Photoreceptor drum with specified flange

A photoreceptor drum having flanges at the ends of a cylindrical substrate is disclosed. The flange contains a heat-resistant thermoplastic resin and a compound comprising a metal selected from a group consisting of Sb, Sn, Pb, Ge, Ga and Zn.

FIELD OF THE INVENTION 
The present invention relates to a photoreceptor drum used for an 
electrophotographic copying machine, an electrophotographic-printer and 
facsimile. 
Heretofore, a photoconductive layer is provided on a cylindrical electric 
conductive substrate of a photoreceptor drum for forming a photoreceptor. 
As well, to an aperture on both ends of the electric conductive substrate, 
a metallic flange such as aluminum or an insulating flange such as plastic 
are engaged. 
The above-mentioned photoreceptor drum has been rotatably supported on a 
rotation shaft which extends from the main body of a copying machine 
through the above-mentioned shaft hole of the flange so that images are 
formed during rotation of the photoreceptor drum by means of a driving 
source. During the image formation, grounding of the above-mentioned 
photoreceptor drum is necessary. 
When an insulating flange is employed, it is known that an elastic 
grounding plate which is brought into pressure contact with an electric 
conductive substrate of the above-mentioned photoreceptor drum and a 
rotation shaft which extends from the main body of the above-mentioned 
copying machine is provided inside the flange to be grounded. 
However, according to a grounding method employing the above-mentioned 
elastic grounding plate, a structure can become complicated. In addition, 
an grounding plate may be abraded and deformed to lose electrical 
conductivity. As a result, there is a shortcoming that it lacks in 
reliability. In addition, according to a method of grounding by the use of 
a metallic flange, a special bearing is provided on an shaft hole as 
described above. In this method, processing cost is expensive and the 
weight of the flange becomes excessively large. 
Japanese Utility Publication Open to Public Inspection Nos. 59-153568 and 
61-182565 and Japanese Patent Publication Open to Public Inspection 
(hereinafter, referred to as Japanese Patent O.P.I. Publication) No. 
61-100764 disclose a flange for a photoreceptor drum employing an electric 
conductive resin in which a agent giving conductivity such as carbon 
black, graphite, carbon filler and metallic powder, polyethylene, 
polypropylene, polyvinyl chloride, polyethylene, an ABS resin nylon, 
polycarbonate, polybutyleneterephthalate and polyethylene fluoride are 
caused to be dispersed and incorporated in a resin. In addition, Japanese 
Patent O.P.I. Publication discloses a technology to use a material in 
which a furnace carbon and carbon filler are dispersed and incorporated in 
an fire-retardant thermo-plastic resin for a flange member. 
SUMMARY OF THE INVENTION 
In the case of technologies described in each of the above-mentioned 
specifications, it is impossible to provide slide-contacting property, 
grounding property and fire-retarding property which are currently 
demanded. Specifically, it has been difficult to provide durability which 
can maintain sure slide-contacting property and grounding property after 
using for a long period. 
Objects of the present invention are, practically, to provide a flange 
employing an electric conductive resin capable of providing sure 
slide-contacting property and grounding performance after using for a long 
period extremely and also provide sufficient fire-retarding property. Due 
to this, grounding of a photoreceptor drum can sufficiently be conducted. 
In addition, a photoreceptor drum in which a flange excellent in 
mechanical strength wherein abrasion with a rotation shaft and damage do 
not occur and, accordingly, noise during operation time and defective 
image do not occur is integral. 
The photoreceptor drum and its embodiment are described. 
The photoreceptor drum comprises flanges provided at ends of a cylindrical 
electric conductive substrate having a photoconductive layer. The flange 
contains a heat-resistant thermo-plastic resin and a compound comprising a 
metal selected from a group consisting of Sb, Sn, Pb, Ge, Ga and Zn. 
The flange preferably comprises a flange shaft bearing member. 
The flange preferably contains a carbon filler. 
The flange contains a polyester elastomer as a raw material. 
The preferable example of the metal of the compound comprising a metal is 
Sb. 
The preferable example of the compound comprising a metal is oxide compound 
containing antimony, and preferable example is antimony pentaoxide. 
The preferable example of the heat-resistant thermo-plastic resin is a 
polycarbonate, a polyethylene terephthalate, a polybutylene terephthalate 
or an ABS, and more preferably a polybutylene terephthalate. 
The carbon filler has preferably 10 m.sup.2 /g or more in terms of BET 
specific surface area. 
The flange preferably contains a fire retardant. 
The preferable embodiment of the flange contains a heat-resistant 
thermo-plastic resin at 55 to 80 parts by weight and the compound 
comprising a metal selected from a group consisting of Sb, Sn, Pb, Ge, Ga 
and Zn at 2 to 15 parts by weight, the polyesterelastomer at 2 to 8 parts 
by weight, the carbon filler at 4 to 20 parts by weight and the fire 
retardant at 3 to 20 parts by weight. 
The preferable example of the fire retardant is a bromine-containing 
fire-retardant. 
The preferable example of the bromine-containing fire retardant is a 
teterabromocyclododecane, a bistribromophenoxyethane, a tribromophenol, an 
ethylenebistetra bromophthalimide, a polydibromophenylene oxide, a 
pentabromobenzeylpolyacrylate or a tetrabromophathalic acid. 
The preferable embodiment of drum comprises flanges provided at ends of a 
cylindrical electric conductive substrate having a photoconductive layer, 
wherein the flange contains a heat-resistant thermo-plastic resin and a 
polyester elastomer, carbon black, antimony pentaoxide and a 
bromine-containing fire-retardant in the resin. 
The image forming apparatus comprises a photoreceptor drum in which flanges 
are provided at ends of a cylindrical electric conductive substrate having 
a photoconductive layer, wherein the flange is formed by containing a 
heat-resistant thermo-plastic resin and a polyester elastomer, carbon 
black, antimony pentaoxide and a bromine-containing fire-retardant in the 
resin.

DETAILED DESCRIPTION OF THE INVENTION 
The photoreceptor drum of the present invention is a photoreceptor drum in 
which a flange is mounted at the ends of a cylindrical electric conductive 
substrate having a photoconductive layer. The flange contains a 
heat-resistant thermo-plastic resin and a compound comprising a metal 
selected from a group consisting of Sb, Sn, Pb, Ge, Ga and Zn. On a 
cylindrical electric conductive substrate, for example aluminum, an 
inorganic or organic photoconductive layer is provided. At the cylindrical 
aperture at both sides of the above-mentioned electric conductive 
substrate, the flange containing a heat-resistant thermoplastic resin and 
a compound comprising a metal selected from a group consisting of Sb, Sn, 
Pb, Ge, Ga and Zn, a flange containing a polyester elastomer, carbon 
black, antimony pentaoxide and a bromine-containing fire-retardant in a 
heat resistant thermo-plastic resin is mounted. When a flange bearing 
member is an independently existing member, it contains both of a flange 
as a part of a flange and a flange bearing member integrally molded and 
processed. 
The photoreceptor drum is rotatably supported by a fixed rotation shaft 
extended from main body of a copying machine through an shaft hole of a 
flange on the above-mentioned both ends. The photoreceptor drum is 
rotatably driven by a driving source through a gears for transmitting 
provided on one of a flanges and plural reducing gears combined for 
engaging with the gears for transmission. In this occasion, grounding of a 
photoreceptor drum is conducted via main body of the copying machine 
through a rotating shaft penetrating an shaft hole of the flange. 
During operation, a photoreceptor drum occurs abrasion of both of a 
rotation shaft and damage and thereby causes noise due to slide-contacting 
between an shaft hole of a flange and a rotation shaft penetrated to the 
shaft hole (it is referred to as "squealing of flanges"). Therefore, in 
the gap between a rotation shaft and an shaft hole of a flange, conductive 
grease is used for the sure slide-contacting. After use for a long period, 
toner splashed invades, clogging the conductive grease, resulting in poor 
slide-contacting and grounding problem and causing defective image such as 
step unevenness and fogging. 
The present invention provides sufficient mechanical strength and 
slide-contacting property. Thereby, use of the conductive grease used for 
minimizing the occurrence of noise can be abolished. Heretofore, it was 
found that flange squealing which used to occurs at about 1,000 copies 
without the use of the conductive grease does not occur until at least of 
after copying 200,000 copies. 
The wiring of a flange employing a conventional electric conductive resin 
can short out in any of various mechanical problems located around a 
photoreceptor drum, and a flange may be scorched due to excess current 
which passes the photoreceptor drum so that the flange is inflamed to 
cause problems. 
However, the flange of the present invention satisfies mechanical strength 
and dimension stability during injection molding. Simultaneously with 
this, standard of UL94 for fire-resistance grade VO can also be satisfied. 
Standard of UL94 for fire-resistance grade VO shows to have a 
self-extinguishing property. 
During operation, a photoreceptor drum is grounded to a copying machine 
main body through an shaft hole of a flange and a rotation shaft 
penetrated to the shaft hole. In order to sufficient conductivity of the 
flange, selection of a conductive agent and its content are important 
issues. Further, the content of agent giving conductivity is related to 
mechanical strength and anti-abrasion property, and therefore, the 
selection of the kind of an agent giving conductivity and its amount which 
do not damage the mechanical strength of the flange becomes an important 
issues. 
According to the invention the flange excellent in mechanical strength and 
fire-resisting property in which grounding of a photoreceptor drum can 
sufficiently be conducted, abrasion with a rotation shaft and damage 
thereby do not occur and, therefore, no noise during operation and 
defective image occur was developed, and a photoreceptor drum in which the 
flange is integral could be provided. 
When a metallic flange is used, the photoreceptor drum is grounded due to 
contact between the above-mentioned rotation shaft and a flange shaft hole 
or bearing such as brass provided in the shaft hole. Therefore, the 
above-mentioned grounding plate must be unnecessary. However, actually, at 
a portion at which a rotation shaft and a flange shaft hole or a bearing 
provided in the shaft hole, in order to improve slide-contacting property, 
a bearing is used. To there, a lubricant oil such as grease is also used. 
In order for these to improve their grounding property, conductive ones 
may be used. Though conductive ones are used, splashed toner is mixed 
during use for a long period. As a result, coagulation or defective 
conductivity occur so that properties as of the present invention cannot 
be obtained. 
As the heat-resistant thermo-plastic resin for the flange, resins excellent 
in heat resistance and slide-contacting property such as polycarbonate, 
polyethylene terephthalate, polypropylene terephthalate, polybutylene 
terephthalate and ABS resin are preferable. Specifically, the 
above-mentioned polybutylene terephthalate is favorable. These resins may 
contain copolymer component. In this instance the component of the 
heat-resistant thermo-plastic resin is preferably more than 30 mol %, more 
preferably 50 mol %, and further, 80 mmol %. 
In the resin the compound containing a metal of Sb, Sn, Pb, Ge, Ga or Zn. 
Preferable example of the compound is an oxide of the metal. Preferable 
example of the metal is Sb. The preferable example of the compound is 
TiO.sub.2, SnO.sub.2, Sb.sub.2 O.sub.5, Sb.sub.2 O.sub.3 and ZnO. The most 
preferable example of the compound is antimony pentaoxide. The preferable 
amount of the compound is 2 to 15 parts by weight, more preferably 5 to 8 
parts by weight, of the flange. 
The flange preferably formed by containing a polyester elastomer. The 
preferable amount of the polyester elastomer is 2 to 8 parts by weight and 
more preferably 4 to 6 parts by weights, of the flange. The polyester 
elastomer has a polyester as a hard segment in a molecule and a polyether 
having low glass transition temperature (Tg) as a soft segment or a 
multi-block copolymer employing a polyester. Typically, there are the 
following two types. 
(1) Polyester.cndot.polyether type 
Hard segment: Aromatic group type crystalline polyester 
Soft segment: Polyether 
For example, there are those having the following structures: 
##STR1## 
In the formulas m is about 5 to 25, n is about 2 to 4. (2) 
Polyester.cndot.polyester type 
Hard segment: Aromatic group type crystalline polyester 
Soft segment: Aliphatic group polyester 
For example, there are those having the following structures: 
##STR2## 
provided that A and B are chain-lengthening agents (low molecular diol, 
for example, diol having 1 to 6 carbon atoms). In the formulas m is about 
5 to 25, n is about 2 to 4. 
Commercially available examples of the above-mentioned compounds include 
Pelprene (produced by Toyo Boseki Co., Ltd.), Hi-trel (Toray and Du Pont), 
Grilux E (Aquzo Inc.) and D-Mod (General Electric Inc.). 
It is preferable that the flange contains carbon filler. It is also 
preferable that the carbon filler has 10 m.sup.2 /g or more interms of BET 
specific surface area, more preferably 300 m.sup.2 /g or more, and 
particular preferably 700 m.sup.2 /g or more and usually up to 1200 700 
m.sup.2 /g. The carbon filler is preferably used in an amount of 4 to 20 
parts by weight and more preferably 7 to 10 parts by weight, of the 
frange. A preferable example of the carbon filler is carbon black. Average 
particle size of the carbon black is 1 .mu.m to 1 .mu.m. As the carbon 
black for the flange, furnace black is preferably used. This furnace black 
is manufactured by a special method in which oil is blown in a furnace, 
and flamed continuously. In the flammation, water is sprayed for cooling 
and collecting. For this reason, this furnace carbon black is excellent in 
terms of conductivity compared with conventional carbon black. Its 
particles are porous having a large specific surface area and is excellent 
in terms of dispersion property into a resin. 
As a commercially available product of a furnace black, for example, 
Kottigen black EC (BET specific surface area is 800 m.sup.2 /g) and 
Kottigen black EC600JD (BET specific surface area is 1270 m.sup.2 /g) 
produced by International Inc., Conductex 40-220 (BET specific surface 
area is 1066 m.sup.2 /g) produced by Colombian Inc. and Printex XE-2 (BET 
specific surface area is 1000 m.sup.2 /g) produced by Degsa Inc. All of 
them are porous having a large specific surface area of carbon particles. 
The particle specific surface area of furnace black preferably used is, in 
terms of BET specific surface area, preferable 700 m.sup.2 /g or more and 
more preferably 800 m.sup.2 /g or more. 
It is preferable that the flange contains fire-retardant. The 
fire-retardant is preferably used in an amount of 3 to 20 parts by weight 
and more preferably 10 to 15 parts by weight, of the flange. The 
fire-retardant includes bromine-containing fire-retardant such as 
tetrabromocyclododecane, bistribromophenoxyethane, tribromophenol, 
ethylenebistetrabromophthalimide, polydibromophenyleneoxide, 
pentabromobenzylpolyacrylate and tetrabromophthalic acid; 
phosphor-containing fire-retardant such as phosphoric ester 
fire-retardant, halogen-contaninging phosphoric ester fire-retardant and 
polyphosphoric acid fire-retardant; chlorine-containing fire-retardant 
such as perchlorocyclopentadecane and tetrachlorophthalic acid anhydride; 
inorganic fire-retardant such as aluminum hydroxide and magnesium oxide. 
Among the fire-retardant the bromine-containing fire-retardant is 
preferably used. Two or more thereof may be used in combination. 
The flange is a flange capable of withstanding abrasion due to friction 
between the shaft hole and the rotation shaft of the above-mentioned 
flange. In order to attain the objects of the above-mentioned present 
invention more preferably, the above-mentioned flange section or at least 
a flange shaft bearing member contains a heat-resistant thermoplastic 
resin such as polybutylene terephthalate at 55-80 parts (hereinafter, 
unless not specifically cited, "part" represents "part by weight") and 
preferably 65-70 parts, a polyester elastomer at 2-8 parts and preferably 
4-6 parts, furnace carbon black at 4-20 parts and preferably 7-10 parts, 
antimony pentaoxide at 2-15 parts and preferably 5-8 parts and a 
bromine-containing fire-retardant at 3-20 and preferably 10-15 parts. 
Volume resistance ratio of the flange is preferably less than 10.sup.2 
.OMEGA..multidot.m to obtain sufficient grounding function of the flange 
and good image formation performance. 
These raw materials are mixed by kneading and then the kneaded composition 
is molded by injection to prepare the flange. 
FIG. 1 is a cross sectional view showing a photoreceptor drum and a driving 
mechanism which rotates and drives a photoreceptor drum of the present 
example. In FIG. 1, photoconductive layer 3 is provided on cylindrical 
electric conductive substrate 2 in a photoreceptor drum. At the aperture 
portion of both ends of the above-mentioned electric conductive substrate 
2, flanges 4 and 5 employing an electric conductive resin of the present 
invention are engaged with. 
The above-mentioned photoreceptor drum 11 is rotatably supported by 
engaging flanges 4 and 5 and shaft holes 6 and 7 on rotation shaft 8 and 9 
which is fixed to the side plates 10 and 11 on the main body of the 
copying machine. The above-mentioned photoreceptor drum 1 is rotatably 
driven by motor M through gear G1 for transmitting and gear for reducing 
gears G2, G3, G4, G5 and G6. 
On the above-mentioned photoreceptor drum, image formation is conducted 
under rotation by the driving source. For forming the image formation, 
grounding of a photoreceptor is essential. If an insulating flange is 
used, a method to ground by providing an elastic grounding plate which is 
brought into contact with an electric conductive substrate of a 
photoreceptor drum and a rotation shaft which extends from the main body 
of a copying machine inside the flanges is known. 
On the other hand, if a metallic flange is used, theoretically, the 
above-mentioned grounding plate becomes unnecessary. the rotation shaft 
and the flange shaft hole are grounded through a bearing such as brass 
provided on the shaft hole. 
However, according to a grounding method employing the above-mentioned 
elastic grounding plate, a structure becomes complicated. In addition, an 
grounding plate may be abraded and deformed to lose electrical 
conductivity. As a result, there is a shortcoming that it lacks in 
reliability. In addition, according to a method of grounding by the use of 
a metallic flange, a special bearing is provided on an shaft hole as 
described above. By this method, processing cost is expensive and the 
weight of the flange becomes large. In addition, though theoretically, a 
grounding plate is unnecessary, the grounding plate must be provided as a 
countermeasure for defective conductivity caused by coagulation of 
conductivity grease by splashing toner as described above. 
As a countermeasure for the above-mentioned problems, a flange employing an 
electric conductive resin is known. However, mechanical strength and 
slide-contacting property tends to be lacking. Specifically, after using 
for a long period, maintaining durability) of performances becomes 
problematic. As described over and over again, due to coating of a 
conductive grease onto a shaft hole section, friction and damage are 
minimized, which absorbs splashed toner and dust, causing sticking. 
Defective grounding and insufficient rotation are caused. The present 
invention solves the above-mentioned problems completely. 
FIG. 2 shows schematic view of FIG. 1. Due to this, an embodiment of the 
present invention will be explained. 
FIG. 2(a) shows a conventional type, in which flange 4 is made of an 
electric conductive material such as an electric conductive resin or 
aluminum. Numeral 8 represents a rotation shaft, numeral 12 represents an 
grounding plate which is fixed to the flange with screw 13. 
The grounding material is made of a phosphoric bronze. It is abraded due to 
friction with a rotation shaft, tending to cause defective grounding. In 
addition, it is necessary to maintain with a screw and to process for 
folding. Therefore, it becomes expensive in terms of cost. 
On the contrary, FIG. 2(b) is an embodiment of the present invention. By 
employing the materials of the present invention for flanges, at least 
bearing member 14 for the flanges (in this occasion, members different 
from the flange are illustrated), a lubricant such as a grease is not 
necessary. Grounding becomes sure. In addition, it is easy to manufacture. 
Therefore, it is profitable in terms of cost. 
EXAMPLES 
Hereinafter, the present invention will be explained in detail referring to 
examples. 
A photoreceptor drum is prepared in the following manner. Based on an 
aluminum-withdrawn tube, the surface roughness of an aluminum drum whose 
outer diameter was 80 mm and the length was 355 mm was arranged to be 0.3 
.mu.m by the use of a diamond bit. After the aluminum drum was cleaned 
sufficiently, a subbing layer was formed by means of a dipping method. On 
the subbing layer, a photoconductive layer in which a charge generation 
layer and a charge transport layer were successively laminated was formed 
for obtaining a photoreceptor for the present example. 
The structure of a flange engaged with the photoreceptor was changed so 
that 9 kinds of flange were prepared and engaged with the above-mentioned 
photoreceptor. Thus, photoreceptor drum examples 1 through 8 and 
comparative photoreceptor drum 1 for the comparison were obtained. 
Each of the above-mentioned photoreceptor was loaded in Konica U-BIX 4155 
(produced by Konica Corporation), and subjected to an actual copying test 
up to 300,000 copies. 
In Table 1, each characteristic was displayed under the following 
requirements. 
1. Specific Volume Resistance 
For evaluation of conductivity, the specific volume resistance was measured 
by means of a Rhorester AP MCP400 (manufactured by Mitsubishi Yuka Co., 
Ltd.). The following was defined to be the requirement for evaluation. 
A: less than 10.sup.2 .OMEGA..multidot.cm 
B: 10.sup.2 .OMEGA..multidot.cm or more 
2. Molding property 
Conditions when molding a flanges and flanges after being processed were 
visually observed. They were evaluated generally, and evaluated under the 
following requirements. 
A: No problem 
B: There was at least one problem in either issues. 
3. Image quality 
Initial image quality was evaluated in terms of fogging of an actual copied 
image, maximum density and image uneven step. 
Durability was evaluated in terms of that to what extent the 
above-mentioned characteristics can be maintained, and evaluated under the 
following requirements. 
A: Image quality was favorable up to 300,000 copies 
A': Defective image occurred before 100,000 copies 
B: Defective image occurred before 20,000 copies 
4. Fire-retardant 
In accordance with standard UL94, the following evaluation was conducted: 
A: The flange reaches grade VO. 
B: The flange does not reach grade VO. 
5. Abnormal noise 
A: No abnormal noise occurred up to 300,000 copies. 
B: Abnormal noise occurred before 300,000 copies has been finished. 
TABLE 1 
__________________________________________________________________________ 
Bromine- 
Specific Image 
Image 
Fire- 
Photo- Penta- 
containing 
volume quality 
quality 
retar- 
receptor Elas- 
antimony 
fire- 
re- Molding 
(Ini- 
(Dura- 
dant 
Abnormal 
drum Resin 
C.B. 
tomer 
oxide 
resistant 
sistance 
property 
tially) 
bility) 
property 
noise 
__________________________________________________________________________ 
1 70 4 8 15 3 A A A A A A 
2 67 8 5 7 13 A A A A A A 
3 64 18 2 7 10 A A A A A A 
4 62 4 6 10 18 A A A A A A 
5 66 8 4 15 5 A A A A A A 
6 59 18 8 6 9 A A A A A A 
7 47 25 0 15 13 A A A A' A A 
8 73 2 5 7 0 A A A A B A 
Compara- 
84 15 1 0 3 A A A B B B 
tive 1 
__________________________________________________________________________ 
Resin: Polybutylene terephthalate 
Elastomer: For photoreceptor drums 1 through 3, 7 and 8 of the Example and 
for photoreceptor drums 1 of the Comparative example, a polyester 
polyether type was employed. For photoreceptor drums 4 through 6, a 
polyester polyester type was employed. 
Bromine-containing fire-retardant: tetrabromocyclododecane 
As apparent from the results of Table 1, though samples 1 to 6 have no 
problems in all properties, comparative samples 1 have some properties in 
some properties so that it can be understood that they do not reach the 
targeted level of the present invention. 
As is apparent from the above explanation, according to the photoreceptor 
drum of the present invention, durability in which sure slide-contacting 
property and grounding property (grounding) can be assured even after 
using for a long period can be provided. 
Owing to the present invention, grounding of the photoreceptor drum can 
sufficiently be conducted, and a photoreceptor drum excellent in 
mechanical strength in which abrasion with a rotation shaft and damage do 
not occurred an improved flange having no occurrence of noise during 
operation time and defective image are integral can be provided.