Structured abrasive particles, articles and methods of using the same

Abstract

An abrasive rotary tool is presented that includes a cylindrical tool body having a curved lateral surface and a circular face. The abrasive rotary tool also includes a conformable abrasive film wrapped around an edge joining the curved lateral surface to the circular face. The conformable abrasive film includes a base portion coupled to the curved lateral surface and a plurality of protrusions extending from the base portion, each protrusion having a first width at the base portion and a second width at an opposing end. The second width is less than the first width. The rotary abrasive tool also includes a structured abrasive layer disposed on the conformable abrasive film. The structured abrasive layer has a plurality of precisely-shaped abrasive composites arranged in a repeating pattern. Each precisely-shaped abrasive composite includes a first substantially triangular-shaped face opposite a second substantially triangular- shaped face, a quadrilateral-shaped surface coupled to both the first and second substantially triangular-shaped faces, a cutting edge formed along one side of the quadrilateral-shaped surface, and a contacting edge formed along an opposite side, the contacting edge being longer than the cutting edge. The precisely-shaped abrasive composites comprise ceramic abrasive particles in a binder material.

Description

PA103275W005STRUCTURED ABRASIVE PARTICEES, ARTICLES AND METHODS OF USING THE SAMEBACKGROUND

[0001] When abrading wire-reinforced glass, heat-resistant glass, or another glass substrate for industrial use, or when abrading a large substrate containing a ceramic or metal material, extending the useful life and maintaining a high cut rate of an abrasive article of an abrasive pad is important. Structured abrasive articles, that is, those abrasive articles that have a plurality of shaped abrasive composites bonded to a backing, are widely used in the abrading steps. During abrading processes using structured abrasive articles, a liquid such as water or a cutting fluid is often added to the abrading interface to extend the useful life of the structured abrasive article. In the case of water, a surfactant is often used in addition.SUMMARY

[0002] An abrasive rotary tool is presented that includes a cylindrical tool body having a curved lateral surface and a circular face. The abrasive rotary tool also includes a conformable abrasive fdm wrapped around an edge joining the curved lateral surface to the circular face. The conformable abrasive fdm includes a base portion coupled to the curved lateral surface and a plurality of protrusions extending from the base portion, each protrusion having a first width at the base portion and a second width at an opposing end. The second width is less than the first width. The rotary abrasive tool also includes a structured abrasive layer disposed on the conformable abrasive film. The structured abrasive layer has a plurality of precisely-shaped abrasive composites arranged in a repeating pattern. Each precisely-shaped abrasive composite includes a first substantially triangular-shaped face opposite a second substantially triangularshaped face, a quadrilateral-shaped surface coupled to both the first and second substantially triangular-shaped faces, a cutting edge formed along one side of the quadrilateral-shaped surface, and a contacting edge formed along an opposite side, the contacting edge being longer than the cutting edge. The precisely-shaped abrasive composites comprise ceramic abrasive particles in a binder material.

[0003] The details of one or more examples of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims.BRIEF DESCRIPTION OF THE DRAWING

[0004] FIG. 1 illustrates a perspective sectional view of an abrasive material product having an abrasive part with triangular pyramid shaped structures.

[0005] FIG. 2 illustrates a plan view of an abrasive material product having an abrasive part with triangular pyramid shaped structures.

[0006] FIGS. 3A-3H illustrate perspective views of some precisely-shaped structured abrasive composites in accordance with embodiments herein.

[0007] FIGS. 4A-4E illustrate abrasive layers formed from a number of precisely-shaped abrasive composites arranged in repeating patterns in accordance with embodiments herein.

[0008] FIGS. 5A-5H illustrate a rotary abrasive system and tool in which embodiments herein may be particularly useful.

[0009] FIGS. 6A-6D illustrate a rotary tool in accordance with embodiments herein.

[0010] FIGS. 7A-7D illustrate shapes of composite abrasive structures described in greater detail in the Examples.

[0011] FIGS. 8A-8F illustrate different conformable abrasive fdm patterns which may be used with rotary tools in accordance with embodiments herein.

[0012] FIG. 9 illustrates a method of forming a rotary abrasive tool for a 3D abrasive operation in accordance with embodiments herein.

[0013] FIG. 10 illustrates a method of abrading a worksurface using a 3D rotary abrasive tool in accordance with embodiments herein.

[0014] FIGS. 11A-11C illustrate results of testing described in greater detail in the Examples.DETAILED DESCRIPTION

[0015] When shaped structures projecting from a substrate are formed in an abrasive part of an abrasive material product, the microstructures of the abrasive face become regular, and loading is reduced in the abrasive part. In this manner, both excellent finishing property and loading resistance for a long duration can be satisfied simultaneously. However, in the case of abrasive material products used for abrasive work with applying high load, improved durability of the abrasive part is still an objective.

[0016] Therefore, the present disclosure provides an abrasive material product comprising an abrasive part having excellent durability for even severe abrasive work with applying high load and long duration abrading work.

[0017] Different shapes of abrasive composite structures have been found to be useful for material removal from different substrates.

[0018] The present disclosure provides a new precisely-shaped abrasive composite for an abrasive article. The abrasive article, in some embodiments here, is a rotary abrasive tool with a compliant layer. The abrasive article may include a substrate and an abrasive part having a plurality of shaped structures projecting from the substrate, in which the abrasive part comprises (1) an upper layer composed of a cured material of a mixture containing abrasive particles dispersed in a resin and (2) a lower layer composed of a cured material of a binder agent containing a radiation-curable monomer and / or oligomer and a thermosetting resin.

[0019] As used herein, the term "shaped abrasive composite" refers to a body that comprises abrasive particles and a binder that is intentionally formed in a non-random shape (for example, a pyramid, ridge, etc.), and typically characterized by regular boundaries. Exemplary forming methods include cast and cure methods, embossing, and molding. The shaped abrasive composites may be disposed on the backing according to a predetermined pattern (for example, as an array). In some embodiments, shaped abrasive composites are "precisely-shaped". This term means that the shape of the abrasive composites is defined by relatively smooth surfaced sides that are bounded and joined by well-defined edges having distinct edge lengths with distinct endpoints defined by the intersections of the various sides. The terms "bounded" and "boundary" refer to the exposed surfaces and edges of each composite that delimit and define the actual three-dimensional shape of each abrasive composite. These boundaries are readily visible and discernible when a cross-section of an abrasive article is viewed under a scanning electron microscope. These boundaries separate and distinguish one precisely-shaped abrasive composite from another even if the composites abut each other along a common border at their bases. By comparison, in an abrasive composite that does not have a precise shape, the boundaries and edges are not well defined (for example, where the abrasive composite sags before completion of its curing).

[0020] As described herein, the term “length” refers to the longest edge dimension of a precisely-shaped abrasive composite. The term “width” refers to the next longest dimension that is perpendicular to the length. The term “thickness” refers to the shortest dimension perpendicular to both the length and width.

[0021] Precisely-shaped abrasive composites may be of any three-dimensional shape that results in at least one of a raised feature or recess on the exposed surface of the abrasive layer. Useful shapes include, for example, cubic, prismatic, pyramidal (for example, square pyramidal or hexagonal pyramidal), truncated pyramidal, conical, frustoconical. Combinations ofdifferently shaped and / or sized abrasive composites may also be used. The abrasive layer of the structured abrasive may be continuous or discontinuous.

[0022] Further details concerning structured abrasive articles having precisely-shaped abrasive composites, and methods for their manufacture may be found, for example, in U.S. Pat. Nos. 5,152,917 (Pieper et al.); 5,435,816 (Spurgeon et al.); 5,672,097 (Hoopman); 5,681,217 (Hoopman et al.); 5,454,844 (Hibbard et al.); 5,851,247 (Stoetzel et al.); and 6,139,594 (Kincaid et al.).

[0023] Typically, the shaped abrasive composites are arranged on the backing according to a predetermined pattern or array, although this is not a requirement. The shaped abrasive composites may be arranged such that some of their work surfaces are recessed from the polishing surface of the abrasive layer.

[0024] For fine finishing applications, the density of shaped abrasive composites in the abrasive layer is typically in a range of from at least 1,000, 10,000, or even at least 20,000 abrasive composites per square inch (for example, at least 150, 1,500, or even 7,800 abrasive composites per square centimeter) up to and including 50,000, 70,000, or even as many as 100,000 abrasive composites per square inch (up to and including 7,800, 11,000, or even as many as 15,000 abrasive composites per square centimeter), although greater or lesser densities of abrasive composites may also be used.

[0025] In some embodiments, the abrasive article includes a thermosetting resin between the abrasive layer and the substrate, which provides an adhesive force that maintains a coupling between the abrasive layer and the substrate even if it is used for a severe abrasive work with applying high load.

[0026] The present disclosure provides an abrasive article comprising a substrate and an abrasive part having a plurality of precisely-shaped abrasive composites projecting from the substrate.

[0027] FIG. 1 is a cross-sectional view of an exemplary abrasive article. The abrasive article includes, as illustrated in FIG. 1, a substrate 1 and an abrasive layer 2. The abrasive layer 2 is separated into an upper layer 4 for contact with the substance to be abraded and a lower layer 3 adjacent the substrate side. The upper layer 4 contains a resin 5 and abrasive particles 6 dispersed therein. In some embodiments, the lower layer 3 contains a resin, with no or substantially no abrasive particles. However, the lower layer 3, in some embodiments, may contain any of abrasive particles, a coloring agent, and a coupling agent to an extent that no adverse effect on the adhesion strength between the substrate and the upper layer is caused.

[0028] Structured abrasive articles are a specific type of coated abrasive article that typically has a plurality of shaped abrasive composites secured to a backing. Each shaped abrasive composite has a base in contact with the backing and a distal end that extends outwardly from the backing. The shaped abrasive composites comprise abrasive particles dispersed in a binder, typically a polymeric binder. The shaped abrasive composites are usually arranged in a close packed array. In one common configuration of a structured abrasive article, the shaped abrasive composites are pyramidal (e.g., tetrahedral or square pyramidal).

[0029] Traditionally, structured abrasive products such as, for example, those available as TRIZACT from 3M Company of St. Paul, Minn., have utilized pyramidal abrasive composites.

[0030] Substrate 1 may be formed from any suitable material including, but not limited to: polymer films, paper, cloths, metal films, fibers, nonwoven substrates, their combinations, and their processed products. The substrate may be a flexible material. The substrate may be transparent to ultraviolet ray radiation for convenience in curing the resin in a production process.

[0031] In some embodiments, substrate 1 is a polymer film such as a polyester film. It is because a polymer film has good smoothness and even thickness and accordingly high finishing precision can be obtained. The polymer film may be subjected to easy adhesion treatment for promoting adhesiveness to the substrate of the abrasive part. However, it is expressly contemplated that any suitable polymer film may be used. For example, a polyurethane film may be used, in some embodiments.

[0032] In some embodiments, a primer is used as an easy-adhesion treatment of polymer film is excellent in heat resistance. Other suitable treatments are possible.

[0033] An example substrate material is a polyester film. Polyester is excellent in mechanical strength, heat resistance, water resistance and oil resistance. When a polyester film is employed, thickness thereof is 10 to 500 pm, preferably 30 to 200 pm, more preferably 50 to 150 pm. The polyester film thickness within the range provides the flexibility which achieves good contact to an object to be abraded, and the strength which withstand the abrasive work with applying high load.

[0034] In a preferred embodiment of the present invention where abrasive material products are industrially mass-produced, it is necessary the process in which the steps of shaping an abrasive part, adhering it to a sheet-form substrate, and winding up the resulting abrasive material product are continuously conducted, so the shaped structures have to be adhered to the substrate in a short period of time. In order to adhere the shaped structures to the substrate in a short period time, it is preferred that the binder which forms the lower layer 3 is at least partiallycured through the radiation curing mechanism to adhere onto a surface of the substrate. Because the application of radiation energy is able to be conducted in a short period of time, and because curing rate of the radiation-curable resins is high.

[0035] In a preferred embodiment, a polymer fdm is employed as the substrate, the binder which forms the lower layer 3 is brought into contact with one surface thereof, light is irradiated from the opposite side of the transparent polymer fdm to cure the binder, and the shaped structures are adhered to the substrate at the same time. The resulted sheet form abrasive material product is then wound up and stored.

[0036] However, it is expressly contemplated that other polymeric fdms may be used in embodiments herein.

[0037] In some embodiments, an optional pressure-sensitive adhesive layer is present.

[0038] In some embodiments, lower layer 3 is substantially formed from a radiation-curable liquid binder. The radiation-curable means the property that it at least partially cures by absorbing radiation energy, and it adheres to a surface of the substrate.

[0039] In some embodiments, the lower layer 3 is composed of a cured material of a binder agent containing a radiation-curable liquid-state monomer and / or oligomer and a thermosetting resin. It is because adhesiveness to the substrate of the binder is sufficiently improved, the abrasive part becomes resistant to separation, and durability of the abrasive material product is improved, by comparison with the case where a radiation-curable liquid state monomer and / or oligomer is solely employed.

[0040] The radiation-curable liquid-state monomer and / or oligomer may include, for example, those known as a photocurable acrylic compound to a person skilled in the art. In one embodiment, they may be selected from a group consisting of acrylated urethane, acrylated epoxy, aminoplast derivatives having an a,[3-unsaturated carbonyl group, ethylenic unsaturated compounds, isocyanurate derivatives having at least one acrylate group, isocyanates having at least one acrylate group, and their mixtures.

[0041] Representative examples of ethylenically-unsaturated monomers include methyl (meth)acrylate, ethyl (meth)acrylate, styrene, divinylbenzene, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, vinyl toluene, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, glycerol tri(meth)acrylate, pentaerthyitol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate. Other ethylenically- unsaturated monomers or oligomers include monoallyl, polyallyl, and polymethallyl esters and amides of carboxylic acids, such as diallyl phthalate, diallyl adipate, and N,N-diallyladipamide.Still other nitrogen containing compounds include tris(2-acryloxyethyl)isocyanurate, l,3,5-tri(2- methacryloxyethyl)-s-triazine, acrylamide, methylacrylamide, N-methylacrylamide, N,N- dimethylacrylamide, N-vinylpyrrolidone, and N-vinylpiperidone.

[0042] Examples of commercially available acrylated urethanes include those known by the trade designations: PHOTOMER (for example, PHOTOMER 6010 from Henkel Corp, of Hoboken, NJ; EBECRYL (for example, EBECRYL 220 (a hexafunctional aromatic urethane acrylate of molecular weight 1000), EBECRYL 284 (aliphatic urethane diacrylate of 1200 grams / mole molecular weight diluted with 1,6-hexanediol diacrylate), EBECRYL 4827 (aromatic urethane diacrylate of 1600 grams / mole molecular weight), EBECRYL 4830 (aliphatic urethane diacrylate of 1200 grams / mole molecular weight diluted with tetraethylene glycol diacrylate), EBECRYL 6602 (trifunctional aromatic urethane acrylate of 1300 grams / mole molecular weight diluted with trimethylolpropane ethoxy triacrylate), and EBECRYL 840 (aliphatic urethane diacrylate of 1000 grams / mole molecular weight)) from UCB Radcure of Smyrna, GA; SARTOMER (for example, SARTOMER 9635, 9645, 9655, 963-B80, and 966-A80) from Sartomer Co., West Chester, PA; and UVITHANE (for example, UVITHANE 782) from Morton International, Chicago, IL.

[0043] Acrylated epoxies are acrylate esters of epoxy resins such as, for example, diacrylate esters of bisphenol A epoxy resin. Examples of commercially available acrylated epoxies include those available as CMD 3500, CMD 3600, and CMD 3700 from UCB Radcure, and as CN103, CN104, CN111, CN112, and CN114 from Sartomer Co.

[0044] Examples of polyester acrylates include those available as PHOTOMER 5007 and PHOTOMER 5018 from Henkel Corp.

[0045] A photocurable acrylic compound generally has (meth)acryloyl group in a molecule and has a molecular weight of 70 to 700 and 80 to 600 in one embodiment. Generally, acrylic acid esters and methacrylic acid esters may be used. Specific examples of the photocurable acrylic compound are as follows.

[0046] Examples of a monofunctional acrylic monomer comprise isobomyl acrylate, 2- hydroxyethyl (meth)acrylate, hydroxypropyl acrylate, 4-hydroxybutyl acrylate, ethylene oxide modified phenol acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, N,N- dimethylacrylamide, N,N-diethylacrylamide, acryloylmorpholine, N,N- dimethylaminopropylacrylamide, isopropylacrylamide, dimethylaminoethyl acrylate, 2-hydroxy- 3 -phenoxypropyl acrylate, dicyclopentanyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl tribromo(meth)acrylate, phenoxyethyl tribromo(meth)acrylate,biphenylethoxy (meth)acrylate, biphenylepoxy (meth)acrylate, naphthylethoxy (meth)acrylate, fluoreneepoxy (meth)acrylate, and the like.

[0047] Examples of a polyfunctional acrylic monomer include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethylene oxide modified trimethylolpropane tri(meth)acrylate, propylene oxide modified trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate, neopentyl di(meth)acrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, ditrimethylolpropane tetra(meth)acrylate, 2-methacryloyloxyethyl-2-hydroxypropyl acrylate, bisphenol A di(meth)acrylate, bisphenol A tetrabromodi(meth)acrylate, bisphenol A ethoxy-modified di(meth)acrylate, bisphenol A tetrabromoethoxy-modified di(meth)acrylate, bisphenol A-epoxy di(meth)acrylate, bisphenol A- epoxy ethoxy-modified di(meth)acrylate, bisphenol A-epoxy tetrabromodi(meth)acrylate, bisphenol A-epoxy tetrabromoethoxy-modified di(meth)acrylate, and the like. Further, acrylic monomer mixtures thereof may also be used.

[0048] The photocurable acrylic compound used for lower layer 3 may be a mixture of a monofunctional acrylic monomer and polyfunctional acrylic monomer. In order to quickly cure a liquid-state binder, a polyfunctional acrylic monomer may be used. The polyfunctional acrylic monomer is, however, high in viscosity and poor in compatibility with the thermosetting resins. If the polyfunctional acrylic monomer is solely employed as the photocurable acrylic compound, preparing a homogeneous binder mixture of sufficient amounts of the thermosetting resins may become difficult, and strength of the cured product tends to decrease.

[0049] On the other hand, a monofunctional acrylic monomer is low in viscosity, and superior in compatibility with the thermosetting resins. So, it becomes possible that viscosity of the binder decreases, compatibility with the thermosetting resin is improved to provide homogeneous binder, and that strength of the cured product improves when the monofunctional acrylic monomer is employed in combination with the polyfunctional acrylic monomer as the photocurable acrylic compound.

[0050] Particularly preferred examples of the monofunctional acrylic monomer include isobomyl acrylate, benzyl acrylate and the like. Particularly preferred examples of the polyfunctional acrylate include trifunctional acrylates such as trimethylol propane triacrylate, ethylene oxide modified trimethylol propane tri (meth)acrylate, propylene oxide modified trimethylol propane tri(meth)acrylate, and tetrafiinctional acrylate such as pentaerythritol tetraacrylate.

[0051] Mixing ratio of the monofiinctional acrylic monomer and the polyfiinctional acrylic monomer is 5 to 500 parts by weight, preferably 10 to 200 parts by weight, more preferably 20to 100 parts by weight of the polyfunctional acrylate based on 100 parts by weight of the monofunctional acrylate. The weight ratio within the range makes it possible to adjust viscosity of a mixture solution with the thermosetting resin or hardness of a cured product within the desirable range.

[0052] In some embodiments, each precisely-shaped abrasive composite contains from 2.5 to 3.5 percent by weight of a nonionic polyether surfactant based on a total weight of the shaped abrasive composite.

[0053] The binder agent of the lower layer 3 may contain a photo polymerization initiator to efficiently carry out polymerization of the photocurable acrylic compound by light radiation. The type and the use amount of the photo polymerization initiator are changed in accordance with the type and the amount of the acrylic monomer, and their determination methods are known well to a person skilled in the art.

[0054] Specific examples of the photo polymerization initiator may include, as a radical polymerization initiator, benzophenone, 2-methyl-l-[4-(methylthio)phenyl]-2- morpholinopropan-l-one, camphor quinone, benzoin, benzoin methyl ether, benzoin n-propyl ether, benzoin n-butyl ether, benzil, p-methylbenzophenone, diacetyl, eosin, thionine, Michler's ketone, acetophenone, 2-chlorothioxanethone, anthraquinone, chloroanthraquinone, 2- methylanthraquinone, a-hydroxyisobutylphenone, p-isopropyl-a-hydoxyisobutylphenone, a,a'- dichloro-4-phenoxyacetophenone, 1 -hydroxy- 1 -cyclohexylacetophenone, 2,2-dimethoxy-2- phenylacetophenone, methylbenzoin formate, dichlorothioxanthone, diisopropyl thioxanthone, phenyldisulfide-2-nitrosofluorene, butyroin, anisoin ethyl ether, tetramethylthiuram disulfide, 2,2-dimethoxy-l,2-diphenyl ethan-l-one, 1-hydroxy-cyclohexyl-phenyl -ketone, 2 -hydroxy-2 - methyl- 1 -phenyl-propan- 1 -one, 1 - [4-(2-hydroxyethoxy)-phenyl] -2-hydroxy-2 -methyl- 1 -propan- 1-one, 2-hydroxy-l-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-l- one, 2-methyl- 1 -(4-methylthiophenyl)-2 -morpholinopropan- 1 -one, 2-benzyl-2-dimethylamino- 1 - (4-morpholinophenyl)-butanone- 1, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-l-[4-(4- morpholinyl)phenyl]-l-butanone, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6- trmicthylbcnzoylj-phcnyl phosphine oxide and the like.

[0055] The photo polymerization initiator is contained in an amount of 0.1 to 20 parts by weight and in one embodiment, 0.5 to 10 parts by weight based on 100 parts by weight of a radiation-curable liquid-state monomer and / or oligomer and a thermosetting resin. If the amount of the photo polymerization initiator is less than 0.1 part by weight, the acrylic monomer polymerization becomes difficult even if light is radiated, and if it exceeds 20 parts by weight,polymerization occurs even by weak light and the storage stability of the binder agent is deteriorated.

[0056] As described above, as a component of lower layer 3, a thermosetting resin may be employed with the radiation-curable liquid-state monomer and / or oligomer. The thermosetting resin may have functional groups which are of different type from those of the radiation-curable liquid-state monomer and / or oligomer. The thermosetting resin does not have to be radiation- curable. The thermosetting resin comprises those which are known as a thermosetting epoxy resin to a person skilled in the art. The thermosetting epoxy resin has two or more epoxy groups per one molecule, a molecular weight of 100 to 2,000, or 200 to 1,500, and epoxy equivalent weight of 50 to 1,000 or 100 to 750. Specific examples of the thermosetting epoxy resin are as follows.

[0057] Examples thereof include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, tetrabromobisphenol A diglycidyl ether, resorcinol diglycidyl ether, phthalic acid diglycidyl ester, cresol novolac polyglycidyl ether, phenol novolac polyglycidyl ether, fluorene glycidyl ether, butanediol diglycidyl ether, hexanediol diglycidyl ether, cyclohexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, glycerin polyglycidyl ether, ethylene -polyethylene glycol diglycidyl ether, sorbitol polyglycidyl ether, and the like. Mixtures thereof can be also used.

[0058] Thermosetting epoxy resins as a component of lower layer 3 may include a cresol- novolac epoxy resin, a bisphenol A epoxy resin, or a mixture thereof. The cresol-novolac epoxy resin is particularly hard, and preferred when heat resistance is necessary. The bisphenol A epoxy resin is liquid, is easily miscible with the acrylic monomer and / or oligomer, and is preferred when flexibility is relatively necessary. By mixing both in an appropriate ratio, hardness can be adjusted in between. Both are excellent in adhesiveness to the substrate and strength, and also good in compatibility with the acrylic monomer and / or oligomer.

[0059] In one embodiment of abrasive material product of the present disclosure, the epoxy resin comprises a cresol-novolac epoxy resin, a bisphenol A epoxy resin, or a mixture thereof, and the acrylic compound comprises a polyfunctional acrylate.

[0060] The binder agent of the lower layer 3 may contain a curing agent for curing the thermosetting epoxy resin. The type and the use amount of the curing agent are changed in accordance with a type and an amount of the thermosetting epoxy resin and their determination methods are known well to a person skilled in the art.

[0061] In one embodiment, the curing agent contain two or more functional groups thermally reactive on epoxy groups per one molecule and has a molecular weight of 100 to2,000, in another embodiment, 200 to 1,500. Examples of the functional groups thermally reactive on epoxy groups may comprise amino groups, amido groups, mercapto groups, and the like. As the curing agent, generally, amines, amides, acid anhydrides, phenols, mercaptan compounds, tertiary amines, Lewis acid complexes, and the like are employed.

[0062] Specific examples of the curing agent include aliphatic amines having 4 to 20 carbon atoms such as hexamethylene diamine and diethylenetriamine; aromatic amines having 6 to 20 carbon atoms such as methaphenylenediamine, diaminophenylmethane, and diaminodiphenylsulfone; dicyandiamide and its derivatives having 2 to 20 carbon atoms; organic acid hydrazides having 3 to 30 carbon atoms such as phenylbiguanide and phenylbiguanide oxalate; BF3 complexes having 2 to 10 carbon atoms such as a BF3 -monoethylamine complex and a BF3 -diethylamine complex; imidazole derivatives having 4 to 30 carbon atoms such as 2- methylimidazole, 2-ethyl-4-methylimidazole and 2-phenylimidazole; diaminomaleonitrile and its derivatives having 4 to 20 carbon atoms; melamine resin and its derivatives; acid anhydrides having 8 to 40 carbon atoms such as phthalic anhydride and pyromellitic anhydride; bismaleimide; and the like.

[0063] The curing agent can be an amine derivative having a molecular weight of 80 to 200, dicyandiamide, and its derivatives.

[0064] The curing agent is used, for example, in the case of an imidazole derivative, in an amount of 0.5 to 20 parts by weight, in one embodiment, 1 to 10 parts by weight based on 100 parts by weight of a radiation-curable liquid-state monomer and / or oligomer and a thermosetting resin. If the amount of the curing agent is less than 0.5 part by weight, the thermosetting epoxy resin becomes difficult to be cured and the strength of the abrasive part is decreased, and if it exceeds 20 parts by weight, the hardness of the cured epoxy resin is decreased.

[0065] As the binder agent of the lower layer 3, a photocurable acrylic compound is preferably contained in an amount of 30 to 1,000 parts by weight, in one embodiment, 50 to 500 parts by weight based on 100 parts by weight of a thermosetting resin. If the amount of the photocurable acrylic compound is less than 30 parts by weight, it becomes difficult to nonfluidize the lower layer 3 in the production process and if it exceeds 1,000 parts by weight, strength of the lower layer 3 may decrease.

[0066] In one embodiment of abrasive material product of the present disclosure, the radiation-curable monomer and / or oligomer in the lower layer is an acrylic compound, the thermosetting resin is an epoxy resin, and 50 to 500 parts by weight of the acrylic compound is contained based on 100 parts by weight of the epoxy resin.

[0067] Particularly, when a mixture of the monofunctional acrylic monomer and the trifunctional acrylic monomer is employed as the photocurable acrylic compound for lower layer 3, and the bisphenol A diglycidyl ether and / or the cresol-novolac polyglycidyl ether are employed as the thermosetting acrylic compound, it is preferred that amount of the photocurable acrylic compound is adjusted to 100 to 200 parts by weight, particularly 120 to 180 parts by weight based on 100 parts by weight of the thermosetting resin to improve adhesiveness to a surface of the substrate.

[0068] In one embodiment of abrasive material product of the present disclosure, the acrylic compound is a mixture of a monofunctional acrylate and a polyfunctional acrylate.

[0069] Further, in one embodiment of abrasive material product of the present disclosure, the mixture comprises 20 to 100 parts by weight of the polyfunctional acrylate based on 100 parts by weight of the monofunctional acrylate.

[0070] The upper layer 4 is composed of a cured material of a mixture containing abrasive particles 6 dispersed in a resin 5. That is, the upper layer 4 is formed by solidifying a slurry containing a plurality of abrasive particles dispersed in the resin in uncured or ungelled state.

[0071] The size of the abrasive particles is, for final finishing abrading, 0.01 to 1 pm, in one embodiment 0.01 to 0.5 pm, and in another embodiment 0.01 to 0.1 pm; for rough abrading, 0.5 to 20 pm and in one embodiment 0.5 to 10 pm. The size of the abrasive particles may be 0.5 to 100 pm when lapping of brittle materials is conducted.

[0072] Examples of suitable abrasive particles for the fixed abrasive pad include cubic boron nitride, fused aluminum oxide, ceramic aluminum oxide, heat treated aluminum oxide, white fused aluminum oxide, black silicon carbide, green silicon carbide, titanium diboride, boron carbide, silicon nitride, tungsten carbide, titanium carbide, diamond, cubic boron nitride, cerium oxide, chromium oxide, hexagonal boron nitride, alumina zirconia, iron oxide, ceria, garnet, alumina zirconia, alumina-based sol gel derived abrasive particles and the like, as well as mixtures thereof. The alumina abrasive particle may contain a metal oxide modifier. Examples of alumina-based sol gel derived abrasive particles can be found in U.S. Pat. Nos. 4,314,827;4,623,364; 4,744,802; 4,770,671; and 4,881,951, all incorporated by reference herein. The diamond and cubic boron nitride abrasive particles may be mono crystalline or polycrystalline. Particularly preferable examples are, for rough abrading, diamond, cubic boron nitride, aluminum oxide, and silicon carbide; for finishing abrading, silica and aluminum oxide.Additionally, in some embodiments, agglomerates of any of the above abrasive particles may be used, such as the agglomerates described in U.S. Pat. 5,039,311, issued August 13, 1991. Otherexamples of suitable inorganic abrasive particles include silica, iron oxide, chromia, ceria, zirconia, titania, tin oxide, gamma alumina, and the like.

[0073] When the abrasive material product is employed for abrasive work with applying high load, high toughness is required for abrasive particles. So preferred abrasive particles are the particles of fused aluminum oxide or diamond, particularly diamond particles.

[0074] The resin is cured or gelled to form the abrasive part. In one embodiment, examples of the resin may comprise phenol resins, aminoplast resins, urethane resins, epoxy resins, acrylic resins, polyester resins, vinyl resins, melamine resins, acrylated isocyanurate resins, ureaformaldehyde resins, isocyanurate resins, acrylated urethane resins, acrylated epoxy resins and their mixtures. Particularly preferable one is resol-phenol resins.

[0075] Aminoplast monomers have at least one pendant alpha, beta-unsaturated carbonyl group. These unsaturated carbonyl groups may be acrylate, methacrylate or acrylamide type groups. Examples of such materials include N-(hydroxymethyl)-acrylamide, N,N'- oxydimethylenebisacrylamide, ortho- and para-acrylamidomethylated phenol, acrylamidomethylated phenolic novolac and combinations thereof.

[0076] In one embodiment of abrasive material product of the present disclosure, the resin of the upper layer comprises a phenol resin.

[0077] The resin in the upper layer may be radiation-curable. The resin may be resins which are at least partially cured by radiation or at least partially polymerizable. In one embodiment, the radiation-curable liquid-state monomer and / or oligomer of the lower layer 3 is used. Based on the type of the resin to be used, energy sources such as infrared ray, electron beam, ultraviolet radiation, and visible light radiation may be used.

[0078] The weight ratio of the abrasive particles to the resin is generally in the range of about 150 to 1000 parts of the abrasive particles based on 100 parts of the resin and in one embodiment in the range of about 200 to 700 parts of the abrasive particles based on 100 parts of the resin. The ratio is changed depending on the size of the abrasive particles and the type of the resin and use of the abrasive material product.

[0079] The mixture composing the upper layer may contain materials other than the abrasive particles and the resin. For example, conventional additives such as a coupling agent, a moistening agent, a dye, a pigment, a plasticizer, a filler, a release agent, an abrasion assisting agent, and mixtures of them.

[0080] The above-mentioned mixtures may contain a coupling agent. Addition of the coupling agent can remarkably decrease the coating viscosity of the slurry to be used for forming the abrasive part. Examples of the coupling agent preferable for the present disclosure compriseorganic silanes, zirconia aluminate and titanate. An amount of the coupling agent is generally less than 5% by weight to the total weight of the abrasive part and in one embodiment, less than 1% by weight.

[0081] Hereinafter, the morphology of the precisely-shaped abrasive composite structures projecting from the substrate will be described. The term “precisely-shaped” refers to abrasive composite structures that are formed in a predetermined shape. The shape of the projections is not needed to be specified if it is a shape artificially formed and has reproducibility. However, the shape is not a random shape formed by natural action. In one embodiment, a plurality of the shaped structures have substantially the same shape and their arrangement in a plane is regular. In embodiments herein, the precisely-shaped abrasive composites are formed using a mold, such that the precisely-shaped abrasive composites have a structure similar to the interior of a corresponding cavity or recess of the mold.

[0082] In some embodiments, a plurality of the precisely-shaped abrasive composites formed to have the same height from the surface of the substrate. However, it is expressly contemplated that, in some embodiments, adjacent precisely-shaped abrasive composites differ in height or shaped. Abrasive layer 2, in embodiments herein, comprises a repeating pattern of precisely-shaped abrasive composites 7. The pattern may include the same precisely-shaped abrasive composite repeated across a length and width of substrate 1, e.g. as illustrated in FIG. 2. However, it is expressly contemplated that, in some embodiments, a first precisely-shaped abrasive composite, having a first shape, may alternate with a second precisely-shaped abrasive composite, having a second shape. Other patterns, for example including three or more shapes, are also expressly contemplated.

[0083] In some embodiments herein, the precisely shaped abrasive composites 7 have a shape such that cross-sections taken parallel to the substrate have a narrower surface area as the cross section is taken at a greater distance from the substrate, e.g. the area of cross-sections increases as the precisely shaped abrasive composite 7 is worn down. The cross-section, in some embodiments, is a quadrilateral cross-section. In some embodiments, the cross-section is a rectangular, or substantially rectangular cross-section. In some embodiments, the cross-section is a trapezoidal cross-section.

[0084] FIG. 1 illustrates a plurality of precisely shaped abrasive composites 7 having substantially the same triangular pyramid shape, and their arrangement in a plane is regular as shown in FIG. 2.

[0085] In FIG. 1, the symbol s denotes height of the upper layer of the shaped structures. The symbol s is in the range of 5 to 95% of height, h, of the shaped structures and in oneembodiment, in the range of 10 to 90%. However, while FIG. 1 illustrates an embodiment where only a portion of a precisely shaped abrasive composite contains abrasive particles, it is expressly contemplated that, in other embodiments, the entire volume of the precisely shaped abrasive composite contains abrasive particles.

[0086] FIG. 2 illustrates a plan view of the abrasive material product having the abrasive part with a triangular pyramid shape of the shaped structures. In FIG. 2, the symbol ‘o’ shows bottom line length of the shaped structures. The symbol ‘p’ shows distance between apexes of the shaped structures. The symbol ‘o’ is, for example, in the range of 5 to 1000 pm and in one embodiment in the range of 10 to 500 pm. ‘p’ is, for example, in the range of 5 to 1,000 pm and in one embodiment in the range of 10 to 500 pm.

[0087] While FIGS. 1-2 illustrate one example known shape for precisely-shaped abrasive composites, it is noted that FIGS. 11 and 12a-12g of U.S. Pat. 9,919,406 issued on Mar. 20, 2018, illustrate a number of other shapes.

[0088] A number of precisely-shaped abrasive composite structures have been previously used. FIGS. 1-2 illustrate a tetrahedral-shaped abrasive composite. U.S. Pat. 9,919,406 issued on Mar. 20, 2018, for example, illustrates a number of shape options for precisely-shaped abrasive composites - a triangular prism in FIGS. 3-4, and a number of shorter, flat-topped structures in FIGS. 11-12. U.S. Pat. 8,425,278, issued April 23, 2013, illustrates a crown-shaped abrasive composite.

[0089] U.S. Pat. 9,415,480, issued August 16, 2016, illustrates another precisely-shaped abrasive composite structure that has historically shown good performance when abrading glass substrates.

[0090] However, a new shape, illustrated in FIGS. 3-4, has been surprisingly found to provide a significantly increased cut rate when compared to, for example, the trapezoidal design of FIGS. 1-2, the crown-shaped design of U.S. Pat. 8,425,278, or a flat triangular shape, such as that discussed in U.S. Pat. 9,919,406.

[0091] FIGS. 3-4 illustrate perspective views of a precisely-shaped structured abrasive composite in accordance with embodiments herein. Among other applications, embodiments herein include precisely-shaped abrasive composites that are particularly useful for grinding glass substrates. Historically, flat precisely-shaped abrasive composites have been used to grind glass substrates. Past attempts to increase cut rate has included changing abrasive particle concentration, abrasive particle size, and abrasive composite construction. Uarger sized abrasive particle can achieve higher cut, but with a rougher finish. However, it was surprisingly found that, controlling for formulation, force, speed and time, that the structure of FIGS. 3-4 resulted ina significantly higher cut rate. The improved cut rate was seen in all three directions of use - forward, backward and across the pattern (e.g. at an angle to the channels between rows of abrasive composite structures).

[0092] FIGS. 3A-3H illustrate some embodiments of precisely-shaped abrasive composites in accordance with embodiments herein. FIG. 3A illustrates a precisely-shaped abrasive composite 200, in accordance with embodiments herein. Composite 200 may have a base surface (not visible in FIG. 3A) that couples to a substrate. The base surface may be defined by a base length 202 and a base width 208. A rake face (not visible in FIG. 3 A) is defined by a rake face length 214. Abrasive composite 200 may also be defined by a relief face 204. Each of the three faces are coupled to both of the other faces such that two substantially triangular-shaped surfaces are formed, opposing each other. E.g., the base is coupled, on a first base edge (represented by base width 208), to relief surface 204. The base is coupled, on a second base edge (not visible in FIG. 3 A), opposite the first base edge, to the rake surface. Similarly, the relief face is coupled to the base along a first relief face edge. Along a second relief face edge, which is opposite the first relief edge, the relief face couples to the rake face. The rake face couples, along a first rake face edge, to the base, and to the relief face along a second rake face edge.

[0093] Base width 208 may be the same as a width of a rake face, e.g. such that the base face is rectangular in shape. In some embodiments, the rake face has a different width than a base width 208, e.g. such that the base is trapezoidal in shape. The rake face may have a longer width, such that precisely shaped abrasive composite 200 is wider on the rake surface end, or may have a shorter width, such that the precisely shaped abrasive composite is wider on a relief surface end.

[0094] The rake surface and relief surface 204 meet along a surface 206. Surface 206 is configured to contact a worksurface during an abrasive operation. Surface 206 may, in some embodiments, be an edge 206 as illustrated in FIG. 3A. However, it is expressly contemplated that surface 206 may have a width as well. For example, as abrasive composite 200 is used and worn down, edge 206 will wear into a contact surface 206, having a rectangular profile.

[0095] Abrasive composite 200 is shown in FIG. 3A in an orientation where a base surface is coupled to a worksurface. In operation, abrasive composite 200 contacts a surface along contact surface 206, and is moved along a machine direction 240. A rake angle 210 is formed between the rake face and the surface, and a relief angle 212 is formed between the relief face 204 and the surface.

[0096] Abrasive composite 200 has a height 220 measured between the contacting surface 206 and the base surface.

[0097] FIGS. 3B-3H illustrate several additional embodiments of an abrasive composite 200 in which one or more shape parameters are modified from the embodiment illustrated in FIG. 3A. It is expressly contemplated that the different shape options illustrated herein may also be combined. For example, a rake angle can be increased or decreased and texture can be added to a contact surface, in accordance with embodiments herein. The embodiments of FIGS. 3B-3H are provided for illustrative purposes only, and are not intended to represent the complete range of abrasive composite shapes that are contemplated herein.

[0098] FIG. 3B illustrates an example embodiment of a precisely-shaped abrasive composite 200 having a contacting surface 206 with a much shorter length than a base width 208, e.g. having a base edge to contact edge ratio greater than 1. Increasing a base edge to contact edge ratio may provide some benefits. For example, abrasive debris (e.g. swarf) is created during an abrasive operation and can collect on the surface of the abrasive article, reducing the efficacy of the abrasive article overtime. Increasing a base edge to contact edge ratio increases a volume between adjacent precisely shaped abrasive composites 200, which may allow for abrasive debris to be more easily removed from the abrading area. Additionally, increasing a base edge to contact edge ratio may also increase the pressure exerted along the contact surface as a force is applied to the abrasive article.

[0099] In embodiments herein, the base edge to contact edge ratio is greater than or equal to 1. In some embodiments herein, the base edge to contact edge ratio is greater than or equal to 1.2. In some embodiments herein, the base edge to contact edge ratio is greater than or equal to1.5. In some embodiments herein, the base edge to contact edge ratio is greater than or equal to1.8. In some embodiments herein, the base edge to contact edge ratio is greater than or equal to2.0. In some embodiments herein, the base edge to contact edge ratio is greater than or equal to2.5.

[0100] FIG. 3C illustrates an embodiment where a base edge to contact edge ratio is significantly higher, such that contact surface 206 is a vertex where the relief face, rake face, and triangular faces meet. While FIG. 3C illustrates an embodiment where contact surface 206 is a point, it is expressly contemplated that contact surface 206 may have a rounded surface.

[0101] FIG. 3C also illustrates an embodiment where a contact surface 206 is not centered with respect to a base surface 208. FIGS. 3A-3B illustrated embodiments where relief face and rake face were regular trapezoids having a set of parallel sides (contacting surface and base edge) and a set of non-parallel sides of substantially equal length and substantially equal anglesadjacent the base. However, it is expressly contemplated that other trapezoidal shapes are possible - FIG. 3C illustrates an embodiment where rake face includes a right angle along a rake face edge 224, e.g. the edge where the rake face and the base meet. In the illustrated embodiment, at least one of the triangular faces of the abrasive composite also includes a right angle such that the contact surface 206 is substantially in line with a comer of the base.However, it is expressly contemplated that the contact surface 206 may be positioned elsewhere with respect to the base. In some embodiments, an abrasive composite has a contact surface 206 that is centered with respect to rake face edge 224. In other embodiments, an abrasive composite has a contact surface 206 that is off-center with respect to rake face edge 224.

[0102] FIG. 3D illustrates an embodiment where a cutting surface 206 has texture 224. Cutting surface 260, in the embodiment of FIG. 3D, includes a sawtooth texture formed of a number of small peaks and valleys. However, it is expressly contemplated that other shapes may be suitable for texture 224, such as rounded peaks, other polygonal structures, sinusoidal patterns, irregular raised features, etc. Texture 226 may include other patterned or random structure as well.

[0103] Texture 224 may have a texture height 226, measured as the difference between the highest point and the lowest point of texture 224. A ratio of texture height to abrasive composite height may be less than 0.5 in some embodiments herein. A ratio of texture height to abrasive composite height may even be less than 0.4, in some embodiments. A ratio of texture height to abrasive composite height may even be less than 0.3, in some embodiments. A ratio of texture height 226 to abrasive composite height may even be less than 0.2, in some embodiments. A ratio of texture height to abrasive composite height may even be less than 0.1, in some embodiments. A ratio of texture height to abrasive composite height may even be less than 0.05, in some embodiments.

[0104] Fig. 3E illustrates an embodiment of a truncated precisely shaped abrasive composite 200 shaped such that the relief face 204 is spaced apart from a base face. The precisely shaped abrasive composite, instead of having two triangular faces, has two trapezoidal faces opposing one another. Instead of having five total faces, abrasive composite 200 also includes a trailing face 232, which has a height 228. While FIG. 3E illustrates a trailing face 232 that appears rectangular, it is expressly contemplated that trailing face 232 is trapezoidal in shape in some embodiments.

[0105] FIGS. 3F-3H illustrate examples of precisely-shaped abrasive composites having different rake angles. FIG. 3F illustrates an example of a precisely-shaped abrasive composite having a positive rake angle 242. FIG. 3G illustrates an example of a precisely-shaped abrasivecomposite having a negative rake angle 244. FIG. 3G illustrates an example of a precisely- shaped abrasive composite having a neutral rake angle 246.

[0106] However, while FIGS. 3F-3H illustrate a few example rake angles, it is expressly contemplated that precisely-shaped abrasive composites 200 in accordance with embodiments herein may have a range of positive or negative rake angle 210. For example, a rake angle between the abrasive composite and a worksurface between 30°-150°, or between 40°-140°, or between 50°-130°, or between 60°-120°, or between 70°-l 10°, or between 80°-100°. Angle 210 may be at least 30°, or at least 40°, or at least 50°, or at least 60°, or at least 70°, or at least 80°, or at least 90°, or at least 100°, or at least 110°, or at least 120°, or at least 130°, or at least 140°, or at least 150°.

[0107] Described herein are precisely-shaped abrasive composites having purposely-shaped faces, for example formed using a mold. The faces are described herein based on a polygon they represent. However, it is expressly contemplated that, for example, edges or comers of precisely-shaped abrasive composites herein may be rounded. A “substantially-triangular” or “substantially-trapezoidal” shaped face may, therefore, resemble a trapezoid with one or more of its three comers being rounded comers. The comers may be purposely rounded, in some embodiments. In other embodiments, the roundness of an edge or tip may be due to limitations in molding, for example collecting of a release agent in a mold recess, or tooling limitations in forming the mold.

[0108] Precisely-shaped abrasive composite 200 may be defined in part by an aspect ratio - a ratio of a thickness (e.g. an average between the lengths of contact surface 206 and base width 208) to a length of base surface 202. Precisely-shaped abrasive composite 200 may have an aspect ratio of thickness: length of greater than 1, but less than 3. In some embodiments, the aspect ratio may be less than 2, or even less than 1.9, or even less than 1.8, or even less than 1.7, or even less than 1.6, or even less than 1.5.

[0109] In some embodiments, a base length 202 of precisely-shaped abrasive composite 200 is between 500-2000 pm. In some embodiments, a base length 202 is between 700-1500 pm. In some embodiments, a base length 202 is between 800-1200 pm. In some embodiments, a height of the precisely-shaped abrasive composite 200 220 is between 300-1200 pm. In some embodiments, height 220 is between 500-900 pm. In some embodiments, height 220 is between 500-700 pm. In some embodiments, a length of cutting surface 206 is between 400-900 pm. In some embodiments, a length of cutting surface 206 is between 500-800 pm. In some embodiments, a length of cutting surface 206 is between 600-700 pm. In some embodiments, abase width 208 is between 500-2000 pm. In some embodiments, a base width 208 is between 700-1500 pm. In some embodiments, a base width 208 is between 900-1000 pm.

[0110] In some embodiments, relief angle 212 is between 15-60°, or between 20-50°, or between 30-40°.

[0111] It is noted that, in contrast to previous designs (e.g. designs of FIGS. 1-2 and FIGS 7B-7D, discussed below), the precisely-shaped abrasive composite 200 has only one plane of symmetry - extending from a midpoint of edge 208 and a midpoint of edge 206, through surface 204. However, it is expressly contemplated that, in some embodiments, the precisely-shaped abrasive composite 200 has no planes of symmetry.

[0112] Precisely-shaped abrasive composite 200, in contrast to at least some previous abrasive composite shapes for abrading glass, has a rectangular cutting surface 206 instead of a flat or rounded abrading surface, as seen in some previous shapes for abrasive composites. Generally, rounded surface or cutting tips have been used.

[0113] FIGS. 4A-4E illustrate abrasive layers formed from a number of precisely-shaped abrasive composites arranged in repeating patterns in accordance with embodiments herein. It is expressly contemplated that, while FIGS. 4A-4C illustrate three example patterns, many other patterns are possible in accordance with embodiments herein.

[0114] FIG. 4A illustrates an abrasive layer 250 formed of a number of precisely-shaped abrasive composites 200, each having a cutting surface 206. In some embodiments, a plurality of precisely-shaped abrasive composites 200 are formed as a unitary structure with a base layer 260.

[0115] Abrasive layer 250 is formed of precisely-shaped abrasive composites 200 that are formed such that each precisely-shaped abrasive composite 200 is adjacent a next precisely shaped abrasive composite 200. In some embodiments, abrasive composites 200 are spaced apart from adjacent composites. In other embodiments, as indicated by spacing 252, adjacent abrasive composites are in contact along a base length and / or a base width. As noted above, having a cutting surface 206 that is shorter in length than a relief face length 222 results in a volume between adjacent abrasive composites that can act as a channel to allow for abrading fluid to enter an abrading contact area and / or for fluid to remove debris from the abrading contact area. In some embodiments, a consistent spacing 252 is present between adjacent precisely shaped abrasive composites 200. Spacing 252 may be less than 10% of a base length 202, or less than 8% of base length 202, or less than 6% of a base length 202, or even less than 4% of a base length.

[0116] In some embodiments, cutting surfaces 206 of the precisely-shaped abrasive composite structures 250 exist in a plane parallel to the substrate surface for a substantial amount of the surface area of the abrasive material product. A height 220 of the precisely-shaped abrasive composites, from the substrate surface, may be between 300 to 1000 pm in some embodiments, or between 400-900 pm, or between 500-800 pm. Variation in height of the apexes is preferably within 20% of average height of the shaped structures and more preferably within 10%.

[0117] As described above, precisely-shaped abrasive composite 200 is formed, generally from abrasive particles in a resin binder. It is noted that, in at least some embodiments herein, the abrasive particles are not projected beyond the surface of the shape of the shaped structures. That is, the shaped structures are composed of smooth surfaces. For example, the surfaces composing the shaped structures have surface roughness Ry of 2 pm or less and in one embodiment, 1 pm or less.

[0118] In the shaped structures, the cutting edge 206 exhibit abrading function. During the use of the abrasive material product for abrading, the precisely-shaped abrasive composites are decomposed from the cutting edge 206 and unused abrasive particles appear. Accordingly, it may be preferable to increase concentration of the abrasive particles existing in the upper layer 4 of the precisely-shaped abrasive composites 200, in order to increase cutting property of the abrasive material product. It is because cutting property of the abrasive material product is improved and the abrasive material product becomes suitable for use in abrading hard materials.

[0119] In some embodiment, precisely-shaped abrasive composite 200 is formed of a series of discrete layers having an increasing concentration of abrasive particles going from base surface edge 202 to cutting edge 206. In some embodiments, at least 2 layers are present, or at least 3 layers, or even at least 4 layers. In some embodiments, discrete layers of varying abrasive particle concentrations are not present, but a concentration of abrasive particles generally increases going from the base surface edge 202 to the cutting edge 206.

[0120] FIG. 4A illustrates an embodiment where each precisely-shaped abrasive composite has the same orientation - e.g. cutting surfaces 206 and base lengths 202 of one precisely-shaped abrasive composites are substantially parallel to each other. However, it is expressly contemplated that other patterns are possible. Abrasive layer 250 includes a number of precisely-shaped abrasive composites 200 that are precisely positioned with respect to each other. Precise positioning can be used to make different patterns of abrasive composites.

[0121] FIG. 4B, for example, illustrates an embodiment where abrasive composites in an abrasive layer 252 are in opposing orientations in adjacent columns. It is expresslycontemplated that abrasive composites could also have opposing orientations by adjacent rows instead.

[0122] FIG. 4C illustrates an embodiment where abrasive composites in an abrasive layer 254 have opposing orientations in both adjacent rows and columns, e.g. like a chess board.

[0123] However, it is expressly contemplated that additional patterns are possible using abrasive composites herein. For example, illustrated in FIGS. 3-4 are embodiments where a base surface is rectangular in shape - e.g. having a base length 202 that is longer than base width 208. However, it is expressly contemplated that base length 202 and base width 208 may be substantially similar, or equal, in some embodiments such that the base surface has a square profile. In such embodiments, instead of opposing orientations, orientations of adjacent abrasive composites may be offset by 90°, 180°, or 270° by adjacent rows, columns, or both.

[0124] Additionally, FIGS. 4A-4C illustrate abrasive layers having clear rows and columns because adjacent abrasive composites have base surfaces that are in-line with each other.However, it is expressly contemplated that abrasive composites can be placed such that they are offset in adjacent rows or columns.

[0125] FIG. 4D illustrates an embodiment where adjacent columns of abrasive composites are offset from each other by an offset 260, which may be expressed as a portion of base length 202. For example, the offset may be greater than or equal to 5% of base length 202, greater than or equal to 10% of base length 202, greater than or equal to 15% of base length 202, greater than or equal to 20% of base length 202, greater than or equal to 25% of base length 202, greater than or equal to 30% of base length 202, greater than or equal to 30% of base length 202, greater than or equal to 40% of base length 202, greater than or equal to 45% of base length 202, greater than or equal to 50% of base length 202, greater than or equal to 55% of base length 202, greater than or equal to 60% of base length 202, greater than or equal to 65% of base length 202, greater than or equal to 70% of base length 202, greater than or equal to 75% of base length 202, greater than or equal to 80% of base length 202, greater than or equal to 85% of base length 202, greater than or equal to 90% of base length 202, greater than or equal to 95% of base length 202.

[0126] Similarly, the offset may be less than or equal to 95% of base length 202, less than or equal to 90% of base length 202, less than or equal to 85% of base length 202, less than or equal to 80% of base length 202, less than or equal to 75% of base length 202, less than or equal to 70% of base length 202, less than or equal to 65% of base length 202, less than or equal to 60% of base length 202, less than or equal to 55% of base length 202, less than or equal to 50% of base length 202, less than or equal to 45% of base length 202, less than or equal to 40% of base length 202, less than or equal to 35% of base length 202, less than or equal to 30% of baselength 202, less than or equal to 25% of base length 202, less than or equal to 20% of base length 202, less than or equal to 15% of base length 202, less than or equal to 10% of base length 202, less than or equal to 5% of base length 202.

[0127] Additionally, while FIG. 4D illustrates an embodiment where adjacent columns of abrasive composites have opposing orientations and offsets by column, it is expressly contemplated that other combinations of features are possible. For example, adjacent rows of abrasive composites may have an offset 260, and all abrasive composites have the same orientation. Other combinations are expressly possible.

[0128] FIG. 4E illustrates a side-view of a row of abrasive composites having multiple shapes of abrasive composites. While FIGS. 4A-4D illustrate embodiments where a single shape of abrasive composite is used across an abrasive layer, it is expressly contemplated that different shapes may be used. The different shapes may be arranged in a repeating pattern across rows and / or columns. In the embodiment illustrated in FIG. 4E, both abrasive composites have the same base length, although it is expressly contemplated that other embodiments are possible.

[0129] Different shapes may allow for an abrasive article having an abrasive layer to have different abrasive properties when used in different directions. For example, when used in a first machine direction 266, abrasive composites have rake angles 264. If used in an opposite direction, abrasive composites have rake angles 262. The combination of different orientations and different shapes may allow for more fine tuning of abrasive layers for different applications.

[0130] Precisely shaped abrasive composites, and abrasive layers containing the same, may be useful for a number of different abrasive applications. The ability to customize the composition of the shape - e.g. using different binder materials and / or abrasive particles makes the precisely-shaped abrasive composites herein versatile. Diamond-containing abrasive tools may be used to improve the surface finish of perimeter edges and feature perimeter edges of a coverglass machining process. Such diamond abrasive tools include metal bonded diamond tools, such as plated, sintered and brazed metal bonded diamond tools. Metal bonded diamond tools may provide relatively high durability and effective cutting rates, but may leave microcracks in the glass that are stress points that can be the initiation points for breakage, significantly reducing the strength of a finished coverglass below its potential facture resistance.

[0131] However, while the example of a coverglass machining process is described in greater detail below, it is expressly contemplated that precisely shaped abrasive composites and layers of abrasive composites like those described with respect to FIGS. 3 and 4 may be useful in other applications as well. For example, microfinishing film often contains precisely-shapedabrasive composites and may also benefit from inclusion of precisely-shaped abrasive composites of embodiments herein.

[0132] To improve the strength and / or appearance of coverglass, the edges can be polished following a grinding of machined edges, using, for example, a cerium oxide (CeO) based coolant, to remove grinding and machining marks in the coverglass. However, such edge polishing can be lengthy for a coverglass, up to many hours in order to provide a desired surface finish for all edges of a coverglass. For example, polishing of a single coverglass many required steps to effectively polish all edges, including the perimeter, holes and comers. Polishing machines can be relatively large and expensive, and unique to the particular feature being polished. For this reason, production of coverglass in a manufacturing environment may include a number of parallel polishing lines, each including a number of polishing machines, in order to provide a desired production capacity of coverglass for the facility. Reducing processing time would allow an increase in the throughput of each polishing line.

[0133] In addition, polishing slurries may be inconsistent such that the polishing of a coverglass is not precisely predictable. Polishing may also cause an undesirable rounding of the comers following the relatively precise shaping provided by the grinding operations. In general, longer polishing provides an improved surface finish, but a greater rounding effect and less precision for the final dimensions of the coverglass. Reducing processing time to provide desired surface finish qualities of a coverglass may not only reduce production time, but may also provide more precise dimensional control for the production of coverglass. The abrasive compounds and tools disclosed herein may facilitate such a reduction in processing time for the production of coverglass.

[0134] FIGS. 5A-5G illustrate a rotary abrasive system, substrate, and tool in which embodiments herein may be particularly useful. FIG. 5 A illustrates system 310, which includes rotary machine 323 and rotary machine controller 330. Controller 330 is configured to send control signals to rotary machine 323 for causing rotary machine 323 to machine, grind or abrade component 324 with rotary tool 328, which is mounted within spindle 326 of rotary machine 323. For example, component 324 may be a coverglass, such as coverglass 350 (FIG. 5C). In one example, rotary machine 323 may represent a CNC machine, such as a three, four or five axis CNC machine, capable of performing routing, turning, drilling, milling, grinding, abrading, and / or other machining operations, and controller 330 may include a CNC controller that issues instructions to spindle 326 for performing machining, grinding and / or abrading of component 324 with one or more rotary tools 328. Controller 330 may include a general-purposecomputer running software, and such a computer may combine with a CNC controller to provide the functionality of controller 330.

[0135] Component 324 is mounted to platform 338 in a manner that facilitates precise machining of component 324 by rotary machine 323. Work holding fixture 318 secures component 324 to platform 338 and precisely locates component 324 relative to rotary machine 323. Work holding fixture 318 may also provide a reference location for control programs of rotary machine 323. While the techniques disclosed herein may apply to workpieces of any materials, component 324 may be a coverglass for an electronic device, such as a coverglass of a smartphone touchscreen.

[0136] In the example of FIG. 5A, rotary tool 328 is illustrated as including abrasive surface 329. In this example, abrasive surface 329 may be utilized to improve the surface finish of machined features in component 324, such as holes and edge features in a coverglass. In some example, different rotary tools 328 may be used in series to iteratively improve the surface finish of the machined features. For example, system 310 may be utilized to provide a coarser grinding step using a fist rotary tool 328, or set of rotary tools 328, followed by a finer abrading step using a second rotary tool 328, or set of rotary tools 328. In the same or different examples, a single rotary tool 328 may include different levels of abrasion to facilitate an iterative grinding and / or abrading process using fewer rotary tools 328. Each of these examples may reduce the cycle time for finishing and polishing a coverglass following the machining of the features in the coverglass as compared to other examples in which only a single grinding step is used to improve surface finish following machining of features in a coverglass.

[0137] In some examples, following grinding and / or abrading using system 310, a coverglass may be polished, e.g., using a separate polishing system to further improve the surface finish. In general, the better the surface finish prior to polishing, the less time is required to provide a desired surface finish following the polishing.

[0138] To abrade an edge of component 324 with system 310, controller 330 may issue instructions to spindle 326 to precisely apply abrasive surface 329 against one or more features of component 324 as spindle 326 rotates rotary tool 328. The instructions may include for example, instructions to precise follow the contours of features of component 324 with a single abrasive surface 329 of a rotary tool 328 as well as iteratively apply multiple abrasive surfaces 329 of one or more rotary tools 328 to different features of component 324.

[0139] In illustrative examples, a base layer of the abrasive surface 329 may be formed of a polymeric material. For example, the base layer may be formed from thermoplastics, for example; polypropylene, polyethylene, polycarbonate, polyurethane, polytetrafluoroethylene,polyethylene teraphthalate, polyethylene oxide, polysulphone, polyetherketone, polyetheretherketone, polyimides, polyphenylene sulfide, polystyrene, polyoxymethylene plastic, and the like; thermosets, for example polyurethanes, epoxy resin, phenoxy resins, phenolic resins, melamine resins, polyimides and urea-formaldehyde resins, radiation cured resins, or combinations thereof. The base layer may consist essentially of only one layer of material, or it may have a multilayered construction. For example, the base layer may include a plurality of layers, or layer stack, with the individual layers of the stack being coupled to one another with a suitable fastening mechanism (e.g., adhesive and / or primer layer). The base layer (or an individual layer of the layer stack) may have any shape and thickness. The thickness of the base layer (i.e., the dimension of the base layer in a direction normal to the first and second major surfaces) may be less than 10 mm, less than 5 mm, less than 1 mm, less than 0.5 mm, less than 0.25 mm, less than 0. 125 mm, or less than 0.05 mm.

[0140] In some examples, abrasive surface 329 may be formed as a two-dimensional abrasive material, such as a convention abrasive sheet with a layer of abrasive particles held to a backing by one or more resin or other binder layers, such abrasive sheet may then be applied to a rotary tool substrate. Alternatively, abrasive surface 329 may be formed as a three-dimensional fixed abrasive, such as a resin or other binder layer that contains abrasive particles dispersed therein. The combination of abrasive particles and resin or binder, is herein referred to as an abrasive composite. In either example, abrasive surface 329 may include an abrasive composite which has appropriate height to allow for the abrasive composite to wear during use and / or dressing to expose a fresh layer of abrasive particles. The abrasive article may comprise a three- dimensional, textured, flexible, fixed abrasive construction including a plurality of precisely shaped abrasive composites.

[0141] The precisely shaped abrasive composites may be arranged in an array to form the three-dimensional, textured, flexible, fixed abrasive construction. Suitable arrays include, for instance, those described in U.S. Pat. No. 5,958,794 (Bruxvoort et al.). The abrasive article may comprise abrasive constructions that are patterned. Abrasive articles available under the trade designation TRIZACT patterned abrasive and TRIZACT diamond tile abrasives available from 3M Company, St. Paul, Minnesota, are exemplary patterned abrasives. Patterned abrasive articles include monolithic rows of abrasive composites precisely aligned and manufactured from a die, mold, or other techniques. Such patterned abrasive articles can abrade, polish, or simultaneously abrade and polish.

[0142] The shape of each precisely shaped abrasive composite may be selected for the particular application (e.g., workpiece material, working surface shape, contact surface shape,temperature, resin phase material). The shape of each precisely shaped abrasive composite may be any useful shape, e.g., cubic, cylindrical, prismatic, right parallelepiped, pyramidal, truncated pyramidal, conical, hemispherical, truncated conical, cross, or post-like sections with a distal end. Composite pyramids may, for instance, have three, four sides, five sides, or six sides.

[0143] In at least some embodiments herein the shape of each precisely-shaped abrasive composite may be a wedge-shaped, having a first triangular surface opposite a second triangular surface. The wedge-shaped abrasive composite may have one or more faces that are quadrilateral in shape, e.g. having four comers and edges. In some embodiments, at least one surface is a trapezoid in shape. In some embodiments, at least two surfaces are trapezoids. In some embodiments, at least one surface is a rectangle.

[0144] The cross-sectional shape of the abrasive composite at the base may differ from the cross-sectional shape at the distal end. The transition between these shapes may be smooth and continuous or may occur in discrete steps. The precisely shaped abrasive composites may also have a mixture of different shapes. The precisely shaped abrasive composites may be arranged in rows, spiral, helix, or lattice fashion, or may be randomly placed. The precisely shaped abrasive composites may be arranged in a design meant to guide fluid flow and / or facilitate swarf removal. As discussed above, the precisely shaped abrasive composites may also have the same or different orientation relative to adjacent shaped abrasive composites in any of the arrangements described herein.

[0145] One or more of the lateral sides forming the precisely shaped abrasive composite may be tapered with diminishing width toward the distal end. The tapered angle may be from about 1 to less than 90 degrees, for instance, from about 1 to about 75 degrees, from about 3 to about 35 degrees, or from about 5 to about 15 degrees. The height of each precisely shaped abrasive composite is preferably the same, but it is possible to have precisely shaped abrasive composites of varying heights in a single article.

[0146] The base of the precisely shaped abrasive composites, as illustrated in FIGS. 4A-4C may abut one another or, alternatively, the bases of adjacent precisely shaped abrasive composites may be separated from one another by some specified distance. In some examples, the physical contact between adjacent abrasive composites involves no more than 33% of the vertical height dimension of each contacting precisely shaped abrasive composite, or even no more than 25% of the vertical height dimension. This definition of abutting also includes an arrangement where adjacent precisely shaped abrasive composites share a common land or bridge-like structure which contacts and extends between facing lateral surfaces of the precisely shaped abrasive composites. The abrasives are adjacent in the sense that no interveningcomposite is located on a direct imaginary line drawn between the centers of the precisely shaped abrasive composites.

[0147] The precisely shaped abrasive composites may be set out in a predetermined pattern or at a predetermined location within the abrasive article. For example, when the abrasive article is made by providing an abrasive / resin slurry between a backing and mold, the predetermined pattern of the precisely shaped abrasive composites will correspond to the pattern of the mold. The pattern is thus reproducible from abrasive article to abrasive article.

[0148] The predetermined patterns may be in an array or arrangement, by which is meant that the composites are in a designed array such as aligned rows and columns, or alternating offset rows and columns. In another example, the abrasive composites may be set out in a "random" array or pattern. By this is meant that the composites are not in a regular array of rows and columns as described above. It is understood, however, that this "random" array is a predetermined pattern in that the location of the precisely shaped abrasive composites is predetermined and corresponds to the mold.

[0149] An abrasive material forming abrasive surface 329 may include a polymeric material, such as a resin. In some examples, the resin phase may include a cured or curable organic material. The method of curing is not critical, and may include, for instance, curing via energy such as UV light or heat. Examples of suitable resin phase materials include, for instance, amino resins, alkylated urea-formaldehyde resins, melamine-formaldehyde resins, and alkylated benzoguanamine -formaldehyde resins. Other resin phase materials include, for instance, acrylate resins (including acrylates and methacrylates), phenolic resins, urethane resins, and epoxy resins. Particular acrylate resins include, for instance, vinyl acrylates, acrylated epoxies, acrylated urethanes, acrylated oils, and acrylated silicones. Particular phenolic resins include, for instance, resole and novolac resins, and phenolic / latex resins. In the same or different examples, the resin may include one or more of an epoxy resin, a polyester resin, a polyvinyl butyral (PVB) resin, an acrylic resin, thermal plastic resin, a thermally curable resin, an ultraviolet light curable resin, and an electromagnetic radiation curable resin. For example, an epoxy resin may represent between about 20 percent to about 35 percent by weight of the abrasive material. In the same or different examples, a polyester resin represents between 1 percent to 10 percent by weight of the abrasive material. The resins may further contain conventional fdlers and curing agents such as are described, for instance, in U.S. Pat. No. 5,958,794 (Bruxvoort et al.), incorporated herein by reference.

[0150] Examples of suitable abrasive particles for the fixed abrasive pad include cubic boron nitride, fused aluminum oxide, ceramic aluminum oxide, heat treated aluminum oxide, whitefused aluminum oxide, black silicon carbide, green silicon carbide, titanium diboride, boron carbide, silicon nitride, tungsten carbide, titanium carbide, diamond, cubic boron nitride, cerium oxide, chromium oxide, hexagonal boron nitride, alumina zirconia, iron oxide, ceria, garnet, alumina zirconia, alumina-based sol gel derived abrasive particles and the like, as well as mixtures thereof. The alumina abrasive particle may contain a metal oxide modifier. Examples of alumina-based sol gel derived abrasive particles can be found in U.S. Pat. Nos. 4,314,827; 4,623,364; 4,744,802; 4,770,671; and 4,881,951, all incorporated by reference herein. The diamond and cubic boron nitride abrasive particles may be mono crystalline or polycrystalline. Particularly preferable examples are, for rough abrading, diamond, cubic boron nitride, aluminum oxide, and silicon carbide; for finishing abrading, silica and aluminum oxide.Additionally, in some embodiments, agglomerates of any of the above abrasive particles may be used, such as the agglomerates described in U.S. Pat. 5,039,311, issued August 13, 1991. Other examples of suitable inorganic abrasive particles include silica, iron oxide, chromia, ceria, zirconia, titania, tin oxide, gamma alumina, and the like.

[0151] In some examples, an abrasive surface 329 may further include a backing layer behind an abrasive composite layer, optionally with an adhesive interposed therebetween. Any variety of backing materials are contemplated, including both flexible backings and backings that are more rigid. Examples of flexible backings include, for instance, polymeric film, primed polymeric film, metal foil, cloth, paper, vulcanized fiber, nonwovens and treated versions thereof and combinations thereof. Examples include polymeric films of polyester, and copolyester, micro-voided polyester, polyimide, polycarbonate, polyamide, polyvinyl alcohol, polypropylene, polyethylene, and the like. When used as a backing, the thickness of a polymeric film backing is chosen such that a desired range of flexibility is retained in the abrasive article.

[0152] Useful backings include, for example, film backings and foam backings.

[0153] Suitable film backings include polymeric films and primed polymeric films, especially those used in the abrasive arts. Useful polymeric films include, for example, polyester films (for example, an ethylene-acrylic acid copolymer primed polyethylene terephthalate), polyolefin films (for example, polyethylene or polypropylene films), and elastic polyurethane films. The film backing may be a laminate of two polymeric films.

[0154] Useful polymeric foams include open cell and closed cell polymeric foams, typically compressible and resilient. Useful polymeric foams include elastic foams such as, for example, chloroprene rubber foams, ethylene / propylene rubber foams, butyl rubber foams, polybutadiene foams, polyisoprene foams, EPDM polymer foams, polyurethane foams, ethylene-vinyl acetate foams, neoprene foams, and styrene / butadiene copolymer foams. Useful foams also includethermoplastic foams such as, for example, polyethylene foams, polypropylene foams, polybutylene foams, polystyrene foams, polyamide foams, polyester foams, plasticized polyvinyl chloride (that is, PVC) foams. Examples of useful open cell foams include polyester polyurethane foams available from Illbruck, Inc. of Minneapolis, MN under the trade designations R 200U, R 400U, R 600U and EF3-700C.

[0155] Useful foam backings are generally from about 1 to about 15 millimeters in thickness; however, this is not a requirement.

[0156] The backing can have an attachment interface layer on its back surface to secure the abrasive article to a support pad or back-up pad. This attachment system half can be, for example, a pressure-sensitive adhesive or tape, a loop fabric for a hook and loop attachment, a hook structure for a hook and loop attachment, or an intermeshing attachment system. Further details concerning such attachment systems may be found, for example, in U.S. Pat. Nos. 5,152,917 (Pieper et al.); 5,454,844 (Hibbard et al.); 5,672,097 (Hoopman); 5,681,217 (Hoopman et al.); and U.S. Pat. Appl. Pub. Nos. 2003 / 0143938 Al (Braunschweig et al.) and 2003 / 0022604 Al (Annen et al.).

[0157] In some examples, an abrasive surface 329 may include one or more additional layers. For example, the abrasive surface may include adhesive layers such as pressure sensitive adhesives, hot melt adhesives, or epoxies. “Sub pads” such as thermoplastic layers, e.g. polycarbonate layers, which may impart greater stiffness to the pad, may be used for global planarity. Sub pads may also include elastically compressible material layers, e.g. foamed material layers. Sub pads which include combinations of both thermoplastic and compressible material layers may also be used. Additionally, or alternatively, metallic fdms for static elimination or sensor signal monitoring, optically clear layers for light transmission, foam layers for finer finish of the workpiece, or ribbed materials for imparting a “hard band” or stiff region to the polishing surface may be included.

[0158] As will be appreciated by those skilled in the art, abrasive surfaces can be formed according to a variety of methods including, e.g., molding, extruding, embossing and combinations thereof.

[0159] In illustrative examples, the abrasive composites may include porous ceramic abrasive composites. The porous ceramic abrasive composites may include individual abrasive particles dispersed in a porous ceramic matrix. As used herein the term “ceramic matrix” includes both glassy and crystalline ceramic materials. These materials generally fall within the same category when considering atomic structure. The bonding of the adjacent atoms is the result of process of electron transfer or electron sharing. Alternatively, weaker bonds as a resultof attraction of positive and negative charge known as secondary bond can exist. Crystalline ceramics, glass and glass ceramics have ionic and covalent bonding. Ionic bonding is achieved as a result of electron transfer from one atom to another. Covalent bonding is the result of sharing valence electrons and is highly directional. By way of comparison, the primary bond in metals is known as a metallic bond and involves non-directional sharing of electrons. Crystalline ceramics can be subdivided into silica-based silicates (such as fireclay, mullite, porcelain, and Portland cement), non-silicate oxides (e.g., alumna, magnesia, MgA12 04, and zirconia) and non-oxide ceramics (e.g., carbides, nitrides and graphite). Glass ceramics are comparable in composition with crystalline ceramics. As a result of specific processing techniques, these materials do not have the long-range order crystalline ceramics do. Glass ceramics are the result of controlled heat-treatment to produce at least about 30% crystalline phase and up to about 90% crystalline phase or phases.

[0160] In illustrative examples, at least a portion of the ceramic matrix includes glassy ceramic material. In further examples, the ceramic matrix includes at least 50% by weight, 70% by weight, 75% by weight, 80% by weight, or 90% by weight glassy ceramic material. In one example, the ceramic matrix consists essentially of glassy ceramic material. Of particular usefulness for edge grinding coverglass, the ceramic matrix includes at least 30% by weight glassy ceramic material.

[0161] In various examples, the ceramic matrixes may include glasses that include metal oxides, for example, aluminum oxide, boron oxide, silicon oxide, magnesium oxide, sodium oxide, manganese oxide, zinc oxide, and mixtures thereof. A ceramic matrix may include alumina-borosilicate glass including Si2O, B2O3, and A12O3. The alumina-borosilicate glass may include about 18% B2O3, 8.5% A12O3, 2.8% BaO, 1.1% CaO, 2.1% Na2O, 1.0% Li2O with the balance being Si2O. Such an alumina-borosilicate glass is commercially available from Specialty Glass Incorporated, Oldsmar Florida.

[0162] As used herein the term “porous” is used to describe the structure of the ceramic matrix which is characterized by having pores or voids distributed throughout its mass. A porous ceramic matrix may be formed by techniques well known in the art, for example, by controlled firing of a ceramic matrix precursor or by the inclusion of pore forming agents, for example, glass bubbles, in the ceramic matrix precursor. The pores may be open to the external surface of the composite or sealed. Pores in the ceramic matrix are believed to aid in the controlled breakdown of the ceramic abrasive composites leading to a release of used (i.e., dull) abrasive particles from the composites. The pores may also increase the performance (e.g., cut rate and surface finish) of the abrasive article, by providing a path for the removal of swarf and usedabrasive particles from the interface between the abrasive article and the workpiece. The voids (or pore volume) may be from about at least 4 volume % of the composite, at least 7 volume % of the composite, at least 10 volume % of the composite, or at least 20 volume % of the composite; less than 95 volume % of the composite, less than 90 volume % of the composite, less than 80 volume % of the composite, or less than 70 volume % of the composite. Of particular usefulness for edge grinding coverglass, the voids may comprise from between 35 percent to 65 percent by weight of the abrasive material.

[0163] In some examples, the abrasive particles may include diamond, cubic boron nitride, fused aluminum oxide, ceramic aluminum oxide, heated treated aluminum oxide, silicon carbide, boron carbide, alumina zirconia, iron oxide, ceria, garnet, and combinations thereof. In one example, the abrasive particles may include or consist essentially of diamond. Diamond abrasive particles may be natural or synthetically made diamond. The diamond particles may have a blocky shape with distinct facets associated with them or, alternatively, an irregular shape. The diamond particles may be mono-crystalline or polycrystalline such as diamond commercially available under the trade designation “Mypolex” from Mypodiamond Inc., Smithfield Pennsylvania. Monocrystalline diamond of various particles size may be obtained from Diamond Innovations, Worthington, Ohio. Poly crystalline diamond may be obtained from Tomei Corporation of America, Cedar Park, Texas. The diamond particles may contain a surface coating such as a metal coating (nickel, aluminum, copper or the like), an inorganic coating (for example, silica), or an organic coating.

[0164] In some examples, the abrasive particles may include a blend of abrasive particles. For example, diamond abrasive particles may be mixed with a second, softer type of abrasive particles. In such instance, the second abrasive particles may have a smaller average particle size than the diamond abrasive particles.

[0165] In illustrative examples, the abrasive particles may be uniformly (or substantially uniformly) distributed throughout the ceramic matrix. As used herein, “uniformly distributed” means that the unit average density of abrasive particles in a first portion of the composite particle does not vary by more than 20%, more than 15%, more than 10%, or more than 5% when compared with any second, different portion of the composite particle. This is in contrast to, for example, an abrasive composite particle having abrasive particles concentrated at the surface of the particle.

[0166] In various examples, the abrasive composite particles may also include optional additives such as fillers, coupling agents, surfactants, foam suppressors and the like. The amounts of these materials may be selected to provide desired properties. Additionally, theabrasive composite particles may include (or have adhered to an outer surface thereof) one or more parting agents. As will be discussed in further detail below, one or more parting agents may be used in the manufacture of the abrasive composite particles to prevent aggregation of the particles. Useful parting agents may include, for example, metal oxides (e.g, aluminum oxide), metal nitrides (e.g., silicon nitride), graphite, and combinations thereof.

[0167] In some examples, the abrasive composites useful in the articles and methods may have an average size (average major axial diameter or longest straight line between two points on a composite) of about at least 5 pm, at least 10 pm, at least 15 pm, or at least 20 pm; less than 1,000 pm, less than 500 pm, less than 200 pm, or less than 100 pm. Abrasive particles particularly useful for edge grinding coverglass may have an average particle size of less than about 65 pm and a max particle size of less than about 500 pm.

[0168] In illustrative examples, the average size of the abrasive composites is at least about 3 times the average size of the abrasive particles used in the composites, at least about 5 times the average size of the abrasive particles used in the composites, or at least about 10 times the average size of the abrasive particles used in the composites; less than 30 times the average size of the abrasive particles used in the composites, less than 20 times the average size of the abrasive particles used in the composites, or less than 10 times the average size of the abrasive particles used in the composites. Abrasive particles useful in the articles and methods may have an average particle size (average major axial diameter (or longest straight line between two points on a particle)) of at least about 0.5 pm, at least about 1 pm, or at least about 3 pm, less than about 300 pm, less than about 100 pm, or less than about 50 pm. The abrasive particle size may be selected to, for example, provide a desired cut rate and / or desired surface roughness on a workpiece. The abrasive particles in some embodiments may have a Mohs hardness of at least 6, or of at least 7, or of at least 8, at least 9, or at least 10. However, it is expressly contemplated that, for some embodiments, abrasive articles may be used that have a Mohs hardness of less than 6.

[0169] In various examples, the weight of abrasive particles to the weight of glassy ceramic material in the ceramic matrix of the ceramic abrasive composites is at least about 1 / 20, at least about 1 / 10, at least about 1 / 6, at least about 1 / 3, less than about 30 / 1, less than about 20 / 1, less than about 15 / 1 or less than about 10 / 1.

[0170] In various examples, a ratio of abrasive particle size to agglomerate size may be no greater than 15 to 1, of no greater than 12.5 to 1, of no greater than 10 to 1. In some examples, a ratio of abrasive size to agglomerate size may also be no less than about 3 to 1, no less thanabout 5 to 1 or even no less than about 7 to 1. Ceramic abrasive composites providing such ratios of abrasive size to agglomerate size may be particularly useful for edge grinding coverglass.

[0171] In various examples, the abrasive composites may be sized and shaped relative to the size and shape of the cavities of the abrasive surface 329 such that one or more (up to all) of the abrasive composites may be at least partially disposed within a cavity. More specifically, abrasive composites may be sized and shaped relative to the cavities such that one or more (up to all) of the abrasive composites, when fully received by a cavity, has at least a portion that extends beyond the cavity opening. As used herein, the phrase “fully received,” as it relates to the position of a composite within a cavity, refers to the deepest position the composite may achieve within a cavity upon application of a non-destructive compressive force (such as that which is present during a polishing operation, as discussed below). In this manner, a polishing operation, the abrasive composite particles of the polishing solution may be received in and retained by (e.g., via frictional forces) the cavities, thereby functioning as an abrasive working surface.

[0172] In various examples, the amount of porous ceramic matrix in the ceramic abrasive composites is at least 5, at least 10, at least 15, at least 33, less than 95, less than 90, less than 80, or less than 70 weight percent of the total weight of the porous ceramic matrix and the individual abrasive particles, where the ceramic matrix includes any fdlers, adhered parting agent and / or other additives other than the abrasive particles.

[0173] In various examples, the abrasive composite particles may be precisely-shaped or irregularly shaped (i.e., non-precisely-shaped). Precisely-shaped ceramic abrasive composites may be any shape (e.g., cubic, block-like, cylindrical, prismatic, pyramidal, truncated pyramidal, conical, truncated conical, spherical, hemispherical, cross, or post-like). The abrasive composite particles may be a mixture of different abrasive composite shapes and / or sizes. Alternatively, the abrasive composite particles may have the same (or substantially the same) shape and / or size. Non-precisely shaped particles include spheroids, which may be formed from, for example, a spray drying process.

[0174] The abrasive composite particles may be formed by any particle forming processes including, for example, casting, replication, microreplication, molding, spraying, spray-drying, atomizing, coating, plating, depositing, heating, curing, cooling, solidification, compressing, compacting, extrusion, sintering, braising, atomization, infiltration, impregnation, vacuumization, blasting, breaking (depending on the choice of the matrix material) or any other available method. The composites may be formed as a larger article and then broken into smaller pieces, as for example, by crushing or by breaking along score lines within the larger article. Ifthe composites are formed initially as a larger body, it may be desirable to select for use fragments within a narrower size range by one of the methods known to those familiar with the art. In some examples, the ceramic abrasive composites may include vitreous bonded diamond agglomerates produced generally using techniques disclosed in of U.S. Patent Nos. 6,551,366 and 6,319, 108. Of particular usefulness for edge grinding coverglass, a volume ratio of diamond agglomerates to a resin binder within the abrasive is greater than 3 to 2.

[0175] Of particular usefulness for edge grinding coverglass, the ceramic abrasive agglomerates may represent between 35 percent to 65 percent by weight of the abrasive material.

[0176] Generally, a method for making the ceramic abrasive composite includes mixing an organic binder, solvent, abrasive particles, e.g. diamond, and ceramic matrix precursor particles, e.g. glass frit; spray drying the mixture at elevated temperatures producing “green” abrasive / ceramic matrix / binder particles; the “green” abrasive / ceramic matrix / binder particles are collected and mixed with a parting agent, e.g. plated white alumina; the powder mixture is then annealed at a temperature sufficient to vitrify the ceramic matrix material that contains the abrasive particles while removing the binder through combustion; forming the ceramic abrasive composite. The ceramic abrasive composites can optionally be sieved to the desired particle size. The parting agent prevents the “green” abrasive / ceramic matrix / binder particles from aggregating together during the vitrifying process. This enables the vitrified, ceramic abrasive composites to maintain a similar size as that of the “green” abrasive / ceramic matrix / binder particles formed directly out of the spray drier. A small weight fraction, less than 10%, less 5% or even less than 1% of the parting agent may adhere to the outer surface of the ceramic matrix during the vitrifying process. The parting agent typically has a softening point (for glass materials and the like), or melting point (for crystalline materials and the like), or decomposition temperature, greater than the softening point of the ceramic matrix, wherein it is understood that not all materials have each of a melting point, a softening point, or a decomposition temperature. For a material that does have two or more of a melting point, a softening point, or a decomposition temperature, it is understood that the lower of the melting point, softening point, or decomposition temperature is greater than the softening point of the ceramic matrix.Examples of useful parting agents include, but are not limited to, metal oxides (e.g. aluminum oxide), metal nitrides (e.g. silicon nitride) and graphite.

[0177] In some examples, the abrasive composite particles may be surface modified (e.g., covalently, ionically, or mechanically) with reagents which will impart properties beneficial to abrasive slurries. For example, surfaces of glass can be etched with acids or bases to create appropriate surface pH. Covalently modified surfaces can be created by reacting the particleswith a surface treatment comprising one or more surface treatment agents. Examples of suitable surface treatment agents include silanes, titanates, zirconates, organophosphates, and organosulfonates. Examples of silane surface treatment agents suitable for this invention include octyltriethoxysilane, vinyl silanes (e.g., vinyltrimethoxysilane and vinyl triethoxysilane), tetramethyl chloro silane, methyltrimethoxy silane, methyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, tris-[3-(trimethoxysilyl)propyl] isocyanurate, vinyl-tris-(2-methoxyethoxy)silane, gamm-methacryloxypropyltrimethoxysilane, beta-(3,4- epoxycyclohexyl)ethyltrimethoxysilane, gamma-glycidoxypropyltrimethoxysilane gammamercaptopropyltrimethoxy silane, gamma-aminopropyltriethoxysilane, gammaaminopropyltrimethoxy silane, N-beta-(aminoethyl)-gamma-aminopropyltrimethoxysilane, bis- (gamma-trimethoxysilylpropyl)amine, N-phenyl-gamma-aminopropyltrimethoxy silane, gamma- ureidopropyltrialkoxy silane, gamma-ureidopropyltrimethoxysilane, acryloxyalkyl trimethoxy silane, methacryloxyalkyl trimethoxy silane, phenyl trichlorosilane, phenyltrimethoxy silane, phenyl triethoxysilane, SILQUEST A1230 proprietary non-ionic silane dispersing agent (available from Momentive, Columbus, Ohio) and mixtures thereof. Examples of commercially available surface treatment agents include SILQUEST A174 and SILQUEST A1230 (available from Momentive). The surface treatment agents may be used to adjust the hydrophobic or hydrophilic nature of the surface it is modifying. Vinyl silanes can be used to provide an even more sophisticated surface modification by reacting the vinyl group w / another reagent. Reactive or inert metals can be combined with the glass diamond particles to chemically or physically change the surface. Sputtering, vacuum evaporation, chemical vapor deposition (CVD) or molten metal techniques can be used.

[0178] As another example, the abrasive material may include metal particles dispersed within the resin in combination with the abrasive composite particles. Metal particles may provide a bearing effect to protect the resin during a grinding operation. Such metal particles may include one or more of copper particles, tin particles, brass particles, aluminum particles, stainless steel particles and metal alloys. For example, the metal particles may represent between 5 percent to 25 percent by weight of the abrasive material. In the same or different examples, the metal particles may have an average particle size of between 10 micrometers to 250 micrometers, such as between 44 micrometers to 149 micrometers, such as about 100 micrometers. Such examples may be particularly useful for abrasive materials used for edge grinding coverglass.

[0179] Polymethyl methacrylate beads are another optional additive that may be dispersed within the resin of the abrasive material. In such examples, the polymethyl methacrylate beadsmay represent between 1 percent to 10 percent by weight of the abrasive material. Such examples may be particularly useful for abrasive materials used for edge grinding coverglass.

[0180] In addition to resin, such as epoxy resin, and abrasive composite particles, the abrasive material may include additional additives, such as a fdler material or other material. In some examples, a fdler material may include one or more of aluminum oxide, non-woven fibers, silicon carbide and ceria particles. In such examples, the filler material may represent between 5 percent to 50 percent by weight of the abrasive material. Such examples may be particularly useful for abrasive materials used for edge grinding coverglass.

[0181] In various examples, abrasive materials as described herein may be used to form an abrasive surface of an abrasive rotary tool particularly suitable for edge grinding coverglass. In some examples, the abrasive material, including resin, abrasive composite particles, and any additional additives dispersed in the resin, may be molded to form the abrasive surface or even an entire rotary tool 328. For example, the abrasive material may be overmolded on a core of a rotary tool 328 to form the abrasive surface. In general, such a core would include the tool shank as well as a portion embedded in the abrasive material in order to mechanically secure the abrasive material to the tool shank.

[0182] In other examples, the abrasive material may be a coating on a substrate. In different examples, the substrate may represent a core of a rotary tool 328 providing the shape of the rotary tool, with the abrasive applied directly to the core of the rotary tool. In other examples, the substrate may represent a sheet material later applied to a core of a rotary tool. In such examples, the substrate may be a flat substrate or a curved substrate. In various examples, the substrate may include one or more of a polymer fdm, a non-woven substrate, a woven substrate, a rubber substrate, an elastic substrate, a foam substrate, a conformable material, an extruded fdm, a primed substrate, and an unprimed substrate.

[0183] In some particular examples, an abrasive material coating may be formed from an abrasive composite layer deposited polymeric fdm with a primer layer between the abrasive composite layer and the polymeric fdm. The polymeric fdm itself may be positioned over a compliant layer, such as a foam, with an adhesive securing the polymeric fdm to the complaint layer. The combined abrasive material coating, polymeric material and complaint material may then be applied to core of rotary tool 328 in order to form the shape of abrasive surface 329 on rotary tool 328. In some examples, the abrasive material may be further cured after being applied to the core of the rotary tool 328.

[0184] FIGS. 5B and 5D-5H illustrate example rotary abrasive tools suitable for grinding of a glass, such as a coverglass, sapphire, ceramics, and the like, whereas FIG. 5C illustrates acoverglass for an electronic device. Each of the tools of FIGS. 5B and 5D-5F may include an abrasive material as described herein, and may be utilized as rotary tool 328 within system 310.

[0185] In particular, FIG. 5B illustrates an example rotary abrasive tool 300. Rotary abrasive tool 300 includes a set of flexible flaps 304 with abrasive external surface 306, 308 that facilitate abrading an edge of a workpiece across multiple angles through bending of the flexible flaps. Rotary abrasive tool 300 further includes tool shank 302, which defines an axis of rotation for tool 300. Flexible flaps 304 may secured to tool shank 302 with an optional fixation mechanism 305, which may represent a pin, screw, rivet or other fixation mechanism. Tool shank 302 may be configured to mount within a chuck of a rotary machine, such as a drill or CNC machine.

[0186] Flexible flaps 304 form a flexible planar section positioned opposite tool shank 302. Each of flexible flaps 304 form a first abrasive external surface 306 on a first side of the flexible flaps 304, the first side of flexible flaps 304 facing generally away from tool shank 302. Each of flexible flaps 304 also form an optional second abrasive external surface 308 on a second side of flexible flaps 304, the second side of flexible flaps 304 facing in the general direction of tool shank 302. Optional substrate 310 is located between first abrasive external surface 306 and second abrasive external surface 308. In some examples, substrate 310 may include an elastically compressible layer backing abrasive external surfaces 306, 308.

[0187] Rotary abrasive tool 300 further includes cylindrical section 314 attached to tool shank 302. Cylindrical section 314 forms third abrasive external surface 316 surrounding the axis of rotation 103. Cylindrical section 314 may further include an optional elastically compressible layer backing abrasive external surface 316. Flexible flaps 304 extend past the outer diameter of cylindrical section 314 relative to axis of rotation 303.

[0188] One or more of abrasive external surfaces 306, 308 and 316 may include an abrasive coating as previously described herein. In the same or different examples, one or more of abrasive external surfaces 306, 308 and 316 may include an abrasive film as also previously described herein. Such abrasives may be secured to a substrate of tool 300, such as substrate 310, with an epoxy.

[0189] In different examples, as described herein, the abrasive of one or more of abrasive external surfaces 306, 308 and 316 may provide an abrasive grain size of less than 20 micrometers, such as an abrasive grain size of between about 10 micrometers and about 1 micrometer, such as an abrasive grain size of about 3 micrometers. Such examples may be particularly useful for edge grinding of a coverglass.

[0190] In some examples, third abrasive external surface 316 of cylindrical section 314 may include portions with different abrasive grain sizes from one another. In such examples, thedifferent portions may be utilized in series to provide improved surface finish or speed for surface finishing during a grinding operation, such as edge grinding of a coverglass.

[0191] As described in further detail with respect to FIGS. 5D-5F, cylindrical section 314 facilitates abrading an edge of the workpiece between the first side of the workpiece and the second side of the workpiece while operating of tool 300 from tool shank 302. In addition, flexible flaps 304 facilitate abrading, with first abrasive external surface 306, a first comer adjacent to a first side of a workpiece across multiple angles relative to the axis of rotation for the rotary tool through bending of flexible flaps 304 when first abrasive external surface 306 is applied to the first comer of the workpiece. Similarly, flexible flaps 304 facilitates abrading, with second abrasive external surface 308, a second comer adjacent to a second side of the workpiece, the second side of the workpiece opposing the first side of the workpiece, across multiple angles relative to the axis of rotation for the rotary tool through bending of flexible flaps 304 when second abrasive external surface 308 is applied to the second comer of the workpiece.

[0192] FIG. 5C illustrates coverglass 350, which is a coverglass for an electronic device, a cellular phone, personal music player or other electronic device. In some examples, coverglass 350 may be a component of a touchscreen for the electronic device. Coverglass 350 may be an alumina-silicate based glass with a thickness of less than 1 millimeter, although other compositions are also possible.

[0193] Coverglass 350 includes a first major surface 362 opposing a second major surface 364. Generally, but not always, major surfaces 362, 364 are planar surfaces. Edge surface 366 follows the perimeter of major surfaces 362, 364, the perimeter including rounded comers 367. Coverglass 350 further forms a hole 352. Hole 352 includes its own edge surfaces.

[0194] To provide an increased resistance to cracking and improved appearance, the surfaces of coverglass 350, including major surfaces 362, 364, edge surface 366 and the edge surfaces of hole 352, should be smoothed to the extent practical during manufacturing of coverglass 350. After machining to form the general shape of coverglass 350, the surfaces may be polished, e.g., using a CeO-based coolant, to remove grinding and machining marks in coverglass 350.

[0195] In addition, as disclosed herein, rotary abrasive tools, such as those described with respect to FIGS. 5A-5B and 5D-5H may be used to reduce edge surface roughness, such as edge surface 366 and the edge surfaces of hole 352, using a CNC machine prior to polishing. The intermediate grinding step may reduce polishing time to provide desired surface finish qualities of coverglass 350 may not only reduce production time, but may also provide more precise dimensional control for the production of coverglass 350.

[0196] FIGS. 5D-5H illustrate rotary abrasive tool 100 being used to abrade coverglass 350, which may represent a partially -finished coverglass in that it has not yet be polished or hardened following machining to form its general shape. Rotary abrasive tool 300 may first be secured to a rotary tool holder of a CNC machine, such as rotary machine 323.

[0197] As illustrated in FIG. 5D, surface 306 of the flexible section of tool 300, flexible flaps 304, are being used to abrade the comers between edge 353 of hole 352 and major surface 362. The flexibility of flexible flaps 304 allows surface 306 to conform to the contours of the comers between edge 353 of hole 352 and major surface 362 as rotary abrasive tool 300 is pushed through hole 352, e.g., by a CNC machine according to a preprogrammed set of instmctions. In different examples, these comers may be rounded, beveled or square prior to the abrading by tool 300. Likewise, the flexibility of flexible flaps 304 allows surface 306 to conform to the contours of other comers, including the comers of between edge 366 and major surface 362 to facilitate abrading these comers with surface 306. In different examples, the comers of between edge 366 and major surface 362 may be rounded, beveled or square prior to the abrading by tool 300.

[0198] Flexible flaps 304 are also flexible enough to push entirely through hole 352, in order to allow abrasive external surface 316 of cylindrical section 314 to abrade edge 353 of hole 352, as shown in FIG. 5E. In addition, the flexibility of flexible flaps 104 allows surface 308 to conform to the contours of the comers between edge 353 of hole 352 and major surface 364 as rotary abrasive tool 300 is pulled back through hole 352, e.g., by the CNC machine. In different examples, these comers may be rounded, beveled or square prior to the abrading by tool 300. Likewise, the flexibility of flexible flaps 304 allows surface 306 to conform to the contours of other comers, including the comers of between edge 366 and major surface 364 to facilitate abrading these comers with surface 308.

[0199] In this manner, tool 300 allows abrading all the surfaces associated with hole 352, including edge 353 and the comers between edge 353 and major surfaces 362, 364. Such abrading may occur by continuously rotating tool 300 while contacting the surfaces associated with hole 352 with abrasive surfaces 306, 316 and 308. Tool 300 also allows abrading all the surfaces associated with edge 166 including the comers between edge 366 and major surfaces 362, 364. Such abrading may occur by continuously rotating tool 300 while contacting the surfaces associated with edge 366 with abrasive surfaces 306, 316 and 308. Following the abrading of surfaces associated edges 353, 366 using tool 300, these surfaces may be polished using an abrasive slurry or coolant, such as a CeO-based coolant, to further improve the surface finish. In the same or different examples in which an abrasive coolant is used, tool 300 may bepart of a set of two or more tools 100 that provide different levels of abrasion. For example, the tools may be used in series from a higher level of abrasiveness to lower levels of abrasiveness to refine the surface finish.

[0200] FIG. 5G illustrates rotary abrasive tool 370. Rotary abrasive tool 370 is substantially similar to rotary abrasive tool 400, except that rotary abrasive tool 370 does not include flexible flaps 304.

[0201] Rotary abrasive tool 370 includes tool shank 372, which defines an axis of rotation for tool 370. Tool shank 372 may be configured to mount within a chuck of a rotary machine, such as a drill or CNC machine. Rotary abrasive tool 370 further includes cylindrical section 374 in coaxial alignment with, and attached to, tool shank 372. Cylindrical section 374 forms an abrasive external surface 376 with circular cross sections perpendicular to the axis of rotation of tool 370. In some examples, two or more abrasive grain sizes may be included in different portions of abrasive external surface 376. Abrasive external surface 376 may include an abrasive coating as previously described herein. In the same or different examples, abrasive external surface 376 may include an abrasive film as also previously described herein.

[0202] Following the abrading of surfaces of a workpiece using tool 370, these surfaces may be polished using an abrasive slurry coolant, such as a CeO-based coolant, to further improve the surface finish. In in the same or different examples in which an abrasive slurry or coolant is used, tool 370 may be part of a set of two or more tools 370 that provide different levels of abrasion. For example, the tools may be used in series from a higher level of abrasiveness to lower levels of abrasiveness to refine the surface finish.

[0203] FIG. 5H illustrates a rotary tool 380 that includes an abrasive external surface 376 that has been wrapped around an edge of cylindrical section, such that a portion 386 is on an end of the shank, while a portion 382 is along a side surface of the shank. This results in precisely shaped abrasive composites having different directionality along the surface to tool 380.

[0204] FIGS. 6A-6D illustrate a rotary tool in accordance with embodiments herein. Rotary tool 400 may be similar to rotary tools 300 and 370. FIG. 6A illustrates a side view of a rotary tool having an abrasive layer. FIG. 6B illustrates an exploded view 410 of rotary tool 400. An abrasive layer 406 is adhered or otherwise coupled to a compliant layer 404, which in turn is coupled to a shaft 402. Shaft 402 may be formed of metal. Compliant layer 404 may be formed from any suitable compliant material and may have a suitable thickness for a given abrading operation. Abrasive layer 406 includes precisely-shaped abrasive composites arranged in a precise grid pattern across the surface of rotary tool 400, as described in embodiments herein.FIG. 6C illustrates a cutaway view of rotary tool 400, illustrating the compressibility of compliant layer 404.

[0205] FIG. 6D illustrates a schematic cutaway view 420 of rotary tool 400. Precisely- shaped abrasive composites 406, as illustrated in FIG. 6D, may be placed such that adjacent composites have at least some contact along an edge. However, it is expressly contemplated that at least some space may be present between adjacent precisely-shaped abrasive composites. As illustrated, in some embodiments, precisely-shaped abrasive composites are wedge-shaped, having a first triangular face (illustrated in FIG. 6D) opposite a second triangular face (not shown in FIG. 6D). A quadrilateral-shaped face may connect the opposing triangular faces and may interface with abrasive backing 422.

[0206] Precisely-shaped abrasive composites 406 are formed, as described herein, of a plurality of abrasive particles within a binder material. In some embodiments herein, the abrasive particles include diamond particles and the binder material includes an acrylate.

[0207] Precisely-shaped abrasive composites 406, in some embodiments herein, are formed as a unitary structure with abrasive layer 422. However, it is expressly contemplated that, in some embodiments, abrasive layer 422 may have a different composition. For example, abrasive layer 422 may be formed of a binder material without abrasive particles for cost savings purposes.

[0208] Abrasive layer 422, in some embodiments, is coupled to a polymeric fdm backing. Abrasive layer 422 may be coupled to a compliant layer 426 using an adhesive 424. Compliant layer 420 may be formed of any suitably resilient compressive material. For example, in some embodiments a rubber or foam material is used. Compliant layer 426 may be at least 1 mm thick, in some embodiments, or at least 2 mm thick, or at least 3 mm thick. In some embodiments, compliant layer 426 is less than 10 mm thick, or less than 8 mm thick, or less than 6 mm thick, or less than 5 mm thick, or even less than 4 mm thick.

[0209] Tool 400 may have a metal body 428 may of any suitable metal.

[0210] FIGS. 7A-7D illustrate shapes of composite abrasive structures described in greater detail in the Examples.

[0211] FIGS. 8A-8F illustrate different conformable abrasive fdm patterns which may be used with rotary tools in accordance with embodiments herein.

[0212] In some embodiments herein, the structured abrasive article is a conformable abrasive fdm having a structured abrasive layer coupled to a compliant layer, with or without an adhesive, for example. In the embodiments described in FIGS. 8A-8F, the structured abrasive article is converted into a shape that can be applied to a tool. For 3D contour shape polishingapplications, the structured abrasive article is converted into a shape that can be wrapped around an edge of a tool body.

[0213] Manufacturers of glass-containing devices, such as cell phone manufacturers, are increasingly upgrading glass material to include ceramic glass that, in turn, increases the need for abrasive articles having higher cut and longer useful life. The material may have at least some amorphous and at least some crystalline phases. Embodiments herein may be particularly useful for abrading ceramic glass, e.g. available under trade name NEOCERAM™ or Robax™, for example. Ceramic glass can withstand higher temperatures and is shatter resistant.

[0214] FIGS. 8A-8C illustrate a petal-shaped pattern for a conformable abrasive film pattern. The petal-shaped pattern is then wrapped around a cylindrical tool such that the edges of each petals contact, or approach contact with adjacent petals, along the cylindrical body of the tool, instead of over the circular face of the tool.

[0215] FIG. 8 A illustrates a schematic 500 of a petal pattern 502 that includes a number of petals 504 arranged about a center hole 506. As illustrated in FIG. 8B, the petal pattern is applied to a cylindrical rotary tool such that center hole 506 aligns with a shaft receiving portion of the tool body. The petal pattern 502 can be understood, simply, as a ring-shaped portion 516, which contacts the circular face of the rotary tool 512, and a plurality of petal portions 518 which wrap around a comer 512 of the rotary tool body such that part of each petal portion 518 contacts the curved lateral surface. In the illustrated embodiment, a majority of the surface area of each petal portion 518 contacts the curved lateral surface. In the illustrated embodiment, the entirety of the ring portion 516 contacts the circular surface.

[0216] As illustrated in FIG. 8C, adjacent petals do not have complete contact along the edges, leaving gaps 522. As seen in the image of FIG. 8C, the gaps may be fdled with an adhesive to increase adhesion.

[0217] In some embodiments, tools described herein are used with a coolant which can also affect the function of the tool. For example, tools of the design illustrated in FIGS. 8A-8C, when used with a cerium oxide coolant, saw delamination of the comformable abrasive film from the tool body, often due to the petals coming loose from the tool body, as the coolant can cause deterioration of the adhesive 524.

[0218] A new pattern is needed that can provided the needed abrading ability for a suitable useful life. FIG. 8D illustrates one example embodiment of a pattern 600 having a rectangularshaped base portion 612 and a number of triangular-shaped portions 614 extending therefrom. However, while triangular-shaped portions 614 are illustrated in FIG. 8D, it is expressly contemplated that other shapes may be possible, such as truncated triangles (e.g. trapezoids). Asillustrated in FIG. 8D, pattern 600 includes slits extending from a triangle width 610 into base 608, such that portions 614 could also be described as pentagonal. Additionally, rounded polygonal shapes may also be suitable in some embodiments. Other shapes may also be suitable. FIG. 8D illustrates an embodiment where triangles 614 are isosceles triangles having a height 608 greater than a width 610. In some embodiments, height 608 is at least 1.5x the width 610, or evel at least 2x the width 610, or at least 2.5x the width 610.

[0219] Base portion 612 may have a height 606 that is less than triangular portion height 608. In some embodiments, triangular portion height 608 is at least 1.5x the height 606, or at least 2x the height 606, or even at least 2.5x times the height 606, or even at least 3x the height 606, or even greater.

[0220] Pattern 600 may be defined by a rectangular shape formed of a length 602 of base portion 612 and a height 604, which may represent height 606 combined with height 608, for example.

[0221] FIG. 8E illustrates a rotary abrasive tool where a conformable abrasive film 622 having pattern 600 has been coupled to a rotary tool 620. Film 622 has been wrapped around an edge 624 joining the curved lateral surface of the cylindrical tool body to the circular face. The triangular portions of film 622 are also wrapped around an edge 626, such that they extend into a centerhole of the rotary abrasive tool body.

[0222] Triangular portions 622 may, in some embodiments, span the edge 624, such that a first portion of each triangular portion 622 covers the curved lateral surface of tool 620 and a second portion covers the circular face.

[0223] In some embodiments, rectangular body portion 612 is coupled to the curved lateral surface of tool 620, and does not span edge 624.

[0224] FIG. 8F illustrates a method 630 of manufacturing a rotary tool for 3D abrasive operations in accordance with embodiments herein. As illustrated in FIG. 8F, the compliant abrasive film is wrapped around the tool body such that body portion 612 is coupled to the curved lateral surface of the cylindrical tool and triangular portions 614 are folded such that the circular face of the tool is covered. In some embodiments, where a rotary tool body has a center hole extending therethrough to receive a shaft, the triangular portions 614 may further be folded into the center hole. This may increase the durability of the compliant abrasive film, and reduce delamination of the triangular portions from the tool body.

[0225] The compliant abrasive film pattern illustrated in FIGS. 8D-8F may provide improved useful life compared to the pattern of FIGS. 8A-8C. Tools made according to the construction illustrated in FIGS. 8A-8C, for example, saw useful lives in the range of about 40 toabout 60 parts. Tools made according to the construction illustrated in FIGS. 8D-8F, in some embodiments, can have a useful life in excess of 60 parts, or even in excess of 70 parts, or even in excess of 80 parts.

[0226] Additionally, because the pattern of FIG. 8D can be cut from a rectangular shape, as opposed to the petal pattern of FIG. 8A, which has a circular footprint, there will be less waste involved in the manufacturing of compliant abrasive fdms for rotary abrasive fdms for 3D abrasive operations.

[0227] FIG. 9 illustrates a method of forming a rotary abrasive tool for a 3D abrasive operation in accordance with embodiments herein. Method 900 may be useful for forming a rotary tool such as that illustrated in FIGS. 8A-8F, for example, or another suitable rotary abrasive tool. Tools made according to method 900 may be particularly suitable for 3D abrasive applications - e.g. operations where abrading is done across multiple surfaces (e.g. two edges simultaneously), or on a surface having 3D geometry (e.g. a curve).

[0228] At block 910, a composite abrasive structure is formed. In embodiments herein, a composite abrasive structure comprises a plurality of shaped abrasive composites arranged in a repeating pattern. The shaped abrasive composites may have a shape such as one of those described with respect to FIGS. 3A-3H, in some embodiments herein. However, other shapes may also be suitable. The shaped abrasive composites may be arranged in a pattern such as those described with respect to FIGS. 4A-4E, in some embodiments herein. However, other arrangements may also be suitable. The composite abrasive structure may be formed on, or coupled to, a fdm backing.

[0229] At block 920, a conformable layer is applied to a tool. In some embodiments herein, the conformable layer includes a thick layer of rubber that is applied to the tool body prior to being coupled to the composite abrasive structure. The compliant backing may include at least one compliant layer, for example a foam, a rubber, or another material that both deforms under pressure but is also resilient and at least partially recovers from deformation when the applied pressure is removed.

[0230] In embodiments where the conformable layer includes a foam, the foam may be any suitable open or closed cell foam as described herein. The foam is a polymeric foam, in some embodiments herein.

[0231] At block 930, the composite abrasive structure is cut into a desired pattern. Forming the pattern may include cutting, stamping or otherwise creating a pattern for the conformable abrasive fdm that allows for the 2D fdm to wrap around a 3D structure. Broadly speaking, the pattern includes a base portion and a number of protrusions. The base portion of the pattern isconfigured to couple along at least a majority of its surface to a first tool body surface. The protrusions are configured to couple to a second tool body surface. The protrusions may also be configured, in some embodiments, to wrap around at least one edge of the tool body surface. In some embodiments, the protrusions are configured to wrap around at least two edges of the tool body surface.

[0232] The protrusions may generally be described as having a first width, where they meet the base portion, and a second width, at an opposing end from the base portion coupling end.The second width may be substantially zero, e.g. such that the protrusions are triangular in shape and taper to a point. However, it is expressly contemplated that other shapes may be used. The second width should be less than the first width. In some embodiments the protrusions are shaped such that, as they wrap around a first and / or second edge of the rotary tool body, adjacent protrusions meet along adjacent protrusion edges to form a continuous surface.

[0233] At block 940, the conformable abrasive film is coupled to a tool body. The conformable abrasive film is coupled along at least two surfaces of the tool body, in some embodiments herein. For example, the conformable abrasive film may at least partially cover a curved lateral surface and at least partially cover a circular face of a cylindrical tool body. In some embodiments, the conformable abrasive film is configured to cover both a first edge where the curved lateral surface and the circular face meet, and a second edge, e.g. such that the conformable abrasive film wraps into a shaft or center hole of a cylindrical tool body.

[0234] FIG. 10 illustrates a method of abrading a worksurface using a 3D rotary abrasive tool in accordance with embodiments herein. Method 1000 may be useful for abrading a hard glass surface using a coolant.

[0235] At block 1010, a coolant is applied to a worksurface. Embodiments herein may be particularly useful for abrading hard glass surfaces in conjunction with a cerium oxide-based coolant. However, it is expressly contemplated that embodiments herein may be useful for other applications and / or in combination with other coolant compositions.

[0236] At block 1020, the worksurface is contacted with a rotary tool. In some embodiments herein the rotary tool includes a cylindrical tool body having a curved lateral surface coupled to a circular face on an edge. The circular face may have an aperture or shaftreceiving feature in the circular face. The rotary tool includes a conformable abrasive film attached to the cylindrical body. The conformable abrasive film is wrapped around the edge such that a first portion contacts the curved lateral surface and a second portion contacts the circular face. In some embodiments herein, the conformable abrasive film wraps around a second edge formed by the circular face and the aperture.

[0237] The conformable abrasive film includes a composite abrasive structure in embodiments herein that is formed of a number of shaped abrasive composites in a repeating pattern. The shaped abrasive composites may be shaped such as those illustrated in FIGS. SASH, in some embodiments. Other suitable shapes may also be possible in some embodiments. The shaped abrasive composites may be arranged in patterns like those illustrated in FIGS. 4A- 4E in some embodiments.

[0238] At block 1030, the rotary tool is moved with respect to the worksurface. In some embodiments, the rotary tool maintains a fixed position and the worksurface is moved. In some embodiments, the worksurface maintains a fixed position and the rotary tool is moved. In some embodiments both the rotary tool and the worksurface move during an abrasive operation. The rotary tool may move in a linear fashion along the worksurface in addition to be rotated, in some embodiments herein. The rotary tool may move in an orbital or random orbital pattern, in some embodiments herein. The rotary tool may also be moved against the worksurface in other patterns in accordance with embodiments herein.

[0239] In typical usage of structured abrasive articles according to the present disclosure, the abrasive layer is brought into frictional contact with a surface of a workpiece and then at least one of the structured abrasive article or the workpiece is moved relative to the other to abrade at least a portion of the workpiece.

[0240] The structured abrasive article may be moved relative to the workpiece by hand or by mechanical means such as, for example, an electric or air-driven motor using any method known in the abrasive art. The structured abrasive article may be removably fastened to a backup pad (for example, as is common practice with discs) or may be used without a backup pad (for example, in the case of abrasive belts).

[0241] An abrasive rotary tool is presented that includes a cylindrical tool body with a curved lateral surface and a circular face. A conformable abrasive film is wrapped around an edge joining the curved lateral surface to the circular face. The conformable abrasive film includes a base portion coupled to the curved lateral surface and a plurality of protrusions extending from the base portion. Each protrusion has a first width at the base portion and a second width at an opposing end, with the second width being less than the first width. A structured abrasive layer is disposed on the conformable abrasive film, comprising a plurality of precisely-shaped abrasive composites arranged in a repeating pattern. Each precisely-shaped abrasive composite includes a first substantially triangular-shaped face opposite a second substantially triangular-shaped face, a quadrilateral-shaped surface coupled to both the first and second substantially triangular-shaped faces, a cutting edge formed along one side of thequadrilateral-shaped surface, and a contacting edge formed along an opposite side, with the contacting edge being longer than the cutting edge. The precisely-shaped abrasive composites may include ceramic abrasive particles in a binder material.

[0242] The rotary abrasive tool may include an aperture in the circular face, with the aperture having a second edge. The protrusions may be configured to wrap around the second edge and extend into the center aperture.

[0243] The protrusions may have a first width at a base end and a second width at a second end opposite the base end, with the second width being less than the first width.

[0244] The second width of the protrusions may be substantially zero.

[0245] The protrusions may be configured such that, when wrapped around the second edge, adjacent protrusions contact each other along a protrusion edge.

[0246] The rotary abrasive tool may further include an adhesive layer coupling the conformable abrasive film to the cylindrical tool body.

[0247] The protrusions may have a protrusion height greater than a protrusion width.

[0248] The protrusions may have a height that is at least twice the protrusion width.

[0249] The base portion and the plurality of protrusions may form a pattern bounded by a hypothetical rectangle.

[0250] A protrusion height may be greater than a base portion height.

[0251] The base portion may be substantially rectangular in shape.

[0252] A protrusion height may be at least twice the base portion height.

[0253] The structured abrasive layer may include diamond abrasive particles.

[0254] The precisely-shaped abrasive composites may be arranged in a grid pattern on the conformable abrasive film.

[0255] Adjacent precisely-shaped abrasive composites may have different orientations.

[0256] Adjacent precisely-shaped abrasive composites may have the same orientation.

[0257] The conformable abrasive film may include a compliant backing layer.

[0258] The binder may include resin.

[0259] The precisely-shaped abrasive composites may be precisely placed such that a spacing between a first precisely-shaped abrasive composite and an adjacent second precisely- shaped abrasive composite is substantially the same as a spacing between the second precisely- shaped abrasive composite and an adjacent third precisely-shaped abrasive composite.

[0260] The spacing may be substantially zero, such that the first precisely-shaped abrasive particle contacts the second precisely-shaped abrasive particle along at least a portion of an edge.

[0261] The first substantially-triangular shaped face may include an obtuse triangle.

[0262] The first substantially-triangular shaped face may include an acute triangle.

[0263] The abrasive particles may have a Mohs hardness of at least 8.

[0264] The precisely-shaped abrasive composite may have an aspect ratio of length to thickness of less than 3.

[0265] The cutting edge may have an uneven cutting profile.

[0266] The uneven cutting profile may include a plurality of peaks and valleys.

[0267] A method of abrading a worksurface using a rotary abrasive tool is presented that includes applying a coolant to the worksurface and frictionally contacting the worksurface with a rotary tool. The rotary tool includes a cylindrical tool body with a curved lateral surface and a circular face, the circular face having a center aperture. A conformable abrasive film is wrapped around an edge joining the curved lateral surface to the circular face. The conformable abrasive film includes a base portion coupled to the curved lateral surface and a plurality of protrusions extending from the base portion, each protrusion having a first width at the base portion and a second width at an opposing end, with the second width being less than the first width. The protrusions are configured to wrap around the edge and into the center aperture. A structured abrasive layer is disposed on the conformable abrasive film, comprising a plurality of precisely- shaped abrasive composites arranged in a repeating pattern. The method includes moving the rotary tool relative to the worksurface to abrade at least a portion of the worksurface.

[0268] The compliant backing of the conformable abrasive film may include a polymeric foam layer.

[0269] The adhesive layer used to secure the conformable abrasive film to the tool body may be a pressure-sensitive adhesive.

[0270] The shaped abrasive composites in the composite abrasive structure may include diamond abrasive particles in a resin binder.

[0271] The coolant applied to the worksurface may be a cerium oxide-based coolant.

[0272] The rotary tool may be moved in an orbital pattern relative to the worksurface during the abrasive operation.

[0273] Each shaped abrasive composite may have a trapezoidal-shaped face coupled to the first and second substantially triangular-shaped faces.

[0274] The quadrilateral-shaped surface of each shaped abrasive composite may be a rectangle.

[0275] The first substantially triangular-shaped face of each shaped abrasive composite may be an isosceles triangle.

[0276] The first substantially triangular-shaped face of each shaped abrasive composite may be an acute triangle.

[0277] The cutting edge of each shaped abrasive composite may be configured to contact a work surface at a rake angle between 80° and 100°.

[0278] A method of forming a rotary abrasive tool for a 3D abrasive operation is presented that includes providing a composite abrasive structure comprising a plurality of precisely-shaped abrasive composites. Each composite has a first substantially triangular-shaped face opposite a second substantially triangular-shaped face and a quadrilateral-shaped surface coupled to both the first and second substantially triangular-shaped faces. The method includes applying the composite abrasive structure to a compliant backing to form a conformable abrasive film, shaping the conformable abrasive film into a pattern comprising a base portion and a plurality of protrusions extending from the base portion, each protrusion having a first width at the base portion and a second width at an opposing end, with the second width being less than the first width. The method includes coupling the conformable abrasive film to a cylindrical tool body such that the base portion is coupled to a curved lateral surface of the tool body, the protrusions wrap around an edge joining the curved lateral surface to a circular face of the tool body, and extend into a center aperture of the tool body. The method includes securing the conformable abrasive film to the tool body using an adhesive layer. The structured abrasive layer may include abrasive particles in a binder material.

[0279] The composite abrasive structure may include a plurality of precisely-shaped abrasive composites, each composite having a first substantially triangular-shaped face opposite a second substantially triangular-shaped face and a quadrilateral-shaped surface coupled to both the first and second substantially triangular-shaped faces.

[0280] The quadrilateral-shaped surface of each precisely-shaped abrasive composite may be a rectangle.

[0281] The first substantially triangular-shaped face of each precisely-shaped abrasive composite may be an isosceles triangle.

[0282] The first substantially triangular-shaped face of each precisely-shaped abrasive composite may be an acute triangle.

[0283] The structured abrasive layer may include abrasive particles in a binder material.

[0284] A structured abrasive article is presented that includes a substrate and a backing coupled to the substrate. The backing has first and second opposed major surfaces and may include a compliant material. A structured abrasive layer is disposed on and secured to the first major surface, comprising precisely-shaped abrasive composites. The precisely-shaped abrasivecomposites include a first substantially triangular-shaped face opposite a second substantially triangular-shaped face and a quadrilateral-shaped surface that is coupled to both the first and second substantially triangular-shaped faces and forms an angle with the backing. A cutting edge is formed along one side of the quadrilateral, and a contacting edge is formed along an opposite side of the quadrilateral. The contacting edge is configured to couple to the backing, and the contacting edge is longer than the cutting edge. The precisely-shaped abrasive composites may include abrasive particles in a binder material.

[0285] The precisely-shaped abrasive composites may be precisely placed such that a spacing between a first precisely-shaped abrasive composite and an adjacent second precisely- shaped abrasive composite is substantially the same as a spacing between the second precisely- shaped abrasive composite and an adjacent third precisely-shaped abrasive composite.

[0286] The spacing may be substantially zero, such that the first precisely-shaped abrasive particle contacts the second precisely-shaped abrasive particle along at least a portion of an edge.

[0287] The first substantially-triangular shaped face may include a right triangle.

[0288] The first substantially-triangular shaped face may include an obtuse triangle.

[0289] The first substantially-triangular shaped face may include an acute triangle.

[0290] The binder material may include a polymeric material.

[0291] The binder material may include a thermoset polymeric material.

[0292] The abrasive particles may include diamond.

[0293] The abrasive particles may include ceramic abrasive particles.

[0294] The abrasive particles may have a Mohs hardness of at least 8.

[0295] The precisely-shaped abrasive composite may have an aspect ratio of length to thickness of less than 3.

[0296] The precisely-shaped abrasive composite may have an aspect ratio of length to thickness of less than 2.

[0297] The structured abrasive article may further include a layer of pressure-sensitive adhesive disposed on the second major surface.

[0298] The cutting edge may have an uneven cutting profile.

[0299] The uneven cutting profile may include a plurality of peaks and valleys.

[0300] A method of abrading a glass workpiece is presented that includes frictionally contacting at least a portion of the structured abrasive layer of the structured abrasive article with a surface of the glass workpiece and moving at least one of the workpiece or the structured abrasive layer relative to the other to abrade at least a portion of the surface of the workpiece.

[0301] An abrasive rotary tool is presented that includes a tool shank defining an axis of rotation for the rotary tool and a cylindrical section attached to the tool shank. The cylindrical section includes an abrasive external surface surrounding the axis of rotation for the rotary tool. The cylindrical section facilitates abrading an edge of the workpiece between the first side of the workpiece and the second side of the workpiece while operating the abrasive rotary tool from the tool shank. The abrasive external surface includes a structured abrasive layer, which comprises a plurality of precisely-shaped abrasive composites. These precisely-shaped abrasive composites are precisely arranged in a pattern on the abrasive external surface. Each composite includes a first substantially-triangular shaped face opposite a second substantially-triangular shaped face, and a trapezoidal-shaped face coupled to the first substantially-triangular shaped face along a first edge and to the second substantially-triangular shaped face along a second edge. A third edge of each precisely-shaped abrasive composite is coupled to the backing and is opposite a fourth edge, with the fourth edge being configured to contact a workpiece.

[0302] The plurality of precisely-shaped abrasive composites may include a plurality of abrasive particles in a binder.

[0303] The plurality of abrasive particles may include diamond particles.

[0304] The first substantially-triangular shaped face may be a right triangle.

[0305] The first substantially-triangular shaped face may be an acute triangle.

[0306] The first substantially-triangular shaped face may be an obtuse triangle.

[0307] The fourth edge may be shorter than the third edge.

[0308] The fourth edge may be at least half the length of the third edge.

[0309] An aspect ratio of a thickness of the precisely-shaped abrasive composite to a length of the precisely-shaped abrasive composite may be less than 3.

[0310] An aspect ratio of a thickness of the precisely-shaped abrasive composite to a length of the precisely-shaped abrasive composite may be less than 2.

[0311] The abrasive rotary tool may further include a flexible planar section positioned opposite the tool shank. The flexible planar section forms a second abrasive external surface on a first side of the flexible planar section, with the first side facing generally away from the tool shank. The flexible planar section forms a third abrasive external surface on a second side of the flexible planar section, with the second side facing in the general direction of the tool shank. The flexible planar section facilitates abrading, with the second abrasive external surface, a first comer adjacent to a first side of a workpiece across multiple angles relative to the axis of rotation for the rotary tool through bending of the flexible planar section when the second abrasive external surface is applied to the first comer of the workpiece. The flexible planarsection also facilitates abrading, with the third abrasive external surface, a second comer adjacent to a second side of the workpiece, with the second side opposing the first side of the workpiece, across multiple angles relative to the axis of rotation for the rotary tool through bending of the flexible planar section when the second abrasive external surface is applied to the second comer of the workpiece. The flexible planar section extends past the outer diameter of the cylindrical section relative to the axis of rotation for the rotary tool.

[0312] The abrasive rotary tool may be configured to surface finish a heat-sensitive metal.

[0313] The abrasive rotary tool may be configured to surface finish a hard or brittle material.

[0314] The abrasive rotary tool may be configured to surface finish a material selected from a group consisting of glass, titanium alloy, sapphire, and ceramics.

[0315] The precisely-shaped abrasive composites may include diamond agglomerate particles.

[0316] A volume ratio of diamond agglomerates to a resin binder within the abrasive may be greater than 3 to 2.

[0317] The precisely-shaped abrasive composites may include a resin and a plurality of ceramic abrasive agglomerates dispersed in the resin. The ceramic abrasive agglomerates may include individual abrasive particles dispersed in a porous ceramic matrix, with at least a portion of the porous ceramic matrix comprising glassy ceramic material. Metal particles may be dispersed in the resin.

[0318] An assembly may include a CNC machine comprising a computer-controlled rotary tool holder and a workpiece platform. A workpiece representing a partially-finished cover glass for an electronic device may be secured to the workpiece platform, with the cover glass forming at least one hole. The assembly may include an abrasive rotary tool as described.

[0319] A method of abrading a surface of a hole in a partially-finished cover glass for an electronic device includes securing an abrasive rotary tool within a rotary tool holder of a CNC machine and operating the CNC machine to abrade the surface of the hole in the cover glass mounted to a workpiece platform of the CNC machine.

[0320] Objects and advantages of this disclosure are further illustrated by the following nonlimiting examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and, details, should not be construed to unduly limit this disclosure.EXAMPLESTEST METHOD AND PREPARATION PROCEDURES

[0321] Coverglass Abrasive Effectiveness Test Method

[0322] A partially finished coverglass following a scribing operation to form perimeter edges was provided. The partially finished coverglass was edge ground using a CNC machine to form the desired size and shape. Following the grinding step, the edges were ready for the abrasive test.

[0323] An abrasive tool assembly was prepared from a structured abrasive sample for evaluation. The tool size of FIG. 6A was standardized as a 32.5mm diameter tool 25mm high and, with a 25mm diameter machined aluminum core, shank and body, a 3mm thick foam rubber conformable layer, an adhesive bonding layer and the abrasive sample on the outside of the assembly. The thickness of the abrasive and adhesive were 0.75mm combined. The RPM, load and coolant flow was checked before the test.

[0324] The test machine held the abrasive tool assembly vertically in a spinning collet. The glass was held horizontally on a sliding bearing so the edge of the glass contacts the outer surface of the tool assembly. A constant load was applied between the glass edge and the tool assembly as the tool assembly spins. A count down timer is set to a predetermined time. The RPM of the rotating tool assembly is set before contact between the tool assembly.

[0325] The cutting fluid was prepared in a 5% solution of Sabrelube 9016 to water and added to the recirculating system for the test machine.Abrasive Effectiveness Test Method

[0326] The abrasive effectiveness test measured amount of coverglass removed from the coverglass edge at a set force, rpm and time. The controlled force eliminates any test variation from abrasive wear or glass part variation. The glass makes contact with the rotating abrasive at a target 3000 rpm. The test cycle was set at 2 minutes and multiple cycles are conducted in the same location on the abrasive. A new location on the glass edge was used for each 2-minute test. The surface roughness was measured at the end of the test in the location after the glass was removed.Cut Rate Test Method

[0327] The coverglass was weighed and then fixed to the moving stage. The tool assembly spun at the set rpm, cooling liquid was turned on, force control was applied to the moving stage,the timer was set and the glass was moved into contact with the tool assembly. After the cycle was completed, the rpm and coolant were turned off. The glass was removed, dried and reweighed. The amount of glass removed was recorded. The tool was positioned at a new location on the coverglass, and the next cycle was run. This sequence was repeated until the total number of cycles are achieved.Surface Finish Test Method

[0328] An interferometer is used to measure the surface finish. The finish produced by the above test method is measured at 20X magnification at the apex of the cut rate test position. Average Sa roughness and Peak-valley Sz values are recorded.Structured Abrasive Example Construction

[0329] The tool assemblies in the abrasive effectiveness test are all prepared identically except for the physical shape of the structured abrasive mounted on the exterior of the tool assembly. The structured abrasive composites of all Examples and Comparative Examples were formed of the same composition as that of commercially available abrasive composites available from 3M Company as product number 678XA-TD3V.

[0330] Example 1 was formed using a structured abrasive layer consisting of the shaped abrasive particle composite design as illustrated in FIG. 7A. The particle had approximate dimensions of length of 927 pm, a height of 635 pm, a cutting edge length of 678 pm, and a base edge length of 902 pm. The angle 210 is 90 degrees, perpendicular to the base film.

[0331] Comparative Example 1 was formed using a structured abrasive layer consisting of the shaped abrasive particle composites as illustrated in FIG. 7B, which are commercially available as product number 678XA-TD3V.

[0332] Comparative Example 2 was formed using a structured abrasive layer consisting of the shaped abrasive particle composites as illustrated in FIG. 7C, which are commercially available as product number 678XA-TD2A.

[0333] Comparative Example 3 was formed using a structured abrasive layer consisting of the shaped abrasive particle composites as described in US Pat. 8,425,278 issued on April 23, 2013.

[0334] Figure 11A is the cut values measured by weight loss of the glass piece at 2 minute intervals on the 3M test method. This show removal rate on the same location on the tool over 30 minutes at 2 minute intervals.

[0335] Figure 1 IB shows average roughness, Sa, is similar in all examples. Figure 11C shows peak to valley roughness, Sz, is similar in all examples. Typically higher cut rate produced rougher finish, but in this case the higher cut of example in Figure 7A result in similar finish to the other examples.

[0336] All patents and publications referred to herein are hereby incorporated by reference in their entirety. Various unforeseeable modifications and alterations of the present disclosure may be made by those skilled in the art without departing from the scope and spirit of the present disclosure, and it should be understood that the present disclosure is not to be unduly limited to the illustrative embodiments set forth herein.

Claims

1. What is claimed is:

1. An abrasive rotary tool comprising: a cylindrical tool body having a curved lateral surface and a circular face; a conformable abrasive film wrapped around an edge joining the curved lateral surface to the circular face, the conformable abrasive film comprising: a base portion coupled to the curved lateral surface; a plurality of protrusions extending from the base portion, each protrusion having a first width at the base portion and a second width at an opposing end, wherein the second width is less than the first width; a structured abrasive layer disposed on the conformable abrasive film, the structured abrasive layer comprising a plurality of precisely-shaped abrasive composites arranged in a repeating pattern, each precisely-shaped abrasive composite comprising: a first substantially triangular-shaped face opposite a second substantially triangular-shaped face; a quadrilateral-shaped surface coupled to both the first and second substantially triangular-shaped faces; a cutting edge formed along one side of the quadrilateral-shaped surface, and a contacting edge formed along an opposite side, the contacting edge being longer than the cutting edge; wherein the precisely-shaped abrasive composites comprise ceramic abrasive particles in a binder material.

2. The rotary abrasive tool of claim 1, wherein the edge is a first edge, wherein the rotary body also comprise an aperture in the circular face, the aperture having a second edge, and wherein the protrusions are configured to wrap around the second edge and extend into the center aperture.

3. The rotary abrasive tool of claim 1 or 2, wherein the protrusions have a first width, at a base end, and a second width, at a second end opposite the base end, and wherein the second width is less than the first width.

4. The rotary abrasive tool of claim 2, wherein the protrusions are configured such that, when wrapped around the second edge, adjacent protrusions contact each other along a protrusion edge.

5. The rotary abrasive tool of any of claims 1-4, and further comprising an adhesive layer coupling the conformable abrasive fdm to the cylindrical tool body.

6. The rotary abrasive tool of any of claims 1-5, wherein the protrusions have a protrusion height greater than a protrusion width.

7. The rotary abrasive tool of any of claims 1-6, wherein a protrusion height is greater than a base portion height.

8. The rotary abrasive tool of claim 7, wherein the base portion is substantially rectangular in shape.

9. The rotary abrasive tool of any of claims 1-2, wherein the structured abrasive layer comprises diamond abrasive particles.

10. The rotary abrasive tool of any of claims 1-3, wherein the precisely-shaped abrasive composites are arranged in a grid pattern on the conformable abrasive film.

11. The rotary abrasive tool of any of claims 1-10, wherein the conformable abrasive film includes a compliant backing layer.

12. The rotary abrasive tool of any of claims 1-11, wherein the precisely-shaped abrasive composites are precisely placed such that a spacing between a first precisely-shaped abrasive composite and an adjacent second precisely-shaped abrasive composite is substantially the same as a spacing between the second precisely-shaped abrasive composite and an adjacent third precisely-shaped abrasive composite.

13. The rotary abrasive tool of any of claims 1-12, wherein the first substantially-triangular shaped face comprises an obtuse triangle.

14. The abrasive rotary tool of any of claims 1-12, wherein the first substantially-triangular shaped face comprises an acute triangle.

15. The rotary abrasive tool of any of claims 1-14, wherein the precisely-shaped abrasive composite has an aspect ratio of length to thickness of less than 3.

16. The rotary abrasive tool of any of claims 1-15, wherein the cutting edge has an uneven cutting profile.

17. A method of abrading a worksurface using a rotary abrasive tool, the method comprising: applying a coolant to the worksurface; frictionally contacting the worksurface with a rotary tool comprising: a cylindrical tool body having a curved lateral surface and a circular face, the circular face having a center aperture; a conformable abrasive film wrapped around an edge joining the curved lateral surface to the circular face, the conformable abrasive film comprising: a base portion coupled to the curved lateral surface; a plurality of protrusions extending from the base portion, each protrusion having a first width at the base portion and a second width at an opposing end, wherein the second width is less than the first width; wherein the protrusions are configured to wrap around the edge and into the center aperture; a structured abrasive layer disposed on the conformable abrasive film, the structured abrasive layer comprising a plurality of precisely-shaped abrasive composites arranged in a repeating pattern; moving the rotary tool relative to the worksurface to abrade at least a portion of the worksurface.

18. The method of claim 17, wherein the compliant backing of the conformable abrasive film comprises a polymeric foam layer.

19. The method of claim 17 or 18, wherein the adhesive layer used to secure the conformable abrasive film to the tool body is a pressure-sensitive adhesive.

20. The method of any of claims 17-19, wherein the shaped abrasive composites in the composite abrasive structure comprise diamond abrasive particles in a resin binder.

21. The method of any of claims 17-20, wherein each shaped abrasive composite has a trapezoidal-shaped face coupled to the first and second substantially triangular-shaped faces.

22. The method of any of claims 17-21, wherein the cutting edge of each shaped abrasive composite is configured to contact a work surface at a rake angle between 80° and 100°.

23. A structured abrasive article comprising: a substrate; a backing coupled to the substrate, the backing having first and second opposed major surfaces, wherein the backing comprises a compliant material; and a structured abrasive layer disposed on and secured to the first major surface, the structured abrasive layer comprising precisely-shaped abrasive composites, wherein the precisely-shaped abrasive composites comprise: a first substantially triangular-shaped face opposite a second substantially triangular-shaped face; a quadrilateral-shaped surface that is coupled to both the first and second substantially triangular-shaped faces and forms an angle with the backing; and wherein a cutting edge is formed along one side of the quadrilateral, and a contacting edge is formed along an opposite side of the quadrilateral, the contacting edge being configured to couple to the backing, and wherein the contacting edge is longer than the cutting edge; and wherein the precisely-shaped abrasive composites comprise abrasive particles in a binder material.

24. The structured abrasive article of claim 23, wherein the precisely-shaped abrasive composites are precisely placed such that a spacing between a first precisely-shaped abrasive composite and an adjacent second precisely-shaped abrasive composite is substantially the same as a spacing between the second precisely-shaped abrasive composite and an adjacent third precisely-shaped abrasive composite.

25. The structured abrasive article of claim 24, wherein the spacing is substantially zero spacing such that the first precisely-shaped abrasive particle contacts the second precisely-shaped abrasive particle along at least a portion of an edge.

26. The structured abrasive article of any of claims 23-25, wherein the first substantially- triangular shaped face comprises a right triangle.

27. The structured abrasive article of any of claims 23-26, wherein the first substantially- triangular shaped face comprises an obtuse triangle.

28. The structured abrasive article of any of claims 23-27, wherein the first substantially- triangular shaped face comprises an acute triangle.

29. The structured abrasive article of any of claims 23-28, wherein the binder material comprises a polymeric material.

30. The structured abrasive article of claim 29, wherein the binder material comprises a thermoset polymeric material.

31. The structured abrasive article of any of claims 23-30, wherein the abrasive particles comprise diamond.

32. The structured abrasive article of any of claims 23-31, wherein the abrasive particles comprise ceramic abrasive particles.

33. The structured abrasive article of any of claims 23-32, wherein the abrasive particles have a Mohs hardness of at least 8.

34. The structured abrasive article of any of claims 23-33, wherein the precisely-shaped abrasive composite has an aspect ratio of length to thickness of less than 3.

35. The structured abrasive article of any of claims 23-34, wherein the precisely-shaped abrasive composite has an aspect ratio of length to thickness of less than 2.

36. The structured abrasive article of any of claims 23-35, and further comprising a layer of pressure-sensitive adhesive disposed on the second major surface.

37. The structured abrasive article of any of claims 23-36, wherein the cutting edge has an uneven cutting profile.

38. The structured abrasive article of any of claims 23-37, wherein the uneven cutting profile comprises a plurality of peaks and valleys.

39. A method of abrading a glass workpiece, the method comprising: frictionally contacting at least a portion of the structured abrasive layer of the structured abrasive article of any of claims 23-38 with a surface of the glass workpiece; and moving at least one of the workpiece or the structured abrasive layer relative to the other to abrade at least a portion of the surface of the workpiece.

40. An abrasive rotary tool comprising: a tool shank defining an axis of rotation for the rotary tool; a cylindrical section attached to the tool shank, wherein the cylindrical section comprises abrasive external surface surrounding the axis of rotation for the rotary tool; wherein the cylindrical section facilitates abrading an edge of the workpiece between the first side of the workpiece and the second side of the workpiece while operating of the abrasive rotary tool from the tool shank; and wherein the abrasive external surface comprises a structured abrasive layer, the structured abrasive layer comprising a plurality of precisely-shaped abrasive composites, the precisely-shaped abrasive composites being precisely arranged in a pattern on the abrasive external surface, and wherein the plurality of precisely-shaped abrasive composites each comprise a first substantially-triangular shaped face opposite a second substantially-triangular shaped face, and a trapezoidal-shaped face coupled to the first substantially-triangular shaped face, along a first edge, and the second substantially-triangular shaped face, along a second edge, wherein a third edge of each precisely-shaped abrasive composites is coupled to the backing and is opposite a fourth edge, the fourth edge being configured to contact a workpiece.

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