composite fine particles contain diamond abrasive grains, the composite fine particles contain hollow composite fine particles, and a content ratio of the hollow composite fine particles is 5 to 40 mass% with respect to the total amount of the composite fine particles.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polishing pad and a method for manufacturing the same. [Background technology]

[0002] Glass is used as a material for magnetic disks such as hard disk drives, glass substrates used as the base material for reflective masks used in EUV lithography, and LCD substrates and cover glasses for mobile devices such as smartphones and tablets.The surfaces of various glass materials must be highly smooth and have as few micro-defects as possible.Fixed abrasive polishing pads are generally used for surface processing of such glass and difficult-to-cut materials.

[0003] For example, Patent Document 1 proposes an abrasive comprising a substrate sheet and an abrasive layer laminated on the surface of the substrate sheet and containing diamond abrasive grains and a binder therefor, wherein the abrasive layer contains multiple types of abrasive grains, of which the abrasive grains with the largest average particle size are designated as first abrasive grains and the abrasive grains with the second largest average particle size are designated as second abrasive grains, and the ratio of the average particle size of the second abrasive grains to the average particle size of the first abrasive grains is 5% to 70%. This abrasive is disclosed as a technology that prevents a decrease in the polishing rate due to excessive abrasion of the abrasive grains, as alumina abrasive grains, which are smaller than the diamond abrasive grains, are dislodged from the abrasive layer before the diamond abrasive grains, causing a moderate shedding of part of the abrasive layer. This dislodges the diamond abrasive grains, which have a relatively reduced grinding force, exposing new abrasive grains.

[0004] Patent Document 2 proposes a grinding tool that includes diamond abrasive grains, a binder, and dispersed grains that are harder than the binder but softer than the diamond abrasive grains, with the diamond abrasive grains and dispersed grains dispersed and bonded within the binder. This grinding tool disperses abrasive grains made of a material softer than the diamond abrasive grains and their aggregates (dispersed grains) together with diamond abrasive grains formed by solidifying multiple diamond abrasive grains with glass, thereby uniformly increasing the distance between the diamond abrasive grains and increasing the processing speed. The presence of the dispersed grains prevents excessive pressure from concentrating on the diamond abrasive grains, thereby suppressing tool wear. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2017 / 163565 [Patent Document 2] Japanese Patent Application Publication No. 2018-092697 Summary of the Invention [Problem to be solved by the invention]

[0006] However, while the abrasive described in Patent Document 1 can maintain a high polishing rate, it has low grip strength for diamond abrasive grains, and small diamond abrasive grains with a particle size of around 10 μm tend to fall off. This reduces the number of diamond abrasive grains held on the polishing surface, lowering the polishing rate, and roughening the polished surface, making it impossible to reduce the surface roughness of the workpiece. Furthermore, the grinding tool described in Patent Document 2 uses aggregated abrasive grains, which makes diamond abrasive grains less likely to fall off. However, the mixture of dispersed and aggregated abrasive grains results in particles of different strengths being unevenly distributed on the grinding tool surface, which causes inconsistent grinding within the surface during the dressing process performed for surface finishing and unclogged grinding, resulting in poor polishing characteristics. Therefore, there is still room for improvement in suppressing the decrease in polishing rate and achieving both a maintained polishing rate and a reduced surface roughness of the workpiece.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a polishing pad and a manufacturing method thereof that have improved self-dressing properties, can maintain a stable polishing rate, and can produce polished objects with low surface roughness. [Means for solving the problem]

[0008] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by using a predetermined amount of hollow composite fine particles, and have thus completed the present invention.

[0009] That is, the present invention is as follows. [1] A substrate and an abrasive portion disposed on the substrate, the polishing portion includes a resin and composite fine particles, The composite microparticles include diamond abrasive grains, the composite particles include hollow composite particles, The content of the hollow composite fine particles is 5 to 40 mass% based on the total amount of the composite fine particles. Polishing pad. [2] the composite particulates further comprise solid composite particulates; the difference between the crushing strength (Cs1) of the hollow composite microparticles and the crushing strength (Cs2) of the solid composite microparticles is 40.0 to 100.0 MPa; [1] The polishing pad according to [1]. [3] The hollow composite fine particles have an average particle size of 20 to 100 μm. [1] or [2]. The polishing pad according to [1] or [2]. [4] The thickness of the shell of the hollow composite fine particles is 5 to 35 μm. The polishing pad according to any one of [1] to [3]. [5] The average particle size of the diamond abrasive grains is 3 to 9 μm. The polishing pad according to any one of [1] to [4]. [6] The polishing portion has a convex portion. The polishing pad according to any one of [1] to [5]. [7] a firing step of firing a composite microparticle precursor containing diamond abrasive grains and matrix particles to obtain composite microparticles; a curing step of curing a curable composition containing a resin and the composite fine particles to obtain a polishing part; a joining step of joining a surface of the polishing part opposite to the polishing surface to a substrate, the composite particles include hollow composite particles, The content of the hollow composite fine particles is 5 to 40 mass% based on the total amount of the composite fine particles. A method for manufacturing a polishing pad. [8] [1] to [6], comprising a step of polishing an object to be polished using the polishing pad according to any one of [1] to [6]. Manufacturing method for polished products. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a polishing pad and a manufacturing method thereof that have improved self-dressing properties, can maintain a stable polishing rate, and can produce polished objects with low surface roughness. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view showing a polishing pad according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view showing the polishing pad of the present embodiment. [Figure 3] 1 is an electron microscope photograph of a cross section of hollow composite fine particles. DETAILED DESCRIPTION OF THE INVENTION

[0012] Below, we will explain in detail the embodiment of the present invention (hereinafter referred to as the ``present embodiment''), but the present invention is not limited to this and various modifications are possible within the scope of the gist of the present invention.

[0013] 1. Polishing pad The polishing pad of this embodiment comprises a substrate and a polishing portion disposed on the substrate, the polishing portion containing a resin and composite microparticles, the composite microparticles containing diamond abrasive grains, the composite microparticles containing hollow composite microparticles, and the content of the hollow composite microparticles is 5 to 40 mass% relative to the total amount of the composite microparticles.

[0014] A schematic perspective view of a polishing pad according to this embodiment is shown in Figure 1. As shown in Figure 1, this polishing pad 10 includes a substrate 11 and a polishing portion 12 disposed on the substrate 11. In Figure 1, a plurality of convex portions formed by the polishing portion 12 are disposed on the surface of the substrate 11, forming an uneven pattern.

[0015] The polishing portions 12 may form a concave-convex pattern together with the substrate 11 as shown in Fig. 1, or may be a uniform layer formed on the surface of the substrate. The concave-convex pattern may be a pattern (negative pattern) formed by the polishing portions 12 formed by punching out dots from a uniform layer, in addition to a concave-convex pattern formed by arranging convex portions, or any other pattern.

[0016] FIG. 2 shows a schematic cross-sectional view of a polishing pad according to this embodiment. As shown in FIG. 2, the polishing portion 12 of the polishing pad 10 according to this embodiment contains composite particles 14 and a resin 15. As polishing progresses, the polishing surface of the polishing portion 12 gradually wears away, exposing the composite particles 14 that were embedded in the polishing portion 12 and forming a new polishing surface, which tends to maintain the polishing rate. Furthermore, the inclusion of hollow composite particles in the composite particles 14 reduces the contact area between the polishing surface of the polishing pad and the workpiece, effectively applying a load to the workpiece and tending to improve polishing performance. Furthermore, the inclusion of hollow composite particles improves self-dressing properties, making them less susceptible to glazing, and suppressing a decrease in the polishing rate even during prolonged polishing. Furthermore, when a processing fluid is used, the open hollow portion can retain the processing fluid, improving polishing efficiency.

[0017] Each component of the polishing pad of this embodiment will be described in detail below.

[0018] 1.1. Base material The substrate is a member on which the polishing section 12 is formed, and may be attached to the polishing device via an adhesive layer or the like, which will be described later.

[0019] The substrate is not particularly limited, but examples thereof include polyester sheets such as polyethylene terephthalate sheets, polypropylene terephthalate sheets, and polybutylene terephthalate sheets; polyolefin sheets such as polyethylene (PE) sheets, polypropylene (PP) sheets, and ethylene-propylene copolymer sheets; polyether ether ketone (PEEK) sheets, polyphenylene sulfide (PPS) sheets, polycarbonate sheets, and acrylic sheets. Among these, polyester sheets are preferred from the viewpoints of chemical resistance, heat resistance, and economy, while acrylic sheets are preferred from the viewpoints of rigidity and adhesiveness.

[0020] 1.2. Polishing section The abrasive part contains a resin and composite particles, and may contain other spacer particles as needed. The abrasive part may be formed as a uniform layer on the surface of the substrate, or may be formed alone or together with the substrate to form a concave-convex pattern (see Figures 1 and 2). When the abrasive part rubs the surface of the workpiece, the abrasive particles held by the composite particles scrape the surface of the workpiece, and the composite particles gradually break down, supplying new abrasive particles.

[0021] Among these, from the viewpoint of supplying or discharging liquid components used during polishing, such as coolant, to the polishing surface and efficiently discharging polishing debris, it is preferable that the polishing part has an uneven pattern, and more preferably a regular uneven pattern. Having a regular pattern enables uniform polishing and can achieve polishing with excellent surface quality. Note that a "regular pattern" refers to a pattern obtained by arranging multiple small unit patterns. The surface of the polishing part opposite the substrate serves as the polishing surface for polishing the workpiece.

[0022] The concave-convex pattern is not particularly limited as long as it has portions that contact the workpiece (convex portions) and portions that do not contact the workpiece (concave portions). Examples include a positive pattern (a pattern with dot-shaped convex portions) in which the abrasive portions 12 are independently formed on the substrate 11 as shown in FIG. 1; a negative pattern (a pattern with dot-shaped concave portions) in which the abrasive portions are continuously formed on the substrate; a pattern with donut-shaped convex portions; a pattern with approximately C-shaped convex portions; a pattern with concentric circular portions that contact the workpiece and portions that do not contact the workpiece; a grid-shaped pattern with portions that contact the workpiece and portions that do not contact the workpiece; a radial pattern with portions that contact the workpiece and portions that do not contact the workpiece; a spiral pattern with portions that contact the workpiece and portions that do not contact the workpiece; or a pattern formed by combining these. Among these, a pattern with dot-shaped convex portions is preferred. Having such a concave-convex pattern tends to further improve the discharge of polishing debris.

[0023] In addition, the three-dimensional shape of the dots in a pattern having dot-shaped protrusions is not particularly limited, and examples thereof include hemispheres, approximately hemispheres, spherical caps, approximately spherical caps, spherical bands, approximately spherical bands, semi-ellipsoids, approximately semi-ellipsoids, cylinders (cylindrical, approximately cylindrical, elliptical, approximately elliptical, polygonal), and truncated cones (circular truncated cones, approximately circular truncated cones, elliptical truncated cones, approximately elliptical truncated cones, polygonal truncated cones). Of the above, the truncated cones may be truncated cones that expand from the substrate side toward the polishing surface side, or from the polishing surface side toward the substrate side. Furthermore, in a pattern having dot-shaped recesses, the three-dimensional shape of the space in the recesses may be similar to the three-dimensional shape in a pattern having dot-shaped protrusions.

[0024] Resin The resin is not particularly limited, but thermosetting resins and photocurable resins are preferred, and examples thereof include polyurethane-based resins such as polyurethanes having an ether or ester bond in the molecule and polyurethane polyureas; acrylic resins such as monofunctional acrylates, difunctional acrylates, polyfunctional acrylates, polyester acrylates, polyurethane acrylates, epoxy acrylates, acrylic phenolic resins, and polyacrylonitrile; vinyl resins such as polyvinyl chloride, polyvinyl acetate, and polyvinylidene fluoride; polysulfone-based resins such as polysulfone and polyethersulfone; acylated cellulose-based resins such as acetylated cellulose and butyrylated cellulose; polyamide-based resins; and polystyrene-based resins, unsaturated polyester resins, phenolic resins, urea resins, melamine resins, polyimide resins, alkyd resins, phenol-modified alkyd resins, and cellulose-based resins.

[0025] Among these, acrylic resin, polyurethane resin, unsaturated polyester resin, phenol-modified alkyd resin are preferred, and three-dimensionally crosslinked acrylic resin is more preferred. By using such resin, the polishing pad tends to be prevented from being worn too much and can be used for a long time. In addition, the resin constituting the polishing part may be used alone or in combination of two or more kinds.

[0026] 1.2.2. Composite fine particles The composite microparticles contain diamond abrasive grains as abrasive microparticles, which are components that contribute to polishing. The composite microparticles may be composite microparticles that contain matrix particles in addition to diamond abrasive grains. They may also contain other abrasive microparticles, auxiliary particles, etc. Here, the matrix particles are a solid dispersion medium for the abrasive microparticles, which are dispersoids. Because they are in particulate form during the manufacturing process, they are referred to as "matrix particles" for convenience, but in the composite microparticles of this embodiment, the matrix particles are fused to each other and do not need to be particles. In other words, the abrasive microparticles may be dispersed in the fused matrix particles. Furthermore, the auxiliary particles may be particles added to suppress blocking between the composite microparticles.

[0027] Among these, it is preferable that the composite particles contain diamond abrasive particles as abrasive particles and matrix particles, which increases the polishing efficiency because new abrasive particles are exposed from the inside as the matrix particles wear.

[0028] The composite particles include hollow composite particles, which are hollow composite particles having an outer shell (shell portion) and a hollow structure with a hollow interior (see FIG. 3). In addition to hollow composite particles, the composite particles may also include other composite particles, such as solid composite particles that are not hollow inside.

[0029] The crushing strength (Cs) of the composite microparticles is preferably 50.0 to 300.0 MPa, more preferably 60.0 to 200.0 MPa, and even more preferably 70.0 to 160.0 MPa. By having the crushing strength within the above range, it is possible to prevent the abrasive microparticles from easily detaching from the composite microparticles, and it tends to be possible to prevent a decrease in the polishing rate. It also tends to be possible to prevent scratches on the polished object caused by the rolling of the detached diamond abrasive grains. Furthermore, after the dressing process, it tends to be possible to prevent scratches on the polished object caused by the diamond abrasive grains being fixed in a protruding state on the polishing surface, and it tends to be possible to prevent a deterioration in surface roughness.

[0030] In the present invention, the "crushing strength" can be determined by measuring the crushing strength of five composite microparticles using the crushing strength measurement method described below and calculating the average value. The crushing strength can be adjusted by the firing temperature, firing time, and firing atmosphere, such as the amount of oxygen, when preparing the composite microparticles.

[0031] The average particle diameter (Da) of the composite fine particles is preferably 20 to 100 μm, more preferably 25 to 90 μm, and even more preferably 30 to 80 μm. When the average particle diameter is within the above range, the composite fine particles are less likely to detach from the polishing pad, the polishing rate is more stably maintained, and the surface roughness of the resulting polished object tends to be reduced.

[0032] In the present invention, the term "average particle size" refers to the particle size at which the cumulative particle volume accounts for 50% of the total in a particle size distribution graph with particle size on the horizontal axis and cumulative particle volume on the vertical axis. Such an average particle size is also called the median diameter or d50. The particle size distribution graph can be obtained by a laser diffraction scattering method or the like.

[0033] The content of the composite particles is preferably 1.5 to 25.0 mass% relative to the total amount of the polishing part, more preferably 2.5 to 22.0 mass%, and even more preferably 3.5 to 20.0 mass%. When the content of the composite particles is 1.5 mass% or more, the polishing rate tends to be further improved. Furthermore, when the content of the composite particles is 25.0 mass% or less, the grinding force tends to be further improved.

[0034] 1.2.2.1.Hollow composite particles The composite microparticles include hollow composite microparticles. Hollow composite microparticles are hollow bodies with an outer shell (shell portion) and a hollow structure with a cavity inside. Hollow composite microparticles can be confirmed as hollow bodies by observing the cross section of the polishing portion or the cross section of the composite microparticle using a scanning electron microscope (SEM) or the like. The shell portion of the hollow composite microparticles contains diamond abrasive grains, preferably diamond abrasive grains and matrix grains. The diamond abrasive grains may be dispersed in the matrix grains. This allows new abrasive microparticles to be exposed from inside the shell portion as the matrix grains in the shell portion of the hollow composite microparticles wear, thereby improving the polishing efficiency. The shape of the hollow composite microparticles is not particularly limited, but examples include spherical, elliptical, and shapes similar to these.

[0035] The average particle size of the hollow composite fine particles is preferably 20 to 100 μm, more preferably 25 to 90 μm, and even more preferably 30 to 80 μm. When the average particle size is within the above range, the abrasive particles can be encapsulated in the shell, which tends to improve polishing performance. The average particle size can be appropriately adjusted by the concentration of the slurry of the hollow composite fine particle precursor composition, the granulation conditions of the spray dryer (spray amount, spray pressure, nozzle diameter, hot air temperature), etc.

[0036] The thickness of the shell of the hollow composite microparticles is preferably 5 to 35 μm, more preferably 6 to 30 μm, and even more preferably 7 to 25 μm. Having a shell thickness within this range allows the abrasive particles to be enclosed in the shell, which tends to improve polishing performance. The shell thickness can be measured using a micrograph of the cross section of the abrasive part or the cross section of the hollow composite microparticles. The shell thickness can be adjusted appropriately by adjusting the firing temperature, firing time, and firing atmosphere (e.g., oxygen content) when preparing the hollow composite microparticles, as well as the solids concentration and drying speed when preparing the hollow composite microparticle precursor.

[0037] The crushing strength (Cs1) of the hollow composite particles is preferably 15.0 to 130.0 MPa, more preferably 20.0 to 120.0 MPa, and even more preferably 30.0 to 110.0 MPa. When the crushing strength is within the above range, the hollow composite particles tend to be appropriately easily disintegrated and have improved self-dressing properties. As a result, the particles are less likely to be crushed, and even during long-term polishing, a decrease in the polishing rate can be suppressed, tending to provide a stable polishing rate.

[0038] The content of hollow composite particles is 5 to 40% by mass, preferably 7 to 38% by mass, and more preferably 9 to 36% by mass, based on the total amount of composite particles. When the content of hollow composite particles is within the above range, the contact area between the polishing surface of the polishing pad and the workpiece to be polished is reduced, and a load is effectively applied to the workpiece, tending to improve polishing performance. Furthermore, the inclusion of hollow composite particles tends to improve self-dressing properties, making it less susceptible to glazing, and inhibiting a decrease in polishing rate even during long-term polishing. Furthermore, when a processing fluid is used, the open hollow portion can retain the processing fluid, tending to improve polishing efficiency.

[0039] 1.2.2.2. Solid Composite Particles The composite particles may include solid composite particles in addition to hollow composite particles. Solid composite particles are composite particles having a solid structure. The solid structure of the solid composite particles can be confirmed by observing the cross section of the polished portion or the cross section of the composite particles using a scanning electron microscope (SEM) or the like.

[0040] The average particle size of the solid composite fine particles is preferably 20 to 100 μm, more preferably 25 to 90 μm, and even more preferably 30 to 80 μm. When the average particle size is within the above range, the composite fine particles are less likely to detach from the polishing pad, the polishing rate is more stably maintained, and the surface roughness of the resulting polished object tends to be reduced.

[0041] The crushing strength (Cs2) of the solid composite microparticles is preferably 100.0 to 300.0 MPa, more preferably 100.0 to 200.0 MPa, and even more preferably 120.0 to 160.0 MPa. A crushing strength of 100.0 MPa or more tends to prevent the abrasive microparticles from easily detaching from the composite microparticles, and tends to prevent a decrease in the polishing rate. In addition, it tends to prevent scratches on the polished object caused by the rolling of detached diamond abrasive grains. A crushing strength of 300.0 MPa or less tends to prevent the diamond abrasive grains from being fixed in a protruding state on the polishing surface after the dressing process, and tends to prevent the surface roughness of the polished object from deteriorating.

[0042] The content of the solid composite particles is 60 to 95 mass %, preferably 62 to 93 mass %, and more preferably 64 to 91 mass %, based on the total amount of the composite particles. When the content of the solid composite particles is within the above range, the polishing rate is stably maintained, and the surface roughness of the polished object tends to be further reduced.

[0043] The difference between the crushing strength (Cs1) of the hollow composite particles and the crushing strength (Cs2) of the solid composite particles is preferably 40.0 to 100.0 MPa, more preferably 45.0 to 85.0 MPa, and even more preferably 50.0 to 70.0 MPa. When the difference between the crushing strength (Cs1) of the hollow composite particles and the crushing strength (Cs2) of the solid composite particles is within the above range, appropriate self-dressing properties are obtained, the polishing rate can be maintained more stably, and the surface roughness of the resulting polished object tends to be reduced.

[0044] 1.2.2.3. Abrasive particles The components constituting the abrasive particles are not particularly limited as long as they contain diamond abrasive grains, but they are the hardest material in the polishing pad and are composed of the components with the highest grinding ability. In addition to diamond abrasive grains, for example, 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 can be mentioned. Among them, diamond abrasive grains have the best grinding ability. These abrasive particles can be used alone or in combination of two or more types.

[0045] The average particle diameter (Dd) of the abrasive particles varies depending on the object to be polished and the process, but is preferably 1.0 to 20.0 μm, more preferably 2.0 to 12.5 μm, and even more preferably 3.0 to 10.0 μm. By keeping the average particle diameter within the above range, it is possible to prevent the abrasive particles from forming deep scratches on the object to be polished.

[0046] The ratio (Dd / Da) of the average particle size (Dd) of the abrasive fine particles to the average particle size (Da) of the composite fine 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 average particle size ratio (Dd / Da) is within the above range, the abrasive fine particles that do not cause deep scratches are less likely to detach from the polishing pad, the removal rate can be more stably maintained, and the surface roughness of the resulting polished object tends to be further reduced.

[0047] The average particle size of the diamond abrasive grains varies depending on the workpiece and process, but is preferably 1.0 to 20.0 μm, more preferably 2.0 to 12.5 μm, and even more preferably 3.0 to 10.0 μm. By keeping the average particle size within the above range, it is possible to prevent the abrasive particles from forming deep scratches on the workpiece. In addition, the abrasive particles can be contained in the shell portion, which tends to improve polishing performance.

[0048] The content of the abrasive particles is preferably 1.0 to 30.0 mass % of the total amount of the composite particles, more preferably 3.0 to 20.0 mass %, and even more preferably 5.0 to 15.0 mass %. When the content of the abrasive particles is within the above range, there are an adequate number of contact points between the abrasive particles and the workpiece to be polished, and the load applied to each abrasive particle is not too large, so the polishing rate can be maintained more stably and the surface roughness of the resulting workpiece tends to be reduced.

[0049] 1.2.2.4. Matrix particles The components constituting the matrix particles are not particularly limited, but may include at least one selected from the group consisting of 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. More preferred is the use of glass frit, which is obtained by melt-molding a glass material primarily composed of silicon dioxide, boron oxide, and zinc oxide and then powdering it. The use of such matrix particles results in composite particles strong enough to hold abrasive particles without shattering the composite particles due to grinding of the matrix particles during conditioning, thereby maintaining more stable polishing and tending to reduce the surface roughness of the resulting polished object. These matrix particles may be used alone or in combination.

[0050] The powdered matrix particles preferably have an average particle size of 1.0 to 20 μm, more preferably 2.0 to 12.5 μm, and even more preferably 3.0 to 10 μm. If the average particle size is about the same as that of the abrasive particles, the distribution in the composite particles tends to be uniform, which is preferable as it reduces variations in grinding ability between the composite particles.

[0051] The ratio of the average particle size of the matrix particles to the average particle size of the composite fine 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 average particle size ratio is within the above range, the abrasive fine particles are excellently fixed when the composite particles are formed, the polishing rate can be more stably maintained, and the surface roughness of the resulting polished object tends to be further reduced.

[0052] The content of the matrix particles is preferably 10 to 98 mass %, more preferably 25 to 95 mass %, and even more preferably 50 to 90 mass %, of the total amount of the composite particles. When the content of the matrix particles is within the above range, the spacing between the abrasive particles increases, the contact points between the abrasive particles and the workpiece during polishing are reduced, the load per abrasive particle increases, and the grinding force increases, tending to improve the polishing rate.

[0053] 1.2.2.5. Auxiliary particles The auxiliary particles are not particularly limited, but examples thereof include auxiliary particles having an average particle diameter (Db) of 0.5 to 4.5 μm. By using such auxiliary particles, blocking of the composite fine particles is suppressed, and the polishing rate tends to be improved. The auxiliary particles may be located on the surface of the composite fine particles.

[0054] The components constituting such auxiliary particles are not particularly limited, but may include, for example, at least one selected from the group consisting of white alumina abrasive grains, brown alumina abrasive grains, black silicon carbide abrasive grains, green silicon carbide abrasive grains, barium sulfate, cerium oxide, etc. By using auxiliary particles containing such components, blocking of the composite fine particles tends to be suppressed, and the polishing rate tends to be improved. These auxiliary particles may be used alone or in combination of two or more types.

[0055] The average particle size of the auxiliary particles is preferably 0.5 to 4.5 μm, more preferably 0.7 to 4.0 μm, and even more preferably 0.9 to 3.5 μm. By having the average particle size within the above range, blocking of the composite fine particles can be effectively suppressed, the effect of improving the polishing rate can be easily obtained, and the surface roughness of the obtained polished object can be further reduced.

[0056] The content of the auxiliary particles is preferably 1.0 to 60.0 mass %, more preferably 10.0 to 55.0 mass %, and even more preferably 20 to 50.0 mass %, relative to the total amount of the composite fine particles. When the content of the auxiliary particles is within the above range, blocking of the composite fine particles can be effectively suppressed, the effect of improving the polishing rate can be easily obtained, and the surface roughness of the obtained polished object tends to be further reduced.

[0057] The content of the auxiliary particles is preferably 1.0 to 25.0 mass %, more preferably 2.0 to 22.0 mass %, and even more preferably 3.0 to 20.0 mass %, relative to the total amount of the polishing part. When the content of the auxiliary particles is within the above range, blocking of the composite fine particles can be effectively suppressed, the effect of improving the polishing rate can be easily obtained, and the surface roughness of the polished object obtained tends to be further reduced.

[0058] 1.2.3.Spacer particles Examples of spacer particles include inorganic particles with a Mohs hardness lower than that of the abrasive particles. The shape of the inorganic particles is not particularly limited, but examples include whisker-like, columnar, flaky, and scaly shapes. Furthermore, the components constituting such inorganic particles are not particularly limited, but examples include silicate minerals such as potassium aluminum silicate (Mohs hardness 6), diatomaceous earth (Mohs hardness 6-7), and wollastonite (Mohs hardness 4.5-5); 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). Among these, wollastonite is preferred from the viewpoints of the fixing power and self-dressing properties of the composite particles.

[0059] Wollastonite is a silicate mineral containing calcium silicate (CaSiO3) and is also known as wollastonite. In addition to calcium, wollastonite may also contain silicates of other metals, such as iron, manganese, sodium, and lithium. The use of wollastonite allows the polishing rate to be maintained more stably and the surface roughness of the resulting polished object to be reduced.

[0060] The average particle size of the spacer particles is 5.0 to 20 μm, preferably 7.5 to 17.5 μm, and more preferably 10 to 15 μm. When the average particle size is within this range, when mixed with a resin, the viscosity is low and the flowability is high, resulting in excellent moldability. In addition, the disintegration of the polishing area is improved, the polishing rate is maintained, and scratches tend to be more suppressed.

[0061] The ratio of the average particle size of the composite fine particles to the average particle size of the spacer particles is preferably 1.5 to 10, more preferably 2.5 to 9.0, and even more preferably 3.5 to 8.0. When the ratio is 1.5 or more, the spacer particles can be densely packed around the composite abrasive grains, making it easier to fix the composite fine particles. When the ratio is 10 or less, the grinding force can be increased without being pressed into the polishing pad during polishing. By keeping the ratio within the above range, the surface quality of the polished object can be more stably maintained.

[0062] The aspect ratio of the spacer particles (average major axis diameter / average minor axis diameter) is 2.0 to 12, preferably 2.5 to 10, and more preferably 3.0 to 7.0. When the aspect ratio (average major axis diameter / average minor axis diameter) is within the above range, appropriate self-dressing properties are obtained, the polishing rate can be more stably maintained, and the surface roughness of the resulting polished object is further reduced. The method for measuring the aspect ratio of the spacer particles is not particularly limited, but it can be calculated from photographs taken with an electron microscope.

[0063] The content of the spacer particles is preferably 20 to 70 mass %, more preferably 23 to 65 mass %, and even more preferably 25 to 60 mass %, relative to the total amount of the polishing part. When the content of the spacer particles is within the above range, new composite fine particles can continue to appear due to the self-dressing property of the spacer particles, which tends to stabilize the polishing rate and further reduce the surface roughness of the polished object.

[0064] The ratio of the spacer particle content to the composite particle content is preferably 1.0 to 22.5, more preferably 1.1 to 17.5, and even more preferably 1.2 to 12.5. When the ratio of the spacer particle content to the composite particle content is within the above range, the spacing between the composite particles becomes appropriate, the load on the composite particles is easily equalized, the polishing rate can be maintained more stably, and the surface roughness of the resulting polished object tends to be reduced.

[0065] 1.3.Adhesive layer The polishing pad of this embodiment may further include an adhesive layer on the opposite side of the substrate from the polishing portion for attaching the polishing pad to the polishing platen of a polishing machine. The adhesive layer may contain an adhesive or pressure-sensitive adhesive used in conventionally known polishing pads.

[0066] 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, silicone adhesives, etc. The adhesive layer may also be, for example, double-sided tape.

[0067] 2. Manufacturing method of polishing pad The method for manufacturing a polishing pad of this embodiment includes a firing step of firing a composite microparticle precursor containing diamond abrasive grains and matrix particles to obtain composite microparticles, a curing step of curing a curable composition containing a resin and the composite microparticles to obtain a polishing part, and a bonding step of bonding the surface of the polishing part opposite the polishing surface to a substrate, wherein the composite microparticles include hollow composite microparticles, and the content of the hollow composite microparticles is 5 to 40 mass% of the total amount of the composite microparticles.

[0068] 2.1. Firing process The firing step is a step of firing a composite microparticle precursor containing diamond abrasive grains and matrix particles to obtain composite microparticles. The firing step may include a composite microparticle precursor preparation step containing diamond abrasive grains and matrix particles. The composite microparticle precursor preparation step may include a hollow composite microparticle precursor preparation step and a solid composite microparticle precursor preparation step. In the firing step, the composite microparticle precursor obtained by the composite microparticle precursor preparation step described below is fired to thermally decompose the binder resin in the composite microparticle precursor, and fuse and appropriately bond the matrix particles together.

[0069] In the firing step, in addition to the composite particle precursor containing diamond abrasive grains and matrix particles, the above-mentioned auxiliary particles may also be included and fired. By including the auxiliary particles, blocking between the composite particle precursors can be suppressed.

[0070] The firing temperature in the firing step is preferably equal to or higher than the deformation point of the matrix particles. If the firing temperature is equal to or higher than the deformation point of the matrix particles, the matrix particles tend to fuse together and bond appropriately, which tends to further improve the stability of the composite particles. If the firing temperature is too low, the matrix particles do not bond together, which reduces the strength of the composite particles and results in poor polishing performance when used in a polishing pad.

[0071] The firing temperature is preferably the deformation point of the matrix particle + 150 ° C or less, more preferably the deformation point of the matrix particle + 120 ° C or less, even more preferably the deformation point of the matrix particle + 100 ° C or less, and even more preferably the deformation point of the matrix particle + 80 ° C or less. The lower limit of the firing temperature is preferably equal to or higher than the deformation point of the matrix particle. When the firing temperature is equal to or lower than the deformation point of the matrix particle + 150 ° C, the composite particles tend to be prevented from bonding together, while the diamond abrasive grain retention force of the composite particles tends to be within a suitable range. In addition, if the firing temperature is too high, the composite particles will bond together and will need to be crushed after firing, which may cause the shape of the composite particles to become distorted, and may impair the abrasive grain retention force of the composite particles.

[0072] The firing temperature depends on the yield point of matrix particles, but is preferably 500 to 700 ° C, more preferably 530 to 670 ° C, even more preferably 550 to 650 ° C, and even more preferably 560 to 630 ° C. When the firing temperature is within the above range, it tends to be possible to suppress the bonding of composite particles, while making the diamond abrasive grain holding power of composite particles within a suitable range.In addition, if the firing temperature is too high, the composite particles will bond together and need to be crushed after firing, which will cause the shape of the composite particles to become distorted, and may cause the composite particles to lose their holding power of abrasive grains.

[0073] The firing time in the firing step is, for example, 0.5 to 30 hours, and may be adjusted appropriately to obtain the desired composite fine particles.

[0074] The atmosphere in the firing step is not particularly limited, but is preferably an air atmosphere. In an air atmosphere, the matrix particles tend to fuse together and bond appropriately, and the variation in the crushing strength of the composite microparticles tends to be stabilized.

[0075] The atmosphere in the firing step is not particularly limited, but is preferably an open system. In this specification, an open system refers to a system in which the firing container is not sealed and the air atmosphere, which is the firing atmosphere, can flow in and out. The firing apparatus may be either a static firing furnace or a fluidized firing furnace. When a static firing furnace is used, the material to be fired is fired in a container such as a sheath. In this case, a temperature difference occurs between the part where the composite particles and the sheath come into contact and the center part of the composite particles, or between the composite particles in contact with the firing atmosphere and the composite particles not in contact with the firing atmosphere, which makes it easy for a difference in thermal history to occur. Therefore, a moderate variation occurs in the thermal history of the composite particles, and the crushing strength of the composite particles can be set within a suitable range. The crushing strength can be adjusted to a suitable range by adjusting the firing time.

[0076] 2.1.1. Composite particle precursor production process The composite particle precursor preparation step may be a step of mixing diamond abrasive grains, matrix particles, a binder resin, a dispersant, and a solvent to prepare a composite particle precursor composition, and then granulating the composite particle precursor. The composite particle precursor preparation step may include a hollow composite particle precursor preparation step and a solid composite particle precursor preparation step.

[0077] As the binder resin, a resin that can bind diamond abrasive grains and matrix particles and can be thermally decomposed by the following firing process is preferred.Water-soluble resin is more preferred, and as such a resin, a general-purpose binder can be used.For example, dextrin, polyvinyl alcohol, polyethylene glycol, polyacrylic acid, and polyacrylamide can be mentioned, and dextrin is preferred.In addition, these binder resins can be used alone or in combination of two or more.

[0078] The dispersant is not particularly limited, but examples thereof include quaternary ammonium salts, polycarboxylic acid surfactants, and maleic anhydride surfactants.

[0079] Examples of the solvent (dispersion liquid containing the binder resin) include water and alcohols such as methanol and isopropanol, and water is preferred. These solvents may be used alone or in combination of two or more.

[0080] In addition to the above components, other additives may be blended into the composite fine particle precursor composition. Examples of other additives include deflocculants (dispersants) and surfactants. These additives may be used alone or in combination of two or more.

[0081] The method for granulating the composite particle precursor composition is not particularly limited, but may include a method using a spray dryer such as a spray dryer. In this method, the precursor composition is sprayed into heated air, and the solvent (dispersion liquid) is evaporated to obtain precursor particles. The granulation conditions are not particularly limited, and can be appropriately set depending on the desired composite particles.

[0082] 2.1.1.1. Hollow composite particle precursor production process The hollow composite particle precursor preparation process may be a process of mixing diamond abrasive grains, matrix particles, a binder resin, a dispersant, and a solvent to prepare a hollow composite particle precursor composition, and then granulating the hollow composite particle precursor.

[0083] The solid content of the hollow composite particle precursor composition is not particularly limited, but is preferably 5 to 40%, more preferably 10 to 35%, even more preferably 15 to 30%, and particularly preferably 15 to 25%. When the solid content is within the above range, hollow composite particles tend to be able to be produced.

[0084] The method for granulating the hollow composite fine particle precursor composition is not particularly limited, but includes a method using a spray dryer such as a spray drier, and granulation using a spray drier is preferred.

[0085] The inlet temperature of the spray dryer can be set appropriately depending on the solids concentration of the hollow composite particle precursor composition and is not particularly limited, but is preferably 130 to 310° C., more preferably 140 to 300° C., and even more preferably 150 to 290° C. By setting the inlet temperature higher within the above range, liquid components such as water tend to volatilize rapidly, forming hollow structures inside and enabling more efficient granulation of the hollow composite particle precursor.

[0086] The outlet temperature of the spray dryer can be appropriately set depending on the solids concentration of the hollow composite particle precursor composition, and is not particularly limited, but is preferably 80 to 160° C., more preferably 85 to 155° C., and even more preferably 90 to 150° C. When the outlet temperature is within the above range, the hollow composite particle precursor tends to be granulated more efficiently.

[0087] 2.1.1.2. Preparation process of solid composite particle precursor The solid composite microparticle precursor preparation process may be a process of mixing diamond abrasive grains, matrix particles, a binder resin, a dispersant, and a solvent to prepare a solid composite microparticle precursor composition, and then granulating the solid composite microparticle precursor.

[0088] The solid content of the solid composite particle precursor composition is not particularly limited, but is preferably 40 to 80%, more preferably 45 to 75%, even more preferably 50 to 70%, and particularly preferably 55 to 65%. When the solid content is within the above range, solid composite particles tend to be able to be produced.

[0089] The method for granulating the solid composite fine particle precursor composition is not particularly limited, but includes a method using a spray dryer such as a spray drier, and granulation using a spray drier is preferred.

[0090] The inlet temperature of the spray dryer can be appropriately set depending on the solid content concentration of the solid composite particle precursor composition, and is not particularly limited, but is preferably 100 to 270° C., more preferably 110 to 260° C., and even more preferably 120 to 250° C. When the inlet temperature is within the above range, liquid components such as water gradually volatilize, and the solid composite particle precursor tends to be granulated more efficiently.

[0091] The outlet temperature of the spray dryer can be appropriately set depending on the solid content concentration of the solid composite particle precursor composition, and is not particularly limited, but is preferably 70 to 150° C., more preferably 75 to 135° C., and even more preferably 80 to 120° C. When the outlet temperature is within the above range, the solid composite particle precursor tends to be granulated more efficiently.

[0092] 2.2.Curing process The curing step is a step of obtaining a polishing part by curing a curable composition containing a resin and composite fine particles.

[0093] 2.2.1. Curable composition The curable composition is not particularly limited as long as it contains a resin and composite fine particles, and examples thereof include a photocurable composition containing a photopolymerization initiator and a polymerizable compound, a thermosetting composition containing a thermal polymerization initiator and a polymerizable compound, a UV-curable resin, a curable composition containing a two-component mixed curable resin, etc. Furthermore, the curable composition may contain a crosslinking agent having two or more polymerizable functional groups, etc., as necessary.

[0094] The polymerizable compound is not particularly limited, but examples thereof include (meth)acrylate, epoxy (meth)acrylate, urethane (meth)acrylate, and polyester (meth)acrylate.

[0095] The photopolymerization initiator is not particularly limited, but examples thereof include phosphine oxide compounds, benzophenone compounds, acetophenone compounds, and thioxanthone compounds. The thermal polymerization initiator is not particularly limited, but examples thereof include azo compounds such as 2,2'-azobisbutyronitrile, and peroxides such as benzoyl peroxide (BPO).

[0096] The thermosetting resin is not particularly limited, but examples thereof include urethane resin, unsaturated polyester resin, alkyd resin, phenol resin, epoxy resin, acrylic resin, urea resin, and formaldehyde resin.

[0097] The UV-curable resin is not particularly limited, but for example, a prepolymer with a number-average molecular weight of about 1,000 to 10,000 is suitable, and examples of materials include acrylic (methacrylic) esters, their urethane-modified products, thiocol-based materials, etc., and a reactive diluent or organic solvent can be used depending on the application. Furthermore, the two-component mixed curable resin is not particularly limited, but for example, prepolymers with different physical properties can be used.

[0098] The curable composition may contain components other than the resin, the composite fine particles, and the polymerization initiator, such as the filler and auxiliary particles described above.

[0099] 2.2.2.Curing method The method for curing the curable composition is not particularly limited, but examples thereof include photocuring, thermal curing, etc. The resulting polished portion has some of the composite fine particles exposed on the surface and the remaining composite fine particles bonded with the resin.

[0100] 2.3.Joining process The bonding step is a step of bonding the surface of the polishing part opposite the polishing surface to the substrate. The bonding method is not particularly limited, and the bonding step may be included in the curing step, or the polishing part and the substrate may be bonded by attaching the curable composition to the substrate and curing the curable composition, or the surface of the polishing part opposite the polishing surface that has been cured in advance may be bonded to the substrate via an adhesive.

[0101] The method for adhering the curable composition onto the substrate is not particularly limited, and examples thereof include a gravure coater method, a small-diameter gravure coater method, a reverse roll coater method, a transfer roll coater method, a kiss coater method, a die coater method, a screen printing method, a spray coating method, an embossing roll method, a transfer method, etc. Among these, the screen printing method or the transfer method is preferred from the viewpoints of ease of forming a complex concavo-convex pattern and productivity.

[0102] In the screen printing method, for example, a plate with an opening pattern corresponding to the convex portions is prepared, gaps are formed on a PET sheet serving as the substrate layer, the plate is placed, and the abrasive layer material is placed on the plate. A moderate amount of pressure is applied to the squeegee, and the abrasive layer material is pressed against the openings in the plate while the squeegee is moved, extruding and printing the abrasive layer material. The abrasive layer material is then cured to obtain a polishing pad consisting of a patterned abrasive layer on the substrate layer. In the transfer method, for example, a transfer mold with recesses corresponding to the convex portions is prepared, and the abrasive layer material is filled into this transfer mold. The filled abrasive layer material is then bonded to a substrate such as a PET sheet or acrylic sheet serving as the substrate layer via an adhesive. The abrasive layer material is then cured by irradiating it with light from above the PET sheet, and the sheet is then peeled off from the transfer mold, and if necessary, the convex portions are irradiated with light again to harden it, thereby obtaining a polishing pad consisting of a patterned abrasive layer on the substrate layer.

[0103] The method may further include a step of bonding the substrate on which the polishing portion is disposed to another substrate. The surface of the substrate opposite to the surface on which the polishing portion is disposed is bonded to the other substrate via an adhesive. The type of adhesive used is not particularly limited, and may be a liquid adhesive, double-sided tape, or adhesive tape made by processing an adhesive into a tape shape. Examples of liquid adhesives include curing adhesives such as photocuring resins, thermosetting resins, and moisture-curing resins, solvent-volatilizing adhesives, and hot-melt adhesives.

[0104] The adhesive can be applied by any conventionally known method, such as printing, typically screen printing, spray application, or application with a roller or brush.

[0105] The type of adhesive used to bond the surface of the pre-cured abrasive portion opposite the abrasive surface to the substrate is not particularly limited, and any of the above-mentioned adhesives may be used as appropriate.

[0106] 2.4.Other processes The method for producing a polishing pad of this embodiment may include other processes as necessary. For example, it may include a process of volatilizing and removing at least a portion of the volatile components in the curable composition before the curing process. Furthermore, it may include a process of removing a portion of the curable composition or the polishing portion before and / or after the curing process to form a desired uneven pattern. Examples of the removal method include cutting.

[0107] 3. Manufacturing method of polished products The method for producing a polished product of this embodiment is not particularly limited as long as it includes a polishing step of polishing an object to be polished using the polishing pad. The polishing step may be a primary lapping step (rough lapping), a secondary lapping step (finish lapping), or a polishing step, or may be a step that combines two or more of these steps. In addition, a coolant may be used in the polishing.

[0108] The polished object is not particularly limited, but examples thereof include materials such as semiconductor devices and electronic components, particularly thin substrates (polished objects) such as Si substrates (silicon wafers), SiC (silicon carbide) substrates, GaN (gallium nitride) substrates, GaAs (gallium arsenide) substrates, sapphire substrates, glass, and substrates for hard disks and LCDs (liquid crystal displays). Among these, the method for manufacturing a polished product of this embodiment is suitable for manufacturing magnetic disks such as hard disk drives, glass substrates used as base materials for reflective masks used in lithography using EUV light, glass materials for LCD substrates and cover glasses of mobile terminals such as smartphones and tablets, sapphire substrates for LEDs, and difficult-to-cut materials such as SiC (silicon carbide) substrates, GaN (gallium nitride) substrates, and GaAs (gallium arsenide) substrates.

[0109] 3.1. Polishing process The polishing step is a step of polishing an object to be polished using the polishing pad in the presence of a coolant. The polishing method may be any conventionally known method, and is not particularly limited.

[0110] In this polishing method, a polishing pad is first mounted in a predetermined position on a polishing apparatus. During this mounting, the polishing pad is fixed to the polishing apparatus via the adhesive layer. Then, a workpiece held on a holding platen, which is positioned opposite the polishing pad as a polishing surface, is pressed against the polishing surface, and the polishing pad and / or holding platen are rotated while supplying coolant from outside. This reduces polishing resistance and removes polishing debris due to the action of the coolant supplied between the polishing pad and the workpiece, while polishing the workpiece surface (surface to be polished). [Example]

[0111] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0112] [Preparation Example 1] (Preparation of hollow composite particles) A composite particle precursor composition with a solids concentration of 20% was prepared by mixing 4 parts by weight of dextrin (manufactured by Tokai Dextrin), 80 parts by weight of purified water, 11.2 parts by weight of glass frit, and 4.8 parts by weight of diamond powder with an average particle diameter of 4 μm. The mixture was then spray-dried using a spray dryer at a discharge flow rate of 1.5 L / min, an inlet temperature of 280°C, an outlet temperature of 140°C, and a spindle rotation speed of 10,000 rpm to form a composite particle precursor. The composite particle precursor and white alumina (manufactured by Fujimi Co., Ltd., average particle diameter 3 μm) were then mixed in a 6:4 ratio and placed in an open-top container. The mixture was then fired at 590°C for 2 hours to obtain composite microparticles with an average particle diameter of 40 μm. Scanning electron microscopy (SEM) of the cross-sections of the resulting composite microparticles confirmed that the particles had hollow interiors and were hollow composite microparticles. The shell thickness of the hollow composite microparticles was 8 to 12 μm.

[0113] [Preparation Example 2] (Preparation of solid composite particles) A composite particle precursor composition with a solids concentration of 60% was prepared by mixing 12 parts by weight of dextrin (manufactured by Tokai Dextrin), 40 parts by weight of purified water, 1 part by weight of additive Cerna D-735 (manufactured by Chukyo Yushi), 42 parts by weight of glass frit, and 5 parts by weight of diamond powder with an average particle diameter of 4 μm. The mixture was then spray-dried using a spray dryer at a discharge flow rate of 1.5 L / min, an inlet temperature of 220°C, an outlet temperature of 90°C, and a spindle rotation speed of 10,000 rpm to form a composite particle precursor. Subsequently, the composite particle precursor and white alumina (manufactured by Fujimi Co., Ltd., average particle diameter 3 μm) were mixed in a 6:4 ratio, placed in an open-top container, and calcined at 590°C for 2 hours to obtain composite microparticles with an average particle diameter of 40 μm. Scanning electron microscopy (SEM) of the cross-sections of the resulting composite microparticles confirmed that the particles had a solid structure and were solid composite microparticles.

[0114] Example 1 (Preparation of Curable Composition) A precursor composition was prepared by mixing 96.9 parts by mass of a mixture (SR368D manufactured by Sartomer Corporation) of trimethylolpropane triacrylate:tris(2-hydroxyethyl)isocyanurate triacrylate = 70:30 (mass ratio), 1.6 parts by mass of a dispersant (Solsperse 32000 manufactured by Lubrizol Japan Co., Ltd.), 1.0 part by mass of a photopolymerization initiator (Irgacure 819 manufactured by BASF Japan Ltd.), and 0.5 parts by mass of a photosensitizer (Anthracure (registered trademark) UVS-581 manufactured by Kawasaki Chemical Industries, Ltd.).

[0115] Next, 5 parts by mass of composite microparticles having a blending ratio of hollow composite microparticles to solid composite microparticles of 35:65 (mass%), 37 parts by mass of the precursor composition, and 58 parts by mass of wollastonite (K-400, manufactured by Keiwa Fine Material Co., Ltd., average particle size 18.6 μm, aspect ratio 6) were mixed to prepare a curable composition.

[0116] (Preparation of polishing pads) The obtained curable composition was poured into a moldable silicone intaglio plate having a rectangular prism-shaped recess with a depth of 1 mm, a cavity opening dimension of 3.0 mm × 3.0 mm, a recess bottom dimension of 2.4 mm × 2.4 mm, and a spacing of 1 mm between adjacent openings. A single-sided tape was attached so that the upper surface of the curable composition and the adhesive layer of the single-sided tape were in contact, and the curable composition was cured by irradiating ultraviolet light from above with an ultraviolet irradiator. The obtained cured product (abrasive part) was then removed from the mold, and a 1 mm thick acrylic substrate was bonded to the ultraviolet-irradiated surface via double-sided tape. The surface that had been in contact with the silicone intaglio plate was then irradiated with ultraviolet light using an ultraviolet irradiator and heated in a dryer at 90 ° C for 12 hours, obtaining a polishing pad of Example 1 with a diameter of 300 mm.

[0117] [Example 2, Comparative Examples 1 and 2] A polishing pad was obtained in the same manner as in Example 1, except that the blending ratio of the hollow composite particles and the solid composite particles was changed to the blending ratio shown in Table 1.

[0118] [Average particle size of diamond abrasive grains and composite microparticles] The average particle size (d50%) at which the cumulative value from the smallest diameter in the cumulative volumetric particle size distribution reached 50% of the total was measured in 10 seconds using a laser diffraction particle size distribution analyzer "Microtrac MT3300EXII" manufactured by Microtrac Bell Co., Ltd. The refractive index used during the measurement was 1.61, and the refractive index of the medium (deionized water) was 1.333.

[0119] [Crushing strength] Five particles were randomly selected from the obtained hollow composite particles or solid composite particles, and each particle was compressed at a loading rate of 51.8527 mN / sec using a microcompression tester (Shimadzu Corporation: MCT-510) and an indenter (Shimadzu Corporation: FLAT200) to measure the test force P (mN) at the time of fracture. The crushing strength (Cs) was measured in accordance with JIS R1639-5:2007 and was calculated from the test force P (mN) and the average particle diameter (d50%) of the composite particles using the following formula (where π is the circumference constant). The average crushing strength for the five particles is shown in Table 1. Crushing strength (Cs)=2.48×P / πd 2

[0120] [Grinding test] A glass grinding test was carried out on the polishing pads of each of the Examples and Comparative Examples under the following test conditions, and the surface roughness of the glass and the polishing rate after the test were measured. (Grinding conditions) Testing machine: Friction and wear testing machine Speedfam tabletop polishing machine (plate size 305mmφ) Dresser: WA whetstone #1000 Dressing time: 5 to 20 minutes Load: 200g / cm 2 Rotation speed: 80 rpm Time: 10 minutes / batch x 7 batches Coolant: Subrelve 9016 (Chemetall) 10 times diluted aqueous solution Fluid volume: 30mL / min Grinding material: Glass (50mm x 50mm)

[0121] (Surface roughness Sa of the workpiece) The surface roughness Sa of the surface of the workpiece after grinding was measured using an optical interferometer (manufactured by Canon, trade name "Zygo NewView 5010"). (Evaluation criteria) ○: Glass surface roughness Sa is less than 50 nm ×: Glass surface roughness Sa is 50 nm or more

[0122] (removal rate, removal rate stability) The polishing rate represents the amount of polishing per minute, and was calculated from the loss in the mass of the glass before and after polishing. The removal rates of the 7th batch and the 3rd batch were measured, and the stability was calculated based on the following formula. Polishing rate stability (%)=(polishing rate for 7th batch of glass−polishing rate for 3rd batch of glass) / polishing rate for 7th batch of glass×100 The polishing rate stability was evaluated according to the following criteria. (Polishing rate evaluation standard) 〇:20mg / min or more ×: Less than 20 mg / min (Polishing rate stability evaluation standard) ○: Less than 10% ×: 10% or more

[0123] [Table 1]

[0124] As described above, the polishing pad of the present invention contains hollow composite microparticles in the polishing portion, and the content of the hollow composite microparticles is 5 to 40 mass% relative to the total amount of composite microparticles, thereby showing a stable polishing rate, good surface roughness of the polished object, and high planarization accuracy.

[0125] On the other hand, in Comparative Example 1, where the content of hollow composite particles was 40% by mass or more relative to the total amount of composite particles, the polishing rate decreased and the polishing rate became unstable, possibly due to the influence of hollow composite particles that fell off the polishing pad during the dressing process.Furthermore, in Comparative Example 2, where the content of hollow composite particles was 5% by mass or less, the surface roughness of the polished object deteriorated, possibly due to poor self-dressing ability. [Industrial Applicability]

[0126] The polishing pad of the present invention has industrial applicability as a polishing pad suitable for lapping and polishing optical materials, semiconductor devices, glass substrates for hard disks, sapphire substrates for LEDs, and difficult-to-cut materials such as SiC (silicon carbide) substrates, GaN (gallium nitride) substrates, and GaAs (gallium arsenide) substrates. [Explanation of symbols]

[0127] 10... Polishing pad, 11... Base material, 12... Polishing portion, 14... Composite fine particles, 15... Resin

Claims

1. A substrate and an abrasive portion disposed on the substrate, the polishing portion includes a resin and composite fine particles, The composite microparticles include diamond abrasive grains, the composite particles include hollow composite particles, The content of the hollow composite fine particles is 5 to 40 mass% based on the total amount of the composite fine particles. Polishing pad.

2. the composite particulates further comprise solid composite particulates; The crushing strength (Cs 1 ) and the crushing strength (Cs 2 ) The difference between the above is 40.0 to 100.0 MPa, The polishing pad of claim 1 .

3. The hollow composite fine particles have an average particle size of 20 to 100 μm. The polishing pad of claim 1 .

4. The thickness of the shell of the hollow composite fine particles is 5 to 35 μm. The polishing pad of claim 1 .

5. The average particle size of the diamond abrasive grains is 3 to 9 μm. The polishing pad of claim 1 .

6. The polishing portion has a convex portion. The polishing pad of claim 1 .

7. a firing step of firing a composite microparticle precursor containing diamond abrasive grains and matrix particles to obtain composite microparticles; a curing step of curing a curable composition containing a resin and the composite fine particles to obtain a polishing part; a joining step of joining a surface of the polishing part opposite to the polishing surface to a substrate, the composite particles include hollow composite particles, The content of the hollow composite fine particles is 5 to 40 mass% based on the total amount of the composite fine particles. A method for manufacturing a polishing pad.

8. A method for polishing an object to be polished using the polishing pad according to any one of claims 1 to 6, Manufacturing method for polished products.

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