Polymer film splicing method and device, and stretching method

Abstract

An off-line stretching device includes a film supply chamber, a tenter section, a relaxation chamber, a cooling chamber, and a winding chamber. The film supply chamber includes a splicing section, where a rear end of a preceding film and a front end of a trailing film are overlapped to be spliced to each other by thermal welding. The thermal welding is performed from above and below the film while a temperature of welding heads of a heat sealer, contacting with the film, is kept at a level equal to or less than a decomposition temperature of the preceding and trailing films. The spliced film is stretched in the tenter section and subjected to heat treatment for stress relaxation in the relaxation chamber, to shrink in a film width direction. Since the shrinkage amount of a spliced area and that of a peripheral area become equal to each other, the occurrence of wrinkles in the spliced area and tears of the film in the peripheral area can be prevented. Additionally, since a heat transfer distance between a film surface and a film splicing surface can be shortened, the heating from above and below the film enables high-speed welding.

1 . A splicing method of a polymer film comprising the steps of:
 overlapping a rear end of a preceding polymer film and a front end of a trailing polymer film;   pressing welding heads against a portion in which said preceding and trailing films are overlapped with each other from each side in a film overlapping direction while sandwiching said portion between said welding heads; and   welding said films while keeping a temperature of said welding heads contacting said film at a temperature equal to or less than a decomposition temperature of said polymer film, to splice said rear end and said front end to each other.   
     
     
         2 . A splicing method of a polymer film as defined in  claim 1 , wherein said polymer film is a cellulose ester film. 
     
     
         3 . A splicing device of a polymer film comprising:
 a welding head provided at each side of a portion in which a rear end of a preceding polymer film and a front end of a trailing polymer film are overlapped with each other in a film overlapping direction;   a shifter for moving said welding heads in said film overlapping direction between a pressing position and a retracted position, said welding heads sandwiching and pressing a portion in which said preceding and trailing films are overlapped with each other in said pressing position, and said welding heads being retracted from said pressing position in said retracted position; and   a heating controller for heating said welding heads contacting said preceding and trailing films at a temperature equal to or less than a decomposition temperature of said polymer film after said welding heads is shifted to said pressing position by said shifter.   
     
     
         4 . A splicing device of a polymer film as defined in  claim 3 , wherein said polymer film is a cellulose ester film. 
     
     
         5 . A polymer film stretching method comprising:
 splicing a rear end of a preceding polymer film and a front end of a trailing polymer film by welding a portion in which said rear end of said preceding film and said front end of said trailing film are overlapped with each other;   transporting continuously said polymer film after being spliced;   heating and stretching said transported polymer film by holding side ends of said polymer film with use of plural clips in a film width direction; and   subjecting said polymer film after being stretched to heat treatment for stress relaxation while continuously transporting said polymer film, such that a shrinkage amount of a spliced area of said preceding and trailing polymer films and a shrinkage amount of an area around said spliced area becomes approximately equal to each other in said film width direction.   
     
     
         6 . A polymer film stretching method as defined in  claim 5 , wherein said welding is performed with use of heat caused by a heat sealer. 
     
     
         7 . A polymer film stretching method as defined in  claim 5 , wherein said welding is performed with use of heat caused by ultrasonic vibration of an ultrasonic splicer. 
     
     
         8 . A polymer film stretching method as defined in  claim 5 , wherein said welding is performed with use of a polymer solvent. 
     
     
         9 . A polymer film stretching method comprising:
 splicing a rear end of a preceding polymer film and a front end of a trailing polymer film by adhering a splicing tape having an adhesive layer and no base to a portion in which said rear end of said preceding film and said front end of said trailing film are overlapped with each other;   transporting continuously said polymer film after being spliced;   heating and stretching said transported polymer film by holding side ends of said polymer film with use of plural clips in a film width direction; and   subjecting said polymer film after being stretched to heat treatment for stress relaxation while continuously transporting said polymer film, such that a shrinkage amount of a spliced area of said preceding and trailing polymer films and a shrinkage amount of an area around said spliced area becomes approximately equal to each other in said film width direction.