Polyimide film, image-forming apparatus, method for producing the polyimide film, and method for producing the intermediate transfer belt

Abstract

A polyimide film having a polyimide as the primary constituent and containing at least a polymeric electroconductive material, wherein in a weight-decrease vs. temperature-increase curve when the polyimide film is heated gradually from 30° C., a weight-decrease rate at a first inflection point, where an amount of difference in weight-decrease rates decreases first from 30° C., is in the range of −1.9% or more and −1.4% or less.

1 . A polyimide film having a polyimide as the primary constituent and containing at least a polymeric electroconductive material, wherein 
 in a weight-decrease vs. temperature-increase curve when the polyimide film is heated gradually from 30° C., a weight-decrease rate at an intersection between a tangent line which passes a first maximum point in the curve having the maximum value in the slope and a tangent line which passes a minimum point in the curve having the minimum value in the slope after the first point, is in the range of −1.9% or more and −1.4% or less.    
     
     
         2 . The polyimide film according to  claim 1 , wherein the polymeric electroconductive material contains polyaniline and a dopant that makes the polyaniline conductive.  
     
     
         3 . The polyimide film according to  claim 1 , wherein the rate of the temperature increase is 10° C./min when the polyimide film is heated gradually from 30° C.  
     
     
         4 . An image-forming apparatus for forming an image on a recording medium by forming a toner image on an image carrier and transferring and fixing the toner image finally onto the recording medium, comprising: 
 an intermediate transfer belt in contact with the image carrier whereon the toner image is formed for receiving the toner image from the image carrier once by application of a bias voltage and transferring the toner image onto the recording medium, wherein    the intermediate transfer belt is made of a polyimide film having a polyimide as the primary constituent and containing at least a polymeric electroconductive material, and    in a weight-decrease vs. temperature-increase curve when the intermediate transfer belt is heated gradually from 30° C., a weight-decrease rate at an intersection between a tangent line which passes a first maximum point in the curve having the maximum value in the slope and a tangent line which passes a minimum point in the curve having the minimum value in the slope after the first point, is in the range of −1.9% or more and −1.4% or less.    
     
     
         5 . The image-forming apparatus according to  claim 4 , wherein the polymeric electro conductive material contains polyaniline and a dopant for making the polyaniline conductive.  
     
     
         6 . The image-forming apparatus according to  claim 4 , wherein the rate of the temperature increase is 10° C./min when the polyimide film is heated gradually from 30° C.  
     
     
         7 . The image-forming apparatus according to  claim 4 , wherein the intermediate transfer belt has a surface resistivity of 10 10  Ω/□ or more and 10 14  Ω/□ or less and a volume resistivity of 10 8  Ω·cm or more and 10 14  Ω·cm or less.  
     
     
         8 . The image-forming apparatus according to  claim 4 , wherein the intermediate transfer belt contains filler particles having a particle diameter of 0.1 μm or more.  
     
     
         9 . A method for producing a polyimide film, comprising the steps of: 
 forming a polyimide compound having a polyimide as the primary constituent and containing at least a polymeric conductive agent into a film shape; and    exposing to high temperature and humidity the film-shaped polyimide compound formed in the step of forming the polyimide compound wherein the polyimide compound is kept in an environment of a temperature of 27° C. or more and a humidity of 70% or more.    
     
     
         10 . The method for producing a polyimide film according to  claim 9 , wherein the polymeric electroconductive material contains polyaniline and a dopant for making the polyaniline conductive.  
     
     
         11 . The method for producing a polyimide film according to  claim 9 , wherein the rate of the temperature increase is 10° C./min when the polyimide film is heated gradually from 30° C.  
     
     
         12 . A method for producing an endless intermediate transfer belt for use in an image-forming apparatus that forms an image on a recording medium by forming a toner image on an image carrier and transferring and fixing the toner image finally on the recording medium, having an intermediate transfer belt in contact with the image carrier whereon the toner image is formed for receiving the toner image from the image carrier once by application of a bias voltage and transferring the toner image onto the recording medium, comprising the steps of: 
 exposing a film-shaped polyimide compound to high temperature and humidity at a temperature of 27° C. or more and a humidity of 70% RH or more, the film-shaped polyimide compound having a polyimide as the primary constituent, containing at least a polymeric electroconductive material and having a differential thermal characteristic in which a differential thermal curve is created, the differential thermal curve at a temperature of 150° C. or more having a plurality of inflection points corresponding to an intersection between a tangent line passing a point of a change from increase to decrease in the slope of the curve and a tangent line passing a point of a change from decrease to increase in the slope of the curve;    cutting into a long belt the film-shaped polyimide compound after the step of exposure to high temperature and humidity; and    heat-compressing the resultant belt by connecting both ends of the belt cut off in the step of cutting into a long belt with an adhesive and heating and compressing both connected end regions at a temperature in the range of 150° C. or more to the inflection point closest to 150° C. where the slope of the differential thermal curve becomes smaller.    
     
     
         13 . The method for producing an intermediate transfer belt according to  claim 12 , wherein the polymeric electroconductive material contains polyaniline and a dopant for making the polyaniline conductive.