JPH0436759A - Full-color image forming method - Google Patents

Abstract

PURPOSE:To provide the image forming method with which the image density is high and the fine lien reproducibility and highlight gradation characteristic are excellent by specifying the volume average grain size of a nonmagnetic color toner, specifying the content % of toner particles of prescribed grain sizes and satisfying the specific condition. CONSTITUTION:The volume average grain size of the nonmagnetic color toner is 6.0 to 10.0mum. The toner particles having <=5mum grain size are incorporated at 15 to 40 piece% therein and the toner particles having 12.7 to 16.0mum grain size at 0.1 to 5.0vol.% and the toner particles having >=16.0 mum grain size at <=1.0vol.% therein. The toner particle of 6.35 to 10.1mum are provided with the grain size distribution satisfying equation I (where V: vol.% of the toner particles having 6.35 to 10.1mum grain size, N: the number % of the toner particle having 6.35 to 10.1mum grain size, dv: the volume average grain size of the entire toner particles). The surface of the toner carrier member has the resin layer contg. at least the fine particles having solid lubricity and a microgap is formed between the latent image holding member and the toner layer surface on the toner carrier member. Alternate electric fields are impressed to this gap.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] 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. 49-46951 and Japanese Patent Publication No. 1983-1989. -776 publication,
Special Publication No. 53-47174, Special Publication No. 53-4717
5, Japanese Patent Publication No. 53-47176, etc.

Various methods have been proposed and put into practical use as methods for developing full-color toner. However, for example, in a developing method using two-component toner, 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 color toner uniformly on the developing roller. This has the disadvantage that the structure of the developing device becomes larger and more complicated. There is also a method of using soft bristles like beaver hair into a cylindrical brush and applying the toner to it.
A method has been proposed in which the coating is applied to a developing roller whose surface is made of a material such as velvet using a doctor blade or the like.

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

Further, magnetic toner can easily prevent toner 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 a toner carrying member so that the surface of the toner carrying member moves in the direction of movement. Forming a magnetic brush of magnetic particles by the magnetic force of the magnetic field generating means upstream of the particle restraining member,
A method has already been proposed in which a magnetic brush is restrained by a magnetic particle restraining member and a thin layer of non-magnetic toner is formed on a toner carrying member (Japanese Patent Laid-Open No. 143360/1982). Using this method, the gap between the latent image holding member and the toner carrying member in the development area is set wider than the toner layer thickness, and an alternating electric field is applied to obtain a nonmagnetic toner developed image on the surface of the latent image holding member. The method was put into practical use.

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

Still another developing method includes a toner container that stores toner and magnetic particles for toner application, and a toner carrying member that conveys the toner to a latent image holding member. There is a method of developing an electrostatic image by forming a magnetic brush in the developing area and setting the gap between the toner carrying member and the latent image holding member larger than the thickness of the magnetic brush layer.

However, in this developing method, the ratio of non-magnetic toner to magnetic particles (so-called T/C ratio) is higher than in the conventional method. Therefore, the thin layer of toner formed on the toner carrying member is composed of nonmagnetic toner attached to magnetic particles and nonmagnetic toner attached directly to the toner carrying member.

Further, when the particle size of the toner is reduced, the specific surface area of the toner increases, and the amount of charge per unit mass, van der Waals force, etc. increase. For this reason, the adhesion force between the toner and the surface of the toner carrying member is strong (and causes charge-up. Therefore, for non-magnetic toner attached to magnetic particles, charge-up can be prevented by appropriately selecting magnetic particles. However, sufficient measures have not been taken to prevent non-magnetic toner directly adhering to the toner carrying member, and as a result, full-color toner with small particle size has not been fully utilized.

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

Furthermore, it is an object of the present invention to achieve high image density, fine line reproducibility,
An object of the present invention is to provide an image forming method with excellent highlight gradation.

A further object of the present invention is to provide an image forming method with no change in performance even after long-term use.

[Means and effects for solving the problem] In order to achieve the above-mentioned object, the inventors of the present invention have conducted intensive studies, and as a result, the original image is separated into colors, and a latent image is formed for each color on a latent image holding member. , in a full-color image forming method in which a latent image is developed with color toner in a development area between the latent image holding member and a toner carrying member opposing the latent image holding member, the true specific gravity is 6 g/cm” or less, and the electrically insulating property is Using magnetic particles coated with resin, a magnetic brush is formed in the developing area of the toner carrying member so that the amount of the magnetic particles is 5 to 100 mg 7 cm, and the latent image holding member and the toner carrying member are coated in the developing area. This developing method is characterized in that a latent image is developed with a non-magnetic color toner between the surface of the magnetic brush formed on the surface of the member, and the non-magnetic color toner has a volume average particle diameter of 6. 0 to 1O10 μm, and contains 15 to 40 number % of toner particles having a particle size of 5 μm or less, and 12.7
Toner particles with a particle size of ~16.0 ILm are 0.1~
5.0% by volume, 1.0% by volume or less of toner particles having a particle size of 16.0Q or more, 6.35-1
0. IJLIll toner particles have the following formula V: 6.3
5-10. % by volume of toner particles having a particle size of 1 μm N: % of number of toner particles having a particle size of 6.35 to 1 μm dv: having a particle size distribution that satisfies the volume average particle size of all toner particles; The surface of the toner carrying member has a resin layer containing at least fine particles having solid lubricating properties, and microgaps are formed between the latent image holding member and the surface of the toner layer on the toner carrying member. This is a full-color image forming method characterized by applying an alternating electric field to a gap. Details are given below.

When the particle size distribution of toner was studied for the purpose of improving development characteristics and image quality, it was found that there is a state of particle size distribution most suitable for achieving the purpose as shown by the following formula.

That is, in the present invention, the volume average diameter of the color toner is 6.
．． 0 to IO, o μm, 15 to 40 number % of toner particles having a particle size of 5.0 μm or less, 12.7 to l 6
Toner particles containing 0.1 to 5.0 volume % of μm and 1.0 volume % of 16 μm or more and 6.35 to 10.1 μm satisfy the following formula L dv: average volume diameter of all toner particles This is an important point.

In other words, when the particle size distribution is adjusted by general air classification, the above value is large, which means that the number of toner particles of about 5 μm that faithfully reproduces the minute dot latent image increases, and the above value is small, which means the opposite This is understood to indicate that toner particles of about 5 μm are reduced in size.

Therefore, when dv is in the range of 6.0 to 10.0 μm and the above relational expression is further satisfied, faithful latent image reproducibility is achieved.

In addition, for toner particles with a particle size of 16.0 μm or more,
It is preferably 1.0% by volume or less, and as little as possible. Toner particles with a particle size of 5.0 μm or less account for 15 of the total number of particles.
It is good that it is ~40% by number, more preferably 20~
35% by number is good; if toner particles with a particle size of 5.0 μm or less are less than 15% by number, there are fewer toner particles effective for high image quality, especially as the toner is used by continuing copying or printing. , effective toner particle components decrease, the balance of toner particle size distribution worsens, and image quality gradually deteriorates. If the amount is 40% or more, toner particles tend to aggregate with each other, impairing fluidity.

In addition, particles in the range of 12.7 to 16.0 μm are 0.1 to 5
．． It is good that it is 0 volume % (preferably 0.2 to 3.
0% by volume is good. When the amount is more than 5.0% by volume, image quality deteriorates and more development than necessary occurs, that is, too much toner is applied, leading to an increase in toner consumption.

On the other hand, if it is less than 0.1% by volume, image density will decrease due to a decrease in fluidity.

Further, it is preferable that the amount of toner particles having a particle size of 16.0 μm or more is 1.0% by volume or less, and more preferably 0.6% by volume.
If it is more than 1.0% by volume, it will interfere with fine line reproduction.

Further, the volume average diameter of the toner is 6.0 to 10.0 μm, preferably 7.0 to 9.0 μm, and this value cannot be considered in isolation from the above-mentioned components. If the volume average particle diameter is less than 6.014 m, in applications with a high image area ratio such as graphic images, the amount of toner applied to the transfer paper is small, which tends to cause problems such as low image density. If the volume average particle diameter is 10.0 μm or more, the resolution is not good, and although the quality is good at the beginning of copying, the image quality tends to deteriorate with continued use.

Thermoplastic resins that can be used include polystyrene, polyp-chlorostyrene, polyvinyltoluene, and styrene.
Homopolymers of styrene and its substituted products, such as p-chlorostyrene copolymers and styrene vinyltoluene copolymers, and copolymers thereof; styrene-methyl acrylate copolymers, styrene-ethyl acrylate copolymers, styrene -Copolymers of styrene and acrylic esters such as n-butyl acrylate copolymers; styrene-methyl methacrylate copolymers, styrene-ethyl methacrylate copolymers, styrene-n-butyl methacrylate copolymers Copolymers of styrene and methacrylic esters such as; multicomponent copolymers of styrene and acrylic esters and methacrylic esters, styrene and dimethylaminoethyl methacrylate and acrylic esters, styrene and diethylaminoethyl methacrylate and acrylic esters; Others: styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-butadiene copolymer, styrene-vinyl methyl ketone copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid ester copolymer Styrenic copolymers of styrene and other vinyl monomers such as polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate,
Polyester, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid, phenol resin, aliphatic or alicyclic hydrocarbon resin, petroleum resin, chlorinated paraffin, etc. can be used alone, in mixtures, or in combination. Particularly preferred are styrene-acrylic resins and polyester resins.

A charge control agent may be added to the toner according to the present invention in order to stabilize charge characteristics. In this case, a colorless or light-colored charge control agent that does not affect the color tone of the toner is preferred.

Coloring agents used in the present invention include known dyes and pigments such as phthalocyanine blue, industhrene blue, peacock blue, permanent red, lake red, rhodamine lake, permanent yellow, benzine yellow, etc. I can do it.

The content thereof is 12 parts by weight or less, preferably 0.5 to 9 parts by weight, based on 100 parts by weight of the binder resin so as to sensitively reflect the transparency 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, AI! 2
0a, TiO2, Gem□, Zr0a, SC20m
, metal oxides such as HfO□, SiC, Tic, W
Carbide such as 2C and 5isN4. There are nitrides such as Ge5N<, among which AR20, TiO2, 5C2
03, ZrO2, GeDz, ) IfD2 is preferably added in an amount of 2% by weight or less to the toner since it is colorless or white, and when used for color toners, it does not adversely affect the color.

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

In producing the toner of the present invention, the constituent materials are kneaded using a thermal kneading machine such as a hot roll, kneader, or extruder, and then mechanically crushed or classified, or mixed into a binder resin solution. After dispersing materials such as colorants,
There are various methods such as spray drying, or polymerization toner manufacturing method, which obtains a toner by mixing a specified material with monomers that constitute the binder resin and then polymerizing this emulsified suspension. Can be applied.

In addition, in this developing method, the ratio of non-magnetic toner to magnetic particles (so-called T/C ratio) is higher than in the conventional method. Therefore, the thin layer of toner formed on the toner carrying member is composed of nonmagnetic toner attached to magnetic particles and nonmagnetic toner attached directly to the toner carrying member. Here, when the particle size of the toner is reduced, the specific surface area of the toner increases, so the amount of charge per unit mass, van der Waals force, etc. increases, causing charge-up and contamination of the toner carrying member by fine powder toner. This gives rise to the possibility of

In order to solve this problem, it was thought that the charged-up fine powder toner near the toner carrying member should be removed by some method. In this method, a resin layer containing fine particles having solid lubricating properties is formed on the surface of the toner carrying member, and charged-up fine powder can be removed, so that the toner can be smoothly replaced in the vicinity of the toner carrying member.

In addition to fine particles that have solid lubricating properties, conductive fine particles, semiconductive metal oxides, etc. are also contained in the resin layer for the purpose of leaking the electric charge of the charged up toner fine powder. Although there is a method of reducing the resistance to 10' Ωcm or less, in this case, it is preferable to set the resistance to 10 3 ΩCl11 or less, and even in this case, it is necessary to contain it in the resin layer at the same time as the fine particles having solid lubricating properties.

As the solid lubricant of the present invention, graphite, graphite fluoride, molybdenum disulfide, tungsten disulfide, boron nitride, silicon nitride, calcium fluoride, barium fluoride, -lead oxide, molybdenum trioxide, etc. are used. It is preferable that the toner has a relatively small triboelectric charge on the toner.

Crystalline graphite is particularly good.

A method for forming a resin layer on the surface of a toner carrying member 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 a cylinder of a toner carrying member to a uniform thickness using an air spray method, and then dried at an elevated temperature.

The thickness of the resin layer is preferably 0.5 to 3.0 μm from the viewpoint of performance and manufacturing.

In addition, the particles having solid lubricating properties used in the invention have a particle size of 0.5 μm to 10 μm. Ogm ones are good.

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 these, those with mold release properties such as silicone resins and fluororesins, or those with excellent mechanical properties such as polyether sulfone, polycarbonate, polyphenylene oxide, polyamide, phenol, polyester, polyurethane, and styrene resins are more preferable. .

The present developing method will be explained below. FIG. 1 is an example of the present invention. In FIG. 1, 3 is a latent image holding member, 21
22 is a toner supply container, 22 is a toner carrying member, 23 is a fixed magnet, 24 is a non-magnetic blade, 26 is a magnetic particle circulation area limiting member, 27 is a magnetic particle, 28 is a non-magnetic toner, 29 is a toner collection container part, 30 is a scattering prevention member, 31 is a magnetic member, 32 is a developing area, and 34 is a bias power source. The toner carrying member 22 rotates in the direction b, and the magnetic particles 27 circulate in the direction C accordingly.

This causes contact and rubbing between the toner carrying member 22 surface and the magnetic particle 27 layer, and a non-magnetic toner 28 layer is formed on the toner carrying member 22 surface. Further, while the magnetic particles 27 circulate in the C direction, a part of them is regulated to a predetermined amount by the gap between the non-magnetic blade 24 and the toner carrying member 22.
The non-magnetic toner is coated on top of the 28 layer. That is, the non-magnetic toner 28 is applied to both the surface of the toner carrying member 22 and the surface of the magnetic particles 27, and the same effect as substantially increasing the surface area of the toner carrying member 22 is exhibited.

Non-magnetic blade 24 downstream toner carrying member 2 in the present invention
The coating amount of the magnetic particles 27 on the second surface layer is preferably a small amount of about 5 mg/cm2 to long/cm'' in order to fully utilize the magnetic brush made of the magnetic particles 27 and the surface of the toner carrying member 22. .

In addition, in the developing area 32, one of the magnetic poles of the fixed magnet 23
A clear development pole is formed by arranging one of the two to face the latent image surface, and the toner is developed by flying onto the toner carrying member 22 and from the magnetic particles 27 by an alternating electric field.

(This phenomenon will be explained later.) After development, magnetic particles 2
7 and undeveloped toner are collected into the toner supply container 21 as the toner carrying member 22 rotates.

The gap d between the tip of the non-magnetic blade 24 and the surface of the toner carrying member 22 at the point 25 is 50 to 500.
μm, preferably 100 to 400 μm. If the distance d is smaller than 50 μm, there is a drawback that the magnetic particles 27 (described later) become clogged and damage the toner carrying member 22.

Moreover, if the diameter is larger than 500 μm, non-magnetic toner 2 described later
8 and magnetic particles 27 leak out in large quantities, making it impossible to form a thin layer.

In FIG. 1, 26 is a magnetic particle circulation area limiting member whose lower surface is in contact with the upper surface of the non-magnetic blade 24 and whose front end surface is an undercut surface.

Reference numerals 27 and 28 denote magnetic particles and non-magnetic toner which are sequentially contained in the toner supply container 21.

The bottom plate of the toner supply container 21 is extended below the toner carrying member 22 to prevent toner from leaking to the outside. In addition, in order to further ensure the prevention of toner leakage to the outside, a toner collection container part 29 is provided on the upper surface of the extended bottom plate to receive and restrain the leaked toner, and a toner collection container part 29 is provided along the longitudinal direction of the tip edge of the extended bottom plate. A scattering prevention member 30 is provided. A voltage, which will be described later, is applied to this scattering prevention member 30.

The magnetic particles 27 generally have an average particle size of 30 to 100 μm,
Preferably it is 40 to 80 μm. Each magnetic particle 27 may be made of only a magnetic material, may be a combination of a magnetic material and a non-magnetic material, or may be a mixture of two or more types of magnetic particles 27. By first putting the magnetic particles 27 into the toner supply container 21, the magnetic particles 27 are applied to the surface area of the toner carrying member 22 facing into the toner supplying container 21, that is, the toner on which the toner carrying member 22 is disposed. In each part of the surface area of the toner carrying member 22 from the magnetic member 31 for preventing leakage of the magnetic particles 27 or toner from the supply container 21 to the tip of the non-magnetic blade 24 serving as a magnetic particle restraining member, Fixed magnet 2
3, the particles are attracted and held as magnetic particles 27M, which completely cover the surface area of the toner carrying member 22.

After the magnetic particles 27 have been introduced, the non-magnetic toner 28 is introduced into the toner supply container 21, so that a large amount of the non-magnetic toner 28 is stored outside the layer of magnetic particles 27 as the first layer for the toner carrying member 22, and is transferred to the second layer. Exist as layers.

The first magnetic particles 27 preferably contain non-magnetic toner 28 in an amount of about 2 to 70% (by weight) of the magnetic particles, but may be composed of only magnetic particles. Furthermore, once the magnetic particles 27 are adsorbed and held as a layer of magnetic particles 27 on the surface area of the toner carrying member 22, they will not substantially shift to one side even if the device is vibrated or the device is tilted considerably. The state in which the surface area of the toner carrying member 22 is completely covered is maintained.

Thus, the magnetic particles 2 are placed in the toner supply container 21 as described above.
7 and non-magnetic toner 28 are sequentially charged and accommodated, the magnetic particles 27 are deposited in the magnetic particle 27 layer portion near the surface of the toner carrying member 22 corresponding to the magnetic pole S2 position of the fixed magnet 23 due to the strong magnetic field of the magnetic pole. A magnetic brush is formed.

In addition, even when the toner carrying member 22 is rotated in the direction indicated by the arrow, the magnetic particle layer near the tip of the non-magnetic blade 24 exerts a regulating force based on the effects of gravity, magnetic force, and the presence of the non-magnetic blade 24. Due to the balance between this and the conveyance force in the moving direction of the toner carrying member 22, the toner particles accumulate at the point 25 on the surface of the toner carrying member 22, forming a stationary layer that can move to some extent but is slow to move.

When the toner carrying member 22 is rotated in the direction indicated by the arrow, the magnetic brush circulates in the direction of the arrow C near the magnetic pole S2 by appropriately selecting the arrangement position of the magnetic pole and the fluidity and magnetic properties of the magnetic particles 27. , forming a circulating layer. In the circulating layer, the magnetic particles relatively close to the toner carrying member 22 rise from the vicinity of the magnetic pole S2 onto the stationary layer on the rotational downstream side of the toner carrying member 22 due to the rotation of the toner carrying member 22. In other words, it receives a force that pushes it upward. The pushed-up magnetic particles do not climb onto the non-magnetic blade 24 because the upper limit of the circulation area is determined by the magnetic particle circulation area limiting member 26 provided at the top of the non-magnetic blade 24. , falls due to gravity,
Magnetic pole S again! Return to nearby area. In this case, the toner carrying member 22
Magnetic particles that are located far from the surface and receive a small push-up force may fall before reaching the magnetic particle circulation area limiting member 26. In other words, in the circulation layer, the magnetic force and frictional force due to gravity and magnetic poles, and the fluidity (viscosity) of the magnetic particles 27 cause the magnetic brushes of the magnetic particles 27 to circulate as shown by arrow C, and during this circulation, the magnetic brushes The non-magnetic toner 28 is sequentially taken in from the toner layer above the magnetic particle layer and returned to the lower part of the toner supply container 21, and this circulation is repeated as the toner carrying member 22 is rotated.

The developing bias voltage applied from the alternating voltage power supply 34 is
An alternating voltage with the same peak voltage on the positive and negative sides, or a DC voltage superimposed on this alternating voltage can be used. For example, dark area latent image potential -600V, bright area latent image potential -20V
For an electrostatic latent image of 0■, for example, by superimposing a DC voltage of -300 V on the toner carrying member 22, the peak voltage of the waveform Vpp is 300 to 2000 V, and the frequency is 200 to 3000.
An alternating voltage selected in the Hz range is applied to maintain the latent image holding member 3 at ground potential.

Generally, the electrical resistance of magnetic brushes is relatively high (10sΩ
cm), the peak voltage of the developing bias voltage v
The higher the pp is, the better (for example, 800 square meters or higher), and the higher the frequency is 600 Hz or higher, preferably 800 Hz or higher, 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, V
l) The upper limit of I) is determined by the gap discharge limit value of the developing area 32, and the lower limit is determined by the toner flight limit value on the toner carrying member 22 and the magnetic particles 27.

In the magnetic brush having relatively high resistance, 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 magnetic brush itself. is preferred.

Incidentally, magnetic particles 27. described in the present invention. The resistance value of the magnetic brush refers to the resistance value of a large amount of magnetic particles 27 on the toner carrying member 22.
A magnetic brush is formed, a metal drum is provided facing the toner carrying member 22 with a gap of 5 mm, and a DC 200 V is connected to a circuit in which a resistor of approximately IMΩ is connected in series with the magnetic brush.
This is calculated from the current value that flows when a voltage of .

Hereinafter, phenomena in the development area 32 will be described regarding the development method according to the present invention.

FIGS. 2 and 3 are enlarged explanatory views of the developing area 32 in the developing method according to the present invention. 50 is a latent image charge in a dark area on the latent image holding member 3. 28 is a non-magnetic toner.

34 is an alternating voltage power source on which a DC component is superimposed. 32nd
The figure shows a case where a positive waveform component of an alternating voltage is applied to the toner carrying member 22, and FIG. 3 shows a case where a negative waveform component of an alternating voltage is applied. The polarity of the latent image charge 5o is shown as negative, and the polarity of the toner is shown as positive.

Moreover, when the polarity of the latent image charge 50 is positive and the polarity of the toner is negative, FIG. 2 shows that the negative waveform component of the alternating voltage is
FIG. 3 shows the case where a positive waveform component of the alternating voltage is added.

The resistance of the magnetic brush 51 is relatively large, approximately io'Ωcm.
Therefore, depending on the charging/discharging time constant of the charge due to the material of the magnetic brush 51 itself and other factors, the magnetic brush 51 has a frictional charge or a mirror charge with the non-magnetic toner 28, and a charge on the latent image holding member 3. There is an electric field injected by the latent image electric field and the alternating electric field between the latent image holding member 3 and the toner particle carrying member 22.

When the electric field due to the latent image charge 5o in the dark area on the latent image holding member 3 matches the electric field due to the alternating electric field, the magnetic brush 51 is brought into a maximum bending state in the direction of the toner carrying member 22.

When the electric field due to the latent image charge 50 on the latent image holding member 3 and the electric field due to the alternating electric field do not match in direction, the bending of the magnetic brush 51 becomes small.

In any case, as mentioned above, the magnetic brush 5 is
1 is in a fine but intense vibration state, and the fog toner that has adhered excessively on the latent image holding member 3 is rubbed by the magnetic brush 51 and removed from the latent image holding member 3.
It is pulled back onto the magnetic brush 51. Further, due to the vibration of the magnetic brush 51, the toner is easily separated from the magnetic brush 51 (and is easily supplied to the latent image holding member 3, so that the image density is also improved. The toner is loosened within the magnetic brush 51 and contributes to improving image density and preventing ghosting.Furthermore, when this vibration state is severe, a part of the magnetic brush 51 separates from the top of the magnetic brush 51 or the toner carrying member 22, and the latent image is retained. A reciprocating motion is generated between the member 3 and the surface of the toner carrying member 22. The kinetic energy of this reciprocating magnetic brush 51 is large, and the above-mentioned vibration effect is expected to be efficient. The behavior of the magnetic particles 27 was determined by high-speed imaging at 8000 frames per second using a high-speed camera.
This 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.

Example 1 A black toner was obtained by externally adding 1.0 parts by weight of cyclic silica fine powder. In addition, cyan toner, magenta toner,
I got yellow toner.

These toners τ were melt-kneaded using a twin-screw extruder, cooled, and then coarsely ground using a hammer mill to about 1 to 2 a+m, and then finely ground using an air jet type pulverizer. Further, the particles were classified using an air classifier, and colorant-containing resin particles were obtained by selecting a particle size distribution of 2.0 to 10.0 μm so as to have the particle size distribution of the present invention. Furthermore, amino-modified silicone oil was added to 100 parts by weight of the resin particles.

These toners were mixed with ferrite particles (true specific gravity 5.0 g/cm'') coated with a fluoroacrylic resin at a ratio of 1:9 to obtain toners of each color.

Using these toners, images were produced using a commercially available full-color copying machine (Color Laser Copier 500, manufactured by Canon) and a developing device modified for positive use. A positively charged amorphous silicon drum was used as the latent image holding member 3, and a toner carrying member 22 was used as the toner carrying member 22, which was coated with a polyester resin in which 45 parts by weight of crystalline graphite was dispersed on the surface of an aluminum cylinder. .

The surface of the latent image holding member 3 facing the toner carrying member 22 has a gap of 300 μm between the toner carrying member 22 and the latent image holding member 3 for a latent image of +30 V in the dark area and +400 V in the bright area as an electrostatic latent image. and set it to an alternating electric field (1,4kV
Development was performed by applying a developing bias voltage in which a DC electric field (pp, 0.8 kH2) was superimposed.

As a result, a clear image with a high image density (and no fogging at all) was obtained.Furthermore, as a result of a durability test of 5,000 sheets, the image density was stable and the image was clear. There was almost no toner scattering inside the machine.

Example 2 Phthalocyanine pigment, rhodamine pigment, C,1, Pigment Yellow 17. 4 each of carbon black
Parts by weight were added and the same procedure as in Example 1 was carried out to obtain colorant-containing particles of four colors. 0.5 parts by weight of silica fine powder treated with hexamethyldisilazane and 0.5 parts by weight of alumina fine powder are externally added to 100 parts by weight of the above colorant-containing particles to produce cyan toner, magenta toner, yellow toner, and black toner. Got toner.

These toners were prepared in the same manner as in Example 1. Image output evaluation was performed using a commercially available full-color copier (Color Laser Copier 5).
00. (manufactured by Canon) and the developing device, except that the toner carrying member 22 was an aluminum cylinder whose surface was coated with styrene resin in which 30 parts by weight of crystalline graphite was dispersed. 5,0
As a result of the durability test of 00 sheets, as in Example 1, the image density was stable and a clear image without fogging was obtained.

Example 3 Images were evaluated in the same manner as in Example 1, except that the coating agent for the toner carrying member 22 was changed to a butadiene-acrylonitrile copolymer in which 40 parts by weight 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.

Comparative Example 1 The same toner as in Example 1 was used, an aluminum sleeve sandblasted with irregular shape using Alundum abrasive grains without surface coating was used in place of the toner carrying member 22 of Example 1, and image formation was carried out in the same manner as in Example 1. I did some endurance. As a result, although the initial image had good density and image quality, the image density decreased after a durability test of about 500 sheets.

Comparative Example 2 Durability was carried out in exactly the same manner as in Example 2 except that a toner having the same particle size distribution as in Example 2 was used.

As a result, the image density became lower than the initial level, and fogging, toner scattering, etc. occurred.

[Effects] According to the present invention, a clear image with high image density, excellent fine line reproducibility and highlight gradation, and no fog can be obtained.

Further, there is almost no toner scattering inside the copying machine, and stable performance and images can be obtained even during long-term use.

[Brief explanation of the drawing]

FIG. 1 is an example of the full-color image forming method of the present invention, and FIGS. 2 and 3 are enlarged views of the development area. 3: Latent image holding member 21: Toner supply container 22: Toner carrying member 23: Fixed magnet 24: Non-magnetic blade 26: Hi-Gun Publishing I Koku Sokuri 1 Goods 27: Magnetic particles
28: Non-magnetic toner 29: Toner collection container portion 30: Scattering prevention member 31: Magnetic member 32: Development area 3
4: Alternating voltage power supply 50:? iF image charge 51: magnetic brush

Claims (3)

[Claims] (1) Color-separate the original image, form a latent image for each color on a latent image holding member, and develop the latent image with color toner in a development area between the latent image holding member and a toner carrying member opposing it. In full color image forming method, true specific gravity is 6g/cm
Using magnetic particles having a particle diameter of ^3 or less and coated with an electrically insulating resin, a magnetic brush is applied so that the amount of the magnetic particles is 5 to 1000 mg/cm^2 in the development area of the toner carrying member. A developing method characterized in that the latent image is developed with non-magnetic color toner between the latent image holding member and the magnetic brush surface formed on the surface of the toner carrying member in the development area, and the volume average particle size of the non-magnetic color toner is 6.0 to 10.0 μm, and 5.0 μm.
15 to 40% by number of toner particles having a particle size of μm or less
0.1 to 5.0% by volume of toner particles having a particle size of 12.7 to 16.0 μm are contained, and the particle size is 16.0 μm.
The toner particles containing 1.0% by volume or less and having a particle size of 6.35 to 10.1 μm are expressed by the following formula 9.
≦V×@d@v/N≦14 V: Volume % of toner particles having a particle size of 6.35 to 10.1 μm N: Number % of toner particles having a particle size of 6.35 to 10.1 μm @ d@v: A full-color image forming method characterized by having a particle size distribution that satisfies the volume average particle size of all toner particles. (2) The full-color image forming method according to claim 1, wherein the surface of the toner carrying member has a resin layer containing at least fine particles having solid lubricating properties. (3) A micro gap is formed between the latent image holding member and the surface of the toner layer on the toner carrying member, and an alternating electric field is applied to this gap.
) Full color image forming method described.