Polishing pad

Abstract

To provide a polishing pad which is improved in maintainability of a polishing rate with respect to polishing time.SOLUTION: A polishing pad comprises a sheet-like substrate, and an abrasive layer laminated on one surface side of the substrate. The abrasive layer contains abrasive grains, a filler and a binder. A ratio of an average particle diameter of the filler relative to an average grain diameter of the abrasive grain is 1.0 or more.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] In recent years, electronic devices such as hard disks have become increasingly sophisticated. Glass is often used as a substrate material for such electronic devices, considering its rigidity, impact resistance, and heat resistance, which allow for miniaturization and thinning. Glass substrates are brittle materials, and surface scratches significantly reduce their mechanical strength. Therefore, polishing such substrates requires not only a high polishing rate but also high flatness accuracy with minimal scratches, which determines the type and particle size of abrasive grains.

[0003] Furthermore, in order to improve productivity, reducing running costs is required for polishing industrial glass substrates. Examples of running costs include the cost of consumables such as abrasives and the cost required for dressing. Dressing refers to the process of scraping off the surface of the abrasive to expose new abrasive grains to the surface in order to restore the polishing rate that has decreased due to the wear of the abrasive grains. The abrasive is also cleaned before and after dressing. Furthermore, polishing of the glass substrate, which is the workpiece, is interrupted during dressing. Therefore, a polishing pad that is less likely to decrease in polishing rate over a relatively long period of time and has a long dressing interval is desired.

[0004] One such polishing pad known in the art is one in which the polishing layer has multiple types of abrasive grains, of which the abrasive grains with the largest average particle diameter are designated as first abrasive grains and the abrasive grains with the second largest average particle diameter are designated as second abrasive grains, and the ratio of the average particle diameter of the second abrasive grains to the average particle diameter of the first abrasive grains is 5% or more and 70% or less (see International Publication No. 2017 / 163565).

[0005] In this conventional polishing pad, the second abrasive grains, which have a smaller average particle size than the first abrasive grains, tend to fall off the polishing layer before the first abrasive grains. This falling off causes the polishing pad to become dull, causing the first abrasive grains, which have a relatively low grinding power, to fall off and expose new abrasive grains. As a result, the proportion of abrasive grains with high grinding power among the abrasive grains on the surface of the polishing layer increases, preventing a decrease in the polishing rate. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] See International Publication No. 2017 / 163565 Summary of the Invention [Problem to be solved by the invention]

[0007] The above-mentioned conventional polishing pads are less likely to decrease in polishing rate and can reduce the frequency of dressing, thereby reducing running costs due to dressing, but further cost improvements are desired.

[0008] The present invention has been made in view of the above circumstances, and has as its object to provide a polishing pad with improved maintenance of the polishing rate relative to the polishing time. [Means for solving the problem]

[0009] A polishing pad according to one embodiment of the present invention is a polishing pad comprising a sheet-like substrate and a polishing layer laminated on one side of the substrate, wherein the polishing layer contains abrasive grains, a filler, and a binder, and the ratio of the average particle size of the filler to the average particle size of the abrasive grains is 1.0 or more. [Effects of the Invention]

[0010] The polishing pad of the present invention has improved maintenance of the removal rate relative to the polishing time. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic plan view showing a polishing pad according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic partially enlarged plan view of the polishing pad of FIG. [Figure 3] FIG. 3 is a schematic partial cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a schematic partial cross-sectional view showing a polishing pad according to an embodiment different from the polishing pad of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Description of the embodiment of the present invention] First, embodiments of the present invention will be listed and described.

[0013] The present inventors have conducted extensive research into the maintenance of the polishing rate relative to the polishing time, and as a result, while it was previously believed that the largest average particle size of the abrasive grains was necessary to ensure the polishing rate, the present inventors have discovered that by using a filler having an average particle size larger than that of the abrasive grains, a high polishing rate and its maintenance can be achieved without worsening the surface roughness of a difficult-to-cut material such as a glass substrate, and have completed the present invention.

[0014] In other words, the polishing pad according to one embodiment of the present invention is a polishing pad comprising a sheet-like substrate and a polishing layer laminated on one side of the substrate, wherein the polishing layer contains abrasive grains, a filler and a binder, and the ratio of the average particle size of the filler to the average particle size of the abrasive grains is 1.0 or more.

[0015] In this polishing pad, the average particle size of the filler is larger than that of the abrasive grains. By making the average particle size of the filler larger than that of the abrasive grains, it is possible to achieve a high removal rate and maintain it, particularly for difficult-to-cut materials, without worsening the surface roughness.

[0016] The ratio of the average particle size of the filler to the average particle size of the abrasive grains is preferably 1.5 or less. By setting the ratio of the average particle size of the filler to the average particle size of the abrasive grains to the upper limit or less, the filler can be prevented from interfering with the grinding of the abrasive grains, making it easier to increase the polishing rate.

[0017] The Mohs hardness of the filler is preferably at least 4. By making the Mohs hardness of the filler at or above the lower limit, high polishing performance can be achieved even for hard-to-cut materials such as glass, ceramics, and semiconductors.

[0018] The filler is preferably aluminum oxide particles. By using aluminum oxide particles as the filler, the maintenance of the polishing rate can be improved.

[0019] The abrasive grains are preferably diamond abrasive grains. By using diamond abrasive grains as the abrasive grains in this way, the polishing rate can be easily increased.

[0020] Here, "abrasive grains" and "fillers" are both granular materials contained in the polishing layer. In other words, the polishing layer contains at least two types of granular materials, and the granular materials with the highest hardness among these granular materials are "abrasive grains," while the granular materials excluding abrasive grains that are contained in the polishing layer at the highest volume percent are "fillers." Note that granular materials contained in the polishing layer at less than 1 volume percent are not included. Furthermore, with regard to the types of granular materials, not only those with different compositions but also allotropes are treated as different types. On the other hand, crystallinity is not an issue. In other words, graphite and diamond are different types of granular materials, but single crystal diamond and polycrystalline diamond are the same type of granular material.

[0021] The term "average particle size" refers to the 50% value (50% particle size, D50) of the cumulative particle size distribution curve on a volume basis measured by laser diffraction or the like.

[0022] [Details of the embodiment of the present invention] A polishing pad according to one embodiment of the present invention will be described with reference to the drawings.

[0023] 1 to 3 includes a sheet-like substrate 10, a polishing layer 20 laminated on one side of the substrate 10, and an adhesive layer 30 laminated on the other side. Hereinafter, the surface of the substrate 10 on which the polishing layer 20 is laminated will also be referred to as the "front surface," and the surface on which the adhesive layer 30 is laminated will also be referred to as the "back surface."

[0024] <Base material> The substrate 10 is a member for supporting the polishing layer 20 .

[0025] The main component of the substrate 10 is not particularly limited, but examples include polycarbonate (PC), polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polyimide (PI), polyethylene naphthalate (PEN), aramid, aluminum, and copper. Among these, PC is preferred because it has an excellent balance between heat resistance and adhesiveness. The surface of the substrate 10 may also be subjected to treatments to enhance adhesiveness, such as chemical treatment, corona treatment, and primer treatment. The "main component" refers to the component with the highest content, for example, a component that is contained in an amount of 50% by mass or more.

[0026] Furthermore, the substrate 10 is preferably flexible or ductile. The flexibility or ductility of the substrate 10 allows the polishing pad 1 to conform to the surface shape of the workpiece, increasing the contact area between the polishing surface and the workpiece, thereby further increasing the polishing rate. Examples of materials for the substrate 10 that have such flexibility include PET and PI. Examples of materials for the substrate 10 that have ductility include aluminum and copper.

[0027] The lower limit of the average thickness of the substrate 10 is preferably 75 μm, more preferably 100 μm, and even more preferably 150 μm. On the other hand, the upper limit of the average thickness of the substrate 10 is preferably 3 mm, more preferably 1 mm, and even more preferably 500 μm. If the average thickness of the substrate 10 is less than the lower limit, the strength and flatness of the polishing pad 1 may be insufficient. Conversely, if the average thickness of the substrate 10 exceeds the upper limit, the polishing pad 1 may become unnecessarily thick and may be difficult to handle. Here, "average thickness" refers to the average value of thicknesses measured at any 10 points.

[0028] The shape and size of the substrate 10 are determined appropriately according to the shape and size of the platen of the polishing machine to be used. For example, the substrate 10 of the polishing pad 1 shown in FIG. 1 is annular. The annular substrate 10 may have an outer diameter of 200 mm to 2022 mm and an inner diameter of 100 mm to 658 mm. The shape of the substrate 10 is not limited to annular, and may be circular with a diameter of 200 mm to 2022 mm or a square with a side of 140 mm to 160 mm, for example.

[0029] Furthermore, from the viewpoint of ease of handling of the polishing pad 1, a configuration in which a plurality of substrates 10 are supported on the platen of a polishing machine may be adopted. In this case, the substrate 10 is divided into a plurality of pieces, which are transported and fixed to the platen of the polishing machine, thereby forming an annular polishing pad 1 as shown in FIG.

[0030] <Polishing layer> 2, the abrasive layer 20 has a plurality of abrasive portions 20a and grooves 20b formed between the abrasive portions 20a. The abrasive layer 20 contains abrasive grains 21, a filler 22, and a binder 23 in the abrasive portions 20a.

[0031] (polishing section) The polishing portion 20a of the polishing pad 1 has a quadrangular prism shape with a square top surface.

[0032] The lower limit of the average area of ​​the top surface of the polishing portion 20a is 6 mm 2 is preferable, and 8 mm 2On the other hand, the upper limit of the average area of ​​the top surface of the polishing portion 20a is 30 mm 2 is preferable, and 25 mm 2 is more preferable, and 20 mm 2 is more preferable. If the average area of ​​the top surface of the polishing portion 20a is less than the above lower limit, the bottom area of ​​the polishing portion 20a will also be small, and the polishing portion 20a may not be able to adhere sufficiently to the substrate 10, and may be prone to tipping over during polishing. Conversely, if the average area of ​​the top surface of the polishing portion 20a exceeds the above upper limit, the polishing pressure may be dispersed, which may result in a decrease in the polishing rate or may make the substrate 10 more prone to warping.

[0033] The lower limit of the minimum distance between the polishing portions 20a (D in FIG. 2) is preferably 0.5 mm, more preferably 1.0 mm. On the other hand, the upper limit of the minimum distance D is preferably 3 mm, more preferably 2.5 mm. If the minimum distance D is less than the lower limit, the average area of ​​the top surfaces of the polishing portions 20a cannot be sufficiently ensured, and the polishing portions 20a may be prone to tipping over during polishing. Conversely, if the minimum distance D exceeds the upper limit, the width of the grooves 20b between adjacent polishing portions 20a may increase, making the substrate 10 more prone to warping. By setting the minimum distance D between the polishing portions 20a within the above range, an appropriate contact area and polishing pressure with the workpiece can be ensured, thereby further increasing the polishing rate of the polishing pad 1.

[0034] The lower limit of the average thickness of the polishing portions 20a (the average height from the surface of the substrate 10 to the top surfaces of the polishing portions 20a) is preferably 0.5 mm, more preferably 0.8 mm, and even more preferably 1 mm. On the other hand, the upper limit of the average thickness of the polishing portions 20a is preferably 2 mm, more preferably 1.8 mm. If the average thickness of the polishing portions 20a is less than the lower limit, the durability of the polishing portions 20a may be insufficient, and the life of the polishing pad 1 may be shortened. Conversely, if the average thickness of the polishing portions 20a exceeds the upper limit, the aspect ratio of the polishing portions 20a may become large, and the polishing portions 20a may easily tip over due to the load applied to the interface between the polishing portions 20a and the substrate 10 by the moment generated during polishing, or the manufacturing cost of the polishing pad 1 may increase.

[0035] The lower limit of the area occupancy of the multiple abrasive portions 20a is preferably 20%, more preferably 30%, and even more preferably 35%. Meanwhile, the upper limit of the area occupancy is preferably 65%, more preferably 61%, and even more preferably 60%. If the area occupancy is below the lower limit, the pressure applied during polishing will be too concentrated on the narrow abrasive portions 20a, which may cause the abrasive portions 20a to peel off from the substrate 10. Conversely, if the area occupancy exceeds the upper limit, the contact area of ​​the abrasive portions 20a with the workpiece during polishing will be large, which may result in a decrease in the polishing rate due to frictional resistance. Note that the area occupancy refers to the ratio of the total area of ​​the multiple abrasive portions 20a to the surface area of ​​the substrate 10. However, if there is a region where no abrasive portions 20a are arranged, such as on the periphery of the substrate 10, the area of ​​this region will be excluded from the surface area of ​​the substrate 10.

[0036] The polishing units 20a may be arranged in a block pattern regularly in the orthogonal X and Y directions in a plan view, as shown in Figures 1 and 2. In this case, the polishing units 20a are arranged in a grid pattern with equal intervals, improving the in-plane uniformity of the polishing pressure and increasing the flattening accuracy.

[0037] The arrangement of the polishing units 20a is not limited to a block pattern, and may be, for example, a staggered arrangement. By arranging the polishing units 20a in this manner, warping of the substrate 10 can be suppressed, thereby improving the uniformity of the polishing pressure on the surface and further increasing the flattening accuracy. Here, "the polishing units are staggered" refers to an arrangement in which the polishing units are arranged at equal intervals in multiple parallel rows, and the centers of the polishing units in one row and adjacent rows are not located in a direction perpendicular to the row, passing through the center of the polishing unit in that row.

[0038] Alternatively, the polishing portions 20a may be arranged concentrically, with the centers of the polishing portions 20a arranged on the circumference of circles of different radii around one center point on the same plane. In the concentric arrangement, when a workpiece is placed at equal intervals in a surface polishing machine and polished, the polishing portions 20a are regularly arranged in the radial direction, making it possible to polish the workpiece with a constant polishing pressure at all times, thereby improving flattening accuracy.

[0039] (groove) The grooves 20b control the area occupancy of the polishing portion 20a depending on the size thereof in a plan view, and also play a role in discharging polishing powder generated during polishing to the outside of the polishing pad 1.

[0040] In the polishing pad 1 of this embodiment, the bottom surfaces of the grooves 20b are formed on the surface of the substrate 10, as shown in Fig. 3. By forming the bottom surfaces of the grooves 20b on the surface of the substrate 10 in this way, the ability to discharge polishing powder is improved. Furthermore, with use, the polishing portion 20a wears, and the polishing pad 1 reaches the end of its life when its top surface approaches the bottom surface of the grooves 20b. However, by forming the bottom surfaces of the grooves 20b on the surface of the substrate 10, the period until the end of its life can be extended.

[0041] On the other hand, the bottom surface of the grooves 20b may be formed by the surface of the polishing layer 20. In other words, the polishing layer 20 may be configured so that multiple polishing portions 20a protrude from a bottom polishing layer that is thinner than the average height of the polishing portions 20a. With this configuration, the multiple polishing portions 20a are connected by the bottom polishing layer, thereby improving adhesion to the substrate 10.

[0042] (abrasive grain) Examples of the abrasive grains 21 include diamond abrasive grains, alumina abrasive grains, silica abrasive grains, ceria abrasive grains, and silicon carbide abrasive grains. Among these, diamond abrasive grains are preferred because they are harder than other abrasive grains. By using diamond abrasive grains as the abrasive grains 21, the polishing power is improved, and the polishing rate can be further improved.

[0043] The diamond of the diamond abrasive grains may be single crystal or polycrystalline, or may be diamond treated with Ni coating or the like. Among them, single crystal diamond and polycrystalline diamond are preferred. Single crystal diamond is harder than other diamonds and has a high grinding power. Furthermore, polycrystalline diamond is easily cleaved at the microcrystalline unit that constitutes the polycrystal, and is less susceptible to dulling, so the reduction in polishing rate is small even when polishing for a long period of time.

[0044] The lower limit of the average particle size of the abrasive grains 21 is preferably 1 μm, more preferably 3 μm. On the other hand, the upper limit of the average particle size of the abrasive grains 21 is preferably 100 μm, more preferably 50 μm, and even more preferably 30 μm. If the average particle size of the abrasive grains 21 is less than the lower limit, the polishing rate may be insufficient. Conversely, if the average particle size of the abrasive grains 21 exceeds the upper limit, the planarization precision may be insufficient.

[0045] The lower limit of the content of abrasive grains 21 in polishing layer 20 is preferably 1 vol%, more preferably 2 vol%, and even more preferably 5 vol%. On the other hand, the upper limit of the content of abrasive grains 21 is preferably 55 vol%, more preferably 45 vol%, and even more preferably 35 vol%. If the content of abrasive grains 21 is below the lower limit, the polishing power of polishing layer 20 may be insufficient. Conversely, if the content of abrasive grains 21 exceeds the upper limit, the polishing layer 20 may not be able to retain the abrasive grains 21.

[0046] (filling material) Examples of the filler 22 include oxides such as aluminum oxide (alumina) particles, silicon oxide (silica) particles, cerium oxide particles, magnesium oxide particles, zirconia particles, and titanium oxide particles, as well as composite oxides such as silica-alumina particles, silica-zirconia particles, silica-magnesia particles, and wollastonite particles, and silicon carbide particles.

[0047] It is preferable that the filler 22 is aluminum oxide particles. By using aluminum oxide as the filler 22 in this way, it is possible to prevent a decrease in the polishing rate and to easily maintain the polishing rate.

[0048] The lower limit of the Mohs hardness of the filler 22 is preferably 4, and more preferably 7. By setting the Mohs hardness of the filler 22 to be equal to or greater than the lower limit, high polishing performance can be achieved even with hard-to-cut materials such as glass, ceramics, and semiconductors. On the other hand, the upper limit of the Mohs hardness of the filler 22 is 10 by definition, but in the polishing pad 1, the Mohs hardness of the filler 22 is lower than the Mohs hardness of the abrasive grains 21.

[0049] The lower limit of the average particle size of the filler 22 is preferably 2 μm, more preferably 5 μm. On the other hand, the upper limit of the average particle size of the filler 22 is preferably 200 μm, more preferably 100 μm, and even more preferably 50 μm. If the average particle size of the filler 22 is below the lower limit, abrasive grains 21 with an even smaller average particle size must be used to maintain the polishing rate using the filler 22, and the polishing rate itself may be insufficient. Conversely, if the average particle size of the filler 22 exceeds the upper limit, polishing of particularly difficult-to-cut materials may become difficult.

[0050] The ratio of the average particle size of the filler 22 to the average particle size of the abrasive grains 21 is 1.0 or more, more preferably greater than 1.0, and even more preferably 1.1 or more. On the other hand, the upper limit of this average particle size ratio is preferably 1.5, more preferably 1.4. If the average particle size ratio is below the lower limit, the effect of the filler 22 in maintaining the polishing rate may be insufficient, and the polishing rate may be easily reduced. Conversely, if the average particle size ratio exceeds the upper limit, the filler 22 may be more likely to hinder the grinding of the abrasive grains 21, and the polishing rate itself may be reduced.

[0051] The lower limit of the content of filler 22 in polishing layer 20 is preferably 35 vol%, more preferably 45 vol%. On the other hand, the upper limit of the content of filler 22 is preferably 75 vol%, more preferably 70 vol%. If the content of filler 22 is less than the above lower limit, the effect of filler 22 in maintaining the polishing rate may be insufficient, and the polishing rate may be easily reduced. Conversely, if the content of filler 22 exceeds the above upper limit, the abrasive grains 21 may become relatively small, and the polishing rate itself may be reduced.

[0052] (binder) The main component of the binder 23 of the abrasive layer 20 is not particularly limited, but may be a resin or an inorganic substance.

[0053] Examples of the resin include polyurethane, polyphenol, epoxy, polyester, cellulose, ethylene copolymer, polyvinyl acetal, polyacrylic, acrylic ester, polyvinyl alcohol, polyvinyl chloride, polyvinyl acetate, polyamide, etc. Among these, polyacrylic, epoxy, polyester, and polyurethane are preferred because they can easily ensure good adhesion to the substrate 10. The resin may be at least partially crosslinked.

[0054] Examples of the inorganic substance include silicates, phosphates, and polyvalent metal alkoxides. Among these, silicates, which have high abrasive grain retention, are preferred. Examples of such silicates include sodium silicate and potassium silicate.

[0055] The binder 23 may contain various auxiliary agents and additives such as a dispersant, a coupling agent, a surfactant, a lubricant, an antifoaming agent, and a colorant, depending on the purpose.

[0056] (Other granular materials) In addition to the abrasive grains 21 and the filler 22, the polishing layer 20 may contain other granular materials (hereinafter simply referred to as "granular materials"). The granular materials have a lower hardness than the abrasive grains 21 and a lower content than the filler 22. The granular materials can function as auxiliary abrasive grains or auxiliary fillers. The granular materials functioning as auxiliary abrasive grains preferably have properties similar to those of the abrasive grains 21 described above, and the granular materials functioning as auxiliary fillers preferably have properties similar to those of the filler 22 described above. More specifically, it is preferable that the ratio of the average particle size of the granular materials having a hardness of 9 or more to the average particle size of the filler 22 is less than 1.0, and that the ratio of the average particle size of the granular materials having a hardness less than 9 to the average particle size of the abrasive grains 21 is greater than 1.0. In this case, the granular materials having a hardness of 9 or more can function as auxiliary abrasive grains, and the granular materials having a hardness less than 9 can effectively function as auxiliary fillers.

[0057] <Adhesive layer> The adhesive layer 30 is a layer that fixes the polishing pad 1 to a support that supports the polishing pad 1 and is used to mount the polishing pad on a polishing apparatus.

[0058] The adhesive used for the adhesive layer 30 is not particularly limited, but examples thereof include reactive adhesives, instant adhesives, hot melt adhesives, and pressure sensitive adhesives that are repositionable adhesives.

[0059] A pressure-sensitive adhesive is preferably used as the adhesive for the adhesive layer 30. By using a pressure-sensitive adhesive for the adhesive layer 30, the polishing pad 1 can be peeled off from the support and replaced, making it easy to reuse the polishing pad 1 and the support. Such pressure-sensitive adhesives are not particularly limited, but examples include acrylic pressure-sensitive adhesives, acrylic-rubber pressure-sensitive adhesives, natural rubber pressure-sensitive adhesives, synthetic rubber pressure-sensitive adhesives such as butyl rubber, silicone pressure-sensitive adhesives, polyurethane pressure-sensitive adhesives, and the like.

[0060] The lower limit of the average thickness of the adhesive layer 30 is preferably 0.05 mm, more preferably 0.1 mm. On the other hand, the upper limit of the average thickness of the adhesive layer 30 is preferably 0.3 mm, more preferably 0.2 mm. If the average thickness of the adhesive layer 30 is less than the lower limit, the adhesive strength may be insufficient, and the polishing pad 1 may peel off from the support. Conversely, if the average thickness of the adhesive layer 30 exceeds the upper limit, the thickness of the adhesive layer 30 may cause problems when cutting the polishing pad 1 into a desired shape, and this may result in reduced workability.

[0061] <Polishing Pad Manufacturing Method> The polishing pad 1 can be manufactured by a manufacturing method including, for example, a preparation step, a polishing layer forming step, and an adhesive layer attaching step.

[0062] (Preparation process) In the preparation step, a composition for a polishing layer is prepared that contains abrasive grains 21, a filler 22, and a binder 23. In manufacturing the polishing pad 1, abrasive grains 21 and a filler 22 are used in which the ratio of the average particle size of the abrasive grains 21 to the average particle size of the filler 22 is 1.0 or more.

[0063] Specifically, a coating liquid is prepared as a composition for a polishing layer containing materials for forming abrasive grains 21, filler 22, and binder 23. The contents of abrasive grains 21 and filler 22 in the solid content will be the contents of abrasive grains 21 and filler 22 in polishing layer 20 after manufacture, respectively, and therefore the amounts of each solid content are appropriately determined so that the contents in polishing layer 20 are the desired values.

[0064] Furthermore, a diluent such as water or alcohol is added to control the viscosity and fluidity of the coating liquid. This dilution allows some of the abrasive grains 21 contained in the polishing layer 20 to protrude from the surface of the binder 23. In other words, by adding a diluent, the thickness of the binder 23 decreases when the polishing layer composition is dried in the polishing layer formation step, increasing the amount of protrusion of the abrasive grains 21. Therefore, this dilution allows a high polishing rate to be achieved from the early stages of polishing.

[0065] (Polishing layer formation process) In the abrasive layer forming step, the composition for abrasive layers prepared in the preparation step is coated to form a plurality of abrasive layers 20. The abrasive layer forming step includes a coating step and a drying step.

[0066] [Coating process] In the coating step, the surface of the substrate 10 is coated with the composition for a polishing layer.

[0067] Specifically, the coating liquid prepared in the preparation step is used to coat the surface of the substrate 10, thereby forming a plurality of polishing portions 20a and grooves 20b disposed between the polishing portions 20a. To form the grooves 20b, a mask having a shape corresponding to the shape of the grooves 20b is prepared, and the coating liquid is applied through this mask.

[0068] The mask for the coating is preferably made of SUS or fluororesin, which allows the mask to be thick, making it easy to produce a polishing layer 20 with a large average thickness.

[0069] The height of the polishing layer 20 can be adjusted mainly by the thickness of the mask and the amount of coating. Therefore, in this coating step, it is preferable to adjust the amount of coating of the polishing layer composition so that the average height of the polishing layer 20 becomes a desired value.

[0070] [Drying process] In the drying step, the coating liquid (polishing layer composition) after the coating step is heated and dried. This heating and drying hardens the coating liquid, forming a plurality of polishing layers 20. This drying step is performed after removing the mask.

[0071] The lower limit of the heating temperature in the drying step is preferably 80°C, more preferably 100°C. On the other hand, the upper limit of the heating temperature is preferably 300°C, more preferably 200°C. If the heating temperature is below the lower limit, the composition for the polishing layer may not be sufficiently cured, resulting in increased wear and shortening the life of the polishing pad 1. Conversely, if the heating temperature exceeds the upper limit, the polishing layer 20 may be altered by heat.

[0072] The heating time in the drying step depends on the heating temperature, but the lower limit of the heating time is preferably 2 hours, more preferably 2.5 hours. If the heating time is less than the lower limit, the polishing composition may not be sufficiently cured, resulting in increased wear and shortening the life of the polishing pad 1. On the other hand, the upper limit of the heating time is not particularly limited, but can be, for example, 20 hours from the viewpoint of production efficiency.

[0073] (Adhesive layer attachment process) In the adhesive layer attaching step, the adhesive layer 30 is laminated on the back surface side of the base material 10. Specifically, for example, a pre-formed tape-like adhesive layer 30 is attached to the back surface of the base material 10.

[0074] Through the above steps, the polishing pad 1 can be manufactured.

[0075] <Advantages> In the polishing pad 1, the average particle size of the filler 22 is larger than the average particle size of the abrasive grains 21. By making the average particle size of the filler 22 larger than the average particle size of the abrasive grains 21 in this way, it is possible to achieve a high polishing rate and maintain the high polishing rate, particularly for difficult-to-cut materials, without worsening the surface roughness.

[0076] [Other embodiments] The present invention is not limited to the above-described embodiment, and can be implemented in various other forms, including those described above, with various modifications and improvements.

[0077] In the above embodiment, the polishing part has a square top surface, but the polishing part may have a rectangular top surface. However, a square top surface is preferable from the viewpoint of isotropy. Furthermore, the shape of the polishing part is not limited to a rectangular prism, and may be a hexagonal prism or other prism, or may be a cylindrical prism, a truncated cone, a truncated pyramid, or the like.

[0078] In the above embodiment, the polishing pad has been described as having multiple polishing portions, but it may have only one polishing portion. In this case, for example, one polishing portion may be laminated over the entire surface of the substrate. No grooves are formed.

[0079] In the above embodiment, the polishing pad has an adhesive layer, but the adhesive layer is not an essential component and can be omitted. If the polishing pad does not have an adhesive layer, the adhesive layer attachment step in the polishing pad manufacturing method can be omitted.

[0080] Alternatively, as shown in Fig. 4, the polishing pad 2 may include a support 40 that is further laminated on the other surface of the substrate 10 via an adhesive layer 30, and a second adhesive layer 31 that is further laminated on the support 40. Providing the support 40 in the polishing pad 2 makes it easier to handle the polishing pad 2. Note that, since the components of the polishing pad 2 other than the support 40 and the second adhesive layer 31 are the same as those of the polishing pad 1 shown in Fig. 3, the same reference numerals are used and their description will be omitted.

[0081] (Support) Examples of the main component of the support 40 include thermoplastic resins such as polypropylene, polyethylene, polytetrafluoroethylene, and polyvinyl chloride, and engineering plastics such as polycarbonate, polyamide, and polyethylene terephthalate. By using such a material as the main component of the support 40, the support 40 becomes flexible, the polishing pad 2 conforms to the surface shape of the workpiece, and the polishing surface and the workpiece come into easy contact with each other, thereby further improving the polishing rate. Among these, polyvinyl chloride is preferred as the main component of the support 40 from the viewpoint of adhesion to the adhesive layer 30 and the second adhesive layer 31.

[0082] The shape and size of the support 40 are determined appropriately according to the shape and size of the platen of the polishing machine to be used. A configuration in which a plurality of supports 40 arranged side by side on a plane like the substrate 10 described above are supported on the platen of the polishing machine may also be used.

[0083] The lower limit of the average thickness of the support 40 is preferably 0.5 mm, more preferably 0.8 mm. On the other hand, the upper limit of the average thickness of the support 40 is preferably 3 mm, more preferably 2 mm. If the average thickness of the support 40 is less than the lower limit, the strength of the polishing pad 2 may be insufficient. Conversely, if the average thickness of the support 40 exceeds the upper limit, it may be difficult to attach the support 40 to the platen of the polishing machine, or the flexibility of the support 40 may be insufficient.

[0084] (Second adhesive layer) The second adhesive layer 31 can use the same adhesive as the adhesive layer 30. The second adhesive layer 31 can have the same average thickness as the adhesive layer 30. [Example]

[0085] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0086] [No.1] A substrate having an average thickness of 0.5 mm and mainly composed of polycarbonate was prepared.

[0087] Diamond abrasive grains (average particle size 9.685 μm, Mohs hardness 10) were prepared as abrasive grains. Aluminum oxide grains (average particle size 9.983 μm; average particle size ratio to abrasive grains 1.03, Mohs hardness 9) were prepared as filler. Epoxy resin was prepared as binder. Silica grains (average particle size 30 nm, Mohs hardness 7) were also prepared as other granular materials.

[0088] The above materials were mixed to prepare a polishing composition, the solid content of which was 2.5% by volume of abrasive grains, 58.5% by volume of filler, 4% by volume of other granular materials, and 35% by volume of binder.

[0089] The abrasive layer having a plurality of abrasive portions was formed by coating the abrasive portion composition (coating liquid) onto the substrate.

[0090] The polishing portion was a square with sides of 3 mm in plan view, with an area ratio of 36% and an average thickness of 500 μm. The pattern of the polishing portions was a grid arrangement as shown in Figure 1.

[0091] In this way, polishing pad No. 1 was obtained.

[0092] [No.2] Polishing pad No. 2 was obtained in the same manner as No. 1, except that the filler content was 63.5% by volume, the binder content was 30% by volume, and the average thickness of the polishing portion was 1000 μm.

[0093] [No.3] Aluminum oxide particles (average particle size 12.41 μm; average particle size ratio to the abrasive particles 1.28) were prepared as a filler. Polishing pad No. 3 was obtained in the same manner as No. 2, except that this filler was used.

[0094] [No.4] Aluminum oxide particles (average particle size 3.291 μm; average particle size ratio to the abrasive particles 0.34) were prepared as a filler. Polishing pad No. 4 was obtained in the same manner as No. 1, except that this filler was used.

[0095] [No.5] Polishing pad No. 5 was obtained in the same manner as No. 4, except that the average thickness of the polishing portion was set to 1000 μm.

[0096] [Polishing conditions] A quartz glass polishing test was carried out for 50 minutes using polishing pads No. 1 to No. 5. A known double-sided polisher was used for the polishing. Note that the polisher used for No. 1 and No. 4 (Polisher A) was different from the polisher used for No. 2, No. 3, and No. 5 (Polisher B). The polishing pressure was 111 gf / cm for all the samples. 2 It was decided.

[0097] In the above polishing, the average polishing rate was calculated for five intervals at 10-minute intervals, and the average polishing rate for the last interval (the fifth interval, from more than 40 minutes to less than 50 minutes) was divided by the average polishing rate for the interval in which the maximum value was recorded among the five intervals to calculate the "polishing rate maintenance rate." The results are shown in Table 1. Note that the interval in which the maximum value was recorded was either the first interval, from more than 10 minutes to less than 20 minutes, or the second interval, from more than 20 minutes to less than 30 minutes, so Table 1 only shows the average polishing rates for the first, second, and fifth intervals.

[0098] Furthermore, the surface roughness Ra defined in JIS-B-0601:2013 was measured for the quartz glass after 50 minutes of polishing using a contact surface roughness meter (Mitutoyo Corporation's "S-3000U"). The results are shown in Table 1.

[0099] [Table 1]

[0100] In the results shown in Table 1, a comparison of No. 1 and No. 4, which were polished using the same polishing machine, and a comparison of No. 2, No. 3 and No. 5, shows that by using a filler with an average particle size larger than that of the abrasive grains, it is possible to improve the polishing rate and its maintenance without worsening the surface roughness, even for difficult-to-cut materials such as quartz glass. [Industrial Applicability]

[0101] The polishing pad of the present invention has improved retention of the polishing rate over the polishing time, and is therefore suitable for use in polishing the surface of difficult-to-cut materials such as glass, ceramics, and semiconductors. [Explanation of symbols]

[0102] 1, 2 Polishing pads 10 Base material 20 Polishing layer 20a Polishing section 20b groove 21 Abrasive grain 22 Filling material 23 Binder 30 Adhesive layer 31 Second adhesive layer 40 Support

Claims

1. A polishing pad comprising a sheet-like substrate and a polishing layer laminated on one surface of the substrate, the abrasive layer comprises abrasive grains, a filler, and a binder; The abrasive grains are diamond abrasive grains, The filler is aluminum oxide particles, A polishing pad in which the ratio of the average particle size of the filler to the average particle size of the abrasive grains is 1.0 or more.

2. 2. The polishing pad according to claim 1, wherein the ratio of the average particle size of said filler to the average particle size of said abrasive grains is 1.5 or less.

3. 3. The polishing pad according to claim 1, wherein the filler has a Mohs hardness of 4 or more.

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