JPH0954461A - Developer for forming color image and color image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain stable developing performance and a color reproduced image without deteriorating color reproducibility by using a polyolefin coated carrier contg. specified fine particles in the resin coating layer. SOLUTION: In this developer consisting of a carrier and a color toner consisting of a bonding resin and a colorant, the carrier is a polyolefin coated carrier contg. fine particles having a whiteness of <=0.2 and <=0.5μm number average primary particle diameter. The carrier is obtd. by coating the surfaces of magnetic particles with polyolefin. The fine particles contained in the carrier coating resin are preferably electrically conductive fine particles having 1×10<2> -1×10<11> Ωcm volume resistivity, e.g. fine particles of poly-acetylene resin, zinc oxide, tin oxide, titanium dioxide or ITO as indium-tin multiple oxide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer used as a color developer using a chromatic color toner and a color image forming method.

[0002]

2. Description of the Related Art As a color developer for forming a color image by an electrophotographic method, it is not necessary to introduce an additive such as magnetic powder which hinders the tint into the toner, and the hue can be adjusted relatively. An easy-to-use two-component developer composed of so-called toner and carrier is often used. As the carrier used here, a carrier in which magnetic particles composed of ferrite, iron powder, or the like is used as it is, or a resin-coated carrier in which the surface of these magnetic particles is coated with a resin is known. Of these, resin-coated carriers are preferably used from the viewpoints of ease of charge control and carrier durability.

Conventionally, styrene / acrylic resins, polyester resins, silicone resins and the like have been widely used as carrier coating resins. Recently, it has been proposed to coat the carrier with polyolefin.

Since the resin itself does not have a polar group, polyolefin has good water repellent property and releasability, and therefore, it is said that it has excellent durability when applied to an electrophotographic carrier.

However, polyolefin is generally used as an insulating material, and when it is used as a carrier coating resin, the volume resistivity, which is the electrical resistance value of the carrier, becomes extremely high. When a carrier having an excessive volume resistivity is used as a carrier for electrophotography, a sufficient amount of development cannot be obtained, which causes insufficient image density. Then, in order to solve the problem, Japanese Patent Laid-Open No. 2-18
As disclosed in Japanese Patent Application No. 7771 and Japanese Patent Application Laid-Open No. 6-266168, it has been proposed to add conductive fine particles to the coating layer to control the volume resistivity of the carrier. Here, as the conductive fine particles, conductive carbon black is used because the carrier resistance can be relatively easily lowered with a small amount.

In recent years, various proposals have been made for using electrophotographic technology in a color image forming method. In this case, it is an important issue to keep the color tone of the toner stable. However, when the polyolefin-coated carrier to which the conductive fine particles are added is applied to the color image forming method, the fine particles contained in the carrier-coating resin are released,
The phenomenon of adhesion to toner occurs. As a result, there arises a problem that the color tone of the output color image is changed.
Since this problem cannot be detected when the polyolefin-coated carrier to which the conductive fine particles are added is used as the carrier for the monochrome toner, it has not been regarded as a problem by the conventionally known art.

As described above, when a polyolefin-coated carrier is used in a color image forming method, satisfactory performances in terms of developability and color reproducibility have not been obtained at present.

[0008]

SUMMARY OF THE INVENTION The present invention provides a stable developability and a color reproducible image for a long period of time without impairing the color reproducibility when a polyolefin resin-coated carrier is used as a carrier for a color developer. It is an object of the present invention to provide a color image forming developer and a color image forming method which can be held by the method.

[0009]

[Means for Solving the Problems]

(1) The color image forming developer of the present invention which achieves the above object is a developer comprising a color toner comprising a binder resin and a colorant and a carrier, wherein the carrier has a whiteness of 0.2 or less. It is a polyolefin-coated carrier containing fine particles having a number average primary particle diameter of 0.5 μm or less (claim 1).

(2) Further, in the color image forming method of the present invention which achieves the above-mentioned object, (a) after developing the electrostatic latent image formed on the photoconductor with the first developer, A color image is formed on the photoconductor by repeating the step of forming the second electrostatic latent image on the surface and developing with the second developer two or more times, and then the image is transferred to the transfer body all at once. In an image forming method for forming a color image on a body, the developer comprises a color toner composed of a binder resin and a colorant, and a resin coating layer having a whiteness of 0.2.
It is characterized by comprising a polyolefin-coated carrier containing fine particles having the following number average primary particle diameter of 0.5 μm or less (claim 3).

(B) In the image forming method of forming a color image on a transfer member by repeating the step of developing the electrostatic latent image formed on the photosensitive member with a developer and then transferring the latent image to the transfer member. A color toner comprising a binder resin and a colorant, and a polyolefin-coated carrier containing fine particles having a whiteness of 0.2 or less and a number average primary particle diameter of 0.5 μm or less in a resin coating layer. (Claim 4).

(C) The electrostatic latent image formed on the photoreceptor is developed with a black developer containing at least a black toner and a carrier, and a chromatic color developer containing a color toner and a carrier, and then the transfer body. Black toner and color toner remaining on the photoconductor after transfer to
In an image forming method having a step of returning the recovered black toner and color toner to a black developer composed of black toner and a carrier, the carrier has a whiteness of 0.2 or less and a number average primary particle diameter of 0. A polyolefin-coated carrier containing fine particles having a size of 0.5 μm or less (claim 5).

That is, according to the present invention, when a polyolefin resin-coated carrier in which fine particles are contained in a coating resin is used as a carrier for a color developer, even if the fine particles are detached and adhered to the toner, the color reproducibility of the toner is improved. The present invention provides a color image forming developer and a color image forming method capable of maintaining stable developability and a color reproduction image for a long period of time without inhibiting the above.

The structure of the present invention will be described below.

(1) Structure of Carrier The carrier used in the present invention is obtained by coating the surface of magnetic particles with polyolefin.

As the monomer constituting the polyolefin, ethylene, propylene, 1-butene, 2-butene,
1-pentene, 2-pentene, 2-methyl-1-butene, 1-hexene, 1-heptene, 1-octene, 1-
Aliphatic hydrocarbon monomers such as nonene are preferred. Further, resins or copolymers obtained from other vinyl monomers can also be used. Polyethylene using ethylene as a monomer is preferable.

The magnetic particles used in the present invention are not particularly limited as long as they have magnetism. As an example, materials having ferromagnetism such as magnetite, ferrite, iron, nickel and cobalt can be cited. Further, the range of the volume average particle diameter of the magnetic particles is 20 to 200 μm.
m, preferably 30 to 100 μm.

The amount of polyolefin coated on the carrier of the present invention is 1.0 wt% to 20 wt% with respect to the magnetic particles,
It is preferably 2.5 wt% to 8.0 wt%. 1.0
If it is less than wt%, the effect of resin coating cannot be sufficiently exerted, resulting in poor durability. On the other hand, if it is 20 wt% or more, the film thickness becomes too thick and the fluidity of the carrier deteriorates, which causes uneven transport of the developer.

As the resin coating method for the carrier of the present invention, various generally known methods, for example, a melt coating method in which an olefin resin is dissolved in an appropriate solvent and spray-coated on the surface of magnetic particles, magnetic particles A method of adhering an olefinic resin powder to the surface of the resin and mechanically fixing it while heating it to a temperature higher than the melting point of the resin material, a surface polymerization coating method described in JP-A-60-106808, or the like. May be used.

The above-mentioned surface polymerization coating method means that a so-called polymerization catalyst such as a Ziegler-Natta catalyst is supported on the surface of the magnetic particle serving as a core, and the above-mentioned monomer is polymerized and grown from the surface to form a resin coating layer. Is the way to do it. This method can obtain a carrier having excellent adhesiveness and adhesion to the magnetic surface, and is a preferable method than other methods.

The fine particles to be contained in the carrier-coated resin of the present invention are preferably those having a whiteness of 0.2 or less, particularly preferably 0.15 or less.

Here, the whiteness of the fine particles is measured as follows. First, a double-sided tape is attached to a support such as paper, and the fine particles are uniformly attached to the surface. Then, the relative reflection density of the portion to which the fine particles are attached is defined as the whiteness of the fine particles with respect to the reflection density of the portion to which the fine particles are not attached. The reflection density can be measured with a reflection densitometer RD-918 (manufactured by Macbeth Co.).

The fine particles to be contained in the carrier-coated resin of the present invention have a volume resistivity of 1 × 10 ² -1.
Conductive fine particles in the range of × 10 ¹¹ Ωcm are preferable.
Specific examples of the fine particles include, for example, polyacetylene-based resin fine particles, zinc oxide fine particles, tin oxide fine particles, titanium oxide fine particles, and IT which is a complex oxide of indium and tin.
Examples include O-based fine particles.

Here, the volume resistivity of the fine particles is measured as follows. An appropriate amount of fine particles is filled in an insulating cylindrical container having a cross-sectional area of 1.0 cm ² , the filling height of the fine particles is determined under a load of 500 g, and then an electric field of DC500V is applied to measure the current value. From the obtained sample filling height and current value,
The volume resistivity value was calculated by the following formula 1.

[0025]

[Equation 1]

The method of adding fine particles to be added to the carrier-coated resin of the present invention is not particularly limited, and an appropriate method may be selected depending on the resin coating method. For example,
In the case of the melt coating method, the fine particles are dispersed and mixed in the resin solution, in the case of the mechanical immobilization method, the resin fine particles and the fine particles to be added are mixed, and in the case of the polymerization coating method, the polymerization is performed during the polymerization reaction. It is possible to use a method such as adding fine particles to the tank. Also, after coating the carrier resin,
A method of mechanically driving the necessary fine particles into the carrier coating layer can also be used.

The amount of the fine particles added to the present invention is appropriately adjusted depending on the intended carrier performance and the type of the fine particles or magnetic particles used, but in many cases, it is 0. It is 1 to 25 wt%, preferably 0.5 to 20 wt%.

The volume resistivity of the carrier is in the range of 1 × 10 ⁸ to 1 × 10 ¹⁴ Ωcm, preferably 5 ×.
It is 10 ^{9 to} 5 × 10 ¹³ . The measurement of the volume resistivity of the carrier is the same as the method for measuring the volume resistivity of the fine particles added to the carrier coating resin described above.

(2) Constitution of Toner As the developing toner mixed with the carrier of the present invention,
Black toner and chromatic toner are used.

The toner contains a binder resin, a colorant, and other additives used as necessary, and the volume average particle diameter of the toner is 1 to 30 μm, preferably 5 to 20 μm.
m. The binder resin that constitutes the toner is not particularly limited, and various conventionally known resins can be used. For example,
Examples thereof include styrene resin, acrylic resin, styrene / acrylic resin, polyester resin and the like.

The colorant constituting the toner is not particularly limited, and various conventionally known materials can be used. For example, as the colorant that can be used for the black toner, materials such as carbon black and magnetite can be used. As carbon black, channel black, furnace black, acetylene black,
Thermal black, lamp black, etc. are used.
Further, so-called granular carbon black obtained by aggregating these carbon blacks can also be preferably used.

As the colorant that can be used in the chromatic toner, either a dye or a pigment can be used.

Examples of the dye include C.I. I. Solvent Red 1, 49, 52, 58, 63, 11
1, 122, C.I. I. Solvent Yellow 19, 4
4, ibid 77, ibid 79, ibid 81, ibid 82, ibid 93, ibid 9
8, the same 103, the same 104, the same 112, the same 162, C.I.
I. Solvent Blue 25, 36, 60, 70,
No. 93, No. 95, etc. can be used, and a plurality of these may be used in combination.

Examples of the pigment include C.I. I. Pigment Red 5, Same 48: 1, Same 53: 1, Same 57: 1, Same 1
22, ibid 139, ibid 144, ibid 149, ibid 166, ibid 1
77, ibid. 178, ibid. 222, C.I. I. Pigment Orange 31, 43 and C.I. I. Pigment Yellow 14, the same 17, the same 93, the same 94, the same 138, C.I. I. Pigment Green 7, C.I. I. Pigment Blue 15: 3, 6
0 or the like can be used, and a plurality of these may be used in combination. Moreover, you may use a dye together.

Other additives include, for example, salicylic acid derivatives, azo metal complexes, charge control agents such as quaternary ammonium salts, release agents such as polyolefin wax and natural wax, and magnetic fine particles.

From the viewpoint of imparting fluidity, inorganic fine particles and / or organic fine particles may be added. As the inorganic fine particles, inorganic oxide particles such as silica, titania and alumina are preferable. Further, these inorganic fine particles may be hydrophobized with a silane coupling agent, a titanium coupling agent, or the like. As the organic fine particles, fine particles made of styrene type resin, acrylic resin, silicone resin or the like can be used. In order to reduce the load of cleaning the photoconductor, a cleaning aid or
A lubricant composed of higher fatty acid or its derivative may be added to the toner.

(3) Structure of Developer The two-component developer in the present invention is prepared by mixing toner and carrier. The toner is used in a mixture of 2 to 10 wt% with respect to the entire developer.

(4) Structure of Photoreceptor The photoreceptor used in the color image forming method of the present invention is not particularly limited, and known photoreceptors can be used.

(5) Image forming method Since the developing system in which the developer of the present invention can be used is not particularly limited, it can be suitably used in either a contact developing system or a non-contact developing system.

FIG. 1 shows an example of the structure of a contact developing type developing device.
This will be described with reference to FIG. In the figure, 400 is a developing device, 401 is a developing sleeve, 402 is a cylindrical magnet body,
Reference numeral 403 is a housing provided at the toner supply port 404, 405 and 406 are stirring screws rotatably provided in the arrow direction, 407 is a supply roller, 408 is a developer layer thickness regulating member, and 10 is a photosensitive drum. . DC power supply 4
10 and the AC power supply 411 are power supplies as developing bias applying means for forming an alternating bias electric field.

The contact developing system is a system in which the electrostatic latent image formed on the photoconductor drum 10 is contacted with and rubbed with a developer to develop the latent image. Therefore, the developer layer formed on the developing sleeve 401 in the developing area is not covered by the photosensitive drum 1.
Contact with 0 is required. Specifically, the layer thickness of the developer in the developing area is 0.2 to 8.0 mm, and particularly, the layer thickness of
It is preferably 4 to 5.0 mm. Further, the gap between the photosensitive drum 10 and the developing sleeve 401 in the developing area is appropriately set depending on the layer thickness of the developer, and specifically, 0.1 to 7.0 mm, particularly 0.2 to 4.0 mm. Is preferred.

As the non-contact developing method, in developing the electrostatic latent image formed on the photosensitive drum 10,
The developer layer formed on the developing sleeve is the photosensitive drum 1.
This is a method of developing in a state where it does not contact 0. for that reason,
It is necessary that the developer layer formed on the developing sleeve in the developing area does not come into contact with the photosensitive drum 10. Specifically, the layer thickness of the developer in the developing area is 0.02 to
It is preferably 4.0 mm, particularly preferably 0.04 to 2.0 mm. Further, the gap between the photosensitive drum 10 and the developing sleeve 401 in the developing area is appropriately set depending on the layer thickness of the developer, but specifically, it is 0.05 to 5.0 mm, particularly 0.1 to 3.0 mm. Is preferred.

In both the contact development system and the non-contact development system, it is necessary to regulate the developer layer thickness to the required thickness. The method is not particularly limited in the present invention, and a known method can be used. Specifically, for example, a magnetic blade method using magnetic force, a method of pressing a developer layer regulating rod against the surface of the developing sleeve, or a developer layer by contacting a urethane blade or a phosphor bronze plate with the surface of the developing sleeve. There is a method to regulate. Further, a rigid blade system or the like can be used in which a rigid member is provided with a certain gap from the developer sleeve and the amount of the developer is regulated by allowing the developer to pass through the gap.

As the developer carrying member, one having a known structure can be used. Preferably, a cylindrical developing sleeve having a diameter of 10 to 80 mm and a plurality of magnets in a cylindrical shape are provided in the developing sleeve, and the developer is carried by utilizing magnetic force.
It is better to use a transport system. The developer carrying method by the developer carrier is a method of rotating a cylindrical developing sleeve,
Either a method of rotating the internal magnet or a method of rotating both of them in the same direction or in the opposite direction can be used.

In developing, a developing bias voltage may be applied between the photosensitive drum and the developer carrying member. In that case, either a method of applying only a DC bias voltage or an AC bias voltage may be used, or a method of applying both DC and AC bias voltages together may be used. here,
The AC bias voltage for forming the alternating electric field preferably has a frequency of 1 to 10000 Hz and a voltage of 1 to 3000 Vp-p. The DC bias voltage is 200 to 1000.
V is preferred.

A structural example of the non-contact developing system will be described with reference to FIG.

FIG. 1B is a sectional view showing an example of a non-contact developing type developing device which can be suitably used in the image forming method of the present invention. In the figure, 41 is a developing sleeve and 42
Is a magnet body fixed inside, and 41 and 42 constitute a developer carrying body. 43 is a supply roller which is a developer supply member, 44 is a developer layer thickness regulating member (hereinafter, simply referred to as a regulating member), 45 is a scraper which scrapes the developer from the developer carrying member, and 46A and 46B are A stirring screw which is a developer stirring member, 47 is a casing of the developing device, D is a two-component developer composed of the carrier and toner of the present invention, and a DC power source 48 and an AC power source 49 are each a developing bias application that forms an alternating bias electric field. A power source 10 as a means is a photosensitive drum which is an electrostatic charge image carrier having a photosensitive layer 12 formed on a conductive substrate 11. Also,
The arrows in the figure indicate the photosensitive drum 10 and the developing sleeve 4.
The rotation direction of 1 is shown. The developing sleeve 41 is a cylinder made of a non-magnetic and conductive metal such as aluminum or stainless steel, and in order to stably convey the developer,
Roughening treatment such as thermal spraying treatment, sand blasting treatment and grooving treatment is added to the surface. The developer carrier 41
The magnetic field on the surface of the developing sleeve 41 is 500 to
A cylindrical magnet body 42 having a plurality of magnetic poles magnetized to have N poles or S poles so as to be 1200 [Gauss] is fixedly installed, and the developing sleeve 41 has a magnet body 42.
It is rotatable with respect to.

The casing 47 is made of resin such as acrylic, polycarbonate, ABS, or aluminum,
Made of metallic material such as stainless steel. When a resin material is used, the casing 47 may be provided with conductivity by introducing a conductive filler such as carbon black or by subjecting the surface to a conductive treatment, if necessary. Inside the casing 47, a developer carrying member including a magnet body 42 and a developing sleeve 41, a supply roller 43, a scraper 45, and stirring screws 46A and 46B are arranged, and inside the casing 47, a regulating member 44 is arranged. There is.

A two-component developer D consisting of toner and carrier is stored inside the casing 47. The two-component developer D is agitated and mixed by agitating screws 46A and 46B, and is supplied onto a developer bearing member by a supply roller 43, and the magnetic force of the magnet member 42 causes a magnetic brush (hereinafter referred to as a developer layer) on the developing sleeve 41. And B) is formed. The developer layer B is restricted by the regulating member 4 as the developing sleeve 41 rotates.
4 is conveyed while the developer layer thickness is regulated by 4 to form a toner image on the photoconductor 10 in the development area A. At the time of this development, the developer layer B is regulated by the regulation member 44 so as not to come into contact with the photoconductor 10.

In the case of applying to the color image forming system of the present invention, a system in which a monochrome image is formed on the photoconductor 10 and sequentially transferred to the image support (this system is referred to as a sequential transfer system, as shown in FIG.
(Shown in (A)), or a single color image is developed a plurality of times on the photoconductor 10 to form a color image, and then the recording paper P is collectively printed.
Method of transferring to (Batch transfer method, as shown in FIG.
Can be used.

An image forming method by the image forming apparatus of the sequential transfer method shown in FIG. 2A will be described. A band electrode 20 for providing electric charges on the surface of the photoconductor 10 by corona discharge in the vicinity of the peripheral surface of the photoconductor 10 having a photosensitive layer for forming an electrostatic latent image on a conductive substrate, and a monochromatic developer is stored. A developing device 40 in which a plurality of the developing devices are arranged, and a cleaning device 90 for cleaning the toner remaining on the photoconductor 10 are arranged. On the other hand, on the transfer drum 1 side including the conductive substrate, the conductive elastic layer and the insulating layer, the transfer paper P is transferred to the transfer drum 1.
The transfer unit 2 for supplying the transfer paper P is transferred to the transfer unit in which the transfer pole 4 is arranged, and the toner image on the photoconductor 10 developed with toner of different color is transferred. Transferring onto the paper P, repeating this several times to form a multicolor image on the surface of the transfer paper P, transferring this transfer paper P to the peeling section, and using the peeling pole 6 the transfer drum 1
, The transfer paper P is separated from the transfer drum 1 and discharged. A multicolor image is formed by fixing the transfer paper P with a melt pressure type fixing device.

An image forming method by the batch transfer type image forming apparatus shown in FIG. 2B will be described. In this image forming method, transfer of each color to the transfer drum is not performed, but multicolor toner images are superposed on the photoconductor 10 and finally transferred onto the transfer paper P at one time. This is the same as the above-mentioned sequential transfer method. FIG. 3 is a block diagram of a batch transfer type color image forming apparatus showing an example of the image forming apparatus of the present invention.

In the figure, 10 is a photoconductor which is an electrostatic latent image bearing member, 20 is a scorotron band electrode which is a charging means,
Reference numeral 25 is an image reading unit, 30 is an image writing unit using a laser beam as an exposure unit, 40A, 40B, 40.
C and 40D are developing devices (collectively referred to as "40") shown in FIG. 1 that contain two-component developers of different colors, 60 is a paper feed unit including a first paper feed roller 61 and a second paper feed roller 62, 70 is a corona discharge electrode for transfer which is a transfer means, and 7
Denoted at 5 is a corona discharge electrode for separation, which is a means for separating the transfer material,
Is a conveyance unit, 85 is a fixing unit, 90 is a cleaning device equipped with a cleaning blade 91, and 95 is a discharge lamp for discharging static charges on the photoconductor before charging. The arrow in the figure indicates the rotation direction of the photoconductor 10.

In the basic operation of the color image forming apparatus according to this embodiment, first, a copy start command is sent from an operation unit (not shown) to a control unit (not shown), and the photoconductor 10 starts rotating. As the photoconductor 10 rotates, its peripheral surface is uniformly charged by the scorotron band electrode 20. Further, in the image reading section 25, the light information from the document is converted into an electric signal,
After the electric signal is subjected to image processing, a laser beam is irradiated by the image writing unit 30 to form an electrostatic latent image on the photoconductor 10. The electrostatic latent image on the photoconductor 10 is developed by any of the developing devices 40A to 40D, and a toner image is formed on the photoconductor 10.

The photoconductor 10 on which the toner image is formed is
It is uniformly charged again by the scorotron band electrode 20 and is irradiated with a laser beam by the image writing unit 30 to form the next electrostatic latent image. The electrostatic latent image on the photoconductor 10 is developed by any of the developing devices 40A to 40D, and toner images of different colors are superposed on the photoconductor 10.

In this example, the latent image forming step and the developing step as described above are repeated four times, and toner images of four colors are superposed on the photoconductor 10.

A recording sheet, which is a transfer material, is stored in the sheet feeding section 60, and is transferred in synchronization with the toner image superposed on the photoconductor 10 by the first sheet feeding roller 61 and the second sheet feeding roller 62. The corona discharge electrode 70 is sent to the transfer unit. The toner images superposed on the photoconductor 10 are transferred onto the recording paper by the transfer corona discharge electrode 70, and the recording paper is separated from the photoconductor 10 by the separation corona discharge electrode 75. The recording paper on which the toner image has been transferred is conveyed to the fixing portion 85 via the conveying portion 80, melted and pressure-fixed, and then discharged to the outside of the apparatus.

On the other hand, the toner remaining on the photoconductor 10 without being transferred onto the recording paper is scraped off by a cleaning device 90 equipped with a cleaning blade 91 which is pressure-bonded onto the photoconductor 10 at a timing, and before charging. After the residual charges are removed by the static elimination lamp 95 that eliminates the static charges on the photoconductor, the next image forming process is started.

The toner image formed on the photoconductor 10 by the various methods described above is transferred to a transfer material such as paper in a transfer process. The transfer method is not particularly limited, and various known methods such as so-called corona transfer method and roller transfer method can be applied.

In the present invention, the mechanism for cleaning the photosensitive member is not particularly limited, and a known cleaning mechanism such as a blade cleaning system, a magnetic brush cleaning system, a fur brush cleaning system or the like can be arbitrarily used. As these cleaning mechanism,
A suitable one is a blade cleaning method using a so-called cleaning blade. Here, as the configuration of the blade cleaning method, any of the configurations described in FIGS. 4A and 4B can be used. FIG.
In (A) and (B), the holder 3 holds the cleaning blade 91. The angle formed by the cleaning blade 91 and the photoconductor 10 is 10 to 90 in the contact angles θ ₁ and θ ₂ shown in the figure both in the trail system shown in FIG. 4A and in the counter system shown in FIG. 4B. And preferably 15 to 75 °. Cleaning blade 9
An elastic body such as silicone rubber or urethane rubber can be used as a material for forming 1 itself. In this case, it is preferable that the rubber hardness is 30 to 90 °. The thickness is 0.
5 to 5.0 mm, the length outside the holder 92 is 3 to 20 m
m is good. The pressure contact force with respect to the photoconductor 10 is 1 to 50 gf /
mm is preferred.

Further, it is possible to use a system in which a plurality of types of toner remaining untransferred on the photoconductor 10 are collected, introduced into a black developer, and reused. In this case, a mechanism for returning the toner collected from the photoconductor 10 by the above-mentioned cleaning mechanism to the black developing device or the black toner replenishing section may be used.

[0062]

EXAMPLES The present invention will be described below with reference to specific examples and comparative examples.

<< Production of developing toner >> 100 parts by weight of polyester resin (Tg = 55 ° C.), 10 parts by weight of carbon black (Mogal L; made by Cabot), natural wax (purified carnauba wax No. 1; made by Noda Wax) )
3 parts by weight were mixed and kneaded, and then pulverized and classified to obtain colored particles having an average particle size of 7.5 μm. This was designated as "colored particle 1".

A yellow pigment (C.I.
g. YELLOW 17) was used in the same manufacturing method as that of the colored particles 1 except that YELLOW 17) was used, and "Magenta pigment (CI Pig. RED122) was used in the same manner as" colored particles 3 ". Cyan pigment (C.I.Pi
g. The one using Blue 15: 3) is "colored particle 4".
And

Further, 0.9 wt% of hydrophobic silica was added to and mixed with each of these colored particles 1 to 4 to obtain a toner. These are designated as "toner 1" to "toner 4".

<< Production of Carrier >> 500 ml of dehydrated n-hexane and 450 g of magnetic particles dried under reduced pressure (ferrite having a volume average particle diameter of 60 μm) were placed in an autoclave and stirred. Next, 2.0 mmol of Ziegler-Natta catalyst was added and stirred to support the catalyst on the surface of the magnetic particles. Further, the particles shown in Table 1 below, which had been dried under reduced pressure in advance, were added, and then heated to 90 ° C. Then, the total pressure was 6.0 kg in dehydrated n-hexane in which the fine particles were dispersed.
Ethylene gas was continuously supplied so as to be / cm ² G. The polymerization reaction is carried out for 45 minutes while stirring, and ethylene is polymerized and grown on the surface of the magnetic particles, whereby the fine particles are mechanically incorporated into the polyethylene-coated resin. Thus, the polyethylene-coated carrier of the present invention and the comparative polyethylene-coated carrier in which the fine particles were dispersed in the coating resin were obtained. In the table, the composition of fine particles indicates the dopant element in parentheses.

[0067]

[Table 1]

<< Preparation of Developer >> [Toner 1] to [Comparative Carrier 1] to [Comparative Carrier 1] to [Comparative Carrier 3] described above, respectively. Toner 4 ”was added in the combination shown in Table 2 below, and then mixed for 20 minutes using a V-type mixer,
A developer having a toner concentration of 7% was prepared.

As shown in the table below, the developers are "inventive developer 1a" to "inventive developer 1d", "inventive developer 2a" to "inventive developer 2d", "inventive development". Agent 3
a "-invention developer 3d", "invention developer 4a"-
"Inventive Developer 4d" and "Comparative Developer 5a"-
Examples 1 to 4 in combination with "Comparative developer 5d", "Comparative developer 6a" to "Comparative developer 6d", "Comparative developer 7a" to "Comparative developer 7d", and Used for Comparative Examples 1-3.

[0070]

[Table 2]

<Image formation> The developer obtained above was subjected to image formation by a sequential transfer system and a batch transfer system.

(A) Sequential Transfer Method As an evaluation apparatus using the sequential transfer method, the one having the same structure as that shown in FIG. 2A was used.

The contact developing method was used as the developing method, and the conditions were as shown below.

Maximum surface potential of photoconductor = −550V Minimum surface potential of photoconductor = −50V DC bias of development = −450V Gap between photoconductor and developer carrier = 0.5 mm Developer layer thickness control system = Rigid blade system Development Area developer layer thickness = 3.0 mm Development sleeve roughening treatment = Sandblast treatment Development sleeve outer diameter = 20 mm Further, as the developing device, a developing device having the same structure as that shown in FIG. 1B is used, A laminated organic photoconductor was used as the photoconductor. The photoreceptor was charged negatively, the exposure was carried out by a semiconductor laser according to the image, and the development was carried out by the reversal development system. Furthermore, a method was adopted in which the toner collected by the cleaning mechanism without being transferred to the transfer material from the photoconductor is collected, introduced into the black developing device, and reused.

In image formation, a toner image formed on the photosensitive drum 10 is successively transferred for each color onto the transfer material on the transfer drum 1 to form a multicolor image on the transfer material. A multi-color image was formed by fixing the transfer material with a melt pressure type fixing device.

(B) Batch Transfer Method As the evaluation apparatus using the batch transfer method, the one having the same structure as that shown in FIG. 2B was used.

The non-contact developing method is used as the developing method.
The conditions are as shown below.

Maximum surface potential of photoconductor = −550V Minimum surface potential of photoconductor = −50V DC bias = −250V AC bias = V _PP : −50 to −
450 V Alternating electric field frequency = 1800 Hz Gap between photoconductor and developer carrier = 300 μm Developer layer thickness control method = Layer control rod pressing method Layer control rod pressing force = 10 gf / mm Layer control rod material = SUS416 Outside layer control rod Diameter = 3 mm Developer layer thickness in development area = 150 μm Development sleeve surface roughening treatment = Sandblast treatment Development sleeve outer diameter = 20 mm Further, as the developing device, the same constitution as shown in FIG. 1 (A) is used. A laminated organic photoconductor was used as the photoconductor drum. Further, the charging of the photoconductor drum 10 is negative charging, the exposure is performed by a semiconductor laser according to the image, and the development is performed by the reversal development method performed on the exposed portion. Furthermore, a method was adopted in which the toner collected by the cleaning mechanism without being transferred onto the transfer material from the photosensitive drum is introduced into the black developing device and reused.

The image formation is the same as the above-mentioned sequential transfer system except that a plurality of types of toner are superposed on the photosensitive drum 10 and finally transferred once onto the transfer material.

As a cleaning mechanism for the photosensitive drum, either a sequential transfer system or a batch transfer system can be used.
The same structure as described in (A) was used. The cleaning conditions were set as shown below.

Angle formed by the holder and the photoconductor drum θ ₁ = 22 ° Cleaning blade = Urethane rubber (rubber hardness 65 °) Cleaning blade thickness = 2 mm Cleaning blade length outside the holder = 8 mm Pressure contact force to the photoconductor drum = 15 gf / mm << Performance Evaluation >> The prepared developer was put into an evaluation machine of a sequential transfer system or a batch transfer system under the above conditions, and A3 with a pixel ratio of 20% was used in a normal temperature and normal humidity environment (20 ° C./55% RH). 10,000 manuscripts were output. Therefore, the output image was sampled at the initial stage and every time 1000 sheets were output, and changes in chromaticity (color difference) and changes in image density of all 11 images were evaluated.

<Chromaticity> The chromaticity change (color difference) is yellow,
Color difference meter for each color of magenta and cyan (color eye 700
0; manufactured by Macbeth Co.) and evaluated by the maximum value of the color difference ΔE of the output image with respect to the initial image in the L ^* a ^* b ^* color space. The color difference ΔE is defined by the following equation, and the maximum value of the color difference ΔE of 3.0 or less was judged to be good.

Color difference ΔE = [(ΔL ^* ) ² + (Δa ^* ) ² + (Δb ^* ) ² ] ^1/2 (Equation 2) <Developability> The change in developability is based on the pixel ratio of 100%. The density of the image area was measured and evaluated based on the difference between the density of the output image on the first and 10,000th sheets. For the density measurement, Color Eye 7000 (manufactured by Macbeth Co.) was used, and those having an image density difference of 0.05 or less were judged to be good.

Table 3 below shows the results of these evaluations.

[0085]

[Table 3]

[0086]

EFFECT OF THE INVENTION The color image forming developer of the present invention does not impair color reproducibility when a carrier coated with a polyolefin resin is used as a carrier for a color developer.
A stable developability and a color image can be retained for a long period of time (claims 1 and 2). Further, the developer is effectively applied to a color image forming apparatus of a batch transfer system or a color image forming apparatus of a sequential transfer system to form a high quality color image (claims 3 and 4). Further, the electrostatic latent image formed on the photoconductor is developed with a black developer including at least a black toner and a carrier and a chromatic color developer including a chromatic color toner and a carrier, and transferred to a transfer body, and then the photoconductor. A method for forming a color image, comprising the step of returning the black toner and the color toner recovered after cleaning the black toner and the color toner remaining on the top to a black developer composed of a black toner and a carrier. By applying, there is no change in the hue and the image density on the image, and the developer can be recycled (claim 5).

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a contact type or non-contact type developing device according to the present invention.

FIG. 2 is a configuration diagram of a sequential transfer type image forming apparatus and a batch transfer type image forming apparatus.

FIG. 3 is a configuration diagram of a batch transfer type color image forming apparatus.

FIG. 4 is an explanatory diagram of a blade cleaning method.

[Explanation of symbols]

10 Photoreceptor Drum (Image Forming Body) 20 Scorotron Charger 30 Image Writing Section 40, 40A, 40B, 40C, 40D, 400 Developing Device 41 Developing Sleeve (Developer Conveying Body) 42 Magnet 43 Supply Roller 44 Developer Layer Thickness Regulation member (regulation member) 45 Scraper 46A, 46B Stirring screw 47 Casing 48, 49 Power source 90 Cleaning device A Development area D Two-component developer

Claims (6)

[Claims] 1. A developer comprising a color toner comprising a binder resin and a colorant and a carrier, wherein the carrier has a whiteness of 0.2 or less in a resin coating layer and a number average primary particle diameter of 0. A developer for color image formation, which is a polyolefin-coated carrier containing fine particles of 5 μm or less. 2. The fine particles contained in the resin coating layer of the carrier are conductive fine particles having a volume resistivity of 1 × 10 ² to 1 × 10 ¹¹ Ωcm.
The developer for forming a color image according to item 1. 3. A first electrostatic latent image formed on a photoconductor is formed.
After the development with the developer, the step of forming the second electrostatic latent image on the photoconductor and developing with the second developer is repeated twice or more to form a color image on the photoconductor. In an image forming method of forming a color image on a transfer body by transferring the toner to the transfer body at once, the developer includes a color toner composed of a binder resin and a colorant, and a whiteness of 0 in a resin coating layer. And a polyolefin-coated carrier containing fine particles having a number average primary particle diameter of 0.5 μm or less. 4. An image forming method for forming a color image on a transfer member by repeating a step of developing an electrostatic latent image formed on a photosensitive member with a developer and then transferring the latent image to the transfer member. Is composed of a color toner composed of a binder resin and a colorant, and a polyolefin-coated carrier containing fine particles having a whiteness of 0.2 or less and a number average primary particle diameter of 0.5 μm or less in a resin coating layer. A color image forming method characterized by the above. 5. An electrostatic latent image formed on a photoconductor is developed with a black developer containing at least a black toner and a carrier, and a chromatic color developer containing a color toner and a carrier, and then transferred to a transfer body. An image forming method having a step of removing and recovering black toner and color toner remaining on the photoconductor after transfer, and returning the recovered black toner and color toner to a black developer composed of black toner and a carrier. A color image forming method, wherein the carrier is a polyolefin-coated carrier containing fine particles having a whiteness of 0.2 or less and a number average primary particle diameter of 0.5 μm or less. 6. The fine particles contained in the resin coating layer of the carrier are conductive fine particles having a volume resistivity of 1 × 10 ² to 1 × 10 ¹¹ Ωcm. 5. The method for forming a color image according to item 5.