JP3495313B2 - 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 comprises silica particles (A) having a BET specific surface area of 100 to 150 m ² / g surface-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) are Weight ratio is 4
It is characterized by being 0:60 to 60:40. Also,
The developing method of the present invention is a method in which a magnetic one-component developer carried on the surface of a non-magnetic sleeve is charged with 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 transferring to an image in a non-contact manner to perform development, the magnetic one-component developer is a silica particle having a BET specific surface area of 100 to 150 m ² / g whose surface is treated with silicone oil on the surface of the magnetic toner particle. (A) and the BET specific surface area which is surface-treated with a silane coupling agent is 2
A magnetic one-component developer having 50 to 350 m ² / g of silica particles (B) attached, and the weight ratio of the silica particles (A) to the silica particles (B) is 40:60 to 60:40. It is characterized by

[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 150 m ² / g obtained by surface-treating the magnetic toner particles with silicone oil.
The silica particles (B) having a BET specific surface area of 250 to 350 m ² / g surface-treated with a silane coupling agent are contained. The silica particles (A) have a BET specific surface area of 100 to 150 m ² / g. 100 m ²
When it is less than / g, the effect of reducing the black solid memory and the halftone memory is not obtained, and 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 photoconductor to contaminate the surface of the photoconductor, and the halftone memory reducing effect cannot be obtained.

The silica particles (B) have a BET specific surface area of 250 to 350 m ² / g. 250
When it is smaller than m ² / g, the effect of reducing the black solid memory is not obtained, and sufficient image density cannot be obtained. On the other hand, 350m
^When it is larger than ² / g, the fluidity of the developer is deteriorated, the image density is lowered during continuous printing, and the halftone memory reducing effect cannot be obtained. Silica particles (A)
The BET specific surface area of the silica particles (B) is a high-precision automatic gas adsorption device (trade name BELSORP2 manufactured by Nippon Bell Co., Ltd.).
It can be measured 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) is selected from 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 Of these, dimethyl silicone oil is particularly preferable because it has the effect of reducing black solid memory and halftone memory, and high transfer efficiency can be obtained.

As the silane coupling agent for treating the surface of the silica particles (B), methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltriethoxysilane meth silane, decyl trimethoxy silane-hexa Methyldisilazane, 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, γ-anilinopropyltrimethoxysilane, and the like. Can be mentioned. Of these, dimethyldichlorosilane is particularly preferable because it has the effect of reducing black solid memory and halftone memory and high transfer efficiency can be obtained.

The weight ratio of the silica particles (A) and the silica particles (B) attached to the magnetic toner particles is 40:60 to.
It should be 60:40. If the weight ratio of the silica particles (A) is less 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 the solid black 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 the study by the present inventor, the memory phenomenon was caused by the developer remaining on the non-magnetic sleeve without jumping to the electrostatic latent image on the surface of the photoconductor drum and 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 due to the difference in the triboelectric charge amount from the developed developer. Then, in order to solve this memory phenomenon, silica particles treated with silane coupling 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. It was confirmed to be effective. It is thought that this is because the fluidity of the developer is improved, which reduces the friction (stress) from the charging blade on the developer remaining on the non-magnetic sleeve and prevents the triboelectric charge amount from increasing more than necessary. To be

However, although the black solid memory is greatly improved by this method, the halftone memory cannot be improved. Further, in order to obtain the effect, it is premised that the silica particles are added in a certain amount or more. However, if a sufficient amount is added, contamination of the photoreceptor due to the silica particles will occur. In the case of the magnetic one-component development method,
Since the magnetic powder used is harder than the photosensitive layer, it causes more damage to the photoconductor than non-magnetic toner. In the case of the roller charging / transfer system used in recent years, both rollers are in contact with the photoconductor and cleaning is performed. It is considered that this is because the silica particles, which are difficult to remove, easily contaminate the photoconductor through both rollers.

On the other hand, for the halftone memory, B
It was effective to use silica particles treated with silicone oil having an ET specific surface area of 100 to 150 m ² / g. Since the silica particles are relatively large and have a smooth surface due to the silicone oil treatment, they intervene between the magnetic toner particles on the sleeve, and the aggregation of the magnetic toner particles due to the Coulomb force is reduced in order to reduce the charge between the toner particles. It is considered that this is because the developer is easily prevented and the developer is easily jumped. The silica particles are effective in improving transfer efficiency. Further, since the particle size is large, it is effective in polishing contaminants to the photoconductor.
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 and obtain good image characteristics, and to obtain a large number of continuous sheets. It was possible to provide a magnetic one-component developer that does not cause contamination of the photoreceptor even in printing.

[0026]

The present invention will be described in more detail based on the following examples. In the following, "parts" means "parts by weight"
Indicates. <Example 1> [Production of magnetic toner particles] Styrene-acrylic acid ester copolymer resin 57 parts (Mitsui Chemicals, Inc. product name: CPR-100) Magnetite particles 38 parts (Toda Kogyo product name: EPT-1000) ) Metallic dye 2 parts (product name: BOTRON manufactured by Orient Chemical Industry Co., Ltd.)
S-34) Low molecular weight polypropylene wax 3 parts (manufactured by Sanyo Kasei Kogyo Co., Ltd .: trade name: Viscole 330P) The raw materials having the above mixing ratios are mixed in a super mixer, hot-melt kneaded in a twin-screw kneader, and then ground in a jet mill. Then, the particles were classified by a dry airflow classifier to obtain magnetic toner particles having a volume average particle size of 9.5 μm. [Preparation of magnetic one-component developer] The above magnetic toner particles 100
Parts and BET surface-treated with dimethyl silicone oil
Henschel mixer comprising 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. The peripheral speed of the stirring blade is 30 m
/ S was mixed for 5 minutes to obtain the 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 surface-treated with dimethyl silicone oil.
0.4 parts and B surface-treated with dimethyldichlorosilane
Silica particles (B) having an ET specific surface area of 300 m ² / g.
6 parts and 6 parts were put into a Henschel mixer and mixed for 5 minutes under the condition that the peripheral speed of the stirring blade was 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 surface-treated with dimethyl silicone oil.
0.6 parts and B surface-treated with dimethyldichlorosilane
Silica particles (B) having an ET specific surface area of 300 m ² / g.
4 parts were put into a Henschel mixer and mixed for 5 minutes under the condition that the peripheral speed of the stirring blade was 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 put into a Henschel mixer and mixed for 5 minutes under the condition that the peripheral speed of the stirring blade was 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 surface-treated with dimethyl silicone oil.
1.0 part was added to a Henschel mixer and mixed for 5 minutes under the condition that the peripheral speed of the stirring blade was 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 put into a Henschel mixer and mixed for 5 minutes under the condition that the peripheral speed of the stirring blade was 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 added to a Henschel mixer and mixed for 5 minutes under the condition that the peripheral speed of the stirring blade was 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 surface-treated with dimethyldichlorosilane
Silica particles (B) having an ET specific surface area of 300 m ² / g.
7 parts and 7 parts were put into a Henschel mixer and mixed for 5 minutes under the condition that the peripheral speed of the stirring blade was 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) having a BET specific surface area of 130 m ² / g surface-treated with dimethyl silicone oil.
0.7 parts and B surface-treated with dimethyldichlorosilane
Silica particles (B) having an ET specific surface area of 300 m ² / g.
3 parts were put into a Henschel mixer, and mixed for 5 minutes under the condition that the peripheral speed of the stirring blade was 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 surface-treated with dimethyl silicone oil, and a surface of dimethyldichlorosilane were used. 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 was mixed for 5 minutes to obtain a magnetic one-component developer for comparison.

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 surface-treated with dimethyl silicone oil.
And 0.5 part 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.
A magnetic one-component developer for comparison was obtained by mixing for 5 minutes under the condition of m / s.

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 surface-treated with dimethyl silicone oil.
0.5 parts and B surface-treated with dimethyldichlorosilane
0.5 part of silica particles having an ET specific surface area of 200 m ² / g was charged into a Henschel mixer, and the peripheral speed of the stirring blade was 30.
A magnetic one-component developer for comparison was obtained by mixing for 5 minutes under the condition of m / s.

Comparative Example 10 100 parts of the magnetic toner particles obtained in Example 1, 0.5 parts of silica particles (A) having a BET specific surface area of 130 m ² / g surface-treated with dimethyl silicone oil, and dimethyl di Silica particles having a BET specific surface area of 400 m ² / g surface-treated with chlorosilane.
5 parts were put into a Henschel mixer and mixed for 5 minutes under the condition that the peripheral speed of the stirring blade was 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, 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 (AB) was evaluated as a black solid memory. The halftone memory was obtained as follows. In the halftone image after printing the document of FIG. 2 four times, the black solid portions 10a, 10b of FIG.
A portion corresponding to 10c and 10d was measured with a reflection densitometer RD-914 manufactured by Macbeth Co., and an average value of image densities at these four points was defined as C. On the other hand, the white portions 20a, 20b, 20 of FIG.
The part that matches c and 20d is a reflection densitometer R manufactured by Macbeth
It is measured by D-914, and 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, by using the magnetic one-component developer of each of the examples and comparative examples, 10,000 sheets were continuously printed by the printer, and the contamination and transfer efficiency on the surface of the photoreceptor after the continuous printing were confirmed. Is shown in Table 1. The contamination of the photoconductor is visually observed on the surface of the photoconductor after 10,000 sheets, and ○ indicates that there is no contamination, and X indicates a small amount of toner particle lumps adhered to the photoconductor surface, resulting in spots on the transfer paper image. The XX indicates that a large amount of toner particles are adhered to the surface of the photoconductor and a large amount of spots are formed on the transfer paper image. The transfer efficiency (%) was calculated using the following formula.

[0042]

[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.

[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 is an image with 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, in all the developers of Comparative Examples 1 to 10, more black solid memories or halftone memories were generated than in the examples. Further, in Comparative Example 1, the image density was low and the transfer efficiency was also inferior to that of the example. Further, in Comparative Examples 3, 4, 5, 7, 8, 9 and 10, contamination on the surface of the photoconductor occurred, and in Comparative Examples 3 and 4, the transfer efficiency was low.

[0046]

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

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03G 9/08

Claims (4)

(57) [Claims] 1. A BET specific surface area of a surface of magnetic toner particles treated with silicone oil is 100 to 150 m.
BET specific surface area of the silica particles (A) of ² / g and a silane coupling agent is 250 to 350 m ² / g
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 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 photosensitive drum provided 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 silica particles (A) having a BET specific surface area of 100 to 150 m ² / g surface-treated with silicone oil on the surface of the magnetic toner particles. ) And the BET specific surface area of which is surface-treated with a silane coupling agent is 250
A magnetic one-component developer to which silica particles (B) of 350 m ² / g are attached, and the weight ratio of the silica particles (A) to the silica particles (B) is 40:60 to 60:40. And a developing method.