JPH0253782B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is a method for developing an electrostatic latent image formed in electrophotography, electrostatic recording, electrostatic printing, etc. using an organic photoconductive photoreceptor using a two-component developer. The present invention relates to an image forming method including steps. [Prior Art] Currently, in order to form a visible image from certain image information, methods using electrostatic latent images, such as electrophotography, are widely used. For example, according to an example of electrophotography, an electrostatic latent image formed on a latent image carrier made of a photoconductive photoreceptor by a charging process and an exposure process is used as a developer made of electrodetectable colored particles called a toner. The toner image is usually transferred and fixed onto a transfer material to obtain a visible image. The developer used to develop such an electrostatic latent image is a so-called two-component developer consisting of a mixture of toner and carrier, and a magnetic toner containing a magnetic substance, which is used alone without being mixed with carrier. However, in the system using a two-component developer, the toner is frictionally charged by mechanically stirring the toner and carrier, so the characteristics of the carrier, stirring conditions, etc. By selecting the developer, it is possible to control the charge polarity and charge amount of the toner to a considerable extent, and in this respect, the developer is superior to a one-component developer. Further, as a developing method, there are a magnetic brush method, a cascade method, and the like, and among these, the magnetic brush method is preferably used. This magnetic brush method involves forming spikes of developer, that is, magnetic brushes, which stand up in the form of a brush by magnetic force on a developer transporting carrier, and then sliding this magnetic brush against the surface of a latent image carrier to prevent electrostatic This is a method of developing an image by attaching toner particles to the image. In a developing method using such a magnetic brush method, the electric field strength in the developing region is one of the important conditions that determines the developability. and,
Factors that define the electric field strength include the surface potential when the photoconductive photoreceptor constituting the latent image carrier is charged, the distance between the latent image carrier and the developer transport carrier in the development area, and the developer ( In a two-component developer, there is an electrical resistance, especially of the carrier, and the electric field strength is determined by the correlation of these factors. On the other hand, recently, there has been a demand for the use of organic photoconductive photoreceptors, which are advantageous in that they not only have high high-temperature durability and stable photosensitive properties over a long period of time, but also are highly safe and inexpensive. It is being However, since this organic photoconductive photoreceptor generally has low photosensitivity, the potential difference between the non-image area that is irradiated with light and the image area that is not irradiated with light during the exposure process is small. Imaging methods using conductive photoreceptors have the disadvantage that the resulting visible images have low density. In addition, organic photoconductive photoreceptors have delicate characteristics, so subtle fluctuations in developing conditions can have a large effect on visible images, making it difficult to consistently obtain excellent visible images. has. [Object of the Invention] The present invention has been made against the background as described above, and its object is to provide an image forming method using an organic photoconductive photoreceptor without image unevenness. An object of the present invention is to provide an image forming method that can stably form high quality images with high image density over many times. [Structure of the Invention] The above object is to form an electrostatic latent image on a latent image carrier made of an organic photoconductive photoreceptor, and to carry a developer made of toner and carrier in a developing area. In an image forming process including a step of developing the electrostatic latent image by a developer transporting carrier facing the carrier, the highest potential ( ) of the charges forming the electrostatic latent image
The absolute value of is 400 to 700, the minimum value of the gap between the latent image carrier and the developer transport carrier constituting the development area is within the range of 0.30 to 0.65 mm, and the carrier is a core material, The following general formula () or () is provided on the surface of this core material.
This is achieved by an image forming method characterized by comprising a polymer of a monomer composition containing the monomer shown as the main component or a coating layer of a composition containing the polymer. . General formula () General formula () (In the formula, R ¹ and R ² each represent a hydrogen atom or a methyl group, n and p each represent an integer of 1 to 8, and m and q each represent an integer of 1 to 19.) The above general formula ( ) and general formula () are preferably monomers represented by the following general formula () and general formula () from the viewpoint of triboelectric charging properties. General formula () General formula () (In the formula, R ³ and R ⁴ each represent a hydrogen atom or a methyl group, 1 represents 1 or 2, and r represents 2
Represents an integer from ~4. ) Preferred monomers represented by the general formula () or () include, for example, methacrylic acid 1,1-
Examples include dihydroperfluoroethyl or 1,1,3-trihydroperfluoro n-propyl methacrylate. Hereinafter, the present invention will be explained in detail based on an example of application to electrophotography. In the present invention, a latent image carrier made of an organic photoconductive photoconductor (hereinafter also referred to as "OPC photoconductor") and a developer transport carrier are disposed opposite to each other with a development area interposed therebetween, and the latent image carrier is While moving the carrier, the electrostatic latent image formed on the carrier was moved to the development area, and was formed on the developer transport carrier by magnetic force. A magnetic brush with a two-component source developer consisting of toner and carrier is carried into the development area, and in the development area, the electrostatic latent image on the latent image carrier is rubbed by this magnetic brush, and the toner particles in the magnetic brush are removed. Development is achieved by electrostatically adhering to the electrostatic latent image, and the following conditions (a) to (c) must be satisfied in the above steps. (a) The OPC photoreceptor constituting the latent image carrier must have an absolute value (usually negative) of the highest potential of the electrostatic latent image when it is charged (usually negative) within the range of 400 to 700V. (b) The minimum gap (Dsd) between the latent image carrier and the developer transport carrier in the development area is 0.30 to 0.65 mm.
be within the range of (c) The carrier includes a core material and a monomer provided on the surface of the core material, the main component of which is a monomer represented by the general formula () or () (preferably containing 50% by weight or more). It has a fluorine-containing polymer obtained from the composition or a multilayer formed from a composition containing the polymer. By satisfying these conditions (a), (b), and (c), the electric field state in the development area can be made appropriate, making it possible to achieve good development, and as a result, the image It is possible to form a high-quality image with high density and suppressed occurrence of image unevenness or fog. If the absolute value of the highest potential () of the electrostatic latent image on the OPC photoreceptor constituting the latent image carrier is outside the range of condition (a) and the value is less than 400, the required electric field It becomes difficult to obtain strength, and on the other hand, if it exceeds 700, it is necessary to increase the film thickness of the OPC photoreceptor, which lowers the sensitivity and is not preferred in practice. If the minimum gap (Dsd) between the latent image carrier and the developer transport carrier is outside the range of condition (b) and is less than 0.30 mm, it will be difficult to obtain a uniform developing effect in the developing area. This tends to cause image unevenness. On the other hand, if the minimum gap (Dsd) exceeds 0.65mm,
In the development area, the effect of opposing electrodes between the toner particles and the latent image is reduced, which tends to lower the image density, and the edge effect, in which more toner adheres to the contours than the center of the latent image, tends to occur. When the carrier satisfies condition (c), the carrier becomes an insulating material with an electrical resistivity value of 10 ¹³ Ωcm or more. The charge of the electrostatic latent image formed on the latent image carrier or the charge of the toner does not leak through the magnetic brush formed by the magnetic brush, and therefore the distribution state of the charge of the electrostatic latent image does not change. This prevents the charging state of the toner from becoming inappropriate, and it is possible to achieve good development. The above electric resistivity value is calculated by placing a sample into a measurement cell with a cross-sectional area of 1 cm ² (Fcm ² ) at a depth of 0.03 to 0.08 cm (hcm), applying a load of 1 kg from the top surface, and applying an applied voltage (V Current value (i ampere) when changing the voltage (volts)
is measured and calculated using the following formula. Electrical resistivity value ρ (Ω・cm)=V×F/i×h Furthermore, the carrier having a coating layer made of the above-mentioned fluorine-containing polymer or a composition containing the polymer has a negative fluorine-containing polymer. Since it has a strong tendency to charge, it has a good positive charging function for toner. Therefore, it is possible to make the developability of an OPC photoreceptor, which is normally given a negative surface potential, sufficiently high, and improve image density. It is possible to prevent the occurrence of fog. Moreover, the fluorine-containing polymer has excellent water resistance and can increase the durability of the carrier. Next, the present invention will be explained in more detail. For example, a developing sleeve is preferably used as the developer transporting carrier for supplying the two-component developer to the developing area. There are two types of developing sleeves: one consisting of a plurality of sleeves and one consisting of one sleeve, but it is more preferable to form an image with a developing sleeve consisting of one sleeve. The developer transport carrier can have a structure to which a bias voltage can be applied, and has, for example, a cylindrical sleeve on which a magnetic brush is supported, and a plurality of magnetic poles arranged inside the sleeve. The rotation of the sleeve carries the magnetic brush on the sleeve into the developing area. The magnetic brush supported on the developer transport carrier is
In order to perform uniform development without unevenness, it is preferable that the developer be carried into the development area with a uniform height. Therefore, on the upstream side of the development area on the developer transport carrier, the height of the magnetic brush should be adjusted. It is preferable to provide a regulating blade for regulating the height of the magnetic brush so that the height of the magnetic brush is trimmed to a constant level. The regulating blade may be made of a magnetic material or a non-magnetic material. The distance (Hcut) between the tip of the regulating blade and the surface of the developer transport carrier is set in relation to the minimum gap (Dsd) between the latent image carrier and the developer transport carrier in the development area. However, the distance (H cut ) is approximately the minimum gap (Dsd)
It is preferable to set it to about 0.8 times. A bias voltage can be applied to the development area as necessary. This bias voltage is generally only a DC voltage, but it may also be a voltage in which an AC voltage is superimposed on a DC voltage. In this case, the DC voltage prevents toner particles from adhering to the background area other than the latent image area. Not only this effect is obtained, but also the toner particles are easily dispersed from the carrier particles by the alternating current voltage, resulting in good toner adhesion to the latent image. The magnitude of DC voltage is preferably about 0 to 300V in absolute value, and the effective value of AC voltage is, for example, 100V to 5KV.
It is preferable that the frequency is, for example, about 100Hz to 10KHz. The toner image formed by the above development process is transferred to a transfer material such as paper by, for example, an electrostatic transfer method, and then the transferred image is fixed in a fixing device by, for example, a contact heating fixing method using a heating roller. A visible image is formed. The latent image carrier used in the present invention is an organic photoconductive photoreceptor (OPC photoreceptor). this
An OPC photoreceptor is constructed by forming a photosensitive layer on a conductive support, comprising a photoconductive substance made of an organic compound alone or dispersed in a binder resin as required. Such a photosensitive layer includes a carrier generation layer containing a carrier generation substance that absorbs visible light and generates charged carriers, and a carrier that transports either or both of positive and negative carriers generated in this carrier generation layer. It is preferable to have a two-layer structure in which a carrier transport layer containing a transport substance is combined. in this way,
By assigning the two basic functions necessary for the photosensitive layer, carrier generation and transport, to separate layers, the range of materials that can be used in the composition of the photosensitive layer is widened, and each function can be optimized. By doing so, it becomes possible to independently select materials or material systems that achieve the desired properties in the electrophotographic process, such as high surface potential when charged, large charge retention ability, and light resistance. It becomes possible to construct a photoreceptor having excellent characteristics such as high sensitivity and great stability in repeated use. Examples of such carrier generating substances include anthonthrone pigments, perylene derivatives, phthalocyanine pigments, azo dyes, and indigoid dyes, and examples of carrier transport substances include carbazole derivatives and oxadiazole derivatives. , triarylamine derivatives, polyarylalkane derivatives, hydrazone derivatives,
Examples include pyrazoline derivatives, stilbene derivatives, and styryltriarylamine derivatives. Examples of binder resins constituting the photosensitive layer in OPC photoreceptors include polyethylene, polypropylene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, epoxy resin, polyurethane resin, phenolic resin, polyester resin, alkyd resin, and polycarbonate resin. ,
Addition polymer resins such as silicone resins and melamine resins, polyaddition resins, polycondensation resins, and copolymer resins containing two or more repeating units of these resins, such as vinyl chloride-vinyl acetate copolymers Examples include insulating resins such as composite resins, vinyl chloride-vinyl acetate-maleic anhydride copolymer resins, and styrene-acrylic copolymer resins, as well as polymeric organic semiconductors such as poly-N-vinylcarbazole. In addition, examples of materials constituting the conductive support in the OPC photoreceptor include aluminum, nickel, copper, zinc, palladium, silver, indium,
A sheet of metal such as tin, platinum, gold, stainless steel, steel, brass, etc. can be used. Such OPC photoreceptors have various mechanical configurations, but the present invention is not particularly limited and any configuration may be used. 1 to 6 each show an example of the mechanical structure of an OPC photoreceptor, and FIGS. 1 and 3 each show a carrier generation layer 12 containing a carrier generation substance as a main component on a conductive support 11. This is an example in which a photosensitive layer 14 made of a laminate with a carrier transport layer 13 containing a carrier transport substance as a main component is provided.
2 and 4 are examples in which an intermediate layer 15 is provided between the photosensitive layer 14 and the conductive support 11, respectively. 5 and 6 respectively show an example in which a photosensitive layer 14 in which a carrier generating substance 17 is dispersed in a layer 16 mainly composed of a carrier transporting substance is provided directly on a conductive support 11, and an intermediate layer. This is an example in which it is provided through 15. The toner constituting the two-component developer used in the present invention is made by dispersing toner components such as a colorant in a binder resin, and various thermoplastic resins are used as the binder resin. Specific examples include styrenes such as styrene, parachlorostyrene, and α-methylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, and methyl methacrylate. , ethyl methacrylate, methacrylic acid n
-α-methylene aliphatic monocarboxylic acid esters such as butyl, lauryl methacrylate, and 2-ethylhexyl methacrylate; vinyl nitriles such as acrylonitrile and methacrylonitrile; 2
- Vinylpyridines such as vinylpyridine and 4-vinylpyridine; Vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; Vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, and methyl isopropenyl ketone; Ethylene, propylene, isoprene, butadiene Polymers of monomers such as unsaturated hydrocarbons and their halides, halogenated unsaturated hydrocarbons such as chloroprene, or copolymers obtained by combining two or more of these monomers; or non-vinyl condensation resins such as rosin-modified phenol-formalin resins, epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, or mixtures of these and the vinyl resins. Can be done. Colorants include, for example, carbon black, nigrosine dye, aniline blue, calco oil blue, chrome yellow, ultramarine blue, methylene blue, rose bengal, phthalocyanine blue, or mixtures thereof. Toner components other than the colorant include a charge control agent, an anti-offset agent, a fluidity improver and the like, and if necessary, fine magnetic powder may be contained. Such a toner can be obtained by a conventionally known toner manufacturing method, and has an average particle size of 20 μm or less,
Particularly preferred is a toner having a diameter of 8 to 12 μm. The carrier constituting the two-component developer used in the present invention includes a core material and a monomer provided on the surface of the core material that preferably contains 50% by weight or more of a monomer represented by the general formula () or (). It is a particulate powder comprising a polymer of a polymeric composition (hereinafter also referred to as "specific polymer") or a coating layer of a composition containing the polymer and other substances added as necessary. . Examples of the polymer of the monomer represented by the general formula () or () include, but are not limited to, those whose repeating units are represented by the following structural formula. The specific polymer is obtained by polymerizing a monomer composition preferably containing 50% by weight or more of the monomer represented by the general formula () or (), but other monomers that can be used may also be used. For example, styrenes such as styrene, parachlorostyrene, and α-methylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, and ethyl methacrylate. , α-methylene aliphatic monocarboxylic acid esters such as n-butyl methacrylate, lauryl methacrylate, and 2-ethylhexyl methacrylate. The core material constituting the carrier must be made of a material that can form a magnetic brush, that is, a magnetic material. Examples of such magnetic materials include iron such as ferrite and magnetite;
Metals or alloys that exhibit ferromagnetism such as cobalt and nickel, or compounds containing these elements, or alloys that do not contain ferromagnetic elements but become ferromagnetic through appropriate heat treatment, such as manganese-copper. - Aluminum, manganese - Copper -
Mention may be made of a type of alloy called Heusler alloy containing manganese and copper such as tin, or chromium dioxide, among others. The particle size of this core material is, for example, 30 to 200 μm, preferably 40 to 120 μm, and the shape is preferably spherical to improve fluidity. The carrier as described above used in the present invention can be manufactured, for example, in the following manner. That is, a coating liquid is prepared by dissolving a polymer having the above characteristics or a composition containing the polymer in a solvent such as acetone, a ketone such as methyl ethyl ketone, tetrahydrofuran, dioxane, or dimethyl sulfoxide, and this coating liquid is applied to the core material. It is applied to the surface and dried to form a coating layer on the surface of the core material. In this application, a dipping method, a spray method, etc. can be used, but a fluidized bed method is particularly preferred. This fluidized bed method uses a pressurized gas flow that rises in the fluidized bed device to lift and float the core material to an equilibrium height, and then the coating liquid is applied from above until the core material falls again. There is a method of spraying and coating each core material and repeating this process to form a coating film of a desired thickness. By this method, a uniform coating film can be formed on each core material. The thickness of the coating layer is 0.2 to 5 μm, especially 0.5 to 2 μm.
The particle size of the carrier is, for example, 30 to 200 μm, preferably 40 to 120 μm, particularly preferably 50 to 75 μm. If the particle size of the carrier is less than 30 μm, the carrier has low fluidity and has a small ability to convey toner to the developing area.As a result, image density tends to decrease, and coating processing is difficult during carrier manufacture. Therefore, it is difficult to obtain such a small diameter carrier with a uniform coating layer. On the other hand, if the particle size of the carrier exceeds 200 μm, the surface area of the carrier particles as a whole per unit weight is small, so the ability to convey toner to the developing area is small, and the image density tends to decrease. Further, the carrier used in the present invention may contain additives such as a charge control agent and a fluidity improver, if necessary. Next, one embodiment of the present invention will be described based on a specific example of an apparatus that can be used to perform the developing process in the present invention. Fig. 7 shows an example of the device, and in Fig. 7, 1 is an OPC
It is a rotating drum-shaped latent image carrier made of a photoreceptor, and is constructed by laminating a photosensitive layer 1b made of an organic photoconductive substance on a cylindrical conductive support 1a made of, for example, aluminum. The latent image carrier 1 is rotated in the direction of the arrow X, and a charger (not shown) is placed on the upstream side of the development area Q so that the surface to be developed has a certain potential within a range of, for example, -400 to -700V. After being charged, an electrostatic latent image corresponding to the original is formed on the developed image by an exposure device (not shown), and then the electrostatic latent image is moved to the development area Q and developed there. 2 is disposed opposite to the latent image carrier 1 so that the minimum gap (Dsd) between the latent image carrier 1 and the developing area Q is within the range of 0.30 to 0.65 mm.
A sleeve made of non-magnetic material such as aluminum,
3 is a plurality of N and S provided inside the sleeve 2.
The sleeve 2 and the magnet 3 constitute a developer transport carrier, which is a magnet having magnetic poles along its circumference.
The sleeve 2 and the magnet body 3 are relatively rotatable, and in the illustrated example, the sleeve 2 is rotated so as to move in the direction of arrow Y, that is, in the same direction as the moving direction of the latent image carrier 1 in the development area Q. The magnet body 3 is fixed. The N and S magnetic poles of the magnet body 3 are normally magnetized to a magnetic flux density of 500 to 1500 Gauss, and the magnetic force causes a layer of developer D consisting of brush-like spikes on the surface of the sleeve 2, that is, a magnetic brush. form. 4
5 is a regulating blade made of magnetic or non-magnetic material that regulates the height and amount of the magnetic brush; 5 is a cleaning blade that removes the magnetic brush that has passed through the developing area Q from above the sleeve 2; The surface of the sleeve 2 after cleaning comes into contact with the developer D again in the developer reservoir 6, and a new magnetic brush is formed on the surface, thereby supplying the developer D. A stirring screw 7 stirs the developer D in the developer reservoir 6 to make the components uniform. In the developer D in the developer reservoir 6, the carrier is used repeatedly, whereas the toner is consumed every time development is performed, so new toner particles T are replenished by the toner hopper 8 as appropriate. Reference numeral 9 denotes a supply roller having a concave portion on its surface, which drops the toner particles T into the developer reservoir 6. 10 is a bias power supply that applies a bias voltage to the sleeve 2 via a protective resistor R. In developing an electrostatic latent image, it is preferable that the tip of the magnetic brush make shallow contact with the surface of the latent image carrier 1 in order to achieve uniform development. The distance between them (Hcut) is preferably about 0.8 times the minimum gap (Dsd) between the latent image carrier 1 and the sleeve 2 in the development area Q. In the device described above, the magnitude and direction of the magnetic field on the surface of the sleeve 2 change as the sleeve 2 rotates, so the carrier particles on the surface of the sleeve 2 follow the rotational movement of the sleeve 2 while rotating and vibrating. It is transported to the development area Q. [Effects of the Invention] As explained in detail above, according to the present invention,
An image forming method including a developing step of using a latent image carrier made of an OPC photoconductor and performing development by rubbing a magnetic brush formed on a developer transporting carrier with a two-component developer. By specifying the developer carrier and the minimum gap (Dsd) between the latent image carrier and the developer transport carrier,
These interrelationships allow the electric field state in the development area to be appropriate, and therefore, good development can be achieved in the development process using an OPC photoconductor, which has low photosensitivity and is generally difficult to obtain high image density. can be achieved. the result,
While taking full advantage of the benefits of using an OPC photoconductor, such as high high-temperature durability and stable photosensitive characteristics over a long period of time, it is possible to stably produce clear images with high image density and no image unevenness. You can get it. [Examples of the Invention] Specific examples of the present invention will be described below, but the present invention is not limited to these examples. (Carrier) A polymer whose repeating unit is represented by the structural formula below.
Add 15 g of each of (1) to (6) to acetone-methyl ethyl ketone (weight ratio 1:1) mixed solvent (or 1,
1,2-trifluoro-1,2,2-trichloroethane) to prepare six coating solutions.
Using each of these coating solutions, 1 kg of core material made of spherical iron powder "DSP-135C" (manufactured by Dowa Iron Powder Kogyo Co., Ltd.) was coated using a fluidization bed device, and a carrier with a coating layer thickness of approximately 2 μm was coated. I got it. These will be referred to as "carrier A" to "carrier F", respectively. On the other hand, a comparative carrier was produced in the same manner as above using methyl methacrylate-styrene copolymer (copolymerization ratio 70:30) and methyl ethyl ketone as the solvent. This will be referred to as "comparative carrier A." Furthermore, as a “comparison carrier B”, a negatively chargeable spherical coating carrier “C-1018” was selected.
(manufactured by Nuclear Metals) was used. The above carriers A to F and comparative carrier A,
The average particle size of B is 105 μm in all cases. (Toner) Toner A: 332 g of terephthalic acid, 90 g of polyoxypropylene (2,2)-2,2-bis(4-hydroxyphenyl)propane, and 587 g of bisphenol A, a thermometer, and a stainless steel stirrer. The flask was placed in a round-bottomed flask equipped with a glass nitrogen gas inlet tube and a flow-down condenser, and the flask was set on a mantle heater, and nitrogen gas was introduced through the nitrogen gas inlet tube to maintain an inert atmosphere inside the flask. The temperature was raised under this condition. Then, 0.05 g of dibutyltin oxide was added, and the reaction was carried out at a temperature of 200° C. while monitoring the reaction at the softening point to obtain a polyester resin. 100 parts by weight of this polyester resin, 10 parts by weight of carbon black "Regal 660R" (manufactured by Cabot Co., Ltd.), low molecular weight polypropylene "Piskol"
660P'' (manufactured by Sanyo Chemical Industries, Ltd.) and 2 parts by weight of etilebis stearoylamide ``Hoechstwax C'' (manufactured by Hoechst) were mixed in a ball mill, and after each process of kneading, pulverization, and classification, an average particle size was obtained. A toner having a diameter of 10 μm was obtained. This will be referred to as "toner A." Toner B: 100 parts by weight of styrene-methyl methacrylate-n-butyl methacrylate copolymer obtained by reacting styrene, methyl methacrylate, and n-butyl methacrylate at a molar ratio of 50:20:30, carbon black " 10 parts by weight of "Regal 660R" (manufactured by Kyabot Co., Ltd.), low molecular weight polypropylene "Viscol"
660P'' (manufactured by Sanyo Chemical Industries, Ltd.) was mixed in a ball mill and subjected to the steps of kneading, pulverization, and classification to obtain a toner with an average particle size of 11 μm. This is called "toner B". Toner C: 100 parts by weight of a styrene-methyl methacrylate-n-butyl methacrylate copolymer obtained by reacting styrene, methyl methacrylate, and n-butyl methacrylate at a molar ratio of 50:20:30, carbon black 10 parts by weight of "Regal 660R" (manufactured by Kyabot Co., Ltd.), low molecular weight polypropylene "Viscol"
660P" (manufactured by Sanyo Chemical Industries, Ltd.) and 2 parts by weight of nigrosine dye "Oil Black SO" (manufactured by Orient Chemical Co., Ltd.) were mixed in a ball mill, and through the steps of kneading, crushing, and classification, the average particle size was determined. 11μ
m toner was obtained. This will be referred to as "toner C". (Developer) A two-component developer with a toner concentration of 2% by weight was prepared by mixing the toners A, B, and C with the carriers A to F and the comparative carriers A and B in the combinations shown in Table 1 below. A total of 14 types were prepared. (Photoreceptor) OPC is produced by laminating a negatively charged two-layer photosensitive layer on a drum-shaped aluminum conductive support using an anthrone pigment as a carrier generating substance and a carbazole derivative as a carrier transporting substance. A photoreceptor was produced. This will be referred to as "OPC photoreceptor A." Examples 1 to 9 and Comparative Examples 1 to 5 Electrophotographic copying machine "U-Bix3000" (manufactured by Konishiroku Photo Industry Co., Ltd.) using the OPC photoreceptor A as a latent image carrier
In each of the Examples and Comparative Examples, it was installed in a modified machine, and a live photo test was conducted under the conditions shown in Table 1 below to investigate the maximum image density (Dmax) and the occurrence of fog at the initial stage and after 10,000 copies. . The results are also shown in Table 1. Under other conditions, the distance (Hcut) between the tip of the regulating blade and the sleeve is approximately Dsd x 0.8 mm, the magnet is fixed, and the magnetic flux density on the sleeve surface is
800 Gauss, and the bias voltage applied to the sleeve is -100V DC. In addition, the maximum image density (Dmax) is evaluated based on the relative density when the image density of the original image is set to 1.3, and regarding the occurrence of fog, the black area ratio of the area corresponding to the white area of the original image in the copied image is evaluated. The evaluation was based on values measured with a point analysis device "Sakura Area Duck-100" (manufactured by Konishiroku Photo Industry Co., Ltd.).

【table】

[Table] As is clear from the results in Table 1, according to Examples 1 to 9 of the present invention, images with sufficiently high image density without image unevenness and fog could be obtained. Further, even after 10,000 continuous duplications, clear images without fogging could be obtained. On the other hand, in Comparative Example 1, the minimum gap value Dsd is too small, resulting in image unevenness, and in Comparative Examples 2 and 3, the minimum gap value Dsd is too large, resulting in insufficient image density. In Comparative Examples 4 and 5, it was possible to obtain images with high image density without fogging at the initial stage of copying, but after continuous copying for 10,000 times,
The characteristics of both fog and image density deteriorated significantly, making it impossible to obtain a high-quality image.

[Brief explanation of the drawing]

1 to 6 are cross-sectional views each showing an example of the mechanical structure of an organic photoconductive photoreceptor, and FIG. 7 is an example of a developing device that can be used to carry out a developing process in the practice of the present invention. It is an explanatory sectional view showing an outline. 11... Conductive support, 12... Carrier generation layer, 13... Carrier transport layer, 14... Photosensitive layer,
15...Intermediate layer, 17...Carrier generating substance, 1
...Latent image carrier, 2 ... Sleeve, 3 ... Magnet, 4 ... Regulation blade, 5 ... Cleaning blade, 6 ... Developer reservoir, 7 ... Stirring screw, 8 ... Toner hopper, 9 ... ...supply roller,
10...Bias power supply, R...Protection resistor, Q...
Development area, D...developer, T...toner particles,
N, S...Magnetic pole.

Claims (1)

[Scope of Claims] 1. A latent image carrier comprising an organic photoconductive photoreceptor, on which an electrostatic latent image is formed, and a developer consisting of toner and carrier is supported in the development area. In an image forming process including a step of developing the electrostatic latent image by opposing developer transport carriers, the highest potential (V) of the charges forming the electrostatic latent image
The absolute value of is 400 to 700, the minimum value of the gap between the latent image carrier and the developer transport carrier constituting the development area is within the range of 0.30 to 0.65 mm, and the carrier is a core material and The following general formula () or () is provided on the surface of this core material.
An image forming method comprising: a polymer of a monomer composition containing the monomer represented by the formula as a main component, or a coating layer made of a composition containing the polymer. General formula () General formula () (In the formula, R ¹ and R ² each represent a hydrogen atom or a methyl group, n and p each represent an integer of 1 to 8, and m and q each represent an integer of 1 to 19.)