JP2002108003A - Image forming method and magnetic toner and developer used therein - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that satisfactory image density can not be obtained and foggy spots are increased since the electrified amount of MICR toner is low and the magnetic force of the MICR toner restrains developability when MICR toner for a magnetic one- or two-component developer is used in a nonmagnetic two-component developer system in which high speed development is possible. SOLUTION: This image forming method comprises depositing the developer comprising at least a magnetic carrier and toner on a developer carrier having a means for generating a magnetic field on the inside and supplying the developer-deposited developer carrier to a latent image holding body to develop a latent image on the latent image holding body. The toner to be used comprises at least a binder resin, a magnetic material and wax and has 25 emu/g or lower saturated magnetization, 7-20 emu/g residual magnetization and -18 to -35 μC/g triboelectrified amount. The magnetic carrier to be used is coated with a resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in electrophotography, electrostatic printing, electrostatic recording, and the like, and particularly, in a magnetic ink character recognition (hereinafter referred to as "MICR") system. The present invention relates to a magnetic toner and a magnetic developer suitable for forming readable characters having magnetism using a non-magnetic two-component developing system.

[0002]

2. Description of the Related Art Conventionally, in an image forming method in a printer, a facsimile or the like to which electrophotography or electrostatic recording is applied, for example, an electrostatic charge image is formed on the surface of a cylindrical photosensitive drum, and then the photosensitive drum is formed. The magnetic developer is attracted to the surface of the sleeve and transported by a developing roll comprising a sleeve provided with a permanent magnet member built therein and coaxially and rotatably fitted with the permanent magnet member. I do. Thereafter, a method is employed in which a magnetic brush is formed in the developing area, and the surface of the photosensitive drum on which the electrostatic charge image is formed is rubbed with the magnetic brush so as to be visualized as a toner image. The most common means is to transfer this visualized toner image to recording paper and then fix it by heat.

On the other hand, in recent years, as image forming apparatuses such as electrophotographic copying machines have become widespread, the uses thereof have been diversified, and character printing machines used in MICR systems have been devised as application fields of electrophotographic printers. Have been.

This MICR system prints information such as the issuing bank, amount, account number and the like on checks and bills using magnetic ink, and efficiently sorts and classifies information at a clearing house using a magnetic reader. It was designed to do it. In this case, offset printing using magnetic ink has been mainly used in the past. However, as business transactions using personal checks, bills, and the like have become more active, a small MICR character printing machine (hereinafter referred to as “MICR encoder”) has been developed. Demand) is increasing.

The above conventional MICR encoder is mainly an impact printer to which a thermal copying method is applied. In this case, however, most of the single function machines print only MICR characters. There is a disadvantage that it cannot be used. For this reason, printing of general documents and / or graphics is possible, and the MIC is used.
There is a demand for an electrophotographic printer that can print R characters and exhibits a good MICR recognition rate.

[0006]

Since MICR printing uses a toner containing a magnetic material, a magnetic one-component developing method using a magnetic one-component developer or a magnetic two-component developer obtained by mixing a magnetic toner and a magnetic carrier is used. It is carried out by a magnetic two-component development system used. The magnetic one-component developing method or the magnetic two-component developing method has a lower charge amount and a lower charging speed than the non-magnetic two-component developing method in which a non-magnetic toner and a magnetic carrier are mixed, so that high-speed development is difficult. is there. Further, the specific gravity of the toner is large, and the toner consumption is increased. Therefore, when attempting to use a conventional MICR toner for a magnetic one-component or two-component developer in a non-magnetic two-component developing system capable of high-speed development, the charge amount is low and the magnetic force of the toner suppresses developability. However, a sufficient image density cannot be obtained, and fogging increases. An object of the present invention is to solve the above-mentioned problems and apply a magnetic toner to a non-magnetic two-component developing system,
An object of the present invention is to provide an image forming method capable of forming a CR magnetic character. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a magnetic toner and a magnetic developer which can be applied to a non-magnetic two-component developing system to form a MICR magnetic character.

[0007]

As a result of intensive studies, the present inventor has found that in order to apply a toner containing a magnetic substance to a non-magnetic two-component developing system, it is necessary to develop a toner containing a magnetic powder capable of reading magnetic characters. It has been found that it is necessary to use a combination of a magnetic toner whose content is suppressed as much as possible and a carrier capable of increasing the charge amount of the toner and charging in a short time in order to ensure the toner properties.

That is, a first aspect of the present invention is to supply a developer comprising at least a magnetic carrier and a toner to a latent image holding member by supporting the developer on a developer holding member having means for generating a magnetic field therein. In an image forming method for developing a latent image on a latent image holding member, the toner contains at least a binder resin, a magnetic substance, and a wax, and has a saturation magnetization of 25 emu.
/ G or less, the residual magnetization is 7 to 20 emu / g, the triboelectric charge is −18 to −35 μC / g, and the magnetic carrier is a resin-coated image forming method.

According to a second aspect of the present invention, a developer comprising at least a magnetic carrier and a toner is carried on a developer carrier having a means for generating a magnetic field therein and supplied to the latent image carrier to supply the latent image carrier. In the image forming method for developing the above latent image, the toner contains at least a binder resin, a magnetic substance, and a wax, has a saturation magnetization of 25 emu / g or less, a residual magnetization of 7 to 20 emu / g, and a triboelectric charge of 9 to 22 μm.
C / g, and the magnetic carrier is a resin-coated image forming method.

According to a third aspect of the present invention, a developer comprising at least a resin-coated magnetic carrier and a toner is carried on a developer carrier having a means for generating a magnetic field therein and supplied to a latent image carrier. The toner used in an image forming method for developing a latent image on a latent image holding member,
At least binder resin, magnetic material, including wax,
Saturation magnetization of 25 emu / g or less, residual magnetization of 7 to 20 em
u / g and the triboelectric charge amount is −18 to −35 μC / g.
Is a magnetic toner.

According to a fourth aspect of the present invention, a developer comprising at least a resin-coated magnetic carrier and a toner is carried on a developer carrier having a means for generating a magnetic field therein and supplied to the latent image carrier. The toner used in an image forming method for developing a latent image on a latent image holding member,
At least binder resin, magnetic material, including wax,
Saturation magnetization of 25 emu / g or less, residual magnetization of 7 to 20 em
u / g and a triboelectric charge of 9 to 22 μC / g.

According to a fifth aspect of the present invention, a developer comprising at least a magnetic carrier and a toner is carried on a developer carrier having a means for generating a magnetic field therein and supplied to the latent image carrier to supply the latent image carrier. The developer used in the image forming method for developing the above latent image, wherein the toner contains at least a binder resin, a magnetic substance, and a wax, and has a saturation magnetization of 25%.
emu / g or less, the residual magnetization is 7 to 20 emu / g, the triboelectric charge is -18 to -35 [mu] C / g, and the magnetic carrier is a resin-coated developer.

According to a sixth aspect of the present invention, a developer comprising at least a magnetic carrier and a toner is carried on a developer carrier having means for generating a magnetic field therein and supplied to the latent image carrier to supply the latent image carrier. The developer used in the image forming method for developing the above latent image, wherein the toner contains at least a binder resin, a magnetic substance, and a wax, and has a saturation magnetization of 25%.
emu / g or less, residual magnetization of 7 to 20 emu / g and triboelectric charge of 9 to 22 μC / g, and the magnetic carrier is a resin-coated developer.

In each of the above inventions, the saturation magnetization is 22 emu /
g or less, the residual magnetization is preferably 9 to 18 emu / g, and the triboelectric charge amount is -20 to -30 for negative charge.
μC / g, and the range of +10 to +20 μC / g for positive charging is preferable.

The developer according to the fifth and sixth inventions comprises 20% by weight.
The toner concentration is preferably as follows, and more preferably 3 to 10% by weight.

The binder resin is styrene-acrylic,
Select a resin suitable for the fixing system, such as polyester, epoxy, or phenoxy resin. Fixing methods suitable for the present invention are heat roll fixing, flash fixing, and oven fixing.

The magnetic material is magnetite, Ba ferrite,
A material having relatively large coercive force and remanent magnetization such as Sr ferrite is preferable. A combination of two or more types may be used. Although the shape of the magnetic material depends on the crystal, the granular shape is less likely to be exposed on the toner surface than the needle shape, and therefore less easily leaks the charge.
The magnetic material preferably has a size of 0.5 μm or less. In order to increase the affinity with the binder resin and improve the dispersibility in the toner, it is preferable to subject the magnetic material surface to a hydrophobic treatment with a titanate coupling agent or a silane coupling agent. If the ratio of the magnetic powder is large, the chargeability and developability of the toner are reduced. Therefore, the content of the magnetic substance in the toner should be an amount that can provide the residual magnetization required for magnetic reading, which is insufficient. It is preferable to supplement the color tone and blackness of the toner with a colorant such as carbon black or a dye or pigment. The content of the magnetic substance in the toner is 10% by weight or more,
A range of less than weight% is preferred.

It is preferable to add wax in order to increase the surface smoothness of the printing surface. Low molecular weight polyethylene,
Polypropylene, ethylene-propylene copolymer, modified polyethylene, modified polypropylene, Fischer-Tropsch wax, Sasol wax, montanic acid wax, carbana wax and the like can be used. Addition amount is 1
About 6% is preferable. The wax is preferably uniformly dispersed in the toner, and may be dispersed in the binder resin in advance.

The charge control agent is selected according to the polarity of the toner. Chromium azo complex, iron azo complex, salicylic acid metal complex, calixarene and the like are suitable for negative charge, and nigrosine dye and phenylmethane dye are preferable for positive charge.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <Developing Apparatus> An organic photoconductor of 50φ is charged to −500 V by a scorotron charger.
Exposure to -40 V by LED. 850 development pole
A 20φ SUS sleeve with a built-in magnet roll magnetized to 4 poles to give G
m was blasted. A gap of 0.6 mm was provided on the magnet roller by a blade, and a developer was applied. At a process speed of 200 mm / S, a sleeve peripheral speed ratio of 1.5 times, and a developing gap of 0.85 mm, -4
An image containing MICR characters was developed by applying a developing bias of 00 to -480 V. Transfer by D-corotron
C + AC was performed, and fixing was performed using a heat roller type fixing machine equipped with a halogen lamp.

In the following Examples and Comparative Examples, a developer comprising at least a magnetic carrier and a toner is carried on a developer carrier having a means for generating a magnetic field therein, and supplied to a latent image carrier to supply a latent image. An image forming method for developing a latent image on an image carrier, wherein the density of an image obtained when the toner is a non-magnetic toner is similar to that of the non-magnetic toner except that the toner has magnetism. An image forming method that is larger than that of an image obtained when the toner is used was carried out using the above-described developing device to form a MICR magnetic character.

Example 1 A toner was prepared as follows.・ 68 parts of polyester resin (Tg62 ° C, Tm125 ° C) ・ 4 parts of wax NP105 ・ 1 part of polyethylene 220MP ・ 1 part of charge control agent TRH ・ 1 part of carbon black MA100 ・ Magnetic powder MAT740 (silane coupling agent made by Toray Dow Corning Silicone (Surface treated with SH6040) 25 parts The above components were mixed by a Henschel mixer, and kneaded at a set temperature of 120 ° C. by a twin screw extruder with a cooling device. Thereafter, the mixture was cooled and crushed by a drum flaker, and further crushed by a rotoplex coarse crusher. The fine pulverization is pulverized by a rotor-stator type pulverizer T250, and the lower limit is classified by a microplex to obtain a volume average particle size of 9.5 μm.
m, 5 to 16 μm distribution particles were obtained. Toner 1 was prepared by mixing 0.7% of silica (RX200 manufactured by Nippon Aerosil) as an external additive using a Henschel mixer. The saturation magnetization σs (10 kOe) of the obtained toner 1 is 20.5 (em
u / g) and the residual magnetization σr was 13.5 (emu / g).

The carrier used was a coating carrier 1 in which a magnetite carrier having a volume of 44 to 105 μm (volume average particle size: 68 μm) was coated with 0.5% of a silicon-based resin. The developer adjusted to a toner concentration of 5 wt% is V
The mixture was mixed by a mold mixer for 30 minutes. Blow off TB2
The charge amount at 00 was -28.5 μC / g. 750 g of this developer and 1500 g of toner were charged into a developing machine equipped with a toner hopper and a replenishing device with a feeder using a sponge roll equipped with a stirring blade and a magnetic bridge type toner density sensor, respectively, and evaluated for printing.

As a result, the image density was 1.4 or more, and the difference between the fog and the paper was 0.5 or less in terms of hunter whiteness. The image quality was free of dust and streaks, and the halftone uniformity and gradation were good. The magnetic intensity of the MICR character was 127% and did not change with more than 20 leader passes. The stability of the developer was good, and sufficient developability was exhibited even in an environment of high temperature and high humidity or low temperature and low humidity. The output of the magnetic bridge sensor was also stable, and the fluctuation of the toner concentration was 5 ± 1%. The printing durability was good, and no reduction in image density or increase in fog was observed even after printing 100k sheets. The amount of toner fixed on the carrier, that is, the amount of toner spent, was also small.

Example 2 A toner was prepared as follows.・ Styrene-acrylic resin (St-nBA, Tg60 ° C., Tm130 ° C., bimodal, Mw / Mn 21.0) 72 parts ・ Polypropylene wax Biscol 550P 3 parts ・ UMEX 100TS 1 part Part: Carbon black Mitsubishi Chemical # 44 1 part Magnetic powder KBN400 (manufactured by Ajinomoto Co., Ltd. Titanate Coupling Agent Planeact TTS) 22 parts The above components were treated in the same manner as Toner 1 to obtain Toner 2. Was. 37-88 μm (volume average particle size 54
μm) Li-Mn-based ferrite carrier was coated with 0.5% of a silicon-based resin mixed with conductive carbon black.

Example 3 A toner was produced as follows.・ Styrene-acrylic resin (St-2EHA, Tg62 ° C, Tm135 ° C) 50 parts ・ Polyester resin (Tg62 ° C, Tm115 ° C) 20 parts ・ Wax (made by Hoechst) PP230 3 parts ・ PE190 1 part ・ Charge control agent Orient 1 part of Chemical S44, 10 parts of magnetite (manufactured by Kanto Denka Kogyo), KBN400 10 parts, 15 parts of KBI20VH A toner was similarly produced using each of the above components to obtain Toner 3. As a result of evaluation of printing using Toner 3 and Carrier 1, good development characteristics and magnetic strength were exhibited.

(Comparative Example 1) The magnetic powder in the toner 2 was K
A toner 4 was obtained in the same manner as the toner 2, except that the BI20VH was changed to 35 parts. Printing evaluation was performed in the same manner as in Example 2 using Toner 4. When the ratio of the magnetic powder is large, the residual magnetization of the toner is large, but at the time of development, the toner is attracted by the magnetic force of the magnet roller and the magnetic force on the magnetic brush, resulting in impaired developability.

(Comparative Example 2) The magnetic powder in the toner 2 was K
A toner 5 was obtained in the same manner as the toner 2 except that BN400 was changed to 10 parts. Printing evaluation was performed in the same manner as in Example 2 using Toner 5. Although the developability was sufficient, the magnetic properties of the toner were insufficient and the magnetic strength was low.

Comparative Example 3 Printing evaluation was performed in the same manner as in Example 1 except that the carrier in Example 1 was changed to the magnetite carrier 3 without coating. In Comparative Example 3, the charge amount of the developer was small and the developability was low. As a result, sufficient magnetic strength could not be obtained.

Comparative Example 4 Printing evaluation was performed in the same manner as in Example 2 except that the carrier in Example 2 was changed to the ferrite carrier 4 without coating. Also in the case of the ferrite carrier, the amount of charge of the developer was small and the developability was low without the coating. As a result, sufficient magnetic strength could not be obtained.

(Comparative Example 5) A similar printing test was performed using a normal two-component non-magnetic toner instead of Toner 1 in Comparative Example 3. The carrier 3 also showed good image characteristics in combination with the non-magnetic two-component toner.

A magnetic material having a relatively high coercive force, such as that used for the MICR toner, has a shape with a high aspect ratio such as a needle shape. When such a magnetic powder is dispersed in toner particles, aggregation tends to occur, and a part of the magnetic substance is easily exposed on the toner surface. Since the magnetic material has a lower electrical resistivity than the resin used for the toner, when the magnetic material is exposed on the toner surface, electric charge leaks easily, and it is expected that the charge amount cannot be maintained and decreases. Therefore, in order to apply a toner containing a magnetic substance to a non-magnetic two-component developing system, it is necessary to use a carrier coated with a resin coated with a high charging ability and a high electric resistivity in a comparative example. Inferred from the results of 3 and 5.

The results are summarized in Table 1.

[0034]

[Table 1]

The values of the saturation magnetization and the residual magnetization were measured by a vibrating magnetometer (VSM) by filling the toner in a capsule. The numerical value of the image density is indicated by a reflection densitometer (Macbeth RD91
The image density according to 4) is 1.35 or more, preferably 1.4.
0 or more is good. The fog value was represented by the difference (dH) between the hunter whiteness of the white paper before printing and the white background after printing. The smaller this value is, the smaller the white background fog is, and preferably 0.5 or less. In order for a magnetic reader to correctly recognize a printed MICR font, the MICR font needs to have an appropriate magnetic reading strength (magnetic strength, also referred to as signal strength). The standard of magnetic strength is determined by each country, but is generally 100 to 200%. It is desirable that the lower limit of the magnetic strength be 110%.

Example 4 A 35φ positive organic photoconductor was charged to +450 V by a brush charger, and was exposed to +70 V by laser beam scanning. A 18φ aluminum sleeve having a built-in magnet roll magnetized to four poles so that the developing pole becomes 800 G is blasted to a surface roughness Rz of 10 μm and further Ni
A base metal was plated. A gap of 0.5 mm was provided on the magnet roller by a blade to apply a developer. At a process speed of 150 mm / S, a sleeve peripheral speed ratio of 1.7, and a developing gap of 0.7 mm, a +400 V developing bias and an AC bias (1 kV, 1.5 kHz) were applied to develop an image containing MICR characters. The transfer was performed by DC + AC using a roller, and the image was fixed at a set temperature of 150 ° C. by a heat roller type fixing machine equipped with a halogen lamp. The photoreceptor after the transfer was cleaned by a blade cleaning method.

The toner was prepared as follows.・ Styrene-acrylic resin (St-nBA, Tg62 ° C, Tm128 ° C, bimodal, Mw / Mn13.5) 69 parts ・ Polyethylene propylene wax NP105 2 parts ・ Wax 210MP 1 part ・ Charge control agent Copy Blue PR made by Hoechst 2 parts-Carbon black 1 part of MA600 manufactured by Mitsubishi Chemical Co., Ltd.-Magnetic powder KBN400 (surface-treated with an anilinosilane coupling agent SZ6083 manufactured by Toray Dow Corning Silicone) 25 parts The above components are mixed with a Henschel mixer and equipped with a cooling device And kneaded at a set temperature of 120 ° C. with a twin screw extruder. Thereafter, the mixture was cooled and crushed by a drum flaker, and further crushed by a rotoplex coarse crusher. The fine pulverization is pulverized by a rotor stator type pulverizer T250 manufactured by Turbo Kogyo Co., Ltd., and the lower limit is classified by a microplex. The volume average particle size is 10.5 μm, 1% less than 5 μm, and more than 16 μm 3.5%.
Particles having a distribution of Toner 6 was prepared by mixing 0.6% of silica (HVK2150 manufactured by Wacker) as an external additive using a Henschel mixer. The saturation magnetization σs (10 kOe) of the obtained toner 6 is 22.3 (emu / g) and the residual magnetization σs is
r was 16.5 (emu / g).

As the carrier, a coated carrier 6 in which a magnetite carrier having a particle size of 44 to 105 μm (average particle size: 68 μm) was coated with 0.5% of a fluororesin was used. The developer adjusted to a toner concentration of 7 wt% was mixed for 30 minutes using a Nauta mixer. Blow-off TB20
The charge amount due to 0 was +18.3 μC / g. 700 g of this developer and 350 g of toner 6 were each added to a developing machine equipped with a toner patch sensor (TPS) equipped with a toner hopper and a replenishing device with a feeder using a sponge roll, and evaluated for printing.

As a result, the image density was 1.41 and the fog was Hunter whiteness and the difference from the paper was 0.45. The image quality had no dust and no streak, and the halftone uniformity and gradation were good. Magnetic strength by MICR character is 1
At 20%, there were no changes from more than 20 leader passes. The stability of the developer was good, and sufficient developability was exhibited even in an environment of high temperature and high humidity or low temperature and low humidity. The output of the TPS sensor is also stable, and the fluctuation of toner concentration is 7 ±
0.5%. The printing durability was good, and no reduction in image density or increase in fog was observed even after printing 100k sheets. The amount of toner fixed on the carrier, that is, the amount of toner spent, was also small.

(Example 5) ・ Styrene-acrylic resin (St-2EHA, Tg 58 ° C., Tm 132 ° C.) 66 parts ・ Polyester resin (Tg 62 ° C., Tm 145 ° C.) 5 parts ・ Wax (manufactured by Hoechst) PP230 2 parts ・1 part of PE190 ・ 1 part of charge control agent N04 manufactured by Orient Chemical ・ 10 parts of magnetite (manufactured by Kanto Denka Kogyo) KBN400 10 parts ・ 15 parts of magnetic powder (manufactured by Toda Kogyo) MAT222 15 parts Toner 7 in the same manner as toner 6 using the above components Was manufactured. As the carrier, a coated carrier 7 was used in which a Cu-Zn-based ferrite carrier of 37 to 105 µm (average particle diameter 60 µm) was coated with 0.5% of a silicon-based resin in which conductive carbon black was mixed. Print evaluation was performed using a developer in which the toner 7 and the carrier 7 were adjusted to a toner concentration of 7 wt%. As a result, good development characteristics and magnetic strength were exhibited.

Comparative Example 6 The magnetic powder in the toner 7 was M
A toner 8 was obtained in the same manner as the toner 7, except that AT222 was changed to 35 parts. Printing evaluation was performed using toner 8 in the same manner as in Example 4. When the ratio of the magnetic powder is large, the residual magnetization of the toner is large, but at the time of development, the toner is attracted by the magnetic force of the magnet roller and the magnetic force on the magnetic brush, and the developability is reduced. As a result, toner replenishment increased, toner density increased, and fog increased.

Comparative Example 7 Printing was evaluated in the same manner as in Example 5 except that the carrier in Example 5 was changed to the carrier 8 without coating. In Comparative Example 7, the charge amount of the developer was small, and the developability was low. As a result, sufficient magnetic strength could not be obtained.

[0043]

[Table 2]

[0044]

According to the present invention, it is possible to obtain a high-definition MICR image with a stable magnetic intensity, to cope with high-speed printing, and to cope with a two-component developing system which consumes a relatively small amount of toner.

Claims (6)

[Claims] 1. A latent image on a latent image carrier, wherein a developer comprising at least a magnetic carrier and a toner is carried on a developer carrier having a means for generating a magnetic field therein and supplied to the latent image carrier. In the image forming method of developing, the toner contains at least a binder resin, a magnetic substance, and a wax,
Saturation magnetization of 25 emu / g or less, residual magnetization of 7 to 20 em
u / g and the triboelectric charge amount is −18 to −35 μC / g.
Wherein the magnetic carrier is coated with a resin. 2. A latent image on a latent image carrier, wherein a developer comprising at least a magnetic carrier and a toner is carried on a developer carrier having means for generating a magnetic field therein and supplied to the latent image carrier. In the image forming method of developing, the toner contains at least a binder resin, a magnetic substance, and a wax,
Saturation magnetization of 25 emu / g or less, residual magnetization of 7 to 20 em
u / g, a triboelectric charge amount of 9 to 22 μC / g, and the magnetic carrier is coated with a resin. 3. A latent image carrier comprising a developer comprising at least a resin-coated magnetic carrier and a toner carried on a developer carrier having means for generating a magnetic field therein and supplied to the latent image carrier. The toner used in the image forming method for developing the above latent image, comprising at least a binder resin, a magnetic substance, and a wax, and having a saturation magnetization of 2
A magnetic toner having a residual magnetization of 7 to 20 emu / g or less and a triboelectric charge of -18 to -35 [mu] C / g. 4. A latent image carrier comprising a developer comprising at least a resin-coated magnetic carrier and a toner carried on a developer carrier having means for generating a magnetic field therein and supplied to the latent image carrier. The toner used in the image forming method for developing the above latent image, comprising at least a binder resin, a magnetic substance, and a wax, and having a saturation magnetization of 2
A magnetic toner having a residual magnetization of 7 to 20 emu / g or less and a triboelectric charge of 9 to 22 μC / g. 5. A latent image on a latent image carrier by supplying a developer comprising at least a magnetic carrier and a toner to a developer carrier having a means for generating a magnetic field therein and supplying the developer to the latent image carrier. The developer used in the image forming method of developing, wherein the toner is at least a binder resin,
It contains a magnetic substance and wax, has a saturation magnetization of 25 emu / g or less, a residual magnetization of 7 to 20 emu / g, a triboelectric charge of -18 to -35 μC / g, and is characterized in that the magnetic carrier is resin-coated. Developer. 6. A latent image on a latent image carrier, wherein a developer comprising at least a magnetic carrier and a toner is carried on a developer carrier having a means for generating a magnetic field therein and supplied to the latent image carrier. The developer used in the image forming method of developing, wherein the toner is at least a binder resin,
It contains a magnetic material and wax, has a saturation magnetization of 25 emu / g or less, a residual magnetization of 7 to 20 emu / g, a triboelectric charge of 9 to 22 μC / g, and has a magnetic carrier coated with a resin. Developer.