JPH11194525A - Developer and developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a developer containing a manganese magnesium ferrite carrier favorable in safety so as to form an excellent image without causing toner scattering, lowering of image density and carrier deposit. SOLUTION: This developer contains a toner containing a coloring material and a binding resin, and a manganese magnesium ferrite carrier. In this case, 0.05-0.3 wt.% of conductive silica particles having 30 nm-2 μm of mean particle size is contained with respect to total weight of the toner, and a covered rate with the toner in the surface of the manganese magnesium ferrite carrier is 30-65%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer used for electrophotography, electrostatic recording, and the like, and a developing device using such a developer.

[0002]

2. Description of the Related Art In recent years, reversal development has been used for digital PPC. In this developing method, first, the surface of the photoreceptor is uniformly charged to a negative polarity by the main charger, and the surface of the photoreceptor is irradiated with a laser beam or the like on the image to remove the charge of the irradiated portion, thereby reducing the latent image. The potential is reduced to the partial potential. In this manner, a latent image of a well potential is formed, and a negative toner is developed on the exposed latent image portion of the well potential by applying a negative developing bias to the developing device.

In such a development system, development process conditions have been optimized in order to obtain a higher quality image, and in recent years, toner and carrier used as a developer have been reduced in particle size, and development has been carried out. By using various fine particles such as silica particles, resin fine powder, barium titanate, and magnetite as external additives in the developer to increase the toner specific concentration in the developer, the physical properties of the toner and the developer are improved. Improve and pursue higher quality images.

As a carrier used for such a developer, a copper-zinc ferrite carrier has been widely used conventionally. On the other hand, in recent years, due to environmental issues,
Use of a manganese-magnesium-based ferrite carrier that is advantageous for safety is being studied.

However, the manganese-magnesium ferrite carrier has a high carrier resistance. Therefore, when an image is formed using a manganese-magnesium ferrite carrier, the image density is reduced as compared with the case where a copper-zinc ferrite carrier is used. In addition, there is a problem of causing carrier adhesion and the like.

FIG. 2 is a graph showing the relationship between toner coverage and toner scattering when an image is formed for a developer using a manganese magnesium based ferrite carrier and a developer using a copper zinc based ferrite carrier. Is shown. In the figure, 201 indicates a graph of a developer using a manganese-magnesium-based ferrite carrier, and 202 indicates a graph of a developer using a copper-zinc-based ferrite carrier.

FIG. 3 is a graph showing the relationship between the toner coverage and the image density, and FIG. 4 is a graph showing the relationship between the toner coverage and the carrier adhesion level.
In the figures, 301 and 401 are graphs of a developer using a manganese magnesium-based ferrite carrier, respectively.
Reference numerals 2 and 402 represent graphs of the developer using the copper-zinc-based ferrite carrier.

From FIG. 2, the developer using the manganese-magnesium ferrite carrier is somewhat more advantageous in toner scattering than the developer using the copper-zinc ferrite carrier. It can be seen that the concentration and the carrier adhesion level are inferior.

As a countermeasure against such a problem, if the toner coverage on the surface of the carrier is increased, the reduction in image density and the adhesion of the carrier can be improved. However, as shown in FIG.
As an adverse effect, toner scattering occurs.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and includes a manganese-magnesium-based ferrite carrier which is advantageous for safety, and has toner scattering.
An object of the present invention is to provide a developer capable of preventing a decrease in image density and carrier adhesion and forming a good image.

Another object of the present invention is to use a manganese-magnesium-based ferrite carrier which is advantageous in terms of safety, to prevent toner scattering, prevent image density reduction and carrier adhesion, and obtain a good image. To provide a developing device.

[0012]

The developer of the present invention is a developer containing a toner containing a colorant and a binder resin, and a manganese magnesium-based ferrite carrier.
As an external additive, conductive silica particles having an average particle diameter of 30 nm to 2 μm are contained in an amount of 0.05 to 0.3% by weight based on the total weight of the toner, and the coverage of the manganese magnesium-based ferrite carrier surface with the toner is reduced. ,
30 to 65%.

The developing device of the present invention is a developer containing a toner containing a colorant and a binder resin, and a manganese-magnesium-based ferrite carrier.
The toner contains 0.05 to 0.3% by weight of conductive silica particles having a particle size of 30 nm to 2 μm with respect to the total weight of the toner, and the coverage of the manganese magnesium ferrite carrier surface with the toner is 30 to 65%.
A developer container that stores the developer, and is provided to face the image carrier, and carries the developer supplied from the developer container connected to the developer container,
A developer carrying member for supplying the carried developer to the image carrier and performing development.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has been made to realize good image formation using a manganese magnesium-based ferrite carrier which is advantageous in safety.

The developer of the present invention is a two-component developer containing a toner containing a colorant and a binder resin, and a manganese-magnesium ferrite carrier. 30 to 65%, and 3% as an external additive.
Conductive silica particles having an average particle size of 0 nm to 2 μm are added in an amount of 0.05 to 0.3% by weight based on the total weight of the toner.

Further, the developing device of the present invention is a developing device to which the above-mentioned developer is applied, wherein a toner containing a colorant and a binder resin, a manganese-magnesium ferrite carrier, and a toner A conductive silica particle having an average particle diameter of 30 nm to 2 μm in an amount of from 0.05 to 0.3% by weight, and a toner coverage of 30 to 65% on the surface of the manganese-magnesium ferrite carrier. A developer container to be housed, and provided to face the image carrier, while carrying the developer supplied from the developer container connected to the developer container,
A developer carrying member for supplying the carried developer to the image carrying member to perform development.

When a manganese-magnesium ferrite carrier is used as a carrier, its image deteriorates,
Since carrier adhesion occurs, for example, it is conceivable to increase the specific surface area with respect to the carrier and increase the toner coverage by reducing the particle size of the toner used. However, at this time, the toner on the surface of the carrier is excessively supplied, so that toner scattering occurs. This is because when the carrier and the toner meet, the carrier cannot sufficiently move around on the toner, and weakly charged toner is generated.

Therefore, in the present invention, the toner coverage on the surface of the manganese-magnesium ferrite carrier is specified in the range of 30 to 65%, and at the same time, as an external additive,
Further, conductive silica particles having an average particle diameter of 30 nm to 2 μm are added to the toner in an amount of 0.05 to 0.1% based on the total weight of the toner.
By adding 3% by weight, broadening on the highly charged side can be suppressed, generation of weakly charged toner can be prevented, and the problem of toner scattering can be improved.

As described above, when the developer of the present invention is used,
In addition to the reduction in image density and carrier adhesion, the problem of toner scattering can be improved, and a good image can be formed that is not inferior to a developer using a copper-zinc-based carrier.

According to the present invention, as an external additive, 6
Hydrophobized inorganic oxide particles having an average particle diameter of 0.1 to 16 μm are used in an amount of 0.1 to 1.
Preferably, it further contains 0% by weight.

By using such hydrophobically treated inorganic oxide particles in combination, high fluidity is imparted to the toner,
When the carrier moves sufficiently on the toner, the generation of weakly charged toner is further suppressed, the problem of toner scattering is further improved, and an excellent image can be formed.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic view showing an example of an image forming apparatus to which the developer and the developing device of the present invention can be applied.

In FIG. 1, reference numeral 1 denotes a photosensitive drum which is provided rotatably in the direction of the arrow and which carries an image. In the peripheral portion of the photosensitive drum, a charging charger 2, an erasing array 3, an exposure unit 4, a developing device 5, a transfer / peeling charger 6, 7, a cleaning device 8, and a static elimination charger 9 are sequentially provided in the rotation direction. Image forming means 1
0 is formed.

A pair of aligning rollers 11 for aligning the sheet is provided below the developing device 5. A guide for guiding the sheet is provided between the pair of aligning rollers 11 and the photosensitive drum 1. A body 12 is provided.

Further, below the cleaning device 8,
A transport belt 13 that transports the sheet is provided.

When an image is formed, an original is set on an original glass, and the original is irradiated with light from an exposure lamp (not shown). The reflected light from the document is imaged on the peripheral surface of the photosensitive drum 1 via an optical system. The surface of the photosensitive drum 1 is charged by a charging charger 2 in advance. An image is formed.
The electrostatic latent image is sent to the developing device 5 by the rotation of the photosensitive drum 1, where the developer is supplied,
It is visualized.

On the other hand, at this time, paper is supplied from a paper feed cassette (not shown), and after the paper is aligned by the aligning roller pair 11, the photosensitive drum 1
Is transferred by the transfer charger 6.

The sheet on which the image has been transferred is peeled off from the photosensitive drum 1 by the action of the peeling charger 7 and is conveyed by the traveling of the conveyor belt 13. The sheet is sent to a fixing device (not shown), where the transferred image is fixed and discharged.

The developing device 5 according to the present invention is provided to face the photosensitive drum 1 rotatably arranged.
The photosensitive drum 1 is rotated in the direction of arrow a by a main motor (not shown).

The developing device 5 includes a binder resin, a coloring material, silica that has been subjected to a conductive treatment, silica whose surface has been subjected to a hydrophobic treatment,
And a developing roller 14a for holding only a negatively charged developer containing a manganese-magnesium-based ferrite carrier on the outer periphery and adhering only a negatively charged toner to an electrostatic latent image formed on the photosensitive drum 1. Have. The two-component developer D and the developing roller 14a are housed in a housing 14b.

At both ends in the longitudinal direction of the developing roller 14a, the distance between the surface of the non-magnetic sleeve forming the outer peripheral surface of the developing roller 14a and the photosensitive layer on the surface of the photosensitive drum 1 is kept constant. Guide rollers (not shown) are provided. Thereby, the distance between the surface of the sleeve and the photosensitive layer of the photosensitive drum 1 is always kept constant.
The sleeve of the developing roller 14a has S
A magnet medium in which a plurality of pole and N pole fixed magnets are arranged at a predetermined angle is provided.

A predetermined developing bias voltage is applied to the developing roller 14a and the carrier and the toner, that is, the developer D in the developing device 5 via a developing bias voltage generating circuit (not shown).

When developing the electrostatic latent image formed on the surface of the photosensitive drum 1, the carrier ears formed on the sleeve along the lines of magnetic force generated from the main magnetic pole of the magnet medium of the developing roller 14a. The toner adhering to the (pigtails) due to the image force is applied to the photosensitive drum 1 and the developing roller 14a.
In the development region where the toner image is opposed to the toner, the toner is moved by an electric field formed by the potential of the electrostatic latent image on the photosensitive drum 1 and the developing bias voltage, and the electrostatic latent image is developed.

The developer D used here contains a binder resin, a coloring material, conductively treated silica, silica whose surface has been hydrophobized, and a manganese-magnesium ferrite carrier. It is a chargeable developer.

Further, as the binder resin used in the developer of the present invention, a copolymer of styrene and a substituted product thereof, an acrylic resin and the like, which have been conventionally used as a binder resin for the developer, can be used. .

Examples of the copolymer of styrene and its substituted product include polystyrene homopolymer, hydrogenated styrene resin, styrene-isobutylene copolymer, styrene-butadiene copolymer, acrylonitrile-butadiene-styrene terpolymer. Acrylonitrile-styrene-acrylic ester terpolymer, styrene-acrylonitrile copolymer, acrylonitrile-acrylic rubber-styrene terpolymer, acrylonitrile-chlorinated polystyrene-styrene terpolymer, acrylonitrile-EVA- Styrene terpolymer, styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene rubber, styrene-maleic acid ester copolymer, styrene-isobutylene copolymer,
And a styrene-maleic anhydride copolymer.

As the acrylic resin, for example,
Polyacrylate, polymethyl methacrylate, polyethyl methacrylate, poly-n-butal methacrylate, polyglycidyl methacrylate, polyfluorinated acrylate, styrene-methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-ethyl acrylate copolymer Coalescence is exemplified.

In addition, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin, phenol resin, urea resin, polyvinyl butyral, polyacrylic resin, rosin, modified rosin, terpene resin, aliphatic Alternatively, an alicyclic hydrocarbon resin, an aromatic petroleum resin, chlorinated paraffin, paraffin wax, or the like can be used alone or as a mixture.

As the coloring material used in the developer of the present invention, carbon black, organic or inorganic pigments and dyes, and the like are used. Although there is no special restriction, carbon black includes acetylene black, furnace black, thermal black, channel black, Ketjen black and the like, and facial dyes include, for example, First Yellow G, Benzidine Yellow, Indofast Orange, Irgazine Red, Carmine FB, Permanent Bordeaux FRR, Pigment Orange R, Risor Red 2G, Lake Red C, Rhodamine FB, Rhodamine B Lake, Phthalocyanine Blue, Pigment Blue,
Brilliant green B, phthalocyanine green, quinacridone and the like. These can be used alone or as a mixture.

Various natural waxes, such as carnauba wax, hydrogenated castor oil, and low molecular weight olefin polymers are used in the present invention, but preferably low molecular weight olefin polymers are used. As this low molecular weight olefin polymer, a low molecular weight olefin polymer or a copolymer of olefin and a monomer other than olefin is used. Here, olefins include ethylene, propylene, butene-1 and the like, and monomers other than olefins include acrylates and methacrylates.

Examples of the charge control agent used in the developer of the present invention include metal complex salts of monoazo dyes, metal complexes of salicylic acid, oxynaphthoic acid, dicarboxylic acids such as Co, Cr and Fe, sulfonated copper phthalocyanine pigments, Examples include styrene oligomers into which nitro groups and halogens have been introduced, chlorinated paraffins, and melamine resins.

As a mixing and dispersing method, a warm dispersing method using a high-speed dissolver, a roll mill, a ball mill, or the like;
A melt kneading method using a roll, a pressure kneader, an internal mixer, a screw-type extruder, or the like can be used. As a mixing means, a ball mill, a V-type mixer, a Folberg, a Henschel mixer, or the like can be used. it can.

As means for coarsely pulverizing the mixture,
For example, a hammer mill, a cutter mill, a jet mill, a roller mill, a ball mill and the like can be used. Furthermore,
As a means for finely pulverizing the coarsely pulverized product, a jet mill, a high-speed rotary pulverizer or the like can be used. As a means for classifying the finely pulverized material, an air flow classifier or the like can be used.

As an external additive to the toner, a silica fine powder having conductivity by coating the surface with a mixture of tin oxide and antimony is used, and the surface is made hydrophobic to ensure fluidity. Oxidized silicon dioxide, aluminum silicate, sodium silicate, potassium silicate, zinc silicate, magnesium silicate and the like. As the metal oxide fine particles, inorganic oxides such as zinc oxide, titanium oxide, aluminum oxide, zirconium oxide, strontium titanate, and barium titanate can be used alone or in combination.

As a means for mixing the external additive, various known mixing devices can be used, and examples thereof include a Henschel mixer and a super mixer.

[0047]

The present invention will be described below in detail with reference to examples.

As the toner used in the examples, a toner having a composition shown in Table 1 below was used.

[0049]

[Table 1] The toner has a relatively small average particle size of 8 μm to 9.5 μm.

Example 1 A toner material having the composition shown in Table 1 was heated, melt-kneaded, cooled, pulverized and classified to obtain toner particles. To 100 parts by weight of the obtained particles, 0.05 parts by weight of conductive silica having an average particle diameter of 50 nm and 1.0 parts by weight of hydrophobic silica having a volume average particle diameter of 16 nm were mixed to obtain a toner. . The toner thus prepared and a manganese-magnesium-based ferrite carrier whose surface is coated with silicon are stirred for 1 hour using a ball mill so that the coverage of the toner on the carrier surface is 30% to obtain a developer. Was.

Note that the coverage is E, the coverage is ρc, the density of the carrier (g / cm ³ ), and ρt is the density of the toner (g / cm ³ ).
cm ³ ), C is the specific toner concentration (% by weight), dc is the average particle diameter of the carrier (cm), S is obtained by the following equation, and dt is the average particle diameter of the toner (cm).
It is determined by the following equations (1) and (2).

E = 100 · C · ρc · dc · S / π · (100−C) · ρt · dt ³ ‥ (1) where

[0053]

(Equation 3) The following evaluation was performed about the obtained developer.

(1) Toner scattering (dirt inside copying machine) Toner scattering was evaluated using a Toshiba copier Leo Dry 6550. 100,000 copies are made using a chart that occupies 6% of the area of the character part in A4 size,
Then, observe the toner scattering state inside the copier, and
The evaluation was made in three stages of x.

(2) Image Density The image density is the same as described above for the Toshiba copier Leodry 65.
The evaluation was performed using 50. For the evaluation, the test chart No. Using 1-T, the image density of the solid portion after copying 100,000 sheets was measured in an environment at room temperature of 10 ° C. and humidity of 20%, and the image density was determined using a Macbeth densitometer. The image density is 1.00 or more.
When the value was 0.8 or more and less than 1.00, the evaluation was Δ, and when it was less than 0.8, the evaluation was X.

(3) Carrier Adhesion Carrier adhesion was evaluated using the same Toshiba copier Leo Dry 6550 as described above. For evaluation, room temperature 10
Under an environment of a temperature of 20 ° C. and a humidity of 20%, the adhesion of the carrier on the continuous blank copy after 100,000 copies was observed, and the evaluation was made in three grades of ○, Δ, and ×.

As described above, as a result of the evaluation test, a level showing no problem in toner scattering, image density, and carrier adhesion was shown.

The results obtained are shown in Table 2 below.

Example 2 A toner material having the composition shown in Table 1 was heated, melt-kneaded, cooled, pulverized and classified to obtain toner particles. To 100 parts by weight of the obtained particles, 0.05 part by weight of conductive silica having a volume average particle diameter of 1.5 nm and 1.0 part by weight of hydrophobic silica having a volume average particle diameter of 6 nm were mixed. I got The surface of the toner thus prepared and a manganese-magnesium-based ferrite carrier whose surface is silicon-coated are stirred for one hour using a ball mill so that the coverage of the toner on the carrier surface is 30%, and the developer is stirred. Obtained.

Using the obtained developer, in the same manner as in Example 1,
A toner scattering test, image density confirmation at low temperature and low humidity, and a carrier adhesion test were performed. The results obtained are shown in Table 2 below. Example 3 A toner material having the composition shown in Table 1 was heated, melted and kneaded, cooled, pulverized and classified to obtain toner particles. To 100 parts by weight of the obtained particles, 0.30 part by weight of conductive silica having a volume average particle diameter of 1.5 nm and 0.1 part by weight of hydrophobic silica having a volume average particle diameter of 16 nm were mixed, and the toner was mixed. Obtained. The toner thus prepared and a manganese-magnesium ferrite carrier whose surface is coated with silicon are stirred for 1 hour using a ball mill so that the coverage of the toner on the carrier surface is 65%, and a developer is obtained. Was.

Using the obtained developer, a toner scattering test, confirmation of image density at low temperature and low humidity, and a carrier adhesion test were carried out in the same manner as in Example 1. The results obtained are shown in Table 2 below.

Example 4 A toner material having the composition shown in Table 1 was heated, melted and kneaded, cooled, pulverized and classified to obtain toner particles. To 100 parts by weight of the obtained particles, 0.30 part by weight of conductive silica having a volume average particle diameter of 50 nm and 0.1 part by weight of hydrophobic silica having a volume average particle diameter of 6 nm were mixed to obtain a toner. . The toner thus prepared and a manganese-magnesium ferrite carrier coated on the surface with silicon were stirred for 1 hour using a ball mill so that the coverage of the toner on the carrier surface was 65% to obtain a developer. .

Using the obtained developer, a toner scattering test, an image density confirmation at low temperature and low humidity, and a carrier adhesion test were performed in the same manner as in Example 1. The obtained results showed levels at which there was no problem in toner scattering, image density, and carrier adhesion.

Example 5 A toner material having the composition shown in Table 1 was heated, melted and kneaded, cooled, pulverized and classified to obtain toner particles. Further obtained particles 1
A toner was obtained by mixing 0.20 part by weight of conductive silica having a volume average particle diameter of 0.7 nm and 0.3 part by weight of hydrophobic silica having a volume average particle diameter of 8 nm with respect to 00 parts by weight. The toner thus prepared and a manganese-magnesium-based ferrite carrier coated on the surface with silicon were stirred for 1 hour using a ball mill such that the coverage of the toner on the carrier surface was 44% to obtain a developer. .

Using the above developer, a toner scattering test, confirmation of image density at low temperature and low humidity, and a carrier adhesion test were performed in the same manner as in Example 1. The results are shown in Table 2 below.

Example 6 A toner material having the composition shown in Table 1 was heated, melt-kneaded, cooled, pulverized and classified to obtain toner particles. With respect to 100 parts by weight of the obtained particles, 0.15 parts by weight of conductive silica having a volume average particle diameter of 0.7 nm and 0.6 parts by weight of hydrophobic silica having a volume average particle diameter of 8 nm were mixed, A toner was obtained. The toner thus prepared and a manganese-magnesium-based ferrite carrier coated on the surface with silicon were stirred for 1 hour using a ball mill such that the coverage of the toner on the carrier surface was 58% to obtain a developer. .

Using the above developer, toner scattering test, image density confirmation at low temperature and low humidity, and carrier adhesion test were conducted in the same manner as in Example 1. Table 2 shows the results.

Example 7 A toner material having the composition shown in Table 1 was heated and melt-kneaded, cooled, pulverized and classified to obtain toner particles. Obtained toner particles 1
0.03 parts by weight of conductive silica having a volume average particle diameter of 0.7 nm and 1.0 parts by weight of silica not subjected to hydrophobic treatment and having a volume average particle diameter of 6 nm are mixed with 00 parts by weight. Particles were obtained. The thus prepared toner and a manganese magnesium-based ferrite carrier coated on the surface with silicon are coated with a toner having a toner coverage of 40% on the carrier surface.
% By using a ball mill for 1 hour to obtain a developer. Using the obtained developer, a toner scattering test, an image density check at low temperature and low humidity, and a carrier adhesion test were performed in the same manner as in Example 1. Table 2 shows the results. In this example, poor charging occurred due to deterioration of the fluidity of the developer, and some toner scattering occurred. However, the image density was good, carrier adhesion was small, and it was within a practical range.

As described above, when the toner coverage on the surface of the manganese-magnesium ferrite carrier is 30 to 65% as in Examples 1 to 6, the 50% diameter of the conductive silica is 0.7 to 2.0 μm, The amount of addition is 0.05 to 0.30%,
The 50% diameter of the hydrophobized inorganic oxide is 6-16n
m, if the addition amount is 0.1 to 1.0%, toner scattering,
It was found that the image density was low and low in humidity, and the level had no problem with carrier adhesion.

Further, even in the case where the hydrophobicized inorganic oxide was not added as in Example 7, there was no practical problem.

Comparative Example 1 A toner material having the composition shown in Table 1 was heated, melted and kneaded, cooled, pulverized and classified to obtain toner particles. To 100 parts by weight of the obtained particles, 0.03 parts by weight of conductive silica having a volume average particle diameter of 50 nm and 1.2 parts by weight of hydrophobic silica having a volume average particle diameter of 16 nm were mixed. Obtained. The toner thus prepared and a manganese-magnesium-based ferrite carrier coated on the surface with silicon were stirred for 1 hour using a ball mill such that the coverage of the toner on the carrier surface was 25% to obtain a developer. . Using the obtained developer, a toner scattering test, an image density confirmation at low temperature and low humidity, and a carrier adhesion test were performed in the same manner as in Example 1. Table 2 shows the obtained results.

In this comparative example, it was found that since the amount of conductive silica added was small, charge leakage was not performed efficiently, resulting in a decrease in image density and carrier adhesion on a white background copy image portion. .

Comparative Example 2 A toner material having the composition shown in Table 1 was heated, melted and kneaded, cooled, pulverized and classified to obtain toner particles. Obtained toner particles 1
The conductive silica having a volume average particle diameter of 20 nm is 0.05 part by weight, and the volume average particle diameter is 18 nm with respect to 00 parts by weight.
Was mixed with 1.2 parts by weight of the above hydrophobic silica to obtain a toner. The toner thus prepared and a manganese-magnesium-based ferrite carrier coated on the surface with silicon were stirred for 1 hour using a ball mill such that the toner coverage on the carrier surface was 30% to obtain a developer. . In the same manner as in Example 1 using the obtained developer, a toner scattering test, an image density check at low temperature and low humidity, and a carrier adhesion test were performed. Table 2 shows the obtained results. In this comparative example, the image density was reduced due to the effect of the increase in the charge amount, and carrier adhesion occurred on the white-copy image portion.

Comparative Example 3 A toner material having the composition shown in Table 1 was heated and melt-kneaded, cooled, pulverized and classified to obtain toner particles. Obtained toner particles 1
0.40 parts by weight of conductive silica having a volume average particle diameter of 1.5 nm was mixed with 00 parts by weight to obtain a toner.
The toner thus prepared and a manganese magnesium-based ferrite carrier coated on the surface with silicon are
In order that the coverage of the toner on the carrier surface is 65%,
The mixture was stirred for 1 hour using a ball mill to obtain a developer. In the same manner as in Example 1 using the obtained developer, a toner scattering test, an image density confirmation at low temperature and low humidity, and a carrier adhesion test were performed. Table 2 shows the results. In this comparative example,
Due to the deterioration of the fluidity of the developer, poor charging was caused, the charge amount was reduced, and toner scattering was deteriorated.

Comparative Example 4 A toner material having the composition shown in Table 1 was heated, melted and kneaded, cooled, pulverized and classified to obtain toner particles. Obtained toner particles 1
To 100 parts by weight, 1.0 part by weight of hydrophobic silica having a volume average particle diameter of 6 nm was mixed to obtain a toner. The toner thus prepared and a manganese-magnesium-based ferrite carrier coated on the surface with silicon are stirred for 1 hour using a ball mill so that the coverage of the toner on the carrier surface is 65%, and a developer is obtained. Was. Using the obtained developer, a toner scattering test, an image density check at low temperature and low humidity, and a carrier adhesion test were performed in the same manner as in Example 1. Table 2 shows the results. In this comparative example, since conductive silica was not added, problems occurred in image density and carrier adhesion.

Comparative Example 5 A toner material having the composition shown in Table 1 was heated, melted and kneaded, cooled, pulverized and classified to obtain toner particles. Obtained toner particles 1
A toner was obtained by mixing 0.03 parts by weight of conductive silica having a volume average particle diameter of 1.5 nm and 1.0 parts by weight of hydrophobic silica having a volume average particle diameter of 6 nm with respect to 00 parts by weight. The toner thus prepared and a manganese-magnesium-based ferrite carrier coated on the surface with silicon are stirred for 1 hour using a ball mill so that the coverage of the toner on the carrier surface is 70%, to obtain a developer. Was. Using the obtained developer, a toner scattering test was performed in the same manner as in Example 1.
Image density confirmation and carrier adhesion test at low temperature and low humidity were performed. Table 2 shows the results. In this comparative example, the toner coverage on the carrier surface was large, the toner could not move sufficiently on the carrier, and the toner could not be frictionally charged sufficiently, and weakly charged toner was generated, and toner scattering was deteriorated. .

Comparative Example 6 A toner material having the composition shown in Table 1 was heated, melted and kneaded, cooled, pulverized and classified to obtain toner particles. Obtained toner particles 1
A toner was obtained by mixing 0.03 parts by weight of conductive silica having a volume average particle diameter of 2.5 μm and 1.0 parts by weight of hydrophobic silica having a volume average particle diameter of 6 nm with respect to 00 parts by weight. The toner thus prepared and a manganese-magnesium-based ferrite carrier coated on the surface with silicon are stirred for 1 hour using a ball mill so that the coverage of the toner on the carrier surface is 65%, and a developer is obtained. Was. Using the obtained developer, a toner scattering test, an image density check at low temperature and low humidity, and a carrier adhesion test were performed in the same manner as in Example 1. Table 2 shows the results. In this comparative example, image density reduction and carrier adhesion occurred due to poor dispersion of the conductive silica.

[0078]

[Table 2]

[0079]

According to the present invention, a developer containing a manganese-magnesium-based ferrite carrier which is advantageous in terms of safety, without lowering of image density, carrier adhesion and toner scattering, and using a copper-zinc-based ferrite carrier A developer capable of forming a good image which is not inferior to the developer is obtained.

Further, according to the developing device of the present invention, by using the above-mentioned developer, the use of a manganese-magnesium-based ferrite carrier which is advantageous for safety causes a decrease in image density, carrier adhesion, and toner scattering. As a result, a good image can be formed which is not inferior to the developer using the copper zinc based ferrite carrier.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of an image forming apparatus using a developing device of the present invention.

FIG. 2 is a graph showing the relationship between the toner coverage of a conventional developer and toner scattering.

FIG. 3 is a graph showing the relationship between the toner coverage of a conventional developer and the image density.

FIG. 4 is a graph showing the relationship between the toner coverage of a conventional developer and the carrier adhesion level.

[Explanation of Symbols] 1 ... photosensitive drum 2 ... charging charger 3 ... erasing array 4 ... exposure unit 5 ... developing device 6 ... transfer charger 7 ... peeling charger 8 ... cleaning device 9 ... static elimination charger 10 ... image forming means 11 ... aligning Roller pair 12 Guide member 13 Conveyor belt 14a Developing roller

Claims (8)

[Claims] 1. A developer containing a toner containing a colorant and a binder resin, and a manganese-magnesium ferrite carrier, wherein the external additive is 30 nm to 2 μm.
The toner contains 0.05 to 0.3% by weight of conductive silica particles having an average particle diameter of m with respect to the total weight of the toner, and the coverage of the manganese magnesium-based ferrite carrier surface with the toner is 30 to 65%. A developer, characterized in that: 2. The method of claim 1, wherein the external additive further comprises 0.1 to 1.0% by weight of a hydrophobically treated inorganic oxide having an average particle diameter of 6 to 16 μm based on the total weight of the toner. Item 7. The developer according to Item 1. 3. The developer according to claim 1, wherein the coverage is determined by the following equations (1) and (2). E = 100 · C · ρc · dc · S / π · (100−C) · ρt · dt ³ ‥ (1) Here, in the formula, E is the coverage, and ρc is the carrier density (g /
cm ³ ), ρt is the density of the toner (g / cm ³ ), C is the specific toner concentration (% by weight), and dc is the average particle diameter of the carrier (c
m) and dt represent the average particle size (cm) of the toner. 4. The inorganic oxide includes silicon dioxide, aluminum silicate, sodium silicate, potassium silicate,
3. The material according to claim 2, wherein the material is at least one selected from the group consisting of zinc silicate, magnesium silicate, zinc oxide, titanium oxide, aluminum oxide, zirconium oxide, strontium titanate, and barium titanate. Developer. 5. A developer containing a toner containing a colorant and a binder resin, and a manganese-magnesium ferrite carrier, wherein 30 nm to 2 μm is used as an external additive.
m containing conductive silica particles having a particle size of 0.05 to 0.3% by weight based on the total weight of the toner, and a coverage of the manganese magnesium ferrite carrier surface with the toner of 30 to 65%. A developer container for storing a developer, provided opposite to the image carrier, connected to the developer container to carry the developer supplied from the developer container, and to the image carrier; A developer carrying member for supplying the carried developer and performing development. 6. The external additive further comprises 0.1 to 1.0% by weight of a hydrophobically treated inorganic oxide having an average particle size of 6 to 16 μm based on the total weight of the toner. The developing device according to claim 5. 7. The developing device according to claim 5, wherein the coverage is obtained by the following equations (1) and (2). E = 100 · C · ρc · dc · S / π · (100−C) · ρt · dt ³ ‥ (1) Here, in the formula, E is the coverage, and ρc is the carrier density (g /
cm ³ ), ρt is the density of the toner (g / cm ³ ), C is the specific toner concentration (% by weight), and dc is the average particle diameter of the carrier (c
m) and dt represent the average particle size (cm) of the toner. 8. The inorganic oxide includes silicon dioxide, aluminum silicate, sodium silicate, potassium silicate,
7. The material according to claim 6, wherein the material is at least one selected from the group consisting of zinc silicate, magnesium silicate, zinc oxide, titanium oxide, aluminum oxide, zirconium oxide, strontium titanate, and barium titanate. Developing device.