GB2246643A - Electrophotographic image forming process - Google Patents

Abstract

A method for forming an electrophotographic image which comprises: uniformly charging a photoreceptor comprising a conductive substrate having thereon a photoreceptive layer containing a phthalocyanine pigment; imagewise exposing the photoreceptor to light to form an electrostatic latent image; and developing the electrostatic image with a single component type magnetic toner; wherein the phthalocyanine (PC) pigment contains a greater percentage of adsorbed water than any other adsorbed gas, as determined by the adsorption gas analysis carried out in vacuum. The photoreceptor preferably has a charge-transport layer above the photoreceptive layer. The desired PC pigment is preferably produced by forming a wet paste of the pigment, adding organic solvent(s), stirring the solution for several hours, diluting with more organic solvent and filtering and drying.

Description

ELECTROPHOTOGRAPHIC IMAGE FORMING PROCESS FIELD OF THE INVENTION This invention relates to an image forming process performed in an electrophotography and particular y te image forming process capable of keeping an image quality excellent even under the conditions of a high ternperature and a high humidity.

BACKGROUND OF THE INVENTION Heretofore, as an electrophotographic developer, a component type developer comprising a non-magnetic toner and a magnetic carrier and a single-component type developer mainly comprising a magnetic toner have been used. The singlecomponent type developers have the advantages that they cannot be deteriorated by the fatigue of carrier because they do not need to use any carrier, that their compositions cannot be varied by the consumption and replenishment of toner and, in addition, that the replenishment and stirring mechanisms for the developer can be simplified.

Besides the above-mentioned advantages, the singlecomponent type developers also have another advantage that they can be transported and developed by means of a compact and miniature magnetic developing roller -which comprises a magnetic roller and a sleeve rotatable relatively around the outer circumference of the magnetic roller-, because they are the magnetic developers similar to the above-mentioned twocomponent type developers. It has, therefore, been studied to utilize them with a miniature sized copying machine or a printer.

There are tlo types of the single-component type developers, namely, a conductive developer mainly comprising a conductive magnetic toner for one and an dielectric developer mainly comprising an dielectric magnetic toner for the other.

The techniques of forming an image by making use of the conductive developer are described in, for example, Japanese Patent Examined Publication No. 56-2705/1981 and Japanese Patent Publication Open to Public Inspection -hereinafter referred to as Japanese Patent O.P.I. Publication- No. 5532059/1980.

The above-given Japanese Patent Examined Publication No.

56-2705/1981 discloses the technique in which the abovementioned conductive developer is transported by a magnetic development roller to a development area and a conductive path is formed between the magnetic roller and a photoreceptor, so that an image is developed in an inductive development system.

The above-given Japanese Patent O.P.I. Publication No. 5532059/1980 discloses the technique in which a conductive developer is transported by a magnetic development roller to a development area in the same manner as in the former technique and an image is contact developed in the development area in a low frequency oscillatory electric field.

Japanese Patent Examined Publication No. 56-46596/1981 discloses the technique in which the foregoing dielectric developer is transported by a magnetic development roller to a development area and an electrostatic latent image is contact developed on a photoreceptor. k, Japanese Patent C.y.

Publication No. 58-70257/1983 discloses the technique in which an dielectric developer is transported by a magnetic development roller to a development area in the same manner as in the former techniques and an electrostatic latent image is non-contact developed on a photoreceptor in an oscillatory electric field.

As described above, the single component type developers comprising mainly magnetic toner are utilized for forming an image in a contact development system and in a non-contact development system. They have the advantages that few damages or deteriorations are produced on a photoreceptor by scratching the photoreceptor in the contact development system, because the single component type developers do not contain any hard and large sized carrier. They have also the other advantages that a development gap can be narrowed in a non-contact development system and, therefore, a vias voltage for generating a development electric field can be lowered and the electrical damages of a photoreceptor can also be diminished.Because of the above-mentioned advantages, the above-described single component type developers are advantageous when they are used with a photoreceptor comprising a relatively soft organic photoconductive material in combination.

Heretofore, a selenium typ photoreceptor has so far been used popularly as an electrophotographlc photoreceptor. In recent years, an attention has been paid to a photoreceptor comprising an organic photoconductive material which can readily and inexpensively be prepared by applying a coatIng process thereto, hereinafter referred simply to as 'an organic photoreceptor.

For preparing the above-described organic photoreceptor, there are plenty of organic photoconductive materials available and the freedum of selecting them is great, so that any photoreceptors each having the different photoreceptivity and spectral wavelengths can readily be selected so as to satisfy various requirements.

Meanwhile, in electrophotographic industry, the image forming processes of digital system which are capable of performing an image-quality refinement, a working control and a document edition are being researched and developed energetically so as to replace the conventional analog system thereby.

In the above-mentioned analog system image forming processes, a visual image has been formed in the manner that, after optically scanning an original document image with an exposure lamp, a photoreceptor is exposed imagewise to the resulting reflected light so as to form an electrostatic latent image, and the latent image is developed to b a vIsual image. In contrast to the above, in te digital systems, a dot image is formed i the follow nag manner.After carrying out a series of a reading, a photoelectric conversion, an A/D conversion, and an image processing each of an optical information given fre an original document by making u e o a reading scanner so as to obtain an image signal, the rays of light emitted from a light source such as an LED, a liquid crystal shutter or a laser device is modulated by the image signal, and a photoreceptor is exposed spotwise to the modulated rays of light so that a dot-shaped electrostatic latent image can be formed and then developed to be the dot image.

In the above-described digital system, a dot image may be obtained by making use of a digital type copying machine equipped with such a scanner as described above, or by making use of a printer utilizing an external image signal given from a facsimile machine or a personal computer. In such case, a dot-shaped electrostatic latent image is formed by exposing spotwise to a 50-100 Am aperture-semiconductor laser beam usually modulated by an image signal and the image is developed in a reversal development system in which an exposed area only is developed.

When making use cf the above-mentioned single component type developer not containing any large sized carrier so as to form a dot image in the above-described reverses development system, there is an advantage that an image having a more excellent sharpness can be obtained as compared to the case of making use of a two-component type developer. It is also desirable to use an organic photoreceptor which is inexpensive in manufacturing cost and great in the freedum of selecting a photoreceptivity and in spectral wavelengths. It is particularly preferable to use a phthalocyanine photoreceptor having a spectral wavelength within the emission spectral range of 700 to 800 nm of a semiconductor laser beam ordinarily used for forming an image in the digital image forming system.

However, when making use of a photoreceptor containing an ordinary phthalocyanine pigment for forming a dot image in the above-mentioned digital image forming system, it has been discovered that the sharpness and image quality of the dot image are seriously affected by a temperature and a humidity of a surrounding atmosphere. When forming a dot image in the digital image forming system, it is required to make a PWM -a pulse width modulation- of a laser beam for improving the gradation of the dot image. In this instance, the beam pulse width is narrowed and, therefore, the photosensitivity of a photoreceptor is required to be made higher as much as the beam pulse width is narrowed.

It is, further, required to make the photosensitjvity of a photoreceptor more higher so as to meet the acce'e-ation of an image formation speed.

In the case where the photosensitivity of a photcreceptor is made higher, it has been discovered that a temperature and a hunidity of the above-mentioned surrounding atmosphere affect seriously in the quality of image formed on the photoreceptor.

SUMMARY OF THE INVENTION It is an object of the invention to provide an image forming process comprising the steps of making use of a single component type developer mainly comprising a magnetic toner, and providing an excellent image quality even in the conditions of a high temperature and a high humidity.

Another object of the invention is to provide an image forming process in which the density and resolving power of an image cannot be lowered and any background fog cannot be produced even in the conditions of a high temperature and a high humidity when forming the image by making use of the above-mentioned developer and a photoreceptor in a reversal development system.

This invention is a method for forming an electrophotographic image which comprises steps o uniformly charging an electrophotographic photoreceptor comprising a conductive substrate having thereon a photoreceptive layer containing a phthalocyanine pigment imagewise exposing to light the photoreceptor to form an electrostatic latent image, and developing the electrostatic latent image with a single component type magnetic layer, wherein the number cf water molecules determined by adsorption gas analysis made in vacuum is highest in the whole number of molecules of gases adsorbed by the phthalocyanine pigment.

BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1 through 6 are the cross sectional views each illustrating the layer arrangements of a photoreceptor; Fig. 7 is a schematic illustration of a digital image forming means relating to the invention; Fog. 8 illustrates a development apparatus; Fog. 9 illustrates an electrical potential explaining the mechanism of a reversal development; and Figs.

10 through 13 are the charts exhibiting the differential thermometric curves of the phthalocyanine pigments of each synthetic example.

DETAILED DESCRIPTION OF THE INVENTION The phthalocyanine pigments applicable to the image forming processes of the invention include, for example, the metallic or non-metallic phthalocyanines described in Japanese Patent O.P.I. Publication No. 62-79470/1987, and the titanyl phthalocyanine pigments described in Japanese Patent O..I.

Publication Nos. 61-239248/1986 and 62-67094/1987, when paying an attentIon only to the chemical structures of the pigments.

Among them, a vanadium phthalocyanine pigment and a titanyl phthalocyanine pigment are deemed preferable.

However, the phthalocyanine type pigments relating to the invention are different from the phthalocyanine type pigments described in the afore-given patent publications in the aggregation conditions of the pigment crystals. In particular, both of them can clearly be discriminated from the point that the water molecule content in terms of number of molecule is highest in the whole number of molecule of the gases adsorbed on the pigment crystals. The number of water molecule can be analyzed in an adsorption gas component analysis made in vacuum.

Therefore, the phthalocyanine pigments relating to the invention are different from the conventional ones in the preparation processes and, at the same time, in X-ray diffraction spectra and endothermic characteristics determined in a differential thermometric analysis, as well as they are greatly different from each other also in electrophotographic characteristics.

The above-mentioned analysis of gas components adsorbed on a phthalocyanine pigment is carried out in the following procedures.

An ampul made of a piece of glass tube having a volumetric capacity of 3.0 cm3 is charged with 0.5 g of a subject phthalocyanine pigment under the atmospheric conditions of a humidity of 50%, and the ampul is loaded on an analyzing chamber. The ampul containing the pigment is fractured at a vacuum degree of 2x10-8 Torr in the analyzing chamber, and the molecular weight of the gas discharged from the ampul is measured by making use of a quadrupole mass spectrometer, so that a component analysis can be made.

Besides the water molecule adsorbed on phthalocyanine coated over a photoreceptive drum can be measured in the following procedures.

A drum coated with a photoreceptive layer containing phthalocyanine is dipped in methanol being kept at an ordinary temperature and the photoreceptive layer is then separated from the substrate of the drum. The photoreceptive layer separate from the substrate is dissolved in methylene chloride, and the resulting insoluble matters are filtrated through a sheet of filter paper. The resulting filtrates are washed well with methylene chloride having a purity of not lower than 98%. The deposits remaining on the filter paper are taken and dispersed in butyl acetate having a purity of not lower than 98i. The resulting insoluble titanyl phthalocyanine is then separated and picked up by making use of a centrifugal separator.

The resulting titanyl phthalocyanine was washed and dried up by heating at a tempertur of l20C, and the water molecules adsorbed thereon are measured in the afore-mentioned procedures.

From the above-described component analyses of the phthalocyanine pigment, each component such as water, hydrogen, nitrogen, oxygen and carbon dioxide may be detected.

The phthalocyanine pigments relating to the invention are characterized in containing the most numerous water molecules.

From the viewpoints of a photosensitivity and the characteristics of repetition use, the phthalocyanine pigments relating to the invent Ion are desirable to have an endothermic peak within the range of 80'C to 120'C in a differential thermal analysis. The above-mentioned differential thermal analyses are performed by making use of 10 mg of a phthalocyanine pigment under the atmospheric conditions of a humidity of 60% and a temperature raising rate of 10'C per minute. The above-mentioned endothermic peak is to be not lower than 30 degrees in terms of the half width.

Taking a titanyl phthalocyanine pigment as a typical example, the characteristics of the pigments relating to the invention will further be detailed below.

Any one of the typical titanyl phthalocyanine pigments relating to the invention has the following structure, and the X-ray diffraction spectrum of Cu-Ka rays has peaks at Bragg angle 26 of 9.5 + C.2 and 27.2 + 0.2 .

wherein X1, X2, X3 and X4 represent each a hydrogen atom, a halogen atom, an alkyl group or an alkoxy group; and n, m, Q and k are each an integer of 0 to 4.

The above-mentioned titanyl phthalocyanine pigments can be prepared in the following procedures. First, 3 diminoisoindoline is mixed with a sulfolane solvent and, next, titanium tetrapropoxide is added thereto, and the resulting mixture is reacted under the nitrogen atmospheric conditions.

The reaction temperature at this instance is within the range of 80'C to 300 C and, preferably, 100-C to 260'C. After completing the reaction and then cooling the reactant, the deposits are taken through a filtration, so that an aggregated titanyl phthalocyanine pigment such as those in the state described in the foregoing Japanese Patent O.P.I. Publication No. 61-239248/1986 can be obtained.

The titanyl phthalocyanine pigments relating to the invention can be obtained in the following manner. After the above-mentioned resulting pigment is subjected to an acid- paste treatment, It is further subjected to a mixing treatent with stirring n a Fed solvent so as to modify the aforementioned aggregated state of the pigment crystals into a different aggregated state, thereby obtaining the objective pigment.

The apparatuses applicable to the above-mentioned mixingstirring treatment include, for example, a homomixer, a disperser, an agitator, a ball mill, a sand mill, and an attriter, as well as any one of ardinary types of stirrers.

Thus, it may be presumed that the resulting aggregates of the pigment crystals take a large number of water molecules thereinto and, resultinly, the X-ray diffraction spectra and endothermic characteristics may peculiarly be displayed. In addition to the above, when a photoreceptor is produced of a titanyl phthalocyanine pigment comprising an aggregate taken a large number of water molecules thereinto, it may also be presumed that a high moisture resistance and a high photoreceptivity can be displayed and peculiar light absorption characteristics can also be displayed. The abovementioned light absorption characteristics mean that a light absorption spectrum is in a near infrared region within the range of 780 nm to 860 nm.When this is the case, a remarkably high photosensitive characteristics can be displayed when making use of semiconductive laser beams which are commonly used with digital copying machines or prInters.

When an organic photoreceptor is constituted by makIng use of a photoconductive material comprising the aforementioned phthalocyanine pigment relating to the invention, the photoconductive material can function as a carrier generating material capable of absorbing light so as to producing carriers.

The above-mentioned carrier generation materials of the photoreceptors relating to the invention can be used with not only the phthalocyanine pigments relating to the invention but also the other carrier generating materials in combination, provided that the effects of the invention cannot be spoiled.

The above-mentioned other combinedly applicable carrier generating materials include, for example, the ordinary types of metallic or non-metallic phthalocyanine pigments such as those described in the aforegiven Japanese Patent O.P.I.

Publication No. 62-79470/1987, the a and ss types of titanyl phthalocyanine pigments such as those described in Japanese Patent O.P.I. Publication Nos. 61-239248/1986 and 6267094/1987, azo type pigments, anthraquinone pigments, perylene pigments, polycyclic quinone pigments, and squarylium pigments.

The photoreceptors relating to the invention can be prepared in the following procedures. For example, the abovedescribed phthalocyanine pigment relating to the invention is mixeuly dispersed in a solution prepared by dissolvir.a a binder resin in a solvent. A coating solution is then prepared by dissolving the later-mentioned carrier transport material in the resulting solution. The resulting coating solution is coated on a conductive support provided in advance with an interlayer or a sublayer if required, in such a coating method as a dip-coating method, a spray-coating method, and a spiral-coating method, so that the photoreceptor can be prepared. In the above-described procedures, the single layer structured photoreceptors shown in Fig. 1 and 2 can be prepared.In the figures, reference numeral 1 indicates a conductive support, 4 indicates a single photoreceptor layer structure, and 5 indicates an interlayer.

However, from the view point of obtaining a photoreceptor having a high photosensitivity and a high durability, the photoreceptor is desirably to have a function-separated multilayered structure such as those shown in Fig. 3 and 4.

When this is the case, a coating solution, which comprises the foregoing pigment mixedly dispersed in a binder resin containing solution, is coated over conductive support 1 provide thereonto, if required, with interlayer 5, so that carrier generation layer 2 can be formed, and a coating solution containing a carrier transport ion material is then coated over the resulting carrier generation layer 2, so that carrier transportion layer 3 can be laminated on carrier generation layer 2. In the above-described procedures, photoreceptive layer 4 having a double layered structure (see Figs. 3 and 5), or photoreceptive layer 4 having an inverted layer structure (see Figs. 4 and 6), can be formed.

The photoreceptors will now be detailed, with priority given to those having a double-layered structure.

When forming a double layered photoreceptor, carrier generation layer 2 and carrier transportion layer 3 may be provided thereonto in either one of the following methods.

(a) A method in which a solution wherein each of a carrier generation material and a carrier transport ion material is dissolved in a suitable solvent, or a solution wherein a binde is further added to the aforesaid solution is coated to be the carrier generation layer and the carrier transportion layer, respectively.

(b) A method wherein a each of a carrier generation material and a carrier transportion material is pulverized into fine particles in each dispersion medium to make a dispersion by a ball mill, a homomixer or a supersonic homogenizer, and is further given a binder, if necessary, for the dispersion and resulting dispersion is coated to be the carrier generation layer and the carrier transportion layer, respectively.

The solvents or the dispersion media each applicable or forming the above-mentioned carrier generation layer and the carrier transportior. layer are include, for example, butylamine, N,N-dimethyl formamide, acetone, methyl ethyl ketone, cyclohexanone, benzene, toluene, xylene, chloroform, 1,2-dichlorethane, dichloromethane, tetrahydrofran, dioxane, methanol, ethanol, isoprDpanol, ethyl acetate, butyl acetate, and dimethyl sulfoxide. When making use of a binder for forming either a carrier generation layer or a carroer transportion layer, any desired binders may be used for.

Among them, it is prtlcularly preferable to use a high molecular polymer which have a hydrophobic property and a high dielectric constant and is capable of forming an electrically dielectric film. The above-mentioned polymers may include the following ones, for example.

1) polycarbonate 2) polyester 3) methacrylic resin 4) acrylic resin 5) polyvinyl chloride 6) polyvinylidene chloride 7) polystyrene 8) polyvinyl acetate 9) styrene-butadiene copolymer 10) vinylidene chloride-acrylonitrile copolymer 11) vinyl chloride-vinyl acetate copolymer 12) vinyl chloride-vinyl acetate-maleic anhydride copolymer 13) silicone resin 14) silicone-alkyd resin 15) phenol-formaldehyde resin 16) styrene-acryl copolymeric resin 17) styrene-alkyd resin 18) poly-N-vinyl carbozole 19) polyvinyl butyral 20) polycarbonate Z resin The above-given binders may be used independently or in combination.

The proportions of the carrier generation material to the binder resin is within the range of, desirably, 10 to 600 wt% and, prteferably, 50 to 400 wt%.

The thickness of the carrier generation layer 2 provided as described above is within the range of, desirably, 0.01 to 20 pin and, preferably, 0.05 to 5 pin.

When carrier generation layer 2 is formed by dispersing the above-mentioned carrier generation material, the carrier generation material is desirable to be in the form of powder having an average particle size of not larger than 2 pin and preferably not larger than 1 pin.

A variety of the carrier transport materials can be used in the invention. Among them, the cypical examples thereof include the compounds eafirl having a nitrogen-containing hetercyclic nucleus and the condensed cyclic nucleus thereof typified by oxazole, oxadiazole, thiazole, thiadiazole and imidazole, a polyaryl lane type compound, a pyrazoline type compound, a hydrazone type compound, a triarylamine type compound, a styryl type compound, a styryltriphenylamine type compound, an a-phenylstyryltriphenylamine type compound, a butadiene type compound, a hexatoluene type compound, a carbazole type compound and a condensed polycyclic type compound.

The typical examples of the carrier transport materials may include those described in Japanese Patent O.P.I.

Publication No. 61-107356/1986.

The proportion of the carrier transport material to the binder resin is within the range of, desirably, 10 to 500 wt%.

The thickness of the carrier transport layer is within the range of, desirably, 1 to 100 Am and, preferably, 5 to 30 pin.

Each of photoreceptive layers 4 of the photoreceptors of the invention are allowed to contain an electron receptive material, for the purposes of improving a photosensitivity, reducing a residual potential, diminishing the fatigue produced in repetition use of the photoreceptors. The abovementioned electron receptive materials incLude, for example, succinic anhydride, maleic anhydride, dibromosuccinic anhydride, phthalic anhydride, tetrachlorophthalic anhydride, tetrabromophthalic anhydride, 3-nitrophthalic anhydride, 4nitrophthalic anhydride, pyromellitic anhydride, mellizic anhydride, tetracyanoethylene, tetracyanoquinodimethane, odinitrobenzene, m-dinitrobenzene, 1,3,5-trinitrobenzene, pnitrobenzonitrile, picryl chloride, quinonechloramide, chloranyl, bromanyl, dichlorodicyano-p-benzoquinone, anthraquinone, dinitroanthraquinone, 9-fluorenylidene malonodinitrile, polynitro-9-fluorenylidene malonodinitrile, picric acid, o-nitrobenzoic acid, p-nitrobenzoic acid, 3,5dinitrobenzoic acid, pentafluorobenzoic acid, 5-nitrosallcylic acid, 3,5-dinitrosalicylic acid, phthalic acid, mellitic acid, and other compounds having a substantial electron affinity.

The electron receptive materials are to be added in an amount within the range of, desirably, 0.01 to 200 wt parts and, preferably, 0.1 to 100 wt parts thereof, each per 100 wt parts of a carrier generation material used.

Further, the above-mentioned photoreceptive layer 4 is allowed to contain an antideteriorating agent such as an antioxidant and an optical stabilizer, for the purposes of improving a preservability and a durability of the photoreceptor.

In the single layer structured photoreceptcrs such as those shown in Figs. 1 and 2, the carrier generation materIal applicable to photoreceptive layer 4 is a phthalocyanine pigment relating to the invention, and the carrier transportion material applicable thereto can be selected from those given above. The binder resins and the other ..açeYials added thereto may be the same as given above.

The aforementioned conductive supports include, for example, a metal plate, a metal drum, a conductive polymer, conductive compounds such as indium oxide, and those provided by coating, evaporating or laminating a thin layer made of a metal such as aluminium or palladium on a sheet of paper or plastic film.

The aforementioned interlayers 5 each applicable thereto, which are capable of functioning as an adhesive layer or a barrier layer, include, for example, a high molecular polymer such as those described as the above-mentioned binder resins, an organic high molecular substance such as polyvinyl alcohol, ethyl cellulose, carboxymethyl cellulose and polyamide, and aluminium oxide.

As described before, the single component type developers each comprising mainly the magnetic toners relating to the invention may be conductive single component type developers each comprising mainly the conductive magnetic toner.

However, dielectric single component type developers may desirably be used, because highly resolved images can be obtained by their excellent developability and, in particular, by their excellent image transferability. The above-described dielectric magnetic toners each mainly comprise both binder resin and magnetic powder and, if required, they contain a colorant and/or an electric charge controlling agent. The volumetric resistance of such a toner is within the range of, desirably, not less than 1012 Qcm and, preferably, not less than 1014 Qcm.

The above-described binder resins suitably applicable thereto include, for example, styrene resins such as polystyrene and polyparachlorostyrene; acrylic resins each comprising methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, methyl methacrylate, ethyl methacrylate or butyl methacrylate, independently or the copolymers thereof; vinyl resins each comprising vinyl chloride, vinyl bromide, vinyl fluoride, vinyl acetate, vinyl propylenate, vinyl benzoate or vinyl lactate, independently or the copolymers thereof; vinyl ether resins each comprising vinyl methyl ether, vinyl isobutyl ether or vinyl ethyl ether, independently or the copolymers thereof; vinyl ketone resins each comprising vinyl methyl ketone or vinyl hexyl ketone, independently of the copolymers thereof;N-vinyl resins each comprising N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole or N-vinyl pyrrolidone, independently or the copolymers thereof; and one or more kinds of the mixtures or the copolymers selected from the group consisting of rhosinmodified phenol formalin resin, oil-modified epoxy resin, polyurethane resin, cellulose resin, vinyl resin, epoxy resin, cellulose resin and polyurethane resin.

The above-mentioned colorant have so far been used in electrophotographic toners. These colorant include, for example, carbon black, a nigrosine dye, aniline blue, chalcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow and the mixtures thereof. However, when the foregoing magnetic materials can function as a colorant, the above-given colorants may not necessarily be added.

The charge controlling agent desirably applicable thereto include, for example, Fettschwarz HBN -Color Index No. 26150-, alcohol-soluble nigrosine -Color Index No. 50415-, Sudan chiefschwarz BB -Color Index No. 26150-, and Chromogenschwarz ETCO -Color Index No. 14645-.

The foregoing dielectric magnetic toner can be prepared in any one of the following processes; namely, a process in which, after a binder resin, a magnetic material in a proportion within the range of 30 to 70 wt% of the toner to be used, and a colorant and/or a charge controlling agent in a proportion within the range of 0 to 5 wt% of the toner are each mixedly kneaded with heating by making use of a doubleroller mill, the resulting kneaded mixture is pulverized and classified by making use of a bail-mill or a jet pulverizer and is then hot-air treated at a temperature not lower than the softening point of the toner resin by making use of one of rotary spray driers including, preferably, that disclosed in, for example, U.S.Patent No. 3,338,991, so that the spherical toner can be prepared; another process in which, after an organic solvent comprising toluene, acetone or ethyl acetate is added into each of the above-described raw materials of toner and the mixture is then mixedly dispersed by making use of a ball-mill, the resulting dispersion is hot-air treated at a temperature not lower than the softening point of the resin used and is then granulated in, for example, a rotary spray drying method, so that the toner can be prepared; or, a further process in which, after the afore-mentioned magnetic powder and, if required, a colorant and/or a charge controlling agent, are so mixedly added into a resin monomer as to be dispersed together, the resulting dispersion is polymerized with stirring in the presence of a polymerization starter, so that the spherical toner can be prepared.

The resulting toners can display an excellent fluidity in a processing apparatus, because each of them is shere-shaped.

However, such a sphere-shaped tone has not always been satisfactory from the viewpoints of developability and cleaning property. Therefore, a toner can be obtained by improving the surface of the toner particles so as to be suitable for developability and cleaning property, when the raw materials of the toner is, mIxed, kneaded with heating, pulverized and stirred at a high speed by making use of an impact type stirrer -i.e., a hybridizer-.

As for the magnetic materials suitable for the abovementioned magnetic powder, the following materials, for example, can be used; namely, the metals such as cobalt and nickel; the alloys or the compounds including, typically, ferrite, magnetite and hematite, which contain the elements such as iron, cobalt and nickel each capable of showing a ferromagnetism; the alloys not containing any ferromagnetic material but capable cf sowing ferromagnetism when they are suitably treated by applying heat, which include, for example, a Heusler's alloy containing manganese and copper, such as a manganese-copper-aluminium alloy and a manganese-copper-tin alloy; or, chromium dioxide.

The volume resistivity of such a toner can be measure in the following procedures. After tapping the subject toner particles in a vessel having an effective cross section of 0.5 cm2, a load of 1 kg/cm2 is applied onto the particles filled in and a voltage is then applied between the load and a base electrode so as to produce an electric field within the range of 102 to 105 V/cm. The generated current value is read and calculated in the specified method, so that the volume resistivity can be obtained. In this instance, the thickness of toner particle layer is to be of the order of 1 mm.

The developers each principally comprising the abovementioned dielectric magnetic toner are allowed to contain hydrophobic silica as a fluidity improving agent in a proportion within the range of 0 to 3.0 wt% of the toner contained therein.

When the developer of the invention is a single component type developer principally comprising electroconductive magnetic toner, the developer is prepared either by containing metallic powder such as those of aluminium, nickel, cobalt and copper or a conductive member such as that of carbon black in the above-mentioned conductive magnetic toner, or by making conductive powder adhered to the surfaces of the toner particles by making use of the hybridizer described in the case of preparing the aforementioned dielectric magnetic toner. In this case, the volume resistivity of the toner is to be normally not higher than 1010 Qcm and preferably not higher than 108 Qcm.

Now, the image forming process of the invention will be detailed below with reference to the image forming apparatus shown in Fig. 7, the development apparatus shown in Fig. 8, and the illustration of a development mechanism shown in Fig.

9.

The image forming apparatus shown in Fig. 7 is roughly classified into original document reading section A, writing section B and image forming section C. In the reading section A, original document 12 placed on platen 11 is optically scanned through light source 13 and reflecting mirrors 14a, 14b and 14c. The resulting optical information is focussed on photoelectric conversion element 30 through lens 15 so as to convert the optical information into an electric signal. The electric signal is subjected to an image processing such as an A/D conversion treatment and then to be multivalued through signal processing apparatus 31, so that an image signal can be obtained and the image signal can be output to writing device 32 in writing section B to which an LED or a laser device is provided.It is usual that a semiconductor laser is modulated imagewise by the above-mentioned image signal, and the resulting modulated laser beams are scanned linearwise through a polygonal mirror and then exposed spotwise on phthalocyanine photoreceptor drum 20 relating to the invention. On the photoreceptor drum 20 is uniformly charged in advance by charger 16, and a dot-shaped electrostatic latent image is formed thereon by making the above-mentioned spot exposure.

The resulting electrostatic latent image is either contact or non-contact treatment in a reversal developing process, in an oscillatory electric field, by developing device 17 containing developer D principally comprising dielectric magnetic toner, and toner adheres to the spot exposed areas, so that the dot- shaped image can be formed on photoreceptor 20. The resulting toner image is electrostatically transferred by transfer electrode 18 to a sheet of transfer paper which is taken out of paper feeding cassette 23 by paper feed roller 24 and is then transported by register roller 25 while keeping welltimed with the image formation process. After then, the resulting toner image-formed transfer paper is separated from drum 20 by separation electrode 19.

After the transfer paper separated from drum 20 is transported to fixing section 27 by transport member 26 and is then heated and fixed there, the paper is ejected to paper receiving tray 29. After completing the transfer operation, the surface of photo-eceptor drum 20 is cleaned up by cleaning blade 21a of cleaning device 21 so that the next image formation can be ready to operate.

Fig. 8 illustrates an example of the above-described reversal developing apparatuses 17. In the figure, a developer replenisher is replenished from developer replenishing hopper 171 into development chamber 173 and the developer replenisher and developer D having been contained in development chamber 175 are mixed up together while stirring with stirring rollers 174 and 175 so as to be supplied for a development carried out with. development roller 176. In this case, development roller 176 is comprised of an N/S alternative fixed magnet 176a and a sleeve 176b rotatable to the direction of the arrow mark wit respect to the magnet 176a. Magnet 176a magnetloally attracts developer D contained in development chamber 173 and transports developer D to development area K.Then, developer D develops an electrostatic latent image on photoreceptor drum 20 being rotated in the direction of the arrow mark. Developer D having been attracted to the above-mentioned development roller 176 is regulated to be a 50 to 500 pin-thick thin developer layer by layer thickness regulating member 177. The electrostatic latent image is then treated in either contact or non-contact reversal development process on photoreceptor drum 20 in the presence of an oscillatory electric field generated in development area K, so that the latent image can be visualized.

In the case of carrying out the above-mentioned noncontact reversal development process, a gap is interposed between the developer layer in the development area and photoreceptor drum 20 so as to arrange them in a non-contact state, and the development is carried out by flying toner from the sleeve surface to the drum surface of the photoreceptor so that the development can be performed. Therefore, a gap -Dsdis provided to be within the range of 100 to 1000 pin between sleeve 176b and photoreceptor drum 20, and an AC bias having an amplitude -VA- within the range of 0.5 to 5 KV (p-p) and a frequency -f- within the range of 0.1 to 3 Khz is applied from power source 22a to sleeve 176b.Further, with overlapping the AC bias, a DC bias having a voltage -VD- within the range of 300 to 600 V is applied from power source 22b, and a DC development electric field and an oscillatory electric field are generated in the development area so that a development can be performed. In the figure, 178 is a scraper for scraping the magnetic toner remaining on the sleeve after completing the development, into development chamber 173. A surface potential -VH- of the photoreceptor drum is ordinarily to be within the range of 300 to 800 V.

Next, Fig. 9 illustrates a mechanism of the abovedescribed reversal development process. As shown in this figure, the surface potential VH (V) of a photoreceptor drum is light decayed by light irradiation to be lowered to VL (V).

Sleeve 176b is applied with a DC bias potential VD (V) and the reversal development is mainly progressed by the difference (VD-VL) (V) - between the aforementioned DC bias potential VD- and light decayed potential VL (V) . In other words, for example, negativelu polarized magnetic toner having been provided onto sleeve 176b with a potential VD (V) is made adhered to an exposed area, so that a reversal development can be achieved. The magnetic toner adhered to sleeve 176b by a magnetism can be releasea from the magnetical attraction by the function of an AC bias VA(p-p).

As described above, in the image forming process of she invention, an image can be formed by making use of a photoreceptor comprising specific phthalocyanine pigment, as a carrier generating material containing the most numerous water molecules in the --dsorptlve gas components of tne pigment and by also making use of, if required, a single component type developer principally comprising an dielectric magnetic toner, preferably in either a contact or non-contact reversal development system. Thereby, an image having a high density and high resolving power can constantly be obtained even in the condition of a high temperature and a high humidity.

[Examples] The invention will be detailed concretely with reference to the examples including the inventive and comparative tests Syntheses of phthalocyanine pigments: < Synthesis example 1 > To a mixture of 29.2 g of 1,3-diiminoisoindoline and 200 mQ of sulfolane, 17.0 g of titanium tetraisopropoxide was added, and the resulting matter was reacted under the nitrogen atmosphere at a temperature of 140 C for 2 hours. After cooling the reactant, the resulting deposits were filtrated and washed with chloroform and further washed wlth an aqueous 28 hydrochloric acid solution.Next, after washing with water and further washing wit; methanol, the filtrate was dried, so that 25.5 g, 88.5, of t-a.ly phthalocyanlne could be obtained. The resulting product of 100 g was dissolved in 2 kg of concentrated sulfuric acid. The solution was poured into 20 liters of water and the reslting deposit was filtrated, so that an amorphous wet paste could be obtained.

A mixed solvent of 200 me of 1,2-dichlorethane and 100 me of methanol was added to 2 g of the resulting wet paste and the mixture thereof was stirred at room temperature for 3 hours. The mixture was diluted with methanol and filtrated.

The filtrate was washed with methanol and dried, thereby obtaining the crystals each having a Bragg's angle of 26 of 9.5 + 0.2 and a peak of 27.2 + 0.2 in the X-ray diffraction spectrum. The X-ray diffraction spectra were measured by making use of an X-ray diffractometer, JDX-8200 manufactured by Japan Electron Co., under the following conditions. -and so forth X-ray tube Cu -Cu-Ka rays Voltage 40.0 KV Current 100.0 mA Start angle 6.00 deg.

Stop angle 35.00 deg.

Step angle 0.020 deg.

Measurement time 0.50 deg./min From the differential thermal analysis of the resulting crystals, the differential them 1 curves were obtained as shown in Fig. IC d the endothermic peak was observed t 99.E C. The differential thermal analysis was carried out in the afore-described method.

< Synthesis example 2 > To a mixture of 29.2 g of 1,3-diiminoisoindoline and 200 me of sulfolane, 17.0 g of titanium tetraisopropoxide was added, and the resulting matter was reacted under the nitrogen atmosphere at a temperature cf 140 C for 2 hours. After cooling the reactant, the resulting deposits were filtrated and washed with chloroform and further washed with an aqueous 2% hydrochloric acid solution. Next, after washing with water and further washing with methanol, the filtrate was dried, so that 25.5 g, yield 88.5%, of titanyl phthalocyanine could be obtained.

The resulting product of 100 g was dissolved in 2 kg of concentrated sulfuric acid. The solution was poured into 20 liters of water and the resulting deposit was filtrated, so that an amorphous wet paste could be obtained.

A mixed solvent of 200 mQ of 1,2-dichlorethane and 100 mQ of methanol was added to 2 g of the resulting wet paste and the mixture thereof was stirred at room temperature for 3 hours. The mixture was diluted with methanol and filtrated.

The filtrate was washed with methanol and dried, thereby obtaining the crystals each having a Bragg's angle of 20 of 9.5 + 0.2 and a peak of 27.2 + C.2 in the X-ray diffraction spectrum. And, from the differential thermal analysis of the resulting crystals, the differential endothermic curves were obtained as shown in Fig. 11.

< Synthesis example 3 > 1,3-diiminoisoindoline of 14.6 g, 0.1 mols, and vanadium oxide acetyl acetonate of 7.95, 0.03 mols, were mixed in 100 mQ of a-chloronaphthalene, and the mixture was reacted together at a temperature of 190-C for 2 hours. After the reactant was cooled down to room temperature, the resulting deposit was filtrated and washed with a-chloronaphthalene.

Next, the deposit was washed, successively, with chloroform, an aqueous 2% hydrochloric acid solution, water and, finally, methanol, respectively, and it was dried up, so that 11.0 g of vanadyl phthalocyanine could be obtained. Next, the resulting products was dissolved in a 30-fold amount of concentrated sulfuric acid. The resulting solution was poured into a 300fold amount of water and the resulting deposit was filtrated, so that an amorphous wet paste could be obtained.

The resulting wet paste of 2 g was added with a mixed solvent comprising 200 b of 1,2-dichlorethane and 100 mQ of methanol, and the solution was stirred at room temperature for 3 hours. The resulting matter was diluted with methanol and filtrated. The filtrate was washed with methanol and then dried, so that the crystals showing the differential endothermic curves could be obtained as shown in Fig. 12.

< Synthesis example 4 > In the same manner as in synthesis example 3, 2 g of amorphous titanyl phthalocyanine wet paste was added therein with a mixed solvent comprising 2C0 X of , I, 2-dlchlorethane and 50 me of water, and the resulting solution was stirred at a temperature of 60'C for 4 hours. Next, the resulting matter was diluted with methanol and the filtrated. The resulting filtrate was washed with methanol and then dried, so that the crystals could be obtained.

< Synthesis example 5 > In the same manner as in synthesis example 3, the amorphous titanyl phthalocyanine wet paste was washed and dried. Then, 12 parts of the dried titanyl phthalocyanine, 18 parts of sodium chloride and 8 parts of diethylene glycol were mixed up and the mixture was milled by heating at a temperature of 80'C for 60 hours in an automatic mortar.

Next, the resulting processed matter was washed with water and dried under reduced pressure. After that, one part of the dried matter was added therein with 20 parts of cyclohexane and 2 parts of glass beads so as to be dispersed together by means of a sand grinder for one hour. The resulting dispersion was filtrated and dried, so that the crystals could be obtained.

< Comparative synthesis example 1 > After drying the same wet paste as in synthesis example 1, a-chloronaphthalene was added thereinto and stirred with heating, so that type titanyl phthalocyanine could be obtained. In the X-ray diffraction spectra thereof, the peaks were at the Bragg's angles 20 of 9.3 + 0.2 , 10.6 + 0.2 , 13.2 # 0.2 , 15.1 # 0.2 , 15.7 # 0.2 , 16.1 , # 0.2 , 20.8 + 0.2 , 23.3- + 0.2 , 26.3- + 0.2 and 27.1 + 0.2. The endothermic curves are shown in Fig. 13.

< Comparative synthesis example 2 > In the same manner as in synthesis example 3, 2 g of amorphous titanyl phthalocyanine wet paste was added therein with a mixed solvent comprising 200 me of 1,2-dichlorethane and 100 me of F2O, and the resulting solution was stirred at a temperature of 80'C for 4 hours. Next, the resulting matter was diluted with methanol and the filtrated. The resulting filtrate was washed with methanol and then dried, so that the crystals could be obtained.

Each of the titanyl phthalocyanine and vandyl phthalocyanine having been obtained in the above-described synthesis examples 1 through 5 and comparative synthesis examples 1 and 2 was vacuum-analyzed into the adsorbed gas components in the aforementioned method. The results thereof are as follows:: Number of molecules (W) H2 H2O CO N2 O2 CO2 Synthesis example 1 2.2 68.5 0.0 23.3 4.2 1.8 2 2.C 5.3 0.0 o1.3 5.6 1.8 3 2.0 50.8 0.0 38.5 7.0 1.7 4 2.3 .3.5 0.0 42.2 9.3 2.5 5 1.8 63.4 0.0 27.5 5.3 2.0 Comparative synthesis example 1 0.0 2.6 0.0 79.5 13.9 4.0 2 2.7 34.7 0.0 47.0 12.2 3.4 It can be proved that the titanyl phthalocyanine and vanadyl phthalocyanine obtained in synthesis examples 1 through 5 are each have the most numerous water molecule content.

< Preparation of photoreceptors for test Nos. 1 to 3 > A polymeric polyamide, 'Lackamide 5003' manufactured by Dai-Nippon Ink Co., of 3 parts, hereinafter referred to as a part or parts by weight, was dissolved with heating into 100 parts of methanol, and the resulting solution was filtrated through a 0.6 Rm-mesh filter. The resulting filtrate was coated over a 60mm-#-sized aluminium drum in a penetration coating process, so that a 0.5 Am-thick syblayer could be provided thereonto.

On the other hand, a dispersion was prepared by dispersing 3 parts of the titanyl phthalocyanine re a'-ng to the invention obtained in synthesis example 1, 3 parts of the solids of a cellulose-modified silicone resin, 'KR-5240' manufactured by Shinetsu Chemical Co., for a binder resin, and 100 parts of methylisobutyl ketone for a dispersion medium altogether by making use of a sand mill. The resulting dispersion was coated over the previously coated sub aye in a penetration coating process, so that a 0.2 Am-thick carrier generation layer could be provided.Next, a solution was prepared by dissolving 1 part of the following carrier transport material T-l, 1.5 parts of a polycarbonate resin 'Eupiron Z 200' manufactured by Mitsubishi Gas Chemical Co., and a small amount of silicone oil 'KF-54' manufactured by Shinetsu Chemical Co. into 10 parts of 1,2-dichlorethane. The resulting solution was penetratingly coated over the previously coated carrier generation layer and dried, so that a 25 Wm-thick carrier transportion layer could be provided and, thereby the negatively chargeable photoreceptors for test Nos. 1 through 3 each relating to the invention could be obtained.

< Preparation of photoreceptors for test Nos. 4 to 6 The photoreceptors relating to the invention, which are subject to test Nos. 4 to 6 were each obtained in the same manner as in the photoreceptor for test No. 1, except that the titanyl phthalocyanine pigment prepared in synthesis example 2 was used in place of the titanyl phthalocyanine pigment prepared in synthesis example 1.

< Preparation of photoreceptors for test Nos. 7 to 9, 10 to 12 and 13 to 15 > The negatively chargeable photoreceptors relating to the invention, which are subject to test Nos. 7 to 9, 10 to 12 and 13 to 15 were each obtained in the same manner as in the photoreceptor for test No. 1, except that the vanadium phthalocyanine pigment prepared in synthesis example 3, 4 and 5 were used in place of the titanyl phthalocyanine pigment prepared in synthesis example 1, respectively.

< Preparation of photoreceptors for test Nos. 16 to 17 and 18 to 19 > The negatively chargeable photoreceptors relating to the invention, which are subject to test Nos. 16 to 17 and 18 to 19 were each obtained in the same manner as in the photoreceptor for test No. 1, except that the comparative phthalocyanine pigments prepared in comparative synthesis examples 1 and 2 were used in place of the titanyl phthalocyanine pigment prepared in synthesis example 1, respectively.

Preparation of developer for test purpose: < Preparation of developers for test Nos. 1, 4, 7, 10 and 13 > Polyester resin -'Dialeck NB/SC', mfd. by Diamond-Schamrock Co.- 240 g Triiron tetraoxide 'MAPICO black', mfd. by Columbia Carbon Co. 103 g -30 wt% in the toner The above-given compositions were well mixed by making use of a ball mil extending for 5 hours and were then mixedly kneaded together by making use of a double-roller kneader at a temperature of 170-C. Then, after spontaneously cooling it, the resulting matter was roughly ground by making use of a cutter mill and was pulverized by making use of a jet-air type fine pulverizer.After then, the pulverized matter was treated by making use of a hybridizer -or, an impact type surface treating apparatus- for 3 minutes and was then classified by making use of an air-classifier, so that negative polar type dielectric toner having an average particle size of 10 pin could be obtained. Hydrophobic silica in a proportion of 0.2 wt% was added from the exterior into the resulting toner, so that the developers for test Nos. 1, 4, 7, 10 and 13 each relating to the invention could be obtained.

< Preparation of developers for test Nos. 2, 5, 8, 11, 14, 16 and 18 > The developers for test Nos. 2, 5, 8, 11 and 14 each relating to the invent ion and the developer for comparative test Nos. 16 and 18 were obtained in the same manner as in the case of the developer for test No. 1, except that, in each of the developers, the triiron tetraoxide was used in an amount of 240 g, i.e., in an proportion of 50 wt in tne toner used.

< Preparation of developers for test Nos. 3, 6, 9, 12, 15, 17 and 19 > The developers for test Nos. 3, 6, 9, 12 and 15 each relating to the invention and the developer for comparative test Nos. 17 and 19 were obtained in the same manner as in the case of the developer for test No. 1, excep that, in each of the developers, the triiron tetraoxide was used in an amount of 560 g, i.e., in an proportion of 70 wt% in the toner used.

The 7 kinds of the photoreceptors and the 3 kinds of the developers, which had been prepared as described above, were loaded on a digital printer of the contact reversal development system which was modified from a digital printer of the normal contact development system, Model LIPS-10 manufactured by Konica Corporation, and 19 kinds of tests i.e., the inventive test Nos. 1 to 15 and the comparative test Nos. 16 to 19 were tried in the order and contents indicated in Table 1.

Besides the above, the other 7 kinds of photoreceptors, i.e., the photoreceptors of synthesis examples 1 to 5 and the photoreceptor of the comparative synthesis examples 1 and 2, were each obtained in the same manner as in the photoreceptors for test Nos. 1 to 19, except that the diameter of the aluminium drum was changed into 150 mm.Thus prepared 7 kinds of the photoreceptors and the foregoing 3 kinds of the developers were each loaded on a digital multicoor couvina machine of the non-contact reversal development system, Model DC-8010 manufactured by Konica Corporation, and 19 kinds of the tests, the inventive test Nos. 21 to 35 and the comparative test Nos. 36 to 39, were each tried in the order and contents as indicated in Table 2, by making use of only the black image reading mechanism and a black development device modified for single component type developer use.

In the tests tried with the LIPS-10 printer indicated in Table 1 and in the tests tried with the DC-8010 copying machine indicated in Table 2, the images were tried to form 1000 times in succession at an ordinary temperature and an ordinary humidity -at 20'C and 60%RH- and a high temperature and a high humidity -at 33 C and 80RH-, and the Dmax of the image obtained in the initial stage and the 1000th image, fogginess and resolving power were evaluated in the following manners, respectively. The results thereof are shown in Table 1.

Image evaluatIon method: < Dmax > An original document having a reflection density of 1.5 was imaged, and the reflection density of the image density obtained was measured by making use of a 'Sakura densitometer' manufactured by Konica Corporation.

< Fogginess > The resulting fog density was measured by the abovementioned 'Sakura densitometer' and, the results of the evaluation graded 'P1 when a fog density exceeds 0.1, 'N' when it was within the range of G.1 to 0.C5, and 'E' when it was less than 0.05, respectively.

< Resolving power > By making use of a chart prepared, in conformity with JIS Z4916, by arranging a series of lines at regular intervals, i.e., 4.0 lines, 5.0 lines, 6.3 lines, 8.0 lines, 10.0 lines, 12.5 lines and 16.0 lines each per mm as the grades, a copied image was judged visually, so that the grades capable of discriminating the lines were expressed as a resolving power. Table 1-a Material Processor (Modified LIPS-10 for contact#reversal development) Synthesis Ordinary temp/humidity (20 C, 60%RH) example No.Magnetite of pigment content of Initial image 1000th image for photo- developer resolving resolving Test No. receptor (wt %) Dmax Fog power Dmax Fog power 1 Inv. 1 30 1.38 E 6.3 1.38 E 6.3 2 Inv. 1 50 1.40 E 6.3 1.39 E 6.3 3 Inv. 1 70 1.39 E 6.3 1.38 E 6.3 4 Inv. 2 30 1.38 E 6.3 1.37 E 6.3 5 Inv. 2 50 1.37 E 6.3 1.37 E 6.3 6 Inv. 2 70 1.40 E 6.3 1.38 E 6.3 7 Inv. 3 30 1.38 E 6.3 1.38 E 6.3 8 Inv. 3 50 1.37 E 6.3 1.36 E 6.3 9 Inv. 3 70 1.38 E 6.3 1.38 E 6.3 10 Inv. 4 30 1.39 E 6.3 1.38 E 6.3 11 Inv. 4 50 1.38 E 6.3 1.38 E 6.3 12 Inv. 4 70 1.40 E 6.3 1.39 E 6.3 13 Inv. 5 30 1.40 E 6.3 1.38 E 6.3 14 Inv. 5 50 1.37 E 6.3 1.37 E 6.3 15 Inv. 5 70 1.39 E 6.3 1.38 E 6.3 16 Comp 1 50 1.37 E 6.3 1.32 E 5.0 17 Comp. 1 70 1.38 E 6.3 1.31 E 5.0 18 Comp. 2 50 1.38 E 6.3 1.34 N 5.0 19 Comp. 2 70 1.39 E 6.3 1.35 N 5.0 < Continued > Table 1-b < Continued from Table 1-a > Processor (Modified LIPS-10 for contact#reversal development) High temp/high humidity (33 C, 80%RH) Initial image 1000th image resolving resolving Test No. Dmax Fog power Dmax Fog power 1 1.32 E 6.3 1.30 E 6.3 2 1.34 E 6.3 1.31 E 6.3 3 1.34 E 6.3 1.31 E 6.3 4 1.31 E 6.3 1.31 E 6.3 5 1.33 E 6.3 1.32 E 6.3 6 1.34 E 6.3 1.32 E 6.3 7 1.32 E 6.3 1.30 E 6.3 8 1.33 E 6.3 1.30 E 6.3 9 1.31 E 6.3 1.31 E 6.3 10 1.30 E 6.3 1.28 E 6.3 11 1.31 E 6.3 1.29 E 6.3 12 1.32 E 6.3 1.30 E 6.3 13 1.29 E 6.3 1.27 E 6.3 14 1.30 E 6.3 1.28 E 6.3 15 1.28 E 6.3 1.25 E 6.3 16 1.09 N 4.0 0.82 N < 4.0 17 0.91 P < 4.0 0.72 P < 4.0 18 1.12 N 5.0 0.98 N 4.0 19 1.03 N 4.0 0.89 N < 4.0 Table 2-a Material Processor (Test machine DC-8010 for non-contact#reversal developement) Synthesis example No. Magnetite Ordinary temp/humidity (20 C, 60%RH) of pigment content of Initial image 1000th image for photo- developer resolving resolving Test No. receptor (wt %) Dmax Fog power Dmax Fog power 21 Inv. 1 30 1.38 E 6.3 1.37 E 6.3 22 Inv. 1 50 1.41 E 6.3 1.36 E 6.3 23 Inv. 1 70 1.40 E 6.3 1.37 E 6.3 24 Inv. 2 30 1.39 E 6.3 1.36 E 6.3 25 Inv. 2 50 1.38 E 6.3 1.37 E 6.3 26 Inv. 2 70 1.40 E 6.3 1.36 E 6.3 27 Inv. 3 30 1.40 E 6.3 1.38 E 6.3 28 Inv. 3 50 1.39 E 6.3 1.37 E 6.3 29 Inv. 3 70 1.39 E 6.3 1.37 E 6.3 30 Inv. 4 30 1.37 E 6.3 1.36 E 6.3 31 Inv. 4 50 1.38 E 6.3 1.37 E 6.3 32 Inv. 4 70 1.38 E 6.3 1.36 E 6.3 33 Inv. 5 30 1.37 E 6.3 1.35 E 6.3 34 Inv. 5 50 1.36 E 6.3 1.34 E 6.3 35 Inv. 5 70 1.35 E 6.3 1.34 E 6.3 36 Comp. 1 50 1.39 E 6.3 1.36 E 5.0 37 Comp. 1 70 1.38 E 6.3 1.34 E 5.0 38 Comp. 2 50 1.37 E 6.3 1.35 E 5.0 39 Comp. 2 70 1.37 E 6.3 1.34 E 5.0 < Continued > Table 2-b < Continued from Table 2-a > Processor (Test machine DC-8010 for non-contact reversal development) Hight temp/high humidity (33 C, 80%RH) Initial image 1000th image resolving resolving Test No. Dmax Fog power Dmax Fog power 21 1.33 E 6.3 1.30 E 5.0 22 1.33 E 6.3 1.30 E 5.0 23 1.32 E 6.3 1.31 E 5.0 24 1.32 E 6.3 1.30 E 5.0 25 1.34 E 6.3 1.32 E 5.0 26 1.32 E 6.3 1.30 E 5.0 27 1.31 E 6.3 1.30 E 5.0 28 1.31 E 6.3 1.29 E 5.0 29 1.32 E 6.3 1.30 E 5.0 30 1.32 E 6.3 1.28 E 5.0 31 1.33 E 6.3 1.27 E 5.0 32 1.31 E 6.3 1.29 E 5.0 33 1.33 E 6.3 1.30 E 5.0 34 1.31 E 6.3 1.28 E 5.0 35 1.33 E 6.3 1.29 E 5.0 36 1.10 N 4.0 0.92 P < 4.0 37 1.12 N 4.0 0.91 P < 4.0 38 1.17 N 5.0 0.95 N 4.0 39 1.13 N 5.0 0.94 N 4.0 It can be proved from Tables 1 and 2 that every test image obtained in accordance with the image forming process of the invention could provide no fogginess, a high density and a high resolving power and, on the other hand, that the images obtained in the comparative tests provided an increased fogginess and the seriously lowered Dmax and resolving power in the conditions of a high temperature and a high humidity.

Claims (8)

1. A method for forming an electrophotographic image which comprises: uniformly charging an electrophotographic photoreceptor comprising a conductive substratum having thereon a photoreceptive layer containing a phthalocyanine pigment; imagewise exposing the photoreceptor to light to form an electrostatic latent image; and developing the electrostatic image with a single component type magnetic toner; wherein the phthalocyanine pigment contains adsorbed water molecules in a numerical amount greater than any other adsorbed gas molecules, as determined by adsorption gas analysis carried out in vacuum.

2. A method according to claim 1, wherein the phthalocyanine pigment has an endothermic peak within the range of from 80"C to 120"C in a thermal differential analysis.

3. A method according to claim 1 or 2, wherein the phthalocyanine pigment is a titanyl phthalocyanine pigment of formula:

wherein X1, X2, X3 and X4 are each independently a hydrogen atom, a halogen atom, an alkyl group or an alkoxy group; and m, n, 0 and k are each independently an integer of from 0 to 4.

4. A method according to claim 3, wherein the titanyl phthalocyanine pigment has peaks at the Bragg angle 20 of 9.5 + 0.2 and 27.2 1 0.2 in an X-ray diffraction spectrum thereof with a Cu-Ka ray.

5. A method according to any one of the preceding claims, wherein the photoreceptive layer comprises a carrier generating layer containing the phthalocyanine pigment and a carrier transporting layer containing a carrier transporting material.

6. A method according to any one of the preceding claims, wherein the single component type toner is a dielectric toner.

7. A method according to claim 6, wherein the dielectric toner has a volumetric resistance of not less than 1012 flom.

8. A method according to claim 1 substantially as herein described in the Examples.