JP2759510B2 - Developer and image forming method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer for visualizing an electrostatic image in an image forming method such as electrophotography, electrostatic recording, and electrostatic printing, and an image forming method. . More specifically, the present invention relates to a developer and an image forming method used in electrophotography, which include a charging step of charging a member to be charged by applying a voltage from outside to a member to be charged.

[Related Art] Conventionally, a corona discharger has been known as a charging unit in an electrophotographic apparatus or the like. However, corona dischargers have problems such as the need to apply a high voltage and the generation of a large amount of ozone.

Therefore, recently, the use of contact charging means without using a corona discharger has been studied. More specifically, a voltage is applied to a conductive roller serving as a charging member, and the roller is brought into contact with a photosensitive member serving as a charged member to charge the surface of the photosensitive member to a predetermined potential. If such a contact charging means is used, the voltage can be reduced as compared with a corona discharger, and the amount of generated ozone can be reduced.

For example, in Japanese Patent Publication No. 50-13661, a low voltage can be applied when photosensitive paper is charged by using a roller having a core covered with a dielectric material made of nylon or polyurethane rubber.

However, in the above conventional example, when the core metal is coated with nylon, there is no elasticity of rubber or the like, so that sufficient contact with the member to be charged cannot be maintained, and poor charging occurs.
On the other hand, when the core metal is coated with polyurethane rubber, the softening agent impregnated in the rubber-based material exudes, and when the photoreceptor is used as the charged body, the charging member sticks to the photoreceptor when the photoreceptor stops at the contact portion. Or the area may cause image blurring. Also, when the softener in the rubber material of the charging member seeps out and adheres to the surface of the photoreceptor,
When the resistance of the photoreceptor is reduced and image flow occurs, the use of the photoreceptor becomes unusable at times. In other cases, toner remaining on the surface of the photoreceptor adheres to the surface of the charging member, causing a filming phenomenon. When a large amount of toner adheres to the surface of the charging member, the surface of the charging member is insulated, and the charging ability of the charging member is lost, so that the charging of the surface of the photoreceptor becomes non-uniform, thereby affecting an image.

This is because the developer is more strongly pressed against the surface of the photoreceptor, so that the residual developer adheres to the surface of the member to be charged or the surface of the member to be charged.

In the contact charging device according to the present invention, a DC voltage or a DC voltage obtained by superimposing an AC voltage is applied to the charging member and used. At this time, particles around the contact portion between the charging member and the photosensitive drum are particularly damaged. Abnormal charging and flying movement of the residual developer having a small diameter and light weight are repeated, which makes it easy for the residual developer to be electrostatically attracted and embedded on the charging member and the surface of the photosensitive drum. This is very different from the case where non-contact charging means using a conventional corona discharger is used.

On the other hand, in recent years, small and inexpensive personal course copiers and laser printers have emerged. In these small machines, from the maintenance-free standpoint, a cartridge integrating a photoconductor, a developing device, a cleaning device, and the like has been developed. It is desirable to use a magnetic one-component type developer because the system is used and the structure of the developing device can be simplified as the developer.

In a method using such a dry developer, in order to form a visible image with good image quality, the developer needs to have high fluidity and uniform chargeability. Conventionally, fine silica powder has been added to and mixed with toner powder. However, since silica fine powder is hydrophilic as it is, the developer to which it is added agglomerates due to the moisture in the air and the fluidity decreases, and in extreme cases, the charging performance of the developer due to the moisture absorption of silica Is reduced. Therefore, use of fine silica powder subjected to hydrophobizing treatment is disclosed in JP-A-46-5792 and JP-A-48-47.
No. 345, JP-A-48-47346 and the like. Specifically, for example, a silicic acid fine powder that has been hydrophobized by reacting a silicic acid fine powder with an organosilicon compound such as dimethyldichlorosilane and replacing the silanol groups on the surface of the silicic acid fine powder with an organic group is used. I have.

Such a magnetic toner has a strong polishing effect on the toner itself, and is particularly suitable for an image forming process in which a photosensitive member having a low surface hardness such as an organic photoconductor (OPC) is pressed against the photosensitive member. In the developer with acid fine powder externally added, the whitening phenomenon caused by scraping the pressing member and the photoconductor surface, the fusion of the toner due to scratching the pressing member and the photoconductor, and the photoconductor contamination such as filming are caused. It is easy to occur, and in extreme cases, image loss occurs.

[Problems to be Solved by the Invention] An object of the present invention is to provide a developer and an image forming method which do not cause toner fusion on a photoreceptor even in an image forming apparatus having a contact charging step.

Another object of the present invention is to provide a developer and an image forming method which are less likely to contaminate a contact charging device and which do not cause uneven charging even if contaminated.

Another object of the present invention is to provide a developer and an image forming method capable of obtaining an image having a high density and no fog.

Means and Action for Solving the Problems According to the present invention, there is provided a process in which a charging member is brought into contact with a member to be charged and a voltage is externally applied to perform charging, a toner, and a toner.
Positively-chargeable resin fine particles (A) having a specific electric resistance of 0.03 to 1.0 μm and specific electric resistance of 10 ⁶ to 10 ⁹ Ω · cm, fine powder of fatty acid metal salt (B), and hydrophobic inorganic fine powder treated with silicone oil or varnish (C) And a method for forming an image.

In the present invention, the positively-chargeable spherical resin particles, a developer containing a fatty acid metal salt fine powder and an inorganic fine powder treated with silicone oil or varnish show the effect on toner fusion to the photoreceptor is as follows. There may be a reason.

First, the cause of the fusion of the toner on the photoreceptor is a scratch when the inorganic fine powder is rubbed against the photoreceptor surface by a contact member during copying or printing. It is close contact. In this case, the presence of a part of the inorganic fine powder in a free state from the toner particles or the like promotes the generation of scratches on the surface of the photoreceptor.

In the toner according to the present invention, the specific electric resistance is 10 ⁶ to 10 ⁹ Ω.
The negatively-chargeable spherical resin fine particles of cm have a function of adsorbing the inorganic fine powder treated with silicone oil or varnish on the surface thereof, which is apparent even by observation with a scanning electron microscope.

Since the adsorbed inorganic fine powder is not in a free state, the silicone oil or varnish is appropriately supplied without damaging the photoreceptor surface, and a thin film is formed on the photoreceptor surface together with the fatty acid metal salt fine powder to reduce frictional resistance and surface energy. The reduction further prevents scratches on the photoreceptor surface and toner adhesion.

With this effect, a higher effect can be achieved under more severe conditions for preventing the toner from being fused on the photoconductor according to the toner of the present invention.

Further, in an image forming apparatus having a contact charging device, the negatively chargeable resin particles slipped from the cleaning blade are adsorbed to the contact charging member, and then the free inorganic fine powder slipping off from the cleaning blade is further adsorbed to the surface, and the photosensitive member is charged. It is thought to be protecting the surface.

In recent years, a laser beam printer having a high printing speed has been demanded with the advancement of the performance of a host computer. At the same time, an image forming apparatus free of ozone generation is desired from the viewpoint of office environment.

Generally, in contact charging, it is necessary to increase the applied voltage and the AC frequency as the process speed increases in order to stabilize the charging on the photoreceptor, but at the same time, the developer is easily fused to the photoreceptor. Has disadvantages.

The present inventors have developed an image obtained by using a positive electrode chargeable resin particle having specific physical properties (particle size, specific electrical resistance) and a fine particle of a fatty acid metal salt in combination with an inorganic fine particle treated with silicone oil, and a contact charging device. It has been found that the use of a forming method can prevent generation of ozone and prevent fusion of a developer to a photoreceptor.

The positively chargeable resin fine particles used in the present invention have a primary average particle size of 0.03 to 1.0 μm, preferably 0.05 to 1.0 μm.
0.80.8 μm is used. Those having a size larger than 1.0 μm have a small specific surface area and are not suitable for adsorbing free silica, and have a small effect of preventing fusion of the photoconductor.

Also, the specific electric resistance of the positively charged resin fine particles is 10 ⁶ to 10 ⁹
Ω · cm is used. When the density is lower than 10 ⁶ Ω · cm, the charge amount of the developer is reduced, and as a result, the image density is reduced. Further, when the density is higher than 10 ⁹ Ω · cm, the fluidity of the developer is deteriorated, and an image with much fog is obtained.

The positively chargeable resin fine particles (A) are contained in an amount of 0.01 to 1.0 part by weight (preferably 0.03 to 0.57 part by weight) per 100 parts by weight of the developer.
Used in the range. When A> 1.0 parts by weight, the image density is reduced, and when A <0.01 parts by weight, there is no effect on the fusion of the photosensitive member.

In addition, the positively chargeable resin fine particles have a triboelectric charge of +50 μc /
g to +350 μc / g is preferred. If it is less than +50 μc / g, the effect of preventing the fusion of the photoconductor is small, and the image density tends to be reduced. If it is larger than +350 μc / g, the fluidity will be deteriorated.

It is preferable that the fatty acid metal salt fine powder (B) used in the present invention is positively chargeable and difficult to be transferred. The primary average particle diameter is preferably 1 μm or less, and the fatty acid preferably has 12 or more carbon atoms.

Further, the hydrophobic inorganic fine powder (C) treated with silicone oil or varnish used in the present invention is preferably a hydrophobic metal oxide fine powder, and more preferably a hydrophobic silica fine powder.

Specific surface area by nitrogen adsorption measured by BET method is 70 to 300 m ²
Those in the range of / g give good results. Magnetic toner 10
The inorganic fine powder is used in an amount of 0.1 to 3.0 parts by weight, preferably 0.2 to 2.0 parts by weight, based on 0 parts by weight.

As the hydrophobic silica fine powder, negatively chargeable hydrophobic silica fine powder is preferable.

The amount of A + B> C and 4B <C is used in the developer of the present invention. When A + B> C, the fluidity deteriorates and fog increases, and when 4B> C, the developer carrier and the photosensitive member contact material are stained, resulting in a decrease in density and image unevenness.

As the hydrophobic silica fine powder used in the present invention, those having a triboelectric charge of −100 μc / g to −300 μc / g are preferably used. If the triboelectric charge is less than -100 μc / g,
The triboelectric charge of the developer itself is reduced, and the humidity characteristics are reduced. On the other hand, if the amount exceeds -300 μc / g, the memory of the developer carrier is promoted, and the effect of the deterioration of silica or the like is liable to occur, which impairs the durability characteristics. Also,
Those finer than 300 m ² / g have no effect on the
Those having a particle size of more than 0 m ² / g have a high probability of being present as a free substance, and are likely to cause black spots due to uneven deposition of silica or aggregates.

The tribo value of the negatively charged silica fine powder is measured by the following method. That is, a carrier iron powder not coated with a resin having a main particle size of 0.2 g of silica fine powder and 200 to 300 mesh which has been left overnight in an environment of 23.5 ° C. and 60% RH (for example, manufactured by Nippon Iron Powder Co., Ltd.) 9.8 g of EFV200 / 300) was accurately weighed under the above-mentioned environment, and sufficiently weighed in a wide-mouthed bottle with a capacity of 50 c.c.
Mix for 2 seconds).

Next, as shown in Fig. 3, a 400 mesh screen 3
About 0.5 g of the mixture is placed in a metal measuring container 32 having a metal cover 3 and a metal lid 34 is provided. At this time, the weight of the entire measurement container 32 is weighed and set as W ₁ (g). Next, in the suction device 31 (at least a portion in contact with the measuring container 32 is an insulator), the pressure of the vacuum gauge 35 is adjusted to 250 mmH by adjusting the air volume control valve 36 by suctioning from the suction port 37.
g. In this state, suction is sufficiently performed to remove silica by suction. At this time, the potential of the electrometer 39 is set to V (volt). Here, 38 is a capacitor, whose capacity is C (μF). In addition, weigh the entire measurement container after suction and weigh W
₂ (g). The triboelectric charge (μc / g) of this silica is calculated as shown below.

The fine silica powder used in the present invention uses both a so-called dry method produced by vapor phase oxidation of a silicon halide compound or a dry silica called fumed silica, and a so-called wet silica produced from water glass or the like. possible it is less silanol groups on the inner surface and fine silica powder, and Na ₂ O, who dry silica without producing residue of SO ₃ ^2-like.

In the case of fumed silica, for example,
By using another metal halide such as aluminum chloride or titanium chloride together with a silicon halide, a composite fine powder of silica and another metal oxide can be obtained, and these are also included.

The average particle diameter is preferably in the range of 0.001 to 2 μm, particularly preferably 0.002 to 0.2 μm.
It is preferable to use silica fine powder in the range of μ.

In the silicon oil treatment of the fine powder used in the present invention, the silanol group can be completely covered by applying the silicon oil to the surface of the silicic acid fine powder, and the moisture resistance is dramatically improved.

Silicon oil or silicone varnish solids used in the present invention is generally represented by the following formula, R: C _1-3 alkyl group R ′: Silicon oil modified group such as alkyl, halogen-modified alkyl, phenyl, modified phenyl R ″: C _1-3 alkyl group or alkoxy group For example, dimethyl silicone oil, alkyl-modified silicon Oil, α-methylstyrene modified silicone oil,
Chlorphenyl silicone oil, fluorine-modified silicone oil and the like can be mentioned. The silicone oil preferably has a viscosity at 25 ° C. of about 50 to 1000 centistokes. Silicone oil with too low molecular weight may generate volatiles due to heat treatment, etc.
On the other hand, if the molecular weight is too high, the viscosity becomes too high and the processing operation becomes difficult.

Known technology is used for the method of silicon oil treatment,
For example, the fine powder and the silicone oil may be directly mixed using a mixer such as a Henschel mixer, or a method of spraying the silicone oil on the base silica may be used. Alternatively, it may be prepared by dissolving or dispersing silicon oil in an appropriate solvent, mixing with a base silica fine powder, and removing the solvent.

It is more preferable that the fine powder used in the present invention is first treated with a silane coupling agent and then treated with a silicon oil or a silicon varnish.

In general, only silicon oil treatment requires a large amount of silicon oil to cover the surface of the fine powder, which tends to cause agglomeration of the fine powder during processing, and that when applied to a developer, the fluidity of the developer may deteriorate. It is necessary to pay close attention to the processing steps of silicon oil. Therefore, in order to remove the agglomerates of the fine powder while maintaining good moisture resistance, it is better to treat the fine silica powder with a silane coupling agent and then treat it with silicon oil, so that the processing effect of the silicon oil can be sufficiently exhibited. That's what it means.

The silane coupling agent used in the present invention has a general formula R _m SiY _n R: an alkoxy group or a chlorine atom m: an integer of 1 to 3. n: an integer of 3 to 1, for example, typically dimethyldichlorosilane, trimethylchlorosilane, allyldimethylchlorosilane, hexamethyldisilazane, allylphenyldichlorosilane, benzyldimethylchlorosilane, vinyltriethoxy Examples thereof include silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, divinylchlorosilane, and dimethylvinylchlorosilane.

The silane coupling agent treatment of the fine powder is a dry process of reacting a vaporized silane coupling agent to a cloud of fine powder by stirring or the like, or a silane coupling agent in which the fine powder is dispersed in a solvent. The treatment can be performed by a generally known method such as a wet method in which a drop reaction is performed.

The treatment amount of the silicone oil or silicone varnish in the present invention is preferably 1 to 35%, more preferably 2 to 30%, based on the specific surface area of the fine powder. The reason for limiting the processing amount is
If the silicon oil treatment amount is too small, the same result as in the case of the silane coupling agent treatment alone will not be obtained, and the moisture resistance will not be improved, and the fine powder will absorb moisture under high humidity, and a high-quality copy image will not be obtained. On the other hand, if the amount of the processed silicon oil is too large, the above-mentioned aggregates of the fine powder are likely to be formed, and moreover, free silicon oil is formed.
When applied to a developer, drawbacks such as the inability to improve fluidity arise.

The degree of hydrophobicity of the inorganic fine powder in the present invention uses a value measured by the following method. Of course, other measurement methods can be applied with reference to this measurement method.

100 ml of ion-exchanged water and 0.1 g of a sample are placed in a sealed stopper 200 ml separatory funnel, and shaken at 90 rpm for 10 minutes with a shaker (Tavla shaker mixer T2C type). After shaking, let stand for 10 minutes.After the inorganic powder layer and the aqueous layer are separated, collect 20-30 ml of the lower aqueous layer, put it in a 10 mm cell, and put a blank ion without a silica fine powder at a wavelength of 500 nm. The transmittance is measured based on the exchanged water, and the value of the transmittance is used as the degree of hydrophobicity of the inorganic fine powder.

The hydrophobicity of the hydrophobic inorganic fine powder in the present invention is 60%.
(More preferably 90% or more). Hydrophobic degree
If it is less than 90%, it is difficult to obtain a high-quality image due to moisture adsorption of the inorganic fine powder under high humidity.

The triboelectric charge amount of the negatively chargeable resin particles used in the present invention is measured as follows.

That is, a carrier iron powder not coated with resin having a particle size of 0.2 g and a main particle size of 200 to 300 mesh, which has been left overnight in an environment of 25 ° C. and 50 to 60% RH (for example,
99.8 g of EFV200 / 300 manufactured by Nippon Tekko Co., Ltd. was placed in an aluminum pot having a volume of about 200
After mixing for minutes, the triboelectric charge of the resin fine particles is measured by a blow-off method using an aluminum cell having a 400 mesh screen at a blowing pressure of 0.5 kg / cm ² .

For measurement of average particle size, see Coulter Counter N4
(Manufactured by Nikkaki Co., Ltd.) in a state of being dispersed in a solvent by ultrasonic waves. Alternatively, measurement may be performed using a CAPA-5000 type (manufactured by Horiba, Ltd.). The virtually monodispersed one obtained by the polymerization method or the like is a scanning micrograph (SEM) at a magnification of 7500 to 10,000 times.
Image).

The measurement of the electrical specific resistance (volume resistivity) in the present invention is performed by, for example, the apparatus shown in FIG. In the figure, 41 is a pedestal. Reference numeral 42 denotes a pressing means, which is connected to a hand press and has a pressure gauge 43 attached. Reference numeral 44 denotes a hard glass cell having a diameter of 3.100 cm, into which a sample 45 is placed. 46 is a press ram made of brass, with a diameter of 4.266 cm and an area of 14.2857 cm ² . Reference numeral 47 denotes a stainless steel push rod having a radius of 0.397 cm and an area of 0.496 cm ² , and applies pressure from a press ram 46 to a sample 45. 48 is a brass base. 49 and 50 are bakelite insulation boards. Reference numeral 51 denotes an ohmmeter connected to the press ram 46 and the table 48, and reference numeral 52 denotes a dial gauge.

In the apparatus of FIG. 4, hydraulic 20 kg / cm ² in a hand press
When the pressure is applied, a pressure of 576 kg / cm ² is applied to the sample. The resistance is read from the resistance meter 51, multiplied by the cross-sectional area of the sample, and divided by the height of the sample read from the dial gauge 52 to obtain the volume specific resistance.

The finely chargeable resin fine particles used in the present invention are preferably spherical, and more specifically, those having a ratio of the minor axis to the major axis (major axis / minor axis) of the resin microparticles of 1.0 to 1.02 are preferably fused to the photosensitive member. Excellent prevention effect. The resin fine particles are produced by an emulsion polymerization method, a spray drying method, or the like.

Preferably methyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, N-methyl-N-phenylethyl methacrylate,
Resin particles obtained by copolymerizing a vinyl monomer such as diethylaminoethyl methacrylamide, dimethylaminoethyl methacrylamide, 4-vinylpyridine, 2-vinylpyridine, or a mixture of these monomers are used.

In order to impart positive chargeability to the resin particles, a method of polymerizing a monomer using a nitrogen-containing polymerization initiator may be used.

It is also preferred that the surface is treated with a metal, a metal oxide, a pigment, a dye, a surfactant or the like to adjust the specific electric resistance and the triboelectric charge. It is a form.

Examples of the binder resin of the toner according to the present invention include homopolymers of styrene such as polystyrene and polyvinyltoluene and substituted products thereof; styrene-propylene copolymer, styrene-vinyltoluene copolymer, and styrene-vinylnaphthalene copolymer. Styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate copolymer, styrene- Methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether copolymer, styrene- Vinyl ethyl ether copolymer, styrene Vinyl methyl ketone copolymer, styrene - butadiene copolymer, styrene - isoprene copolymer, styrene - maleic acid copolymer, styrene - styrene copolymer and maleic acid ester copolymers;
Polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene,
Polyvinyl butyral, polyacrylic acid resin, rosin,
Modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, paraffin wax, carnauba wax and the like can be used alone or in combination.

Further, as a coloring material which can be further added to the toner according to the present invention, conventionally known carbon black, copper phthalocyanine, iron black and the like can be used.

In the present invention, a magnetic toner is preferable. As the magnetic fine particles contained in the magnetic toner according to the present invention, a substance that is magnetized when placed in a magnetic field is used, and powder of a ferromagnetic metal such as iron, cobalt, and nickel, or magnetite, γ-Fe ₂ Alloys and compounds such as O ₃ and ferrite can be used.

These magnetic fine particles preferably have a BET specific surface area of 1 to ²⁰ m ² / g, particularly 2.5 to 12 m ² / g, and more preferably a magnetic powder having a Mohs hardness of 5 to 7 by a nitrogen adsorption method. The content of the magnetic powder is preferably from 10 to 70% by weight based on the weight of the toner.

Further, the toner of the present invention preferably has a negative charge property and may contain a charge control agent if necessary. Agent is used. Further, the magnetic toner according to the present invention preferably has a volume resistivity of 10 ¹⁰ Ω · cm or more, particularly preferably 10 ⁹ Ω · cm or more in terms of triboelectric charge and electrostatic transferability. The volume resistivity here means that the toner is molded at a pressure of 100 kg / cm ² ,
An electric field of 100 V / cm is applied to this, and it is defined as a value converted from a current value one minute after the application.

The developer of the present invention may further contain other additives such as a fixing aid (eg, low-molecular-weight polyethylene) or a metal oxide such as tin oxide as a conductivity-imparting agent, as long as it does not substantially adversely affect the developer. May be added.

In the production of the toner of the present invention, the constituent materials are kneaded well by a hot kneader such as a hot roll, kneader, extruder, etc., and then are obtained by mechanical pulverization and classification, or the materials are dispersed in a binder resin solution. After that, a method obtained by spray drying, or a polymerization method for producing a toner by mixing a predetermined material with a monomer to constitute a binder resin to form an emulsion suspension and then polymerizing to obtain a toner, Each method can be applied.

Hereinafter, the contact charging step of the present invention applicable to the developer and the image forming method of the present invention will be specifically described.

FIG. 1 is a schematic configuration diagram of a contact charging device showing one embodiment of the present invention. Reference numeral 1 denotes a photosensitive drum as an object to be charged, which is formed by forming an organic photoconductor (OPC) 1b as a photosensitive layer on an outer peripheral surface of a drum base 1a made of aluminum. Rotate. In this embodiment,
The photosensitive drum 1 has an outer diameter of 30 mmφ. Reference numeral 2 denotes a charging roller which is a charging member brought into contact with the photosensitive drum 1 with a predetermined pressure, and a conductive rubber layer 2b is provided on a metal core 2a, and a surface layer 2c which is a release coating on the peripheral surface thereof. Was provided. The surface layer in this embodiment is a release film, and it is preferable to provide a release film in terms of matching with the developer and the image forming method according to the present invention. However, if the resistance is too large, the photosensitive drum 1 is not charged, and if the resistance is too small, a large voltage is applied to the photosensitive drum 1 too much.
Since the drum is damaged and pinholes are generated, it is preferable that the resistance is appropriate, that is, the volume resistivity is 10 ⁹ to 10 ¹⁴ Ωm, and the thickness of the releasable coating at this time is within 3.0 μm. In addition, the lower limit of the thickness of the film is good if the film is not peeled or blunt.
It is considered about μm.

In this embodiment, the outer diameter of the charging roller 2 is 12 mmφ,
EPDM was used for the conductive rubber layer 2b, and nylon resin having a thickness of 10 μm was used for the surface layer 2c. The hardness of the charging roller 2 is 54.5 ° (AS
KER-C). E is a power supply unit that applies a voltage to the charging roller 2 and supplies a predetermined voltage to the metal core 2 a of the charging roller 2. In FIG. 1, E indicates a DC voltage, but it is preferable that the AC voltage is superimposed on the DC voltage.

 Preferred process conditions in this case are shown below.

Contact pressure 5 to 500 g / cm AC voltage 0.5 to 5 KV _pp AC frequency 50 to 3000 Hz DC voltage -200 to -900 V FIG. 2 is a schematic configuration diagram of a contact charging member showing another embodiment of the present invention. The same reference numerals are given to the same members as those in the apparatus of FIG. 1 described above, and the description will not be repeated.

The contact charging member 2 'of this embodiment is in the form of a blade which is brought into contact with the photosensitive drum 1 in a forward direction at a predetermined pressure, and this blade 2' is electrically connected to a metal supporting member 2'a to which a voltage is supplied. Rubber 2'b is supported, and the photosensitive drum 1
Is provided with a surface layer 2'c to be a release coating. Nylon having a thickness of 10 μm was used as the surface layer 2′c. According to this embodiment, the same function and effect as those of the above embodiment can be obtained without any trouble such as adhesion between the blade and the photosensitive drum.

In the above-described embodiment, a roller-shaped or blade-shaped charging member is used. However, the present invention is not limited to this, and the present invention can be applied to other shapes.

Further, in this embodiment, the charging member is composed of the conductive rubber layer and the release coating, but the invention is not limited to this. It is preferable to form a resistance layer, for example, a hydrin rubber layer with small environmental fluctuation.

Also, PVDF is used as a release coating instead of nylon resin.
(Polyvinylidene fluoride) or PVDC (polyvinylidene chloride) may be used. As the photoconductor, amorphous silicon, selenium, ZnO or the like can be used. In particular, when amorphous silicon is used for the photoconductor, compared to the case where other materials are used, even if the softening agent of the conductive rubber layer adheres to the photoconductor even to a small extent, the image flow becomes severe, so The effect of the insulating coating is great.

In the cleaning step according to the present invention, generally, the photosensitive drum after the transfer of the toner image is cleaned and cleaned by a cleaning member such as a blade or a roller of the cleaner by wiping and removing remaining toner and other contaminants. It is repeatedly used for image formation.

In addition, such a cleaning process involves electrophotography,
It is also possible to carry out the charging step, the developing step, or the transferring step at the same time.

The present invention is particularly effective for an image forming apparatus in which the surface of a latent image carrier is an organic compound. When the organic compound forms the surface layer, it has good adhesion to the binder resin contained in the toner.Particularly, when using the same material, a chemical bond occurs at the contact point, and the transfer property is low. Is to be reduced.

Examples of the surface material of the latent image carrier used in the present invention include, but are not limited to, silicone resin, vinylidene chloride, ethylene-vinyl chloride, styrene-acrylonitrile, styrene-methyl methacrylate, styrene, polyethylene terephthalate, and polycarbonate. However, other monomers or copolymerization or blending between the exemplified resins can also be used.

The present invention is particularly effective for an image forming apparatus in which the diameter of the latent image carrier is 50 mm or less. This is because, in the case of a small-diameter drum, even if the line pressure is the same, the curvature is large, so that the pressure tends to concentrate at the contact portion.

It is considered that the same phenomenon occurs in the belt photoreceptor, and the present invention is also effective for an image forming apparatus having a radius of curvature of 25 mm or less at the transfer section.

[Embodiment] The basic configuration and features of the present invention have been described above. Hereinafter, the method of the present invention will be specifically described based on the embodiments. However, this does not limit the embodiment of the present invention at all. Parts in the examples are parts by weight.

Production Example 1 The above mixture is melt-kneaded in a twin-screw extruder heated to 140 ° C., the cooled kneaded material is roughly pulverized by a hammer mill, the coarsely pulverized material is finely pulverized by a jet mill, and the obtained finely pulverized powder is After classification, a magnetic particle classification powder [toner] (I) (Tg 60 ° C.) having a volume average particle diameter of 12 μm was obtained.

Production Example 2 The above components were used in the same manner as in Production Example 1 to obtain a magnetic particle classified powder [toner] (II) (Tg 55 ° C).

Examples and Comparative Examples A developer having a toner to which the positively chargeable resin fine particles and the silica fine powder are externally added, and the positively chargeable resin fine particles and the silica fine powder are added to the magnetic particle classification powder and mixed with a Henschel mixer. I got

Next, an image forming apparatus having a contact charging device shown in FIG.
DC voltage and AC voltage (600Hz, LBP-8II modified machine)
1500 V _pp ) and a continuous printing test to form a toner image by the reversal development method at a printing speed of 16 sheets (A4) / min at normal temperature and normal humidity (25 ° C, 60% RH). evaluated. At the same time, the appearance of the charging member (roller type) and the surface of the photosensitive drum were observed.

Table 1 shows the physical properties of the positively chargeable resin fine particles, Table 2 shows the physical properties of the hydrophobic silica, and Table 3 shows the composition of the developer and the evaluation results. The charging device used was the roller type shown in FIG. 1 except that the blade type shown in FIG. 2 was used in Example 5.

 The evaluation criteria are shown below.

Fog ○: Almost none △: Fogged, but practically acceptable ×: Impossible Photoconductor fusion ○: No fusion at all ○ △: Fusion of 1 to 3 points in A4 solid black △: A4 solid black 3 to 10 fusion points ×… 10 or more fusion points in A4 solid black [Effects of the Invention] According to the present invention, a positively chargeable resin particle having specific physical properties (particle diameter, specific electrical resistance) is contacted with a developer in which a fatty acid metal salt fine powder is used in combination with a silicone oil-treated inorganic fine powder. By using the present invention in an image forming method having a charging device, it is possible to prevent generation of ozone, prevent fusion of a developer to a photoconductor, and obtain a high-quality image free from toner contamination and fogging.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an outline of a charging roller of the present invention, FIG. 2 is an explanatory view showing an outline of a blade according to another embodiment of the present invention, and FIG. Schematic,
FIG. 4 is an explanatory view of an electric resistivity measuring device. 1. Photosensitive drum, 2, 2 '... Charging member E ... Power supply

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Toyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-64-91142 (JP, A) JP-A-64 JP-A-77075 (JP, A) JP-A-1-113762 (JP, A) JP-A-1-126660 (JP, A) JP-A-1-154163 (JP, A) JP-A-1-177579 (JP, A) (58) Fields surveyed (Int.Cl. ⁶ , DB name) G03G 9/08 G03G 15/02

Claims (2)

(57) [Claims] 1. A developer for use in an image forming method, comprising: a charging step of bringing a charging member into contact with a member to be charged and applying a voltage from the outside to perform charging, and a developing step of developing an electrostatic image. , The developer and the toner, the average particle size 0.03 ~ 1.0μ
m, containing positively chargeable resin fine particles (A) and fatty acid metal salt fine powder (B) having a volume electric resistance of 10 ⁶ to 10 ⁹ Ω · cm, and hydrophobic inorganic fine powder (C) treated with silicone oil or varnish. A developer, characterized in that: 2. A charging step in which a charging member is brought into contact with a member to be charged and a voltage is applied from the outside to perform charging, and a toner, an average particle diameter of 0.03 to 1.0 μm, and a volume electric resistance of 10 ⁶ to 10 ⁶
A developing step using a developer containing 10 ⁹ Ω · cm positively chargeable resin fine particles (A), fatty acid metal salt fine powder (B), and hydrophobic inorganic fine powder (C) treated with silicone oil or varnish; An image forming method comprising: