Abrasive sheet and polishing method

Abstract

To provide a polishing sheet which efficiently polishes a hard material such as a metal product and can form a smooth surface having less irregularity, and can form a uniform smooth surface even when repeatedly polishing the material with the same polishing surface.SOLUTION: A polishing sheet contains a base material, a plurality of three-dimensional elements that contain diamond abrasive grains and a binding material and constitute a polishing surface, and an intermediate layer that is provided between the base material and the three-dimensional elements and joins the base material and the three-dimensional elements. A ratio C2 / C1 of a content C2 of the diamond abrasive grains to a content C1 of the binding material is 0.05 to 1.5 by mass ratio.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a polishing sheet and a polishing method.

Background Art

[0002] Conventionally, various abrasives have been studied to form a smooth surface on metal products and the like. For example, Patent Documents 1 and 2 describe abrasives provided with a polishing portion having a three-dimensional shape.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to form a uniform smooth surface on an object to be polished, in the conventional abrasive, the polished surface obtained by polishing one object to be polished is not reused, and generally, the next object to be polished is polished with a new polished surface or a new abrasive.

[0005] An object of the present invention is to provide a polishing sheet and a polishing method that can efficiently polish an object to be polished to form a smooth surface with few irregularities, and can form a uniform smooth surface even when polishing is repeatedly performed on the same polished surface.

Means for Solving the Problems

[0006] One aspect of the present invention relates to a polishing sheet including a base material, a plurality of three-dimensional elements containing diamond abrasive grains and a binder and constituting a polishing surface, and an intermediate layer provided between the base material and the three-dimensional elements for joining the base material and the three-dimensional elements, wherein the ratio C2 / C1 of the content C2 of the diamond abrasive grains to the content C1 of the binder is 0.05 to 1.5 by mass ratio.

[0007] Another aspect of the present invention relates to a polishing method for polishing a plurality of objects to be polished using the polishing sheet, the method including a first polishing step of pressing the polishing surface of the polishing sheet against the object to be polished and sliding the polishing sheet and the object to be polished, and a reuse step of polishing another object to be polished using at least a part of the polishing surface used in the first polishing step.

Advantages of the Invention

[0008] According to the present invention, there is provided a polishing sheet capable of efficiently polishing an object to be polished to form a smooth surface with few irregularities and capable of forming a uniform smooth surface even when repeated polishing is performed on the same polishing surface. Further, according to the present invention, there is provided a polishing method capable of efficiently polishing an object to be polished using the polishing sheet.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0010] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same reference numerals are given to the same elements, and redundant descriptions are omitted. Further, the drawings are drawn with some exaggeration for easy understanding, and the dimensional ratios and the like are not limited to those described in the drawings.

[0011] (Polishing sheet) The polishing sheet according to the present embodiment includes a base material, diamond abrasive grains and a binder, a plurality of three-dimensional elements that constitute a polishing surface, and an intermediate layer provided between the base material and the three-dimensional elements to bond the base material and the three-dimensional elements.

[0012] In the present embodiment, the ratio C2 / C1 (mass ratio) of the content C2 of the diamond abrasive grains to the content C1 of the binder is 0.05 to 1.5.

[0013] The polishing sheet according to the present embodiment can efficiently polish a hard material such as a metal product to form a smooth surface with few irregularities, and can form a uniform smooth surface even when polishing is repeated (for example, 10 times or more) on the same polishing surface. When the ratio C2 / C1 exceeds 1.5, when polishing is repeated on the same polishing surface, the formed smooth surface gradually becomes rough, and it is difficult to form a uniform smooth surface. Further, when the ratio C2 / C1 is less than 0.05, when polishing is repeated on the same polishing surface, the polishing performance is greatly reduced, and it becomes difficult to remove irregularities.

[0014] The reason for the above effect is not necessarily clear. However, when the ratio C2 / C1 exceeds 1.5, a large amount of grinding occurs and a large amount of grinding debris is likely to be generated. Also, due to reasons such as the three-dimensional elements being rigid and the dischargeability of the grinding debris from the polishing surface being low, the grinding debris is likely to adhere to the polishing surface. This adhered grinding debris is considered to be one of the causes of the roughness of the smooth surface during repeated polishing. Further, when the ratio C2 / C1 is less than 0.05, due to the small amount of diamond abrasive grains, the decrease in polishing performance due to the wear of the diamond abrasive grains is significant, and it is considered that sufficient polishing performance cannot be maintained during repeated polishing. That is, when the ratio C2 / C1 is within the above range, the adhesion of the grinding debris to the polishing surface is suppressed, and since it is an amount of abrasive grains that can maintain sufficient polishing performance even during repeated polishing, it is considered that the above effect can be obtained.

[0015] Hereinafter, a preferred embodiment of the polishing sheet will be described in detail with reference to the drawings.

[0016] FIG. 1 is a cross-sectional view showing a preferred embodiment of the polishing sheet. The polishing sheet 10 shown in FIG. 1 includes a base material 11, three-dimensional elements 12 containing diamond abrasive grains and a binder, and an intermediate layer 13 disposed between the base material 11 and the three-dimensional elements 12 and bonding the three-dimensional elements 12 onto one surface of the base material 11.

[0017] Examples of the base material 11 include a paper base material, a cloth base material, a sponge base material, a resin film, a metal film, and the like.

[0018] Examples of the paper base material include kraft paper, impregnated paper, coated paper, synthetic paper, and the like. Also, examples of the cloth base material include cotton cloth, rayon cloth, polyester cloth, or blends thereof. Further, examples of the sponge base material include polyurethane foam, polyethylene foam, melamine foam, and the like.

[0019] The surface of the base material 11 that contacts the intermediate layer 13 is preferably smooth, and from the viewpoint of easily obtaining smoothness, it preferably includes a resin film and / or a metal film. Examples of the resin film include a polyester film, a polyimide film, a polyamide film, and the like. From the viewpoint of high thermal conductivity and expectable frictional heat dissipation, a metal foil is preferable as the metal film, and examples thereof include an aluminum foil and a copper foil. The base material 11 may be a laminate obtained by laminating a plurality of resin films, may be a laminate obtained by laminating a plurality of metal films, or may be a laminate including a resin film and a metal film.

[0020] The surface of the base material 11 on the side opposite to the intermediate layer 13 may be subjected to a surface treatment for the purpose of, for example, improving the adaptability to a polishing apparatus. Examples of the surface treatment include roughening treatment by sandblasting, formation of an anti-slip layer using an inorganic particle-containing resin, and application of an adhesive layer using a pressure-sensitive adhesive.

[0021] The thickness of the base material 11 is not particularly limited, and may be, for example, 15 μm or more, and may also be 60 μm or more. Further, the thickness of the base material 11 may be, for example, 500 μm or less, and may also be 350 μm or less. When the thickness of the base material 11 is increased, breakage of the base material during high-load polishing is significantly suppressed, and the stability of high-load polishing is improved. Further, when the thickness of the base material 11 is decreased, the followability to the object to be polished is further improved.

[0022] The Young's modulus of the base material 11 at 25°C is preferably 3.0×10 9 Pa or more. By having such a base material 11, it becomes easier to slide the polishing sheet 10 against the fixed hard material, and the polishing sheet 10 excellent in adaptability to high-load polishing is obtained.

[0023] From the viewpoint of more significantly obtaining the above effects, the Young's modulus of the base material 11 at 25°C is more preferably 3.5×10 9 Pa or more, and 3.8×10 9More preferably, it is Pa or higher. When the base material 11 is a metal film, the Young's modulus of the base material 11 at 25 °C may be even higher. For example, it may be 10×10 9 Pa or higher, or may be 20×10 9 Pa or higher.

[0024] The upper limit of the Young's modulus of the base material 11 at 25 °C is not particularly limited. From the viewpoint of processability into a roll-shaped product, the Young's modulus of the base material 11 at 25 °C is, for example, 250×10 9 Pa or less is preferable, and 150×10 9 Pa or less is more preferable. When the base material 11 is a resin film, the Young's modulus of the base material 11 at 25 °C may be even lower. For example, it may be 20×10 9 Pa or less, or may be 15×10 9 Pa or less.

[0025] In this specification, the Young's modulus of the base material indicates a value measured by a test on the tensile properties of the film in accordance with ISO 527-3.

[0026] The base material 11 preferably has an elongation at break of 200% or less. Such a base material 11 can fix the three-dimensional element 12 more firmly during high-load polishing, and the polishing performance tends to be further improved.

[0027] From the viewpoint of obtaining the above effects more significantly, the elongation at break of the base material 11 is more preferably 180% or less, and even more preferably 150% or less. When the base material 11 is a metal film, the elongation at break of the base material 11 may be even lower. For example, it may be 40% or less, or may be 30% or less.

[0028] The lower limit of the elongation at break of the base material 11 is not particularly limited. For example, it may be 1% or more, or may be 3% or more. When the base material 11 is a resin film, the elongation at break of the base material 11 may be even higher. For example, it may be 20% or more, or may be 40% or more.

[0029] In this specification, the elongation at break of the base material indicates a value measured in accordance with JIS K 7127.

[0030] The three-dimensional element 12 includes diamond abrasive grains (hereinafter also simply referred to as abrasive grains) for polishing the object to be polished and a binder for binding the abrasive grains. By the three-dimensional element 12, a convex portion in contact with the object to be polished and a concave portion not in contact with the object to be polished are formed on the polishing surface of the polishing sheet 10. That is, the three-dimensional element 12 in the polishing sheet 10 can be said to be an element provided such that the polishing surface has convex and concave portions.

[0031] The polishing sheet 10 has a plurality of three-dimensional elements 12, and the three-dimensional elements 12 are independent of each other. By having such a configuration, the plurality of three-dimensional elements 12 can follow the unevenness of the object to be polished during high-load polishing.

[0032] The average particle size of the abrasive grains may be appropriately selected according to the use of the polishing sheet 10. The average particle size of the abrasive grains may be, for example, 2 μm or more, preferably 5 μm or more, more preferably 7 μm or more, and still more preferably 9 μm or more. When the average particle size of the abrasive grains is large, it becomes easy to manufacture a polishing sheet that satisfies the ratio C2 / C1 described later. Further, the average particle size of the abrasive grains may be, for example, 100 μm or less, preferably 50 μm or less, and more preferably 30 μm or less.

[0033] In this specification, the average particle size of the polishing particles is the volume cumulative particle size D50 measured using laser diffraction / scattering particle size distribution measurement. The specific measurement conditions are as follows, but as long as those skilled in the art can understand that equivalent values can be obtained based on the same principle, the use of other measurement devices and conditions is not precluded. · Measuring device: Laser diffraction / scattering particle size distribution measuring device LA-920 (manufactured by Horiba, Ltd., Kyoto, Kyoto Prefecture) · Analysis software: LA-920 for Windows (registered trademark) · Amount of abrasive grains: 150 mg · Dispersion medium: 150 mL of ion-exchanged water ·Circulation speed (water agitation speed): Set value 15 ·Ultrasonic oscillation: Yes (using the built-in ultrasonic device in LA-920) ·Measurement temperature: Room temperature (25 °C) ·Relative humidity: 85% or less ·He-Ne laser light transmittance: 85% ·Tungsten lamp transmittance: 85% ·Relative refractive index: Set to 1.80 (relative refractive index of diamond: 1.81) ·Measurement time: 20 seconds ·Number of data acquisitions: 10 ·Particle size standard: Volume

[0034] The grit size is defined by JIS R-6001-2:2017 and may be, for example, #240 to #20000, preferably #400 to #2000.

[0035] The binder can be a matrix that disperses the abrasive grains. The binder may be, for example, a cured product of a thermosetting resin composition or a cured product of a photocurable resin composition.

[0036] The binder preferably has a Young's modulus at 25 °C of 1.0×10 9 Pa or more. According to such a binder, the shape of the three-dimensional element 12 can be sufficiently maintained even under high loads, and the polishing force on the object to be polished tends to be more significantly exhibited.

[0037] From the viewpoint of more significantly obtaining the above effects, the Young's modulus of the binder at 25 °C is more preferably 2.0×10 9 Pa or more, and even more preferably 4.0×10 9 Pa or more. The upper limit of the Young's modulus of the binder at 25 °C is not particularly limited and may be, for example, 20×10 9 Pa or less, or 15×10 9 Pa or less.

[0038] In the present specification, the Young's modulus of the binder is determined by performing dynamic viscoelastic measurement by bending vibration at a frequency of 1 Hz in accordance with ISO 6721-5 under the following conditions, and indicates the value of the complex elastic modulus calculated from the results of the measurement. (Measurement conditions) · Measuring device: Solids Analyzer RSA III manufactured by Rheometric Scientific · Measurement mode: Three Point Bending · Distance between support ends: 40 mm · Frequency: 1 Hz · Approximate dimensions of test piece: width 10 mm × length 50 mm × thickness 2 mm · Strain: 0.05%

[0039] In a preferred embodiment, the binder may contain a phenolic resin. Such a binder is likely to obtain the above-described preferred Young's modulus.

[0040] In another preferred embodiment, the binder may be a cured product of a resin composition containing an acrylic monomer. The acrylic monomer is a compound having at least one polymerizable group selected from the group consisting of an acryloyl group and a methacryloyl group. The above resin composition is cured by polymerization of the acrylic monomer to become a cured product constituting the binder.

[0041] In the above resin composition, 60% by mass or more of the acrylic monomer may be a polyfunctional monomer selected from the group consisting of tris(2-hydroxyethyl)isocyanurate triacrylate and tris(2-hydroxyethyl)isocyanurate diacrylate. Thereby, since a binder having a high compressive yield stress is formed, the binder can be deformed while maintaining the pressure applied to the polishing surface during high-load polishing, improving the adhesion to the hard material, and obtaining a high polishing force.

[0042] The content of the above polyfunctional monomer in the acrylic monomer is preferably 65% by mass or more, more preferably 85% by mass or more, may be 95% by mass or more, may be 99% by mass or more, or may be 100% by mass or more.

[0043] The above resin composition may further contain other acrylic monomers other than the above polyfunctional monomer. As the other acrylic monomers, those having a glass transition temperature of 25°C or higher in the homopolymer are preferred. Examples of the other acrylic monomers include, as monofunctional monomers, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, etc.; as difunctional monomers, tricyclodecanemethanol di(meth)acrylate, bisphenol A ethylene oxide-modified di(meth)acrylate, etc.; and as polyfunctional monomers, trimethylpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, ε-caprolactone-modified tris-(2-acryloxyethyl)isocyanurate, etc.

[0044] The content of the acrylic monomer in the above resin composition may be, for example, 90% by mass or more, preferably 95% by mass or more, more preferably 99% by mass or more, based on the total amount of the solid content in the resin composition. The upper limit of the content of the acrylic monomer in the above resin composition is not particularly limited.

[0045] The above resin composition may further contain a polymerization initiator for initiating the polymerization of the acrylic monomer. Examples of the polymerization initiator include thermal polymerization initiators and photopolymerization initiators, and among these, a photopolymerization initiator for initiating free radical polymerization is preferred. Examples of the photopolymerization initiator include, as the intramolecular cleavage type, benzoin derivatives, benzyl ketals, α-hydroxyacetophenones, α-aminoacetophenones, acylphosphine oxides, titanocenes, O-acyl oximes, etc., and as the hydrogen abstraction type, benzophenone, Michler's ketone, thioxanthone, etc.

[0046] The content of the polymerization initiator in the above resin composition may be appropriately changed according to the type of the polymerization initiator and the like. The content of the polymerization initiator in the above resin composition may be, for example, 0.1 part by mass or more, preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, based on 100 parts by mass of the acrylic monomer. Also, the content of the polymerization initiator in the above resin composition may be, for example, 10 parts by mass or less, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, based on 100 parts by mass of the acrylic monomer.

[0047] The above resin composition may further contain other components other than the acrylic monomer and the polymerization initiator. Examples of the other components include coupling agents, wetting agents, dyes, pigments, plasticizers, fillers, release agents, polishing aids, and other additives.

[0048] In the three-dimensional element 12, the ratio C2 / C1 (mass ratio) of the content C2 of the abrasive grains to the content C1 of the binder is 0.05 or more, preferably 0.1 or more. Also, the ratio C2 / C1 (mass ratio) is 1.5 or less, and from the viewpoint of more significantly obtaining the above effects, it is preferably 1.0 or less, more preferably 0.7 or less. Also, from the viewpoint of reducing the amount of diamond used and suppressing the cost, the ratio C2 / C1 (mass ratio) may be, for example, 1.5 or less, 1.0 or less, 0.7 or less, 0.5 or less, or 0.2 or less.

[0049] When the three-dimensional element 12 is divided into an apex 12a on the side opposite the substrate 11, which accounts for 20% by volume of the three-dimensional element 12, and a base 12b on the substrate 11 side, which accounts for 80% by volume of the three-dimensional element 12, it is preferable that more than 50% by mass of the abrasive grains in the three-dimensional element 12 are located at the apex 12a.

[0050] As described above, when the abrasive grain content in the top portion 12a is high, polishing performance can be efficiently achieved with a small amount of abrasive grains, and the above-mentioned effects are more pronounced. More specifically, because the top portion 12a is the portion that constitutes the polishing surface, the selective presence of abrasive grains in the top portion 12a can achieve high polishing performance even with a small amount of abrasive grains. Furthermore, because the base portion 12b is the portion that constitutes the groove for discharging polishing debris, a small amount of abrasive grains is thought to further improve the discharge of polishing debris, further suppress adhesion of polishing debris to the polishing surface, and make it easier to obtain a more uniformly smooth surface.

[0051] From the viewpoint of obtaining the above effect more significantly, the amount of abrasive grains contained in the top portion 12a is more preferably 55% by mass or more of the abrasive grains in the three-dimensional element 12, and further preferably 60% by mass or more.

[0052] 1, the three-dimensional elements 12 are shown as having a triangular cross section, but the shape of the three-dimensional elements 12 is not necessarily limited to this. The three-dimensional elements 12 may have, for example, a cone structure with a convex portion at the apex and a base that is joined to the intermediate layer 13. Alternatively, the three-dimensional elements 12 may have, for example, a triangular prism structure with a convex portion at one side and a side surface opposite the convex portion that is joined to the intermediate layer 13.

[0053] The three-dimensional elements 12 may also have a columnar structure, for example, with one bottom surface forming a convex portion and the other bottom surface joining to the intermediate layer 13. The three-dimensional elements 12 may also have a frustum structure, for example, with one bottom surface forming a convex portion and the other bottom surface joining to the intermediate layer 13.

[0054] The three-dimensional element 12 may have a multi-layer structure. For example, the three-dimensional element 12 may be composed of an abrasive layer made of abrasive grains and a binder, and a support layer made of a binder.

[0055] The height of the three-dimensional elements 12 (the height from the recesses to the protrusions on the polishing surface) may be, for example, 2 to 800 μm, or 4 to 400 μm.

[0056] The intermediate layer 13 is a layer disposed between the substrate 11 and the three-dimensional element 12 and bonds the substrate 11 and the three-dimensional element 12 together.

[0057] The Young's modulus of the intermediate layer 13 at 25°C is 1.0 × 10 7 It is preferable that the surface tension is equal to or higher than Pa. Such an intermediate layer 13 can sufficiently fix the three-dimensional elements 12 onto the substrate 11, and therefore can sufficiently prevent the three-dimensional elements 12 from falling off during polishing.

[0058] In order to achieve the above effect more significantly, the Young's modulus of the intermediate layer 13 at 25° C. is 3.0×10 7 Pa or more is preferable, 5.0 × 10 7 Pa or more is more preferable.

[0059] The Young's modulus of the intermediate layer 13 at 25°C is 5.0 × 10 8 It is preferable that the pressure is equal to or less than Pa. Such an intermediate layer 13 functions as a buffer layer during high-load polishing, allowing each of the multiple three-dimensional elements 12 to conform to the unevenness of the object to be polished. Therefore, such an intermediate layer 13 makes it easy to form a smooth surface with minimal unevenness.

[0060] In order to achieve the above effect more significantly, the Young's modulus of the intermediate layer 13 at 25° C. is 4.0×10 8 Pa or less is preferable, and 2.0×10 8 Pa or less is more preferable.

[0061] The Young's modulus of the intermediate layer is shown by the value of the complex elastic modulus calculated from the results of the dynamic viscoelasticity measurement by bending vibration at a frequency of 1 Hz in accordance with ISO 6721-5 under the following conditions. (Measurement Conditions) · Measuring device: Solids Analyzer RSA III manufactured by Rheometric Scientific · Measurement mode: Three Point Bending · Distance between support ends: 40 mm · Frequency: 1 Hz · Approximate dimensions of test piece: width 10 mm × length 50 mm × thickness 2 mm · Strain: 0.05%

[0062] The constituent material of the intermediate layer 13 is not particularly limited as long as it can bond the base material 11 and the three-dimensional element 12. The intermediate layer 13 may be composed of, for example, a cured product of a thermosetting resin composition or a cured product of a photocurable resin composition.

[0063] In a preferred embodiment, the intermediate layer 13 may be composed of a cured product of a resin composition containing urethane acrylate. Such an intermediate layer 13 tends to easily achieve both the above-described preferred Young's modulus and a strong adhesive force between the base material 11 and the three-dimensional element 12.

[0064] Urethane acrylate can be said to be a polymerizable compound having a urethane bond and at least one polymerizable group selected from the group consisting of an acryloyl group and a methacryloyl group. Specific examples of urethane acrylate include, for example, polyester skeleton-containing urethane acrylate, polyether skeleton-containing urethane acrylate, aliphatic urethane acrylate, aromatic urethane acrylate, and the like.

[0065] The above resin composition may further contain other polymerizable compounds other than urethane acrylate. The other polymerizable compounds may be appropriately selected from compounds copolymerizable with urethane acrylate. Examples of the other polymerizable compounds include tetrahydrofurfuryl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, cyclic trimethylolpropane formal acrylate, glycidyl methacrylate, (meth)acrylic acid, and the like. Further, the above resin composition may further contain a polymerizable compound that does not copolymerize with urethane acrylate, such as an epoxy resin.

[0066] The proportion of urethane acrylate in the polymerizable compounds in the above resin composition may be, for example, 40% by mass or more, preferably 50% by mass or more, and more preferably 70% by mass or more. Thereby, the above-described suitable Young's modulus can be more easily obtained.

[0067] The upper limit of the proportion of urethane acrylate in the polymerizable compounds in the above resin composition is not particularly limited, and may be, for example, 99.9% by mass or less, or may be 99% by mass or less.

[0068] The above resin composition may further contain a polymerization initiator for initiating the polymerization of urethane acrylate. Examples of the polymerization initiator include thermal polymerization initiators and photopolymerization initiators, and among these, photopolymerization initiators for initiating free radical polymerization are preferred. Examples of the photopolymerization initiator include benzoin derivatives, benzyl ketals, α-hydroxyacetophenone, α-aminoacetophenone, acylphosphine oxides, titanocenes, O-acyl oximes, etc. as the intramolecular cleavage type, and benzophenone, Michler's ketone, thioxanthone, etc. as the hydrogen abstraction type.

[0069] The content of the polymerization initiator in the above resin composition may be appropriately changed according to the type of the polymerization initiator and the like. The content of the polymerization initiator in the above resin composition may be, for example, 0.1 part by mass or more, preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, based on 100 parts by mass of the polymerizable compound. Further, the content of the polymerization initiator in the above resin composition may be, for example, 50 parts by mass or less, preferably 20 parts by mass or less, more preferably 10 parts by mass or less, based on 100 parts by mass of the polymerizable compound.

[0070] The above resin composition may further contain other components other than the polymerizable compound and the curing agent. Examples of the other components include coupling agents, wetting agents, dyes, pigments, plasticizers, fillers, and other additives.

[0071] In the polishing sheet 10, the intermediate layer 13 is three-dimensionally formed together with the three-dimensional element 12 and constitutes the concave portion of the polishing surface. Further, the polishing sheet 10 has a plurality of intermediate layers 13, and the plurality of intermediate layers 13 each join one three-dimensional element 12 and the base material 11. That is, in the polishing sheet 10, one three-dimensional element 12 is provided on one intermediate layer 13.

[0072] In the present embodiment, the shape of the intermediate layer is not limited to the above shape. For example, in the polishing sheet, a plurality of three-dimensional elements may be joined to the three-dimensional element by one intermediate layer. In other words, a plurality of three-dimensional elements may be provided on one intermediate layer.

[0073] In the present embodiment, the total volume of the three-dimensional elements with respect to the total of the three-dimensional elements and the intermediate layer is, for example, 55% by volume or more, preferably 60% by volume or more, more preferably 70% by volume or more. Thereby, the polishing sheet tends to have a longer service life. Further, the total volume of the three-dimensional elements with respect to the total of the three-dimensional elements and the intermediate layer is, for example, 95% by volume or less, preferably 90% by volume or less, more preferably 85% by volume or less. Thereby, the adhesion between the base material and the intermediate layer and the adhesion between the intermediate layer and the three-dimensional element are further improved, and a smoother surface with more stable polishing force of the polishing sheet is more easily obtained.

[0074] FIG. 2 is a cross-sectional view showing another aspect of the polishing sheet. The polishing sheet 20 shown in FIG. 2 includes a base material 21, a plurality of three-dimensional elements 22, and an intermediate layer 23 disposed between the base material 11 and the plurality of three-dimensional elements 22 and joining the base material 11 and the plurality of three-dimensional elements. The intermediate layer 23 is joined to the base material 11 on one surface side and to the plurality of three-dimensional elements 22 on the other surface side. The surface of the intermediate layer 23 that contacts the three-dimensional element 22 is three-dimensionally formed together with the three-dimensional element 22 and constitutes a concave portion of the polishing surface.

[0075] The base material 21 and the three-dimensional element 22 may be the same as the base material 11 and the three-dimensional element 12 in the polishing sheet 10, and the intermediate layer 23 may be the same as the intermediate layer 23 in the polishing sheet 10 except for its shape. When the three-dimensional element 22 is divided into a top portion 22a occupying 20% by volume of the three-dimensional element 22 and a base portion 22b occupying 80% by volume of the three-dimensional element 22, it is preferable that 50% by mass or more of the abrasive grains in the three-dimensional element 22 are located in the top portion 22a.

[0076] Note that although the intermediate layer 23 is three-dimensionally formed together with the three-dimensional element 22 and forms a three-dimensional shape on the polishing surface, the intermediate layer 23 does not necessarily have to be three-dimensionally formed, and the three-dimensional element 22 may be provided on the smooth surface of the intermediate layer 23.

[0077] In the present embodiment, a three-dimensional shape is formed on the polishing surface of the polishing sheet by three-dimensional elements (in some cases, three-dimensional elements and an intermediate layer). Hereinafter, with reference to the drawings, a preferred aspect of the three-dimensional shape will be exemplified.

[0078] FIG. 3(a) is a top view showing one aspect of the three-dimensional shape of the polishing sheet. The three-dimensional portion 121 has a pyramid structure (triangular pyramid structure) in which the apex forms a convex portion and is joined to the base material side at the bottom surface. In FIG. 3(a), although the plurality of three-dimensional portions 121 are in contact with each other at the bottom edges of the pyramid structures, the plurality of three-dimensional portions 121 may be spaced apart from each other.

[0079] In Fig. 3(a), reference sign o indicates the bottom side length of the three-dimensional part 121, and reference sign p indicates the distance between the vertices of adjacent three-dimensional parts 121. o may be, for example, 5 μm to 1000 μm, preferably 10 μm to 500 μm. p may be, for example, 5 μm to 1000 μm, and is 10 μm to 500 μm.

[0080] Fig. 3(b) is a top view showing another aspect of the three-dimensional shape of the polishing sheet. The three-dimensional part 122 has a frustum structure that forms a convex part on one bottom surface and is joined to the substrate side on the other bottom surface. In Fig. 3(b), the plurality of three-dimensional parts 122 are spaced apart from each other, but the plurality of three-dimensional parts 122 may be in contact with each other at the bottom sides on the substrate side.

[0081] In Fig. 3(b), reference sign o indicates the bottom side length of the three-dimensional part 122 on the substrate side, reference sign u indicates the distance between the bottom sides of adjacent three-dimensional parts 122, and reference sign y indicates the bottom side length of the side where the convex part of the three-dimensional part 122 is formed. o may be, for example, 5 μm to 2000 μm, preferably 10 μm to 1000 μm. u may be, for example, 0 to 1000 μm, preferably 2 μm to 500 μm. y may be, for example, 0.5 μm to 1800 μm, preferably 1 μm to 900 μm.

[0082] Fig. 4(a) is a perspective cross-sectional view showing another aspect of the three-dimensional shape of the polishing sheet. The three-dimensional part 123 has a triangular prism structure that forms a convex part on one side and is joined to the substrate side on the side surface opposite to the side. The three-dimensional part 123 has a multilayer structure including a three-dimensional element 132 and an intermediate layer 133. When the three-dimensional element 132 is divided into a top part 132a that occupies 20% by volume of the three-dimensional element 132 and a base part 132b that occupies 80% by volume of the three-dimensional element 132, it is preferable that 50% by mass or more of the abrasive grains in the three-dimensional element 132 are located in the top part 132a.

[0083] In addition, although Fig. 4(a) shows a three-dimensional element having a triangular prism structure and a multilayer structure, the three-dimensional part having a triangular prism structure may not have a multilayer structure and may be composed only of three-dimensional elements.

[0084] The apex angle α of the three-dimensional part 123 may be, for example, 30° to 150°, and may be 45° to 140°. In FIG. 4(a), the symbol h indicates the height of the three-dimensional part 123, and the symbol s indicates the height of the three-dimensional element 132. h may be, for example, 10 μm to 10000 μm, preferably 20 μm to 1000 μm. s may be, for example, 5% to 95% of the height h of the three-dimensional part, preferably 10% to 90%.

[0085] In FIG. 4(a), the symbol w indicates the length of the short base (width of the three-dimensional part 123), the symbol p indicates the distance between the tops of the three-dimensional part 123, and the symbol u indicates the distance between the long bases of adjacent three-dimensional parts 123. w may be, for example, 2 μm to 2000 μm, preferably 4 μm to 1000 μm. p may be, for example, 2 μm to 4000 μm, preferably 4 μm to 2000 μm. u may be, for example, 0 to 2000 μm, preferably 0 to 1000 μm.

[0086] The length (length of the long base) of the three-dimensional part 123 may extend across the entire area of the polishing sheet. In this case, both ends in the direction of the long base of the three-dimensional part 123 are near the ends of the polishing sheet, and a plurality of three-dimensional parts 123 are arranged in a stripe shape.

[0087] Also, the three-dimensional part 123 may have an appropriate length for the length of the long base, for example, 5 μm to 10000 μm. An example in this case is shown in FIG. 4(b). In FIG. 4(b), the end face of the three-dimensional part 124 is shaped such that it is cut off with an acute angle from below, but the end face of the three-dimensional part 124 is not limited to such a shape.

[0088] In FIG. 4(b), the symbol l indicates the length of the long base of the three-dimensional part 124, and the symbol x indicates the distance between the short bases of adjacent three-dimensional parts 124. l may be, for example, 5 μm to 10000 μm, preferably 10 μm to 5000 μm. x may be, for example, 0 to 2000 μm, preferably 0 to 1000 μm.

[0089] The polishing sheet according to this embodiment can sufficiently reduce the unevenness of the target surface during polishing under high load. Therefore, the polishing sheet can be suitably used for high-load polishing applications. That is, the polishing sheet may be a polishing sheet for high-load polishing.

[0090] The load in high-load polishing may be, for example, 1.0×10 6 Pa or more, preferably 1.2×10 6 Pa or more, and more preferably 1.5×10 6 Pa or more. Also, the load in high-load polishing may be, for example, 5.0×10 6 Pa or less, preferably 3.0×10 6 Pa or less.

[0091] Also, since the polishing sheet according to this embodiment is suitable for high-load polishing, it can be suitably used for polishing applications of hard materials such as metal products. That is, the polishing sheet may be a polishing sheet for polishing hard materials.

[0092] The hard material refers to, for example, a material having a Vickers hardness of HV150 or more as defined in ISO 8486-2:2007. Examples of hard materials include, for example, carbon steel, stainless steel, titanium, tungsten, and ceramic materials such as silicon carbide, aluminum nitride, zirconia, and alumina.

[0093] (Polishing method) The polishing method according to this embodiment is a polishing method for polishing a plurality of polishing objects using the above polishing sheet. The polishing method according to this embodiment includes a first polishing step of pressing the polishing surface of the polishing sheet against the polishing object and sliding the polishing sheet and the polishing object, and a reuse step of polishing another polishing object using at least a part of the polishing surface used in the first polishing step.

[0094] In the first polishing step, the load when pressing the polishing sheet against the polishing object may be a high load of, for example, 1.0×10 6 Pa or more. The load may be, for example, 1.2×10 6Preferably, it is above Pa, and more preferably above 1.5×10 6 Pa. The upper limit of the load may be, for example, 5.0×10 6 Pa or less, and preferably 3.0×10 6 Pa or less.

[0095] The sliding between the polishing sheet and the object to be polished may be carried out by fixing one and sliding the other, or by sliding both. In this embodiment, among these, the method of fixing the object to be polished and sliding the polishing sheet is particularly preferred.

[0096] The object to be polished is not particularly limited, but from the viewpoint of significantly obtaining the effect by using the above polishing sheet, it is preferably the above-mentioned hard material.

[0097] In this embodiment, when sliding the polishing sheet and the object to be polished, a lubricating fluid may be interposed. Lubricating fluids are roughly classified into water-soluble and water-insoluble. Water-soluble lubricating fluids include soluble type, solution type, and emulsion type, and any of these may be used. In addition, examples of water-insoluble lubricating fluids include lubricating fluids composed of mineral oil and / or fatty oil, and the lubricating fluid may or may not contain an extreme pressure additive.

[0098] In this embodiment, by performing the reuse process a plurality of times (for example, 10 times or more, preferably 15 times or more, more preferably 20 times or more), a plurality of (for example, 10, preferably 15 or more, more preferably 20 or more) objects to be polished may be polished on the same polishing surface. Note that the polishing method in the reuse process may be the same as that in the first polishing process.

[0099] As described above, the preferred embodiments of the present invention have been described, but the present invention is not limited to the above embodiments.

Examples

[0100] Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

[0101] (Example A-1) (Preparation of Composition for Forming Three-dimensional Element) 62.33 parts by mass of tris(2-hydroxyethyl)isocyanurate triacrylate (SR368, manufactured by Arkema), 0.06 parts by mass of a silane coupling agent (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.), 1.25 parts by mass of a photopolymerization initiator (Omunirad 819, manufactured by IGM Resins), 0.62 parts by mass of a photopolymerization initiator (Omunirad 369, manufactured by IGM Resins), 5.52 parts by mass of diamond abrasive grains (average particle diameter 15 μm), and 30.22 parts by mass of propylene glycol methyl ether were mixed to prepare a composition for forming a three-dimensional element. The ratio of the content of diamond abrasive grains to the content of the resin component in the composition was 0.09.

[0102] (Preparation of Composition for Forming Intermediate Layer) 78.43 parts by mass of urethane acrylate (CN991, manufactured by Arkema), 19.61 parts by mass of an acrylate monomer (Biscoat #150, manufactured by Osaka Organic Chemical Industry Co., Ltd.), and 1.96 parts by mass of a photopolymerization initiator (Omunirad 819, manufactured by IGM Resins) were mixed to prepare a composition for forming an intermediate layer.

[0103] (Preparation of Substrate) As a substrate, a PET film (thickness 125 μm, Young's modulus at 25°C is 5.0 MPa) was prepared.

[0104] (Production of Polishing Sheet) A shaped film made of polypropylene having recesses corresponding to the three-dimensional shape shown in Fig. 3(a) on the surface was prepared. The composition for forming a three-dimensional element was applied onto the shaped film with a bar coater to fill the recesses of the shaped film with the composition for forming a three-dimensional element. Thereafter, the composition filled in the recesses was dried at 75°C for 5 minutes. Next, the composition for forming an intermediate layer was applied onto the shaped film, the substrate was placed thereon, and pressure was applied with a roll. Thereafter, ultraviolet rays were irradiated from the substrate side to cure the composition for forming an intermediate layer. Next, the shaped film was peeled off and oven-heated at 70°C for 24 hours to obtain a polishing sheet. When analyzing the three-dimensional elements of the obtained polishing sheet, it was confirmed that many abrasive grains were present on the top side due to the sedimentation of the abrasive grains in the concave portions.

[0105] (Example A-2) 59.35 parts by mass of tris(2-hydroxyethyl)isocyanurate triacrylate (SR368, manufactured by Arkema), 0.09 parts by mass of a silane coupling agent (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.), 1.19 parts by mass of a photopolymerization initiator (Omunirad 819, manufactured by IGM Resins), 0.59 parts by mass of a photopolymerization initiator (Omunirad 369, manufactured by IGM Resins), 8.76 parts by mass of diamond abrasive grains (average particle diameter 15 μm), and 30.03 parts by mass of propylene glycol methyl ether were mixed to prepare a composition for forming three-dimensional elements. The ratio of the content of diamond abrasive grains to the content of the resin component in the composition was 0.14. A polishing sheet was produced in the same manner as in Example A-1 except that this composition for forming three-dimensional elements was used.

[0106] (Example A-3) 52.80 parts by mass of tris(2-hydroxyethyl)isocyanurate triacrylate (SR368, manufactured by Arkema), 0.16 parts by mass of a silane coupling agent (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.), 1.06 parts by mass of a photopolymerization initiator (Omunirad 819, manufactured by IGM Resins), 0.53 parts by mass of a photopolymerization initiator (Omunirad 369, manufactured by IGM Resins), 15.59 parts by mass of diamond abrasive grains (average particle diameter 15 μm), and 29.87 parts by mass of propylene glycol methyl ether were mixed to prepare a composition for forming three-dimensional elements. The ratio of the content of diamond abrasive grains to the content of the resin component in the composition was 0.3. A polishing sheet was produced in the same manner as in Example A-1 except that this composition for forming three-dimensional elements was used.

[0107] (Example A-4) 43.07 parts by mass of tris(2-hydroxyethyl)isocyanurate triacrylate (SR368, manufactured by Arkema), 0.25 parts by mass of a silane coupling agent (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.), 0.86 parts by mass of a photopolymerization initiator (Omunirad 819, manufactured by IGM Resins), 0.43 parts by mass of a photopolymerization initiator (Omunirad 369, manufactured by IGM Resins), 25.42 parts by mass of diamond abrasive grains (average particle diameter 15 μm), and 29.96 parts by mass of propylene glycol methyl ether were mixed to prepare a composition for forming a three-dimensional element. The ratio of the content of diamond abrasive grains to the content of the resin component in the composition was 0.6. A polishing sheet was produced in the same manner as in Example A-1 except that this composition for forming a three-dimensional element was used.

[0108] (Example A-5) 23.30 parts by mass of tris(2-hydroxyethyl)isocyanurate triacrylate (SR368, manufactured by Arkema), 0.34 parts by mass of a silane coupling agent (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.), 0.46 parts by mass of a photopolymerization initiator (Omunirad 819, manufactured by IGM Resins), 0.23 parts by mass of a photopolymerization initiator (Omunirad 369, manufactured by IGM Resins), 34.39 parts by mass of diamond abrasive grains (average particle diameter 15 μm), and 41.27 parts by mass of propylene glycol methyl ether were mixed to prepare a composition for forming a three-dimensional element. The ratio of the content of diamond abrasive grains to the content of the resin component in the composition was 1.4. A polishing sheet was produced in the same manner as in Example A-1 except that this composition for forming a three-dimensional element was used.

[0109] (Comparative Example X-1) 67.22 parts by mass of tris(2-hydroxyethyl)isocyanurate triacrylate (SR368, manufactured by Arkema), 0.01 part by mass of a silane coupling agent (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.), 1.34 parts by mass of a photopolymerization initiator (Omunirad 819, manufactured by IGM Resins), 0.67 part by mass of a photopolymerization initiator (Omunirad 369, manufactured by IGM Resins), 0.99 part by mass of diamond abrasive grains (average particle diameter 15 μm), and 29.76 parts by mass of propylene glycol methyl ether were mixed to prepare a composition for forming a three-dimensional element. The ratio of the content of diamond abrasive grains to the content of the resin component in the composition was 0.014. A polishing sheet was produced in the same manner as in Example A-1 except that this composition for forming a three-dimensional element was used.

[0110] (Comparative Example X-2) 65.63 parts by mass of tris(2-hydroxyethyl)isocyanurate triacrylate (SR368, manufactured by Arkema), 0.02 part by mass of a silane coupling agent (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.), 1.31 parts by mass of a photopolymerization initiator (Omunirad 819, manufactured by IGM Resins), 0.66 part by mass of a photopolymerization initiator (Omunirad 369, manufactured by IGM Resins), 1.94 parts by mass of diamond abrasive grains (average particle diameter 15 μm), and 30.44 parts by mass of propylene glycol methyl ether were mixed to prepare a composition for forming a three-dimensional element. The ratio of the content of diamond abrasive grains to the content of the resin component in the composition was 0.028. A polishing sheet was produced in the same manner as in Example A-1 except that this composition for forming a three-dimensional element was used.

[0111] (Comparative Example X-3) 17.29 parts by mass of tris(2-hydroxyethyl)isocyanurate triacrylate (SR368, manufactured by Arkema), 0.51 parts by mass of a silane coupling agent (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.), 0.31 parts by mass of a photopolymerization initiator (Omunirad 819, manufactured by IGM Resins), 0.17 parts by mass of a photopolymerization initiator (Omunirad 369, manufactured by IGM Resins), 51.06 parts by mass of diamond abrasive grains (average particle size 15 μm), and 30.64 parts by mass of propylene glycol methyl ether were mixed to prepare a composition for forming a three-dimensional element. The ratio of the content of diamond abrasive grains to the content of the resin component in the composition was 2.8. A polishing sheet was produced in the same manner as in Example A-1 except that the composition for forming a three-dimensional element was used.

[0112] (Evaluation of the polishing sheet) Regarding the polishing sheets produced in the examples and comparative examples, a polishing test was conducted under the following conditions, and the grinding amount (mg / 30 s) in 30 seconds and the surface roughness Ra (μm) of the obtained smooth surface were determined. Further, on the same polished surface, the polishing test was conducted 19 times under the same conditions, and the grinding amount in 30 seconds and the surface roughness Ra of the obtained smooth surface were determined for each time. The results of the grinding amount are shown in Table 1, and the results of the surface roughness Ra are shown in Table 2. · Workpiece to be polished: S45C (without heat treatment) · Workpiece size: 10 mm Φ × 200 mm in length · Polishing device: Superfinisher (manufactured by Matsuda Seiki Co., Ltd.) · Rotation speed: 829 rpm · Polishing sheet feed: None · Oscillation: None · Grinding fluid: Simtech 500 (manufactured by CIMCOOL FLUIDS TECHNOLOGY) 2% aqueous solution · Backup roll hardness: Shore A 30° · Depth of cut: 4.2 mm · Polishing time: 30 seconds · Cut amount: The weight loss of the workpiece after the polishing test was defined as the cut amount. · Surface average roughness Ra: Measured under the following device and conditions. Device: SURFTEST SV-3100H4 manufactured by Mitutoyo Corporation Measurement Conditions: Conforming to JIS B-0601:2001 (ISO 4287:1997) Cut-off: 0.8 mm Evaluation Length: 4 mm

[0113]

Table 1

[0114]

Table 2

[0115] As shown in Table 1 and Table 2, in Comparative Examples X-1 and X-2 where the ratio C2 / C1 is less than 0.05, the grinding amount significantly decreased with less than 10 grinding passes, making grinding difficult. Also, in Comparative Example X-3 where the ratio C2 / C1 exceeds 1.5, the surface roughness Ra gradually increased after more than 10 grinding passes, making it difficult to form a uniform smooth surface. In contrast, in Examples A-1 to A-5, even when the number of grinding passes exceeded 20, a grinding amount of 3.5 mg / 30 seconds or more and a surface roughness Ra of less than 0.06 μm were maintained, and it was confirmed that a uniform smooth surface could be formed even when repeated grinding was performed on the same grinding surface.

Explanation of Reference Signs

[0116] 10, 20... grinding sheets, 11, 21... base materials, 12, 22... three-dimensional elements, 13, 23... intermediate layers, 121, 122, 123, 123... three-dimensional parts.

Claims

1. A base material, a plurality of three-dimensional elements containing diamond abrasive grains and a binder and constituting a polishing surface, an intermediate layer provided between the base material and the three-dimensional elements and bonding the base material and the three-dimensional elements, comprising: the binder is a cured product of a resin composition containing an acrylic monomer, and 60% by mass or more of the acrylic monomer is a polyfunctional monomer selected from the group consisting of tris(2-hydroxyethyl)isocyanurate triacrylate and tris(2-hydroxyethyl)isocyanurate diacrylate, the intermediate layer is composed of a cured product of a resin composition containing urethane acrylate, the intermediate layer is three-dimensionally formed together with the three-dimensional elements, when the three-dimensional element is divided in the thickness direction into a base portion on the base material side occupying 80% by volume of the three-dimensional element and a top portion on the side opposite to the base material occupying 20% by volume of the three-dimensional element, 50% by mass or more of the diamond abrasive grains in the three-dimensional element are located at the top portion, The content C of the binder １ The content C of the diamond abrasive grains relative to ２ Ratio C ２ / C １ is 0.05 to 1.5 in terms of mass ratio, the polishing sheet.

2. The polishing sheet according to claim 1, wherein the average particle diameter of the diamond abrasive grains is 5 μm or more.

3. The ratio C ２ / C １ is 0.05 to 0.7 in terms of mass ratio, and the polishing sheet according to claim 1 or 2.

4. The polishing sheet according to any one of claims 1 to 3, wherein the total volume of the three-dimensional elements is 60 to 90% by volume with respect to the total of the three-dimensional elements and the intermediate layer.

5. A polishing method for polishing a plurality of polishing objects using the polishing sheet according to any one of claims 1 to 4, a first polishing step of pressing the polishing surface of the polishing sheet against a polishing object and sliding the polishing sheet and the polishing object, a reuse step of polishing another polishing object using at least a part of the polishing surface used in the first polishing step, comprising: a polishing method.

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