JPH049864A - Full-color image forming method - Google Patents

Abstract

PURPOSE:To increase an image density and to improve fine line reproducibility and highlight gradation characteristic by developing latent images by a nonmagnetic color toner between a latent image holding body and the surface of a specific magnetic brush in a developing region and using the toner which consists of a toner resin having negative chargeability and does not contain a charge control agent. CONSTITUTION:The magnetic brush 151 is formed in the developing region of a developer carrying member 122 by using magnetic particles which have <=6g/cm<3> true sp.gr. and are coated with an electrical insulating resin in such a manner that the existence quantity of the magnetic particles attains 5 to 100mg/cm<2>. The latent images are developed by the nonmagnetic color toner 128 between the latent image holding body 103 and the surface of the magnetic brush 151 formed on the surface of the developer carrying member 122 in the developing region. The toner which consists of the toner resin having the negative chargeability and does not contain the charge control agent is used as the color toner 128. The bright images which have the high image density and are free from fogging are obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an image forming method used for full color image formation by electrophotography.

[Prior Art] Full-color toner for electrophotography is basically a combination of yellow toner, magenta toner, cyan toner, and black toner if necessary, and is disclosed in Japanese Patent Publication No. 49046951, l'i#l5O- It is described in JP 776, JP 53-47174, JP 53-47175, JP 53-47178, etc.

Conventionally, various methods have been proposed and put into practical use as dry development methods. For example, in a developing method using a two-component developer, the development efficiency is poor, and in order to obtain a predetermined and sufficient development density, it is necessary to apply a predetermined amount of toner onto the developing roller with a uniform concentration. , This has the disadvantage that the developing device configuration becomes larger and more complicated.

A one-component developing method is superior to a two-component developing method in terms of improving development efficiency. Among them, in particular, in Japanese Patent Application Laid-open No. 54-43037, which the present applicant previously filed, 100. Form a thin layer of toner below cam, and apply the toner applied on the sleeve to approximately 1 layer in the image area.
Developing with nearly 00% development efficiency. Therefore, the structure of the developing device could be downsized and simplified for practical use.

This was achieved because a thin layer of 2004+ or less could be formed on the developer roller. However, in any of the development methods, it is extremely difficult to form a thin layer of dry developer, and for this reason, even in one-component development, all but Ganjin Honda configure their developing devices by forming a relatively thick layer. However, in view of the image quality, there is now a demand for improvements in the clarity, resolution, etc. of developed images, and it is essential to develop a method for forming a thin layer of a dry developer and an apparatus therefor.

However, the applicant's method described above involved forming a thin layer of magnetic toner. In order to make magnetic toner magnetic, a magnetic substance must be added to the toner, which causes poor fixing performance when fixing the developed image transferred to transfer paper.
Since a magnetic substance is added to the toner itself (the magnetic substance is usually black), there are problems such as poor color reproduction during color reproduction.

For this reason, methods for forming a thin layer of non-magnetic toner include a method in which toner is applied by using a cylindrical brush made of soft bristles like beaver's hair, and a developing roller whose surface is made of velvet or other fiber. A method of applying with a doctor blade or the like has been proposed.

However, when an elastic blade is used as a doctor blade for the above-mentioned grain brush, it is possible to regulate the amount of toner, but uniform application is not achieved, and only by rubbing the grain brush on the developing roller, the toner existing between the grains of the brush Since no triboelectric charge is imparted to the toner, there is a problem in that fogging and the like are likely to occur.

Further, magnetic toner can easily prevent the toner from scattering by using magnetic force, but non-magnetic toner cannot utilize magnetic force and is likely to cause toner scattering inside the machine.

The above-mentioned disadvantages occur not only during copying but also when vibrations or shocks are applied during transport of the apparatus.

The present applicant uses non-magnetic toner and magnetic particles as a developing device, which is completely different from the conventional method described above, and provides a magnetic particle restraining member opposite to the toner carrying member, so that the magnetic particles A method has already been proposed in which a magnetic brush of magnetic particles is formed by the magnetic force of a magnetic field generating means upstream of a restraining member, the magnetic brush is restrained by the magnetic particle restraining member, and a thin layer of non-magnetic toner is formed on the toner holding member. (Japanese Unexamined Patent Publication No. 143360/1982). With this method, a non-magnetic toner developed image is obtained on the surface of the latent image carrier by setting the gap between the latent image carrier and the toner carrier in the developing section to be wider than the toner layer thickness and applying an alternating electric field. It has been put into practical use.

As a result, it has become possible to obtain color developed images with extremely high development efficiency and a small, simple developing device configuration. In particular, there were no rubbing marks that occur in the dark image area during rubbing development with a two-component magnetic brush, and a solid image of good quality was obtained. However, it has been desired to further improve the developed image quality, for example, to develop a developing method that further improves gradation.

Still another developing method includes a developer container that stores toner and magnetic particles for toner application, and a developer carrier that conveys the toner to a latent image carrier, and uses the magnetic particles to carry the developer. There is a method in which an electrostatic image is developed by forming a magnetic brush in the developing area of the body and setting the gap between the toner carrier and the electrostatic image holder to be larger than the thickness of the magnetic brush layer.

On the other hand, many of the charge control agents conventionally used in toners are colored, and even the colorless charge control agents developed for color toners have insufficient transparency.
I am not completely satisfied with the color toner. Therefore, it was desired to use a binder resin for toner that has charge control properties, and so we examined it.

However, when this toner is used in the non-magnetic toner developed image forming method as described above, the image density decreases due to the toner charge-up phenomenon, and furthermore, the toner that cannot make sufficient contact with the surface of the developer carrier is deposited on the image area. A problem arises in which the so-called fogging phenomenon occurs during development.

On the other hand, charge control using only toner resin causes problems such as a significant decrease in developability due to inability to obtain sufficient charge as a toner.

[Problems to be Solved by the Invention] An object of the present invention is to provide a full-color image forming method that solves the above problems.

That is, the object of the present invention is to achieve high image density (high image density, fine line reproducibility,
The present invention provides a full-color image forming method with excellent highlight gradation.

A further object of the present invention is to provide a full-color image forming method that does not change in performance even after long-term use.

[Means and effects for solving the problem] As a result of intensive studies by the present inventors, the original image is color separated, a latent image is formed for each color on a latent image holding member, and the latent image holding member is In a full-color image forming method in which a latent image is developed with color toner in a development area between a developer carrier and a developer carrier facing the developer carrier, (1) the true specific gravity is 6 g/cm' or less and the developer carrier is coated with an electrically insulating resin; A magnetic brush is formed using magnetic particles such that the amount of the magnetic particles is 5 to 100 mg/cm" in the development area of the developer carrier, and the latent image carrier and the surface of the developer carrier are formed in the development area. This is a developing method in which a latent image is developed with a non-magnetic color toner between the surface of the magnetic brush formed on the surface of the magnetic brush, and (1) the color toner includes a toner resin having negative IT property and containing an f'IK control agent. It has been discovered that a full-color image forming method characterized by using a toner that does not contain toner achieves the above object, leading to the present invention.

Further, the present invention is characterized in that the surface of the developer carrier has a resin layer containing at least fine particles having solid lubricating properties, and the surface of the latent image carrier and the toner layer on the developer carrier are bonded to each other. Full-color image formation characterized by forming a minute gap between the two and applying an alternating electric field to the gap, and further characterized in that the amount of triboelectric charge of the non-magnetic color toner is -0.5 to 60 μcam''. Regarding the method.

The details are described below.

In the present invention, one of the characteristics of the non-magnetic full color toner is that the amount of triboelectric charge exists in the range of -0.5 to 60 .mu.c/ll2 (more preferably -1.theta. to -40 .mu.c/m2). In the present invention, if the amount of triboelectric charge of the toner is less than 10.5 μc/II2, the toner becomes difficult to charge, significantly impairs the developability of the toner, and has adverse effects such as toner scattering, while -60 μc/m2 If it exceeds 100 mL, the toner is strongly supported on the toner carrier, making it difficult to form an image on the electrostatic image carrier.

The amount of triboelectric charge in the present invention is measured by mixing 3% by weight of toner with iron oxide powder (EFV'lQO/300 + manufactured by Nippon Tetsuko Co., Ltd.) as a carrier, and applying this to a 400-mesh conductor network with N2. Spray with gas 1k87cm,
This is the charge amount measured for 1 minute with a blow-off measuring device (TB-200: manufactured by Toshiba Chemical Corporation), and the toner surface area is determined using this and a specific surface area measuring device (Autosorb 1: manufactured by Leakage Ionics Co., Ltd.) that uses the BET method. By this,
Calculated.

As the coloring agent used in the present invention, a wide variety of known dyes and pigments can be used, such as phthalocyanine blue, industhrene blue, peacock blue, permanent red, lake red, rhodamine lake, banza yellow, permanent yellow, benzine yellow, and the like. Its content is 12 parts by weight or less, preferably 0.5 to 9 parts by weight, based on 9,100 parts by weight of the binder so as to sensitively reflect the permeability of the OHP film.

A fluidity imparting agent may be added to the toner according to the present invention in order to stabilize fluidity.

Examples of the fluidity imparting agent include, but are not necessarily limited to, the following. For example, Af20
3. TiO2, GeO2, ZrO2, 5C203, H
Metal oxides such as fO2, carbides such as Eic, TiC, WxC, and 5iJ4. There are nitrides such as GeJ4, among which ^R2O5, TiO2, 5C203, Z
Adding rO2, GeO2, and HfO2 to the toner in an amount of 2% by weight or less is preferable since it does not adversely affect the color when used for color toners since the toner is colorless or white.

If necessary, other additives may be mixed in the toner of the present invention within a range that does not impair the properties of the toner. For example, lubricants such as Teflon, zinc stearate, polyvinylidene fluoride, or low molecular weight polyethylene, Fixing aids such as low molecular weight polypropylene, etc.

As the negatively chargeable toner binding resin used in the present invention, resins composed of one of the following monomers can be used. That is, examples thereof include acids such as acrylic acid, methacrylic acid, and maleic acid, and their esters. In addition, examples of the copolymers that can be combined with the above copolymer include the following.

Styrene (St), α-chlorostyrene, α-methylstyrene, allylbenzene, phenylacetylene, vinylnaphthalene, 4-methylstyrene, 2,4-dimethylstyrene, 3-ethylstyrene, 2,4-diethylstyrene, 2- Methoxystyrene, 4-chlorostyrene, 4-
Aromatic monomers such as fluorostyrene, 3-iodostyrene, 4-cyanostyrene, 3-nitrostyrene, etc., or ethylenically unsaturated monoolefins such as ethylene, propylene, isoprene (IP), butadiene (BD), butylene, isobutylene, etc. Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride; Vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate; Methyl methacrylate (MMA), ethyl methacrylate, methacrylic acid Propyl, methacrylic 1
lIn-butyl (BMA) isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate,
2-ethylhexyl methacrylate (2EHA), stearyl methacrylate, phenyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate (
BA), isobutyl acrylate, propyl acrylate,
Acrylic acid or methacrylic acid esters such as n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate: vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether vinyl ethers such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone; aliphatic vinyl monomers such as acrylonitrile (^N), acrolein, acrylamide, maleic anhydride (MA), timer acid; etc. Preferably used.

It is also possible to copolymerize two or more types of these mercury and use them.

Furthermore, the toner resin used in the present invention is not limited to the above-mentioned resin composed of 1,000 yen, but may also be polyester, polysulfonate, polyether, polyurethane, or the like.

In manufacturing the toner used in the present invention, a hot roll,
After thoroughly kneading the constituent materials using a thermal kneader such as a kneader or extruder, the resulting product is obtained by mechanical crushing and classification, or by dispersing materials such as colorants in a binder resin solution and then spray drying. Alternatively, a method for producing a polymerized toner can be applied, such as a method for producing a toner by mixing a predetermined material with a monomer to constitute a binder resin, and then polymerizing the emulsified suspension.

Another feature of the present invention is that the surface of the developer carrier (developing sleeve) contains at least fine particles having solid lubricating properties. This is due to the structure of the present invention.
It is characterized by using a toner binder resin that has charge control properties without using a negative charge control agent that is conventionally used to impair the transparency of color toners. Charge-up phenomenon or charge controllability becomes a problem.

In order to solve this problem, we thought that the charged up toner near the developing sleeve should be removed by some method. In this method, a resin layer containing fine particles having solid lubricating properties is formed on the sleeve surface, which makes it possible to remove charged-up fine particles and allows smooth replacement of toner in the vicinity of the sleeve.

In addition to fine particles having solid lubricating properties, conductive fine particles, semiconductive metal oxides, etc. may also be contained in the resin layer at the same time for the purpose of leaking the electric charge of the charged-up toner fine powder, and the volume of the resin layer may be There is also a method of reducing the specific resistance to 10'Ω or less, but in this case, it is preferable to set the resistance to 10'cn+ or less, and even in this case, it is necessary to contain it in the resin layer at the same time as fine particles that have solid lubricating properties. be.

The solid lubricants used in the present invention include graphite, fluorinated graphite,
Molybdenum disulfide, tungsten disulfide, boron nitride,
Silicon nitride, calcium fluoride, barium fluoride, -lead oxide, molybdenum trioxide, etc. are used and have crystallinity.
For toner, it is preferable that the triboelectric charge is relatively small. Crystalline graphite is particularly good.

A method for forming a resin layer on the sleeve surface in the present invention will be described.

Common methods for forming a coating include dipping, spraying, roll coating, curtain coating, sputtering, etc., and dipping and spraying are particularly suitable for applying the coating of the present invention.

Specifically, in the spray method, the coating resin as a solid content is dissolved in a solvent, and the contents such as fine particles with solid lubricating properties are mixed with glass beads and dispersed in a paint shaker. It is filtered through a mesh or the like to form a paint, which is applied to the sleeve cylinder using an air spray method to a uniform thickness and then dried at elevated temperatures.

For performance reasons, the thickness of the resin layer should be 0.5 to 3.0μ.
This is preferable from the viewpoint of manufacturing.

Further, the particles having solid lubricating properties used in the present invention preferably have a particle size of 0.5 μmN10 μm.

Examples of film-forming polymeric materials include thermoplastic resins such as styrene resins, vinyl resins, polyethersulfone resins, polycarbonate resins, polyphenylene oxide resins, polyamide resins, fluororesins, cellulose resins, and acrylic resins, and epoxy resins. Thermosetting resins or photocurable resins such as resins, polyester resins, alkyd resins, phenol resins, melamine resins, polyurethane resins, urea resins, silicone resins, and polyimide resins can be used. Among them, those with mold release properties such as silicone resins and fluororesins, and those with excellent mechanical properties such as polyether sulfone, polycarbonate, polyphenylene oxide, polyamide, phenol, polyester, polyurethane, and styrene resins are better. preferable.

More preferred film-forming polymeric materials include polyamide resins, melamine resins, and aminoacrylic resins that have strong positive chargeability, and copolymers or mixtures of these resins and other resins are also possible.

The developing method according to the present invention will be explained below. FIG. 1 shows an example of a developing device suitable for the present invention. In Figure 1, 1
03 is a latent image holding member (photosensitive drum), 121 is a toner supply container, 122 is a non-magnetic coated sleeve, 123 is a fixed magnet, 124 is a non-magnetic plate, 127 is a magnetic particle,
128 is a non-magnetic toner 129 is a developer collecting container portion, 13
0 is a scattering prevention member, 131 is a magnetic member, 132 is a developing area, and 134 is a bias power source. The sleeve 122 is b
As the magnetic particles 127 rotate in the C direction, the magnetic particles 127 circulate in the C direction. This causes contact and rubbing between the sleeve surface and the magnetic particle layer, and a non-magnetic toner layer is formed on the sleeve surface. Further, while the magnetic particles circulate in the C direction, a part of them is regulated to a predetermined amount by the gap between the nonmagnetic blade 124 and the sleeve 122, and is applied onto the nonmagnetic toner layer. That is, the non-magnetic toner is applied to both the sleeve surface and the magnetic particle surface, and the same effect as substantially increasing the sleeve surface area is exhibited. In the present invention, the amount of magnetic particles applied to the surface layer of the sleeve on the downstream side of the non-magnetic blade 124 is 5 mg/1, in order to fully utilize both the magnetic brush made of magnetic particles and the surface of the sleeve 122.
A small amount of about cm2 to 100 g/c+a'' is desirable.

Furthermore, in the development area 132, one of the magnetic poles of the fixed magnet 123 is opposed to the latent image surface to form a clear development pole, and an alternating electric field is used to fly toner from above the sleeve and magnetic particles for development ( This phenomenon will be discussed later). After development, the magnetic particles and undeveloped toner are collected into the developer container as the sleeve rotates.

The sleeve 122 may be a paper tube or a cylinder made of synthetic resin, but if the surface of these cylinders is subjected to conductive treatment or made of a conductive material such as aluminum, brass or stainless steel, it can be used as a developing electrode roller.

The gap d between the tip of the non-magnetic blade 124 and the surface of the developing sleeve 122 is 50 to 500 Im, preferably 100 to 400 μm. If the distance d is smaller than 50 μm, there is a drawback that magnetic particles, which will be described later, become clogged and damage the sleeve. If it is larger than 500 μm, a large amount of non-magnetic toner and magnetic particles (described later) will leak out, making it impossible to form a thin layer.

Reference numeral 7.8 denotes magnetic particles and non-magnetic toner which were sequentially accommodated in the toner supply container 2.

The bottom plate of the toner supply container 2 is extended below the developing sleeve 3, which is a toner holding member, to prevent toner from leaking to the outside. In addition, in order to further ensure the prevention of toner leakage to the outside, a leaked toner collection container part 9 is provided on the top surface of the extended bottom plate to receive and restrain the leaked toner, and a leaked toner collection container part 9 is provided along the length of the tip edge of the extended bottom plate. Shatter prevention material l
O is arranged. A voltage described later is applied to this member IO.

The magnetic particles 7 generally have an average particle size of 30 to 100 microns, preferably 40 to 80 microns. Each magnetic particle may be made of only a magnetic material, a combination of a magnetic material and a non-magnetic material, or a mixture of two or more types of magnetic particles. By first putting the magnetic particles 7 into the toner supply container 2, the magnetic particles 7 are transferred from the sleeve surface area facing the inside of the container 2, that is, the magnetic particles from the toner supply container 2 in which the sleeve 3 is disposed. Alternatively, each part of the sleeve surface area from the magnetic member 11 for preventing leakage of toner to the tip of the non-magnetic blade 5 serving as a magnetic particle restraining member is attracted and held by the magnetic field of the magnet 4 in the sleeve 3 as a magnetic particle layer. The surface area is completely covered. When the non-magnetic toner 28 is put into the container 2 after the magnetic particles 7 have been put in, a large amount of the non-magnetic toner 28 is stored outside the magnetic particle layer as the first layer with respect to the sleeve 3 and exists as a second layer.

It is preferable that the initially charged magnetic particles originally contain about 2 to 70% (by weight) of non-magnetic toner 8 based on the magnetic particles, but only magnetic particles.

You may do so. , If the magnetic particles 7 are adsorbed and held as a magnetic particle layer on the -H sleeve surface area, they will not substantially drift to one side even if the device is vibrated or the device is tilted considerably, and the sleeve surface will remain on the sleeve surface. The entire region is kept covered.

When the magnetic particles 27 and the non-magnetic toner 8 are sequentially charged and stored in the container 2 as described above, the magnetic particle layer near the sleeve surface corresponding to the magnetic pole S2 position of the magnet 4 has a magnetic pole. A magnetic brush of magnetic particles is formed by a strong magnetic field.

In addition, the magnetic particle layer near the tip of the non-magnetic blade 5, which is a magnetic particle regulating member, is regulated based on the effects of gravity, magnetic force, and the presence of the non-magnetic blade 5 even when the sleeve 3 is driven to rotate in the direction indicated by the arrow. Due to the balance between the force and the conveying force of the sleeve 3 in the 8 directions, it accumulates at a point on the surface of the sleeve 3, forming a stationary layer that can move to some extent but is slow to move.

When the sleeve 3 is rotated in the direction shown by the arrow, by appropriately selecting the arrangement position of the magnetic pole and the fluidity and magnetic properties of the magnetic particles 7, the magnetic brush circulates in the direction of the arrow C near the magnetic pole S2. form a layer. In the circulation layer, the magnetic particles relatively close to the sleeve 3 rise from the vicinity of the magnetic pole S2 to the stationary layer on the downstream side of the rotation of the sleeve due to the rotation of the sleeve 3. In other words, it receives a force that pushes it upward. The pushed-up magnetic particles are prevented from climbing onto the non-magnetic blade 5 because the upper limit of the circulation area is limited by the magnetic particle circulation area limiting member 5 provided on the upper part of the non-magnetic blade 5. Instead, it falls due to gravity and returns to the vicinity of the magnetic pole S2 again. In this case, magnetic particles that are located far from the sleeve surface and receive a small push-up force may fall before reaching the magnetic particle circulation area limiting member. In other words, in the circulation layer, the magnetic brush of the magnetic particles is circulated as shown by arrow C due to the magnetic force and frictional force due to gravity and magnetic poles, and the fluidity (viscosity) of the magnetic particles. The non-magnetic toner 8 is successively taken in from the upper toner layer and returned to the lower part of the developer supply container 2, and this circulation is repeated as the sleeve 3 is rotated.

As the developing bias voltage 13, an alternating voltage whose positive and negative peak voltages are the same, or a DC voltage superimposed on this alternating voltage can be used. For example, dark area latent image potential -100V
For an electrostatic latent image with a bright area latent image potential of -600V, for example, by superimposing a DC voltage of -300V on the sleeve 3, the peak voltage of the waveform is set to vpp300 to 2000, and the frequency is 200V.
~3000) An alternating voltage selected in the range of 12 is applied to maintain the photoreceptor drum l at ground potential.

Generally, the electrical resistance of magnetic brushes is relatively high (10aΩ
(greater than C1), the peak voltage of the developing bias vpp
The higher the frequency is, the better (for example, 800 V or higher), and the higher the frequency is 600 Hz or higher, preferably 800 Hz or higher, and more preferably 1 kHz or higher, the higher the image quality with sufficient density can be obtained. Even if only vpp is high, if the frequency is low, the density will be low and it will be difficult to obtain good image quality. In any case, the upper limit of vpp is determined by the gap discharge limit value of the developing section, and the limit is determined by the toner flight limit value on the sleeve and on the magnetic particles.

In the comparatively resistive developing brushes, the peak value of the alternating electric field is set so that the gap voltage does not reach the discharge starting voltage by appropriately selecting the frequency of the applied alternating electric field and the time constant of the developing brush itself. is preferred.

Note that the resistance value of the magnetic particles/magnetic brush mentioned in the present invention refers to the resistance value of a magnetic brush made of a large amount of magnetic particles formed on the developing sleeve 22, and facing the developing sleeve and a gap 5.
A metal drum with a diameter of about IM is installed in series with
It is calculated from the current value that flows when a DC voltage of 200 V is applied to a circuit connected to a resistor of Ω.

In the developing method according to the present invention, phenomena in the developing section 132 will be described below.

FIGS. 2 and 3 are enlarged explanatory views of the developing section of the developing method according to the present invention. 150 is a latent image charge in a dark area on the latent image carrier. 128 is a non-magnetic toner. 134 is an alternating voltage power source on which a DC component is superimposed. FIG. 2 shows a case in which a positive waveform component of an alternating voltage is applied to the sleeve 122, and FIG. 3 shows a case in which a negative waveform component of an alternating voltage is applied. The polarity of the latent image charge is shown as negative, and the polarity of the developer is shown as positive.

The resistance of the developing brush 151 is relatively large (approximately 106Ωc).
m), the developing brush 151 depends on the charging/discharging time constant of the charge due to the material of the developing brush 151 itself and other
is a frictional charge or a mirror charge with the toner 128,
There will be charges injected by the latent image electric field on the latent image carrier 103 and the alternating electric field between the latent image carrier 103 and the sleeve 122.

When the electric field due to the latent image charge 150 in the dark area on the latent image holding member 103 matches the electric field due to the alternating electric field, the developing brush 1
At 51, the sleeve is in the maximum bending state in the direction of the sleeve 122.

When the electric field due to the latent image charge on the latent image holding member 103 and the electric field due to the alternating electric field do not match in direction, the bending of the developing brush 151 becomes small.

In any case, as mentioned above, the developing brush 1 is
51 enters a fine but violent vibration state, and the excess fog toner adhering to the latent image holder is rubbed by the developing brush, removed from the latent image holder 103, and pulled back onto the brush. In addition, due to the above vibration of the brush,
Since the toner is easily separated from the brush 151 and easily supplied to the latent image holding member 103, the image density is also improved.

Furthermore, the vibration of the brush 151 loosens the toner within the brush 151, which contributes to improving image density and preventing ghosts. Further, if this vibration state is severe, a portion of the magnetic brush comes off from the brush or the sleeve, causing reciprocating motion between the latent image holder and the sleeve surface. The kinetic energy of this reciprocating brush is large and efficient, and the behavior of magnetic particles in one or more developing sections, where the above-mentioned vibration effect is expected, is the result of high-speed photography at 8000 frames per second with a high-speed camera. , is an observed phenomenon.

[Examples] Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

It should be noted that unless otherwise specified, the terms in the text or % are based on weight.

After mixing the ingredients, the mixture was melt-kneaded using a twin-screw kneading press, cooled, pulverized using an air flow pulverizer, and classified using an air classifier to obtain a blue powder with a volume average particle diameter of approximately 11.5 μm. Got toner. 0.8 parts of negatively chargeable colloidal silica was externally added to 100 parts of this toner to obtain a cyan toner. The resulting toner rub! The electric charge amount was -25 μC/l112. In addition, the phthalocyanine pigment in the above formulation was replaced with rhodamine pigment, C,1, Pigment Yellow 17. Magenta toner, yellow toner, and black toner were obtained in the same manner except that carbon black was used.

These toners were mixed with ferrite particles (true north f[5, Og/cm') coated with fluorine acrylic resin at a ratio of 1=9 to obtain developers for each color.

Using these developers, images were produced using a commercially available full-color copying machine (Color Laser Copier 500, manufactured by Canon) with a modified developing device.

As a developer carrier (developing sleeve), an aluminum cylinder coated with a polyamide resin in which 45 parts of crystalline graphite was dispersed was used. Furthermore, on the surface of the photoreceptor drum facing the developing sleeve, the gap between the developer carrier and the latent image holder is set to 400μ for a latent image of -100V in the dark area and -600V in the bright area as an electrostatic latent image. Here, an alternating electric field (1.8KVpp, 1.2K
)Iz) and a direct current electric field were applied to perform development.

As a result, a clear image with high image density and no fogging was obtained. As a result of further durability testing of 5000 sheets,
The image density was stable and the image was clear. Furthermore, there was almost no toner scattering inside the copying machine.

Image quality was evaluated in the same manner as in Example 1, except that the coating agent for the developing sleeve in Example 1 was changed to a styrene-dimethylaminoethyl acrylate copolymer in which 40 parts of crystalline graphite was dispersed.

As a result of the durability test of 5,000 sheets, as in Example 1, the image density was stable and a clear image without fogging was obtained.

[Shim] The toner formulation of Example 1 was the same as in Example 1, except that the toner binding resin was changed to polyester resin. Obtained. Example 2 A developer was prepared in the same manner as in Example 1.
The same development evaluation as in Example 1 was carried out using the developing sleeve.

As a result of a durability test of 5,000 sheets, the image density was stable and a clear image without fogging was obtained, similar to the example work.

Comparative Example 1 The same toner as in Example 3 was used, and instead of the developing sleeve in Example 1, an aluminum sleeve sandblasted in an irregular shape using alundum abrasive grains without surface coating was used.
In the same manner as above, the image display durability was carried out.

As a result, the initial image was good in both density and image quality, but the image density began to decrease after running for about 500 sheets.This is an enlarged explanatory diagram of the developing section.

Ta.

Comparative Example 2 Using polyvinyl chloride as the toner resin of Example 1,
A toner of 10.54 u+ and a friction it amount of -65 μc/m2 was obtained. A developer was prepared using this toner in the same manner as in Example 1, and image quality was evaluated.

As a result, the image density became lower than the initial level, and fogging, toner scattering, etc. occurred. Note that the temperature of the fixing device was changed by changing its settings.

[Effect of the invention] By applying a specific non-magnetic color toner not containing an 'f'N control agent and a developer having magnetic particles to a full-color image forming method having a developer carrier having a specific surface layer, , high image density, clear images without fogging, and no change in performance even after long-term use.

[Brief explanation of the drawing]

Claims (1)

[Scope of Claims] 1) Separate the original image into colors, form a latent image for each color on a latent image holder, and generate a latent image in the development area between the latent image holder and a developer carrier facing the latent image holder. In a full-color image forming method in which an image is developed with color toner, [1] magnetic particles having a true specific gravity of 6 g/cm^3 or less and coated with an electrically insulating resin are used to form a developing area of a developer carrier. The amount of magnetic particles present is 5 to 100 mg/
cm^2, and a latent image is developed with non-magnetic color toner between the surface of the magnetic brush formed on the surface of the latent image carrier and the developer carrier in the development area. [2] A full-color image forming method, characterized in that [2] a toner in which the toner resin is negatively chargeable and does not contain a charge control agent is used as the color toner. 2) The full-color image forming method according to claim 1, wherein the surface of the developer carrier has a resin layer containing at least fine particles having solid lubricating properties. 3) According to claim (1) or (2), a minute gap is formed between the latent image holding member and the surface of the toner layer on the developer carrying member, and an alternating electric field is applied to this gap. Full color image forming method as described. 4) The amount of triboelectric charge of the non-magnetic color toner is -0.
Claim characterized in that it is 5 to 60 μc/m^2 (
The full-color image forming method according to any one of 1) to (3).