US 3769010 A
An electrophotographic photosensitive member is composed of a base, a photoconductor layer and an insulating layer laminated in this order, and additionally a rectifying layer is provided between the base and the photoconductor layer.
Description (OCR text may contain errors)
United States Patent [1 1 Hanada et al.
ELECTROPHOTOGRAPHIC PHOTOSENSITIVE MEMBER inventors: Hiroshi Hanada, Yokohama; Nobuo Kitajima; Tatsuo Masaki, both of Tokyo, all of Japan Canon Kabushiki Kaisha, Tokyo, Japan Filed: June 15, 1971 Appl. No.: 153,354
Foreign Application Priority Data June 20, 1970 Japan 45/53956 us. 01. 96/1.5, 96/] R, 852/501,
75/134 11, 29/195, 29/197, 29/199, 29/194 1m. (:1 G03g 5/04 Field 61 Search 96/1, 15; 252/501 References Cited Primary Examiner-Roland E. Martin, Jr. Attorney-Raymond J. McElhannon et a1.
[5 7 ABSTRACT An electrophotographic photosensitive member is composed of a base, a photoconductor layer and an insulating layer laminated in this order, and additionally a rectifying layer is provided between the base and the photoconductor layer.
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ELECTROPHOTOGRAPHIC PI-IOTOSENSITIVE MEMBER BACKGROUND OF THE INVENTION This invention relates to an electrophotographic photosensitive member, and more particularly to improvements in an electrophotographic photosensitive member fundamentally composed of base, photoconductive layer and insulating layer.
Heretofore, there have been known various inventions of electrophotographic photosensitive member of such three layer structure, but most of them are directed to improvement in stable retention of electric charge on the photosensitive member. Any useful method for injecting sufficiently photocarriers has not been disclosed.
SUMMARY OF THE INVENTION The present invention relates to a photosensitive member comprising a base, a photoconductive layer, an insulating layer, and a rectifying layer being provided between the base and the photoconductor layer.
An object of this invention is to provide an improved photosensitive member comprising three layers.
Another object of this invention is to provide a photosensitive member capable of retaining stably the charge.
A further object of this invention isto provide a photosensitive member to which a sufficient photocarrier can be injected.
Still another object of thisinvention is to provide a photosensitive member'capable of forming an excellent electrostatic image.
A still further object of this invention is to provide a process for producing these photosensitive members.
BRIEF DESCRIPTION OF THE DRAWING FIG. 1 illustrates an enlarged cross-section view of an embodiment of electrophotographic photosensitive member according to the present invention;
FIG. 2 is a graph showing charging characteristics of a photoconductor layer according to the present invention; 7 I
FIG. 3 is a graph showing charging characteristics of a rectifying layer according to the presentinvention;
FIG. 4 is a graph showing charging characteristicsof a photosensitive member according to the present invention;
FIG. 5 is a graph showing the comparison between the photosensitive member according to the present invention and the prior art with respect to decay of charge in cases of exposure and dark discharging;
FIG. 6(A) and (B) show charging states of a photoconductor layer and a photosensitive layer according to this invention, respectively.
DESCRIPTION OF THE PREFERRED EMBODIMENTS A representative electrophotographic process em ploying a photosensitive member composed of a base,
a photoconductive layer and an insulating layer is a process comprising primary charging, secondary charging simultaneously with exposure and blanket irradiation such as electrophotographic processes disclosed in U.S. Ser. No. 563,899, filed July 8, 1966 and U.S. Ser.
No. 571,538, filed Aug. 10, 1966, now abandoned.
According to such electrophotographic processes, electrostatic images may be produced by applying a charge of a certain definite polarity onto the insulating layer, simultaneously injecting a charge of a polarity opposite to that of the above mentioned charge from the base side so as to bind the charge to the neighbourhood of interface between the photoconductive layer and the insulating layer and in the photoconductive layer. And further a DC. voltage corona charging having a polarity opposite to that of the primary charging or an AC. corona charging is applied thereto simultaneously with imagewise exposure and the trapped charge is released at the light portion, but not at the dark portion, and then a blanket irradiation is applied to increase the contrast and form an electrostatic image.
Important matter in the three layer photosensitive member is pertinent to the charging state of charge trapped by primary charging. It is highly desired that the charge is stably retained, the sensitivity of photoconductor layer is increased and photocarrier is easily and sufficiently injected from the base to thephotosensitive layer.
Referring to FIG. 1, a rectifyinglayer 3 is provided between a highly sensitive photoconductor layer 2 and a base 4 so as to inject easily .photocarriers and retain a charge of a polarity opposite to that of the trapped charge in an insulating-layer l by primary charging at a neighbourhood of the interface between the photoconductor layer 2 and the insulating layer.
A photosensitive member having an Se-Te alloy layer provided on a conductor by vapor deposition or plating has sensitivity varying depending upon the contents of Te. The more the contents of Te, the higher the sensi-- tivity. The sensitivity becomes maximum at about 20 percent by weight of Te and the resistance decreases, but the crystallization is accelerated and life of the photosensitive member itself is shortened.
The present inventors have found that the crystallization can be suppressed without decreasing the sensitivity by incorporating 0.01 to 8 percent by weight of Ge, Si or Ge-Se. When the resulting material is used as a photoconductor layer, the Se contains 6 45 percent (by weight) Te and, if desired, additionally contains 0.01 to 8 percent (by weightlGe, Si or Ge-Si. The photoconductor can be vapor-deposited on an aluminum plate to form a photoconductor layer. The resulting photosensitive member is positively or negatively charged by a corona charger in a dark place for a time of period t. The resulting charged potential measured by an electrometer is as shown in FIG. 2. That is, the charge amount at charging time f is decayed gradually by dark discharging regardless the polarity of the charging. In FIG. 2, a denotes a positive charging curve and b denotes a negative charging curve.
On the contrary, when the content of Te in Se is decreased to less than about 5 percent, vapor-deposited on an aluminum plate to form a photosensitive member. Negative and positive charging are applied to the photosensitive member to give the charging curves as shown in FIG. 3. As compared with the curves for large Te content, the surface potential in. case of negative chargingin FIG. 3 is remarkably less. In other words, it is interpreted that injection of positive hole (photocarrier) from the conductive layer (base) becomes easy.
When the above-mentioned Se or Se alloys containing various amounts of Te are used in combination, and positive or negative charging is applied for a time of period f, the charging state is as illustrated in FIG. 4.
The negative charging curve is almost the same as that of the rectifying layer containing less than 6 percent of Te as shown in FIG. 3 and the positive charging curve is almost the same as that of photoconductor layer of relatively high decay as shown in FIG. 2.
FIG. shows a change of surface potential measured by an electrometer when a negative charge is applied to a photosensitive member comprising a photoconductor layer showing the charging and dark discharging characteristics as shown in FIG. 2 and an insulating layer overlying thereon, and to a photosensitive member comprising a photosensitive layer having a rectifying property and having the charging and dark discharging characteristics as shown in FIG. 3 and FlG. 4 and an insulating layer overlying thereon, for a time of period f and discharged in a dark place or exposed to light.
In FIG. 5, decay curves for Se or Se alloy containing more than 6 percent Te are represented by a and a, where the curve a shows a decay caused by exposure while the curve a shows a decay caused by dark discharging. Decay curves for Se or Se alloy containing less than 6 percent Te are represented by B and B, where B is for exposure while B is for dark exposure. There is hardly recognized any difference between B and B.
As is indicated in FIG. 5, the surface potential of the photosensitive member containing Se or Se alloy containing not less than 6% Te (corresponding to the shape of FIG. 2) decreases after charging. The abovementioned photosensitive member has a distribution of charge when charged. The charge is injected from the conductive layer 11 as the time passes to neutralize the charge on the insulating layer 13 and then is decreased. On the other hand, electrostatic charge is uniformly charged on the insulating layer 13 and in the neighbourhood of the interface between the insulating layer and the photoconductor layer 12 in case of providing a rectifying layer 14 as shown in FIG. (B) and there hardly appears a decay. This fact indicates that positive I holes are sufficiently injected.
' minum, copper, brass and the like at an optional thickness in a desired form such as sheet, web, plate, drum and cylinder. On the base there are overlaid a rectifying layer and a photoconductor layer by a known layer forming method such as a flash method, a co-vapor deposition method, a vacuum vapor-deposition method.
The rectifying layer may be formed by vapordepositing on a base a chalcogen substance containing 0 6 percent (by weight) Te such As Se, Se-Te, Se Ge, Se-Si, Se-Ge-Si, Se-Te-Ge, Se-Te-Si, Se-Te-Ge-Si and the like at a temperature of the base of from about 65C to about 80C to form the deposit layer of about lpt 60p. thick.
The photoconductor layer may be produced by depositing a chalcogen substance containing more than 6 percent (by weight) Te, preferred with up to 45 percent, such as Se-Te, Se-Te-Ge, Se-Te-Si, Se-Te-Ge-Si and the like in a thickness of about 1 80;!"
As the insulating layer overlying the photoconductor layer, there may be used any insulating material which is excellent in charge retention property and can pass a radiation to which the photoconductor is sensible. Representative insulating materials are organic insulating layer such as synthetic resin film, for example, polypropylene and polyester, inorganic insulating material such as alumina, mica and-the like, and composite-of inorganic and organic insulating materials.
The following examples are given for illustrating the present invention, but should not be construed as restricting the scope of the invention.
EXAMPLE 1 Se powder (purity of higher than 99.99 percent) and Te powder (purity of higher than 99.99 percent) are mixed in a weight ratio of 9 I, placed in a quartz ampoule at about 10 Torr., sealed, and heated at about 550C for 7 hours to melt the contents. It is preferable to stirring sufficiently the melt by vibration or rotation. The ampoule is, then, put in water to quench. Thus, there is obtained a glassy alloy of Se-Te. The resulting glassy alloy is vapor-deposited on an aluminum base to form a photosensitive layer of about 40 thick at 10 10 mm Hg at a temperature of base of 65 C at a temperature of vapor source of about 250C. Then, a polyethylene terephthalate film of 25 thick is adhered to a surface of the photosensitive layer by using an epoxy resin to produce a photosensitive member of three-layer structure. The resulting photosensitive member is hereinafter called standard photosensitive member" On the other hand, Se powder is sealed in a quartz ampoule at about 10 Torr. The ampoule is heated at about 500C for 6 hours to melt the contents and the ampoule is, then, put in water to quench. Thus, a glassy selenium is obtained. The glassy selenium is vapordeposited on an aluminum base at 10 10 mm Hg at a temperature of base of 65 C at a temperature of vapor source of about 250C to form a rectifying layer of about 20 u in thickness. The above mentioned Se-Te glassy alloy is vapor-deposited on the rectifying layer at 10 10 mm Hg at a temperature of base of 65 C at atemperature of vapor source of about 250C to form a photosensitive layer of about 30 p. in thick. Then, a polyethylene terephthalate film of 25 p. in thickness is adhered to the surface of the photosensitive layer by using an epoxy resin to form a photosensitive member of four layer structure.
An electrophotographic method of Japanese Publication No. 24748/1968 is applied to the standard photosensitive member at an exposure amount of 10 lux-sec. to form an image having an electrostatic contrast of about 400 V.
On the other hand, when the above-mentioned electrophotographic method is applied to a photosensitive member according to this invention with the same conditions as those for the standard photosensitive member, and an electrostatic contrast of as high as about 600 V at an exposure amount of 5 lux-sec. is obtained, and this photosensitive member also shows excellent resolving power and panchromatic property. EXAMPLE 2 Se, Te and Ge powders (each being purity higher than 99.99 percent) are mixed in a ratio of atom numher of l 1 l, ball-milled for about 20 hours, sealed in a quartz ampoule at about Torr., and heated at about 800C for 50 hours to melt the contents. It is preferable to agitate the melt by vibration or rotation. The ampoule is put in water to quench and thus a glassy alloy of Se-Te-Ge is obtained. On the other hand, an alloy of Se-Te alloy (Se Te being 100 7 by weight) is obtained by a procedure similar to Example 1. On a surface of Se rectifying layer on an aluminum plate obtained as in Example l there is produced a photosensitive layer of about 30 p. thick by co-vapor deposition method using Se-Te-Ge alloy or Se-Te alloy. The resulting photosensitive layer contains Se, Te and Ge in a weight ratio of about 90 l0 0.4. The vapor deposition conditions are: pressure, 10 4 10' mm Hg; base temperature, 65 82C; vapor source temperature, about 550C for Se-Te-Ge alloy, about 250C for Se-Te alloy. Then, a polyethylene terephthalate film of 25 p. in thickness is adhered to the surface of the photosensitive layer with an epoxy resin to produce a photosensitive member of four-layer structure.
To the above-mentioned photosensitive member is applied an electrophotographic process of Japanese Patent Publication No. 24748/1968 under the same conditions as in Example 1. There is obtained an electrostatic contrast of as high as'about 550 V at an exposure amount of 5 lux-sec., and the resolving power, panchromatic property and durability are also excellent.
1. An electrophotographic photosensitive member comprising a base, a photoconductor layer containing Se-Te, an insulating layer overlying the photoconductor layer, and rectifying layer means containing selenium and being provided between the base and the photoconductor layer for injecting an electric charge into said photoconductor layer from said base, wherein said photoconductor layer contains 6 45% Te and 0.01 8 percent of at least one of Ge, Si and Ge-Si.
2. An electrophotographic photosensitive member according to claim 1 wherein said rectifying layer means contains Te in an amount up to 6 percent by weight.