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.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The invention relates to a polyimide film having a polyimide as the primary constituent and containing at least a polymeric electroconductive material, an image-forming apparatus having an intermediate transfer belt made of the polyimide film, a method for producing the polyimide film, and a method for producing the intermediate transfer belt. [0003] 2. Description of the Related Art [0004] Some image-forming apparatuses by electrophotographic process employ an endless intermediate transfer belt (see, e.g., Japanese Patent Application Laid-Open (JP-A) No. 62-206567 ). In the image-forming apparatuses equipped with an intermediate transfer belt, an image is formed by forming an electrostatic latent image on the surface of an image carrier, developing the electrostatic latent image with a toner into a toner image, transferring the toner image on the image carrier once onto the intermediate transfer belt electrostatica...

AI Technical Summary

Benefits of technology

[0011] The present invention has been made in view of the above circumstances and provides a polyimide film containing a polymeric electroconductive material sufficiently higher in conductivity and thus having a stabilized resistivity, an image-forming apparatus having an intermediate transfer belt made of the polyimide film, a method for producing the polyimide film in a period as short as possible, and a method for producing the intermediate transfer belt that provides high-quality transfer images.

[0018] In the image-forming apparatus according to the invention, the surface resistivity and volume resistivity of the intermediate transfer belt are stable even after repeated application of bias voltages and thus allow reliable production of high-quality transfer images.

[0020] The former polyimide film provides high-quality transfer images, while the latter suppresses fluctuation in the length of intermediate transfer belt and provides the intermediate transfer belt with sufficiently high mechanical strength, assuring more stabilized movement of the belt. Each resistivity above is the value as determined when a voltage of 100V is applied.

[0022] By the method for producing a polyimide film according to the invention, the water content of the polyimide film is stabilized in a shorter period of time by the processing in the step of high temperature and humidity exposure, allowing more efficient production of the polyimide film according to the invention.

[0027] By the method for producing an intermediate transfer belt according to the invention, the resistivity of the intermediate transfer belt becomes stabilized in a shorter period of time by the processing in the step of high temperature and humidity exposure, and additionally an intermediate transfer belt superior in dimensional accuracy can be obtained by the processing in the step of thermocompression. That is, if a wet belt is subjected to thermocompression, water in the belt is released, causing shrinkage of the belt in the width direction and waveness on the surface thereof. If the temperature of thermocompression is in the range of 150° C. or more to the inflection point closest to 150° C. where the slope of the differential thermo curve becomes smaller, the heat-compressed belt which is suppressed in the shrinkage in the width direction and surface waveness, returns almost to the original shape by absorbing water in the environment when allowed to cool, allowing the shrunk portion to return to the original shape, and thus can regain its favorable dimensional accuracy, but when the temperature of thermocompression is higher than the temperature above, the belt becomes completely or almost absolutely dry, leaving the shrunk area and the worsened dimensional accuracy as they are.

[0028] The invention provides a polyimide film overcoming the disadvantages described above, i.e., a polyimide film having a polymeric electroconductive material sufficiently higher in conductivity and thus more stabilized in resistivity, an image-forming apparatus having an intermediate transfer belt made of the polyimide film, a method for producing the polyimide film in a period as short as possible, and a method for producing the intermediate transfer belt that provides high-quality transfer images.

Problems solved by technology

However, although the intermediate transfer belt described in Patent Reference 11 containing a dopant for making the polyaniline conductive has extremely consistent volume and surface resistivity during repeated application of bias voltages compared to the intermediate transfer belts described in Patent References 8 to 10 containing a conductive filler or carbon black dispersed therein if the polyaniline is made sufficiently conductive until it reaches a stabilized region, but if the conductivity of the belt is insufficient, the volume resistivity and surface resistivity gradually deteriorate over time regardless of whether the bias voltages are applied repeatedly or not.

Another disadvantage is that it requires an extended period of time to make polyaniline sufficiently conductive.

Yet another disadvantage is that the belt becomes shrunk and deformed by the heat applied when the cut belt is thermally compressed at both ends in production of the intermediate transfer belt, resulting in deterioration in dimensional accuracy and thus could not provide high-quality transfer images reliably.

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