Transfer material-carrying member

Details Transfer material-carrying member Transfer material-carrying member

1999-03-03

2001-05-29

Woodward, Ana (Department: 1711)

Stock material or miscellaneous articles

Structurally defined web or sheet

Discontinuous or differential coating, impregnation or bond

C428S914000, C525S420000, C525S425000

Reexamination Certificate

active

06238775

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to transfer material-carrying members formed from a resin composition, and more particularly to transfer material-carrying members used in image forming apparatus such as copying machines according to an electrophotographic system, printers and facsimiles.
BACKGROUND OF THE INVENTION
In image forming apparatus (electrophotographic copying machine, electrostatic recording apparatus, etc.) such as copying machines according to an electrophotographic system, printers and facsimiles, images are formed through steps such as charging, exposure, development, transfer and fixing. In such an image forming apparatus, a toner image formed on a photosensitive drum through the steps of charging, exposure and development is transferred to a transfer material such as transfer paper or OHP film and then fixed to the transfer material by a means such as heating. In the transfer step of the image forming apparatus, there is used a transfer material-carrying member having the functions of carrying a transfer material, conveying the transfer material to a transfer position and separating the transfer material after transferring a toner image to the transfer material to deliver it to a fixing step.
A dielectric or conductive film has heretofore been used as such a transfer material-carrying member. In many cases, the transfer material-carrying member is formed in the form of a drum or endless belt. It is very important that a material used for the transfer material-carrying member should be a material capable of controlling the electrical characteristics of the transfer material-carrying member within preferred ranges. At the same time, it is also necessary for such a material to have excellent mechanical characteristics, because the transfer material-carrying member is required to play a role as a mechanical structure.
A resin material comprising a polycarbonate resin as a main component has been proposed as a resin material for transfer material-carrying members (Japanese Patent Application Laid-Open No. 311472/1995). In this technical field, besides this material, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, fluorocarbon resins such as polyvinylidene fluoride, and the like are used as resin materials. However, these resin materials have both merits and demerits and do not fully satisfy high electrical characteristics and mechanical physical properties required of the transfer material-carrying members.
For example, a transfer material-carrying member formed from a polycarbonate resin exhibits far excellent fatigue endurance, but is not sufficient in electrical characteristics such as dielectric constant and also insufficient in tensile elongation at break. More specifically, the polycarbonate resin is excellent in stiffness or rigidity, but, on the other hand, it has high brittleness. Therefore, the transfer material-carrying member formed from the polycarbonate resin tends to cause brittle fracture when it passes the mechanical endurance limit. This suggests the possibility that the polycarbonate resin may be lacking in the reliability as a mechanical part. In order to provide a transfer material-carrying member as a high-performance member, it is desirable that the member should have good stiffness and cause ductile fracture. However, the resin material comprising the polycarbonate resin as a main component is not sufficient in these characteristics.
In addition, the polycarbonate resin has a low dielectric constant. Polyester resins also have not a very high dielectric constant. Charging and discharging are repeated on a transfer material-carrying member upon use. If the dielectric constant of the transfer material-carrying member is low, it is necessary to make applied voltage higher. More specifically, a charge level upon charging operation is represented by the equation (1):
Q=CV  (1)
wherein Q is charge, C is capacitance, and V is applied voltage. If C (&agr; &egr;: dielectric constant) is small, it is necessary to make V higher in order to obtain a fixed Q. In order to make V higher, it is necessary to make an electric power unit larger. Therefore, the apparatus cost is increased as a whole. When high voltage is applied, discharge toward peripheral metal members and the like tends to occur, and so the necessity of taking insulation measure arises.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide a transfer material-carrying member which has excellent mechanical fatigue endurance, tensile elongation at break, mechanical endurance, stiffness and the like and a high specific dielectric constant and makes it possible to lower voltage required upon repeated charging and discharging.
The present inventors have carried out an extensive investigation with a view toward overcoming the above-described problems involved in the prior art. As a result, it has been found that a transfer material-carrying member exhibiting excellent mechanical physical properties and electrical characteristics can be obtained from a resin composition comprising a polyester resin containing ethylene terephthalate as a predominant repeating unit and having a specific reduced viscosity, and a polyamide resin and/or a polycarbonate resin in specifically selected compositional proportions. The present invention has been led to completion on the basis of this finding.
According to the present invention, there is thus provided a transfer material-carrying member formed from a resin composition comprising at least two resins selected from the group consisting of (A) a polyester resin containing a predominant repeating unit composed of ethylene terephthalate and having a reduced viscosity of at least 0.9 dl/g, (B) a polyamide resin, and (C) a polycarbonate resin, wherein the compositional proportions by mass % of the respective resins are included within a range of a pentagon having points (98, 2, 0), (85, 15, 0), (65, 15, 20), (72, 0, 28) and (90, 0, 10) as vertexes when represented by a triangular coordinate indicated in the above order (A, B, C).


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patent: 5302574 (1994-04-01), Lawrence et al.
patent: 5340884 (1994-08-01), Mills et al.
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patent: 5650469 (1997-07-01), Long et al.
patent: 0 767 414 A1 (1997-04-01), None
patent: 06149083 (1994-05-01), None
patent: 7-311472 (1995-11-01), None

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