Polishing composition, polishing method using polishing composition, and mold production method using polishing composition

Abstract

To provide a polishing composition enabling quick removal of scratches while achieving a high polishing rate without impairing surface quality.SOLUTION: A polishing composition comprises abrasive grains having a Mohs hardness of 8 or more and a dispersion medium, wherein the abrasive grains have two or more peaks at different particle diameters in a particle size distribution on a volume basis as measured by a pore electrical resistance method, and the abrasive grain concentration is more than 0.5 mass% and less than 3.5 mass%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polishing composition, a polishing method using the polishing composition, and a method for manufacturing a mold using the polishing composition. [Background technology]

[0002] Various materials, such as metals, glass, ceramics, resins, and diamonds, require surface smoothing depending on their applications. To smooth the surfaces of these various materials, polishing is performed using hard abrasive grains with high Mohs hardness, such as diamond. For example, metals with a three-dimensional structure (3D shape) used as molds for pressing, forging, casting, die-casting, plastics, glass, rubber, powder metallurgy, etc., are polished after cutting by grinding with a grindstone and sandpaper, and then finished with a paste of hard abrasive grains (e.g., diamond). This removes scratches from the metal surface and produces a smooth surface. For example, Patent Document 1 discloses a diamond paste containing oil, metal soap, and diamond particles. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-66384 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, many companies have been faced with the challenge of reducing production times and fierce price competition due to the shortening of product life cycles, and are therefore faced with the challenge of cost improvement. In this context, there is a demand for a polishing composition that can shorten the polishing work time more than before.

[0005] Therefore, an object of the present invention is to provide a polishing composition that can quickly remove scratches and has a high polishing rate without deteriorating the surface quality. [Means for solving the problem]

[0006] In view of the above-mentioned problems, the present inventors have conducted extensive research and found that the above-mentioned problems can be solved by a polishing composition containing abrasive grains having a Mohs hardness of 8 or more and a dispersion medium, the abrasive grains having two or more maximum points of different particle diameters in a particle size distribution on a volume basis measured by a pore size resistivity method, and the abrasive grain concentration is more than 0.5 mass % and less than 3.5 mass %, thereby completing the present invention. [Effects of the Invention]

[0007] According to the present invention, there is provided a polishing composition which can quickly remove scratches and has a high removal rate without deteriorating the surface quality. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a conceptual diagram of the particle size distribution of abrasive grains contained in the polishing composition according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Modes for carrying out the present invention are described in detail below. The embodiments described herein are illustrative only to embody the technical concept of the present invention and are not intended to limit the present invention. Therefore, all other possible embodiments, methods of use, and operational techniques conceivable by those skilled in the art without departing from the spirit of the present invention are within the scope and spirit of the present invention, as well as the scope of the invention and its equivalents as set forth in the claims. The embodiments described herein can be arbitrarily combined to produce other embodiments. Furthermore, in this specification, the term "X to Y" indicating a range means "X or more and Y or less," and "weight" and "mass," "wt%" and "mass%," and "parts by weight" and "parts by mass" are treated as synonyms. In this specification, "A and / or B" encompasses both A and B, as well as both A and B. Unless otherwise specified, operations and measurements of physical properties are performed at room temperature (20°C to 25°C) and a relative humidity of 40% RH to 50% RH.

[0010] <Polishing composition> One aspect of the present invention is a polishing composition containing abrasive grains having a Mohs hardness of 8 or more and a dispersion medium, the abrasive grains having two or more maximum particle diameters in a particle size distribution on a volume basis measured by a pore electrical resistivity method, and the abrasive grain concentration being more than 0.5% by mass and less than 3.5% by mass. The polishing composition having such a configuration can quickly remove scratches on the surfaces of metals, semiconductor substrates, glass, ceramics, resins, diamonds, etc., especially on metal surfaces, and can polish objects to be polished at a high removal rate without deteriorating the surface quality.

[0011] In polishing compositions, abrasive grains exist as aggregates of particles with a particle size distribution. The inventors have found that a specific particle size distribution significantly contributes to the removal rate and the ease of eliminating scratches on the polished surface, and that this effect is even more pronounced at a specific abrasive grain concentration. Specifically, they have found that using a specific content of abrasive grains with a broad particle size distribution (i.e., abrasive grains with two or more maximum particle sizes in the volume-based particle size distribution measured by the pore size resistivity method) significantly improves the removal rate and scratch removal performance. While the details of this mechanism are unclear, it is speculated as follows: Small particles can enter gaps that form when large particles are lined up on the polishing surface. It is speculated that the polishing composition of this embodiment contains small particles with a broad particle size distribution, thereby forming a more densely packed state of the abrasive grains on the polishing surface as described above. However, if the amount of abrasive grains is too small, the distance between the abrasive grains on the polishing surface increases, preventing the formation of a densely packed state of the abrasive grains on the polishing surface. On the other hand, if the amount of abrasive grains is too large, the abrasive grains will overlap with each other on the polishing surface, forming a dense layer of abrasive grains. This abrasive grain layer becomes thicker depending on the amount of abrasive grains. As the abrasive grain layer becomes thicker, it becomes more prone to collapse. Therefore, it is speculated that abrasive grains in this state may make it difficult for mechanical force to be transmitted from the polishing pad to the polishing surface. As described above, the inventors speculate that the particle size distribution and abrasive grain concentration are related to the optimal packing state of the abrasive grains and the significant application of mechanical force from the polishing pad to the polishing surface via the abrasive grains. Therefore, it is believed that by containing abrasive grains with a specific particle size distribution at a specific concentration, the abrasive grains can apply a stronger mechanical force to the polishing surface, allowing for efficient polishing of the polishing surface and rapid removal of scratches on the polishing surface.

[0012] The above mechanism is based on speculation, and the present invention is not limited to the above mechanism in any way.

[0013] Each component contained in the polishing composition according to this embodiment will be described below.

[0014] [Abrasive grain] The polishing composition according to this embodiment contains abrasive grains with a Mohs hardness of 8 or more. The abrasive grains have the effect of mechanically polishing an object to be polished. Here, the Mohs hardness is measured by a method in which standard minerals ranging from hardness 1 to 10 are set, the standard material is rubbed against a material to be measured, and the hardness is measured based on the presence or absence of scratches. The standard materials used for Mohs hardness are talc for Mohs hardness 1, gypsum for Mohs hardness 2, calcite for Mohs hardness 3, fluorite for Mohs hardness 4, apatite for Mohs hardness 5, orthoclase for Mohs hardness 6, quartz for Mohs hardness 7, topaz for Mohs hardness 8, corundum for Mohs hardness 9, and diamond for Mohs hardness 10.

[0015] Examples of abrasive grains having a Mohs hardness of 8 or higher include tungsten carbide (Mohs hardness 8), zirconium boride (Mohs hardness 8), aluminum nitride (Mohs hardness 8), aluminum oxides such as sintered alumina and fused alumina (Mohs hardness 9), titanium nitride (Mohs hardness 9), titanium carbide (Mohs hardness 9), tantalum carbide (Mohs hardness 9), zirconium carbide (Mohs hardness 9), chromium (Mohs hardness 9), aluminum boride (Mohs hardness 9), boron carbide (Mohs hardness 9), silicon carbide (Mohs hardness 9), cubic boron nitride (cBN, Mohs hardness 9.5), boron carbide (Mohs hardness 9.5), titanium boride (Mohs hardness 9.5), and diamond (Mohs hardness 10). Among these, silicon carbide and diamond are preferably used. Silicon carbide is suitable for use when the object to be polished is a soft metal (e.g., aluminum alloy, titanium alloy, etc.), and is also advantageous from the viewpoint of cost. Diamond is more preferably used because of its excellent scratch-eliminating properties. When multiple types of abrasive grains are mixed, the Mohs hardness of the main component of the abrasive grains should be 8 or higher. Here, the main component of the abrasive grains refers to a component that accounts for more than 50% by mass of the abrasive grains. In one embodiment, in the polishing composition according to this embodiment, the abrasive grains having a Mohs hardness of 8 or higher account for preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and most preferably 95% by mass or more of the abrasive grains.

[0016] The abrasive grains used in this embodiment have two or more maximum points of different particle diameters in the particle size distribution on a volume basis measured by a pore electrical resistance method. The number of maximum points may be 2, 3, or 4 or more. In the polishing composition according to this embodiment, the number of maximum values ​​in the particle size distribution on a volume basis is preferably 2 or more and 5 or less, more preferably 2 or more and 4 or less, even more preferably 2 or 3, and particularly preferably 2.

[0017] The abrasive grains contained in the polishing composition according to this embodiment will be described in detail with reference to Fig. 1. Fig. 1 is a conceptual diagram showing the particle size distribution of the abrasive grains contained in the polishing composition according to this embodiment.

[0018] FIG. 1 shows, as an example, a conceptual diagram of the particle size distribution (volume basis) of abrasive grains having three maximum points. In the particle size distribution of FIG. 1, the vertical axis represents the relative particle number on a volume basis (hereinafter, "volume basis frequency") shown on a linear (normal) scale, and the horizontal axis represents the particle size (μm) on a logarithmic scale. Note that the particle size distribution of abrasive grains shown in FIG. 1 is merely a conceptual diagram and does not limit the abrasive grains contained in the polishing composition of this embodiment. In the particle size distribution of FIG. 1, particle sizes D1, D2, and D3 have maximum points with volume basis frequencies (i.e., peak heights) V1, V2, and V3, respectively.

[0019] Here, of two or more particle sizes having a maximum point in the volume-based particle size distribution, the smallest particle size is defined as Dmin and the largest particle size is defined as Dmax. That is, in the particle size distribution of FIG. 1, D1 corresponds to Dmin and D3 corresponds to Dmax. Furthermore, of two or more particle sizes having a maximum point in the volume-based particle size distribution, the particle size on the smaller side is defined as Ds, and the particle size on the larger side is defined as Dt, for the particle size having the largest volume-based frequency (i.e., peak height) and the particle size having the second largest volume-based frequency (i.e., peak height). That is, in the particle size distribution of FIG. 1, D1 corresponds to Ds, and D2 corresponds to Dt. The volume-based frequencies of particle sizes Dmin, Dmax, Ds, and Dt are defined as Vmin, Vmax, Vs, and Vt, respectively. In the particle size distribution of FIG. 1, D1 is Dmin and Ds.

[0020] For example, when there are two maximum points in the particle size distribution on a volume basis, Dmin is Ds and Dmax is Dt.

[0021] In addition, if the difference in particle size between adjacent maximum points in the particle size distribution is within 0.05 μm, the adjacent maximum points are not treated as separate maximum points, but are regarded as a single peak together, and the particle size with the largest volume-based frequency among them is treated as the maximum point.

[0022] In this specification, the particle size distribution of abrasive grains is based on the capillary electrical resistance method, specifically the International Standard ISO13319:2021 Determination of particle size distributions—Electrical sensing zone method. Examples of particle size and measuring devices include the measuring devices described in the Examples. Measurements based on the International Standard ISO (ISO13319:2021) use apertures (capillary tubes) with diameters corresponding to the particle diameter. When the maximum points in the particle size distribution of abrasive grains are far apart and not all of the maximum points can be detected using a single aperture, two or more apertures can be used to detect all of the maximum points.

[0023] The abrasive grains used in the polishing composition of this embodiment have a particle size distribution in which the ratio of the smallest particle size (Dmin) to the largest particle size (Dmax) among two or more maximum particle sizes (i.e., the ratio of Dmin to Dmax) Dmin / Dmax is preferably 0.05 or more, more preferably 0.1 or more, even more preferably 0.2 or more, particularly preferably 0.3 or more, and most preferably 0.4 or more. Furthermore, the Dmin / Dmax in the particle size distribution of the abrasive grains is preferably 0.9 or less, more preferably 0.85 or less, even more preferably 0.8 or less, particularly preferably 0.7 or less, and most preferably 0.6 or less. That is, the Dmin / Dmax in the particle size distribution of the abrasive grains is preferably 0.05 or more and 0.9 or less, more preferably 0.1 or more and 0.85 or less, even more preferably 0.2 or more and 0.8 or less, particularly preferably 0.3 or more and 0.7 or less, and most preferably 0.4 or more and 0.6 or less. When the Dmin / Dmax of the abrasive grains is within the above range, the particles tend to be packed more densely, and the desired effects of the present invention are more effectively achieved. In one embodiment, the Dmin / Dmax of the abrasive grains is 0.1 or more and 0.9 or less.

[0024] The ratio Vmin / Vmax of Vmin to Vmax is not particularly limited, but is preferably 0.01 or more, more preferably 0.05 or more, even more preferably 0.1 or more, particularly preferably 0.2 or more, and most preferably 0.25 or more. Also, Vmin / Vmax is preferably 5.0 or less, more preferably 3.5 or less, even more preferably 3.0 or less, particularly preferably 2.5 or less, and most preferably 2.0 or less. When the Vmin / Vmax of the abrasive grains is within the above range, the particles tend to be packed more densely, and the desired effects of the present invention are more effectively achieved.

[0025] In one embodiment, the abrasive grains preferably have a ratio Vs / Vt of 3.5 or less, where Vs is the volume-based frequency of the smaller grain size (Ds) and Vt is the volume-based frequency of the larger grain size (Dt) among the maximum grain size points in the grain size distribution. The Vs / Vt ratio in the grain size distribution of the abrasive grains is preferably 0.05 or more, more preferably 0.1 or more, even more preferably 0.2 or more, particularly preferably 0.25 or more, and most preferably greater than 0.25. Furthermore, the Vs / Vt ratio in the grain size distribution of the abrasive grains is preferably 5.0 or less, more preferably 3.5 or less, even more preferably 3.0 or less, particularly preferably 2.5 or less, and most preferably 2.0 or less. When the Vs / Vt ratio of the abrasive grains is within the above range, the particles tend to be packed more densely, thereby further enhancing the desired effects of the present invention.

[0026] The Dmin value of the abrasive grains is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1.0 μm or more, particularly preferably 1.1 μm or more, even more preferably 1.5 μm or more, and most preferably 2.0 μm or more. The Dmin value of the abrasive grains is not particularly limited, but is preferably 5.0 μm or less, more preferably 4.0 μm or less, even more preferably 3.5 μm or less, particularly preferably 3.0 μm or less, and most preferably 2.9 μm or less. When the Dmin value of the abrasive grains is within the above range, the mechanical action of the particles is enhanced, and the desired effects of the present invention are more effectively achieved. In one embodiment, the Dmin value of the abrasive grains is 0.3 μm or more and less than 3.0 μm. Furthermore, when there are two maximum points in the particle size distribution, the Dmin value of the abrasive grains is preferably 0.4 μm or more and 2.5 μm or less, and more preferably 1.0 μm or more and 2.3 μm or less. When the particle size distribution has three or more maximum points, the Dmin value of the abrasive grains is preferably 0.3 μm or more and 2.9 μm or less, more preferably 1.0 μm or more and 2.9 μm or less, and even more preferably 2.0 μm or more and 2.9 μm or less. When the Dmin of the abrasive grains is within the above range, the mechanical action of the particles is increased, and the desired effects of the present invention are more effectively achieved.

[0027] The Dmax value of the abrasive grains is preferably 1.0 μm or more, more preferably 1.5 μm or more, even more preferably 1.8 μm or more, particularly preferably 2.0 μm or more, and most preferably greater than 2.0 μm. The Dmax value of the abrasive grains is not particularly limited, but is preferably 9.0 μm or less, more preferably 8.5 μm or less, even more preferably 8.0 μm or less, particularly preferably 7.5 μm or less, and most preferably 7.0 μm or less. When the Dmax of the abrasive grains is within the above range, the mechanical action of the particles is enhanced, and the desired effects of the present invention are more effectively achieved. In one embodiment, the Dmax value of the abrasive grains is 3.0 μm or more and 6.5 μm or less. Furthermore, when there are two maximum points in the particle size distribution, the Dmax value of the abrasive grains is preferably 3.5 μm or more and 5.5 μm or less, and more preferably 3.8 μm or more and 5.0 μm or less. When the particle size distribution has three or more maximum points, the Dmax value of the abrasive grains is preferably 3.5 μm or more and 8.5 μm or less, and more preferably 4.0 μm or more and 8.0 μm or less. When the Dmax of the abrasive grains is in the above range, the mechanical action of the particles is increased, and the desired effects of the present invention are more effectively achieved.

[0028] When the maximum value of Ds of the abrasive grains is 2, Ds = Dmin, and therefore the above-mentioned Dmin value can be applied as Ds. When the maximum value is 3 or more, the Ds value of the abrasive grains is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1.0 μm or more, particularly preferably 1.1 μm or more, even more preferably 1.5 μm or more, and most preferably 2.0 μm or more. The Ds value of the abrasive grains is not particularly limited, but is preferably 5.0 μm or less, more preferably 4.0 μm or less, even more preferably 3.5 μm or less, particularly preferably 3.0 μm or less, and most preferably 2.9 μm or less. When the Ds of the abrasive grains is within the above range, the mechanical action of the particles is increased, and the desired effects of the present invention are more effectively achieved.

[0029] When the maximum value of Dt of the abrasive grain is 2, Dt = Dmax, and therefore the above-mentioned Dmax value can be applied as Dt. When the maximum value is 3 or more, the Dt value of the abrasive grain is not particularly limited, but is preferably 1.0 μm or more, more preferably 1.5 μm or more, even more preferably 1.8 μm or more, particularly preferably 2.0 μm or more, and most preferably greater than 2.0 μm. The Dt value of the abrasive grain is not particularly limited, but is preferably 9.0 μm or less, more preferably 8.5 μm or less, even more preferably 8.0 μm or less, particularly preferably 7.5 μm or less, and most preferably 7.0 μm or less. When the Dt of the abrasive grain is within the above range, the mechanical action of the particles is increased, and the desired effects of the present invention are more effectively achieved.

[0030] As long as the abrasive grains have two or more maximum points with different particle sizes, one type may be used alone, or two or more types may be mixed to have two or more maximum points. In addition, the abrasive grains to be used may be commercially available products or synthetic products.

[0031] Here, for abrasive grains having two or more maximum points of different particle size, synthesis conditions may be adjusted so that the particle size distribution has two or more maximum points of different particle size, or natural abrasive grains or artificial abrasive grains may be adjusted to the desired size (particle size distribution). For example, after producing the artificial abrasive grains or after obtaining commercially available products, they may be pulverized using a ball mill, airflow pulverization, or the like to adjust to the desired size. Furthermore, the pulverized abrasive grains may be classified using a sieve or the like to obtain abrasive grains of the desired size (particle size distribution), or classified abrasive grains may be mixed to obtain abrasive grains of the desired size (particle size distribution).

[0032] When the abrasive grains are diamond, the diamond may be, for example, natural diamond or artificial diamond, and artificial diamond is preferred. There is no particular limitation on the artificial diamond, and artificial diamonds synthesized by known methods such as high-pressure high-temperature synthesis (HPHT), chemical vapor deposition (CVD), and detonation (detonation) can be used. In addition, the artificial diamond may be a single crystal diamond or a polycrystalline diamond, and a mixture of single crystal diamond and polycrystalline diamond can also be used. Single crystal diamond is preferred from the viewpoint of cost. In addition, polycrystalline diamond is preferred from the viewpoint of scratch removal.

[0033] Examples of commercially available diamond products include those manufactured by Kemet Japan, Technorise, Tomei Diamond, Opticanics, Nakanishi, PUREON, and Nagase Polishing Equipment.

[0034] The content (concentration) of abrasive grains in the polishing composition is more than 0.5% by mass and less than 3.5% by mass, based on the total mass of the polishing composition. If the content of abrasive grains is 0.5% by mass or less, it is difficult to form the desired abrasive grain arrangement (densely packed state) on the polishing surface, resulting in a decrease in the polishing rate and inability to quickly remove surface scratches. If the content of abrasive grains is 3.5% by mass or more, it is difficult to form the desired abrasive grain arrangement (densely packed state) on the polishing surface, or even if the desired abrasive grain arrangement is formed, mechanical force is difficult to transmit, resulting in a decrease in the polishing rate and inability to quickly remove surface scratches. The content (concentration) of abrasive grains in the polishing composition is preferably 0.7% by mass or more and 3.0% by mass or less, more preferably 1.0% by mass or more and 2.8% by mass or less, even more preferably 1.3% by mass or more and 2.7% by mass or less, and particularly preferably 2.0% by mass or more and 2.5% by mass or less, based on the total mass of the polishing composition. When the content of the abrasive grains is within the above range, a sufficient polishing rate can be obtained and scratches on the surface can be quickly eliminated.

[0035] In the present invention, the abrasive grains may be only abrasive grains having a Mohs hardness of 8 or more, such as diamond, or may be combined with other abrasive grains. The other abrasive grains may be abrasive grains having a Mohs hardness of less than 8. Examples of the abrasive grains to be combined include boron nitride, boron carbide, silicon carbide, fused alumina, ceria, and silica.

[0036] The particle size distribution and content of abrasive grains in a polishing composition may be measured by isolating the abrasive grains, for example, as follows: In this case, for example, a 25-fold amount of a mold cleaner (e.g., NIC mold cleaner: Daizo Nichimori Division, a cleaner mainly composed of isohexane) is dissolved in the polishing composition as a solvent at 60 to 70°C, the abrasive grains are precipitated, the supernatant is removed, and the abrasive grain components are extracted. This process is repeated three times, and then the same operation is repeated three times using ethanol as a solvent, thereby isolating the abrasive grains.

[0037] [Dispersion medium] The polishing composition according to this embodiment contains a dispersion medium. The dispersion medium is a component for dispersing abrasive grains. The dispersion medium may be in any state, such as liquid, solid, or gel, but is preferably liquid at room temperature (25°C). For example, when a liquid dispersion medium is used, the polishing composition containing abrasive grains and the dispersion medium becomes an abrasive grain dispersion. When a solid or gel dispersion medium is used, or when the viscosity of the abrasive grain dispersion is increased by adding a thickener or the like to the abrasive grain dispersion, the polishing composition containing abrasive grains and the dispersion medium becomes an abrasive grain paste. Therefore, the polishing composition according to this embodiment includes both an abrasive grain dispersion and an abrasive grain paste. Hereinafter, unless otherwise specified, the abrasive grain dispersion is also considered to include an abrasive grain paste.

[0038] Examples of dispersion media include water; hydrophilic organic solvents other than water that are miscible with water (e.g., acetone, acetonitrile, ethanol, methanol, isopropanol, glycerin, ethylene glycol, propylene glycol, polyoxyalkylene glycols (e.g., oxyalkylene homopolymers (polymers containing only one type of oxyalkylene group), oxyalkylene copolymers (copolymers containing two or more types of oxyalkylene groups), oxyalkylene alkyl ethers having a short-chain hydrophobic group, etc.); hydrophobic organic solvents (e.g., aliphatic hydrocarbon compounds such as n-pentane, cyclopentane, n-hexane, cyclohexane, n-heptane, methylcyclohexane, and n-octane; aromatic hydrocarbon compounds such as benzene, toluene, and xylene; fatty acids or salts thereof; oils and fats; saturated or unsaturated petroleum hydrocarbons such as liquid paraffin and olefins (excluding waxes); and waxes that are solid or semi-solid at room temperature (25°C), such as paraffin wax (also called solid paraffin) and Vaseline). The polyoxyalkylene alkyl ether having a short-chain hydrophobic group is, for example, a polyoxyalkylene alkyl ether having an alkyl ether having 1 to 10 carbon atoms. The polyoxyalkylene alkyl ether preferably has 1 to 8 carbon atoms, and more preferably has 1 to 6 carbon atoms.

[0039] In this specification, a liquid at room temperature (25°C) refers to a substance having a viscosity of, for example, 10,000 mPa·s or less at 25°C, and a solid or semi-solid substance at room temperature (25°C) refers to a substance having a viscosity of more than 10,000 mPa·s at 25°C. Hereinafter, a semi-solid substance is included in the solid substance. Viscosity is measured using a rotational viscometer.

[0040] In the polyoxyalkylene glycol used as a dispersion medium, the oxyalkylene group is preferably one or more selected from an oxyethylene group and an oxypropylene group. That is, the oxyalkylene group constituting the oxyalkylene homopolymer, the oxyalkylene copolymer, and the polyoxyalkylene alkyl ether having a short chain length hydrophobic group is preferably one or more selected from an oxyethylene group and an oxypropylene group. The average number of moles of the oxyalkylene group added is preferably 2 or more and 30 or less, more preferably 4 or more and 20 or less.

[0041] Examples of oxyalkylene homopolymers and oxyalkylene copolymers used as dispersion media include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene glycol-polypropylene glycol random copolymers, polyethylene glycol-polytetramethylene glycol random copolymers, polypropylene glycol-polytetramethylene glycol random copolymers, polyethylene glycol-polypropylene glycol-polytetramethylene glycol random copolymers, polyethylene glycol-polypropylene glycol block copolymers, polypropylene glycol-polyethylene glycol-polypropylene glycol triblock copolymers, and polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymers.

[0042] Examples of polyoxyalkylene alkyl ethers having a short chain length hydrophobic group used as a dispersion medium include polyoxyalkylene monoalkyl ethers such as polyethylene glycol monomethyl ether, polypropylene glycol monomethyl ether, polytetramethylene glycol monomethyl ether, polyethylene glycol-polypropylene glycol monomethyl ether, polyethylene glycol monoethyl ether, polypropylene glycol monoethyl ether, polytetramethylene glycol monoethyl ether, polyethylene glycol-polypropylene glycol monoethyl ether, polyethylene glycol monopropyl ether, polypropylene glycol monopropyl ether, polytetramethylene glycol monopropyl ether, polyethylene glycol-polypropylene glycol monopropyl ether, polyethylene glycol monobutyl ether, polypropylene glycol monobutyl ether (polyoxypropylene glycol monobutyl ether), polytetramethylene glycol monobutyl ether, polyethylene glycol-polypropylene glycol monobutyl ether, polyethylene glycol monopentyl ether, polypropylene glycol monopentyl ether, polyethylene glycol monohexyl ether, polypropylene glycol monohexyl ether, polyethylene glycol monooctyl ether, polypropylene glycol monooctyl ether, polyethylene glycol monononyl ether, polypropylene glycol monononyl ether, polyethylene glycol monodecyl ether, and polypropylene glycol monodecyl ether;Polyoxyalkylene dialkyl ethers such as polyethylene glycol dimethyl ether, polypropylene glycol dimethyl ether, polytetramethylene glycol dimethyl ether, polyethylene glycol-polypropylene glycol dimethyl ether, polyethylene glycol diethyl ether, polypropylene glycol diethyl ether, polytetramethylene glycol diethyl ether, polyethylene glycol-polypropylene glycol diethyl ether, polyethylene glycol dipropyl ether, polypropylene glycol dipropyl ether, polytetramethylene glycol dipropyl ether, polyethylene glycol-polypropylene glycol dipropyl ether, polyethylene glycol dibutyl ether, polypropylene glycol dibutyl ether, polypropylene glycol dihexyl ether, polypropylene glycol dihexyl ether, polyethylene glycol dioctyl ether, polypropylene glycol dioctyl ether, polyethylene glycol dinonyl ether, polypropylene glycol dinonyl ether, polyethylene glycol didecyl ether, and polypropylene glycol didecyl ether; and the like.

[0043] The polishing composition according to this embodiment may contain a fatty acid or a salt thereof as a dispersion medium. The fatty acid is preferably a linear or branched fatty acid having from 8 to 30 carbon atoms, more preferably a linear or branched fatty acid having from 10 to 26 carbon atoms, and even more preferably a linear or branched fatty acid having from 12 to 22 carbon atoms. The fatty acid may be either a saturated or unsaturated fatty acid. When the fatty acid is in the form of a salt (i.e., a fatty acid salt), examples of the cation species constituting the fatty acid salt include alkali metal salts such as lithium, sodium, and potassium, and alkaline earth metal salts such as magnesium, calcium, strontium, and barium. Hereinafter, the fatty acid or its salt will also be referred to as "fatty acid (salt)."

[0044] Examples of fatty acids or salts thereof include capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, 12-hydroxystearic acid, undecylenic acid, isostearic acid, linoleic acid, linolenic acid, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), behenic acid, erucic acid, tall acid, and salts thereof. One fatty acid (salt) may be used alone, or two or more may be used in combination.

[0045] In the present invention, among these, from the viewpoint of ensuring that the entire polishing composition contributes efficiently to polishing, it is preferable that the polishing composition contains one or more fatty acids or salts thereof selected from the group consisting of lauric acid, oleic acid, myristic acid, palmitic acid, stearic acid, linoleic acid, and salts thereof. Furthermore, since the polishing composition is liquid at room temperature, it is preferable that the polishing composition contains one or more fatty acids or salts thereof selected from the group consisting of oleic acid, linoleic acid, and salts thereof. When a fatty acid (salt) that is solid at room temperature is used as the dispersion medium, it is preferable to heat the fatty acid (salt) to above its melting point to make it liquid, and then mix it with the abrasive grains. When a fatty acid (salt) that is liquid at room temperature is used as the dispersion medium, an abrasive grain dispersion can be obtained by mixing the abrasive grains with the dispersion medium.

[0046] In the present invention, a solid fatty acid (salt) (i.e., a dispersion medium such as lauric acid, myristic acid, palmitic acid, stearic acid, or a salt thereof) can disperse abrasive grains while also improving the viscosity of the polishing composition, and therefore also acts as a thickener, as described below.

[0047] The polishing composition according to this embodiment may contain a fat or oil as a dispersant. The fat or oil serves as a dispersant for dispersing abrasive grains. Examples of fat or oil that can be preferably used include safflower oil, grape oil, evening primrose oil, walnut oil, sunflower oil, soybean oil, cottonseed oil, corn oil, wheat germ oil, rosehip oil, borage seed oil, rice bran oil, sesame oil, peanut oil, adlay oil, rapeseed oil, linseed oil, palm oil, olive oil, tung oil, castor oil, coconut oil, and hydrogenated oils thereof. One type of fat or oil may be used alone, or two or more types may be used in combination.

[0048] In the present invention, from the viewpoint of ensuring that the polishing composition as a whole contributes efficiently to polishing, it is preferable that the polishing composition contain one or more oils selected from the group consisting of rice bran oil, peanut oil, olive oil, and palm oil.

[0049] In the present invention, fats and oils that are solid at room temperature (e.g., hydrogenated oils such as hydrogenated castor oil, hydrogenated coconut oil, and hydrogenated jojoba oil) can disperse abrasive grains while also improving the viscosity of the polishing composition, and therefore also act as a thickener, as described below.

[0050] The polishing composition according to this embodiment may contain a saturated or unsaturated petroleum hydrocarbon (excluding wax) as a dispersion medium. In the present invention, from the viewpoint of the polishing composition as a whole efficiently contributing to polishing, it is preferable that the polishing composition contains liquid paraffin.

[0051] The polishing composition according to this embodiment may contain wax as a dispersion medium. Examples of waxes that can be preferably used include paraffin wax, microcrystalline wax, carnauba wax, montan wax, and polyethylene wax. One type of wax may be used alone, or two or more types may be used in combination.

[0052] In the present invention, from the viewpoint of efficiently contributing to polishing by the entire polishing composition, it is preferable that the polishing composition contains wax. Waxes that are solid at room temperature (e.g., paraffin wax, Vaseline, etc.) can disperse abrasive grains while also improving the viscosity of the polishing composition, and therefore also act as a thickener, as described below.

[0053] The content of the dispersion medium is preferably 5% by mass or more and 90% by mass or less, more preferably 10% by mass or more and 85% by mass or less, even more preferably 15% by mass or more and 80% by mass or less, particularly preferably 20% by mass or more and 75% by mass or less, and most preferably 25% by mass or more and 70% by mass or less, based on the total mass of the polishing composition. In one embodiment, the content of the dispersion medium may be 30% by mass or more and 98% by mass or less, 35% by mass or more and 95% by mass or less, or 40% by mass or more and 93% by mass or less, based on the total mass of the polishing composition. When the content of the dispersion medium is within the above range, a sufficient polishing rate can be obtained and surface scratches can be quickly eliminated. When two or more dispersion media are used, the content of the dispersion media is the total amount.

[0054] The dispersion medium may be either a hydrophilic organic solvent or a hydrophobic organic solvent depending on the application. Among these, from the viewpoint of diamond dispersibility, it is preferable to use a combination of a hydrophilic organic solvent and a hydrophobic organic solvent, and more preferable are polyoxyalkylene glycols (for example, oxyalkylene homopolymers, oxyalkylene copolymers, polyoxyalkylene alkyl ethers with short chain lengths of hydrophobic groups), fatty acids (salts), oils and fats, petroleum hydrocarbons (for example, liquid paraffin), and waxes (for example, paraffin wax). In one embodiment, the dispersion medium comprises one or more selected from the group consisting of polyoxyalkylene glycols (for example, polyoxyalkylene alkyl ethers with short chain lengths of hydrophobic groups), fatty acids (salts), oils and fats, petroleum hydrocarbons, and waxes. Furthermore, from the viewpoint of cleanability after polishing the object to be polished, hydrophilic organic solvents are preferred, oxyalkylene homopolymers (polyoxyalkylene glycols), oxyalkylene copolymers, and polyoxyalkylene alkyl ethers having short-chain hydrophobic groups are more preferred, and oxyalkylene homopolymers (polyoxyalkylene glycols) and polyoxyalkylene alkyl ethers having short-chain hydrophobic groups are even more preferred. In one embodiment, the dispersion medium contains, for example, one or more selected from oxyalkylene homopolymers, oxyalkylene copolymers, and polyoxyalkylene alkyl ethers having short-chain hydrophobic groups.

[0055] According to one embodiment, the polishing composition according to this aspect contains one or more dispersion media selected from the group consisting of polyoxyalkylene glycols, fatty acids (salts), petroleum hydrocarbons, and waxes. According to one embodiment, the polishing composition according to this aspect contains one or more components selected from the group consisting of polyoxyalkylene glycols (e.g., polyoxyalkylene alkyl ethers having short-chain hydrophobic groups) and fats and oils. According to one embodiment, the polishing composition according to this aspect contains one or more components selected from the group consisting of fatty acids (salts), petroleum hydrocarbons (e.g., liquid paraffin), and waxes. The content of these components (content (mass%) relative to the polishing composition) refers to the total amount, which is the content of the dispersion media. When the content of these components is within the above range, a sufficient polishing rate can be obtained and surface scratches can be quickly eliminated. When two or more dispersion media are used, the content of the dispersion media refers to the total amount.

[0056] In the polishing composition according to this embodiment, it is preferable that two or more dispersion media are used. When two or more dispersion media are used, they may be mixed and used simultaneously, or abrasive grains may be dispersed in a first dispersion medium to obtain an abrasive grain dispersion, and then a second dispersion medium may be added to the abrasive grain dispersion.

[0057] According to one embodiment, in the polishing composition of this embodiment, the first dispersion medium is one or more selected from the group consisting of polyoxyalkylene glycols (e.g., polyoxyalkylene alkyl ethers with short-chain hydrophobic groups), fats and oils, and petroleum hydrocarbons, and the second dispersion medium is one or more selected from the group consisting of fatty acids (salts) and waxes. In this case, the content of the first dispersion medium (total amount when two or more types are included) is preferably 30% by mass or more and 95% by mass or less, more preferably 35% by mass or more and 90% by mass or less, even more preferably 40% by mass or more and 85% by mass or less, particularly preferably 45% by mass or more and 80% by mass or less, and most preferably 50% by mass or more and 75% by mass or less, based on the total mass of the polishing composition. In this case, the content of the second dispersion medium (total amount when two or more types are included) is preferably 1% by mass or more and 65% by mass or less, more preferably 2% by mass or more and 60% by mass or less, even more preferably 3% by mass or more and 55% by mass or less, particularly preferably 5% by mass or more and 50% by mass or less, and most preferably 10% by mass or more and 45% by mass or less, based on the total mass of the polishing composition. When the contents of the first dispersion medium and the second dispersion medium are within the above ranges, a sufficient polishing rate can be obtained and surface scratches can be quickly eliminated. In addition, the composition is thickened to a paste-like state with a moderate viscosity, which has the effect of improving usability.

[0058] According to one embodiment, in the polishing composition of this form, the content of polyoxyalkylene glycol (e.g., polyoxyalkylene alkyl ether having a short chain length hydrophobic group) is preferably 30% by mass or more and 95% by mass or less, more preferably 35% by mass or more and 90% by mass or less, even more preferably 40% by mass or more and 85% by mass or less, particularly preferably 45% by mass or more and 80% by mass or less, and most preferably 50% by mass or more and 75% by mass or less, relative to the total mass of the polishing composition.

[0059] According to one embodiment, in the polishing composition of this form, the content of oils and fats is preferably 30 mass% or more and 95 mass% or less, more preferably 35 mass% or more and 90 mass% or less, even more preferably 40 mass% or more and 85 mass% or less, particularly preferably 45 mass% or more and 80 mass% or less, and most preferably 50 mass% or more and 75 mass% or less, relative to the total mass of the polishing composition.

[0060] According to one embodiment, in the polishing composition of this form, the content of petroleum hydrocarbons is preferably 30 mass% or more and 95 mass% or less, more preferably 35 mass% or more and 90 mass% or less, even more preferably 40 mass% or more and 85 mass% or less, particularly preferably 45 mass% or more and 80 mass% or less, and most preferably 50 mass% or more and 75 mass% or less, relative to the total mass of the polishing composition.

[0061] According to one embodiment, in the polishing composition of this form, the content of fatty acid (salt) is preferably 0.1 mass% or more and 30 mass% or less, more preferably 0.5 mass% or more and 28 mass% or less, even more preferably 1 mass% or more and 25 mass% or less, particularly preferably 2 mass% or more and 23 mass% or less, and most preferably 3 mass% or more and 20 mass% or less, relative to the total mass of the polishing composition.

[0062] According to one embodiment, in the polishing composition of this form, the wax content is preferably 0.1 mass% or more and 30 mass% or less, more preferably 0.5 mass% or more and 28 mass% or less, even more preferably 1 mass% or more and 25 mass% or less, particularly preferably 2 mass% or more and 23 mass% or less, and most preferably 3 mass% or more and 20 mass% or less, relative to the total mass of the polishing composition.

[0063] When a polishing composition is produced using a first dispersion medium and a second dispersion medium, the mass ratio of the first dispersion medium to the second dispersion medium (first dispersion medium:second dispersion medium) is preferably 30:70 to 99:1, more preferably 35:65 to 98:2, even more preferably 40:60 to 97:3, particularly preferably 50:50 to 96:6, and most preferably 60:40 to 95:5. In one embodiment, the mass ratio of the first dispersion medium to the second dispersion medium may be 65:35 to 95:5, 60:40 to 90:10, or 60:40 to 85:15.

[0064] According to one embodiment, a dispersion medium that is liquid at room temperature (25°C) (hereinafter referred to as the third dispersion medium) and a dispersion medium that is solid at room temperature (25°C) (hereinafter referred to as the fourth dispersion medium) are used in combination. When the third dispersion medium and the fourth dispersion medium are used to produce a polishing composition, the mass ratio of the third dispersion medium to the fourth dispersion medium (third dispersion medium:fourth dispersion medium) is preferably 1:99 to 99:1, more preferably 2:98 to 90:10, even more preferably 3:97 to 80:20, and most preferably 4:96 to 75:25. The fourth dispersion medium (solid at room temperature (25°C)) does not necessarily need to be contained as a dispersion medium.

[0065] [Other ingredients] The polishing composition according to this embodiment may contain, in addition to the abrasive grains and the dispersion medium, one or more other components selected from the group consisting of surfactants and thickeners.

[0066] Surfactants The polishing composition according to this embodiment may contain a surfactant, which acts as a dispersant to help the diamond disperse in the fatty acid (salt) or oil as a dispersing medium in the polishing composition.

[0067] The surfactant is not particularly limited, but examples thereof include cationic surfactants, anionic surfactants, amphoteric surfactants, nonionic surfactants, etc. Among these, nonionic surfactants are preferred from the viewpoints of foaming and dispersibility of abrasive grains.

[0068] Cationic surfactants can be classified into, for example, polyoxyethylene alkylamines, alkylalkanolamides, alkylamine salts, amine oxides, quaternary ammonium salts, tertiary amidoamine surfactants, etc. Specific examples of cationic surfactants include coconut amine acetate, stearyl amine acetate, lauryl dimethyl amine oxide, stearic acid dimethylaminopropylamide, alkyl trimethyl ammonium salts, alkyl dimethyl ammonium salts, alkyl benzyl dimethyl ammonium salts, etc.

[0069] Anionic surfactants that can be used in the present invention can be classified into, for example, sulfates, sulfonic acids, phosphoric acids, phosphonic acids, carboxylic acids, etc. Specific examples of anionic surfactants include alkyl sulfates, polyoxyethylene alkyl sulfates, polyoxyethylene alkyl sulfates, alkyl sulfates, alkyl ether sulfates, higher alcohol sulfates, alkyl phosphates, alkylbenzene sulfonic acids, α-olefin sulfonic acids, alkyl sulfonic acids, styrene sulfonic acids, alkyl naphthalene sulfonic acids, alkyl diphenyl ether disulfonic acids, polyoxyethylene alkyl ether acetates, polyoxyethylene alkyl ether phosphoric acids, polyoxyethylene alkyl phosphates, polyoxyethylene sulfosuccinic acids, alkyl sulfosuccinic acids, and salts of any of the above compounds. A specific example of an alkyl sulfonic acid is dodecyl sulfonic acid. Other examples of anionic surfactants include taurine surfactants, sarcosinate surfactants, isethionate surfactants, N-acyl acidic amino acid surfactants, quaternary ammonium salts of higher fatty acid salts, and acylated polypeptides.

[0070] Specific examples of amphoteric surfactants that can be used in the present invention include alkyl betaines, alkylamine oxides, etc. Specific examples of amphoteric surfactants include cocobetaine, lauramidopropyl betaine, cocamidopropyl betaine, sodium lauroamphoacetate, sodium cocoamphoacetate, coconut oil fatty acid amidopropyl betaine, lauryl betaine (lauryl dimethylaminoacetic acid betaine), etc.

[0071] The nonionic surfactant is not particularly limited, but examples thereof include surfactants having a polyoxyalkylene group, such as polyoxyalkylene adducts.Specific examples of the polyoxyalkylene adducts are not particularly limited, but include polyoxyalkylene alkyl ethers, polyoxyalkylene aryl ethers, polyoxyalkylene alkylamines, polyoxyalkylene fatty acid esters, polyoxyalkylene glycerin ether fatty acid esters, polyoxyalkylene sorbitan fatty acid esters, etc., each of which has a long chain length hydrophobic group.Among these, polyoxyalkylene fatty acid esters are preferred from the viewpoint of lubricity during polishing.

[0072] Examples of polyoxyalkylene alkyl ethers having a long chain hydrophobic group that are used as surfactants include polyoxyalkylene alkyl ethers having an alkyl group with more than 10 carbon atoms.

[0073] In surfactants having a polyoxyalkylene group, the oxyalkylene group constituting the polyoxyalkylene group is preferably one or more selected from an oxyethylene group and an oxypropylene group, more preferably an oxyethylene group. The average number of moles of oxyalkylene groups added is preferably 2 to 30, more preferably 4 to 20. The number of carbon atoms in the alkyl group in the polyoxyalkylene alkyl ether having a long-chain hydrophobic group is preferably 12 or more, more preferably 14 or more, even more preferably 16 or more, and preferably 30 or less, more preferably 20 or less, and even more preferably 18 or less. That is, the number of carbon atoms in the alkyl group in the polyoxyalkylene alkyl ether having a long-chain hydrophobic group is preferably 12 or more and 30 or less, more preferably 14 or more and 20 or less, and even more preferably 16 or more and 18 or less. The number of carbon atoms in the fatty acid residue in the polyoxyalkylene fatty acid ester is preferably 10 or more, more preferably 12 or more, even more preferably 14 or more, and preferably 22 or less, more preferably 20 or less, and even more preferably 18 or less. That is, the number of carbon atoms in the fatty acid residue in the polyoxyalkylene fatty acid ester is preferably 10 or more and 22 or less, more preferably 12 or more and 20 or less, and even more preferably 14 or more and 18 or less. The fatty acid residue may be saturated or unsaturated, and is preferably unsaturated.

[0074] Examples of polyoxyalkylene alkyl ether types include polyoxyethylene monoundecyl ether, polyoxyethylene monododecyl ether (polyoxyethylene monolauryl ether), polyoxyethylene didodecyl ether (polyoxyethylene dilauryl ether), polyoxyethylene monotetradecyl ether (polyoxyethylene monomyristyl ether), polyoxyethylene ditetradecyl ether (polyoxyethylene dimyristyl ether), polyoxyethylene monooleyl ether, polyoxyethylene dioleyl ether, etc. Examples of polyoxyalkylene aryl ether types include polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecyl phenyl ether, etc. Examples of polyoxyalkylene alkylamine types include polyoxyethylene laurylamine, polyoxyethylene stearylamine, polyoxyethylene oleylamine, etc. Examples of polyoxyalkylene fatty acid ester types include polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene distearate, polyoxyethylene monooleate, polyoxyethylene dioleate, etc. Examples of polyoxyalkylene glycerin ether fatty acid esters include polyoxyethylene glycerin monolaurate, polyoxyethylene glycerin ether monostearate, etc. Examples of polyoxyalkylene sorbitan fatty acid esters include polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopaltimate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, etc.

[0075] Further, examples of the polyoxyalkylene adducts include polyoxyethylene sorbitol trioleate, polyoxyethylene castor oil, and polyoxyethylene hydrogenated castor oil.

[0076] The nonionic surfactant preferably has an HLB of 1-10, more preferably 2-9, and even more preferably 4-8.

[0077] The molecular weight of the surfactant is not particularly limited, but is preferably less than 1,000, more preferably less than 500, and even more preferably less than 400. The molecular weight of the surfactant is preferably calculated from the chemical formula.

[0078] The surfactant may be a commercially available product or a synthetic product, and one type of surfactant may be used alone, or two or more types may be used in combination.

[0079] The content of the surfactant is not particularly limited, but is preferably 0.01% by mass or more and 25% by mass or less, more preferably 0.1% by mass or more and 23% by mass or less, even more preferably 1% by mass or more and 22% by mass or less, particularly preferably 2% by mass or more and 20% by mass or less, and most preferably 5% by mass or more and 18% by mass or less, based on the total mass of the polishing composition. In one embodiment, the content of the surfactant is 1% by mass or more and 17% by mass or less, or 2% by mass or more and 15% by mass or less, based on the total mass of the polishing composition. When the surfactant is contained within the above range, the abrasive grains are uniformly dispersed, thereby achieving a sufficient polishing rate and quickly eliminating surface scratches.

[0080] The polishing composition of this embodiment preferably contains a nonionic surfactant as a surfactant, more preferably a polyoxyalkylene fatty acid ester, and even more preferably a polyoxyalkylene fatty acid ester having a fatty acid having 12 to 22 carbon atoms.

[0081] In one embodiment, the polishing composition according to this embodiment contains a fatty acid (salt) as a dispersion medium and a polyoxyalkylene fatty acid ester as a surfactant. That is, in one embodiment, the polishing composition according to this embodiment contains a fatty acid (salt) and a polyoxyalkylene fatty acid ester. With this configuration, the polishing rate is improved while the scratch removal ability is further improved. More preferably, the polishing composition according to this embodiment contains a fatty acid (salt) having 12 to 22 carbon atoms and a polyoxyalkylene fatty acid ester having the fatty acid (salt) having 12 to 22 carbon atoms. In this case, the content of the fatty acid (salt) is preferably 0.5 to 25% by mass, more preferably 1 to 23% by mass, and even more preferably 2 to 20% by mass, relative to the total mass of the polishing composition. The content of the polyoxyalkylene fatty acid ester is preferably 0.1 to 20% by mass, more preferably 0.5 to 18% by mass, and even more preferably 1 to 15% by mass.

[0082] In one embodiment, the polishing composition of this embodiment contains one or more dispersing media selected from the group consisting of fatty acids (salts), oils and fats, and polyoxyalkylene alkyl ethers having short-chain hydrophobic groups, and a polyoxyalkylene fatty acid ester as a surfactant.

[0083] Thickener The polishing composition according to this embodiment may contain a thickener. The thickener has the effect of increasing the viscosity of the polishing composition and improving its stability. The thickener used in the present invention includes inorganic compounds that are solid at room temperature (25°C). Examples of such inorganic compounds include amorphous silica and bentonite, and examples of amorphous silica include silica gel, silica sol, precipitated silica, and fumed silica. Of these, amorphous silica is preferred as the thickener, with precipitated silica, silica gel, and fumed silica being more preferred, and fumed silica and precipitated silica being more preferred.

[0084] When an inorganic compound is used as a thickener, the inorganic compound may be added directly to the abrasive dispersion, or the inorganic compound may be dispersed in a dispersion medium and then the inorganic compound dispersion may be added to the abrasive dispersion.

[0085] Furthermore, as mentioned above, in the polishing composition of this embodiment, among the dispersion media, those that are solid at room temperature (25°C) (e.g., solid fatty acids (salts), solid oils and fats, wax, etc.) also act as thickeners. For this reason, in the examples described below, sodium stearate and paraffin wax (solid paraffin) are used as thickeners. When a solid dispersion medium (e.g., sodium stearate, wax, etc.) is used as a thickener, a paste abrasive composition can be prepared by heating the abrasive dispersion liquid to the melting point of the solid dispersion medium, adding the solid dispersion medium to the abrasive dispersion liquid, melting and stirring uniformly, and cooling to room temperature.

[0086] According to one embodiment, the dispersion medium is liquid at room temperature (25°C), and the thickener is solid at room temperature (25°C). Thus, according to one embodiment, in the present invention, solid fatty acids (salts) (e.g., lauric acid, myristic acid, palmitic acid, stearic acid or salts thereof, etc.), solid fats and oils, and waxes (e.g., paraffin wax, Vaseline) are also used as thickeners. In this case, the dispersion medium that is solid at room temperature (i.e., the thickener in this form) is preferably contained in an amount of 0.1% to 30% of the total mass of the polishing composition, more preferably 0.5% to 25%, even more preferably 1% to 20%, particularly preferably 3% to 15%, and most preferably 5% to 10%.

[0087] The content of the thickener is not particularly limited, but is preferably 0.1% by mass or more and 33% by mass or less, more preferably 0.5% by mass or more and 30% by mass or less, even more preferably 1% by mass or more and 27% by mass or less, particularly preferably 2% by mass or more and 25% by mass or less, and most preferably 5% by mass or more and 23% by mass or less, based on the total mass of the polishing composition. When the thickener is contained within the above range, a sufficient polishing rate can be obtained, and surface scratches can be quickly eliminated.

[0088] The polishing composition of this embodiment may contain other additives in any proportion as needed, in addition to the abrasive grains, dispersion medium (preferably at least one selected from polyoxyalkylene glycol, fatty acid (salt), oil, fat, petroleum hydrocarbon, and wax), surfactant, and thickener, as long as the effects of the present invention are not impaired. Examples of other additives include pH adjusters, polymeric compounds, antifungal agents (preservatives), antifoaming agents, dissolved gases, reducing agents, oxidizing agents, and alkanolamines. Known additives can be used as these other additives.

[0089] [Method for producing polishing composition] The method for producing a polishing composition according to this embodiment includes a step of dispersing abrasive grains in a dispersion medium (e.g., water, polyoxyalkylene glycol, fatty acid (salt), oil, petroleum hydrocarbon, wax, etc.). Specifically, the method for producing a polishing composition according to this embodiment includes the steps of: (a) adding abrasive grains and a surfactant to a first dispersion medium (e.g., polyoxyalkylene glycol, oil, and / or petroleum hydrocarbon) and mixing to obtain an abrasive grain dispersion; and (b) optionally adding a second dispersion medium (e.g., fatty acid (salt) and / or wax) and, if necessary, a thickener to the abrasive grain dispersion and mixing to obtain a polishing composition. Here, methods for mixing to obtain an abrasive grain dispersion or a polishing composition that can be used include ultrasound, a magnetic stirrer, a three-one motor, a homogenizer, etc. When mixing an abrasive grain dispersion, it is preferable to mix using ultrasound, and when mixing to obtain a polishing composition, it is preferable to mix using ultrasound or a three-one motor.

[0090] When using, for example, a fatty acid (salt) as a dispersant that is solid at room temperature, the fatty acid (salt) is heated to its melting point to become liquid, and then abrasive grains are added to the fatty acid (salt), stirred until uniform, and cooled to room temperature to produce a paste (abrasive grain dispersion). When a solid fatty acid (salt) acid is used as a thickener, a polishing composition in the form of a paste may be obtained using a solid fatty acid (salt) as a dispersant, or abrasive grains may be dispersed in a fatty acid (salt) that is liquid at room temperature to obtain an abrasive grain dispersion, and then the fatty acid (salt) that is solid at room temperature may be added to the abrasive grain dispersion. In this case, it is preferable to use a fatty acid (salt) that is solid at room temperature, which is heated to a temperature above the melting point of the fatty acid (salt) to become liquid before being added to the abrasive grain dispersion.

[0091] [Uses of polishing composition] The polishing composition according to the present invention is suitable for polishing metals, semiconductor substrates, glass, ceramics, resins, diamonds, etc., and is particularly suitable for polishing metals having a three-dimensional structure (metals having a three-dimensional shape). Examples of metals having a three-dimensional shape include molds.

[0092] That is, according to another aspect of the present invention, there is provided a polishing method for polishing a three-dimensional metal using the polishing composition. Also, according to another aspect of the present invention, there is provided a method for manufacturing a mold, which includes a step of polishing a mold using the polishing composition.

[0093] Examples of metals to be polished in this embodiment include pre-hardened steels such as carbon steel SC series for machine structures (e.g., S50C, etc.), chromium-molybdenum steel SCM series (e.g., P2RM, P3RMF, etc.), and NAK series (precipitation hardening type) (e.g., NAK80, etc.); quenched and tempered steels such as stainless steels (e.g., STAVAX, HPM38S, P12RM, etc.) and alloy tool steels (e.g., P9RM, D9RM1, NAK101, etc.); aging-treated steels; etc. Applications of dies made from these metals include dies for pressing, forging, casting, die-casting, plastics, glass, rubber, powder metallurgy, etc. Components that can be molded using these molds include steel plates, non-ferrous metals such as aluminum alloys and zinc alloys, glass materials, rubbers, plastics such as polypropylene, polystyrene, ABS resin, polycarbonate (PC), acrylic resins such as polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and fiber reinforced plastics (FRP).

[0094] Fields in which these molds are used include automobile parts, construction machinery parts, agricultural machinery parts, beverage containers, lighting fixture parts, footwear, mold bases, bumpers, home appliances, instrument panels, TV cabinets, headlamps, optical equipment, office equipment, smartphone / PC / camera housings, cosmetic bottles, lenses, optical discs, fiber-reinforced products, etc. The polishing composition of this embodiment can be used as a polishing composition for polishing molds used for molding when producing products in the various fields mentioned above.

[0095] Although the embodiments of the present invention have been described in detail, it is clear that this is for illustrative and exemplary purposes only and not for limitation, and that the scope of the present invention should be interpreted by the appended claims.

[0096] The present invention encompasses the following aspects and configurations.

[0097] [1] A polishing composition comprising abrasive grains having a Mohs hardness of 8 or more and a dispersion medium, wherein the abrasive grains have two or more maximum points of different particle diameters in a particle size distribution on a volume basis measured by a pore electrical resistance method, and the abrasive grain concentration is more than 0.5 mass% and less than 3.5 mass%; [2] The polishing composition according to the above [1], wherein the abrasive grains have a ratio Dmin / Dmax of the smallest grain size (Dmin) to the largest grain size (Dmax) among the two or more maximum grain sizes different from each other, of 0.1 or more and 0.9 or less; [3] The polishing composition according to [1] or [2] above, wherein the abrasive grains have a Vs / Vt ratio of 3.5 or less, where Vs is the volume-based frequency at the smaller grain size (Ds) of the two or more maximum grain sizes having the largest and second largest volume-based frequencies, and Vt is the volume-based frequency at the larger grain size (Dt) of the two or more maximum grain sizes; [4] The polishing composition according to any one of the above [1] to [3], wherein the abrasive grains have a Vmin / Vmax ratio of 3.5 or less, where Vmin is the volume-based frequency at the smallest grain size (Dmin) among the two or more maximum points having different grain sizes, and Vmax is the volume-based frequency at the largest grain size (Dmax); [5] The polishing composition according to any one of the above [1] to [4], wherein the abrasive grains are diamond; [6] The polishing composition according to [5] above, wherein the diamond is polycrystalline diamond; [7] The polishing composition according to any one of the above [1] to [6], wherein the dispersion medium is one or more selected from the group consisting of polyoxyalkylene glycols, fatty acids (salts), petroleum hydrocarbons, and waxes; [8] The polishing composition according to any one of the above [1] to [7], which contains one or more components selected from the group consisting of surfactants and thickeners; [9] The polishing composition according to [8] above, wherein the thickener is amorphous silica;

[10] The polishing composition according to any one of the above [1] to [9], further comprising a surfactant, wherein the surfactant is a polyoxyalkylene fatty acid ester;

[11] A polishing method for polishing a three-dimensional metal using the polishing composition according to any one of [1] to

[10] above;

[12] A method for producing a mold, comprising a step of polishing a mold with the polishing composition according to any one of [1] to

[10] above. [Example]

[0098] The present invention will be described in more detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. Unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass," respectively. In the following examples, unless otherwise specified, the operations were carried out under the conditions of room temperature (25°C) and a relative humidity of 40% RH or more and 50% RH or less.

[0099] [Preparation of Polishing Compositions A1 to A4 and B1 to B3] The abrasive grains used were the following single crystal diamonds (x) or (y). Single crystal diamond (x): Two maxima Dmax=4.59μm, Vmax=4.25 Dmin=2.01μm, Vmin=1.18 Single crystal diamond (y): One maximum point Dmax=4.39 μm, Vmax=5.56.

[0100] A diamond dispersion was prepared by uniformly stirring the single-crystal diamond (x) or (y) described above, a surfactant (polyoxyethylene oleate ester (also known as polyoxyethylene monooleate) (product name: Noigen® ES-99D (Dai-ichi Kogyo Seiyaku Co., Ltd.), HLB: 7.7), and a dispersion medium (at least one selected from the group consisting of higher fatty acid (oleic acid), polyoxyalkylene glycol (polyoxypropylene glycol monobutyl ether; Sanyo Chemical Industries, Ltd., product name: Newpol LB-625), and liquid paraffin). A thickener (at least one selected from the group consisting of fumed silica (product name: Aerosil® 200, Nippon Aerosil Co., Ltd., average primary particle size (D50): 12 nm), sodium stearate, and paraffin wax) was added to the diamond dispersion and uniformly kneaded to prepare polishing compositions A1-A5 and B1-B3. The types and amounts of each component contained in each polishing composition are as shown in Table 1.

[0101] [Measurement of diamond particle size distribution] The particle size distribution of the diamond was measured using a "Multisizer 4e" manufactured by Beckman Coulter, Inc. The aperture diameter was set to 20 μm.

[0102] [Evaluation of Polishing Composition] The resulting polishing compositions A1 to A5 and B1 to B3 were evaluated as follows. The evaluation results for the polishing compositions A1 to A5 and B1 to B3 are shown in Table 1.

[0103] [Polishing rate] The polishing rate of NAK80 was measured by polishing using the polishing composition under the following polishing conditions. The polishing rate was calculated by measuring the weight of the mold material before and after polishing, taking the difference as the removal amount, and dividing it by the polishing time. The polishing rate of polishing composition B2 was then set to 1.00, and the polishing rate ratio to polishing composition B2 was calculated. This operation was performed three times, and the average value was shown. The polishing rate of polishing composition B2 was 11 mg / min.

[0104] [Scratch removal time] NAK80 was polished with 2000-grit sandpaper and then polished with the polishing composition under the following polishing conditions. The surface was visually observed, and the time it took for the scratches caused by the 2000-grit sandpaper to disappear was recorded as the scratch removal time (minutes).

[0105] [Polishing conditions] Material: NAK80 Size: 60mm x 60mm x 5mm Polishing machine: Minitor MINIMO (registered trademark) ONE SERIES VER.2 M112GRAD Pad: Minitor φ30 felt (SA3103) Rotation speed: 1000 rpm

[0106] [Table 1]

[0107] As shown in Table 1 above, the polishing compositions of the Examples, which contain abrasive grains with two or more maximum points of different particle sizes and have an abrasive grain concentration of more than 0.5% by mass and less than 3.5% by mass, have high removal rates and short scratch-elimination times, demonstrating good polishing performance and enabling reductions in working time. On the other hand, the polishing compositions of the Comparative Examples, which contain abrasive grains with one maximum point and which contain abrasive grains with two or more maximum points of different particle sizes at a concentration of 0.5% by mass or less or 3.5% by mass or more, were found to have inferior removal rates and scratch-elimination times compared to the polishing compositions of the Examples.

Claims

1. The abrasive grains have a Mohs hardness of 8 or more, and a dispersion medium. the abrasive grains have two or more maximum points of different grain sizes in a grain size distribution on a volume basis measured by a pore electrical resistance method; The polishing composition has an abrasive concentration of more than 0.5 mass% and less than 3.5 mass%.

2. 2. The polishing composition according to claim 1, wherein the abrasive grains have a ratio Dmin / Dmax of the smallest grain size (Dmin) to the largest grain size (Dmax) among the two or more maximum points of different grain sizes, of 0.1 or more and 0.9 or less.

3. 3. The polishing composition according to claim 1, wherein the abrasive grains have a Vs / Vt ratio of 3.5 or less, where Vs is the volume-based frequency at the particle size (Ds) on the smaller particle size side and Vt is the volume-based frequency at the particle size (Dt) on the larger particle size side, among the two or more maximum particle sizes with different particle sizes.

4. 3. The polishing composition according to claim 1, wherein the abrasive grains have a Vmin / Vmax ratio of 3.5 or less, where Vmin is the volume-based frequency at the smallest grain size (Dmin) among the two or more maximum points of different grain sizes, and Vmax is the volume-based frequency at the largest grain size (Dmax).

5. 3. The polishing composition according to claim 1, wherein the abrasive grains are diamond.

6. 6. The polishing composition according to claim 5, wherein the diamond is a polycrystalline diamond.

7. 3. The polishing composition according to claim 1, wherein the dispersion medium is at least one selected from the group consisting of polyoxyalkylene glycols, fatty acids (salts), petroleum hydrocarbons, and waxes.

8. 3. The polishing composition according to claim 1, further comprising one or more components selected from the group consisting of surfactants and thickeners.

9. 9. The polishing composition according to claim 8, wherein the thickener is amorphous silica.

10. 3. The polishing composition according to claim 1, further comprising a surfactant, wherein the surfactant is a polyoxyalkylene fatty acid ester.

11. A polishing method for polishing a three-dimensional metal using the polishing composition according to claim 1 or 2.

12. A method for manufacturing a mold, comprising a step of polishing a mold with the polishing composition according to claim 1 or 2.

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