JP2001281923A - Magnetic single-component developer and method for development using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide as magnetic signal-component developer and a method for the development using the developer by which sufficient image density is obtained and excellent image characteristics can be achieved without causing memory phenomenon. SOLUTION: The magnetic single-component developer consists of magnetic toner particles, silica particles (A) surface treated with silicone oil and having 100 to 150 m2/g BET specific surface area and silica particles (B) surface treated with a silane coupling agent and having 250 to 350 m2/g BET specific surface area, both silica particles being deposited on the surface of the magnetic toner particles. The weight ratio of the silica particles (A) to the silica particles (B) ranges 40:60 to 60:40. In the method for development, the obtained developer is carried on the surface of a nonmagnetic sleeve and transferred in a noncontact state to an electrostatic latent image held on the surface of a photoreceptor drum which is disposed to form a specified gap from the nonmagnetic sleeve.

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 the like, and a developing method thereof.

[0002]

2. Description of the Related Art In general, the electrophotographic method is to form a latent image electrically on a photoreceptor, develop the latent image with toner, and transfer a toner image 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 pressurization to obtain a copy. Developers used in such electrophotography include a two-component developer composed of a toner component and a carrier component, and a one-component developer having both functions of a toner and a carrier.

[0003] Two-component developers are excellent in electrophotographic properties 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. There were problems such as becoming complicated and complicated. Further, there is a problem that the two-component developer is easily deteriorated and its life is short.

[0004] In recent years, a developing method using a magnetic one-component developer which solves the problem of the two-component developer and achieves both simplification of the size of the developing device and electrophotographic characteristics has been proposed and put into practical use. In the method of developing a magnetic one-component developer, a magnetic one-component developer carried on a non-magnetic sleeve is brought into contact with a photoreceptor holding an electrostatic latent image so that the magnetic one-component developer is electrostatically latent. A contact-type magnetic one-component developing method in which the image is transferred to an image, and a fixed gap (gap) is provided between the non-magnetic sleeve carrying the magnetic one-component developer and the photoconductor holding the electrostatic latent image. ) Is provided, and the magnetic one-component developer is turned into an electrostatic latent image,
There is a non-contact magnetic one-component developing method in which development is performed by transferring (jumping) in a non-contact manner.

In the contact type magnetic one-component developing method, since the photoreceptor comes in contact with the magnetic one-component developer on the non-magnetic sleeve, the developability is good. However, the magnetic one-component developer receives not only the friction when agitated in the developing device but also the friction due to the contact with the photoreceptor, so that the mechanical burden 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 magnetic blade, the mechanical load on the magnetic one-component developer is small. However, in the case of the non-contact type, the development amount is generally inferior to that of the contact type, and a sufficient image density cannot be obtained, since the development requires an interval.

As a method for solving this problem, it has been studied to increase the amount of the magnetic one-component developer that has passed by increasing the distance between the non-magnetic sleeve and the magnetic blade in the developing device. However, when the amount of the magnetic one-component developer passing is increased in this manner, the electric charge is not sufficiently injected into the magnetic one-component developer by the magnetic blade, and the frictional charge amount of the magnetic one-component developer is insufficient. And the thin layer of the magnetic one-component developer on the surface of the non-magnetic sleeve was non-uniform. For this reason, when an original such as black solid or halftone is developed in a state where the thin layer of the magnetic one-component developer is non-uniform,
There is a problem that the image is blurred and the image density is insufficient. Further, when the non-magnetic sleeve is rotated by two or more rotations for development, the magnetic one-component developer remaining on the surface of the non-magnetic sleeve without completely transferring to the photoconductor at the time of the first rotation development is removed at the time of the second rotation development. There is a serious problem that a phenomenon of appearing as an afterimage, that is, a memory phenomenon occurs.

[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 obtaining excellent image characteristics without causing a problem of a memory phenomenon, and a developing method thereof. Is to provide.

[0008]

The magnetic one-component developer according to the present invention comprises silica particles (A) having a BET specific surface area of 100 to 150 m ² / g treated with silicone oil on the surface of magnetic toner particles. A magnetic one-component developer to which silica particles (B) having a BET specific surface area of 250 to 350 m ² / g surface-treated with a silane coupling agent are attached, wherein the silica particles (A) and the silica particles (B) Weight ratio of 4
0:60 to 60:40. Also,
The developing method according to the present invention is directed to a method of developing the electrostatic latent component held on the surface of a photosensitive drum provided with a certain gap from the non-magnetic sleeve. In a developing method in which the toner is transferred to an image in a non-contact manner, the magnetic one-component developer is applied on a surface of a magnetic toner particle by silica particles having a BET specific surface area of 100 to 150 m ² / g, which is surface-treated with silicone oil. (A) and a BET specific surface area surface-treated with a silane coupling agent is 2
A magnetic one-component developer having silica particles (B) of 50 to 350 m ² / g attached thereto, wherein the weight ratio of the silica particles (A) to the silica particles (B) is 40:60 to 60:40. It is characterized by the following.

[0009]

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

As the binder resin, for example, polystyrene, poly-p-chlorostyrene, polyvinyl toluene,
Styrene such as styrene-p-chlorostyrene copolymer and styrene-vinyltoluene copolymer, and homopolymers and their copolymers of substituted styrenes; styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer Copolymers of styrene and acrylic acid esters, such as styrene-acrylic acid-n-butyl copolymer;
Copolymers of styrene and methacrylate such as methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-methacrylic acid-n-butyl copolymer; styrene and acrylate and methacrylate Styrene-acrylonitrile copolymer, styrene vinyl methyl ether copolymer, styrene butadiene copolymer, styrene vinyl methyl ketone copolymer, styrene acrylonitrile indene copolymer, styrene-maleic ester Styrene copolymers of styrene such as copolymers with other vinyl monomers; polymethyl methacrylate, polybutyl methacrylate, polyester resin, polyvinyl acetate resin, polyamide resin, epoxy resin, polyvinyl butyral,
Examples include polyacrylic acid phenol resin, aliphatic or alicyclic hydrocarbon resin, petroleum resin, chlorinated paraffin, and the like. These can be used alone or in combination.

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

As the coloring agent, for example, the following pigments or dyes can be used. Carbon black, aniline blue (CINo. 50405), Riko oil blue (CINo.
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 (CINo. 74160), malachite green oxalate (CINo. 42000), lamp black (CINo. 77266), rose bengal (CINo. 45435) and mixtures thereof.

As the charge control agent, a positively chargeable magnetic one-component developer includes nigrosine dyes, metal salts of naphthenic acid and higher fatty acids, alkoxylated amines, quaternary ammonium salts, alkyd amides, phosphorus, tungsten , Molybdate lake pigments, fluorinated activators and the like.
As the negatively charged magnetic one-component developer, an electron-accepting organic complex, chlorinated paraffin, chlorinated polyester, polyester having an excess acid group, sulfonylamine of copper phthalocyanine, or the like is used.

The magnetic one-component developer of the present invention comprises: silica particles (A) having a BET specific surface area of 100 to 150 m ² / g obtained by treating the magnetic toner particles with silicone oil;
And a silica particle (B) having a BET specific surface area of 250 to 350 m ² / g surface-treated with a silane coupling agent. The silica particles (A) have a BET specific surface area of 100 to 150 m ² / g. 100m ²
When the value is smaller than / g, there is no effect of reducing the solid black memory and the halftone memory, and a sufficient image density cannot be obtained. On the other hand, when it is larger than 150 m ² / g, the developer adheres to the surface of the photoreceptor, causing the surface of the photoreceptor to be contaminated, and the effect of reducing halftone memory cannot be obtained.

The silica particles (B) have a BET specific surface area of 250 to 350 m ² / g. 250
If it is smaller than m ² / g, there is no effect of reducing the solid black memory, and a sufficient image density cannot be obtained. On the other hand, 350m
If it is larger than ² / g, the fluidity of the developer is deteriorated, the image density is reduced during continuous printing, and the effect of reducing halftone memory cannot be obtained. Silica particles (A)
And the BET specific surface area of the silica particles (B) are measured with a high-precision automatic gas adsorption device (manufactured by Nippon Bell Co., Ltd., trade name:
The measurement can be performed by using N ₂ gas as the adsorption gas in 8) and the like.

The silicone oil for treating the surface of the silica particles (A) includes dimethyl silicone oil, alkyl-modified silicone oil, α-methylstyrene-modified silicone oil, chlorophenyl silicone oil, fluorine-modified silicone oil and olefin-modified silicone oil. At least one selected from the group consisting of: Among them, dimethyl silicone oil is particularly preferable since it has the effect of reducing solid black memory and halftone memory and can achieve high transfer efficiency.

Examples of the silane coupling agent for treating the surface of the silica particles (B) include methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, tetramethoxysilane, methyltrimethoxysilane, Dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane, hexamethyldi Silazane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, β- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ -Aminopropyltriethoxysilane, N- (β
-Aminoethyl) -γ-aminopropyltrimethoxysilane, γ- (2-aminoethyl) -γ-aminopropylmethyldimethoxysilane, at least one selected from the group consisting of γ-anilinopropyltrimethoxysilane and the like. Can be mentioned. Among them, dimethyldichlorosilane is particularly preferable since it has a black solid memory and halftone memory reducing effect and can achieve high transfer efficiency.

The weight ratio of the silica particles (A) and the silica particles (B) to be adhered to the magnetic toner particles is from 40:60 to
It must be 60:40. When the weight ratio of the silica particles (A) is smaller than 40, the effect of reducing the halftone memory cannot be obtained, and the silica particles (A)
If the weight ratio is larger than 60, the effect of reducing black solid memory cannot be obtained.

As a method for attaching the silica particles (A) and the silica particles (B) to the surface of the magnetic toner particles, a method of adhering the silica particles (A), the silica particles (B) and the magnetic toner particles to 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 using a device called a surface reformer (Nara Hybridization System manufactured by Nara Machinery Co., Ltd., Ongmill manufactured by Hosokawa Micron Corporation). 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 state of being scattered, and according to the latter method, both particles (A) and (B) correspond to the magnetic toner particles. It adheres to the surface in a fixed state. The term “adhesion” as used in the present invention means both the state of glare and the state of adhesion.

The surface of the magnetic toner particles may be appropriately coated with magnetic powder, alumina, talc, clay, calcium carbonate, magnesium carbonate, titanium oxide to control the fluidity, chargeability, cleaning property and storage stability of the toner. Alternatively, an external additive 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 diagram of a developing device used in the method for developing a magnetic one-component developer of the present invention. This developing device is provided with a cylindrical photosensitive drum 1 serving as an electrostatic latent image holding member, a hopper 2 containing a magnetic one-component developer 3, and a certain gap with respect to the photosensitive drum 1. The right half circumference is stored in the hopper 2,
A non-magnetic sleeve 6 made of aluminum whose left half circumferential surface faces the photosensitive drum 1, a magnet roller 5 built in the non-magnetic sleeve 6, and a magnetic one-component developer 3 carried on the non-magnetic sleeve 6. The charging blade 4 for making the thickness of the layer 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 kept electrically conductive, A power supply 8 for applying an alternating bias voltage and a DC bias voltage to the body drum 1 is schematically configured. The gap between the non-magnetic sleeve 6 and the photosensitive drum 1 is about 50 to 400 μm.

The method for developing a magnetic one-component developer of the present invention using this developing device is performed 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 supply 8 to the photosensitive drum 1, the non-magnetic sleeve 6 and the photosensitive drum 1
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-described mechanism.

In general, a memory phenomenon is more likely to occur in a non-contact magnetic one-component developing method than in a two-component developing method. The memory phenomenon includes a solid black memory generated on a solid black and a halftone memory generated on a halftone formed by dots. As a result of the study by the present inventors, the memory phenomenon is caused by the fact that the developer remaining on the non-magnetic sleeve without jumping to the electrostatic latent image on the photosensitive drum surface and the developing layer newly on the non-magnetic sleeve surface from inside the hopper are added. It has been found that this phenomenon is caused by the difference in the triboelectric charge amount from the obtained developer. In order to solve this memory phenomenon, silica particles subjected to a silane coupling treatment having a BET specific surface area in the range of 250 to 350 m ² / g are added to improve the fluidity of the developer and reduce the black solid memory. Confirmed that it is effective. This is thought to be due to the improved fluidity of the developer, which reduces the friction (stress) of the developer remaining on the non-magnetic sleeve from the charging blade and prevents an unnecessary increase in the amount of frictional charge. Can be

With this method, however, although the solid black memory was greatly improved, the halftone memory could not be improved. In order to obtain the effect, it is premised that the silica particles are added in a certain amount or more, but if a sufficient amount is added, contamination of the photoreceptor due to the silica particles occurs. This is a magnetic one-component development method.
Since the magnetic powder used is harder than the photosensitive layer, the damage to the photoconductor is higher than that of the non-magnetic toner. In the case of a roller charging / transfer system that has been used recently, both rollers are in contact with the photoconductor, This is considered to be because silica particles, which are difficult to be removed, easily contaminate the photoreceptor through both rollers.

On the other hand, for the halftone memory, B
The use of silica oil-treated silica particles having an ET specific surface area of 100 to 150 m ² / g was effective. Since the silica particles are relatively large and have a smooth surface due to the silicone oil treatment, they are interposed between the magnetic toner particles on the sleeve and coagulate due to Coulomb force between the magnetic toner particles to reduce the charge between the toners. This is considered to be because the developer is easily jumped. The silica particles are effective in improving transfer efficiency. Further, since the particle size is large, there is an effect of polishing contaminants on the photoreceptor.
In the present invention, by using two kinds of different silica particles in combination, it is possible to eliminate black solid and halftone memory in the non-contact type magnetic one-component developing method, obtain good image characteristics, Thus, it was possible to provide a magnetic one-component developer which does not cause photoconductor contamination in printing.

[0026]

Hereinafter, the present invention will be described in more detail with reference to examples. In the following, “parts” means “parts by weight”
Is shown. <Example 1> [Preparation of Magnetic Toner Particles] Styrene-acrylate copolymer resin 57 parts (Mitsui Chemicals Co., Ltd .: CPR-100) Magnetite particles 38 parts (Toda Kogyo Co., Ltd., trade name: EPT-1000) ) Metal-containing dye 2 parts (Orient Chemical Industry Co., Ltd. Brand name: BONTRON)
S-34) Low molecular weight polypropylene wax 3 parts (Sanyo Kasei Kogyo Co., Ltd. product name: Viscol 330P) The raw materials having the above mixing ratios are mixed by a super mixer, hot melt kneaded by a twin screw kneader, and then pulverized by a jet mill. Thereafter, the powder was classified by a dry air classifier to obtain magnetic toner particles having a volume average particle diameter of 9.5 μm. [Preparation of Magnetic One-Component Developer] The above magnetic toner particles 100
And BET surface-treated with dimethyl silicone oil
0.5 parts of silica particles (A) having a specific surface area of 130 m ² / g and 0.5 parts of silica particles (B) having a BET specific surface area of 300 m ² / g surface-treated with dimethyldichlorosilane were mixed with a helical mixer. And the peripheral speed of the stirring blade is 30m
/ S for 5 minutes to obtain a magnetic one-component developer of the present invention.

Example 2 100 parts of the magnetic toner particles obtained in Example 1 and silica particles (A) having a BET specific surface area of 130 m ² / g treated with dimethyl silicone oil
0.4 parts and B treated with dimethyldichlorosilane
Silica particles (B) having an ET specific surface area of 300 m ² / g
6 parts were charged into a Henschel mixer, and mixed for 5 minutes at a peripheral speed of the stirring blade of 30 m / s to obtain a magnetic one-component developer of the present invention.

Example 3 100 parts of the magnetic toner particles obtained in Example 1 and silica particles (A) having a BET specific surface area of 130 m ² / g treated with dimethyl silicone oil
0.6 parts and B treated with dimethyldichlorosilane
Silica particles (B) having an ET specific surface area of 300 m ² / g
4 parts were charged into a Henschel mixer and mixed for 5 minutes at a peripheral speed of the stirring blade of 30 m / s to obtain a magnetic one-component developer of the present invention.

Comparative Example 1 100 parts of the magnetic toner particles obtained in Example 1 and silica particles (A) having a BET specific surface area of 130 m ² / g surface-treated with dimethyl silicone oil
0.5 part was charged into a Henschel mixer and mixed for 5 minutes at a peripheral speed of the stirring blade of 30 m / s to obtain a magnetic one-component developer for comparison.

Comparative Example 2 100 parts of the magnetic toner particles obtained in Example 1 and silica particles (A) having a BET specific surface area of 130 m ² / g treated with dimethyl silicone oil
1.0 part was charged into a Henschel mixer, and mixed for 5 minutes at a peripheral speed of the stirring blade of 30 m / s to obtain a magnetic one-component developer for comparison.

Comparative Example 3 100 parts of the magnetic toner particles obtained in Example 1 and silica particles (B) having a BET specific surface area of 300 m ² / g surface-treated with dimethyldichlorosilane
0.5 part was charged into a Henschel mixer and mixed for 5 minutes at a peripheral speed of the stirring blade of 30 m / s to obtain a magnetic one-component developer for comparison.

Comparative Example 4 100 parts of the magnetic toner particles obtained in Example 1 and silica particles (B) having a BET specific surface area of 300 m ² / g surface-treated with dimethyldichlorosilane.
1.0 part was charged into a Henschel mixer, and mixed for 5 minutes at a peripheral speed of the stirring blade of 30 m / s to obtain a magnetic one-component developer for comparison.

Comparative Example 5 100 parts of the magnetic toner particles obtained in Example 1 and silica particles (A) having a BET specific surface area of 130 m ² / g surface-treated with dimethyl silicone oil
0.3 parts and B treated with dimethyldichlorosilane
Silica particles (B) having an ET specific surface area of 300 m ² / g
7 parts were charged into a Henschel mixer, and mixed for 5 minutes at a peripheral speed of the stirring blade of 30 m / s to obtain a magnetic one-component developer for comparison.

Comparative Example 6 100 parts of the magnetic toner particles obtained in Example 1 and silica particles (A) surface-treated with dimethyl silicone oil and having a BET specific surface area of 130 m ² / g.
0.7 parts and B treated with dimethyldichlorosilane
Silica particles (B) having an ET specific surface area of 300 m ² / g
3 parts were charged into a Henschel mixer, and mixed for 5 minutes at a peripheral speed of the stirring blade of 30 m / s to obtain a magnetic one-component developer for comparison.

<Comparative Example 7> 100 parts of the magnetic toner particles obtained in Example 1, 0.5 parts of silica particles having a BET specific surface area of 50 m ² / g treated with dimethyl silicone oil, and a surface treated with dimethyldichlorosilane 0.5 parts of the treated silica particles (B) having a BET specific surface area of 300 m ² / g were charged into a Henschel mixer, and the peripheral speed of the stirring blade was 30 m.
/ S for 5 minutes to obtain a comparative magnetic one-component developer.

Comparative Example 8 100 parts of the magnetic toner particles obtained in Example 1 and 0.5 parts of silica particles having a BET specific surface area of 200 m ² / g treated with dimethyl silicone oil were used.
Parts and 0.5 parts of silica particles (B) having a BET specific surface area of 300 m ² / g, surface-treated with dimethyldichlorosilane, were charged into a Henschel mixer, and the peripheral speed of the stirring blade was 30.
The mixture was mixed for 5 minutes under the condition of m / s to obtain a magnetic one-component developer for comparison.

Comparative Example 9 100 parts of the magnetic toner particles obtained in Example 1 and silica particles (A) having a BET specific surface area of 130 m ² / g treated with dimethyl silicone oil were used.
0.5 parts of B treated with dimethyldichlorosilane
0.5 parts of silica particles having an ET specific surface area of 200 m ² / g were put into a Henschel mixer, and the peripheral speed of the stirring blade was 30
The mixture was mixed for 5 minutes under the condition of m / s to obtain a magnetic one-component developer for comparison.

Comparative Example 10 100 parts of the magnetic toner particles obtained in Example 1, 0.5 part of silica particles (A) having a BET specific surface area of 130 m ² / g treated with dimethyl silicone oil, and dimethyldiamine Silica particles having a BET specific surface area of 400 m ² / g treated with chlorosilane.
5 parts were charged into a Henschel mixer and mixed for 5 minutes at a peripheral speed of the stirring blade of 30 m / s to obtain a magnetic one-component developer for comparison.

Next, the following tests were carried out on the magnetic one-component developers of the above Examples and Comparative Examples. That is, using the magnetic one-component developer of the above-described example and the comparative example, the developing device as shown in FIG. 1 is used, and a commercially available magnetic one-component non-contact developing method using an organic photoreceptor is used. The document having the pattern shown in No. 2 was printed four times on a blank sheet, and then a separately prepared A4 size document whose entire surface was a solid black image was printed on an A4 size blank sheet. The document shown in FIG. 2 was printed four times on a blank sheet by the same printer, and then a separately prepared A4 size document having a halftone image on the entire surface was printed on an A4 size blank sheet. Then, the printed solid image and halftone image were evaluated for image density, solid black memory, and halftone memory. The results are shown in Table 1. In Table 1, the image density was obtained by measuring a black solid image portion of a blank sheet on which the original shown in FIG.
914.

The solid black memory was determined as follows. In the black solid image after the document of FIG. 2 is printed four times, the solid black portions 10a, 10b, 10c,
The part corresponding to 10d is the reflection density meter RD- made by Macbeth.
The measurement was made at 914, and the average value of the image densities at these four points was defined as A. On the other hand, the white portions 20a, 20b, 20c, 20 in FIG.
The part corresponding to d is a reflection densitometer RD-91 manufactured by Macbeth.
4, and the average value of the image densities at these four points is defined as B. Then, the value of (AB) was evaluated as a solid black memory. The halftone memory was obtained as follows. In the halftone image after the document of FIG. 2 is printed four times, the solid black portions 10a and 10b of FIG.
The portions corresponding to 10c and 10d were measured with a reflection densitometer RD-914 manufactured by Macbeth Co., and the average value of the image densities at these four points was defined as C. On the other hand, the white portions 20a, 20b, 20 in FIG.
c, 20d is a reflection density meter R made by Macbeth.
The average value of the image densities of these four points is measured as D-914. Then, the value of CD was evaluated as a halftone memory. As for the values of the solid black memory and the halftone memory, an image closer to 0 in absolute value indicates an image without a memory phenomenon, and 0.1 or less is a practically acceptable level.

Using the magnetic one-component developer of the example and the comparative example, continuous printing of 10,000 sheets was performed by the printer, and contamination and transfer efficiency on the photoreceptor surface after the continuous printing were confirmed. Are shown in Table 1. The photoreceptor contamination was visually observed on the surface of the photoreceptor after 10000 sheets. O indicates that there is no contamination, and X indicates a small amount of toner particles clumping on the photoreceptor surface and spots on the transfer paper image. XX indicates that a large amount of toner particles adhered to the surface of the photoreceptor and a large number of spots were generated on the transfer paper image. The transfer efficiency (%) was determined using the following equation.

[0042]

(Equation 1)

In the formula, A is the weight of the developer supply cartridge before printing, B is the weight of the developer recovery cleaning cartridge before printing, C is the weight of the developer supply cartridge after printing 10,000 sheets, D is 10,000
This is the weight of the developer collecting cleaning cartridge after printing one sheet.

[0044]

[Table 1]

As is clear from Table 1, the magnetic one-component developer of the present invention has an image density of 1.40 or more, and has little black solid memory and halftone memory.
There was no problem with photoconductor contamination and the transfer efficiency was 90% or more. On the other hand, all of the developers of Comparative Examples 1 to 10 generated more black solid memory or halftone memory than those of the examples. In Comparative Example 1, the image density was low, and the transfer efficiency was inferior to that of the Example. In Comparative Examples 3, 4, 5, 7, 8, 9, and 10, contamination on the photoreceptor surface occurred, and Comparative Examples 3 and 4 had low transfer efficiency.

[0046]

As described above, when the magnetic one-component developer of the present invention is applied to a non-contact type magnetic one-component developing apparatus, the problem of a black solid memory and a halftone memory can be solved. Even after printing, there is little contamination on the photoreceptor, and the transfer efficiency is superior to that of a conventional magnetic one-component developer.

[Brief description of the 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 an embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum, 3 ... Magnetic one-component developer, 6 ... Non-magnetic sleeve

Claims (4)

[Claims] A BET specific surface area of a surface of magnetic toner particles treated with silicone oil is 100 to 150 m.
² / g of silica particles (A) and a BET specific surface area treated with a silane coupling agent having a BET specific surface area of 250 to 350 m ² / g
A magnetic one-component developer having silica particles (B) attached thereto, wherein the weight ratio of the silica particles (A) to the silica particles (B) is 40:60 to 60:40. One-component developer. 2. The magnetic one-component developer according to claim 1, wherein the silicone oil is dimethyl silicone oil. 3. The magnetic one-component developer according to claim 1, wherein the silane coupling agent is dimethyldichlorosilane. 4. A method according to claim 1, wherein the magnetic one-component developer carried on the surface of the non-magnetic sleeve is transferred to an electrostatic latent image held on the surface of a photosensitive drum provided with a predetermined gap from the non-magnetic sleeve. In a developing method of performing development by transferring the toner in a non-contact manner, the magnetic one-component developer is applied to a surface of a magnetic toner particle by silica particles having a BET specific surface area of 100 to 150 m ² / g (A) treated with silicone oil. ) And a BET specific surface area treated with a silane coupling agent of 250
A magnetic one-component developer to which silica particles (B) having a particle size of from 350 to 350 m ² / g are attached, wherein the weight ratio of the silica particles (A) to the silica particles (B) is from 40:60 to 60:40. A developing method characterized by the above-mentioned.