Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D11/00—Constructional features of flexible abrasive materials; Special features in the manufacture of such materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B19/00—Single-purpose machines or devices for particular grinding operations not covered by any other main group
  • B24B19/02—Single-purpose machines or devices for particular grinding operations not covered by any other main group for grinding grooves, e.g. on shafts, in casings, in tubes, homokinetic joint elements
  • B24B19/028—Single-purpose machines or devices for particular grinding operations not covered by any other main group for grinding grooves, e.g. on shafts, in casings, in tubes, homokinetic joint elements for microgrooves or oil spots
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B19/00—Single-purpose machines or devices for particular grinding operations not covered by any other main group
  • B24B19/22—Single-purpose machines or devices for particular grinding operations not covered by any other main group characterised by a special design with respect to properties of the material of non-metallic articles to be ground
  • B24B19/226—Single-purpose machines or devices for particular grinding operations not covered by any other main group characterised by a special design with respect to properties of the material of non-metallic articles to be ground of the ends of optical fibres
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D11/00—Constructional features of flexible abrasive materials; Special features in the manufacture of such materials
  • B24D11/001—Manufacture of flexible abrasive materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D3/00—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents
  • B24D3/02—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D3/00—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents
  • B24D3/02—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent
  • B24D3/20—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent and being essentially organic
  • B24D3/28—Resins or natural or synthetic macromolecular compounds

Definitions

• the present invention relates to an abrasive material having an abrasive layer of a three-dimensional structure, and more particularly to an abrasive material having an abrasive layer of a three-dimensional structure and being suited for abrading an end surface of an optical fiber on which a ferrule is mounted, i.e., an end surface of an optical fiber connector, into a predetermined shape.
• an optical fiber connector which can be easily removed is widely used for connection of optical fibers in an optical fiber communication network.
• end surfaces of the optical fiber ferrules made of an optical fiber and a covering portion (ferrule) for covering the optical fiber are allowed to directly abut each other. Therefore, the optical characteristics at the time of connection, particularly the connection loss, depend on the processing properties and precision of the end surfaces of the optical fibers.
• the end surface of the optical fiber ferrule is processed through a number of abrasion steps.
• the quality of the end surface is influenced by the processing properties and the precision in the final finishing abrasion step.
• the major factors for the connection loss of the optical fiber are the degree of finishing roughness of the end surface and its inclination.
• connection loss is about 0.5 dB if the particle size of the abrasive grains is about 1 ⁇ m, whereas the connection loss is more than about 1.0 dB if the particle size of the abrasive grains is about 15 ⁇ m.
• abrasive grains having a particle size of 10 to 15 ⁇ m must be used in order to satisfy a standard requiring the connection loss of the optical fiber to be less than 1 dB. and fine grade abrasive grains having a particle size of less than 1 ⁇ m must be used in order to satisfy a standard requiring the connection loss of the optical fiber to be less than 0.5 dB.
• Japanese Laid-open Patent Publication No. 09-248771/1997 discloses an abrasive tape for an end surface of an optical fiber connector in which the abrasive tape has a base material and an abrasive layer disposed on the base material, the abrasive layer is composed of silica particles having an average particle size of 5 to 30 ⁇ m and has a binder for connecting these abrasive material particles, and the central line average roughness Ra of the abrasive layer surface is 0.005 to 0.2 ⁇ m.
• Fine grade abrasive materials such as an abrasive tape for an end surface of an optical fiber connector have a problem of loading.
• loading means that the space among abrasive grains is filled with abrasion dusts that protrude to inhibit the abrasive property. For example, in the case where an end surface of an optical fiber connector is abraded, the particles of abrasion dusts stay in the space among the abrasive grains, whereby the cutting ability of the abrasive grains decreases.
• liquid that is used as a coolant and a lubricant does not act sufficiently between the abrasive material and the end surface of the optical fiber connector, whereby a part of the abrasive layer adheres to the surface of the optical fiber connector after abrasion and its removal is cumbersome.
• the period of time required for abrasion will be long.
• the particle size of the abrasive grains is increased, the finished end surface of the optical fiber connector will be rough, thereby failing to meet the standard for connection loss of the optical fiber. If both methods are used in combination, the number of abrading steps will increase.
• WO92/ 13680 and WO96/27189 disclose an abrasive material having an abrasive layer of a three-dimensional structure.
• This abrasive material has a base material and an abrasive layer disposed on the base material, the abrasive layer is made of an abrasive composite containing abrasive particles and a binder, and the abrasive layer has a three- dimensional structure constructed with a plurality of regularly arranged three-dimensional elements having a predetermined shape.
• the shape of the three-dimensional elements tetrahedral shape, pyramidal shape, and others are disclosed.
• This abrasive material is resistant to loading and excellent in durability.
• an abrasive material having such an abrasive layer of a three-dimensional structure is produced by applying an abrasive slurry containing abrasive particles and a binder in a mold sheet having a structure, superposing a base material on the mold sheet to bond the binder to the base material, hardening the binder by ultraviolet radiation, and removing the mold sheet.
• the abrasive slurry must have a sufficient fluidity to be introduced into the structure within the mold sheet.
• the ultraviolet radiation is performed after covering the abrasive slurry with the base material, the abrasive slurry must not contain a volatile component.
• the content of the abrasive grains in the abrasive slurry cannot exceed the critical pigment volume concentration. Accordingly, the conventional abrasive material having an abrasive layer of a three-dimensional structure has a problem that the content of abrasive grains in the abrasive layer cannot be sufficiently raised.
• the abrasive property of the abrasive material will decrease as the content of the abrasive grains is reduced.
• the abrasive efficiency will be poor to increase the period of time required for abrasion if the content of the abrasive grains is insufficient.
• the conventional abrasive material having an abrasive layer of a three-dimensional structure is poor in abrasive property and hence is not suited for abrading a hard material such as an end surface of an optical fiber connector efficiently and smoothly into a predetermined shape.
• the present invention has been made to solve the aforesaid problems of the prior art and an object thereof is to provide an abrasive material which is excellent in loading resistance and durability, allows no attachments to attach to an abraded surface even when the end surface of the optical fiber is abraded, and is particularly suited for use in abrading a hard material such as an end surface of an optical fiber connector effectively and smoothly into a predetermined shape.
• the present invention provides an abrasive material for abrading an end surface of an optical fiber connector into a predetermined shape, the abrasive material having a base material and an abrasive layer disposed on the base material, the abrasive layer having an abrasive composite containing abrasive grains and a binder as construction components, the abrasive layer having a three-dimensional structure constructed with a plurality of regularly arranged three-dimensional elements having a predetermined shape, thereby to achieve the aforesaid object of the present invention.
• the present invention provides a method for producing an abrasive material having an abrasive layer of a three-dimensional structure, the method comprising the steps of: (1) filling a mold sheet having a plurality of regularly arranged recesses, with an abrasive material coating solution containing abrasive grains, a binder, and a solvent, to a predetermined depth; (2) removing the solvent from the abrasive material coating solution in the recesses by evaporation; (3) filling the recesses further with a binder; (4) laminating a base material on the mold sheet to bond the binder to the base material; and (5) hardening the binder.
• the abrasive material having an abrasive layer of a three-dimensional structure is preferably produced by the aforesaid production method.
• Fig. 1 is a section view illustrating an abrasive material having an abrasive layer of a three-dimensional structure according to an embodiment of the present invention
• Fig. 2 is a top view illustrating an abrasive material having an abrasive layer of a three-dimensional structure according to an embodiment of the present invention
• Fig. 3 is a top view illustrating an abrasive material having an abrasive layer of a three-dimensional structure according to an embodiment of the present invention
• Fig. 4 is a perspective section view illustrating an abrasive material having an abrasive layer of a three-dimensional structure according to an embodiment of the present invention
• Fig. 5 is a top view illustrating an abrasive material having an abrasive layer of a three-dimensional structure according to an embodiment of the present invention
• Figs. 6(a) to 6(e) are model views illustrating steps for producing an abrasive material having an abrasive layer of a three-dimensional structure
• Fig. 7 is a graph showing change with time of an abraded amount when an end surface of an optical fiber connector is abraded with various abrasive materials
• Fig. 8 is a microscope photograph of an end surface of an optical fiber connector after being abraded with the abrasive material of the present invention
• Fig. 9 is a microscope photograph of an end surface of an optical fiber connector after being abraded with the abrasive material of the present invention.
• Fig. 10 is a microscope photograph of an end surface of an optical fiber connector after being abraded with the abrasive material of the prior art
• Fig. 11 is a microscope photograph of an end surface of an optical fiber connector after being abraded with the abrasive material of the prior art
• Fig. 12 is a microscope photograph of an end surface of an optical fiber connector after being abraded with the abrasive material of the prior art
• Fig. 13 is a microscope photograph of an end surface of an optical fiber connector after being abraded with the abrasive material of the present invention
• Fig. 14 is a microscope photograph of an end surface of an optical fiber connector after being abraded with the abrasive material of the present invention
• Fig. 15 is a microscope photograph of an end surface of an optical fiber connector after being abraded with the abrasive material of the prior art
• Fig. 16 is a graph showing change with time of an abraded amount when a circular rod of zirconia is abraded with various abrasive materials
• Fig. 17 is a microscope photograph of an end surface of an optical fiber connector after being abraded with the abrasive material of the present invention
• Fig. 18 is a microscope photograph of an end surface of an optical fiber connector after being abraded with the abrasive material of the present invention
• Fig. 19 is a microscope photograph of an end surface of an optical fiber connector after being abraded with the abrasive material of the present invention
• Fig. 20 is a microscope photograph of an end surface of an optical fiber connector after being abraded with the abrasive material of the present invention
• Fig. 21 is a microscope photograph of an end surface of an optical fiber connector after being abraded with the abrasive material of the prior art
• Fig. 22 is a microscope photograph of an end surface of an optical fiber connector after being abraded with the abrasive material of the prior art
• Fig. 23 is a microscope photograph of an end surface of an optical fiber connector after being abraded with the abrasive material of the present invention
• Fig. 24 is a microscope photograph of an end surface of an optical fiber connector after being abraded with the abrasive material of the present invention.
• Fig. 25 is a microscope photograph of an end surface of an optical fiber connector after being abraded with the abrasive material of the present invention.
• Fig. 1 is a section view illustrating an abrasive material having an abrasive layer of a three-dimensional structure as an embodiment of the present invention.
• An abrasive material 100 has a base material 101 and an abrasive layer 102 disposed on a surface of the base material 101.
• the base material for the present invention include polymer film, paper, cloth, metal film, vulcanized fiber, non-woven base material, a combination thereof, and a processed product thereof.
• the base material is preferably flexible, thereby facilitating formation of a spherical shape.
• the base material is preferably transparent with respect to ultraviolet radiation, since it is convenient in the production process.
• the base material may be, for example, a polymer film such as polyester film.
• the polymer film may be undercoated with a material such as polyethylene acrylic acid in order to promote bonding to the base material of the abrasive composite.
• the abrasive layer 102 has an abrasive composite containing a matrix of a binder and abrasive grains 103 dispersed therein as construction components.
• the abrasive composite is formed from a slurry containing a plurality of abrasive grains dispersed in the binder which is in an unhardened or ungelated state. In hardening or gelation, the abrasive composite is solidified, i.e. is fixed to have a predetermined shape and a predetermined structure.
• the dimension of the abrasive grains may vary depending on the type of the abrasive grains or the intended use of the abrasive material.
• the dimension is 0.01 to 1 ⁇ m, preferably 0.01 to 0.5 ⁇ m, more preferably 0.01 to 0.1 ⁇ m for the final finishing abrasion, and is 0.5 to 20 ⁇ m, preferably 0.5 to 10 ⁇ m for rough abrasion in forming a curved surface.
• abrasive grains for the present invention include diamond, cubic boron nitride, cerium oxide, fused aluminum oxide, heat-treated aluminum oxide, sol-gel aluminum oxide, silicon carbide, chromium oxide, silica, zirconia, alumina zirconia, iron oxide, garnet, and a mixture thereof.
• the binder is hardened or gelated to form an abrasive layer.
• the binder include phenolic resin, resol-phenolic resin, aminoplast resin, urethane resin, epoxy resin, acrylate resin, polyester resin, vinyl resin, melamine resin, acrylated isocyanurate resin, urea-formaldehyde resin, isocyanurate resin, acrylated urethane resin, acrylated epoxy resin, and a mixture thereof.
• the binder may be a thermoplastic resin.
• Especially preferable examples of the binder include phenolic resin resol-phenolic resin, epoxy resin, and urethane resin.
• the binder may be radiation-curing.
• the radiation-curing binder is a binder that is at least partially hardened or is at least partially polymerizable by radiation energy.
• an energy source such as heat, infrared radiation, electron beam radiation, ultraviolet radiation, or a visible light radiation is used.
• these binders are polymerized by a free radical mechanism.
• these binders are selected from the group consisting of acrylated urethane, acrylated epoxy, an aminoplast derivative having an , ⁇ unsaturated carbonyl group, an ethylenic unsaturated compound, an isocyanurate derivative having at least one acrylate group, isocyanate having at least one acrylate group, and a mixture thereof.
• a photoinitiator is required to start free radical polymerization.
• the photoinitiator to be used for this purpose include organic peroxides, azo compounds, quinones, benzophenones, nitroso compounds, acryl halides, hydrazones, mercapto compounds, pyrylium compounds, triacrylimidazole, bisimidazole. chloroalkyltriazine, benzoin ether, benzyl ketal, thioxanthone, and acetophenone derivatives.
• a preferable photoinitiator is 2.2-dimethoxy- 1 ,2-diphenyl- 1 -ethanone.
• the binder is hardened by visible light radiation, it is necessary that a photoinitiator stakrts a free radical polymerization.
• a photoinitiator for this purpose are disclosed in United States Patent No. 4,735,632, column 3, line 25 to column 4, line 10. column 5, lines 1 to 7, and column 6 lines 1 to 35, which are incorporated herein by reference.
• the weight proportion of the abrasive grains to the binder is typically within a range of about 1.5 to 10 parts of abrasive grains with respect to one part of the binder, preferably about 2 to 7 parts by weight of abrasive grains with respect to one part of the binder.
• the concentration of the abrasive grains contained in the abrasive composite is preferably within a range of 43 to 90 wt% if the abrasive grains are made of silicon carbide; 70 to 90 wt% if the abrasive grains are made of spherical abrasive particles of alumina, silica, or the like; 37 to 90 wt% if the abrasive grains are made of alumina; and 39 to 90 wt% if the abrasive grains are made of diamond.
• the abrasive composite may contain a material other than the abrasive grains and the binder.
• the abrasive material may contain ordinary additives such as a coupling agent, a lubricant, a dye, a pigment, a plasticizer, a filler, a stripping agent, an abrasive aid, and a mixture thereof.
• the abrasive composite can contain a coupling agent. Addition of the coupling agent can considerably reduce the covering viscosity of a slurry to be used for formation of the abrasive composite.
• the coupling agent for the present invention include organic silane, zircoaluminate, and titanate.
• the amount of the coupling agent is typically less than 5 wt%, preferably less than 1 wt%, of the binder.
• the abrasive layer 102 has a three-dimensional structure constructed with a plurality of regularly arranged three-dimensional elements 104 having a predetermined shape.
• the three-dimensional elements 104 each have a tetrahedral shape in which ridges are connected at a point on the top.
• the angle ⁇ formed between two ridges is typically 30 to 150°, preferably 45 to 140°.
• the three-dimensional elements 104 may have a pyramidal shape. In this case, the angle ⁇ formed between two ridges is typically 30 to 150°, preferably 45 to 140°.
• the points on the top of the three-dimensional elements 104 are located on a plane parallel to the surface of the base material substantially over an entire region of the abrasive material.
• the symbol h represents the height of the three-dimensional elements 104 from the surface of the base material.
• the height h is typically 2 to 300 ⁇ m, preferably 5 to 150 ⁇ m.
• the variation of the height of the points on the top is preferably less than 20%, more preferably less than 10%, of the height of the three-dimensional elements.
• the three-dimensional elements 104 are arranged in a predetermined configuration. In Fig. 1, the three-dimensional elements 104 are most closely packed. Typically the three-dimensional elements are repeated with a predetermined period. This repetitive shape is one-directional or preferably two-directional.
• the abrasive grains do not protrude beyond the surface of the shape of the three- dimensional elements.
• the three-dimensional elements 104 are constructed with flat planes.
• the surfaces constituting the three-dimensional elements 104 have a surface roughness Ra of less than 2 ⁇ m, preferably less than 1 ⁇ m.
• the top portion 105 performs an abrading function. While the abrasive material is subjected to abrasion, the three-dimensional elements are decomposed starting from the top portion, thereby allowing unused abrasive grains to appear. Therefore, in order to increase the abrasive property of the abrasive material, the concentration of the abrasive grains in the abrasive composite located in the top portion of the three-dimensional element is preferably increased to be as high as possible so that the abrasive material may have a higher abrasive property to be suited for abrading a hard material.
• the concentration of the abrasive grains in the abrasive composite located in the top portion of the three-dimensional element more preferably exceeds the critical pigment volume concentration.
• the critical pigment volume concentration is considered to be the pigment volume concentration where there is just sufficient binder to coat pigment surfaces and provide a continuous phase throughout the film.
• the critical pigment volume concentration as used herein means a volume concentration of abrasive grains when the gaps among the grains are just filled with a binder. In the case where the binder is liquid, the mixture has fluidity if the concentration is less than the critical pigment volume concentration, whereas the mixture loses its fluidity if the concentration exceeds the critical pigment volume concentration.
• the concentration of the abrasive grains in the abrasive composite located in the top portion of the three-dimensional element is less than or equal to the critical pigment volume concentration, the abrasive property of the abrasive material will be insufficient, so that the abrasive material will not be suitable for abrasion of a hard material such as an end surface of an optical fiber connector.
• the foot portion 106 of the three-dimensional element namely the lower portion of the abrasive layer adhering to the base material, does not usually perform an abrading function. This is because, if the abrasive layer is worn to the lower portion, the abrasive material is usually discarded.
• the foot portion 106 of the three-dimensional element that does not perform the abrading function need not contain abrasive grains, so that the foot portion 106 may be made of the binder alone.
• the binder in the foot portion 106 can be designed considering only the adhesive power of the binder to the base material, poor adhesion to the base material hardly occurs.
• the symbol s represents the height of the top portion 105 of the three- dimensional element.
• the height s is, for example, 5 to 95%. preferably 10 to 90%, of the height h of the three-dimensional element.
• Fig. 2 is a top view of this abrasive material.
• the symbol o represents the bottom side length of the three-dimensional element.
• the symbol p represents the distance between the tops of adjacent three-dimensional elements.
• the length o is, for example, 5 to 1000 ⁇ m, preferably 10 to 500 ⁇ m.
• the distance p is, for example, 5 to 1000 ⁇ m, preferably 10 to 500 ⁇ m.
• the three-dimensional element may have a tetrahedral or pyramidal shape whose top is truncated to a predetermined height.
• the top of the three-dimensional element is preferably formed of a triangular or quadrangular plane parallel to the surface of the base material, and substantially all of these planes are preferably located on a plane parallel to the surface of the base material.
• the height of the three-dimensional element is 5 to 95%, preferably 10 to 90%, of the height h of the three-dimensional element before truncation of the top.
• Fig. 3 is a top view of the abrasive material according to this embodiment.
• Fig. 3 is a perspective section view of an abrasive material having an abrasive layer of a three-dimensional structure according to another embodiment of the present invention.
• An abrasive material 400 is an abrasive material having a base material 401 and an abrasive layer 402 disposed on the surface of the base material.
• the abrasive layer 402 has an abrasive composite containing a matrix of a binder and abrasive grains 403 dispersed therein as construction components.
• the abrasive layer 402 has a three-dimensional structure constructed with a plurality of regularly arranged three-dimensional elements having a predetermined shape.
• the three-dimensional elements 404 has a prismatic shape formed of a laterally-placed triangular prism.
• the angle ⁇ of the three-dimensional element 404 is typically 30 to 150°, preferably 45 to 140°.
• the ridges on the top of the three-dimensional elements 404 are located on a plane parallel to the surface of the base material substantially over an entire region of the abrasive material.
• the symbol h represents the height of the three-dimensional element from the surface of the base material.
• the height h is typically 2 to 600 ⁇ m, preferably 4 to 300 ⁇ m.
• the variation of the height of the top lines is preferably less than
• the three-dimensional element 404 preferably has a two-layer structure including a top portion 405 made of an abrasive composite and a foot portion 406 made of a binder.
• the symbol s represents the height of the top portion of the three-dimensional element. The height s is, for example,
• the three-dimensional elements 404 are arranged in a stripe pattern.
• the symbol w represents the length of the short bottom side of the three- dimensional element (width of the three-dimensional element).
• the symbol p represents the distance between tops of adjacent three-dimensional elements.
• the symbol u represents the distance between long bottom sides of adjacent three-dimensional elements.
• the length w is, for example, 2 to 2000 ⁇ m, preferably 4 to 1000 ⁇ m.
• the distance p is, for example, 2 to 4000 ⁇ m, preferably 4 to 2000 ⁇ m.
• the distance u is, for example, 0 to 2000 ⁇ m, preferably 0 to 1000 ⁇ m.
• the length of the three-dimensional element may extend substantially over an entire region of the abrasive material.
• the length of the three-dimensional element may be cut to a suitable length.
• the ends of the three-dimensional elements may be either aligned or non-aligned.
• the ends of the prismatic three-dimensional elements may be cut at an acute angle from its bottom to form a house shape having four inclined surfaces.
• Fig. 5 is a top view of the abrasive material according to this embodiment.
• the symbol 1 represents the length of a long bottom side of the three-dimensional element.
• the symbol v represents the distance of a portion of the three-dimensional element cut at an acute angle.
• the symbol x represents the distance between short bottom sides of adjacent three-dimensional elements.
• the symbols w, p, and u have the same meaning as in Fig. 4.
• the length 1 is, for example, 5 to 10000 ⁇ m, preferably 10 to 5000 ⁇ m.
• the distance v is, for example, 0 to 2000 ⁇ m, preferably 1 to 1000 ⁇ m.
• the distance x is, for example. 0 to 2000 ⁇ m, preferably 0 to 1000 ⁇ m.
• the length w is, for example, 2 to 2000 ⁇ m, preferably 4 to 1000 ⁇ m.
• the distance p is, for example, 2 to 4000 ⁇ m. preferably 4 to 2000 ⁇ m.
• the distance u is, for example, 0 to 2000 ⁇ m, preferably 0 to 1000 ⁇ m.
• the abrasive material having an abrasive layer of a three-dimensional structure of the present invention exemplified in Figs. 1 to 5 are particularly suited for use in abrading an end surface of an optical fiber connector, and can provide an end surface of an optical fiber connector with an extremely small connection loss.
• the abrasive material having an abrasive layer of a three-dimensional structure according to the present invention provides an end surface of an optical fiber connector with a connection loss of less than 1.0 dB, or less than 0.5 dB.
• the abrasive material of the present invention is preferably produced by the method described below.
• an abrasive slurry which contains abrasive grains, a binder, and a solvent.
• the abrasive slurry to be used herein is a composition containing the binder, the abrasive grains, and optional additives such as a photoinitiator in sufficient amounts to constitute an abrasive composite and further containing a volatile solvent in a sufficient amount to impart fluidity to the mixture. Even if the content of the abrasive grains in the abrasive composite exceeds the critical pigment volume concentration, the fluidity can be maintained by allowing the abrasive slurry to contain a volatile solvent.
• a preferable volatile solvent is an organic solvent that dissolves the binder and shows volatility at room temperature to 170°C.
• the organic solvent include methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, ethanol, isopropyl alcohol, ethyl acetate, butyl acetate, tetrahydrofuran, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate.
• Another preferable solvent is water.
• a mold sheet which has a plurality of regularly arranged recesses tapered toward the bottom.
• the shape of the recesses may be an inverse of the three-dimensional elements to be formed.
• the mold sheet may be made of a metal such as nickel or plastics such as polypropylene.
• a thermoplastic resin such as polypropylene is preferable because it can be embossed at its melting point on a metal tool to form recesses of a predetermined shape.
• the binder is a radiation-curing type resin, it is preferable to use a material that transmits ultraviolet rays and visible light.
• Figs. 6(a) to 6(e) are model views showing steps for producing an abrasive material having an abrasive layer of a three-dimensional structure.
• the obtained mold sheet 601 is filled with an abrasive slurry 602.
• the amount of the abrasive slurry to be used in filling the mold sheet is such that it can form a top portion 105, 405 after the solvent is evaporated and the binder is hardened.
• the amount of the abrasive slurry may be such that its depth from the bottom is a dimension s shown in Figs. 1 and 4 after the evaporation of the solvent.
• the mold sheet can be filled with the abrasive slurry by applying the abrasive slurry onto the mold sheet by means of a coating apparatus such as a roll coater.
• the viscosity of the abrasive slurry for application is preferably adjusted to be 10 to 106 cps, particularly 100 to 105 cps.
• the solvent is evaporated and removed from the abrasive slurry.
• the mold sheet filled with the abrasive slurry is heated to 50 to 150°C for 0.2 to 10 minutes. If the binder is a thermoplastic resin, the mold sheet may be heated at its curing temperature for simultaneously performing a hardening step. If the volatility of the solvent is high, the mold sheet may be left to stand at room temperature for several minutes to several hours.
• the mold sheet is further filled with a binder 603 for lamination to fill the recesses with the binder.
• the lamination binder may be the same as or different from the one used in preparing the abrasive slurry.
• a binder having a good adhesion to the base material is preferable as the lamination binder.
• the lamination binder is acrylate resin, epoxy resin, and urethane resin.
• the mold sheet may be filled with the lamination binder in the same manner as the abrasive slurry.
• a base material 604 is superposed on the mold sheet 601 to allow the binder to adhere to the base material.
• the adhesion is carried by pressing with a roll for lamination.
• the binder is hardened.
• hardening means that the binder is polymerized into a solid state. After the hardening, the specific shape of the abrasive layer does not change.
• the hardening of the binder in the abrasive slurry and the hardening of the lamination binder introduced alone at the later step may be performed either separately or simultaneously.
• the binder is hardened by heat, infrared radiation, or by electron beam radiation, ultraviolet radiation, or by another radiation energy such as visible light radiation.
• the amount of radiation energy to be applied may vary depending on the type of the binder and the radiation energy source. Usually, those skilled in the art can suitably determine the amount of radiation energy to be applied.
• the period of time required in hardening may vary depending on the thickness, density, temperature of the binder, the properties of the composition, and others.
• the binder may be hardened by radiating ultraviolet rays (UV) from above the transparent base material.
• UV ultraviolet rays
• the mold sheet is removed to produce an abrasive material 606 composed of the base material 604 and the abrasive layer 605 having a three-dimensional structure.
• the binder may be hardened after the mold sheet is removed.
• An abrasive material coating solution was prepared by mixing the components shown in Table 1.
• a lamination binder was prepared by mixing the components shown in Table 2.
• a mold sheet made of polypropylene and having recesses with a shape of inverted three-dimensional elements shown in Fig. 4 was prepared.
• An abrasive slurry was applied onto the mold sheet by means of a roll coater and dried at 50°C for 5 minutes.
• a lamination binder was applied thereon and further a transparent polyester film having a thickness of 75 ⁇ m was superposed and pressed by a roll for lamination. Ultraviolet rays were radiated from the polyester film side to harden the lamination binder. Subsequently, the binder of the abrasive slurry was hardened by heating at 70°C for 24 hours.
• the mold sheet was removed and the resultant was cooled to room temperature to produce an abrasive material.
• the abrasive layer has a three- dimensional structure having a prismatic shape arranged in a stripe pattern shown in Fig. 4. The dimensions thereof are shown in Table 3.
• Table 3 This abrasive material was stamped out into a circular shape having a diameter of 1 10 mm to fabricate an abrasive disk. An end surface of an optical connector ferrule was abraded with the use of the obtained abrasive disk. The abrasion conditions are shown in Table 4.
• An abrasive slurry was prepared by mixing the components shown in Table 5.
• Abrasive grains/(binder + additives) proportion 2.86
• An abrasive disk was fabricated in the same manner as in Example 1 except that this abrasion slurry was used, and an end surface of an optical connector ferrule was abraded. The change with time of the abraded amount is shown in Fig. 7. After the abrasion, the end surface of the optical connector ferrule was observed by an electron microscope, whereby a smooth surface was confirmed. The obtained microscope photograph is shown in Fig. 9.
• An abrasive material "Imperial Sign Diamond Lapping Film 3 Mil 3 Micron Type H” made by Minnesota Mining and Manufacturing Co., Ltd. was stamped out into a circular shape having a diameter of 110 mm to fabricate an abrasive disk.
• An end surface of an optical connector ferrule was abraded in the same manner as in Example 1 except that this abrasive disk was used. The change with time of the abraded amount is shown in Fig. 7. After the abrasion, the end surface of the optical connector ferrule was observed by an electron microscope, whereby a rough surface was confirmed. The obtained microscope photograph is shown in Fig. 10.
• the abrasive slurry prepared in Example 1 was applied onto a polyester film having a thickness of 75 ⁇ m by means of a knife coater and the solvent was removed by evaporation to form an abrasive layer having a thickness of 11 ⁇ m.
• the abrasive layer was heated at 70°C for 24 hours to harden the binder.
• the obtained abrasive material was stamped out into a circular shape having a diameter of 110 mm to fabricate an abrasive disk.
• An end surface of an optical connector ferrule was abraded in the same manner as in Example 1 except that this abrasive disk was used. The change with time of the abraded amount is shown in Fig. 7. After the abrasion, the end surface of the optical connector ferrule was observed by an electron microscope, whereby a rough surface was confirmed. The obtained microscope photograph is shown in Fig. 11. Comparative Example 3
• the abrasive slurry prepared in Example 2 was applied onto a polyester film having a thickness of 75 ⁇ m by means of a knife coater and the solvent was removed by evaporation to form an abrasive layer having a thickness of 11 ⁇ m.
• the abrasive layer was heated at 70°C for 24 hours to harden the binder.
• the obtained abrasive material was stamped out into a circular shape having a diameter of 110 mm to fabricate an abrasive disk.
• Figs. 8 and 9 By comparing Figs. 8 and 9 with Fig. 10, it will be understood that the abrasive materials of Examples 1 and 2 give a more smooth abraded surface than the abrasive material of Comparative Example 1 which is a current product. Also, by comparing Fig. 8 with Fig. 11, it will be understood that the abrasive material of Example 1 gives a more smooth surface than the abrasive material of Comparative Example 2 which is an abrasive material made of the same slurry but having an abrasive layer without a three-dimensional structure. By comparing Fig. 9 with Fig. 12, it will be understood that the abrasive material of Example 2 gives a more smooth surface than the abrasive material of
• Comparative Example 3 which is an abrasive material made of the same slurry but having an abrasive layer without a three-dimensional structure.
• Example 2 exhibits a higher abrasive property than the abrasive disks of Comparative Examples 1 to 3.
• An abrasive slurry was applied onto the mold sheet by means of a roll coater and dried at 60°C for 5 minutes.
• a lamination binder prepared in Example 1 was applied thereon and further a transparent polyester film having a thickness of 75 ⁇ m was superposed and pressed by a roll for lamination. Ultraviolet rays were radiated from the polyester film side to harden the binder.
• the mold sheet was removed and the resultant was cooled to room temperature to produce an abrasive material. This abrasive material was stamped out into a circular shape having a diameter of 110 mm to fabricate an abrasive disk.
• an optical connector ferrule was prepared and an end surface thereof was abraded under the same abrasion condition as in Table 7 with the use of an abrasive material "Imperial Sign Diamond Lapping Film 3 Mil 0.5 Micron Type H" made by Minnesota Mining and Manufacturing Co., Ltd. An end surface of this optical connector ferrule was further abraded with the use of the fabricated abrasive disk.
• the abrasion condition is shown in Table 7.
• An abrasive slurry was prepared by mixing the components shown in Table 8.
• An abrasive disk was fabricated in the same manner as in Example 3 except that this abrasive slurry was used, and an end surface of an optical connector ferrule was abraded. A microscope photograph of the end surface after the abrasion is shown in
• Comparative Example 5 The abrasive slurry prepared in Example 3 was applied onto a polyester film having a thickness of 75 ⁇ m by means of a knife coater and the solvent was removed by evaporation to form an abrasive layer having a thickness of 4 ⁇ m. A polyester film having a thickness of 31 ⁇ m was laminated on this abrasive layer, and the binder was hardened by radiating ultraviolet rays. The obtained abrasive material was stamped out into a circular shape having a diameter of 1 10 mm to fabricate an abrasive disk.
• An end surface of an optical connector ferrule was abraded in the same manner as in Example 3 except that this abrasive disk was used. However, attachments accumulated on the end surface during the abrasion, making it impossible to perform effective abrasion.
• the abrasive slurry prepared in Example 4 was applied onto a polyester film having a thickness of 75 ⁇ m by means of a knife coater and the solvent was removed by evaporation to form an abrasive layer having a thickness of 4 ⁇ m.
• a polyester film having a thickness of 31 ⁇ m was laminated on this abrasive layer, and the binder was hardened by radiating ultraviolet rays.
• the obtained abrasive material was stamped out into a circular shape having a diameter of 1 10 mm to fabricate an abrasive disk.
• An end surface of an optical connector ferrule was abraded in the same manner as in Example 3 except that this abrasive disk was used. However, attachments accumulated on the end surface during the abrasion, making it impossible to perform effective abrasion.
• An abrasive slurry was prepared by mixing the components shown in Table 10.
• An abrasive slurry was applied onto the mold sheet by means of a roll coater and dried at 70°C for 5 minutes.
• a lamination binder prepared in Example 1 was applied thereon and further a transparent polyester film having a thickness of 75 ⁇ m was supe ⁇ osed and pressed by a roll for lamination. Ultraviolet rays were radiated from the polyester film side to harden the lamination binder. Subsequently, the binder in the abrasive slurry was hardened by heating at 70°C for 24 hours.
• the resultant was cooled to room temperature and the mold sheet was removed to produce an abrasive material.
• This abrasive material was stamped out into a circular shape having a diameter of 110 mm to fabricate an abrasive disk.
• a circular rod of zirconia (diameter: 3 mm) was abraded with the use of the fabricated abrasive disk.
• the abrasion conditions are shown in Table 11.
• Table 1 1 The change with time of the abraded amount is shown in Fig 16 Subsequently, the abrasive disk was replaced with a new one, and the end surface of the optical connector ferrule was abraded The abrasion condition is shown in Table 12
• abrasive material was fabricated in the same manner as in Example 5 except that a mold sheet made of polypropylene and having recesses with a shape of inverted three-dimensional elements shown in Fig 5 was used
• the abrasive layer has a three-dimensional structure of a house shape arranged in a stripe pattern as shown in Fig 5 The dimensions are shown in Table 13
• the symbols h, s, and ⁇ represent the height of the three-dimensional element, the height of the top portion of the three-dimensional element, and the angle shown in Fig. 4, respectively.
• the obtained abrasive material was stamped out into a circular disk having a diameter of 1 10 mm to fabricate an abrasive disk.
• a circular rod of zirconia and an end surface of an optical connector ferrule were abraded with the use of this abrasive disk in the same manner as in Example 5.
• the change with time of the abraded amount of the circular rod of zirconia is shown in Fig. 16.
• the end surface of the optical connector ferrule was observed by an electron microscope, whereby a smooth surface was confirmed.
• a microscope photograph is shown in Fig. 18.
• abrasive material was fabricated in the same manner as in Example 5 except that a mold sheet made of polypropylene and having recesses with a shape of inverted three-dimensional elements shown in Figs. 1 and 2 was used.
• the abrasive layer has a three-dimensional structure of a tetrahedral shape most closely packed as shown in Figs. 1 and 2. The dimensions are shown in Table 14.
• the obtained abrasive material was stamped out into a circular disk having a diameter of 1 10 mm to fabricate an abrasive disk.
• a circular rod of zirconia and an end surface of an optical connector ferrule were abraded with the use of this abrasive disk in the same manner as in Example 5.
• the change with time of the abraded amount of the circular rod of zirconia is shown in Fig. 16.
• the end surface of the optical connector ferrule was observed by an electron microscope, whereby a smooth surface was confirmed.
• a microscope photograph is shown in Fig. 19.
• abrasive material was fabricated in the same manner as in Example 5 except that a mold sheet made of polypropylene and having recesses with a shape of inverted three-dimensional elements shown in Fig. 4 and being of a different type from the one used in Example 5 was used.
• the abrasive layer has a three- dimensional structure of a prismatic shape arranged in a stripe pattern as shown in Fig. 4. The dimensions are shown in Table 15.
• the obtained abrasive material was stamped out into a circular disk having a diameter of 110 mm to fabricate an abrasive disk.
• a circular rod of zirconia and an end surface of an optical connector ferrule were abraded with the use of this abrasive disk in the same manner as in Example 5.
• the change with time of the abraded amount of the circular rod of zirconia is shown in Fig. 16.
• the end surface of the optical connector ferrule was observed by an electron microscope, whereby a smooth surface was confirmed.
• a microscope photograph is shown in Fig. 20.
• Type H made by Minnesota Mining and Manufacturing Co., Ltd. was stamped out into a circular shape having a diameter of 110 mm to fabricate an abrasive disk.
• a circular rod of zirconia and an end surface of an optical connector ferrule were abraded in the same manner as in Example 5 except that this abrasive disk was used.
• the change with time of the abraded amount of the circular rod of zirconia is shown in Fig. 16.
• the end surface of the optical connector ferrule was observed by an electron microscope, whereby a rough surface was confirmed. A microscope photograph is shown in Fig. 21.
• the abrasive slurry prepared in Example 5 was applied onto a polyester film having a thickness of 75 ⁇ m by means of a knife coater and the solvent was removed by evaporation to form an abrasive layer having a thickness of 14 ⁇ m.
• the abrasive layer was heated at 70°C for 24 hours and further heated at 100°C for 24 hours to harden the binder.
• the abrasive material obtained by cooling to room temperature was stamped out into a circular shape having a diameter of 1 10 mm to fabricate an abrasive disk.
• a circular rod of zirconia and an end surface of an optical connector ferrule were abraded in the same manner as in Example 6 except that this abrasive disk was used.
• the change with time of the abraded amount of the circular rod of zirconia is shown in Fig. 16.
• the end surface of the optical connector ferrule was observed by an electron microscope, whereby a rough surface was confirmed.
• a microscope photograph is shown in Fig. 22.
• An abrasive slurry was prepared by mixing the components shown in Table 16.
• a lamination binder was prepared by mixing the components shown in Table 17. Table 17
• Example 2 The same mold sheet made of polypropylene as used in Example 1 was prepared. An abrasive slurry was applied onto the mold sheet by means of a roll coater and dried at
• the lamination binder was applied thereon and further a transparent polyester film having a thickness of 75 ⁇ m was supe ⁇ osed and pressed by a roll for lamination. Ultraviolet rays were radiated from the polyester film side to harden the lamination binder. Subsequently, the binder in the abrasive slurry was hardened by heating at 70°C for 24 hours.
• the resultant was cooled to room temperature and the mold sheet was removed.
• the binder in the abrasive layer was hardened by further heating at 100°C for 24 hours.
• This abrasive material was stamped out into a circular shape having a diameter of 1 10 mm to fabricate an abrasive disk.
• a circular rod of zirconia and an end surface of an optical fiber connector were abraded in the same manner as in Example 5 except that this abrasive disk was used.
• the change with time of the abraded amount of the circular rod of zirconia is shown in Fig. 16.
• the end surface of the optical fiber connector was observed by an electron microscope, whereby a smooth surface was confirmed.
• a microscope photograph is shown in Fig. 23.
• An abrasive material was fabricated in the same manner as in Example 9 except that the same mold sheet made of polypropylene as used in Example 6 was used. This abrasive material was stamped out into a circular shape having a diameter of 1 10 mm to fabricate an abrasive disk. A circular rod of zirconia and an end surface of an optical fiber connector were abraded in the same manner as in Example 5 except that this abrasive disk was used. The change with time of the abraded amount of the circular rod of zirconia is shown in Fig. 16.
• the end surface of the optical fiber connector was observed by an electron microscope, whereby a smooth surface was confirmed. A microscope photograph is shown in Fig. 24.
• abrasive material was fabricated in the same manner as in Example 9 except that a mold sheet made of polypropylene and having recesses with a shape of inverted three-dimensional elements shown in Fig. 3 was used.
• the abrasive layer has a three-dimensional structure of a pyramidal shape shown in Fig. 3 in which the top is truncated at a predetermined height. The dimensions are shown in Table 18.
• the symbols h, s, and ⁇ represent the height of the three-dimensional element, the height of the top portion of the three-dimensional element, and the angle formed between two ridges of the three-dimensional element before the top is truncated, respectively.
• the obtained abrasive material was stamped out into a circular shape having a diameter of 110 mm to fabricate an abrasive disk.
• a circular rod of zirconia and an end surface of an optical fiber connector were abraded in the same manner as in Example 5 except that this abrasive disk was used.
• the change with time of the abraded amount of the circular rod of zirconia is shown in Fig. 16.
• the end surface of the optical fiber connector was observed by an electron microscope, whereby a smooth surface was confirmed.
• FIG. 25 A microscope photograph is shown in Fig. 25. From the graph shown in Fig. 16, it will be understood that the abrasive disks of Examples 5 to 11 exhibit a higher abrasive property and a longer product life than the abrasive disks of Comparative Examples 7 and 8. Also, by comparing Figs. 17 to 20 and 23 to 25 with Figs. 21 and 22, it will be understood that the abrasive disks of Examples 5 to 1 1 give a more smooth abraded surface than the abrasive disk of Comparative
• Example 7 which is a current product and the abrasive disk of Comparative Example 8 having an abrasive layer without a three-dimensional structure.

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