Polishing member and method for polishing end faces of optical fibers

Abstract

A polishing member for polishing an end face of an optical fiber comprises a substrate and a polishing layer overlaid on the substrate, the polishing layer having been formed with application of a coating composition, which contains a binder and polishing particles as principal constituents, onto the substrate. The polishing layer contains first particles, which act as the polishing particles and are constituted of silica particles having a mean particle diameter falling within the range of 5 nm to 50 nm, and second particles, which are constituted of silica particles having a mean particle diameter 50 to 2,500 times as large as the mean particle diameter of the first particles.

What is claimed is:  
     
         1 . A polishing member for polishing an end face of an optical fiber, the polishing member comprising: 
 i) a substrate, and    ii) a polishing layer overlaid on the substrate, the polishing layer having been formed with application of a coating composition, which contains a binder and polishing particles as principal constituents, onto the substrate,    wherein the polishing layer contains: 
 a) first particles, which act as the polishing particles and are constituted of silica particles having a mean particle diameter falling within the range of 5 nm to 50 nm, and  
 b) second particles, which are constituted of silica particles having a mean particle diameter 50 to 2,500 times as large as the mean particle diameter of the first particles.  
   
     
     
         2 . A polishing member as defined in  claim 1  wherein the second particles are used in a proportion falling within the range of 1 part by weight to  5  parts by weight per 100 parts by weight of the first particles.  
     
     
         3 . A polishing member as defined in  claim 1  wherein the second particles exhibit oil absorption falling within the range of 10 ml/100 g to 400 ml/100 g.  
     
     
         4 . A polishing member as defined in  claim 1  wherein the second particles have a spherical shape.  
     
     
         5 . A polishing member as defined in  claim 1  wherein the binder contained in the polishing layer contains a polyurethane resin.  
     
     
         6 . A polishing member as defined in  claim 5  wherein the polyurethane resin has the characteristics, such that a glass transition temperature Tg is at most 40° C., and/or an elongation is at least 200%.  
     
     
         7 . A polishing member as defined in  claim 1  wherein the ratio of the first particles and the second particles to the binder takes a value between 1:0.2 and 1:2.  
     
     
         8 . A method of polishing an end face of an optical fiber, the method comprising the steps of: 
 i) bringing an end face of an optical fiber connector, which comprises a ferrule having a center hole and an optical fiber having been inserted and secured in the center hole of the ferrule, into contact with a polishing member having a polishing layer, which comprises a binder and silica particles dispersed in the binder,    ii) subjecting the end face of the optical fiber connector to sliding movement on the polishing member, while the end face of the optical fiber connector is being in contact with the polishing member, and    iii) supplying a silica slurry, which acts as a polishing liquid, to the sliding contact area, at which the end face of the optical fiber connector is in sliding contact with the polishing member, the silica slurry containing fine-particle silica, which has a mean particle size falling within the range of 1 nm, inclusive, to a value smaller than 20 nm, and water,    whereby the end face of the optical fiber connector is finish-polished into a convex spherical surface shape.    
     
     
         9 . A method as defined in  claim 8  wherein the silica slurry acting as the polishing liquid further contains an alcohol.  
     
     
         10 . A method as defined in  claim 8  wherein water contained in the silica slurry is deionized water and has an electric conductivity of at most 0.500 μS/cm at 25° C.  
     
     
         11 . A method as defined in  claim 8  wherein, as the polishing particles contained in the polishing layer of the polishing member, the silica particles are utilized alone or in combination with at least one different kind of polishing particles selected from the group consisting of cerium oxide, alumina, chromium oxide, silicon carbide, and diamond, and the silica particles constitute at least 50% of the polishing particles contained in the polishing layer of the polishing member.  
     
     
         12 . A method as defined in  claim 8  wherein the surface of the polishing layer of the polishing member is provided with a fine concavity-convexity pattern, such as a worm-shaped wrinkle pattern, a block-shaped pattern, an orange peel-shaped pattern, an arrayed protrusion pattern, or a random protrusion pattern.  
     
     
         13 . A method of polishing an end face of an optical fiber, the method comprising the steps of: 
 i) bringing an end face of an optical fiber connector, which comprises a ferrule having a center hole and an optical fiber having been inserted and secured in the center hole of the ferrule, into contact with a polishing member having a polishing layer, which comprises a binder and silica particles dispersed in the binder,    ii) subjecting the end face of the optical fiber connector to sliding movement on the polishing member, while the end face of the optical fiber connector is being in contact with the polishing member, and    iii) supplying a silica slurry, which acts as a polishing liquid, to the sliding contact area, at which the end face of the optical fiber connector is in sliding contact with the polishing member, the silica slurry containing coarse-particle silica, which has a mean particle size falling within the range of 20 nm, inclusive, to 500 nm, inclusive, and water, and having a pH value falling within the range of 8 to 12,    whereby the end face of the optical fiber connector is finish-polished into a convex spherical surface shape.    
     
     
         14 . A method as defined in  claim 13  wherein water contained in the silica slurry is deionized water and has an electric conductivity of at most 0.500 μS/cm at 25° C.  
     
     
         15 . A method as defined in  claim 13  wherein, as the polishing particles contained in the polishing layer of the polishing member, the silica particles are utilized alone or in combination with at least one different kind of polishing particles selected from the group consisting of cerium oxide, alumina, chromium oxide, silicon carbide, and diamond, and the silica particles constitute at least 50% of the polishing particles contained in the polishing layer of the polishing member.  
     
     
         16 . A method as defined in  claim 13  wherein the surface of the polishing layer of the polishing member is provided with a fine concavity-convexity pattern, such as a worm-shaped wrinkle pattern, a block-shaped pattern, an orange peel-shaped pattern, an arrayed protrusion pattern, or a random protrusion pattern.