JP3485861B2 - Magnetic one-component developer and developing method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic one-component developer used in electrophotography and a developing method thereof.

[0002]

2. Description of the Related Art Generally, electrophotography is a method in which a latent image is electrically formed on a photoconductor, the latent image is developed with a toner, and the toner image is transferred to a transfer material such as paper as required. After that, the toner image is fixed on the transfer material by means such as heating and pressing to obtain a copy. Developers used in such an electrophotographic method include a two-component developer including a toner component and a carrier component, and a one-component developer having both the functions of the toner and the carrier.

The two-component developer is excellent in electrophotographic characteristics such as transferability, fixability and environmental resistance. However, since it is necessary to control the mixing ratio of the toner component and the carrier component, a toner concentration sensor is required in the developing device, and a stirring mechanism for stirring the toner component and the carrier component is required. It had problems such as becoming complicated and complicated. Further, the two-component developer is prone to deterioration and has a problem that the life is short.

In recent years, there has been proposed and put into practical use a developing method using a magnetic one-component developer which has improved the problem of the above-mentioned two-component developer and made the developing device compact and simple and has electrophotographic characteristics. To develop a magnetic one-component developer, the magnetic one-component developer is carried by contacting the magnetic one-component developer carried on a non-magnetic sleeve with a photoreceptor carrying an electrostatic latent image. A contact type magnetic one-component developing method in which the image is transferred to the image for development and a non-magnetic sleeve carrying the magnetic one-component developer and the photoconductor holding the electrostatic latent image have a constant gap (gap). ) Is provided, and the magnetic one-component developer is used as an electrostatic latent image,
There is a non-contact type magnetic one-component developing method in which development is performed by non-contact transfer (jumping).

In the contact-type magnetic one-component developing method, the developing property is good because the magnetic one-component developer on the non-magnetic sleeve comes into contact with the photoreceptor. However, the magnetic one-component developer receives not only friction when it is agitated in the developing device, but also friction caused by contact with the photoconductor, so that the mechanical load on the magnetic one-component developer increases. there were. On the other hand, in the non-contact type magnetic one-component developing method,
Since the magnetic one-component developer is frictionally charged only by the charging blade, the mechanical load on the magnetic one-component developer is small. However, in the case of the non-contact type, the amount of development is generally inferior to that of the contact type, and a sufficient image density cannot be obtained, because the interval is involved in the development.

As a method for solving this problem, it has been considered to increase the distance between the non-magnetic sleeve and the charging blade to increase the passage amount of the magnetic one-component developer in the developing device. However, when the passing amount of the magnetic one-component developer is increased in this way, the charge is not sufficiently injected into the magnetic one-component developer by the charging blade, and the triboelectric charge amount of the magnetic one-component developer becomes insufficient. The thin layer of the magnetic one-component developer on the surface of the non-magnetic sleeve was uneven. Therefore, when a document such as a black solid image or a halftone image is developed with a thin layer of the magnetic one-component developer being non-uniform, there is a problem in that the image is blurred and the image density is insufficient. Also, when the non-magnetic sleeve is developed by rotating it for two or more turns, the magnetic one-component developer remaining on the surface of the non-magnetic sleeve during the second turn is not completely transferred to the photoconductor during the first turn. The phenomenon of appearing as an afterimage,
That is, there was a serious problem that a memory phenomenon occurred.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a magnetic one-component developer capable of obtaining a sufficient image density and excellent image characteristics without causing a memory phenomenon, and a developing method thereof. To provide.

[0008]

The magnetic one-component developer of the present invention has a BET specific surface area of 100 to 300 m ² / g having the same polarity as the magnetic toner particles on the surface of the magnetic toner particles.
Of the silica toner (A) and the silica particles (B) having a BET specific surface area of 40 to 90 m ² / g having a polarity opposite to that of the magnetic toner particles. ) And silica particles (B) in a weight ratio of 95: 5.
˜50: 50. Further, in the developing method of the present invention, the magnetic one-component developer carried on the surface of the non-magnetic sleeve is retained on the surface of the photoconductor drum which is installed with a certain gap from the non-magnetic sleeve. In a developing method of transferring to an electrostatic latent image in a non-contact manner for development, the magnetic one-component developer has a BET specific surface area of 100 to 300 m ² having the same polarity as the magnetic toner particles on the surface of the magnetic toner particles. / G of silica particles (A) and the BET specific surface area having a polarity opposite to that of the magnetic toner particles are 40 to
A magnetic one-component developer having 90 m ² / g of silica particles (B) attached, wherein the weight ratio of the silica particles (A) to the silica particles (B) is 95: 5 to 50:50. Characterize.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The magnetic toner particles used in the present invention contain at least a binder resin and a magnetic material, and if necessary, a colorant, a charge control agent and the like. The volume average particle diameter of the magnetic toner is not particularly limited, but is preferably 5 to 20 μm.
m.

Examples of the binder resin include polystyrene, poly-p-chlorostyrene, polyvinyltoluene,
Styrenes such as styrene-p-chlorostyrene copolymers and styrene-vinyltoluene copolymers, homopolymers of styrene and its substitution products and copolymers thereof; styrene-methyl acrylate copolymers, styrene-ethyl acrylate copolymers Copolymers of styrene and acrylates such as polymer, styrene-n-butyl acrylate copolymer; styrene-
Copolymers of styrene and methacrylic acid ester such as methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-methacrylic acid-n-butyl copolymer; styrene and acrylic acid ester and methacrylic acid ester Other styrene copolymers; styrene-acrylonitrile copolymer, styrene vinyl methyl ether copolymer, styrene butadiene copolymer, styrene vinyl methyl ketone copolymer, styrene acrylonitrile indene copolymer, styrene-maleic acid ester Styrene-based copolymers of styrene and other vinyl-based monomers such as copolymers; polymethyl methacrylate, polybutyl methacrylate, polyester resins, polyvinyl acetate resins, polyamide resins, epoxy resins, polyvinyl butyral,
Examples thereof include polyacrylic acid phenol resin, aliphatic or alicyclic hydrocarbon resin, petroleum resin, and chlorinated paraffin. These can be used alone or as a mixture.

As the magnetic substance, for example, cobalt, iron,
Metals such as nickel, aluminum, copper, nickel, magnesium, tin, zinc, gold, silver, selenium, titanium, tungsten, zirconium and other metals, aluminum oxide, iron oxide, metal oxides such as nickel oxide, Ferromagnetic ferrite, magnetite or mixtures thereof are used. The average particle size of the magnetic substance is not particularly limited, but is preferably 0.05 to 3 μm. The content of the magnetic substance is not particularly limited, but is preferably 65% by weight or less in the magnetic toner particles.

As the colorant, for example, the following pigments or dyes can be used. Carbon black, aniline blue (CI No.50405), power ruco oil blue (CI No.
azoec Blue 3), Chrome Yellow (CINo.14090), Ultramarine Blue (CINo.77103), DuPont Oil Red (CINo.26105), Orient Oil Red # 330.
(CINo.47005), Methylene blue chloride (CINo.52
015), phthalocyanine blue (CI No.74160), malachite green oxalate (CI No.42000), lamp black (CI No.77266), rose bengal (CI No.45435) and mixtures thereof.

As the charge control agent, positively charged magnetic one-component developers include nigrosine dyes, metal salts of naphthenic acid and higher fatty acids, alkoxylated amines, quaternary ammonium salts, alkyd amides, phosphorus and tungsten. , Molybdate lake pigments, fluorinated activators, etc. are used.
An electron-accepting organic complex, chlorinated paraffin, chlorinated polyester, polyester having excess acid groups, sulfonylamine of copper phthalocyanine and the like are used for the negatively charged magnetic one-component developer.

The magnetic one-component developer of the present invention comprises silica particles (A) having a BET specific surface area of 100 to 300 m ² / g, which has the same polarity as the magnetic toner particles.
And silica particles (B) having a BET specific surface area of 40 to 90 m ² / g, which has a polarity opposite to that of the magnetic toner particles. BET specific surface area of silica particles (A) is 1
If it is less than 00 m ² / g, sufficient image density cannot be obtained. On the other hand, when it is larger than 300 m ² / g, the halftone memory reduction effect cannot be obtained,
Sufficient image density cannot be obtained.

When the BET specific surface area of the silica particles (B) is less than 40 m ² / g, the effect of reducing black solid memory and halftone memory cannot be obtained. on the other hand,
When it is larger than 90 m ² / g, the silica particles (B) are likely to be buried in the surface of the magnetic toner particles, so that the triboelectric charge amount of the magnetic toner particles cannot be improved and, as a result, a black solid memory and a halftone memory are obtained. It is impossible to obtain the effect of reducing the image density and a sufficient image density. The BET specific surface areas of the silica particles (A) and the silica particles (B) are high-precision automatic gas adsorption devices (product name: BELSO manufactured by Nippon Bell Co., Ltd.).
It can be measured by using N ₂ gas as an adsorption gas in RP28) or the like.

Silica particles (A) and silica particles (B)
Can selectively adjust the polarity with respect to the magnetic toner particles by selectively using a surface treatment agent. As the surface treatment agent for increasing the negative chargeability of the silica particles, among silane coupling agents and titanium coupling agents, those having a functional group showing negative chargeability can be preferably used.
For example, γ-chloropropyltrimethoxysilane, γ-
Glycidoxypropyltrimethoxysilane, β- (3,4-
Epoxycyclohexyl) ethyltrimethoxysilane,
Examples include alkylchlorotitanium coupling agents. Further, examples of the surface treatment agent for increasing the positive chargeability of the silica particles include an aminosilane coupling agent, and examples thereof include γ-aminopropyltriethoxysilane and N- (β-aminoethyl) -γ-aminopropyl. Examples thereof include trimethoxysilane, γ-anilinopropyltrimethoxysilane, and polyethyleneimine-containing silane.

The polarity of silica particles with respect to magnetic toner particles can be determined as follows. 1 g of magnetic toner particles and non-coated ferrite particles 49
20 to 22 ° C / g in a 200cc glass container
It is left for 12 hours or more in an environment of 60 to 65% RH. Next, after stirring the glass container with a constant speed stirrer at 80 rpm for 5 minutes, the triboelectric charge amount of the magnetic toner particles was measured three times with a blow-off triboelectric charge amount measuring device, and the average value thereof was obtained. Next, in the above, the triboelectric charge amount of the silica particles is determined in the same manner except that silica particles are used instead of the magnetic toner particles. The polarity of the silica particles with respect to the magnetic toner particles can be determined from the triboelectric charge amount of the magnetic toner particles and the silica particles obtained above.

The weight ratio of the silica particles (A) and the silica particles (B) attached to the magnetic toner particles is 95: 5-5.
Must be 0:50. When the weight ratio of the silica particles (A) is larger than 95, the effect of reducing the black solid memory and the halftone memory cannot be obtained,
When the weight ratio of the silica particles (A) is less than 50,
The effect of reducing the halftone memory cannot be obtained.

As a method of adhering the silica particles (A) and the silica particles (B) to the surface of the magnetic toner particles, the silica particles (A), the silica particles (B) and the magnetic toner particles are mixed with a turbine type stirrer, a Henschel mixer, There is a method of stirring using a general stirrer such as a super mixer, or a method of using a device called a surface reformer (Nara Hybridization System manufactured by Nara Machinery Co., Ltd., Ong Mill manufactured by Hosokawa Micron Co., Ltd.). According to the former method, the silica particles (A) and the silica particles (B) adhere to the surface of the magnetic toner particles in a sprinkled state, and by the latter method, both particles (A) and (B) are It adheres to the surface in a fixed state. The term “adhesion” as used in the present invention means both the state of the glaze and the state of fixation.

Further, on the surface of the magnetic toner particles, magnetic powder, alumina, talc, clay, calcium carbonate, magnesium carbonate, titanium oxide are appropriately added to control the fluidity, charging property, cleaning property and storage property of the toner. Alternatively, external additives such as various resin fine particles may be attached.

Next, the developing method of the present invention using the above magnetic one-component developer will be described. FIG. 1 is a schematic view of a developing device used in the method for developing a magnetic one-component developer of the present invention. This developing device is installed with a cylindrical photosensitive drum 1 serving as an electrostatic latent image holder, a hopper 2 containing a magnetic one-component developer 3, and a constant gap with respect to the photosensitive drum 1. The right half circumference is stored in the hopper 2,
The non-magnetic sleeve 6 made of aluminum whose left half peripheral surface faces the photoconductor drum 1, the magnet roller 5 contained in the non-magnetic sleeve 6, and the magnetic one-component developer 3 carried by the non-magnetic sleeve 6. The charging blade 4 for making the layer thickness uniform, the stirrer 7 for stirring the magnetic one-component developer 3 in the hopper 2, the non-magnetic sleeve 6 and the charging blade 4 are electrically connected to each other, The body drum 1 is provided with a power source 8 for applying an alternating bias voltage and a DC bias voltage, and is generally configured. The gap between the non-magnetic sleeve 6 and the photosensitive drum 1 is about 50 to 400 μm.

The developing method of the magnetic one-component developer of the present invention using this developing apparatus is carried out as follows. First,
An electrostatic latent image is formed on the surface of the photosensitive drum 1 by a known electrophotographic method. On the other hand, the magnetic one-component developer 3 in the hopper 2 is carried by the charging blade 4 on the surface of the non-magnetic sleeve 6 containing the magnet roller 5 so as to have a constant layer thickness, and is conveyed. Here, by applying an alternating bias voltage and a DC bias voltage from the power source 8 to the photosensitive drum 1, the non-magnetic sleeve 6 and the photosensitive drum 1 are
A DC electric field and an AC electric field are generated between the two, and the magnetic one-component developer 3 on the surface of the non-magnetic sleeve 6 is jumped and developed into an electrostatic latent image on the surface of the photosensitive drum 1. The developing method of the present invention uses the magnetic one-component developer as the magnetic one-component developer in the developing device having the above mechanism.

Generally, the memory phenomenon is more likely to occur in the non-contact type magnetic one-component developing method as compared with the two-component developing method. There are two types of memory phenomena: solid black memory that occurs on solid black and halftone memory that occurs on halftone formed by dots. As a result of a study conducted by the present inventor, the above memory phenomenon was found in the developer remaining on the non-magnetic sleeve without jumping to the electrostatic latent image on the surface of the photosensitive drum, and on the developing layer newly on the surface of the non-magnetic sleeve from inside the hopper. It was found that this is a phenomenon that occurs because of the difference in the triboelectric charge amount with the added developer. In order to solve this memory phenomenon, in the present invention, silica particles (A) having the same polarity as the magnetic toner particles and a BET specific surface area of 100 to 300 m ² / g, and B having the opposite polarity to the magnetic toner particles.
Silica particles (B) having an ET specific surface area of 40 to 90 m ² / g
And are included. Silica of the same polarity (A)
Has the effect of improving the fluidity of the developer and reducing the black solid memory, while silica (B) of opposite polarity is interposed between the magnetic toner particles to reduce the toner-to-toner charge and to the developer. By reducing the friction (stress) from the charging blade, it is presumed that the frictional electrification amount is prevented from being increased more than necessary, and as a result, the developer is easily jumped and the halftone memory is reduced. In the present invention, by using two kinds of different silica particles as described above in combination, black solid and halftone memory can be eliminated in the non-contact type magnetic one-component developing method, and good image characteristics can be obtained, It was possible to provide a magnetic one-component developer having a sufficient image density even in the continuous printing of a large number of sheets.

[0024]

EXAMPLES The present invention will be described in more detail based on the following examples.
Explained. In the following, "parts" means "parts by weight"
Indicates. <Example 1> [Preparation of magnetic toner particles] Styrene-acrylic ester copolymer resin 57 parts (Mitsui Chemicals, Inc. product name: CPR-100) Magnetite particles 38 parts (Toda Kogyo Co., Ltd. product name: EPT-1000) Metallic dye 2 parts (Product name by Orient Chemical Industry: BONTRON
S-34) Low molecular weight polypropylene wax 3 parts (Product name of Sanyo Kasei Co., Ltd .: Viscole 330P) Mix the raw materials with the above mixing ratio with a super mixer
And then melt-kneading with a twin-screw kneader and crushing with a jet mill.
Then, classify with a dry airflow classifier to obtain a volume average particle size.
Magnetic toner particles of 9.5 μm were obtained. This magnetic toner grain
The child has a negative charging property to the uncoated ferrite particles.
Was there. [Preparation of magnetic one-component developer] The above magnetic toner particles 100
And γ-glycid having the same polarity as the magnetic toner particles
BET surface-treated with xypropyltrimethoxysilane
Specific surface area is 200m ²/ G silica particles (A) 0.5 part
And a γ-aminopropionate having a polarity opposite to that of the magnetic toner particles.
BET specific surface area surface-treated with pyrtriethoxysilane
Is 50m²/ G silica particles (B) 0.3 parts
It is put into an oil mixer and the peripheral speed of the stirring blade is 30 m / s.
The magnetic one-component developer of the present invention is obtained by mixing for 5 minutes under the conditions.
It was

<Example 2> A magnetic one-component developer of the present invention was obtained in the same manner as in Example 1 except that the content of the silica particles (B) having a polarity opposite to that of the magnetic toner particles was 0.1 part. It was

<Example 3> A magnetic one-component developer of the present invention was obtained in the same manner as in Example 1 except that the content of the silica particles (B) having a polarity opposite to that of the magnetic toner particles was 0.5 part. It was

Example 4 100 parts of the magnetic toner particles obtained in Example 1 and γ-having the same polarity as the magnetic toner particles.
Silica particles (A) having a BET specific surface area of 120 m ² / g surface-treated with glycidoxypropyltrimethoxysilane
BET surface-treated with 0.5 parts of γ-aminopropyltriethoxysilane having a polarity opposite to that of the magnetic toner particles
0.3 part of silica particles (B) having a specific surface area of 80 m ² / g was charged into a Henschel mixer, and the peripheral speed of the stirring blade was 30.
The magnetic one-component developer of the present invention was obtained by mixing for 5 minutes under the condition of m / s.

Example 5 100 parts of the magnetic toner particles obtained in Example 1 and γ-having the same polarity as the magnetic toner particles.
Silica particles (A) having a BET specific surface area of 300 m ² / g surface-treated with glycidoxypropyltrimethoxysilane
BET surface-treated with 0.5 parts of γ-aminopropyltriethoxysilane having a polarity opposite to that of the magnetic toner particles
0.3 part of silica particles (B) having a specific surface area of 80 m ² / g was charged into a Henschel mixer, and the peripheral speed of the stirring blade was 30.
The magnetic one-component developer of the present invention was obtained by mixing for 5 minutes under the condition of m / s.

Comparative Example 1 A magnetic one-component developer for comparison was obtained in the same manner as in Example 1, except that silica particles having the opposite polarity to the magnetic toner particles were not attached.

Comparative Example 2 A magnetic one-component developer for comparison was obtained in the same manner as in Example 1 except that silica particles having the same polarity as the magnetic toner particles were not attached.

Comparative Example 3 In Example 1, silica particles having the same polarity as the magnetic toner particles, surface-treated with γ-glycidoxypropyltrimethoxysilane, having a BET specific surface area of 50 m ² / g. A magnetic single-component developer for comparison was obtained in the same manner except that parts were used.

Comparative Example 4 In Example 1, silica particles having the same polarity as the magnetic toner particles, surface-treated with γ-glycidoxypropyltrimethoxysilane, having a BET specific surface area of 340 m ² / g. A magnetic single-component developer for comparison was obtained in the same manner except that parts were used.

<Comparative Example 5> In Example 1, the BET specific surface area which is surface-treated with γ-aminopropyltriethoxysilane as silica particles having a polarity opposite to that of the magnetic toner particles is 1
A comparative magnetic one-component developer was obtained in the same manner except that 0.3 part of 20 m ² / g silica particles was used.

<Comparative Example 6> In Example 1, the BET specific surface area which is surface-treated with γ-aminopropyltriethoxysilane as silica particles having a polarity opposite to that of the magnetic toner particles is 3
A comparative magnetic one-component developer was obtained in the same manner except that 0.3 part of 5 m ² / g silica particles was used.

Comparative Example 7 In Example 1, the content of the silica particles (B) having a polarity opposite to that of the magnetic toner particles was 0.7 part (the weight ratio of the silica particles (A) and the silica particles (B) was Four
A magnetic one-component developer for comparison was obtained in the same manner except that the ratio was 1.6: 58.3).

Next, the following tests were carried out on the magnetic one-component developers of the above Examples and Comparative Examples. That is, the magnetic one-component developer of the above-described Examples and Comparative Examples is used to have a developing device configuration as shown in FIG. 1 and a commercially available magnetic one-component non-contact developing method printer using an organic photoconductor is used. An original having a pattern shown in 2 was printed on a blank sheet of paper 4 times, and then a separately prepared A4 size original having a solid black image was printed on an A4 size blank sheet. Further, the original of FIG. 2 was printed on a blank sheet of paper 4 times by the same printer, and then a separately prepared A4 size original having a halftone image was printed on an A4 size blank sheet. The image density, black solid memory, and halftone memory of the printed solid black image and halftone image were evaluated. The results are shown in Table 1. In Table 1, the image density is the reflection densitometer RD- manufactured by Macbeth Co., Ltd. for the black solid image portion of the white paper on which the original of FIG. 2 is printed for the first time.
It is the value measured at 914.

The black solid memory was determined as follows. In the solid black image after the original document of FIG. 2 has been printed four times, the solid black portions 10a, 10b, 10c of FIG.
The part suitable for 10d is a reflection densitometer RD- manufactured by Macbeth.
The average value of the image densities at these four points was defined as A. On the other hand, the white parts 20a, 20b, 20c, 20 of FIG.
The portion matching d is the reflection densitometer RD-91 manufactured by Macbeth.
4 and the average value of the image densities at these four points is designated as B. Then, the value of A-B was evaluated as a black solid memory. The halftone memory was obtained as follows. In the halftone image after printing the original document of FIG. 2 four times, the black solid portions 10a, 10b, 10 of FIG.
The part that matches c and 10d is a reflection densitometer R manufactured by Macbeth
It was measured by D-914, and the average value of the image densities at these four points was defined as C. On the other hand, the white parts 20a, 20b, 20c of FIG.
A portion suitable for 20d is a reflection densitometer RD- manufactured by Macbeth.
The average value of the image densities at these four points is defined as D. Then, the value of CD was evaluated as a halftone memory. The values of the black solid memory and the halftone memory are images having no memory phenomenon as the absolute value is closer to 0, and both values of 0.1 or less are practically no problem.

Further, using the magnetic one-component developers of Examples and Comparative Examples, 10000 sheets were continuously printed by the printer, the transfer efficiency after continuous printing was confirmed, and the results are shown in Table 1. The transfer efficiency (%) was calculated using the following formula.

[0039]

[Equation 1]

In the formula, A is the weight of the developer replenishing cartridge before printing, B is the weight of the developer collecting cleaning cartridge before printing, C is the weight of the developer replenishing cartridge after printing 10,000 sheets, and D is D. 10,000
It is the weight of the cleaning cartridge for collecting the developer after printing one sheet.

[0041]

[Table 1]

As is clear from Table 1, the magnetic one-component developer of the present invention has an image density of 1.36 or more, and has little black solid memory and halftone memory.
The transfer efficiency was 87% or more. On the other hand, in all the developers of Comparative Examples 1 to 7, more black solid memories or halftone memories were generated than in the examples. Further, the image density was low in Comparative Examples 2 to 5, and the transfer efficiency was lower in Comparative Examples 1, 4 and 6 than in the Examples.

[0043]

As described above, the magnetic one-component developer of the present invention solves the problems of black solid memory and halftone memory when applied to a non-contact type magnetic one-component developing device, and can be used for a large number of sheets. Even after printing, there is little contamination on the photoconductor, and transfer efficiency is superior to conventional magnetic one-component developers.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a developing device used in a non-contact type magnetic one-component developing method.

FIG. 2 is a diagram showing an image pattern used for image evaluation in Examples.

[Explanation of symbols]

1 ... Photosensitive drum, 3 ... Magnetic one-component developer, 6 ... Non-magnetic sleeve

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03G 9/08

Claims (2)

(57) [Claims] 1. A BET specific surface area of 100 to 300 having the same polarity as the magnetic toner particles on the surface of the magnetic toner particles.
and m ² / g of silica particles (A), a magnetic one-component developer BET specific surface area is attached is 40~90m ² / g of silica particles (B) having an opposite polarity and magnetic toner particles,
A magnetic one-component developer characterized in that the weight ratio of the silica particles (A) to the silica particles (B) is 95: 5 to 50:50. 2. A magnetic one-component developer carried on the surface of a non-magnetic sleeve is converted into an electrostatic latent image held on the surface of a photoconductor drum which is installed with a certain gap from the non-magnetic sleeve. In the developing method of non-contact transfer and development, the magnetic one-component developer has a BET specific surface area of 100 to 300 m ² / g having the same polarity as the magnetic toner particles on the surface of the magnetic toner particles. The particle (A) has a BET specific surface area of 40 to 40, which has a polarity opposite to that of the magnetic toner particle.
A magnetic one-component developer having 90 m ² / g of silica particles (B) attached, wherein the weight ratio of the silica particles (A) to the silica particles (B) is 95: 5 to 50:50. Characteristic development method.