JPH0359563A - Developer and image forming method - Google Patents

Abstract

PURPOSE:To obtain high-quality images which are free from toner contamination and fogging by making combination use of the fine particles of a specific positive chargeable resin with specific inorg. fine powder. CONSTITUTION:An electrifying member is brought into contact with a body to be electrified and a voltage is impressed thereto from the outside to electrify the member. The member is developed by using a developer contg. a toner, the fine particles of the positive chargeable resin having 0.03 to 1.0mum average grain size and 10<6> to 10<9>OMEGA.cm specific electric resistance and the hydrophobic inorg. fine powder. The particles of the positive chargeable resin act to adsorb the fine powder of free silica on the surface. The particles of the positive chargeable resin slipped from the cleaning blade of an image forming device having a contact electrifying device are attracted to the contact electrifying member and thereafter, the free inorg. fine powder slipped from the cleaning blade is attracted on the surface to protect the surface of the photosensitive body. The high-quality images which are free from the toner contamination and fogging are thus obtd.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a developer and an image forming method for visualizing electrostatic images in image forming methods such as electrophotography, electrostatic recording, and electrostatic printing. . More specifically, when an IT member to which a voltage is applied from the outside is brought into contact with an energized member! The present invention relates to a developer used in electrophotography and an image forming method that includes a charging step of applying electricity.

[Prior Art] Conventionally, in electrophotographic devices, etc. A corona discharger is known as a cage means. However, corona dischargers have problems such as the need to apply high voltage and the generation of a large amount of ozone.

Therefore, recently, consideration has been given to using a contact cage means without using a corona discharger.

Specifically, a voltage is applied to a conductive roller, which is a charging member, and the roller is brought into contact with a photoreceptor, which is an object to be charged, so that the surface of the photoreceptor is charged to a predetermined potential. If such contact charging means is used, the voltage can be lowered compared to a corona discharger, and the amount of ozone generated can also be reduced.

For example, in Japanese Patent Publication No. 50-13661, it is possible to apply a low voltage when charging photosensitive paper by using a roller whose core metal is coated with a dielectric material made of nylon or polyurethane rubber.

However, in the above-mentioned conventional example, when the core metal is coated with nylon, it does not have the elasticity of rubber or the like, so it cannot maintain sufficient contact with the object to be charged, resulting in charging failure. On the other hand, when the core metal is coated with urethane rubber, the softening agent impregnated into the rubber material seeps out, and when a photoconductor is used as the subject of electricity, the charging member is in contact with the photoconductor when the photoconductor stops. There is a problem in that the image sticks to the area or the image becomes blurred in that area. In addition, if the softener in the rubber material of the charging member seeps out and adheres to the surface of the photoreceptor, the resistance of the photoreceptor becomes low and image deletion occurs, making it unusable in severe cases or toner remaining on the surface of the photoreceptor. may adhere to the surface of the f-type 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 becomes insulated, the charging member loses its f-electrification ability, and the surface of the photoreceptor becomes non-uniformly charged, which affects the image.

This is because the developer is more strongly pressed against the surface of the photoreceptor by the charging member, which tends to cause residual developer to stick to the charging member and the surface of the charged object, as well as to cause scratches and abrasions.

In the contact charging device according to the present invention, a DC voltage or a DC voltage superimposed with an AC voltage is applied to the charging member. The abnormal -f charge and routine motion of the residual developer, which is small in diameter and light in weight, is repeated, and as a result, the residual developer is likely to be electrostatically attracted to or embedded in the charging member or the surface of the photoreceptor drum. The current situation is very different from the case of using non-contact charging means using a conventional corona discharger.

On the other hand, in recent years, small and inexpensive personal copying machines and laser printers have appeared, and these small machines use cartridges that integrate the photoreceptor, developer, cleaning device, etc. for maintenance-free purposes. It is desirable to use a magnetic component type developer because the structure of the developing device can be simplified.

In a method using such a magnetic dry developer, in order to form a visible image of good quality, it is necessary for the developer to have high fluidity and uniform IFt properties. Conventionally, fine silicic acid powder has been added and mixed to toner powder. However, since silicic acid fine powder is wood-philic as it is, developers to which it is added may form condensation due to moisture in the air, resulting in decreased fluidity, or in extreme cases, silica may absorb moisture, causing the developer to deteriorate. Charging performance will deteriorate. Therefore, the use of hydrophobized silicic acid fine powder has been proposed in JP-A-46-5782, JP-A-48-47345, JP-A-48-47346, and the like. Specifically, for example, silicic acid fine powder is reacted with an organosilicon compound such as dimethyldichlorosilane, and the silanol groups on the surface of the silicic acid fine powder are replaced with organic groups.
Hydrophobized silicic acid fine powder is used.

Such magnetic toner has a strong abrasive effect, and is particularly difficult to use in image forming processes where it is pressed against a photoconductor with a low surface hardness such as an organic photoconductor (OPC). With a developer externally added with acid fine powder, white spots occur due to scraping of the surface of the pressure contact member and photoreceptor, and toner fusion occurs due to scratches on the pressure contact member and photoreceptor.

Contamination of the photoreceptor such as fill-in contamination is likely to occur, and if it is severe, image defects may occur.

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

Another object of the present invention is to provide a developer and an image forming method that do not easily contaminate a contact charging device and do not cause charging unevenness even if the contact charging device is contaminated.

Another object of the present invention is to provide a developer and an image forming method capable of producing high-density, fog-free images.

Means and operation for solving the problem] The present invention includes a step of bringing a charging member into contact with a charged object and applying a voltage from the outside to perform charging, a toner, and an average particle size of 0.0:3 to 1. ．．
A developer and an image used in an image forming apparatus having a developing step using a developer containing OH, positively charged resin fine particles (A) having a specific electric resistance lO6 to 109 Ω・am, and a hydrophobic inorganic fine powder (B) Regarding the forming method.

The reason why positively chargeable resin particles exhibit an effect on photoreceptor fusion in the present invention is considered to be as follows.

First, photoreceptor fusion is caused by scratches caused when inorganic fine powder is rubbed against the photoreceptor surface by an abutting member, and removal of free inorganic fine powder is effective in preventing photoreceptor fusion. The positively charged resin particles of the present invention have the function of adsorbing this free silica fine powder to the surface, which is clear from observation with a scanning electron microscope.

In addition, in an image forming apparatus equipped with a contact charging device, the positively charged resin particles that have slipped through the cleaning blade are adsorbed by the contact charging member, and then the free inorganic fine powder that has slipped through the cleaning blade is further adsorbed onto the surface of the photoreceptor. It is thought to protect the surface.

The positively charged resin fine particles used in the present invention have an average primary particle diameter of 0.03 to 1.0 μm, preferably 0.05 to 0.8 μm. 1. Oui
Larger particles have a small specific surface area, are not suitable for adsorbing free silica, and are less effective in preventing photoreceptor fusion.

Further, the positively charged resin fine particles have a specific electrical resistance of 106 to 1.
06 Ω·cm is used. If a resistor with a resistivity lower than 10 6 Ω·Cm is used, the amount of charge of the developer is decreased, resulting in a decrease in image density. Further, if a resistor having a resistivity higher than 109Ω·Cl11 is used, the fluidity of the developer will be significantly deteriorated, resulting in images with poor fogging.

In addition, the positive 11F electrically conductive resin fine particles (A) are used in an amount of 0.01 to 1.0 parts by weight (preferably 0.03 to 0.57 parts by weight) in 100 parts by weight of the developer. The fine powder (B) is preferably used in an amount of 0.1 to 3.0 parts by weight, and preferably A<B. When A>1.0 parts by weight, image density decreases, and when A<0.01 parts by weight, there is no effect on photoreceptor fusion. Furthermore, if A≧B, the fluidity deteriorates and fog occurs.

Further, the positive chargeable resin fine particles have a triboelectric charge amount of +5Da.
It is preferable that it is c/g~+350ac/g.

If it is less than +50 μc/g, the effect of preventing photoreceptor fusion is small and the image density tends to decrease. When it is larger than +350 μc/g, fluidity deteriorates.

The hydrophobic inorganic fine powder (B) used in the present invention is preferably a hydrophobic metal oxide fine powder, and more preferably a hydrophobic silica fine powder.

In addition, the specific surface area due to nitrogen adsorption measured by BET method is 7.
A range of 0 to 300 m"/g gives good results. Inorganic fine powder o
, i to 3.0 parts by weight, preferably 0.2 to 2.0 parts by weight.

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

The hydrophobic silica fine powder used in the present invention preferably has a tribocharge amount of 1100 μc/g to 13 ouc/g. If the amount of tribocharge is less than 1100 μc/g, the amount of tribocharge of the developer itself is reduced, and the humidity characteristics are deteriorated. In addition, if a material exceeding -300 μc/g is used, the memory of the developer carrier will be promoted.
In addition, it becomes more susceptible to the effects of silica deterioration, etc., which impairs durability characteristics. In addition, if it is finer than 3oom'/g, it has no effect when added to the developer, and if it is coarser than rom'/g, it has a high probability of existing as a free substance, which can cause black spots due to uneven silica accumulation and aggregates. Cheap.

The tribo value of negatively charged silica fine powder is measured by the following method. That is, 0.2 g of silica fine powder left overnight in an environment of 23.5°C and 60% RH and 200 to 300
Carrier iron powder that is not coated with resin and has a main particle size in the mesh (for example, EFV200/3 manufactured by Nippon Iron Powder Co., Ltd.)
00) 9.8 g under the above environment, approximately 5
Mix thoroughly (hand shake up and down approximately 50 times for approximately 20 seconds) in a polyethylene lidded mouth bottle having a volume of 0 c, c.

Next, as shown in FIG. 3, approximately 0.5 g of the mixture is placed in a metal measuring container 32 with a 400-mesh screen 33 at the bottom and a metal lid 34 is placed. Measurement container 32 at this time
Weigh the entire weight and let it be L (g). Next, the suction machine 31 (
At least the portion in contact with the measurement container 32 is an insulator), suction is applied from the suction port 37, and the ffl amount control valve 36 is adjusted to set the pressure of the vacuum gauge 35 to 250 mmHg. In this state, suction is applied sufficiently to remove the silica. The potential of the electrometer 39 at this time is assumed to be V (volt). Here, 38 is a capacitor, and the capacitance is C (μF). Furthermore, the weight of the entire measurement container after suction is weighed and is defined as W2 (g). The amount of triboelectric charge (μc/g) of this silica is calculated as shown in the following formula.

As the silicic acid fine powder used in the present invention, both so-called dry silica produced by vapor phase oxidation of a silicon halide compound or dry silica called fumed silica, and so-called wet silica produced from water glass etc. can be used. However, it is preferable to use dry silica, which has fewer silanol groups on the surface and inside the silicic acid fine powder and is free of production residues such as Na, O, So, 2-, etc.

In addition, for dry silica, it is also possible to obtain a composite fine powder of silica and other metal oxides by using other metal halide compounds such as aluminum chloride or titanium chloride together with silicon halide compounds in the manufacturing process. These are also included.

The average primary particle size of the particles is preferably within the range of 0.001 to 2μ, particularly preferably 0.00μ.
It is preferable to use silica fine powder within the range of 2 to 0.2 microns.

Further, for the hydrophobization treatment, conventionally known hydrophobization treatment agents and methods are used.

For the degree of hydrophobicity of the inorganic fine powder in the present invention, a value measured by the following method is used. Of course, other measurement methods can also be used while referring to this measurement method.

1 of ion-exchanged water in a sealed 2 (lomil separating funnel)
Add 00fflf and 0.1 g of the sample, and shake for 10 minutes at 9 Orpm using a shaker (turbo sneaker Kisa-T2C type). After shaking and allowing to stand for 10 minutes to separate the inorganic powder layer and water layer, the lower water layer was
m4 is sampled, placed in a 10 mm cell, and the transmittance is measured at a wavelength of 500 nm using blank ion-exchanged water that does not contain silica fine powder as a reference, and the transmittance value is taken as the degree of hydrophobicity of the inorganic fine powder. It is.

The degree of hydrophobicity of the hydrophobic inorganic fine powder in the present invention is 60%.
or more (more preferably 90% or more). If the degree of hydrophobicity 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 amount of triboelectric charge of the negatively charged resin particles used in the present invention is measured as follows.

That is, 0.2 g of fine resin particles left overnight in an environment of 25° C. and 50% to 60% R)I and a non-resin-coated carrier iron powder having a main particle size of 200 to 300 mesh (for example, EFV20Q/300 manufactured by Iron Powder Company)
99.8 g in an aluminum pot with a volume of approximately 200 cc under the above environment, mixed for 60 minutes, and then heated to a blowing pressure of (1.5 J/cm2) using an aluminum cell with a 400 mesh screen. Hey,
The triboelectric charge amount of the resin particles is measured by the blow-off method.

For measurement of average particle size, Coulter Counter N4
(manufactured by Nikikaki Co., Ltd.) in a state in which it is dispersed in a solvent using ultrasonic waves. Alternatively, it may be measured with (:APA-5000 model (manufactured by Horiba, Ltd.).Furthermore, virtually monodisperse obtained by polymerization method etc. is a scanning micrograph (SEM image) at a magnification of 7500 to 00 times. It may be measured by

The electrical resistivity (volume resistivity) in the present invention is measured, for example, using the apparatus shown in FIG. In the figure, 41 is a pedestal. 42 is a pressing means, which is connected to a hand press and has a pressure gauge 43 attached thereto.

44 is a hard glass cell with a diameter of 3.100 cm, into which a sample 45 is placed. 46 is a brass number press ram, diameter 4
．． 266cm, area 14.2857clQ'. 47 is a stainless steel push rod with a radius of 0.397 cm and an area of 0.
．． At 496 cm2, the pressure from the press ram 46 was
Add to 5. 48 is a brass base, 49 and 50 are Bakelite insulating plates. 51 is a resistance meter connected to the press ram 46 and the stand 48, and 52 is a dial gauge.

In the device shown in Figure 4, the hand press has a hydraulic pressure of 20 kg/
When a pressure of 578 kg/cm is applied to the sample,
'' is applied.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 determine the volume resistivity.

Further, the positively chargeable resin fine particles used in the present invention are preferably spherical, and specifically, the resin fine particles have a ratio of the short axis to the long axis (major axis/breadth axis) of 1.0 to 1.02. Excellent in preventing photoreceptor fusion. 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,
Diethylaminoethyl methacrylamide 5 dimethylacinoethyl methacrylamide, 4-vinylpyridine, 2-
Resin particles copolymerized with vinyl monomers such as vinyl pyridine or mixtures of these monomers are used.

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

It is also preferred in the present invention that the surface may be crosslinked with divinylbenzene or the like, and the surface may be treated with a metal, metal oxide, pigment, dye, surfactant, etc. in order to adjust the specific electrical resistance and tribocharge amount. It is a form.

As the binder resin of the toner according to the present invention, styrene and substituted products thereof such as polystyrene and polyvinyltoluene can be used! #Polymer: Styrene-brobylene copolymer, styrene-vinyltoluene copolymer.

Styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylamino acrylate Ethyl copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer.

Styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether copolymer, styrene-vinylethyl ether copolymer.

Styrenic copolymers such as styrene-vinylmethylketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid copolymer, and styrene-maleic acid ester copolymer; polymethyl methacrylate , polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin.

Terpene resin, phenolic 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 coloring materials that can be further added to the toner according to the present invention, conventionally known carbon black, copper phthalocyanine, iron black, etc. can be used.

Further, in the present invention, a magnetic developer is preferable. As the magnetic fine particles contained in the magnetic toner of the present invention, a substance that is magnetized when placed in a magnetic field is used, such as powder of a ferromagnetic metal such as iron, cobalt, or nickel, or magnetite,
γ-Fe, 0. ．． Alloys and compounds such as ferrite can be used.

These magnetic fine particles preferably have a BET specific surface area of 1 to 2 om2/g, especially 2.5 to 12 m2 by nitrogen adsorption method.
2/g, and preferably a magnetic powder having a Mohs hardness of 5 to 7. The content of this magnetic powder is 10 to 70% based on the weight of the toner.
Good weight percentage.

In addition, the toner of the present invention preferably has negative chargeability (it may contain a charge control agent if necessary, and may contain a negative charge control agent such as a metal complex salt of a monoazo dye, a gold R complex salt of salicylic acid, alkylsalicylic acid, dialkylsalicylic acid, or naphthoic acid). A control agent is used. Furthermore, it is preferable that the magnetic toner according to the present invention has a volume resistivity of 10 10 Ω·cm or more, particularly 10 9 Ω·cm or more, from the viewpoint of triboelectric charge and electrostatic transferability.

The volume resistivity mentioned here is 100kg/cm for toner.
It is defined as the value calculated from the current value after 1 minute has passed after molding with a pressure of 2 and applying an electric field of 100 V/cm to this.

The developer of the present invention may further contain other additives, such as a fixing aid (for example, low molecular weight polyethylene), or a metal oxide such as tin oxide as a conductivity imparting agent, as long as it does not have a substantial adverse effect. You can also add it.

In producing the toner of the present invention, the constituent materials are thoroughly kneaded using a thermal kneader such as a hot roll, kneader, or extruder, and then mechanically crushed or classified, or the materials are mixed in a binder resin solution. A method of producing a toner by dispersing and then spray drying, or a polymerization method of producing a toner by mixing a predetermined material with a vehicle body that constitutes a binder resin to form an emulsified suspension and then polymerizing it. , each method can be applied.

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

FIG. 1 is a schematic diagram of a contact charging device showing an embodiment of the present invention. Reference numeral 1 denotes a photoconductor drum which is a charged body, and is made by forming an organic photoconductor (OPC) 1b which is a photoconductor layer on the outer peripheral surface of a drum base 1a made mainly of aluminum. Rotate at speed. In this embodiment, the photosensitive drum 1 has an outer diameter of 30 mmφ. 2 is a charging roller which is a charging member brought into contact with the photosensitive drum 1 with a predetermined pressure, a metal core 28 is provided with a conductive rubber layer 2b, and a surface layer 2C which is a releasable film is provided on the circumferential surface of the conductive rubber layer 2b. has been established. The surface layer in this example is a releasable film, and it is preferable to provide a releasable film in view of matching with the developer and image forming method of the present invention. However, if the resistance of the release film is too high, the photoreceptor drum 1 will not be charged, and if the resistance is too small, too much voltage will be applied to the photoreceptor drum 1, causing damage to the drum and the formation of pinholes. The resistance, that is, the volume resistivity, is preferably 109 to 101 Ωm, and the thickness of the releasable film at this time is preferably 3.0 μm or less.

Further, the lower limit of the thickness of the coating is considered to be about 5 μm, as long as the coating does not peel off or crease.

In this embodiment, the outer diameter of the charging roller 2 is 12 amφ, the conductive rubber layer 2b is made of EPDM, and the surface layer 2C has a thickness of 10 am.
μm nylon resin was used. The hardness of the charging roller 2 was 54.5' (ASKER-C). E is a power supply unit that applies voltage to the charging roller 2, and supplies a predetermined voltage to the core metal 28 of the charging roller 2. In FIG. 1, E indicates a DC voltage, but it is preferable to use an AC voltage superimposed on a 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, p AC frequency 50 to 3000H2 DC voltage -200 to -900v Fig. 2 is a schematic configuration diagram of a contact charging member showing another embodiment of the present invention. It is. Components common to those of the device shown in FIG. 1 are designated by the same reference numerals and will not be described again.

The contact charging member 2' of this embodiment is a blade-shaped member brought into contact with the photoreceptor drum 1 in the forward direction with a predetermined pressure, and this blade 2' is a metal support member 2 to which voltage is supplied.
A conductive rubber 2'b is supported on 'a', and a surface layer 2'c serving as a releasable film is provided at the portion in contact with the photoreceptor drum 1. Nylon with a thickness of 10 μm was used as the surface layer 2'c. According to this embodiment, there is no problem such as adhesion between the blade and the photoreceptor drum, and the same effects as in the previous embodiment can be obtained.

In the above-described embodiments, a roller-shaped or blade-shaped charging member is used, but the present invention is not limited to this, and the present invention can be practiced with other shapes as well.

In addition, in this embodiment, the charging member is composed of a conductive rubber layer and a release film, but the charging member is not limited to this. It is preferable to form a resistive layer, for example, a hydrin rubber layer with small environmental fluctuations.

Also, as a mold release coating, PV is used instead of nylon resin.
F (polyvinylidene fluoride) and PVDC (polyvinylidene chloride) may also be used. As the photoreceptor, amorphous silicon, selenium, ZnO, etc. can also be used. In particular, when amorphous silicon is used for the photoreceptor, compared to when other materials are used, if even a small amount of the softener in the conductive rubber layer adheres to the photoreceptor, image fading will become severe. The effect of applying an insulating film is significant.

In addition, in the cleaning process according to the present invention, the photosensitive drum after the toner image is generally transferred is wiped off by a cleaning member such as a cleaner blade or roller to make the surface of the photosensitive drum clean. It is subjected to image formation repeatedly.

Further, it is also possible to perform such a cleaning step simultaneously during a charging step, a developing step, or a transfer step related to electrophotography.

The present invention is particularly effective for image forming apparatuses in which the surface of the latent image carrier is made of an organic compound. When an organic compound forms the surface layer, it has good adhesion with the binder resin contained in the toner, and especially when the same material is used, a chemical bond occurs at the contact point, resulting in poor transferability. This is because the

As the surface material of the latent image carrier used in the present invention, silicone resin, vinylidene chloride, ethylene-PVC, styrene-
Acrylonitrile, styrene-methyl methacrylate,
Examples include styrene, polyethylene terephthalate, polycarbonate, etc., but are not limited to these. Copolymerization or blending of other styrenes or exemplified resins can also be used.

The present invention is particularly effective for image forming apparatuses 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 linear pressure is the same, the curvature is large, so pressure concentration tends to occur at the contact area.

It is thought that the same phenomenon occurs with a belt photoreceptor, and it is also effective for image forming apparatuses having a radius of curvature of 25+nm or less at the transfer section.

[Example] The basic structure and features of the present invention have been described above, and the method of the present invention will be specifically explained based on Examples below. However, this does not limit the embodiments of the present invention in any way. Parts in the examples are parts by weight.

The above mixture is melt-kneaded with a twin-screw extruder heated to 140°C, the cooled mixture is coarsely pulverized with a hammer mill, the coarsely pulverized material is pulverized with a jet mill, and the resulting finely pulverized powder is The mixture was classified to obtain 7 g (60° C.) of magnetic particle divided powder [toner] (I) having a volume average particle diameter of 12 Pm.

A magnetic particle sifted powder [toner] (II) (Tg 55° C.) was obtained using the above components in the same manner as in Production Example 1.

[Examples and Comparative Examples] Positively chargeable resin fine particles and silica fine powder were added to the above-mentioned magnetic particle divided powder and mixed in a Henschel mixer to produce a toner to which positively chargeable resin fine particles and silica fine powder were externally added. A developer having the following properties was obtained.

Next, these prepared individual magnetic developers were applied to an image forming apparatus (L made by Canon) having a contact charging device as shown in FIG.
DC voltage and AC voltage (1
50Hz, 1500Vpp) was applied and 4 sheets (A4)/
A live-action test was conducted at room temperature (25℃, 60% RH) in which toner images are continuously formed using the reversal development method at a printing speed of 1 minute.
), and the printout images were evaluated. At the same time, 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 particles, Table 2 shows the physical properties of the hydrophobic silica, and Table 3 shows the composition and evaluation results of the developer. The charging device used was the roller type shown in FIG. 1 except for the blade type shown in FIG. 2 in Example 4.

The evaluation criteria are shown below.

Fogging ○... is very bad △... It is foggy but it can be used for practical purposes ×... It is not practical Photoreceptor fusion ○ ... Not fused at all ○△... 1 in A4 peta black ～3 points of fusion △ ・・・A
3 to 10 points of fusion in 4 solid black x ...10 or more fusions in A4 solid black (hereinafter referred to as margin) [Effect of the invention] According to the present invention, a specific inorganic fine powder can be When used in conjunction with positively charged resin particles, free inorganic fine particles are adsorbed onto the photoreceptor surface, which protects the photoreceptor surface, making it possible to obtain high-quality images without toner contamination or fogging. .

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an outline of a charging roller of the present invention, Fig. 2 is an explanatory diagram showing an outline of a blade which is another embodiment of the invention, and Fig. 3 is an explanatory diagram showing an outline of a blade which is another embodiment of the invention. Schematic,
FIG. 4 is an explanatory diagram of the electrical resistivity measuring device. 1...Photosensitive drum 2.2'...Charging member E...Power source

Claims (2)

[Claims] (1) A developer used in an image forming method comprising a charging step of bringing a charging member into contact with an object to be charged and applying a voltage from the outside to perform charging, and a developing step of developing an electrostatic image, the developer comprising: The developer is toner and has an average particle size of 0.03 to 1.0μ
A developer characterized by containing positively chargeable resin fine particles (A) and hydrophobic inorganic fine powder (B) having a volumetric electrical resistance of 10^6 to 10^9 Ω·cm. (2) {1} A charging process in which the charging member is brought into contact with the object to be charged and a voltage is applied from the outside to perform charging; {2} The toner has an average particle size of 0.03 to 1.0 μm and a volume electrical resistance of 10 An image forming method comprising: a developing step using a developer containing positively chargeable resin fine particles (A) and hydrophobic inorganic fine powder (B) of ^6 to 10^9 Ω·cm.