Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
1999-12-21
2001-08-28
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S353000, C428S036920, C428S220000, C428S332000, C428S473500
Reexamination Certificate
active
06281324
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a semiconductive belt being excellent in environmental stability of electric characteristics and durability, which can be preferably used in an electronic photographic recording apparatus as an intermediate transfer belt to transfer an image to a recording sheet or a transfer conveyance belt to both transfer an image on an image carrier to a recording sheet provided on the belt and convey the recording sheet having the image transferred.
BACKGROUND OF THE INVENTION
In order to elongate the lifetime of apparatuses arranged to form and record an image according to the electro-photographic method such as copying machines, laser printers, video printers, facsimile machines and their composite systems, a method in which the image on an image carrier is temporarily transferred to an intermediate transfer belt, and the transferred image is then fixed on a recording sheet has been investigated as an alternative to a method in which an image, composed of a recording material such as toner, formed on an image carrier such as a photosensitive drum is directly fixed to a recording sheet. Furthermore, a transfer method in which the recording sheet, on which the image is transferred, is conveyed has been investigated.
Hitherto, a semiconductive belt which can be used as the intermediate transfer belt is composed of a polyimide film containing an electrically conductive filler to have a volume resistivity of 1
13
&OHgr;cm to 10
13
&OHgr;cm as described in JP-A-5-77252 (the term “JP-A” as used herein means unexamined Japanese patent publication). The use of the polyimide film overcome problems of conventional semiconductive belts (JP-A-5-200904, JP-A-5-345368 and JP-A-6-95521) composed of a film made of vinylidene fluoride, ethylene-tetrafluoroethylene copolymer or polycarbonate, i.e., occurrence of a crack etc. at the end of the belt due to insufficient mechanical characteristics (e.g., strength and wear and abrasion resistance) and deformation of the transferred image caused by a load applied at driving.
However, the conventional semiconductive belts comprising the polyimide film are practically unsatisfactory in the environmental stability of the electric characteristics and durability. That is, the electric characteristics such as surface resistivity undesirably vary depending on external environment such as temperature and humidity. Furthermore, the electric characteristics largely vary with the long-term use. When the conventional semiconductive belt is used as the intermediate transfer belt or the transfer conveyance belt, there are problems such as transfer unevenness of the toner image transferred and developed on the recording sheet or separation failure of the recording sheet having an image transferred from the belt.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a semiconductive belt which has excellent mechanical characteristics such as strength attributable to a polyimide film, is excellent environmental stability of electric characteristics such as surface resistivity so that electric characteristics hardly vary depending on external environment, enables transfer of a good image onto a recording sheet free from deformation of a toner image and transfer unevenness, and good separation of the recording sheet being conveyed, even when it is used as an intermediate transfer belt or a transfer conveyance belt of an electrophotographic recording apparatus, and retains such characteristics for a long time.
According to one aspect of the present invention, there is provided a semiconductive belt comprising a polyimide film having a volume resistivity of 10
9
&OHgr;cm to 10
6
&OHgr;cm and a surface resistivity of 10
10
&OHgr; to 10
17
&OHgr; at 25° C. and 60% RH (relative humidity), wherein the amount of change of the surface resistivity between 30° C. and 85% RH and 10° C. and 15% RH in terms of common logarithm is 1.0 or smaller.
According to the present invention, a semiconductive belt can be obtained which has excellent mechanical characteristics attributable to the polyimide film such as strength and non-elongation characteristic, is excellent environmental stability of electric characteristics such as surface resistivity so that electric characteristics hardly vary depending on external environment, enables transfer of a good image onto a recording sheet free from deformation of a toner image and transfer unevenness, and good separation of the recording sheet being conveyed, even when it is used as an intermediate transfer belt or a transfer conveyance belt of an electrophotographic recording apparatus, and retains such characteristics for a long time.
Other objects of the invention will be apparent from the following detailed descriptions.
DETAILED DESCRIPTION OF THE INVENTION
A semiconductive belt according to the present invention comprises a polyimide film having a volume resistivity of 10
9
&OHgr;cm to 10
16
&OHgr;cm and a surface resistivity of 10
10
&OHgr; to 10
17
&OHgr; at 25° C. and 60% RH, wherein the amount of change of the surf ace resistivity between 30° C. and 85% RH and 10° C. and 15% RH in terms of common logarithm is 1.0 or smaller.
The polyimide film can be formed, for example, by a method which comprises developing a solution of polyamic acid prepared by polymerizing tetracarboxylic dianhydride or its derivative and diamine in a solvent by a proper developing method, drying the developed layer to obtain a film-like molding, and heating the molding to convert polyamic acid into imide.
Tetracarboxylic dianhydride and diamine for preparing polyamic acid can be selected arbitrarily.
Examples of tetracarboxylic dianhydride include a compound represented by the following general formula:
where R is a tetravalent aromatic group, aliphatic group, cyclic aliphatic group or a composite group of these groups, which may have substituent(s).
Examples of tetracarboxylic dianhydride include pyromellitic dianhydride (PMDA), 3,3′,4,4′-benzophenone tetracarboxylic dianhydride, 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (BPDA), 2,3,3′,4′-biphenyl teteracarboxylic dianhydride, 2,3,6,7-naphthalene teteracarboxylic dianhydride and 1,2,5,6-naphthalene teteracarboxylic dianhydride.
Examples of tetracarboxylic dianhydride further include 1,5,8-napthalene tetracarboxylic dianhydride, 2,2′-bis (3,4-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, perylene-3,4,9,10-tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride and ethylene tetracarboxylic dianhydride.
Examples of the diamine include 4,4′-diaminodiphenyl ether (DDE), 3,3′-diaminodiphenylether, 4,4′-diaminediphenyl methane, 3,3′-diaminodiphenyl methane, 3,3-dichlorobenzidine, 4,4′-aminodiphenyl sulfide, 3,3′-diaminediphenyl sulfone, 1,5-diaminonaphthalene, m-pheylene diamine, p-phenylene diamine (PDA), 3,3′-dimethyl-4,4′-diaminobiphenyl and benzidine;
3,3′-dimethylbenzidine, 3,3′-dimethoxybenzidine, 4,4′-diaminephenyl sulfone, 4,4′-diaminodiphenyl sulfide, 4,4′-diaminodiphenyl sulfone, 2,4-bis (&bgr;-amino-t-butyl) tolene, bis (p-&bgr;-amino-t-butylphenyl) ether, bis (p-&bgr;-methyl-&dgr;-aminophenyl) benzene, bis-p-(1,1-dimethyl-5-amiopentyl)benzene, 1-isopropyl-2,4-m-phenylene diamine, m-xylylene diamine and p-xylylene diamine;
diamine include di (p-aminocyclohexyl) methane, hexmethylene diamine, hepthamethylene diamine, octmethylene diamine, nonamethylene diamine, decamethylene diarmine, diaminopropyltetramethylene diamine, 3-metylheptamethylene diamine, 4,4-dimethyheptamethylene diamine, 2,11-diaminododecane, 1,2-bis-(3-aminopropoxy) ethne, 2,2-dimethylpropylene diamine, 3-metoxyhexamethylene diamine, 2,5-dimethylhexamethylene diamine, 2,5-dimethylheptamethylene diamine; and
3-methylheptamethylene diamine, 5-methylnonamethylene diamine, 2,17-diaminoeicosadecane, 1,4-diaminocyclohexane, 1,10-diamino-1,10-dimethyldecane, 1,12-diamino-octdecane, 2,2
Iwamoto Toshiaki
Nakamura Masao
Nakazono Junichi
Sugimoto Masakazu
Tomita Toshihiko
Hampton-Hightower P.
Nitto Denko Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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