JP2002351127A - Image forming method and electrophotographic developer used for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-component developer which is capable of forming images of high image quality strong to the thermal stress and mechanical stress to toners and an image forming method using this developer. SOLUTION: The toners satisfying at least one requirement of a coefficient of dynamic friction of 0.18 to 0.30, a loose apparent density of >=0.30 g/cm<3> or a coagulation degree of <=30% are used in the oilless fixed image forming method using the two-component developer consisting of toners dispersed with wax and carriers. The doctor gap of the electrophotographic image forming device is 0.3 to 0.8 mm and the developer bulk density between a photoreceptor and a developer roller is 1.5 to 2.5 g/cm<3> .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic developer and an image forming method using the developer, and more particularly, to an image forming method such as electrophotography, electrostatic recording, and electrostatic printing. The present invention relates to a two-component developer used and an image forming method using the developer and using oilless fixing.

[0002]

2. Description of the Related Art An image forming method using an electrophotographic method using a two-component developer is widely known and used in printers, copiers, facsimile machines and the like. Recently, Japanese Patent Application Laid-Open No. 60-41
No. 079, the latent image formed on the photoconductor is developed with toner, the toner image is transferred to a transfer material such as plain paper, and the toner remaining on the photoconductor drum is cleaned with a cleaner. After removal, the removed toner is often returned to the developing device for reuse. Further, as disclosed in Japanese Patent Application Laid-Open No. 7-199538, as a toner capable of forming good image quality for a long time with little toner deterioration even in a low-temperature fixing recycling system, an additive for increasing a charge amount is used. There have been proposed toners containing a fluidity improver containing two kinds of additives, such as a reducing agent, and carnauba wax as a release agent.

[0003]

Recently, however, many copy machines have a printer function, and the output of only one copy or print is increased. Stirring time is increasing. In the developing device, the stirring of the developer greatly affects the deterioration of the developer. The developer is pumped up by the developing roller, and the carrier and the toner are rubbed at the doctor portion. As a result, the toner component locally adheres to the carrier due to the temperature rise due to the friction of the developer and the mechanical stress.
In addition, wax is dispersed in the oilless toner in order to ensure the fixing releasability. When a thermal stress is applied to the developer, the wax bleeds out to the toner surface and the toner particle surface becomes excessive in the wax, so that the adhesion of the wax to the carrier surface is promoted. When the toner has a negative polarity, the wax having the same polarity deactivates the charging function of the carrier surface, and as a result, the charge amount of the developer decreases. Further, as an image density control method, a method of controlling the image density by controlling the toner density by optically detecting the density of the toner adhered on the photoreceptor is used. As a result, when the charge amount of the developer decreases, the developing γ characteristic rises and the saturated image density decreases. As a result, problems such as a decrease in image density and poor sharpness occur, and problems such as a need to replace the developer occur.

In particular, recently, high image quality has been demanded.
Means for achieving this is to reduce the toner particle size,
It can be achieved by including more fine particles. However, when the toner particle size is small, the wax easily bleeds out to the surface of the toner particles, and the deterioration of the developer is further promoted by the increase in the total surface area of the toner particles.

The present invention has been made in view of the above-mentioned prior art, and provides a two-component developer which is resistant to thermal stress and mechanical stress on a toner and can obtain a stable image, and an image forming method using the developer. The purpose is to:

[0006]

According to a first aspect of the present invention, there is provided an oilless fixed image forming method using a two-component developer comprising a toner and a carrier.
A toner satisfying at least one of 0.30, a loose apparent density of 0.30 g / cm ³ or more, and a cohesion degree of 30% or less is used, and the doctor gap of the electrophotographic image forming apparatus is 0.3 to 0. 0.8 mm, and the bulk density of the developer between the photoconductor and the developing roller is 1.5 to 2.5 g / cm.
^3. An image forming method using oilless fixing.

A second aspect of the present invention is that the dynamic friction coefficient is 0.18 to
A two-component developer comprising a toner and a carrier satisfying at least one requirement of 0.30, a loose apparent density of 0.30 g / cm ³ or more, or a cohesion degree of 30% or less, and an electrophotographic image forming apparatus. Used in an image forming method using oil-less fixing in which the doctor gap is 0.3 to 0.8 mm and the bulk density of the developer between the photoreceptor and the developing roller is 1.5 to 2.5 g / cm ^3. And a developer for electrophotography.

The toner of the electrophotographic developer of the present invention has a dynamic friction coefficient of 0.18 to 0.30, a loose apparent density of 0.30 g / cm ³ or more, or a cohesion degree of 30% or less,
If at least one of the requirements is satisfied, low-temperature fixing can be achieved, and high image quality and long life can be achieved at the same time. However, it is preferable to satisfy the two or more requirements.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The toner loose apparent density is an index of toner fluidity, and the larger the value, the better the fluidity of the toner and developer. Here, the above-mentioned development conditions enabling high image quality, that is, the doctor gap of the electrophotographic image forming apparatus is 0.3 to 0.8 mm, and the developer bulk density between the photosensitive member and the developing roller is 1.5 to Under the development condition of 2.5 g / cm ³ , the stress applied to the developer during development becomes large. Therefore, when a toner having poor fluidity is used, the stress applied between the toner and the photoconductor and the carrier becomes stronger. As a result, the components of the toner are likely to locally adhere to the carrier (hereinafter referred to as spent on the carrier or spent on the carrier). Further, when the fluidity further decreases due to the desorption or burying of the additives on the surface of the toner particles, the toner remaining in the developing device as an undeveloped part and the toner returning to the developing device as recycled toner are more spent on the carrier. Is more likely to occur.

When the loose apparent density is less than 0.30,
In the above development process, fluidity is poor and carrier spent tends to occur. Therefore, the loose apparent density is 0.30 or more, preferably 0.30 to 0.40.
The apparent density of loose toner is measured using a powder tester (PTN type:
(Manufactured by Hosokawa Micron Corporation).

When the degree of toner aggregation is 30% or more, the fluidity of the developer deteriorates and the developer is easily subjected to development stress.
When strong developing stress is continuously received, the amount of wax on the toner surface increases, and carrier spent occurs. In particular, under the above-described development conditions that enable high image quality, the stress applied to the developer during development increases. Therefore, the cohesion degree is 30%
When the toner having poor fluidity is used as described above, the stress applied between the toner and the photosensitive member and the carrier becomes stronger. As a result, the components of the toner easily adhere to the carrier locally. Further, when the fluidity further decreases due to the desorption or burying of the additives on the surface of the toner particles, the toner remaining in the developing device as an undeveloped part and the toner returning to the developing device as recycled toner are more spent on the carrier. Is more likely to occur.

Therefore, the degree of agglomeration is 30% or less, preferably 10 to 30%. The toner aggregation degree is measured using a powder tester (PTN type: manufactured by Hosokawa Micron Corporation). The screens used were 75 μm, 45 μm, and 22 μm, and the values were obtained when vibration was performed at an amplitude of 1.0 mm for 30 seconds.

The properties of a toner containing a wax vary greatly depending on the state of dispersion of the wax. When the wax has a small particle size and is uniformly dispersed, the ratio of the amount of the wax present on the toner surface becomes equal to the amount of the included wax. However, when the toner has a large particle size, the ratio of the amount of wax present on the toner surface becomes larger than the amount of wax contained therein. The cause is that when the kneaded toner is pulverized and atomized, it is often pulverized by an external force such as a mechanical impact or an impact by a jet stream, and in that case, destruction occurs from the weakest portion inside. Since this is wax, if the wax has a large particle size, the amount of wax on the toner surface increases, and in such a toner, the dynamic friction coefficient, the loose apparent density decreases, and the degree of aggregation increases.

When the dynamic friction coefficient is 0.18 or less, the amount of wax on the toner surface is large. In addition, when the internal temperature rises, the amount of wax on the toner surface further increases, and carrier spent occurs. Also, the fluidity of the toner deteriorates.
When the coefficient of kinetic friction is 0.30 or more, the amount of wax on the toner surface is small. Although this is advantageous for an increase in the internal temperature, hot offset occurs during fixing.

The dynamic friction coefficient of the toner surface is 3 g in mass.
The toner was subjected to a load of 6 t / cm ² and formed into a disc-shaped pellet having a diameter of 40 mm, and was measured using a fully automatic friction and wear analyzer manufactured by Kyowa Interface Science Co., Ltd. At this time, a 3 mm stainless ball point contact is used as the contact.

When the circularity of the toner is low, the contact area between the carrier and the toner increases, so that the amount of spent on the carrier increases during the same development time. Accordingly, the toner of the present invention has an average circularity of 0.94 or more, and preferably has a circularity of 0.94 or more.
95 to 0.98. When the average circularity is less than 0.94, the toner particles become indefinite and the contact area with the carrier increases. As a result, the spent on the carrier of the wax on the toner surface increases, and the deterioration of the developer is accelerated.

The average circularity can be measured using a flow type particle image analyzer FPIA-2100 manufactured by SYSMEX. The measurement was made to a 1% NaCl aqueous solution using primary sodium chloride and then 0.45 μm
0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 50 to 100 ml of the liquid having passed through the filter, and 1 to 10 mg of a sample is added. This is subjected to a 1 minute dispersion treatment with an ultrasonic disperser,
The measurement was performed using a dispersion liquid in which the particle concentration was adjusted to 5000 to 15000 particles / μl. The diameter of a circle having the same area as the two-dimensional image area picked up by the CCD camera is defined as a circle equivalent diameter, and a circle equivalent diameter of 0.6 μm or more is effective from the accuracy of the CCD pixel and used for calculating the average circularity. . The average circularity can be obtained by calculating the circularity of each particle, adding up the circularity of each particle, and dividing by the total number of particles. The average circularity of each particle can be calculated by dividing the perimeter of a circle having the same projected area as the particle image by the perimeter of the projected particle image.

The toner having an average circularity of 0.94 or more can be produced by a method such as pulverization by mechanical impact or a method by heat treatment.

Further, the toner of the present invention preferably has a volume average particle size of 5 to 10 μm in order to improve the image quality.
When the volume average particle size is 5 μm or less, the fluidity of the toner deteriorates, and when the developing stress is applied for a long period of time, the fluidity of the toner further deteriorates, making it difficult to uniform the toner composition and causing toner scattering. When the volume average particle diameter is 10 μm or more, it is strong against heat history (development stress) but has little effect of improving image quality.

The toner of the present invention has a volume average particle size of 5
It is preferred that those having a size of not more than μm are 60 to 80% by number. When 5 μm or less is 60% by number or less, it is strong against development stress and recycling process, but has little effect on improving image quality. If the particle size is 5 μm or less and the number is 80% or more, the fluidity of the toner is remarkably deteriorated, and if the developing stress is applied over a long period of time, the fluidity of the toner is further deteriorated, causing problems such as toner scattering.

[0021] The volume average particle size of the electrolyte solution is 100 to
0.1 to 5 ml of a surfactant (alkylbenzenesulfonate) is added to 150 ml, and the measurement sample is added to the mixture in 2 to 2 ml.
Add 0 mg. An electrolytic solution in which a sample is suspended is subjected to a dispersion treatment by an ultrasonic disperser for 1 to 3 minutes, and a particle size distribution or the like of 2 to 40 μm is measured based on the volume using a 100 μm aperture by the Coulter Counter IIe described above. And

In recent years, the particle size of the toner and carrier has been reduced for the purpose of improving the image quality, and particularly under the above-mentioned developing conditions, the hazard that the developer mechanically receives becomes large. When toner having a particle size is used, spent on the carrier surface is promoted. Further, if the amount of wax on the toner surface is simply reduced in order to solve the above-mentioned problem, the dynamic friction coefficient becomes too large and a fixing offset occurs. However, when carnauba wax, rice wax, or ester wax is used as the wax component in the toner, low-temperature fixability is excellent even with a small amount of wax. Therefore, it is preferable to use carnauba wax, rice wax, synthetic ester wax, and a mixture thereof as the wax component.

Carnauba wax is a natural wax obtained from the leaves of carnauba palm, and a low-acid-type wax from which free fatty acids have been eliminated is preferred because it can be uniformly dispersed in a binder resin. Rice wax is a natural wax obtained by refining crude wax produced in a dewaxing or wintering process when refining rice bran oil extracted from rice bran. Synthetic ester wax is synthesized from a monofunctional linear fatty acid and a monofunctional linear alcohol by an ester reaction.

These wax components are used alone or in combination. It is important that the wax component is added in an amount of 0.5 to 10 parts by weight and has an average particle size of 100 to 600 μm.

It is extremely desirable that the wax component is uniformly dispersed in the toner at a desired particle size. A preferable dispersion diameter is about 0.1 to 5 μm. However, the raw material wax particles often have a very wide particle size distribution. Such a toner using a wax having a very wide particle size distribution has a nonuniform wax dispersion diameter,
Although the particle size distribution will be about 0.01 to 50 μm,
In the toner of the present invention, a desired dispersion diameter could be obtained by setting the average particle diameter of the wax dispersed in the toner to 100 to 600 μm.

When the average particle diameter of the wax is 600 μm or more, the dispersion diameter in the toner becomes large, and the filming property and
Spent property and heat-resistant storage stability deteriorate. When the average particle diameter of the wax is 100 μm or less, the dispersion diameter in the toner becomes small, and the low-temperature fixing property and the offset property deteriorate.
The dispersion diameter of the wax in the toner is determined by analyzing a photographic image of the wax particles of the toner taken by a transmission scanning electron microscope using an image analyzer Luzex IIIU (manufactured by NIRECO).

As the binder resin used in the present invention, all conventionally known resins can be used. For example, styrene,
Poly-α-stillstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-
Butadiene copolymer, styrene-vinyl chloride copolymer,
Styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α
Styrene resins such as methyl chloroacrylate copolymer, styrene-acrylonitrile-acrylate copolymer (a homopolymer or copolymer containing styrene or a substituted styrene), a polyester resin, an epoxy resin,
Examples thereof include vinyl chloride resin, rosin-modified maleic resin, phenol resin, polyethylene resin, polypropylene resin, petroleum resin, polyurethane resin, ketone resin, ethylene-ethyl acrylate copolymer, xylene resin, and polyvinyl butyrate resin. These resins can be used alone or in combination of two or more. The method for producing these resins is not particularly limited, and any of bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization can be used.

As the external additive, inorganic fine particles can be preferably used. The primary particle diameter of these inorganic fine particles is 5 m
μm to 2 μm, particularly 5 μm to 500 μm.
mμ is preferred. The specific surface area by the BET method is preferably 20 to 500 m ² / g. Further, the use ratio of the inorganic fine particles is 0.01% of the toner.
To 5% by weight, particularly 0.01 to 2.
It is preferably 0% by weight.

Specific examples of the inorganic fine particles include silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, tin oxide, silica sand, clay, mica, and silica ash. Stone, diatomaceous earth, chromium oxide, cerium oxide, pengara, antimony trioxide, magnesium oxide,
Zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, silicon nitride, and the like can be given.

In addition, polymer fine particles such as polystyrene obtained by soap-free emulsion polymerization, suspension polymerization, and dispersion polymerization, polycondensation systems such as silicone, benzoguanamine, and nylon, and methacrylic acid ester and acrylic acid ester copolymers; Polymer particles made of a curable resin may be used.

Such a fluidizing agent is subjected to a surface treatment,
Hydrophobicity can be increased to prevent deterioration of flow characteristics and charging characteristics even under high humidity. For example, a silane coupling agent, a silylating agent, a silane coupling agent having a fluorinated alkyl group, an organic titanate-based coupling agent, an aluminum-based coupling agent, and the like are preferable surface treatment agents.

Examples of the cleaning property improver for removing the developer after transfer remaining on the photoreceptor and the primary transfer medium include fatty acid metal salts such as zinc stearate, calcium stearate and stearic acid, for example, fine particles of polymethyl methacrylate, Examples include polymer fine particles produced by soap-free emulsion polymerization of polystyrene fine particles and the like. The polymer fine particles preferably have a relatively narrow particle size distribution and a volume average particle size of 0.01 to 1 μm.

The toner used in the present invention may contain a charge control agent, if necessary. As the charge control agent, any known charge control agents can be used. For example, nigrosine dyes, triphenylmethane dyes, chromium-containing metal complex dyes, molybdate chelate pigments, rhodamine dyes, alkoxy amines, quaternary ammonium salts (fluorine-modified) Quaternary ammonium salts), alkyl amides, phosphorus simple substances or compounds, tungsten simple substances or compounds, fluorine-based activators, salicylic acid metal salts, and salicylic acid derivative metal salts. Specifically, Nigrosine dye Bontron 0
3. Bontron P-51, a quaternary ammonium salt; Bontron S-34, a metal-containing azo dye; E-82, an oxynaphthoic acid-based metal complex; E-8, a salicylic acid-based metal complex
4. E-89 of phenolic condensate (above, manufactured by Orient Chemical Industry Co., Ltd.), TP-302, TP-415 of quaternary ammonium salt molybdenum complex (above, manufactured by Hodogaya Chemical Industry Co., Ltd.), quaternary ammonium Salt Copy Charge PSY
VP2038, copy blue PR of triphenylmethane derivative, copy charge of quaternary ammonium salt N
EG VP2036, copy charge NX VP43
4, LRA-901, LR-147 which is a boron complex (manufactured by Nippon Carlit), copper phthalocyanine, perylene, quinacridone, azo pigments, other sulfonic acid groups, carboxyl groups, quaternary ammonium salts And the like.

As the colorant used in the present invention, all pigments and dyes conventionally used as toner colorants are applied. Specifically, carbon black,
There is no particular limitation on lamp black, iron black, ultramarine blue, nigrosine dye, aniline blue, calco oil blue, oil black, azo oil black, and the like. The amount of the colorant used is 1 to 10 parts by weight, preferably 3 to 7 parts by weight.

The method for producing the toner of the present invention may be a conventionally known method, in which a binder resin, a wax component, a colorant, and if necessary, a charge control agent and the like are mixed by a mixer or the like, and then mixed with a hot roll, an extruder, or the like. After kneading using a kneading machine, the mixture is cooled and solidified, pulverized by pulverization using a jet mill or the like, and then classified.

The volume average particle diameter of the toner is 5 to 10
μm is desirable. When the toner particle size is large, the resolution of an obtained image is deteriorated. On the other hand, if it is too small, the flowability of the toner is reduced. Table 1 shows an example of the particle size distribution of the toner used in the present invention. The measurement was performed by Coulter MU
LTISIZER IIe was used. The aperture diameter is 100 μm. To add an external additive to the toner, a mixer such as a super mixer or a Henschel mixer is used.

Conventionally known magnetic materials having an average particle size of 30 to 80 μm are used for the carrier core material used in the present invention. For example, ferromagnetic metals such as iron, cobalt and nickel and alloys such as magnetite, hematite and ferrite are used. Alternatively, compounds and the like can be mentioned. By the way, the magnetic properties of the carrier are affected by the magnet roller incorporated in the developing sleeve, and greatly affect the developing properties and transportability of the developer.

Further, it has been found that the use of a silicone resin having a small surface energy as the coating resin for the carrier used in the present invention is extremely effective. As the coating resin used in the examples of the present invention, a general thermosetting silicone resin was used.

The carrier has a saturation magnetization of 50 to 90 e.
In the case of mu / g, particularly in color copying, the uniformity and gradation reproducibility of the image are excellent, which is preferable. 90e saturation magnetization
If it exceeds mu / g (with respect to an applied magnetic field of 3000 Oersted), brush-like spikes formed by the carrier and the toner on the developing sleeve facing the electrostatic latent image on the photoconductor at the time of development become hard. It is in a tight state, and the gradation and the reproduction of halftone are deteriorated. On the other hand, if it is less than 50 emu / g, it becomes difficult to hold the toner and the carrier on the developing sleeve satisfactorily. The problem that the adhesion and toner scattering are deteriorated is likely to occur.

Further, if the residual magnetization and coercive force of the carrier are too high, good transportability of the developer in the developing device is hindered,
As an image defect, blurring or uneven density in a solid image is likely to occur, and the developing ability is reduced. Therefore, in order to maintain the developability, the remanent magnetization is 10 emu / g or less, preferably 5 emu / g or less, more preferably substantially 0, and the coercive force is 40 Oe or less (3000 Oe, the applied magnetic field). On the other hand, it is important that it is preferably 30 Oe or less, more preferably 10 Oe or less. In consideration of these points, it is preferable to use ferrite as the core material.

Fine powder is added to the carrier coating layer for the purpose of adjusting the carrier resistance, etc. The fine powder dispersed in the coating layer has a particle size of about 0.01 to 5.0 μm. Is preferred.

Further, a coupling agent, in particular, a silane coupling agent can be used for the purpose of adjusting the charge characteristics of the carrier and for improving the adhesion between the coating layer and the magnetic particles. For example, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β-
(N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane hydrochloride, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxy Silane, γ-
Chloropropyltrimethoxysilane, hexamethyldisilazane, γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyldimethyl [3-
(Trimethoxysilyl) propyl] ammonium chloride, γ-chloropropylmethyldimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane (all manufactured by Toray Silicon Co., Ltd.),
Allyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, dimethyldiethoxysilane, 1.3-divinyltetramethyldisilazane, methacryloxyethyldimethyl (3-trimethoxysilylpropyl) ammonium Chloride (all manufactured by Chisso Corporation) and the like.

As the coating resin used in the present invention, an ultraviolet curing type resin is used. The ultraviolet curing type is basically based on solventless coating. However, in order to control the film thickness, after coating by diluting with a solvent, the curing reaction can be advanced by irradiating ultraviolet rays.

Fine powder is added to the coating layer for the purpose of adjusting the carrier resistance, etc. The fine powder dispersed in the coating layer has a particle size of about 0.01 to 5.0 μm. preferable. Further, when the fine powder is carbon black and the content is 2% or less based on the coating resin, the effect of the present invention becomes remarkable.

Hereinafter, other methods for measuring the characteristic values of the toner, carrier and developer according to the present invention will be described below.

(1) Particle size of wax raw material There are a measuring method using a vibrating screen, a measuring method using a laser, and the like. Equipment: HORIBA, Ltd. LA-920 Conditions: Circulation speed 5-7, dispersion medium methanol

(2) Developer Bulk Density Between Photoreceptor / Developing Roller The bulk density of the developer was measured as follows. W / t (g / cm ³ ) where the weight per unit area of the developer after doctor regulation (g / cm ² ) and the width of the developing area in the rotation direction between the photosensitive member and the developing roller is t (cm) ) Is the developer bulk density between the photoconductor and the developing roller.

(3) Carrier magnetic characteristics A BHU-60 type magnetization measurement device (manufactured by Riken Keisaku Co., Ltd.) is used as the measurement device. Specifically, the measurement sample is about 1.0 g
It is weighed, packed in a cell having an inner diameter of 7 mmφ and a height of 10 mm, and set in the above-mentioned device. In the measurement, the applied magnetic field is gradually applied to change the maximum to 3000 Oe. Next, the applied magnetic field is decreased, and finally a hysteresis curve of the sample is obtained on the recording paper. From this, the saturation magnetization, residual magnetization, and coercive force are obtained.

(4) Measurement of Particle Size Distribution of Carrier The measurement was carried out using an SRA type Microtrac particle size analyzer (manufactured by Nikkiso Co., Ltd.) in the range of 0.7 to 125 μm.

Next, an image forming apparatus according to the present invention will be described. The digital copying machine shown in FIG. 1 employs a well-known electrophotographic system and includes a drum-shaped photoconductor 1 therein. Around the photoreceptor 1, a charger 2, an exposure unit 3, a developing unit 4, a transfer unit 5, and a cleaning unit 6 for performing an electrophotographic copying process are arranged along a rotation direction indicated by an arrow A. The exposing unit 3 forms an electrostatic latent image on the photoreceptor 1 based on an image signal read by the reading unit 8 from a document placed on a document table 7 on the top of the copying machine. The electrostatic latent image formed on the photoreceptor 1 is formed into a toner image by a developing unit 4, and the toner image is electrostatically transferred by a transfer unit 5 to a transfer sheet fed from a sheet feeding device 9. The transfer paper having the toner image thereon is conveyed to the fixing unit 10 and fixed, and then discharged outside the apparatus. FIG. 2 is an enlarged view around the developing device 4.

Next, the movement of the toner used in the image forming process will be described with reference to FIGS. The developing device 4 is a two-component developing device in which a developing tank 50 contains a developer composed of a carrier and a toner. When the developing device 4 forms a toner image, the toner of the developer is consumed, and the ratio (toner density) decreases. Therefore, in order to suppress a decrease in image density, when the toner density Vt in the developer becomes a predetermined value or less with respect to the target value Vref of the toner density,
The toner is supplied from the toner hopper 51 to maintain the toner concentration in the developer.

The toner concentration in the developer is measured by a magnetic permeability sensor 52 attached to the lower case of the developing device. The target value Vref of the toner density is set by a value Vsp obtained by measuring a measurement toner image (P pattern) formed on the photoconductor with a photosensor. The toner supplied from the toner hopper 51 via the supply roller 53 is stirred and frictionally charged with the carrier by the stirring member 54 in the developing device 4.

The developer including the carrier and the toner is jumped up to the developing roller 56 by the paddle wheel 55, and the developing roller 56 is magnetized by the magnet in the developing roller 56.
Adsorb on top. The developer is transported by a sleeve on the outer periphery of the developing roller. The tip of the developing doctor 57 and the developing roller 5
The outer peripheral surface of 6 has a predetermined interval, and in the present invention, this interval is defined as a doctor gap. An excess amount of the developer conveyed onto the developing roller is scraped off by the developing doctor 57. The toner in the developer conveyed to the photoreceptor adheres to the electrostatic latent image due to the developing bias.

The toner adhered on the photoreceptor 1 by the above development is electrostatically transferred to transfer paper by the transfer means 5, but about 10% of the toner remains untransferred on the photoreceptor. The untransferred toner is scraped off from the photoreceptor by the cleaning blade 6a and the brush roller 6b of the cleaning means 6, and the scraped-off collected toner is discharged 6c for reuse as recycled toner (T). From its own weight, and is conveyed to the gas flow transfer means as collected toner. The transported toner is returned to the developing device 4 as recycled toner from a recycled toner collecting port 58 shown by a dotted line.

On the other hand, a cleaning means 11 is also provided on the transfer belt 5a of the transfer means 5 for contacting the photosensitive member 1 in the untransferred portion or the non-image portion to adhere the toner. The residual toner on the transfer belt 5a is scraped off by a cleaning blade (not shown) that slides on the belt. It is highly possible that the scraped-off toner contains foreign matter such as paper powder. In this example, the toner dropped from the discharge port 5b without recycling and collected via the toner guide screw pipe (dotted line) without being recycled. The waste toner as a container is sent to the tank 14.

[0056]

The present invention will be described below in detail with reference to Reference Examples and Examples. The parts here are based on weight.

Reference Example 1 (Preparation of Toners T1 to T6) (Preparation of Toner T1) Polyester resin 81.5 parts Styrene-methyl acrylate copolymer 20 parts Carnauba wax (particle diameter 400 μm) 4.5 parts Carbon black 8 Part of the metal-containing monoazo dye 1.0 part After sufficiently mixing and mixing these mixtures in a Henschel mixer, about 30 minutes at a temperature of 130 to 140 ° C by a roll mill.
The mixture was heated and melted for one minute, cooled to room temperature, and the kneaded product was pulverized and classified by a jet mill to obtain a classified toner having a particle size of 7.0 μm. For 100 parts of the classified product, 0.1 parts of silica fine particles were added.
7 parts 0.3 parts of titania fine particles were added and mixed at 1500 rpm with a Henschel mixer to obtain a toner T1.

(Preparation of Toner T2) A toner T2 was obtained in the same manner as in (Preparation of Toner T1) except that 5.5 parts of carnauba wax was used.

(Preparation of Toner T3) A toner T3 was obtained in the same manner as in (Preparation of Toner T1), except that 3.5 parts of carnauba wax was used.

(Preparation of Toner T4) A toner T4 was obtained in the same manner as in (Preparation of Toner T1), except that the particle size of the carnauba wax was 550 μm.

(Preparation of Toner T5) A toner T5 was obtained in the same manner as in (Preparation of Toner T1), except that carnauba wax having a particle size of 700 μm was used.

(Preparation of Toner T6) A toner T6 was obtained in the same manner as in (Preparation of Toner T1), except that a carnauba wax having a particle size of 80 μm was used.

Reference Example 2 (Preparation of Toners T7 to 10) (Preparation of Toner T7) Polyester resin 81.5 parts Styrene-methyl acrylate copolymer 20 parts Rice wax (particle diameter 400 μm) 4.5 parts Carbon black 8 parts 1.0 parts of metal-containing monoazo dyes These mixtures were thoroughly stirred and mixed in a Henschel mixer, and then roll-milled at a temperature of 130 to 140 ° C. for about 30 minutes.
The mixture was heated and melted for one minute, cooled to room temperature, and the kneaded product was pulverized and classified by a jet mill to obtain a classified toner having a particle size of 7.0 μm. For 100 parts of the classified product, 0.1 parts of silica fine particles were added.
7 parts 0.3 parts of titania fine particles were added and mixed at 1500 rpm with a Henschel mixer to obtain toner T7.

(Preparation of Toner T8) A toner T8 was obtained in the same manner as in (Preparation of Toner T7), except that the volume average particle size after classification was 9.5 μm.

(Preparation of Toner T9) (Preparation of Toner T7) except that the volume average particle size after classification was 11.0 μm.
In the same manner as in the above, a toner T9 was obtained.

(Preparation of Toner T10) Except that the volume average particle size after classification was 4.5 μm (Preparation of Toner T7)
In the same manner as in the above, a toner T10 was obtained.

Reference Example 3 (Preparation of Toner T11) Polyester resin 81.5 parts Styrene-methyl acrylate copolymer 20 parts Ester wax (particle size 400 μm) 4.5 parts Carbon black 8 parts Metal-containing monoazo dye 1.0 part After sufficiently stirring and mixing the mixture in a Henschel mixer, the mixture was rolled at a temperature of 130 to 140 ° C. for about 30 minutes.
The mixture was heated and melted for one minute, cooled to room temperature, and the obtained kneaded material was pulverized and classified with a jet mill to obtain a classified toner having a particle diameter of 7.0 μm. For 100 parts of the classified product, 0.1 parts of silica fine particles were added.
7 parts 0.3 parts of titania fine particles were added and mixed at 1500 rpm with a Henschel mixer to obtain toner T11.

Reference Example 4 (Preparation of Carrier C1) Silicon resin (20%) 100 parts γ- (2-aminoethyl) aminopropyltrimethoxysilane 1.0 part Carbon black 0.1 part Toluene 60 parts The mixture was dispersed with a homomixer for 20 minutes to prepare a coating layer forming liquid. This is a ferrite 10 having a weight average particle size.
00 parts (volume average particle diameter 55 μm, saturation magnetization 72 emu /
After forming a coating layer on the surface of g) using a fluidized bed type coating apparatus, the carrier C1 was produced by firing in an electric furnace.

Reference Example 5 (Preparation of Carrier C2) Silicon resin (20%) 100 parts γ- (2-aminoethyl) aminopropyltrimethoxysilane 1.0 part Carbon black 0.5 part Toluene 60 parts The mixture was dispersed with a homomixer for 20 minutes to prepare a coating layer forming liquid. This is a ferrite 10 having a weight average particle size.
00 parts (volume average particle diameter 80 μm, saturation magnetization 80 emu /
After forming a coating layer on the surface of g) using a fluidized bed type coating apparatus, the carrier C2 was produced by firing at the same firing temperature as that of the carrier C1.

Reference Example 6 (Preparation of Carrier C3) Silicon resin (20%) 100 parts γ- (2-aminoethyl) aminopropyltrimethoxysilane 1.0 part Carbon black 0.1 part Toluene 60 parts The mixture was dispersed with a homomixer for 20 minutes to prepare a coating layer forming liquid. This is a ferrite 10 having a weight average particle size.
00 parts (volume average particle diameter 80 μm, saturation magnetization 92 emu /
After forming a coating layer on the surface of g) using a fluidized bed type coating apparatus, the carrier C3 was produced by firing at the same firing temperature as the carrier C1.

Reference Example 7 (Preparation of Carrier C4) Silicon resin (20%) 100 parts γ- (2-aminoethyl) aminopropyltrimethoxysilane 1.0 part Carbon black 0.1 part Toluene 60 parts The mixture was dispersed with a homomixer for 20 minutes to prepare a coating layer forming liquid. This is a ferrite 10 having a weight average particle size.
00 parts (volume average particle diameter 55 μm, saturation magnetization 40 emu /
After forming a coating layer on the surface of g) using a fluidized bed type coating apparatus, the carrier C4 was produced by firing at the same firing temperature as the carrier C1.

(Examples 1 to 8 and Comparative Examples 1 to 6) When the volume average particle diameter of the carrier is 55 μm, 5 parts of toner and 95 parts of the carrier, and when the volume average particle diameter of the carrier is 80 μm, 3 parts of toner 97 parts of the carrier were stirred and mixed at 50 rpm for 15 minutes using a turbulator mixer to obtain a two-component developer. A developer was prepared by combining the toner and the developer shown in Table 1, and the following evaluation was performed under the developing conditions shown in Table 1.

(Evaluation of Image) The above-prepared developer was continuously copied 100,000 sheets (printing rate 6%) using a modified Ricoh copier imagio MF6550, and the start time was 100,000 sheets. Evaluate spent property and image quality. The image quality was evaluated for fixability, image density, background stain, and gradation (the same applies hereinafter). The results are shown in Tables 2 and 3.

Spent property: Spent property is when the weight of the carrier from which the developer has been blown off is Wb, and the weight after the carrier is immersed in a solvent to remove substances adhered to the carrier surface and the carrier is dried is Wa. Is obtained by the following equation. Spent property = (Wb−Wa) / Wb × 100

Fixability: Fixability was evaluated as follows. After shaping the fixing heater temperature to obtain a fixed image, a mending tape (manufactured by 3M) was applied to the fixed image, a certain pressure was applied, and then the film was slowly peeled off. The image density before and after that is measured by a Macbeth reflection densitometer, and the fixing rate is calculated by the following equation. The fixing roller temperature is gradually decreased, and the temperature at which the fixing rate represented by the following equation becomes 80% or less is defined as the fixing temperature. Also, the temperature at which the hot offset phenomenon starts appearing as the temperature is increased is defined as the hot offset occurrence temperature. Fixing rate = image density on tape / image density × 100

Image density background stain, gradation: Image density evaluation is measured by a Macbeth reflection densitometer. The image density and the background stain were ranked according to the degree, and ○ was regarded as a pass level, Δ was regarded as an allowable level, and × as an unacceptable level. Regarding the gradation, the roughness of the gray scale portion was visually evaluated, and particularly excellent image quality was evaluated as ◎, excellent image quality as ○, allowable level as Δ, and unacceptable level as ×.

[0077]

[Table 1]

[0078]

[Table 2]

[0079]

[Table 3]

Reference Example 8 (Preparation of Toners T21 to T28) (Preparation of Toner T21) Polyester resin 81.0 parts Styrene-methyl acrylate copolymer 20 parts Ester wax (particle size: 400 μm) 5.0 parts Carbon black 8 parts 1.0 parts of metal-containing monoazo dyes These mixtures were thoroughly stirred and mixed in a Henschel mixer, and then roll-milled at a temperature of 100 to 110 ° C. for about 30 minutes.
The mixture was heated and melted for one minute, cooled to room temperature, and the kneaded product was pulverized and classified by a jet mill to obtain a classified toner having a particle size of 7.0 μm. For 100 parts of the classified product, 0.1 parts of silica fine particles were added.
7 parts 0.3 parts of titania fine particles were mixed with a Henschel mixer in 1 part.
500 rpm was added and mixed to obtain toner A1 (loose apparent density 0.32 g / cm ³ , average circularity 0.93).

(Preparation of Toner T22) Except that the kneading temperature in the roll mill was set at 130 to 140 ° C.,
In the same manner as in Production 1), a toner T22 (loose apparent density 0.29 g / cm ³ , average circularity 0.93) was obtained.

(Preparation of Toner T23) Toner T23 (loose apparent density 0.33 g) was prepared in the same manner as in (Preparation of Toner T21) except that the pulverizing and classifying step was performed using a mechanical pulverizer.
/ Cm ³ and an average circularity of 0.96).

(Preparation of Toner T24) Toner T24 (loose apparent density 0.31 g / cm ³ , average circularity) in the same manner as (Preparation of Toner T21) except that the particle size of the ester wax was 100 μm. 0.94).

(Preparation of Toner T25) Toner T25 (loose apparent density 0.33 g / cm ³ , average circularity) in the same manner as in (Preparation of Toner T21) except that the ester wax having a particle size of 600 μm was used. 0.94).

(Preparation of Toner T26) Toner T26 (loose apparent density 0.33 g / cm ³ ) in the same manner as in (Preparation of Toner T21) except that carnauba wax (particle size: 500 μm) was used instead of the ester wax. , An average circularity of 0.93).

(Preparation of Toner T27) Toner T27 (loose apparent density 0.34 g / cm ³ ) in the same manner as in (Preparation of Toner T21) except that rice wax (particle size: 400 μm) was used instead of ester wax. An average circularity of 0.94) was obtained.

(Preparation of Toner T28) (Preparation of Toner T22) Except that the additive mixing condition was 1500 rpm.
In the same manner as in toner T28 (loose apparent density 0.26
g / cm ³ and an average circularity of 0.93).

Reference Example 9 (Preparation of Carrier C21) Silicon resin (20%) 100 parts γ- (2-aminoethyl) aminopropyltrimethoxysilane 1.0 part Carbon black 0.1 part Toluene 60 parts The mixture was dispersed with a homomixer for 20 minutes to prepare a coating layer forming liquid. This is a ferrite 10 having a weight average particle size.
00 parts (volume average particle diameter 55 μm, saturation magnetization 72 emu /
After forming a coating layer on the surface of g) using a fluidized bed coating apparatus, the carrier C21 was produced by firing in an electric furnace.

Reference Example 10 (Preparation of Carrier C22) Silicon resin (20%) 100 parts γ- (2-aminoethyl) aminopropyltrimethoxysilane 1.0 part Carbon black 0.5 part Toluene 60 parts The mixture was dispersed with a homomixer for 20 minutes to prepare a coating layer forming liquid. This is a ferrite 10 having a weight average particle size.
00 parts (volume average particle diameter 80 μm, saturation magnetization 80 emu /
After forming a coating layer on the surface of g) using a fluidized bed type coating apparatus, the carrier C22 was produced by firing at the same firing temperature as the carrier C21.

Reference Example 11 (Preparation of Carrier C23) Silicon resin (20%) 100 parts γ- (2-aminoethyl) aminopropyltrimethoxysilane 1.0 part Carbon black 0.1 part Toluene 60 parts The mixture was dispersed with a homomixer for 20 minutes to prepare a coating layer forming liquid. This is a ferrite 10 having a weight average particle size.
00 parts (volume average particle diameter 80 μm, saturation magnetization 92 emu /
After forming a coating layer on the surface of g) using a fluidized bed type coating device, the carrier C23 was produced by firing at the same firing temperature as the carrier C21.

Reference Example 12 (Preparation of Carrier C24) Silicon resin (20%) 100 parts γ- (2-aminoethyl) aminopropyltrimethoxysilane 1.0 part Carbon black 0.1 part Toluene 60 parts The mixture was dispersed with a homomixer for 20 minutes to prepare a coating layer forming liquid. This is a ferrite 10 having a weight average particle size.
00 parts (volume average particle diameter 55 μm, saturation magnetization 40 emu /
After forming a coating layer on the surface of g) using a fluidized bed type coating apparatus, the carrier C24 was produced by firing at the same firing temperature as the carrier C21.

(Examples 9 to 19 and Comparative Examples 7 and 8) When the carrier particle size is 55 μm, 5 parts of the toner and the carrier 9
5 parts and a carrier particle size of 80 μm, 3 parts of the toner and 97 parts of the carrier were mixed at 50 rpm and 1
The mixture was stirred and mixed for 5 minutes to obtain a two-component developer.

A developer was prepared by combining the toner and the developer shown in Table 4, and the following evaluation was performed under the developing conditions shown in Table 5.

[0094]

[Table 4]

[0095]

[Table 5]

Reference Example 13 (Preparation of Toners T31 to T37) (Preparation of Toner T31) Polyester resin 90 parts Ester wax (particle size 400 μm) 5 parts Carbon black 5 parts Metal-containing monoazo dye 1 part These mixtures were placed in a Henschel mixer. After sufficiently stirring and mixing with a roll mill, the mixture was heated and melted at a temperature of 80 ° C. for about 30 minutes, cooled to room temperature, and the kneaded product was pulverized and classified by a jet mill to obtain a classified toner having a particle size of 7.0 μm. . To 100 parts of the classified product, 0.7 parts of silica fine particles and 0.3 parts of titania fine particles were mixed at 1500 rpm with a Henschel mixer.
m, and mixed to obtain a toner T31 (25% agglomeration degree, 7.5 μm in volume average particle size, 68% by number of particles having a particle size of 5 μm or less).

(Preparation of Toner T32) Toner T32 (coagulation degree: 32%, volume average particle size: 7.5 μm, 5 μm or less) in the same manner as in (Preparation of toner T31) except that the kneading temperature in the roll mill was set to 120 ° C. (Particle number 70 number%) was obtained.

(Preparation of Toner T33) Toner T33 (coagulation degree 36%, volume average particle diameter 7.5 μm, 5 μm or less) in the same manner as in (Preparation of toner T31) except that the kneading temperature in the roll mill was set at 140 ° C. (Particle number 70 number%) was obtained.

(Preparation of Toner T34) Toner T34 (preparation of toner T31) was prepared in the same manner as in (Preparation of Toner T31) except that the volume average particle diameter after classification by jet milling was 9.5 μm, and the number of particles was 5 μm or less and 30%. 25%).

(Preparation of Toner T35) Toner T35 (preparation of toner T31) was prepared in the same manner as in (Preparation of toner T31) except that the volume average particle size after classification by jet milling was 6.5 μm and the number of particles was 5 μm or less and 80%. 29%).

(Preparation of Toner T36) Toner T36 (27% aggregation, volume average particle diameter) in the same manner as in (Preparation of Toner T31) except that carnauba wax (particle diameter: 500 μm) was used instead of ester wax. 7.5 μm,
5 μm or less 72% by number of particles).

(Preparation of Toner T37) Toner T37 (coagulation degree 26%, volume average particle diameter 7%) in the same manner as (Preparation of toner T31) except that rice wax (particle diameter 100 μm) was used instead of ester wax. .5 µm, 5 µ
m or less, the number of particles is 69 number%).

Reference Example 14 (Production of Carrier C31) Silicon resin (20%) 100 parts γ- (2-aminoethyl) aminopropyltrimethoxysilane 1.0 part Carbon black 0.1 part Toluene 60 parts The mixture was dispersed with a homomixer for 20 minutes to prepare a coating layer forming liquid. This is a ferrite 10 having a weight average particle size.
00 parts (volume average particle diameter 55 μm, saturation magnetization 72 emu /
After forming a coating layer on the surface of g) using a fluidized bed coating device, the carrier C31 was produced by firing in an electric furnace.

Reference Example 15 (Preparation of Carrier C32) Silicon resin (20%) 100 parts γ- (2-aminoethyl) aminopropyltrimethoxysilane 1.0 part Carbon black 0.5 part Toluene 60 parts The mixture was dispersed with a homomixer for 20 minutes to prepare a coating layer forming liquid. This is a ferrite 10 having a weight average particle size.
00 parts (volume average particle diameter 80 μm, saturation magnetization 80 emu /
After forming a coating layer on the surface of g) using a fluidized bed type coating apparatus, the carrier C32 was produced by firing at the same firing temperature as the carrier C31.

Reference Example 16 (Preparation of Carrier C33) Silicon resin (20%) 100 parts γ- (2-aminoethyl) aminopropyltrimethoxysilane 1.0 part Carbon black 0.1 part Toluene 60 parts The mixture was dispersed with a homomixer for 20 minutes to prepare a coating layer forming liquid. This is a ferrite 10 having a weight average particle size.
00 parts (volume average particle diameter 80 μm, saturation magnetization 92 emu /
After forming a coating layer on the surface of g) using a fluidized bed type coating apparatus, the carrier C33 was produced by firing at the same firing temperature as the carrier C31.

Reference Example 17 (Preparation of Carrier C34) Silicon resin (20%) 100 parts γ- (2-aminoethyl) aminopropyltrimethoxysilane 1.0 part Carbon black 0.1 part Toluene 60 parts The mixture was dispersed with a homomixer for 20 minutes to prepare a coating layer forming liquid. This is a ferrite 10 having a weight average particle size.
00 parts (volume average particle diameter 55 μm, saturation magnetization 40 emu /
After forming a coating layer on the surface of g) using a fluidized bed type coating device, the carrier C34 was produced by firing at the same firing temperature as the carrier C31.

(Examples 20 to 29 and Comparative Examples 9 and 1
0) (Preparation of developer) When the particle size of the carrier is 55 μm, 5 parts of the toner and 95 parts of the carrier, and when the particle size of the carrier is 80 μm, 3 parts of the toner and 97 parts of the carrier are stirred with a tumbler mixer at 50 rpm for 15 minutes. After mixing, a two-component developer was obtained. A developer was prepared by combining the toner and the developer shown in Table 6, and the following evaluation was performed under the developing conditions shown in Table 7.

[0108]

[Table 6]

[0109]

[Table 7]

[0110]

According to the present invention, it is possible to provide a two-component developer which is particularly excellent in fixing property, image stability and spent property, and further provides high image quality, and an image forming method.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a digital copying machine using a developer of the present invention.

FIG. 2 is a diagram illustrating movement of toner in a developing and toner supply unit according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charger 3 Exposure means 4 Developing means 5 Transfer means 5a Transfer belt 5b Discharge port 6 Cleaning means 6a Cleaning blade 6b Brush roller 6c Discharge port 7 Document mounting table 8 Document reading means 9 Paper feeder 10 Fixing means 11 Cleaning means 14 Waste toner tank 50 Developing tank 51 Toner hopper 52 Magnetic permeability sensor 53 Supply roller 53 54 Developing device 55 Paddle wheel 56 Developing roller 57 Developing doctor 58 Recycled toner collecting port 60 Toner replenishing unit

Continued on the front page (72) Inventor Kazuyuki Yazaki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Takayuki Koike 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Company (72) Inventor Koji Suzuki 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Tadashi Kasai 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Hiroshi Takahashi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Mitsuo Aoki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Akihiro Ito 3-1 Shinmei-do, Nakaname, Shimada-cho, Shibata-cho, Shibata-gun, Miyagi Prefecture F-term (reference) 2H005 AA06 BA06 CA12 CA14 EA02 EA05 EA10 2H077 AD13 AD18 AD22 EA03 EA21

Claims (9)

[Claims] 1. An oil-less fixed image forming method using a two-component developer comprising a wax-dispersed toner and a carrier, wherein the dynamic friction coefficient is 0.18 to 0.30 and the loose apparent density is 0.30 g / cm ^3. A toner that satisfies at least one of the above requirements or a cohesion degree of 30% or less, has a doctor gap of 0.3 to 0.8 mm in an electrophotographic image forming apparatus, and has a developer between a photoreceptor and a developing roller. An image forming method using oilless fixing, wherein the bulk density is 1.5 to 2.5 g / cm ³ . 2. A toner and carrier in which a wax satisfying at least one of a dynamic friction coefficient of 0.18 to 0.30, a loose apparent density of 0.30 g / cm ³ or more, and a cohesion degree of 30% or less is satisfied. And the doctor gap of the electrophotographic image forming apparatus is 0.3 to 0.8 mm, and the bulk density of the developer between the photoconductor and the developing roller is 1.5 to 2.5 g / cm. ^{3. A} developer for electrophotography, which is used in the image forming method using oilless fixing, which is ³ . 3. The electrophotographic developer according to claim 2, wherein at least one of carnauba wax, rice wax, and ester wax is used as the wax dispersed in the toner. 4. The electrophotographic developer according to claim 2, wherein the wax dispersed in the toner has a raw material average particle diameter of 100 to 600 μm. 5. The electrophotographic developer according to claim 2, wherein the toner has a volume average particle diameter of 5 to 10 μm. 6. The electrophotographic developer according to claim 5, wherein the toner having a volume average particle size of 5 μm or less accounts for 60 to 80% by number. 7. The electrophotographic developer according to claim 2, wherein the circularity of the toner is 0.94 or more. 8. The electrophotographic developer according to claim 2, wherein the surface of the carrier is coated with a silicone resin. 9. A carrier having a saturation magnetization of 50 to 90 emu.
/ G. The electrophotographic developer according to any one of claims 2 to 8, wherein