JP2759547B2 - Full-color image forming method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method used for forming a full-color image by an electrophotographic method.

2. Description of the Related Art A full-color toner for electrophotography is basically a combination of a yellow toner, a magenta toner, a cyan toner and, if necessary, a black toner. No. 50-776, Japanese Patent Publication No. 53-
No. 47174, JP-B-53-47175, JP-B-53-4717
It is described in, for example, No. 6 gazette.

As a method of developing a full-color toner, various methods have been proposed and put to practical use. However, for example, in a developing method using two-component toner, the developing efficiency is poor, and in order to obtain a predetermined sufficient developing density, it is necessary to uniformly apply a predetermined amount of color toner density on a developing roller,
For this reason, there is a disadvantage that the configuration of the developing device becomes large and complicated. In addition, a method of applying soft toner such as beaver hair to a cylindrical brush and applying toner to the brush, or a method of applying a developing roller made of velvet or the like to a developing roller using a doctor blade or the like. Has been proposed.

However, when an elastic blade is used as a doctor blade for the above-mentioned brush, the amount of toner can be regulated, but uniform application is not performed, and the brush between the brushes is merely rubbed with the brush on the developing roller. Since no triboelectric charge is applied to the existing toner, there is a problem that fog or the like is easily generated.

Further, magnetic toners can easily prevent toner scattering by using magnetic force, but non-magnetic toners cannot use magnetic force, and toner easily scatters in the apparatus.
The above disadvantages occur not only when copying, but also when vibrations or impacts are given during transport of the apparatus.

The present applicant uses a non-magnetic toner and magnetic particles as a developing device completely different from the above-described conventional method, and provides a magnetic particle restraining member opposed to the toner carrying member to move the toner carrying member in the moving direction of the surface of the toner carrying member. A method of forming a magnetic brush of magnetic particles by the magnetic force of the magnetic field generating means upstream of the particle restraining member, restraining the magnetic brush by the magnetic particle restraining member, and forming a thin layer of non-magnetic toner on the toner carrying member has already been described. It was proposed (JP-A-58-143360). Using this method, the gap between the latent image holding member and the toner carrying member in the developing area is set wider than the toner layer thickness, and an alternating electric field is applied to obtain a non-magnetic toner developed image on the surface of the latent image holding member. The method was put to practical use.

This makes it possible to obtain a color developed image with a very high developing efficiency and a small and simple developing device configuration. In particular, there was no rubbing trace generated on the solid image portion during the two-component magnetic brush rubbing development, and a good quality solid image was obtained. However, it has been desired to further improve a developed image, for example, to develop a developing method for further improving the gradation.

As still another developing method, a toner container for storing toner and magnetic particles for toner application, and a toner carrying member for transporting toner to a latent image holding member are arranged, and the toner carrying member is used by using the magnetic particles. A magnetic brush is formed in the developing area, and the gap between the toner carrying member and the latent image holding member is set to be larger than the magnetic brush layer thickness to develop an electrostatic image.

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

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, and the like increase. For this reason, the adhesion between the toner and the surface of the toner carrying member is increased, which causes charge-up. For this reason, charge-up can be prevented for the non-magnetic toner attached to the magnetic particles by appropriate selection of the magnetic particles, but sufficient measures have not been taken for the non-magnetic toner directly attached to the toner carrying member. As a result, the use of full-color toner having a small particle size was insufficient.

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

A further object of the present invention is to provide a full-color image forming method having high image density, fine line reproducibility, and excellent highlight gradation.

It is a further object of the present invention to provide a full-color image forming method in which the performance does not change even when used for a long time.

[Means and Actions for Solving the Problems] The above object is achieved by the following configurations of the present invention.

The present invention is a development area of a color separation of a document image, forming a latent image for each color on a latent image holding member, and a developing area of the latent image holding member and a toner carrying member including a magnet inside the opposed to the latent image holding member.
The latent image is developed by a color toner of a color brush corresponding to each of the color-separated colors carried on the toner carrying member and a magnetic brush formed by a two-component developer having magnetic particles. In a full-color image forming method in which the step of forming an image is repeated for each color, the amount of magnetic particles conveyed to a developing area is regulated, and the magnetic particles are circulated in a toner supply container. The component-based developer is conveyed to the developing area, and the true specific gravity is 6 g / cm ³ or less, and the magnetic particles coated with an electrically insulating resin are used on the toner carrying member. The amount of magnetic particles present is 50-100 mg /
forming a magnetic brush so as to have a diameter of ² cm, and developing the latent image of the latent image holding member with a non-magnetic color toner of the magnetic brush formed on the surface of the toner carrying member; A resin layer containing fine particles having solid lubricity is formed on the surface of the supporting member, and the non-magnetic color toner has a volume average particle diameter of 6.0 to 10.0.
μm, and toner particles having a particle size of 5.0 μm or less
0.1 to 5.0% by volume of toner particles having a particle size of 12.7 to 16.0 μm, and 1.0% by volume or less of toner particles having a particle size of 16.0 μm or more;
5 to 10.1 μm toner particles have the following formula 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 v: having a particle size distribution satisfying the volume average particle size of all toner particles And a full-color image forming method.

Hereinafter, regarding the full-color image forming method of the present invention,
Give details.

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

That is, in the present invention, the volume average diameter of the color toner is
6.0 to 10.0 μm, containing 15 to 40% by number of toner particles having a particle diameter of 5.0 μm or less, 0.1 to 5.0% by volume of 12.7 to 16 μm, 1.0% by volume or less of 16 μm or more, and 6.35 to 10.1
μm toner particles have the following formula Satisfying is an important point.

That is, the above value indicates the width of the particle size distribution in the volume average particle size of each toner, and when the particle size distribution is adjusted by general air classification, that the above value is large means that each toner The width of the particle size distribution in the volume average particle size becomes broad and faithfully reproduces a minute dot latent image.
Conversely, the fact that toner particles of about μm increase and the above value is small indicates that the width of the particle size distribution in the volume average particle diameter of each toner becomes sharp, and that toner particles of about 5 μm decrease. Is done.

Therefore, when v 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.

For toner particles having a particle diameter of 16.0 μm or more, 1.
It is preferable that the content is 0 volume% or less and the amount is as small as possible. 5.0
15 to 40% by number of toner particles with a particle size of less than μm
And more preferably 20 to 35% by number. When the toner particles having a particle size of 5.0 μm or less are less than 15% by number, the amount of toner particles effective for high image quality is small. In particular, as the toner is used by continuing copy or printout, the effective toner particle components are reduced. Decrease,
The balance of the particle size distribution of the toner deteriorates, and the image quality gradually decreases. On the other hand, if the content is 40% by number or more, the toner particles tend to aggregate with each other, and the fluidity is impaired.

Further, the particle size in the range of 12.7 to 16.0 μm is preferably 0.1 to 5.0% by volume, and more preferably 0.2 to 3.0% by volume. Five.
If the content is more than 0% by volume, the image quality is deteriorated, and the development is performed more than necessary, that is, the toner is excessively applied, which causes an increase in toner consumption. On the other hand, when the content is less than 0.1% by volume, the image density is reduced due to the decrease in fluidity.

Further, the content of toner particles having a particle size of 16.0 μm or more is preferably 1.0% by volume or less, more preferably 0.6% by volume or less.

Further, the volume average diameter of the toner is 6.0 to 10.0 μm, and preferably 7.0 to 9.0 μm, and this value cannot be considered separately from the above-described components. When the volume average particle diameter is less than 6.0 μm, in applications having a high image area ratio such as a graphic image, a problem that the amount of toner on the transfer paper is small and the image density is low tends to occur. If the volume average particle diameter is 10.0 μm or more, the resolution is not good, and the image quality is liable to deteriorate at the beginning of copying, if the use is continued at best.

Examples of the thermoplastic resin that can be used include homopolymers of styrene such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene, styrene-p-chlorostyrene copolymer, and styrene-vinyltoluene copolymer, and substituted polymers thereof, and copolymers thereof. Coalescence: Styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-
A copolymer of styrene and an acrylate such as an n-butyl acrylate copolymer; a styrene-methyl methacrylate copolymer, a styrene-ethyl methacrylate copolymer,
Copolymers of styrene and methacrylate such as styrene-n-butyl methacrylate copolymer; styrene and acrylate and methacrylate; styrene and dimethylaminoethyl methacrylate and acrylate; styrene and diethylaminoethyl methacrylate; Multi-component copolymers such as acrylic esters; other styrene-acrylonitrile copolymers, styrene-vinyl methyl ether copolymers, styrene-butadiene copolymers, styrene-vinyl methyl ketone copolymers, styrene-acrylonitrile-indene copolymers Coalescence, styrene-
Styrene copolymers of styrene such as maleic ester copolymers with other vinyl monomers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyester, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid, phenol Resins, aliphatic or alicyclic hydrocarbon resins, petroleum resins, chlorinated paraffins, and the like can be used alone, mixed or in combination. Particularly, a styrene-acrylic resin and a polyester resin are preferable.

The toner according to the present invention may contain a charge control agent in order to stabilize the charge characteristics. At that time, a colorless or light-colored charge control agent that does not affect the color tone of the toner is preferable.

As the colorant used in the present invention, known dyes and pigments,
For example, phthalocyanine blue, induslen blue, peacock blue, permanent red, lake red,
Rhodamine lake, Hansa yellow, permanent yellow, benzine yellow and the like can be widely used.
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 reflect sensitively on 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 the fluidity.

Examples of the fluidity-imparting agent include, but are not necessarily limited to, the following. For example, Al ₂ O ₃ ,
Metal oxides such as TiO ₂ , GeO ₂ , ZrO ₂ , Sc ₂ O ₃ , HfO ₂ , SiC, Ti
There are carbides such as C and W ₂ C, and nitrides such as Si ₃ N ₄ and Ge ₃ N ₄ ,
Among them, for color toners, it is colorless or white that adding 2% by weight or less of Al ₂ O ₃ , TiO ₂ , Sc ₂ O ₃ , ZrO ₂ , GeO ₂ , HfO ₂ to the toner is less than 2% by weight. When used for
It is suitable without adversely affecting the color.

Additives may be added to the toner of the present invention as needed as long as the properties of the toner are not impaired.
Lubricants such as zinc stearate, polyvinylidene fluoride,
Or fixing aids such as low molecular weight polyethylene and low molecular weight polypropylene.

In the production of the toner of the present invention, a method of kneading the constituent materials well by a heat kneader such as a hot roll, a kneader, an extruder and the like, and then mechanically pulverizing and classifying the toner, Or a method of obtaining a toner by dispersing such materials and spray-drying, or by mixing a predetermined material with a monomer to constitute a binder resin and then polymerizing this emulsion suspension to obtain a toner. Each method such as a toner manufacturing method can be applied.

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

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

In addition to the fine particles having solid lubricating properties, conductive fine particles, semiconductive metal oxides, etc. are simultaneously contained in the resin layer for the purpose of leaking the charge of the fine powder of the charged toner, so that the volume of the resin layer is specific. There is also a method of reducing the resistance to 10 ⁵ Ωcm or less, but in this case, the resistance is preferably set to 10 ³ Ωcm or less, and even in this case, it is necessary to include the fine particles having solid lubricity in the resin layer at the same time. is there.

The fine particles having solid lubricity of the present invention include graphite,
Graphite fluoride, molybdenum disulfide, tungsten disulfide,
Boron nitride, silicon nitride, calcium fluoride, barium fluoride, lead monoxide, molybdenum trioxide, and the like are used, and those having crystallinity and having a relatively small triboelectric charge to the toner are preferable. Particularly, crystalline graphite is preferable.

The method for forming a resin layer on the surface of the toner carrying member in the present invention will be described.

Common coating methods include dipping, spraying, roll coating, curtain coating,
There are a sputtering method and the like, and a dipping method and a spraying method are particularly excellent for applying the coating of the present invention.

Specifically, in the spraying method, the coating resin as a solid content is dissolved in a solvent, and the contents such as fine particles having solid lubricity are mixed with glass beads and dispersed with a paint shaker. The mixture is filtered through a mesh or the like to form a paint, which is adhered to a cylinder of the toner carrying member by an air spray method so as to have a uniform thickness, and dried by heating.

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

The fine particles having solid lubricity used in the present invention preferably have a particle size of 0.5 μm to 10.0 μm.

The film-forming polymer material is, for example, a thermoplastic resin such as a styrene resin, a vinyl resin, a polyether sulfone resin, a polycarbonate resin, a polyphenylene oxide resin, a polyamide resin, a fluororesin, a cellulose resin, an acrylic resin, or an epoxy resin. A thermosetting resin such as a resin, a polyester resin, an alkyd resin, a phenol resin, a melamine resin, a polyurethane resin, a urea resin, a silicone resin, and a polyimide resin, or a photocurable resin can be used. Among them, silicone resins, those with release properties such as fluororesins, or polyether sulfone,
Those having excellent mechanical properties such as polycarbonate, polyphenylene oxide, polyamide, phenol, polyester, polyurethane and styrene resin are more preferable.

Hereinafter, the present developing method will be described. FIG. 1 is an example according to the present invention. In FIG. 1, 3 is a latent image holding member, 21 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 circulating area limiting member, 27 is a magnetic particle, 28 is a non-magnetic toner, 29 is a toner collecting container part, 30 is a scattering prevention member, 31 is a magnetic member, 32 is a developing area, 34 Indicates a bias power supply. The toner carrying member 22 rotates in the direction b, and the magnetic particles 27 circulate in the direction c accordingly. As a result, contact and rubbing between the surface of the toner carrying member 22 and the layer of magnetic particles 27 occur, and a layer of non-magnetic toner 28 is formed on the surface of the toner carrying member 22. Further, while the magnetic particles 27 circulate in the direction c, a part thereof is regulated to a predetermined amount by a gap between the non-magnetic blade 24 and the toner carrying member 22, and is applied onto the non-magnetic toner 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 an effect equivalent to substantially increasing the surface area of the toner carrying member 22 is exhibited. The coating amount of the magnetic particles 27 on the surface layer of the non-magnetic blade 24 downstream toner carrying member 22 in the present invention is
In order to make full use of the magnetic brush composed of 27 and the surface of the toner carrying member 22, it is desirable that the amount is as small as about 5 mg / cm ^{2 to} 100 g / cm ² .

In the developing area 32, one of the magnetic poles of the fixed magnet 23 is opposed to the latent image surface to form a clear developing pole, and the alternating electric field is used to form the toner carrying member 22 and the magnetic particles 27.
The toner is developed by flying. (The development will be described later.) After the development, the magnetic particles 27 and the undeveloped toner are collected in the toner supply container 21 with the rotation of the toner carrying member 22.

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, the magnetic particles 27 to be described later are clogged, and the toner carrying member 22
There is a disadvantage to hurt. On the other hand, if it is larger than 500 μm, a large amount of non-magnetic toner 28 and magnetic particles 27 which will be described later leak out and a thin layer cannot be formed.

In FIG. 1, reference numeral 26 denotes a magnetic particle circulation region limiting member having a lower surface in contact with the upper surface of the non-magnetic blade 24 and a front end surface as an undercut surface.

Numerals 27 and 28 denote magnetic particles and non-magnetic toner sequentially accommodated in the toner supply container 21.

The bottom plate of the toner supply container 21 is extended below the toner carrying member 22 so that toner does not leak outside. In order to further prevent the leakage of the toner to the outside, a toner collecting container portion 29 for receiving and restraining the leaked toner is provided on the upper surface of the extension bottom plate, and scattering is prevented along the longitudinal edge of the leading edge of the extension bottom plate. A member 30 is provided. A voltage described later is applied to the scattering prevention member 30.

The magnetic particles 27 generally have an average particle size of 30 to 100 μm, preferably 40 to 80 μm. Each magnetic particle 27 may be composed of only a magnetic material, a combination of a magnetic material and a non-magnetic material, or a mixture of two or more magnetic particles 27. The magnetic particles 27 are first charged into the toner supply container 21 so that the magnetic particles 27 face the toner supply container 21 in the surface area of the toner carrying member 22, that is, the toner in which the toner carrying member 22 is disposed. Magnetic member 27 for preventing leakage of magnetic particles 27 or toner from supply container 21
The toner carrying member 22 is provided at each part of the surface area of the toner carrying member 22 from the end 31 of the non-magnetic blade 24 as a magnetic particle restraining member.
The magnetic field generated by the fixed magnet 23 in the inside causes the toner holding member 22 to be entirely held as a layer of magnetic particles 27 as a magnetic particle 27 layer. The non-magnetic toner 28 is charged into the toner supply container 21 after the magnetic particles 27 have been charged, so that a large amount of the non-magnetic toner 28 is stored outside the magnetic particles 27 as the first layer with respect to the toner carrying member 22, and Exists as a layer.

It is preferable that the magnetic particles 27 initially charged contain the non-magnetic toner 28 in an amount of about 2 to 70% (by weight) with respect to the magnetic particles, but it is also possible to use only the magnetic particles. Also, once the magnetic particles 27 are adsorbed and held as a layer of magnetic particles 27 in the surface area of the toner carrying member 22, the device does not vibrate or flow substantially substantially even if the device is tilted considerably. The state where the surface area of the toner carrying member 22 is entirely covered is maintained.

Thus, the magnetic particles 27 are stored in the toner supply container 21 as described above.
And the non-magnetic toner 28 are sequentially charged and accommodated, the magnetic particles 27 layer near the surface of the toner carrying member 22 corresponding to the position of the magnetic pole S ₂ of the fixed magnet 23 is provided with a magnetic field of a strong magnetic pole. Magnetic brush is formed.

The magnetic particle layer in the vicinity of the tip of the non-magnetic blade 24 is regulated based on the gravity, the magnetic force, and the effect of the presence of the non-magnetic blade 24 even when the toner carrying member 22 is driven to rotate in the direction of arrow b. Due to the balance between the force and the conveying force of the toner carrying member 22 in the moving direction, the toner accumulates at the point 25 on the surface of the toner carrying member 22 and forms a stationary layer which can move slightly but is slightly movable.

Also when rotating the toner carrying member 22 in the arrow b direction, by choosing the fluidity and magnetic properties of the arrangement positions and the magnetic particles 27 of the magnetic poles properly, the magnetic brush in the direction of arrow c in the vicinity of the magnetic pole S ₂ Circulates to form a circulating layer. In the circulating layer, relatively near the magnetic particles was the toner carrying member 22 amounted prime from the pole S ₂ near the rotation of the toner carrying member 22 onto the stationary layer on the rotation downstream side of the toner carrying member 22.
That is, it receives a force that is pushed upward. The pushed-up magnetic particles do not climb onto the non-magnetic blade 24 because the upper limit of the circulating region is determined by the magnetic-particle circulating-region limiting member 26 provided above the non-magnetic blade 24. falls by, returning again to the magnetic pole S ₂ vicinity. In this case, the magnetic particles having a small push-up force received, for example, by being located far from the surface of the toner carrying member 22 may fall before reaching the magnetic particle circulation area limiting member 26. In other words, in the circulating layer, the magnetic brush of the magnetic particles 27 is circulated as indicated by the arrow c by the magnetic force and frictional force due to gravity and magnetic poles and the fluidity (viscosity) of the magnetic particles 27. The non-magnetic toner 28 is sequentially taken in from the toner layer above the particle layer, returns to the lower part in the toner supply container 21, and repeats this circulation with the rotation driving of the toner carrying member 22.

The developing bias voltage applied from the alternating voltage power supply 34 is
An alternating voltage having the same peak voltage on the plus side and the minus side, or a DC voltage superimposed on this alternating voltage can be used. For example, for an electrostatic latent image having a dark portion latent image potential of −600 V and a bright portion latent image potential of −200 V, as an example, a DC voltage of −300 V is superimposed on the toner carrying member 22 to form a waveform peak voltage Vpp 300 to 2000.
V, an alternating voltage selected in the frequency range of 200 to 3000 Hz is applied to hold the latent image holding member 3 at the ground potential.

Generally, the electric resistance of the magnetic brush is relatively high (10 ⁸ Ωc
m), the peak voltage width Vpp of the developing bias voltage is preferably higher (for example, 800 V or more), and the frequency is 600H.
A higher image quality of z or more, preferably 800 Hz or more, more preferably 1 KHz or more, provided good image quality with sufficient density. Even if only Vpp is high, if the frequency is low, the density is low, and it is 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 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 a relatively high resistance, by appropriately selecting the frequency of the alternating electric field to be applied and the time constant of the magnetic brush itself, the peak value of the alternating electric field is set so that the gap voltage does not reach the firing voltage. Is preferred.

The resistance value of the magnetic particles 27 and the magnetic brush described in the present invention means that a magnetic brush of a large amount of the magnetic particles 27 is formed on the toner carrying member 22, and the gap between the magnetic brush and the toner carrying member 22 is opposite. It is obtained by calculating from the value of current flowing when a voltage of 200 V DC is applied to a circuit in which a metal drum holding 5 mm is provided and a resistor of about 1 MΩ is connected in series with the metal drum.

Hereinafter, the development in the development region 32 will be described for the development method according to the present invention.

2 and 3 are enlarged explanatory views of the development area 32 in the development method according to the present invention. Reference numeral 50 denotes a latent image charge in a dark portion on the latent image holding member 3. 28 is a non-magnetic toner. Reference numeral 34 denotes an alternating voltage power supply on which a DC component is superimposed. FIG. 2 shows a case where a positive waveform component of the alternating voltage is applied to the toner carrying member 22, and FIG. 3 shows a case where a negative waveform component of the alternating voltage is added. The polarity of the latent image charge 50 is shown as minus, and the polarity of the toner is shown as plus.

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

Since the resistance of the magnetic brush 51 is relatively large (greater than about 10 ⁸ Ωcm), the magnetic brush 51 has friction with the non-magnetic toner 28 depending on the charge / discharge time constant of electric charge due to the material of the magnetic brush 51 itself and the like. There will be an electric field injected by the charged or reflected charge, the latent image electric field on the latent image holding member 3 and the alternating electric field between the latent image holding member 3 and the toner particle holding member 22.

When the electric field due to the latent image charge 50 in the dark portion on the latent image holding member 3 and the electric field due to the alternating electric field match, the magnetic brush 51 is in the maximum bending state toward the toner carrying member 22.

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

In any case, as described above, the magnetic brush
Reference numeral 51 denotes a fine but intense vibration state, and the fog toner excessively attached on the latent image holding member 3 is removed by the magnetic brush.
The toner is rubbed and removed from the latent image holding member 3 by the brush 51, and is pulled back onto the magnetic brush 51. Also, due to the above vibration of the magnetic brush 51, the toner is easily detached from the magnetic brush 51,
Since the toner is easily supplied to the latent image holding member 3, the image density is also improved. Further, the toner is loosened in the magnetic brush 51 by the vibration of the magnetic brush 51, which contributes to improvement of image density and prevention of ghost. Furthermore, if this vibration condition is severe,
A part of the magnetic brush 51 is detached from the magnetic brush 51 or the toner carrying member 22, and the latent image holding member 3 and the toner carrying member
Generates reciprocating motion with 22 surfaces. The kinetic energy of the reciprocating magnetic brush 51 is large, and the effect of the above-described vibration is expected to be efficient. The behavior of the magnetic particles 27 in the development area 32 described above is a phenomenon observed during the course of high-speed shooting of 8000 frames per second with a high-speed camera.

[Examples] Next, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited thereto.

Example 1 Was melt-kneaded by a twin-screw extruder, cooled, roughly crushed by a hammer mill to about 1 to 2 mm, and then finely crushed by an air jet-type fine crusher. Classification is further performed using an air classifier so that the particle size distribution of the present invention is obtained.
Coloring agent-containing resin particles were obtained by selecting from 0 to 10.0 μm. Further, 1.0 part by weight of amino-modified silicon oil-treated silica fine powder was externally added to 100 parts by weight of the resin particles to obtain a black toner. Cyan toner, magenta toner and yellow toner were obtained in the same manner except that carbon black was changed to phthalocyanine pigment, rhodamine pigment and CI Pigment Yellow 17 and nigrosine was changed to quaternary ammonium salt.

These toners are Met.

These toners were mixed with ferrite particles (true specific gravity of 5.0 g / cm ³ ) coated with a fluoroacrylic resin at a ratio of 1: 9 to obtain toners of each color.

Using these toners, all four-color developing devices of a commercially available full-color copying machine (Color Laser Copier 500, manufactured by Canon) were modified into the developing devices shown in FIG. . As the latent image holding member 3, a positively chargeable amorphous silicon drum was used, and as the toner holding member 22, a toner holding member 22 coated with a polyester resin in which 45 parts by weight of crystalline graphite was dispersed on the surface of an aluminum cylinder was used. .

On the surface of the latent image holding member 3 opposed to the toner holding member 22, a gap between the toner holding member 22 and the latent image holding member 3 is set to 300 for a latent image of a dark portion + 30V and a bright portion + 400V as an electrostatic latent image.
The development was performed by applying a developing bias voltage in which an alternating electric field (1.4 kVpp, 0.8 kHz) and a DC electric field were superimposed thereon. The amount of magnetic particles present in the developing region of the magnetic brush formed on the toner carrier was 40 mg / cm ² , which is the same as the setting condition of the color laser copier 500.

As a result, a clear image having a high image density and no fog was obtained. Furthermore, as a result of performing a durability test on 5000 sheets, the image density was stable and the image was clear. In addition, toner scattering in the copying machine hardly occurred.

Example 2 4 parts by weight of a phthalocyanine pigment, a rhodamine pigment, CI Pigment Yellow 17, and carbon black were added to the mixture, and four colorant-containing particles were obtained in the same manner as in Example 1. A cyan toner, a magenta toner, a yellow toner and a black toner were obtained by externally adding 0.5 parts by weight of hexamethyldisilazane-treated silica fine powder and 0.5 parts by weight of alumina fine powder to 100 parts by weight of the colorant-containing particles. .

These toners are Thus, a toner was prepared in the same manner as in Example 1. Image evaluation was performed using a commercially available full-color copier (Color Laser Copier 500, manufactured by Canon Inc.) with a developing device configured to regulate the amount of magnetic particles transported to the development area and circulate the magnetic particles in the toner supply container. A) a developing device of a magnetic brush formed on a toner carrying member using a toner carrying member having a surface of an aluminum cylinder coated with a styrene resin in which 30 parts by weight of crystalline graphite is dispersed as a toner carrying member; The amount of the magnetic particles in the above was set to 40 mg / cm ² which is the same condition as the setting condition of the color laser copier 500. As a result of the durability test of 5,000 pieces,
As in Example 1, the image density was stable, and a clear image without fog was obtained.

Example 3 The coating agent of the toner carrying member 22 was made of crystalline graphite.
An image formation evaluation was performed in the same manner as in Example 1 except that the butadiene acrylonitrile copolymer dispersed in 40 parts by weight was changed. As a result of the durability test on 5,000 sheets, the image density was stable as in Example 1, and a clear image without fog was obtained.

Comparative Example 1 The same toner as in Example 1 was used, and instead of the toner carrying member 22 of Example 1, an aluminum sleeve which had been subjected to irregular sand blasting using alundum abrasive grains not coated on the surface was used, and image formation was performed in the same manner as in Example 1. Endurance was performed. As a result, the initial image was good in both density and image quality, but the image density was lowered by the durability test of about 500 sheets.

Comparative Example 2 In Example 2, the toner particle size distribution was The durability was carried out in exactly the same manner as in Example 2 except that the toner described above was used.

As a result, the image density was lower than the initial stage, and fog, toner scattering and the like occurred.

[Effects] According to the present invention, a clear image with high image density, excellent fine line reproducibility, and excellent highlight gradation can be obtained without any fog.

Further, there is almost no toner scattering in the copying machine, and stable performance and images can be obtained even when used for a long time.

[Brief description of the drawings]

FIG. 1 is an example of a full-color image forming method of the present invention, and FIGS. 2 and 3 are enlarged views of a development area. 3: Latent image holding member, 21: Toner supply container 22: Toner carrying member, 23: Fixed magnet 24: Non-magnetic blade, 26: Magnetic particle circulation area limiting member 27: Magnetic particles, 28: Non-magnetic toner 29: Toner trap Collection container part, 30: scattering prevention member 31: magnetic member, 32: developing area 34: alternating voltage power supply, 50: latent image charge 51: magnetic brush

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroaki Kawakami 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masashi Jimbo 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (56) References JP-A-2-877 (JP, A) JP-A-63-170660 (JP, A) JP-A-47-13088 (JP, A) JP-A-57-66443 (JP, A) A)

Claims (3)

(57) [Claims] A latent image is formed on a latent image holding member by forming a latent image for each color on a latent image holding member. The latent image holding member is opposed to the latent image holding member with a toner carrying member having a magnet therein. ,
The latent image is developed by a color toner of a color brush corresponding to each of the color-separated colors carried on the toner carrying member and a magnetic brush formed by a two-component developer having magnetic particles. In a full-color image forming method in which the step of forming an image is repeated for each color, the amount of magnetic particles conveyed to a developing area is regulated, and the magnetic particles are circulated in a toner supply container. The component-based developer is conveyed to the developing area, and the true specific gravity is 6 g / cm ³ or less, and the magnetic particles coated with an electrically insulating resin are used on the toner carrying member. The amount of magnetic particles present is 50-100 mg /
forming a magnetic brush so as to have a diameter of ² cm, and developing the latent image of the latent image holding member with a non-magnetic color toner of the magnetic brush formed on the surface of the toner carrying member; A resin layer containing fine particles having solid lubricity is formed on the surface of the supporting member, and the non-magnetic color toner has a volume average particle diameter of 6.0 to 10.0.
μm, and toner particles having a particle size of 5.0 μm or less
5 to 40% by number, 0.1 to 5.0% by volume of toner particles having a particle size of 12.7 to 16.0 μm, and 1.0% by volume or less of toner particles having a particle size of 16.0 μm or more;
5 to 10.1 μm toner particles have the following formula 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 v: having a particle size distribution satisfying the volume average particle size of all toner particles A full-color image forming method. 2. An image forming apparatus according to claim 1, wherein a developing bias voltage is applied to said toner carrying member to form an alternating electric field in a developing area between said latent image holding member and said toner carrying member, thereby performing development. The method for forming a full-color image according to claim 1. 3. The fine particles having solid lubricating properties include graphite, graphite fluoride, molybdenum disulfide, tungsten disulfide, boron nitride, silicon nitride, calcium fluoride, barium fluoride, lead monoxide and molybdenum trioxide. The particles are selected from the group consisting of:
Or the full-color image forming method according to 2.