Coated optical fiber and radiation-curable resin composition

Abstract

Provided is a radiation curable resin composition suitable for use as a primary coating material for optical fibers, which can form a cured coating with a low modulus of elasticity exhibiting a high breaking strength, and small light transmission loss; the coating composition comprises (A) a polymer containing polymerizable unsaturated groups in an average amount of 1.2 per molecule, a urethane bond in a molecular chain, and having a number average molecular weight from 3,000 to 30,000, (B) a poly-functional monomer having two or more polymerizable unsaturated groups, (C) a monomer having one polymerizable unsaturated group, and (D) a radiation active initiator. The secant modulus of the coating is less than 0.15 kg/mm 2 , the tensile strength is more than 0.15 kg/mm 2 .

What is claimed is:  
     
         1 . A radiation curable resin composition comprising: 
 (A) a polymer containing polymerizable unsaturated groups in an average amount of 1.2-4 per one molecule, a urethane bond in a molecular chain, and having a number average molecular weight from 3,000 to 30,000,    (B) a poly-functional monomer having two or more polymerizable unsaturated groups,    (C) a monomer having one polymerizable unsaturated group, and,    (D) a radiation active initiator.    
     
     
         2 . The composition of  claim 1 , wherein the composition after irradiation with a dose of 1 J/cm 2  ultraviolet radiation in air has a secant modulus of 0.15 kg/mm 2  or less and a tensile strength of 0.15 kg/mm 2  or more.  
     
     
         3 . The composition of  claim 1 , wherein curing said composition can produce a product having a viscoelasticity curve having a total of at least one peak and at least one shoulder, or at least two peaks in a temperature range from −50° C. to +35° C. in a temperature dependency curve of loss tangent.  
     
     
         4 . The composition of  claim 3 , wherein said product has at least one peak or shoulder in a temperature range from −50° C. to −20° C. and at least one peak or shoulder in a temperature range from −20° C. to +35° C. in the temperature dependency curve of loss tangent.  
     
     
         5 . The composition of  claim 1 , wherein the composition comprises: 
 (A) 25 to 75 wt % of a polymer containing polymerizable unsaturated groups in an average amount of 1.2-4 per molecule, a urethane bond and a polyoxyalkylene structure in a molecular chain, and having an average molecular weight from 3,000 to 30,000,    (B) 0.1 to 10 wt % of a poly-functional monomer having 2 to 6 polymerizable unsaturated groups,    (C) 20 to 70 wt % of a monomer having a one polymerizable unsaturated group, and    (D) 0.1 to 10 wt % of a radiation-active initiator.    
     
     
         6 . The composition of  claim 1 , wherein the polymer (A) possesses an average of 1.5-2.5 polymerizable unsaturated groups per molecule.  
     
     
         7 . The composition of  claim 1 , wherein the whole or a portion of the main chain of the polymer (A) is a polyether polyol-type urethane acrylate polymer.  
     
     
         8 . The composition of  claim 1 , wherein the component (B) is selected from the group consisting of diacrylate compounds and triacylate compounds having a molecular weight of 800 or less.  
     
     
         9 . The composition of  claim 1 , wherein the component (B) is selected from the group consisting of 1,6-hexanedioldiacrylate, 1,9-nonanediolacrylate, triethylene glycol diacrylate, tricyclodecanedimethanol diacrylate, and trimethylolpropane alkoxytriacylate.  
     
     
         10 . The composition of  claim 1 , wherein the component (C) has a molecular weight of 100-1000.  
     
     
         11 . The composition of  claim 1 , wherein said component (C) includes at least one N-vinyllactam.  
     
     
         12 . The composition of  claim 1 , wherein said component (C) includes at least one N-vinyllactam and at least one monomer having an alicyclic structure.  
     
     
         13 . The composition of  claim 1 , wherein said composition has a viscosity of 1,000-20,000 cP at 25° C.  
     
     
         14 . A coated optical fiber comprising: 
 a coating having, 
 a tensile strength at break of more than 0.15 kg/mm 2 , and  
 a secant modulus of 0.15 kg/mm 2  or less.  
   
     
     
         15  The coated optical fiber of  claim 14 , wherein said coating is formed from a radiation-curable composition comprising: 
 (A) a polymer composition comprising one or more polymers having, 
 (i) urethane bonds in a molecular chain, and  
 (ii) a number average molecular weight of 3,000-30,000,  
 
 wherein the composition has on average 1.2 or more polymerizable unsaturated groups per polymer molecule;  
 (B) a poly-functional monomer having two or more polymerizable unsaturated groups;  
 (C) a monomer having one polymerizable unsaturated group; and  
 (D) a radiation-active initiator.  
 
     
     
         16 . The coated optical fiber of  claim 15 , wherein the polymer composition (A) comprises a polyether polyol urethane-based polymer.  
     
     
         17 . The coated optical fiber of  claim 15 , wherein the polymer composition (A) comprises a polymer derived from a polyoxyalkylene polyether polyol.  
     
     
         18 . The coated optical fiber of  claim 15 , wherein the polymer composition includes at least one polymer having 2-10 urethane bonds.  
     
     
         19 . The coated optical fiber of  claim 15 , wherein the radiation-curable compostion comprises, relative to the total radiation-curable composition, between 40 and 70% wt of the polymer composition (A).  
     
     
         20 . The coated optical fiber of claims  15 , wherein the poly-functional monomer (B) has a molecular weight of 800 or less.  
     
     
         21 . The coated optical fiber of  claim 15 , wherein the monomer (C) comprises a polymerizable vinyl group.  
     
     
         22 . The coated optical fiber of  claim 15 , wherein the radiation-curable composition has a viscosity, at 25° C., of from 1,000 to 20,000 cP.  
     
     
         23 . The coated optical fiber of  claim 15 , wherein said coating has a viscoelasticity curve having a total of at least one peak and at least one shoulder, or at least two peaks in a temperature range from −50° C. to +35° C. in a temperature dependency curve of loss tangent.