JPH07120114B2 - Electrophotography - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic method, and more particularly to an electrophotographic method using a one-component magnetic toner as a developer.

[Description of Prior Art]

As the electrophotographic method, U.S. Pat.No. 2,297,691 specification,
Various methods are described in JP-B-42-23910 and JP-B-43-24748, all of which are electrostatically charged on the surface of the photoreceptor having a photoconductive layer by means of corona discharge or the like. Is applied, and an electrostatic latent image is formed by irradiating the photoconductive layer having this charge with a light image corresponding to the original, and then it is called a toner having a polarity opposite to the electrostatic latent image on the electrostatic latent image. Develop the electrostatic latent image by attaching colored fine powder,
After transferring the toner image to a transfer material such as paper, if necessary,
A copy is obtained by fixing with heat, pressure, solvent vapor or the like.

In the step of developing the electrostatic latent image, toner particles charged to a polarity opposite to that of the latent image are attracted by electrostatic attraction and attached to the electrostatic latent image. The methods of developing an image using toner are roughly classified,
There are a method of using a so-called two-component developer in which a toner is dispersed in a medium called a carrier in a small amount, and a method of using a so-called one-component developer in which the toner is used alone without using the carrier.

The method using a two-component developer is one in which toner and carrier are stirred and rubbed so that they are charged to different polarities, respectively.The cascade method uses glass beads for the carrier, and the magnetic brush uses iron powder for the carrier. There are laws etc. In any case, the toner in the developer is continuously consumed in image formation while maintaining the charged state in the developing process, so when the toner content is less than the optimum content, the image density decreases and becomes faint. not only,
Carriers may adhere to the surface of the photoconductor or the paper and cause various defects. Further, if the toner is excessively contained, the image density increases due to an increase in the toner adhesion amount, but it may cause "roughness", "fog" in the non-image area, "cleaning failure", etc. Electrostatic repulsion between excess toner particles is likely to cause scattering and contamination inside the device. Therefore, it is necessary to replenish the toner during development so that the content in the developer is always maintained within a certain range.

In order to eliminate the problems of these two-component developers, conventionally, developing methods using various one-component developers have been proposed and put into practical use. Among them, there are many excellent methods of using a magnetic toner as a developer, but in particular, a thin layer of an insulating magnetic toner is coated on a developing sleeve and triboelectrically charged,
Then, a method of developing the toner by causing the toner to fly by facing the electrostatic latent image in close proximity to the electrostatic latent image under the action of a magnetic field has been put into practical use as a method of obtaining an excellent image.

However, the method using the one-component magnetic toner has a drawback that the toner particles coated on the sleeve have a remarkably small amount of tribo charge compared to the toner particles in the two-component developer. ing. That is, the charging of the toner in the two-component developer has many contact opportunities such as frictional mixing with the carrier particles and frictional contact with the developing sleeve and friction with the side wall of the developing device. Therefore, it can have a considerably high charge amount. On the other hand, the main factor of triboelectrification in the one-component magnetic toner is only the contact between the toner and the developing sleeve and the contact between the toners. Therefore, the charge amount of the one-component magnetic toner is equal to that of the toner in the two-component developer. It becomes small compared to. When a magnetic toner holding only such a weak charge amount is used, an image defect is likely to occur.

Further, the magnetic toner on the developing sleeve is based on the magnetic force between the toner and the magnet arranged in the sleeve,
Retained on the sleeve. Therefore, since the magnetic toner near the surface of the developing sleeve can directly rub against the sleeve, it can have a relatively high charge amount.
As the contact with the sleeve decreases, and also the magnetic toner in the upper layer, which is separated from the developing sleeve and is charged only by friction between the toners, can obtain a weaker charge.
When a magnetic toner having a variation in charge amount is used as described above, image deterioration such as background fog and density unevenness is likely to occur. (Here, "ground fog" means a bright portion potential ( _VL ) of a portion of the latent image bearing member exposed to light in the developing process.
In addition, it is a development in which toner adheres excessively and fogging occurs. In order to eliminate the drawbacks in the developing method using such a one-component magnetic toner, it has been attempted to use an additive having a polarity opposite to that of the toner for the purpose of improving the chargeability of the magnetic toner, but the durability is improved. Therefore, there is a problem that additives of opposite polarities are accumulated and image deterioration such as reversal fog occurs. (Here, "inverted fog" means, for the purpose of multiple copy, multicolor copy, etc., to erase an image in a specific area, so that a stronger light is applied to the latent image holder with an LED, fuse lamp, etc., When a potential (V _SL ) lower than V ₂ is applied, excess toner adheres to this portion to cause fog.) Furthermore, when such an additive is used, the additive itself adversely affects fog. The additives were limited to colorless fine powders so as not to give.

[Object of the Invention] An object of the present invention is to solve the above-mentioned problems in an electrophotographic method using a one-component magnetic toner as a developer.

That is, a main object of the present invention is to provide an electrophotographic method which is free from background fog and reversal fog and has excellent developing characteristics.

Another object of the present invention is to provide an electrophotographic method capable of obtaining an excellent image with high density from the initial stage.

It is another object of the present invention to provide an electrophotographic method which does not cause reversal fog due to durability, sleeve contamination, image quality deterioration and the like.

[Structure of Invention]

The present inventor has conducted the earnest research to achieve the above-mentioned objects by overcoming the above-mentioned problems in the electrophotographic method using the conventional one-component magnetic toner, and as a result, obtained the following findings, The present invention has been completed based on the findings.

That is, the present invention provides at least a positively chargeable magnetic toner and a non-magnetic lubricant particle having a negatively chargeable volume average particle diameter of 1 to 25 μm as an additive of 0.01 to 5% by weight based on the magnetic toner. An electrophotographic method in which a one-component magnetic toner having the above is used, and the one-component magnetic toner is carried by a developing sleeve having a magnet inside and developed while applying a developing bias. Before forming
In order to positively transfer the negatively charged particle groups to the latent image carrier, the absolute value of the difference between the direct current component of the developing bias applied to the developing sleeve and the potential of the latent image carrier is determined at the time of toner image formation. The developing bias applied is made higher than the absolute value of the difference between the direct current component and the potential of the non-toner image area of the latent image carrier, and the transferred negatively charged particle groups are removed from the latent image carrier. The present invention relates to an electrophotographic method characterized by

The findings obtained as a result of the inventors' earnest research have been summarized as follows.

When a positively charged magnetic toner to which negatively charged lubricant particles are added is used as the developer, when the magnetic toner is placed on the developing sleeve, friction between the magnetic toner and the developing sleeve and magnetic In addition to friction between the toners, friction between the magnetic toner and the negatively charged lubricant particles is an important factor, and the charge amount of the magnetic toner can be sufficient, and the charge amount of the magnetic toner is insufficient. Also, it is possible to prevent the occurrence of fog on the ground due to the variation in the charge amount. Further, it is generally known that when a large amount of fine magnetic toner is present, ground fog is increased.
Since the finely charged positively charged magnetic toner that causes the background fog has a large charge amount, the particles are selectively attached by the Coulomb force to prevent the background fog and improve the image quality.

However, if a reverse polarity particle group is present in the developer used during image formation, it will adhere to the bright portion of the latent image and cause fog on the ground. Further, a potential (V _SL ) lower than the light portion potential (V _L ) is applied to erase an image in a specific area for the purpose of multiple copy, multicolor copy, etc., but when the developing bias is V _DC , | The degree of reversal fog caused by the magnitude of V _DC -V _SL | varies.
Then, the higher the ratio of the reverse polarity particle group present alone is, the more likely the reverse fog is to occur from the time when the value of | V _DC -V _SL | is smaller. However, when the negatively charged particle group is not used to form an image, that is, before the toner image is formed, the potential of the latent image carrier and the DC component of the developing bias applied to the developing sleeve are changed. Thus, the absolute value of the difference between the DC component of the developing bias and the potential of the latent image carrier is calculated as the absolute value of the difference between the DC component of the developing bias applied during toner image formation and the potential of the non-toner image area on the latent image carrier. When compared with the value, the latent image carrier is positively transferred, and the transferred negatively charged particle groups are removed from the latent image carrier by cleaning. The negative charge particles are removed from the sleeve so that the negative charge particles do not adhere to the image area.

As the negatively-charged lubricating particles added to the positively chargeable magnetic toner used in the electrophotographic method of the present invention, any negatively-charged lubricating fine particles can be used. For example, polyvinylidene fluoride. , Polytetrafluoroethylene, polyvinylidene chloride, polychlorotrifluoroethylene and copolymers thereof, or a mixture thereof can be used. Further, in the electrophotographic method of the present invention, since the opposite polarity particle group is positively adhered to the latent image carrier when the image is not formed, it is difficult for such opposite polarity particles to adhere to the image area. I'm running. Therefore, the negatively chargeable lubricant used in the present invention is not limited to a colorless one, and a colored one can be used. A typical example of such colored lubricant particles is molybdenum sulfide.

When the negatively charged lubricant particles are placed on the developing sleeve, they are charged to the same polarity as the electrostatic latent image, and therefore, they are subjected to the force due to the Coulomb force and also have the opposite polarity to the positively charged toner. Therefore, it has an attractive force due to Coulomb force. Therefore, the charge amount, particle size, surface properties, etc. of the low molecular weight polyolefin have a great influence.

However, the negatively chargeable lubricant particles used in the present invention have a polarity opposite to that of the positively chargeable magnetic toner in the charge amount measurement by the two-component mesh method, and
Those that are well dispersed in the magnetic toner are desirable. That is, the charge amount (q / M) by the two-component mesh method is | q / M | ≦
50, and preferably −1 ≧ q / M ≧ −30. In the case of q / M <−50, the negatively chargeable lubricant particles themselves are charged, and the adverse effects such as sticking to the developing sleeve are likely to occur. The charge amount is measured by the two-component mesh method in the present invention as follows. That is, the test substance is thoroughly mixed with the iron powder carrier having a particle size of 200/300 at a ratio of 1:10. 0.5-1.5 g of the mixture was precisely weighed and 25c on a 400 mesh metal screen connected to an electrometer.
Aspirate with mH ₂ O pressure. At this time, the amount of charge per unit weight is determined from the amount of the test substance separated and sucked and the amount of charge indicated by the electrometer.

Also, the volume average particle size of the negatively charged lubricant particles used in the present invention is usually 1 to 25 μm, preferably 2 to 15 μm. When ▲ ▼ exceeds 25, the surface area becomes large, so that a large amount of positively chargeable magnetic toner adheres, resulting in increased background fog. On the other hand, when ▲ ▼ is less than 1, not only does the flowability deteriorate, but it becomes difficult to use a commercial product as it is. The volume average particle size ▲ ▼ in the present invention is the Coulter counter TA.
It was measured with a type II (aperture diameter 100 μ).

In the electrophotographic method of the present invention, the amount of negatively charged lubricant particles added is preferably 0.01 to 5% by weight, and more preferably 0.03 to 3% by weight, based on the positively chargeable magnetic toner. If the amount added exceeds 5% by weight, the amount of the toner particles adhered to the latent image carrier before forming a toner image becomes too large at the initial stage or at the time of replenishing the developer, and further, the negatively charged lubricant particles are not formed. A large amount is transferred onto the transfer paper together with the magnetic toner, resulting in deterioration of fixability during fixing.
Further, if the addition amount is less than 0.01% by weight, it becomes difficult to disperse the magnetic toner in a uniform manner, and as a result, the chargeability to the magnetic toner cannot be said to be sufficient, and the occurrence of fog or the image density is prevented. Is not efficiently achieved. Further, since the lubrication effect is not sufficiently exerted, adverse effects such as filming of the latent image carrier easily occur.

The positively chargeable magnetic toner used in the present invention comprises a binder resin containing a magnetic material.

As the binder resin for the magnetic toner used in the present invention, polystyrene, poly (p-chlorostyrene), styrene such as polyvinyltoluene, or a homopolymer of a substitution product thereof: styrene-
p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer,
Styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer,
Styrene-butyl methacrylate copolymer, styrene-acryl-amino acrylic copolymer, styrene-amino acrylic copolymer, styrene-α-methyl chloromethacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl Methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-malein Styrene-based copolymers such as acid copolymers and styrene-maleic acid ester copolymers: polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester,
Polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin,
Paraffin wax can be used alone or as a mixture.

As the magnetic substance contained in the binder resin, ferromagnetic elements and alloys containing these, alloys such as magnetite, hematite, and ferrite, iron, cobalt, nickel, alloys such as manganese, compounds and other ferromagnetic alloys Can be used as appropriate.

Its particle size is 100 to 800 mμ, preferably 300 to 500 mμ, and 30 to 70 wt% with respect to the polymer particles, preferably 40 to
It is suitable to contain 65% by weight, more preferably 50 to 60% by weight.

In addition, the magnetic toner contains an impulse control agent, a flow modifier,
Even if a colorant, a lubricant and the like are added and contained as necessary, the present invention is not impeded.

The particle size of the above binder resin containing a magnetic substance to form particles is preferably 5 to 20 μm, which is a general toner particle size.

In the production of the positively chargeable magnetic toner used in the present invention, a method obtained by mechanically pulverizing and classifying the constituent materials well after kneading the constituent materials with a heat kneader such as a heat roll, a kneader, and an extruder. Alternatively, a method obtained by dispersing a material such as magnetic powder in a binder resin solution and then spray-drying it,
Alternatively, respective methods such as a polymerization method and a toner production method in which a predetermined material is mixed with a monomer that constitutes a binder resin and then the emulsion suspension is polymerized to obtain a magnetic toner can be applied.

The electrophotographic method of the present invention is particularly effective when a magnetic toner obtained by suspension polymerization or a microcapsule toner made of a core substance and a wall substance is used. That is, in the magnetic toner or the microcapsule toner obtained by the suspension polymerization method, the ratio of the magnetic powder on the fine powder side is inevitably reduced due to the problem of the dispersibility of the magnetic powder. Therefore, the influence of fine powder causes charging and adversely affects the ground fog. If it is a manufacturing process including heat kneading, crushing and classification, it is possible to cut fine powder that causes image quality deterioration by the classification process and reuse the cut classification fine powder. It is very difficult to reuse the obtained magnetic toner or microcapsule toner.

However, according to the electrophotographic method of the present invention, even when the toner or the microcapsule toner obtained by the suspension polymerization method which easily has such fine powder is used, the generation of the background fog by the fine powder toner is efficiently performed. It can be prevented.

The developer used in the present invention is one in which negatively charged lubricant particles are added to and mixed with the above-mentioned positively charged magnetic toner. As a method of adding and mixing, a known mixer, for example, a V-type mixer is used. A rotary container type mixer such as a turbula mixer, a ribbon type, a screw type, a rotary blade type or any other fixed container type mixer can be appropriately used.

In the electrophotographic method of the present invention, reverse polarity particles adhering to the latent image carrier or a method of cleaning the transfer residual developer from the latent image carrier is performed by blade cleaning, far brush cleaning, magnetic brush cleaning method, etc. Although it can be used, the blade cleaning method is particularly preferable because it positively transfers the negative polarity lubricant particles to the latent image carrier, and when the toner image is not formed, the latent image is evenly attached to the surface of the photoreceptor. Filming of the carrier is prevented.

Hereinafter, typical examples of the electrophotographic method of the present invention will be described in more detail with reference to the drawings, but the present invention is not limited thereto.

FIG. 1 is a sectional view schematically showing a copying machine to which an example of the electrophotographic method of the present invention is applied.

In the figure, reference numeral 1 denotes a photosensitive drum (hereinafter, simply referred to as "drum") which is a latent image carrier, and is charged uniformly by a corona discharger 2 via a voltage applying means 10 and then a lens. The optical information that has passed through the array 3 is applied to the surface of the drum 1 to form an electrostatic latent image.

Reference numeral 4 denotes a developing container, which has a developer 5 and a developing sleeve 6 (hereinafter, simply referred to as “sleeve”) carrying the developer 5 therein. The sleeve 6 is about 30 with the drum 1.
The drums 1 are arranged in the developing unit 8 at a narrow interval of 0 μm.
The magnet roller 4 having a developing magnetic pole is arranged inside the sleeve 6 while rotating in the same direction.
A magnetic blade 7 is arranged above the sleeve 6, and the developer 5 is regulated by the magnetic blade 7 and is carried on the sleeve 6 as a toner layer having a thickness of about 70 μm. In the developing section 8, a voltage is applied via the voltage applying means 9 between the drum 1 and the sleeve 6, and the magnetic toner carried on the sleeve 6 adheres to the latent image on the drum 1,
It is developed. The voltage application means 9 and the voltage application means 10 to the corona discharger 2 are controlled by the control means 11 which takes timing with a clock pulse.

Reference numeral 13 denotes a recording paper, which is sent by the registration roller 12 at the same timing as the rotation of the drum 1, and the developed image is transferred onto the recording paper 13 by the transfer charger 14. The transferred image is then fixed by a fixing member (not shown).

After the transfer, the magnetic toner remaining on the drum 1 is removed by the cleaning member 15.

The above is the outline of the copying apparatus to which the electrophotographic method of the present invention can be applied. Next, the developing step in the electrophotographic method of the present invention will be described in more detail.

In the developing section 8 of the embodiment apparatus shown in FIG. 1, a frequency of 1800 Hz and a peak value voltage of 1400 are provided between the drum 1 and the sleeve.
Alternating voltage of V and DC voltage of developing bias are applied. That is, at the time of image formation, a latent image having a dark portion voltage of about −700 V and a light portion voltage of about −200 V is formed on the surface of the latent image carrier, and the latent image is developed by the alternating voltage and the DC voltage applied on the sleeve. It

During this image formation, the DC voltage is about -200V in the bright area of the latent image.
A reverse polarity potential difference of 50 V to 100 V occurs at −250 V
~ -300V is applied. If the magnetic toner has sufficient tribo, the magnetic toner does not adhere and the background fog does not occur due to the potential difference of the polarity opposite to that of the latent image bright portion, that is, the same polarity as the magnetic toner.

However, if a reverse polarity particle group is present in the developer used for development, it adheres to the latent image bright portion and causes background fog.

That is, it is necessary to remove the reverse polarity particle group by the means described below.

FIG. 3 shows the relationship between the DC potential difference between the drum 1 and the sleeve 6 and the image density of the developer adhering to the drum 1 when the alternating voltage is applied. 0V in the center of the graph shown in Fig. 3
Indicates that the drum 1 and the sleeve 6 have the same voltage,
To the right of 0V, the ease of developing a latent image, to the left of 0V,
It is shown that the reverse toner is easily attached to the bright portion of the image.

As is apparent from FIG. 3, the reverse toner adhering to the drum 1 starts to increase at about 350 V or higher.

That is, in the embodiment of the present invention, when the image is not formed, that is, before the toner image is formed, the direct current component is 350 V
By applying the above developing bias, the negatively charged particle group can be positively attached to the latent image carrier.

Next, the developing method of the present invention will be described more specifically.

FIG. 2 shows an example of the developing bias DC voltage applied to the sleeve and the application timing.

Before the toner image is formed, a developing bias having a frequency of 1800 Hz, a peak value voltage of 1400 V, and a DC component of −400 V is applied. The control for switching the DC voltage between the image area and the non-image area is performed by the control means 11. The surface of the drum 1 has the latent image erased, and the entire surface is at about 0V. There is a DC potential difference of about + 400V on the drum surface with reference to the sleeve 6, and as can be seen from Fig. 3, + 400V (> + 35V)
At 0 V), it is easy for the sleeve 6 to adhere to the drum 1. Therefore, the reverse polarity particle group adheres to the drum 1 and is removed from the sleeve 6.

Here, the reverse polarity particle group attached to the drum is removed by the cleaning member 15. At this time, when not forming an image,
That is, since the toner image has not yet been formed, the transfer charging device 14 is controlled to be turned off by the control means 11 so that the reverse polarity fine particle group is guided to the cleaning member 15 while being attached to the surface of the drum 1.

According to this method, when the image is not formed, that is, before the toner image is formed, the reverse polarity particle group is positively removed from the sleeve 6, so that the reverse polarity particles attributed to the negatively charged lubricant particles can be obtained. It is possible to remove the particles as well as to remove the fine particle toner firmly adhered to the opposite polarity particles while performing a normal copying operation, and since the latent image is erased, the opposite polarity particles are uniformly attached to the drum. It is also advantageous in terms of cleaning such as filming prevention.

〔Example〕

Hereinafter, the electrophotographic method of the present invention will be described more specifically with reference to Examples 1 to 4 and Comparative Examples 1 to 4, but the present invention is not limited thereto.

Example 1 The above mixture was kneaded at 150 ° C. by a roll mill, cooled, and coarsely pulverized by a speed mill. After that, finely pulverize with a jet mill and classify powder of 5 to 20μ with an air classifier,
Positively charged magnetic toner was used. The charge amount of the toner is 16.3μ
It was c / g.

0.5% by weight of polyvinylidene fluoride fine particles (volume average particle size 13 μ, charge amount −11.3 μc / g) and 0.5% by weight of colloidal silica were mixed with the above positively charged magnetic toner to prepare a developer.

When an image was formed by using the developer and a combination of the above-mentioned developing method and cleaning by the blade cleaning method, some background fog was observed from the initial stage to 20 sheets, but after that, the development was performed. No ground fog or reversal fog was observed up to 50,000 sheets, including when replenishing the agent. In addition, from the initial stage to 50,000 sheets, including the replenishment of the developer, the image density was as good as 1.3 to 1.4. On the way, when the latent image bearing member was observed with an optical microscope in a state where an image was not formed, it was recognized as polyvinylidene fluoride particles, and 2 to 5 black fine particles were attached with the particles as nuclei. Were found at a random rate.

Comparative Example 1 An image was formed in the same manner as in Example 1 except that only the positively chargeable magnetic toner used in Example 1 was used as a developer, and the reversal fog was good, but about 5,000 sheets. Ground fogging was noticeable. When a bright portion (non-image portion) on the latent image carrier was observed with an optical microscope while an image was being formed on the way, many black fine particles were observed. Furthermore, when images were printed up to 7,000 sheets, filming occurred on the latent image carrier.

Comparative Example 2 Images were printed in the same manner as in Example 1 except that polyvinylidene fluoride fine particles (▲ ▼ = 27 μ, charge amount −7.3 μc / g) were used, and fog was remarkable from the initial stage to about 200 sheets. It was. When the bright part (non-image part) of the latent image bearing member was observed while an image was being formed on the way, several black particles were attached around the white particles, which are considered to be polyvinylidene fluoride fine particles, to form fog. Was found to exist.

Comparative Example 3 Commercially available polyvinylidene fluoride fine particles (▲ ▼ 13μ, charge amount-11.3 μc / g) were finely pulverized and then cut, and ▲ ▼ =
Fine particles with a charge amount of 0.9 μm and a charge amount of −56.3 μc / g were obtained. The measurement of ▲ ▼ at this time was performed with an electron microscope.

When image formation was performed using the above fine particles in the same manner as in Example 1, the image density started to decrease from about 200 sheets. Furthermore, when images were printed up to 500 sheets, unevenness in light and shade occurred in the image, and it was not practically usable.

Comparative Example 4 When image formation was performed in the same manner as in Example 1 except that 11% by weight of polyvinylidene fluoride fine particles were used in Example 1, reversal fog and ground fog were remarkable at the initial stage and during developer replenishment. About 100 photos haven't disappeared. Further, the amount of developer used also increased by 15% as compared with Example 1.

Example 2 An image was produced in the same manner as in Example 1 except that flowing camolybdenum fine particles (▲ ▼ = 2.3 μ, charge amount −1.3 μc / g) were used instead of polyvinylidene fluoride. Similar to Example 1, good results were obtained.

Example 3 The above mixture was uniformly mixed for about 10 minutes in a container such as TK Homomixer (manufactured by Tokushu Kogyo Co., Ltd.) equipped with a high shear mixing device. During that time, the temperature rose to about 55 ° C. During this time, the magnetic powder was uniformly dispersed in the styrene monomer. Separately, 2000 g of water and polyvinyl alcohol as a dispersion stabilizer were put into a TK homomixer, and the above slurry was put into a system kept at 70 ° C. under stirring with a TK homomixer.
Stirred at rpm for 30 minutes. After that, the reaction mixture system was stirred by paddle blade stirring to complete the polymerization. After washing with water and overdrying, a toner having a volume average diameter of 11.0 μ, a number distribution of 6.35 μ or less 21%, and a volume distribution of 20.2 μ or more 5% was obtained. The charge amount of this toner was +11.6 μc / g.

Polyvinylidene fluoride fine particles (volume average particle diameter 13 μ, charge amount −11.3 μ) 0.7 per 100 parts by weight of the above magnetic toner
%, And colloidal silica 0.5% were mixed to form a developer, and images were formed in the same manner as in Example 1. As a result, good results were obtained as in Example 1.

Example 4 The above mixture was kneaded at 150 ° C. for about 30 minutes with a roll mill, and 30 parts by weight of the mixture was dispersed with 50 parts by weight of THF in a ball mill pot to obtain a THF suspension having a particle size of 5 to 15 μm. This suspension was designated as suspension A. Separately THF100
Suspension B was prepared by ball-milling 20 parts by weight of styrene-diethylaminomethacrylate copolymer.

While stirring 100 parts by weight of Suspension A, 50 parts by weight of Suspension B, and 100 parts by weight of THF in a stirring tank, ion-exchanged water is dropped to precipitate an outer wall around the particles composed of polyethylene and a magnetic substance to form microcapsules. Toner (▲
▼ = 10.8μ, number distribution is 6.35μ or less 30%, volume distribution
20.2μ or more 4.3%) was obtained. The charge amount of this toner is 19.8
It was μc / g.

Polyethylene chloride fine particles (volume average particle size 8.5 μ, charge amount −
8.3 μc / g) was mixed with 0.8% and colloidal silica 0.5% to prepare a developer, which was imaged as in Example 1.
Good results were obtained as in Example 1.

[Summary of Effect of Invention]

When image formation is performed by the electrophotographic method of the present invention, a high-density image can be maintained from the beginning, and a high-quality image without reverse fog can be obtained.
It is also possible to prevent the occurrence of ground fog due to durability.

[Brief description of drawings]

FIG. 1 shows a copying apparatus 1 to which the electrophotographic method of the present invention is applied.
FIG. 2 is a cross-sectional view schematically showing an example, FIG. 2 is an explanatory diagram showing the application of a DC voltage to the sleeve and the timing of charging by the corona discharger in the embodiment of the present invention, and FIG. FIG. 3 is an explanatory diagram showing a relationship between a DC potential difference between a drum and a sleeve and toner concentration. About Fig. 1, 1 ... Photosensitive drum, 2 ... Corona discharger, 3 ... Lens array, 4 ... Developer container, 5 ... Developer, 6 ... Developing sleeve, 7 ... Magnetic blade , 8 …… Developing section, 9,
10 ... Voltage applying means, 11 ... Control means, 12 ... Registration roller, 13 ... Recording paper, 14 ... Transfer charger, 15 ... Cleaning member

Claims (7)

[Claims] 1. At least a positively chargeable magnetic toner and 0.01 to 5% by weight of said magnetic toner as a non-charged non-lubricating lubricant particle having a negatively charged volume average particle diameter of 1 to 25 μm as an additive. An electrophotographic method in which a one-component magnetic toner is used, and the one-component magnetic toner is carried by a developing sleeve having a magnet inside and developed while applying a developing bias, and a toner image is formed on a latent image carrier. Before, the absolute value of the difference between the direct current component of the developing bias applied to the developing sleeve and the potential of the latent image carrier in order to positively transfer the negatively charged particle group to the latent image carrier, The development bias applied during toner image formation is made higher than the absolute value of the difference between the direct current component and the potential of the non-toner image area of the latent image carrier, and the transferred negatively charged particle groups are used to carry the latent image carrier. Characterized by removal from the body Electrophotographic method. 2. The electrophotographic method according to claim 1, wherein the volume average particle diameter of the magnetic toner is 5 to 20 μm. 3. The electrophotographic method according to claim 1, wherein the magnetic toner is manufactured by a manufacturing process including heat kneading, pulverization, and classification. 4. The electrophotographic method according to claim 1, wherein the magnetic toner is produced by a suspension polymerization method. 5. The electrophotographic method according to claim 1, wherein the magnetic toner is a microcapsule toner composed of a core substance and a wall substance. 6. The electrophotography according to claim 1, further comprising a step of cleaning the toner remaining on the latent image carrier after development and transfer by a blade cleaning method. Law. 7. The non-magnetic negatively charged lubricant particles include polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene chloride, polychlorotrifluoroethylene, copolymers thereof, mixtures thereof or molybdenum sulfide. An electrophotographic method according to any one of claims (1) to (6).