(19)
(11)EP 0 176 221 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
28.02.1990 Bulletin 1990/09

(21)Application number: 85305894.9

(22)Date of filing:  19.08.1985
(51)International Patent Classification (IPC)5G03G 5/04, G03G 5/06, G03G 13/02

(54)

Photoreceptor for positive electrostatic charge

Photorezeptor für positive elektrostatische Ladung

Photorécepteur pour charge électrostatique positive


(84)Designated Contracting States:
DE FR GB

(30)Priority: 17.08.1984 JP 171745/84

(43)Date of publication of application:
02.04.1986 Bulletin 1986/14

(73)Proprietor: KONICA CORPORATION
Tokyo 163 (JP)

(72)Inventors:
  • Fujimaki, Yoshihide
    Hachioji-shi Tokyo (JP)
  • Takimoto, Masataka
    Hachioji-shi Tokyo (JP)
  • Suzuki, Yasuo
    Hachioji-shi Tokyo (JP)

(74)Representative: Myerscough, Philip Boyd et al
J.A. Kemp & Co. 14 South Square, Gray's Inn
GB-London WC1R 5EU
GB-London WC1R 5EU (GB)


(56)References cited: : 
EP-A- 0 144 791
US-A- 4 348 470
US-A- 4 359 513
US-A- 4 400 455
US-A- 4 440 845
DE-A- 2 804 669
US-A- 4 356 243
US-A- 4 390 611
US-A- 4 426 432
US-A- 4 447 513
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description


    [0001] The invention relates to a photoreceptor for positive electrostatic charge such as an electrophotographic photoreceptor for positive electrostatic charge.

    [0002] Until now, electrophotographic photoreceptors have commonly comprised an inorganic photoreceptor bearing a photosensitive layer mainly comprising an inorganic photoelectroconductive substance such as selenium, zinc oxide, cadmium sulfide and the like.

    [0003] Recently, however, a variety of organic photoelectroconductive substances have been researched and developed for use in the photosensitive layers of such electrophotographic photoreceptors.

    [0004] For example, Japanese Patent Examined Publication No. 10496/1975 describes organic photoreceptors bearing a photosensitive layer comprising poly-N-vinyl carbazole and 2,4,7-trinitro-9-fluorenone. However, this photoreceptor does not always exhibit satisfactory sensitivity and durability. Attempts have therefore been made to develop organic photoreceptors having a high sensitivity and an increased durability in such a manner that, when they are used in a photosensitive layer, a carrier generating function and a carrier transport function are allotted separately to different substances. In the so-called function separation type electrophotographic photoreceptors such as mentioned above, the substances capable of displaying each function may be selected from a wide range of substances. It is, therefore, relatively easy to make an electrophotographic photoreceptor having any desired characteristics.

    [0005] Many substances have so far been proposed as the carrier generating substances in such function separation type electrophotographic photoreceptors. Examples of those using an inorganic substance include amorphous selenium, as described in Japanese Patent Examined Publication No. 16198/1968, which is used in combination with an organic carrier transporting substance.

    [0006] Many electrophotographic photoreceptors using an organic dyestuff or an organic pigment as the carrier generating substances have also been proposed. They include, for example, those having a photosensitive layer including a bisazo compound, which are disclosed, for example, in Japanese Patent Publication Open to Public Inspection Nos. 37543/1972, 22834/1980, 79632/1979, 116040/1981.

    [0007] Photoreceptors using an organic photoelectroconductive substance are normally used for negative electrostatic charge. The reason is that they show good photosensitivity because the Hall mobility of carriers is great when an electrostatic charge is negative.

    [0008] In using such a negative charge, certain problems arise. Firstly ozone is likely to be produced in the atmosphere when a negative electric charge is applied which may aggravate environmental conditions. Another problem is that toners of positive polarity are required in the development of a photoreceptor for negative electrostatic charge and such toners of positive polarity cannot readily be prepared from the viewpoint of the triboelectrification series to ferromagnetic carrier particles.

    [0009] A photoreceptor has accordingly been proposed which uses an organic photoelectroconductive substance with a positive charge. For example, in the case of a photoreceptor for positive electrostatic charge comprising a carrier transport layer laminated on a carrier generation layer, the carrier transport layer being formed of a substance having a relatively high electron transport function, the carrier transport layer must include trinitrofluorenone or the like; this is not, however, suitable for use because this substance is carcinogenic. It may alternatively be possible to use a photoreceptor for positive electrostatic charge which is prepared by laminating a carrier generation layer on a carrier transport layer having a relatively high Hall transport function. With this photoreceptor, however, there is an extremely thin carrier generation layer on the surface of the photoreceptor, and so the printing resistance and the like are deteriorated making layer arrangement unsuitable for practical use.

    [0010] US―A―3615414 discloses a photoreceptor for positive charge comprising a thiapyrylium salt as the carrier generating substance, which forms a eutectic complex with polycarbonate, i.e. the binder resin. This photoreceptor has the disadvantages of a relatively serious memory phenomenon and, a tendency to form shadows. US―A―3357989 discloses a photoreceptor including phthalocyanine. However, phthalocyanine does not have consistent properties because of its crystal systems, which need to be strictly controlled; in addition, the unsatisfactory sensitivity at short wavelengths and the serious memory phenomenon mean that such a photoreceptor is not suitable for use in copying apparatus using a light source having a wavelength region of visible light.

    [0011] EP-A-0,144,791, having an earlier priority date than, but published after, the priority date of the present application, discloses a photoreceptor comprising a light-sensitive layer composed of a carrier generating phase and a carrier transporting phase, the carrier generating phase comprising specific bisazo compounds and the carrier transporting phase containing specific styryl, hydrazone or amine derivatives.

    [0012] US-A-4,356,243 discloses an electrophotographic light-sensitive medium comprising a particular disazo compound.

    [0013] US-A-4,440,845 discloses an electrophotographic element which includes a disazo compound.

    [0014] US-A-4,400,455 describes a layered electrophotographic photoconductor comprising a charge generating layer containing a bisazo pigment and a charge transporting layer containing a hydrazone compound.

    [0015] US-A-4,348,470 describes a layered electrophotographic element containing a charge generating layer including a disazo pigment and a charge transport layer.

    [0016] Photoreceptors using an organic photoelectroconductive substance have so far not been feasible for positive electrostatic charge and have only been used for negative charge.

    [0017] One object of the invention is, accordingly, to provide a photoreceptor which is suitable for positive electrostatic charge, shows excellent dispersibility or distribution of the carrier generating substance, is capable of reducing memory phenomena, will stabilize the residual potential and improve the printing resistance and is also capable of forming consistently good visible images.

    Brief Description of the Drawings



    [0018] The drawings illustrate embodiments of the invention.

    Fig. 1 is a cross section of a portion of each example of the electrophotographic photoreceptor; and

    Fig. 2 is a drawing illustrating the characteristic variations according to the constitutions of each electrophotographic receptor.



    [0019] The present invention provides a photoreceptor suitable for carrying positive electrostatic charge comprising a carrier generation layer and a carrier transport layer, wherein said carrier generation layer contains a carrier generating substance whose photosensitivity when negatively charged is higher than that when positively charged, a carrier transporting substance and a binder and the thickness of said carrier generation layer is from 1µm to 10 pm, and said carrier transport layer contains a carrier transporting substance and a binder and is present on the lower surface of said carrier generation layer, wherein said carrier generating substance has the formula:

    Formula (I) - azo Compounds













    wherein

    Ar1, Ar2 and Ar3 each independently represents a substituted or unsubstituted carbocyclic radical;

    Cp represents



    wherein

    Z represents a group of atoms forming a substituted or unsubstituted aromatic carbocyclic ring or a substituted or unsubstituted aromatic heterocyclic ring;

    Y represents hydrogen, a hydroxyl group, carboxyl group or a carboxy ester group, a sulfo group, a substituted or unsubstituted carbamoyl group, or a substituted or unsubstituted sulfamoyl group;

    R1 represents hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted amino group, a substituted or unsubstituted carbamoyl group, a carboxyl group or a carboxy ester group, or a cyano group;

    Ar4 represents a substituted or unsubstituted aryl group; and

    R2 represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aralkyl group, or substituted or unsubstituted aryl group;

    Formula (I') - azo Pigments



    wherein

    Ar5, Ar6 and Ar7 each independently represents a substituted or unsubstituted carbocyclic aromatic radical;

    A represents



    or

    wherein n is 1 or 2, m is 0 or an integer from 1 to 4,

    X' represents a hydroxy group,

    wherein R4 and R5 independently represent hydrogen, or a substituted or unsubstituted alkyl group; and R6 represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group,

    Y' represents hydrogen or halogen, a substituted or unsubstituted alkyl group, an alkoxy group, a carboxy group, a sulfo group, a substituted or unsubstituted carbamoyl group, or a substituted or unsubstituted sulfamoyl group, such that if m is not less than 2 each Y' may be the same or different;

    Z' represents a group of atoms forming a substituted or unsubstituted carbocyclic aromatic ring or a substituted or unsubstituted heterocyclic aromatic ring; R3 represents hydrogen, a substituted or unsubstituted amino group, a substituted or unsubstituted carbamoyl group, or a carboxyl group or a carboxy ester group; and

    A' represents a substituted or unsubstituted aryl group;

    Formula (I") - azo Pigments





    wherein

    Ar1, Ar2 and Ar3 each independently represent a substituted or unsubstituted carbocyclic aromatic ring group;

    R1, R2, R3 and R4 each independently represent an electron withdrawing group or hydrogen, such that at least one of R1 to R4 is an electron withdrawing group;

    A is



    or

    wherein

    n is 1 or 2, m is 0 or an integer from 1 to 4, X represents a hydroxy group,

    such that R6 and R7 each independently represent hydrogen, or a substituted or unsubstituted alkyl group and R8 represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group;

    Y represents hydrogen or halogen, a substituted or unsubstituted alkyl group, an alkoxy group, a carboxyl group, a sulfo group, a substituted or unsubstituted carbamoyl group or a substituted or unsubstituted sulfamoyl group, such that if m is not less than two each

    Y may be the same or different;

    Z represents a group of atoms forming a substituted or unsubstituted carbocyclic aromatic ring or a substituted or unsubstituted heterocyclic aromatic ring;

    R5 represents hydrogen, a substituted or unsubstituted amino group, a substituted or unsubstituted carbamoyl group, or a carboxyl group or a carboxy ester group;

    A' represents a substituted or unsubstituted aryl group;

    Formula (II) - polycyclic quinone pigments



    and

    wherein

    X" represents halogen, a nitro group, cyano group, acyl group or carboxyl group;

    n is 0 or an integer from 1 to 4; and

    m is 0 or an integer from 1 to 6.



    [0020] An example of an electron withdrawing group represented by R' to R4 in a compound of formula (I") is a cyano group.

    [0021] According to the invention, the carrier generation layer can be prepared by solidifying both the particulate carrier generating substance and the carrier transporting substance with the binder substance. Since the carrier generating substance is particulate, that is dispersed in the form of pigment in the layer, the quality of printing resistance and the like is high and, at the same time, memory phenomena are reduced and residual potential stabilized. In addition, the particulate carrier generating substance is required so that there is a sufficient electron transport function within the layer. In other words, when a photoreceptor for positive electrostatic charge is irradiated with light, the photoreceptor comprising a mixed phase type photosensitive layer including the above-mentioned carrier generating substance and carrier transporting substance, the surface positive potential is attenuated only to a limited extent. According to the invention, however, a carrier generating substance is used which gives rise to a relatively faster electron mobility rate when negatively charging a photoreceptor bearing an independent photosenstive layer, than when positively charging such a photoreceptor. In other words, photosensitivity is higher when negatively charging. The electrons which are produced by irradiating the positively charged photoreceptor bearing the above-mentioned mixed phase photosensitive layer with light, will move at a high speed to the surface of the photoreceptor. This causes the surface positive potential to be attenuated satisfactorily i.e. the photosensitivity is improved and the residual potential is also reduced. In addition, however, the properties of the carrier transport substances according to the invention are such that Hall mobilization may easily be effected. The photoreceptors may therefore also be positively charged, provided that properties of the above-mentioned carrier generating substance are utilized in combination and the sublayered carrier transport layer is provided.

    [0022] An essential feature of the invention is that the above-mentioned carrier generating layer is provided onto the surface in a thickness of at least 1 pm, more desirably at least 3 µm. If the potential generation layer is thinner than 1 µm, the surface will be mechanically damaged by repeated developing and cleaning when the photoreceptor is in use. For example, a portion of the layer is shaved off or black streaks are produced on an image. For this reason, the layer must not be thinner than 1 µm. In contrast, however, if the thickness of such potential generation layer is too great and is, for example, at least 10 pm, then more thermally excited carriers are generated; the receptive potential and density in image area will be lowered and the temperature will be raised. Furthermore, if the irradiating light has a longer wavelength than that of the absorption edge of the carrier generating substance, photo-carriers are generated even in the vicinity of the lowermost portion of the potential generation layer. In such a situation the electrons have to move up to the surface of the layer and, as a result, a satisfactory transport function is not obtained. Accordingly, when operating repeatedly, the residual potential tends to rise.

    [0023] For the above reasons, the thickness of the carrier generation layer should be no less than 1 pm and not more than 10 pm.

    [0024] In the meantime, the thickness of the aforementioned potential transport layer is preferably between 5 pm and 50 pm, and more preferably between 5 µm and 30 µm.

    [0025] The ratio of the thickness of the carrier generation layer to that of the carrier transport layer is preferably 1:1 to 1:30.

    [0026] In the invention, the carrier generation layer is formed such that the carrier generating substance is dispersed in the form of particles (as a pigment) in a layer prepared by solidifying a carrier transporting substance with a binder substance. The average particle size of the carrier generating substance is generally not larger than 2 um, more preferably not larger than 1 µm. If the average particle size is too large, dispersibility deteriorates and the particles will tend to cohere and be localized in certain areas. Furthermore, extra toners will adhere to such localized areas, which tends to cause so-called toner filming phenomena.

    [0027] According to the invention, a charge transfer complex is formed if an electron receptive substance or Lewis acid is added to the photosensitive layer: this improves the sensitization effect.

    [0028] Typical examples of azo compounds of formula (I) and azo pigments of formulae (I') and (I") are:



































































































































































































































































































































































    [0029] Typical examples of polycyclic quinone pigments of formula (II) are:



























































    [0030] Suitable carrier transporting substances for use in the invention include, for example, an oxazole derivative, an oxadiazole derivative, a thiazole derivative, a thiadiazole derivative, a triazole derivative, an imidazole derivative, an imidazolone derivative, an imidazolidine derivative, a bisimidazolidine derivative, a styryl compound, a hydrazone compound, a pyrazoline derivative, an oxazolone derivative, a benzothiazole derivative, a benzimidazole derivative, a quinazoline derivative, a benzofuran derivative, an acridine derivative, a phenazine derivative, an aminostilbene derivative, poly-N-vinylcarbazole, poly-1-vinylpyrene, and poly-9-vinylanthracene.

    [0031] Styryl compounds represented by the following formula [III] or [IV] can be used as the carrier transporting substances:

    wherein

    R8 and R9 represent an alkyl group or aryl group, unsubstituted or substituted by an alkyl group, alkoxy group, a substituted amino group, a hydroxyl group, a halogen or an aryl group;

    Ar4 and Ar5 represent an aryl group, unsubstituted or substituted by an alkyl group, an alkoxy group, a substituted amino group, a hydroxyl group, a halogen, or an aryl group; and

    R10 and R11 represent hydrogen or an aryl group, unsubstituted or substituted by an alkyl group, an alkoxy group, a substituted amino group, a hydroxyl group, a halogen, or an aryl group.

    wherein

    R12 represents a substituted or unsubstituted aryl group;

    R13 represents hydrogen, a halogen, a substituted or unsubstituted alkyl group, an alkoxy group, an amino group, a substituted amino group or a hydroxyl group; and

    R14 represents a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic ring group.



    [0032] Typical examples of the styryl compounds represented by the Formula [III] or [IV] are as follows:





























































































































































































































    [0033] To serve as the carrier transporting substances, the hydrazone compounds represented by the following Formula [V], [VI], [VII] or [VIII] can be used;

    Formula [V]:

    wherein

    R15 and R16 each are hydrogen or a halogen;

    R17 and R18 each represent a substituted or unsubstituted aryl group; and

    Ar6 represents a substituted or unsubstituted arylene group.

    wherein

    R19 represents a methyl group, an ethyl group, 2-hydroxyethyl group or 2-chloroethyl group;

    R20 represents a methyl group, ethyl group, benzyl group or phenyl group; and

    R21 represents a methyl group, ethyl group, benzyl group or phenyl group.

    wherein

    R22 represents a substituted or unsubstituted naphthyl group;

    R23 represents a substituted or unsubstituted alkyl group, aralkyl group or aryl group;

    R24 represents hydrogen, an alkyl group or alkoxy group; and

    R25 and R26, which are the same or different, are each a substituted or unsubstituted alkyl group, aralkyl group or aryl group.

    wherein

    R27 represents a substituted or unsubstituted aryl group or a substituted or unsubstituted heterocyclic ring group;

    R28 represents hydrogen, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group;

    Q represents hydrogen, a halogen, an alkyl group, a substituted amino group, alkoxy group or cyano group; and

    p is an integer of zero or one.



    [0034] Typical examples of the hydrazone compounds represented by the Formulas [V] through [VIII] are as follows:













































































































































































































































































    [0035] Pyrazoline compounds represented by the following formula [IX] can also be used as the carrier transporting substances:

    I is zero or one;

    R29, R30 and R31 each represent a substituted or unsubstituted aryl group;

    R32 and R33 each represent hydrogen, an alkyl group having one to four carbon atoms, or a substituted or unsubstituted aryl or aralkyl group; provided that R32 and R33 are not hydrogen at the same time, and R32 is not hydrogen if I is zero.



    [0036] Typical examples of the pyrazoline compounds are as follows:







































    [0037] Amine derivatives represented by the following formula [X] can also be used as the carrier transporting substances:

    wherein

    ArB and Ar7 each represent a phenyl group, unsubstituted or substituted by a halogen, an alkyl group, nitro group or alkoxy group, Ar8 represents a naphthyl group, anthryl group, fluorenyl group, heterocyclic ring group or phenyl group unsubstituted or substituted by an alkyl group, an alkoxy group, a halogen, a hydroxyl group, an aryloxy group, an aryl group, an amino group, a nitro group, a piperidino group, a morpholino group, a naphthyl group, an anthryl group or an amino group which is substituted by an acyl group, an alkyl group, an aryl group or an aralkyl group.



    [0038] Typical examples of the amine derivatives are given below:



































































    [0039] According to the invention, a photoreceptor for positive charge which is improved with respect of residual potential and receptive potential can be provided, if the carrier generating substance is added to the binder substance in an amount of 20 to 50 parts by weight, of carrier generating substance to 100 parts by weight of the binder substance. The range of 25 to 40 parts by weight of carrier generating substance to 100 parts by weight of binder substance is particular desirable. If insufficient carrier substance is included, the photosensitivity will be lowered and the residual potential will be increased. If an excess of carrier generating substance is used, the receptive potential will be lowered. The contents of the carrier transporting substance are also an important factor. The proportion of carrier transporting substance to the binder substance suitably from 20 to 200 parts by weight of the former to 100 parts by weight of the latter; 30 to 50 parts by weight of carrier transporting substances is particularly suitable. When the proportion is within this range, the residual potential is relatively low and photosensitivity is high and, in addition, the solubility of the carrier transporting substance can well be maintained. If the proportion is outside the range and the content of carrier transporting substance is low, the residual potential and the photosensitivity are apt to deteriorate, whereas if there is an excess of transporting substance, the solubility is apt to deteriorate. The content range of the carrier transporting substance may also be applicable to the carrier transport layer.

    [0040] In the carrier generation layer, the rate by weight of carrier generating substance to carrier transporting substance is generally from 1:3 to 1:2 for the functions of each substance to be displayed effectively.

    [0041] Suitable binder substances, among them binder resins, include, for example, addition polymerization type resin, polyaddition type resin and polycondensation type resins such as polyethylene, polypropylene, acryl resin, methacryl resin, vinylchloride resin, vinylacetate resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyl resin, polycarbonate resin, silicone resin, and melamine resin, a copolymer resin containing two or more repetition units of the above-mentioned resins, for example an insulating resin such as vinyl chloride - vinyl acetate copolymeric resin, and vinyl chloride - vinyl acetate - maleic hydride copolymeric resin, and a high molecular organic semiconductor such as poly-N-vinyl carbazole.

    [0042] When an electrophotographic photoreceptor is prepared so as to be of the function-separation type, normally the constitution thereof is as shown in Fig. 1. Such a photoreceptor comprises an electroconductive support 1 bearing a photosensitive layer 4 laminated with a carrier generation layer of 1 pm in thickness, prepared by dispersing the aforementioned particulate carrier generating substance 7 in a layer 6 comprising the above-mentioned carrier transport substance as principal ingredient, and a carrier transport layer 3 comprising the above-mentioned carrier transporting substance. In the constitution shown in Fig. 1, an interlayer (not shown) may also be provided between the electroconductive support 1 and the photosensitive layer 4.

    [0043] When a photosensitive layer is formed by dispersing therein the above-mentioned particulate carrier generating substance, the carrier generating substance is a maximum average particle size of 2 pm and more preferably not larger than 1 pm. If the particle size is too large, dispersion thereof into the layer is poor and the smoothness of the layer surface is also diminished. Further, in some cases, an electric discharge will be generated from the protruding portions of the particles, or toner particles will adhere to the protruded portion of the particles and cause a toner filming phenomenon. In a carrier generating substance having sensitivity to wavelengths of up to 700 nm, it is assumed that the surface potential may be neutralized by generating a thermal excitation carrier in the carrier generating substance and that this neutralization effect is greatest when the particle size of the carrier generating substance is large. Accordingly, high resistance and high sensitization cannot be achieved unless particle size is very small. However, if the particle size is too small any advantage is lost because cohesion is apt to arise which increases the resistance of the layer and decreases the sensitivity and the repetition property. It is therefore desirable to limit the average particle size to a minimum of 0.1 pm.

    [0044] Photosensitive layers according to the invention can be prepared as follows. In this process, carrier generating substance is made into fine particles in a dispersion medium by means of a ball mill, a homogenizer or the like. A binder resin and a carrier transporting substance are added to make a mixed dispersion, and the resulting dispersion solution is coated on. In this process a uniform dispersion can be achieved if the particles are dispersed under the application of ultrasound. The carrier transport layer can also be formed by coating with a solution of the carrier transporting substance.

    [0045] Suitable dispersion media for the above-mentioned layers include, for example, N,N-dimethyl formamide, benzene, toluene, xylene, 1,2-dichloroethane, dichloromethane, and tetrahydrofuran.

    [0046] Suitable binder resins for use in forming a photosensitive layer include, in particular, electric-insulating film-forming high molecular polymers which are hydrophobic and high in electric permitivity.

    [0047] In addition, in order to improve sensitivity, and reduce the residual potential and/or the fatigue caused by repeated use, the above-mentioned photosensitive layer may contain one or more kinds of electron receptive substances. Examples of such electron receptive substances include succinic anhydride, maleic anhydride, debromomaleic anhydride, phthalic anhydride, tetrachlorophthalic anhydride, tetrabromophthalic anhydride, 3-nitrophthalic anhydride, 4-nitrophthalic anhydride, pyromellitic anhydride, mellitic anhydride, tetracyanoethylene, tetracyanoquinodimethane, o-dinitrolobenzene, m-dinitrolobenzene, 1,3,5- trinitronbenzene, paranitrobenzonitrile, picrylchloride, quinonechlorimide, chloranil, bromanil, dichloro- dicyanoparabenzoquinone, anthraquinone, dinitroanthraquinone, 9-fluorenyliden[dicyanomethylene- malonodinitrile], polynitro-9-fluorenylidene-[dicyanomethylenemalonodinitrile], picric acid, o-nitrobenzoic acid, p-nitrobenzoic acid, 3,5-dinitrobenzoic acid, pentafluorobenzoic acid, 5-nitrosalicylic acid, 3,5-dinitro- salicyclic acid, phthalic acid, metallic acid, and other compounds having a high electron-affinity. The proportion of the electron receptive substance to the carrier generating substance 0.01:100 to 200:100 by weight and preferably 0.1:100 to 100:100 by weight.

    [0048] i The supports (1) to be provided with the above-mentioned photosensitive layer may comprise a metal plate, a metal drum, or a support of which the substance such as a sheet of paper, plastic film or the like coated, evaporated or laminated with an electroconductive thin layer comprising an electroconductive polymer, electroconductive compound such as indium oxide, or a metal such as aluminium, palladium or gold. The interlayers which function as an adhesive layer or a barrier layer include those interlayers comprising a high molecular polymer, an organic high molecular substance such as polyvinyl alcohol, ethyl cellulose or carboxymethyl cellulose, or aluminium oxide, which were described as the aforementioned binder resins.

    Example



    [0049] The following example illustrates the invention, by reference to a comparative example:

    [0050] An interlayer of 0.05 µm in thickness was formed comprising an electroconductive support comprising a polyester film laminated with an aluminium foil bearing thereon vinyl chloride - vinyl acetate - maleic anhydride copolymer, [Eslec MF-10, manufactured by Sekisui Chemical Co.]. Next, the carrier transporting substance and the binder resin each shown in Fig. 2 were dissolved in 67 ml of 1,2-dichloroethane. The resulting solution was coated over the interlayer, so that a carrier transport layer was prepared. Both the carrier generating substance and the carrier transporting substances, each having the specific particle sizes indicated in Fig. 2, and the binder resins, were added to 67 ml of 1,2-dichloroethane and dispersed by a ball mill for 12 hours. The resulting solution was coated over the above-mentioned carrier transport layer and dried so as to form a carrier generation layer. Each of the electrophotographic photoreceptors were prepared in this way.

    [0051] The electrophotographic photoreceptors were tried on an electrostatic test machine [SP-428, manufactured by Kawaguchi Electric Mfg. Co.], and the properties thereof were examined. More specifically, in each of the tests, a photosensitive layer was electrically charged by applying a corona discharge for 5 seconds after applying a +6KV voltage to an electric charger, and was then allowed to stand for 5 seconds, (the voltage at this point of time is called V,). Next, the surface of the photosensitive layer was irradiated with light from a tungsten lamp such that the illuminance thereon was at 35 lux, so as to obtain an exposure amount necessary for attenuating the surface potential of the photosensitive layer to a half, that was a half attenuation exposure amount, E½. Measurements were made for the receptive voltage VA at the initial stage where the charging was made by the above-mentioned corona discharge and the receptive voltage after 10,000 copies were made. And, the measurements were made for the dark attenuation ratio, (VA - Vi)/Ni × 100(%), and the exposure quantity, ES50500 (lux.sec.) which is necessary for attenuating the initial voltage V, from -500(V) to -50(V).

    [0052] According to the results obtained, it can be found that the samples (No. 1 through No. 10) of the example based on the invention can display considerably excellent electrophotographic characteristics in comparison with the comparative examples No. 1 through 4.


    Claims

    1. A photoreceptor comprising a carrier generation layer and a carrier transport layer, wherein said carrier generation layer contains a carrier generating substance whose photosensitivity when negatively charged is higher than that when positively charged, a carrier transporting substance and a binder and the thickness of said carrier generation layer is from 1 µm to 10 µm, and said carrier transport layer contains a carrier transporting substance and a binder and is present on the lower surface of said carrier generation layer, wherein said carrier generating substance has the formula:











    or

    wherein

    Ar1, Ar2 and Ar3 each independently represents a substituted or unsubstituted carbocyclic radical;

    Cp represents



    wherein

    Z represents a group of atoms forming a substituted or unsubstituted aromatic carbocyclic ring or a substituted or unsubstituted aromatic heterocyclic ring;

    Y represents hydrogen, a hydroxyl group, carboxyl group or a carboxy ester group, a sulfo group, a substituted or unsubstituted carbamoyl group, or a substituted or unsubstituted sulfamoyl group;

    R1 represents hydrogen, a substituted or unsubstituted akyl group, a substituted or unsubstituted amino group, a substituted or unsubstituted carbamoyl group, a carboxyl group or a carboxy ester group, or a cyano group;

    Ar4 represents a substituted or unsubstituted aryl group; and

    R2 represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aralkyl group, or substituted or unsubstituted aryl group;



    wherein

    Ar5, Ar6 and Ar7 each independently represents a substituted or unsubstituted carbocyclic aromatic radical;

    A represents



    or

    wherein n is 1 or 2, m is 0 or an integer from 1 to 4,

    X' represents a hydroxy group,

    wherein R4 and R5 independently represent hydrogen, or a substituted or unsubstituted alkyl group; and R6 represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group,

    Y' represents hydrogen or halogen, a substituted or unsubstituted alkyl group, an alkoxy group, a carboxy group, a sulfo group, a substituted or unsubstituted carbamoyl group, or a substituted or unsubstituted sulfamoyl group, such that if m is not less than 2 each Y' may be the same or different;

    Z' represents a group of atoms forming a substituted or unsubstituted carbocyclic aromatic ring or a substituted or unsubstituted heterocyclic aromatic ring; R3 represents hydrogen, a substituted or unsubstituted amino group, a substituted or unsubstituted carbamoyl group, or a-carboxyl group or a carboxy ester group; and

    A' represents a substituted or unsubstituted aryl group;





    wherein

    Ar1, Ar2 and Ar3 each independently represent a substituted or unsubstituted carbocyclic aromatic ring group;

    R1, R2, R3 and R4 each independently represent an electron withdrawing group or hydrogen, such that at least one of R1 to R4 is an electron withdrawing group;

    A is



    or

    wherein

    n is 1 or 2, m is 0 or an integer from 1 to 4,

    X represents a hydroxy group,

    such that R6 and R7 each independently represent hydrogen, or a substituted or unsubstituted alkyl group and R8 represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group;

    Y represents hydrogen or halogen, a substituted or unsubstituted alkyl group, an alkoxy group, a carboxyl group, a sulfo group, a substituted or unsubstituted carbamoyl group or a substituted or unsubstituted sulfamoyl group, such that if m is not less than two each

    Y may be the same or different;

    Z represents a group of atoms forming a substituted or unsubstituted carbocyclic aromatic ring or a substituted or unsubstituted heterocyclic aromatic ring;

    R5 represents hydrogen, a substituted or unsubstituted amino group, a substituted or unsubstituted carbamoyl group, or a carboxyl group or a carboxy ester group;

    A' represents a substituted or unsubstituted aryl group;



    and

    wherein

    X" represents halogen, a nitro group, cyano group, acyl group or carboxyl group;

    n is 0 or an integer from 1 to 4; and

    m is 0 or an integer from 1 to 6.


     
    2. A photoreceptor according to claim 1, wherein the thickness of said carrier generation layer is more than 3 pm.
     
    3. A photoreceptor according to claim 1 or 2, wherein the thickness of said carrier transport layer is from 5 µm to 50 pm.
     
    4. A photoreceptor according to claim 3, wherein the ratio (Tg:Tt) of the thickness of said carrier generation layer, Tg, to said carrier transport layer, Tt, is 1:(1 to 30).
     
    5. A photoreceptor according to any one of the preceding claims wherein said carrier transporting substance is an oxazole derivative, an oxadiazole derivative, a thiazole derivative, a thiadiazole derivative, a triazole derivative, an imidazole derivative, an imidazolone derivative, an imidazolidine derivative, a bisimidazolidine derivative, a styryl compound, a hydrazone compound, a pyrazoline derivative, an oxazolone derivative, a benzothiazole derivative, a benzimidazole derivative, a quinazoline derivative, a benzofuran derivative, an acridine derivative, a phenazine derivative, an aminostilbene derivative, poly-N-vinylcarbazole, poly-1-vinylpyrene or poly-9-vinylanthracene.
     
    6. A photoreceptor according to any one of the preceding claims, wherein said carrier generation layer contains said carrier generating substance in an amount from 20% to 50% by weight of said binder and said carrier transporting substance in an amount from 20% to 200% by weight of said binder.
     
    7. A photoreceptor according to any one of the preceding claims wherein the weight ratio, Sg:St, of said carrier generating substance Sg to said carrier transporting substance St in said carrier generation layer is 1:(2 to 3).
     
    8. A photoreceptor according to any one of the preceding claims wherein said carrier generating substance is dispersed in said carrier generation layer as particles whose diameter is less than 2 pm.
     
    9. A process for positive electrification, using a photoreceptor as claimed in any one of the preceding claims.
     


    Ansprüche

    1. Aufzeichnungsmaterial mit einer Ladung erzeugenden Schicht und einer Ladung transportierenden Schicht, wobei die Ladung erzeugende Schicht eine Ladung erzeugende Substanz mit höherer Lichtempfindlichkeit bei negativer Aufladung als bei positiver Aufladung, eine Ladung transportierende Substanz und ein Bindemittel enthält und eine Dicke von 1 µm bis 10 um aufweist, wobei die Ladung transportierende Schicht eine Ladung transportierende Substanz und ein Bindemittel enthält und auf der Unterseite der Ladung erzeugenden Schicht vorgesehen ist, und wobei die Ladung erzeugende Substanz einer der Formeln:













    oder

    worin bedeuten:

    Ar1, Ar2 und Ar3 jeweils unabhängig voneinander einen gegebenenfalls substituierten carbocyclischen Rest, Cp



    mit Z gleich einer Gruppe von einen gegebenenfalls substituierten aromatischen carbocyclischen Ring oder gegebenenfalls substituierten aromatischen heterocyclischen Ring bildenden Atomen;

    Y gleich einem Wasserstoffatom oder einer Hydroxyl-, Carboxyl- oder Carboxyester-, Sulfo-, gegebenenfalls substituierten Carbamoyl- oder gegebenenfalls substituierten Sulfamoylgruppe;

    R' gleich einem Wasserstoffatom oder einer gegebenenfalls substituierten Alkyl-, gegebenenfalls substituierten Amino-, gegebenenfalls substituierten Carbamoyl-, Carboxyl-, Carboxyester- oder Cyanogruppe;

    Ar4 gleich einer gegebenenfalls substituierten Arylgruppe und

    R2 gleich einer gegebenenfalls substituierten Alkyl-, gegebenenfalls substituierten Aralkyl- oder gegebenenfalls substituierten Arylgruppe; oder der Formeln:



    worin bedeuten:

    Ar5, Ar6 und Ar7 jeweils unabhängig voneinander einen gegebenenfalls substituierten carbocyclischen aromatischen Rest und



    oder

    mit n = 1 oder 2, m = 0 oder eine ganze Zahl von 1-4;

    X' gleich einer Hydroxygruppe,

    oder ―NHSO2―R6,
    worin R4 und R5 unabhängig voneinander für ein Wasserstoffatom oder eine gegebenenfalls substituierte Alkylgruppe stehen und R6 einer gegebenenfalls substituierten Alkylgruppe oder einer gegebenenfalls substituierten Arylgruppe entspricht,

    Y' gleich einem Wasserstoff- oder Halogenatom, einer gegebenenfalls substituierten Alkylgruppe, einer Alkoxygruppe, einer Carboxygruppe, einer Sulfogruppe, einer gegebenenfalls substituierten Carbamoylgruppe oder einer gegebenenfalls substituierten Sulfamoylgruppe, wobei im Falle, daß m nicht weniger als 2 bedeutet, die Reste Y' gleich oder verschieden sein können;

    Z' gleich einer Gruppe von einen gegebenenfalls substituierten carbocyclischen aromatischen Ring oder einen gegebenenfalls substituierten heterocyclischen aromatischen Ring bildenden Atomen;

    R3 gleich einem Wasserstoffatom, einer gegebenenfalls substituierten Aminogruppe, einer gegebenenfalls substituierten Carbamoylgruppe oder einer Carboxyl- oder Carboxyestergruppe, und

    A' gleich einer gegebenenfalls substituierten Arylgruppe; oder der Formeln:



    oder

    worin bedeuten:

    Ar1, Ar2 und Ar3 jeweils unabhängig voneinander eine gegebenenfalls substituierte carbocyclische aromatische Ringgruppe;

    R1, R2, R3 und R4 jeweils unabhängig voneinander eine Elektronen abziehende Gruppe oder ein Wasserstoffatom, wobei mindestens einer der Reste R' bis R4 für eine Elektronen abziehende Gruppe steht;

    Δ



    oder

    worin n = 1 oder 2, m = 0 oder eine ganze Zahl von 1 bis 4,

    X eine Hydroxygruppe,

    oder ―NHSO2―R8, wobei R6 und R7 unabhängig voneinander für ein Wasserstoffatom oder eine gegebenenfalls substituierte Alkylgruppe stehen und R8 eine gegebenenfalls substituierte Alkylgruppe oder eine gegebenenfalls substituierte Arylgruppe darstellt;

    Y ein Wasserstoff- oder Halogenatom oder eine gegebenenfalls substituierte Alkylgruppe, eine Alkoxygruppe, eine Carboxylgruppe, eine Sulfogruppe, eine gegebenenfalls substituierte Carbamoylgruppe oder eine gegebenenfalls substituierte Sulfamoylgruppe bedeutet, wobei im Falle, daß m nicht weniger als 2 ist, die verschiedenen Reste Y gleich oder verschieden sein können;

    Z für eine Gruppe von einen gegebenenfalls substituierten carbocyclischen aromatischen Ring oder einen gegebenenfalls substituierten heterocyclischen aromatischen Ring bildenden Atomen steht;

    R5 ein Wasserstoffatom oder eine gegebenenfalls substituierte Amino- oder Carbamoylgruppe oder eine Carboxyl- oder Carboxyestergruppe darstellt und

    A' einer gegebenenfalls substituierten Arylgruppe entspricht;
    oder der Formeln:



    und

    worin X" für ein Halogenatom, eine Nitrogruppe, eine Cyanogruppe, eine Acylgruppe oder eine Carboxylgruppe steht, n = 0 oder eine ganze Zahl von 1 bis 4 und m = 0 oder eine ganze Zahl von 1 bis 6, entspricht.


     
    2. Aufzeichnungsmaterial nach Anspruch 1, dadurch gekennzeichnet, daß die Dicke der Ladung erzeugenden Schicht nicht mehr als 3 pm beträgt.
     
    3. Aufzeichnungsmaterial nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Dicke der Ladung transportierenden Schicht 5 pm bis 50 um beträgt.
     
    4. Aufzeichnungsmaterial nach Anspruch 3, dadurch gekennzeichnet, daß das Verhältnis (Tg:Tt) der Dicke der Ladung erzeugenden Schicht Tg zur Ladung transportierenden Schicht Tt 1 : (1 bis 30) beträgt.
     
    5. Aufzeichnungsmaterial nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Ladung transportierende Substanz aus einem Oxazol-, Oxadiazol-, Thiazol-, Thiadiazol-, Triazol-, Imidazol-, Imidazolon-, Imidazolidin- oder Bisimidazolidinderivat, einer Styryl- oder Hydrazonverbindung, einem Pyrazolin-, Oxazolon-, Benzothiazol-, Benzimidazol-, Chinazolin-, Benzofuran-, Acridin-, Phenazin-oder Aminostilbenderivat, Poly-N-vinylcarbazol, Poly-1-vinylpyren oder Poly-9-vinylanthracen besteht.
     
    6. Aufzeichnungsmaterial nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Ladung erzeugende Schicht die Ladung erzeugende Substanz in einer Menge von 20-50 Gew.-% des Bindemittels und die Ladung transportierende Substanz in einer Menge von 20-200 Gew.-% des Bindemittels enthält.
     
    7. Aufzeichnungsmaterial nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß das Gewichtsverhältnis Sg:St der Ladung erzeugenden Substanz Sg zur Ladung transportierenden Substanz St in der Ladung erzeugenden Schicht 1 : (2 bis 3) beträgt.
     
    8. Aufzeichnungsmaterial nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Ladung erzeugende Substanz in der Ladung erzeugenden Schicht in Form von Teilchen eines Durchmessers von weniger als 2 pm dispergiert ist.
     
    9. Verfahren zur positiven Aufladung unter Verwendung eines Aufzeichnungs materials nach einem der vorhergehenden Ansprüche.
     


    Revendications

    1. Photorécepteur comprenant une couche de support génératrice et une couche de support transporteuse, dans lequel ladite couche de support génératrice contient une substance de support génératrice dont la photosensibilité, lorsqu'elle est chargée negativement, est plus elevée que lorsqu'elle est chargée positivement, une substance de support transporteuse et un liant, et l'épaisseur de ladite couche de support génératrice est de 1 µm à 10 pm, et ladite couche de support transporteuse contient une substance de support transporteuse et un liant et est présente sur la surface inférieure de ladite couche de support génératrice, ladite substance de support génératrice répondant à la formule:











    ou

    dans laquelle

    Ar1, Ar2 et Ar3 représentent, chacun indépendamment, un radical carbocyclique substitué ou non substitué;

    Cp represente



    Z représente un groupe d'atomes formant un noyau carbocyclique aromatique substitué ou non substitué, ou un noyau hétérocyclique aromatique substitué ou non substitué; Y représente l'hydrogène, un groupe hydroxyle, un groupe carboxyle ou un groupe ester carboxylique, un groupe sulfo, un groupe carbamoyle substitué ou non substitué ou un groupe sulfamoyle substitué ou non substitué; R1 représente l'hydrogène, un groupe alkyle substitué ou non substitué, un groupe amino substitué ou non substitué, un groupe carbamoyle substitué ou non substitué, un groupe carboxyle ou un groupe ester carboxylique, ou un groupe cyano; Ar4 représente un groupe aryle substitué ou non substitué; et R2 represente un groupe alkyle substitué ou non substitué, un groupe aralkyle substitué ou non substitué ou un groupe aryle substitué ou non substitué;



    Ar5, Ar6 et Ar7 representent chacun independamment un radical aromatique carbocyclique substitué ou non substitué;

    A représente



    ou

    où n est 1 ou 2, m est 0 ou un nombre entier de 1 à 4, X' représente un groupe hydroxy,

    ou ―NHSO2―R6,

    où R4 et R5 représentent chacun indépendamment l'hydrogène ou un groupe alkyle substitué ou non substitué; et R6 represente un groupe alkyle substitué ou non substitué ou un groupe aryle substitué ou non substitué,

    Y' représente l'hydrogène ou un halogène, un groupe alkyle substitué ou non substitué, un groupe alcoxy, un groupe carboxy, un groupe sulfo, un groupe carbamoyle substitué ou non substitué ou un groupe sulfamoyle substitué ou non substitué, tel que si m n'est pas inférieur à 2, chaque Y' peut être identique ou différent;

    Z' represente un groupe d'atomes formant un noyau aromatique carbocyclique substitué ou non substitué ou un noyau aromatique hétérocyclique substitué ou non substitué; R3 représente l'hydrogène, un groupe amino substitué ou non substitué, un groupe carbamoyle substitué ou non substitué ou un groupe carboxyle ou un groupe ester carboxylique; et

    A' représente un groupe aryle substitué ou non substitué;







    Ar1, Ar2 et Ar3 représentent chacun indépendamment un noyau aromatique carbocyclique substitué ou non substitué;

    R1, R2, R3 et R4 représentent chacun indépendamment un groupe accepteur d'électron ou l'hydrogène, tel qu'au moins l'un de R1 à R4 soit un groupe accepteur d'électron;

    A est



    ou

    où n est 1 ou 2, m est 0 ou un nombre entier de 1 à 4, X représente un groupe hydroxy,

    ou ―NHSO2―R8, tel que R6 et R7 représentent chacun indépendamment l'hydrogène ou un groupe alkyle substitué ou non substitué; et R8 represente un groupe alkyle substitué ou non substitué ou un groupe aryle substitué ou non substitué,

    Y représente l'hydrogène ou un halogène, un groupe alkyle substitué ou non substitué, un groupe alcoxy, un groupe carboxyle, un groupe sulfo, un groupe carbamoyle substitué ou non substitué ou un groupe sulfamoyle substitué ou non substitué, tel que si m n'est pas inférieur à deux, chaque Y peut être identique ou différent;

    Z représente un groupe d'atomes formant un noyau aromatique carbocyclique substitué ou non substitué ou un noyau aromatique hétérocyclique substitué ou non substitué;

    R5 représente l'hydrogène, un groupe amino substitué ou non substitué, un groupe carbàmoyle substitué ou non substitué ou un groupe carboxyle ou un groupe ester carboxylique; et

    A' représente un groupe aryle substitué ou non substitué;



    et

    X" représente un halogène, un groupe nitro, un groupe cyano, un groupe acyle ou un groupe carboxyle;

    n est 0 ou un nombre entier de 1 à 4; et

    m est 0 ou un nombre entier de 1 à 6.


     
    2. Photorécepteur selon la revendication 1, dans lequel l'épaisseur de ladite couche de support génératrice est supérieure à 3 pm.
     
    3. Photorécepteur selon la revendication 1 ou 2, dans lequel l'épaisseur de ladite couche de support transporteuse est de 5 µm à 50 pm.
     
    4. Photorécepteur selon la revendication 3, dans lequel le rapport (Tg:Tt) de l'épaisseur de ladite couche de support generatrice, Tg, à l'épaisseur de ladite couche de support transporteuse, Tt, est de 1 :(1 à 30).
     
    5. Photorécepteur selon l'une quelconque des revendications précédentes, dans lequel ladite substance de support transporteuse est un dérivé d'oxazole, un dérivé d'oxadiazole, un dérivé de thiazole, un dérivé de thiadiazole, un dérivé de triazole, un dérivé d'imidazole, un dérivé d'imidazolone, un dérivé d'imidazolidine, un dérivé de bisimidazolidine, un composé styryle, un composé hydrazone, un dérivé de pyrazoline, un dérivé d'oxazolone, un dérivé de benzothiazole, un dérivé de benzimidazole, un dérivé de quinazoline, un dérivé de benzofurane, un dérivé d'acridine, un dérivé de phénazine, un dérivé d'aminostilbène, un poly-N-vinylcarbazole, un poly-1-vinylpyrène ou un poly-9-vinylanthracène.
     
    6. Photorécepteur selon l'une quelconque des revendications précédentes, dans lequel ladite couche de support génératrice contient ladite substance de support génératrice en une proportion de 20% à 50% en poids dudit liant et ladite substance de support transporteuse en une proportion de 20% à 200% en poids dudit liant.
     
    7. Photorécepteur selon l'une quelconque des revendications précédentes, dans lequel le rapport en poids, Sg:St, de ladite substance de support génératrice Sg à ladite substance de support transporteuse St dans ladite couche de support génératrice est de 1:(2 à 3).
     
    8. Photorécepteur selon l'une quelconque des revendications précédentes, dans lequel ladite substance de support génératrice est dispersée dans ladite couche de support génératrice sous la forme de particules dont le diamètre est inférieur à 2 pm.
     
    9. Procédé pour une électrisation positive, utilisant un photorécepteur selon l'une quelconque des revendications précédentes.
     




    Drawing