Plastic optical fiber, optical fiber cable, plugged optical fiber cable, and production methods thereof

Abstract

The present invention relates to a production method of a plastic optical fiber which comprises the steps of heat drawing an undrawn plastic optical fiber obtained by melt spinning and annealing the drawn fiber at a circumferential velocity ratio between the front and rear rollers (circumferential velocity of a rear roller/circumferential velocity of a front roller) of 0.5 to 1.2 under heating conditions which satisfy 4≦y≦1.5x+330 and (Tgc−5)° C.≦x≦(Tgc+110)° C. [Tgc: a glass transition temperature of a core, x: an annealing temperature (° C.), and y: an annealing time (seconds)]. According to the present invention, a plastic optical fiber having a small thermal shrinkage ratio and excellent heat resistance can be provided.

1 . A plastic optical fiber having a shrinkage stress occurring temperature obtained by thermomechanical analysis of not lower than [(a glass transition temperature of a core)−35]° C.  
   
   
       2 . The plastic optical fiber as claimed in  claim 1 , wherein the core comprises a homopolymer of methyl methacrylate, or a copolymer comprising a methyl methacrylate unit and another monomer unit.  
   
   
       3 . The plastic optical fiber as claimed in  claim 1 , wherein the core comprises a homopolymer of methyl methacrylate and has a birefringence absolute value of not larger than 2.0×10 −4 .  
   
   
       4 . A plastic optical fiber which has a core comprising a homopolymer of methyl methacrylate and having a birefringence absolute value of not smaller than 1.5×10 −4  and has a shrinkage stress occurring temperature obtained by thermomechanical analysis of not lower than [(a glass transition temperature of the core)−20]° C.  
   
   
       5 . The plastic optical fiber as claimed in any one of  claims 1  to  4 , which exhibits a shrinkage ratio of not higher than 2% when heated at 90° C. for 65 hours.  
   
   
       6 . The plastic optical fiber as claimed in  claim 4 , which exhibits a shrinkage ratio of not higher than 0.5% when heated at 90° C. for 65 hours.  
   
   
       7 . A plastic optical fiber cable obtained by forming a coating layer around the plastic optical fiber a: claimed in any one of  claims 1  to  6 .  
   
   
       8 . A plastic optical fiber cable that has a protective layer comprising a vinylidene fluoride-tetrafluoroethylene copolymer formed around the plastic optical fiber as claimed in any one of  claims 1  to  6  having a core-sheath structure in which the sheath comprises a polymer containing a fluorine-based methacrylate unit or a vinylidene fluoride unit and that has a coating layer comprising Nylon 12 formed on the protective layer.  
   
   
       9 . A plugged plastic optical fiber cable obtained by attaching a plug on the tip of the plastic optical fiber cable as claimed in  claim 7  or  8 .