JP3298034B2 - Two-component developer for developing electrostatic images and image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-component developer for developing electrostatic images such as electrophotography and an image forming method.

[0002]

2. Description of the Related Art Conventionally, a two-component developer composed of a carrier and a toner is often used as a developer for electrophotography and the like. In recent years, a coating carrier obtained by coating a ferrite carrier with a resin has been used from the viewpoint of improving the durability and image quality of the carrier, particularly the reproducibility of fine lines. However, in the case of a coating carrier, the developability is low due to the high electric resistance.
Particularly, only an image having a large edge effect can be obtained, and the image density of the solid portion is low. In addition, the environment is largely dependent on the environment, and characters are crushed at low density at low temperature and low humidity and excessively high density at high temperature and high humidity, and the resolution is reduced. Further, toner scattering and fogging occur.

In order to solve these problems, a half-coated carrier that exposes a convex portion of a carrier core, instead of coating the entire surface of the carrier with a resin, is disclosed in Japanese Patent Laid-Open Publication No. Hei.
160463 and JP-A-4-93954. Since the core of the carrier is exposed, the electric resistance is low,
Charges easily move, and a decrease in developability is prevented. However, in order to reduce the resistance of these carriers, charges having a polarity opposite to the charge on the surface of the photoreceptor are injected into the carriers and adhere to the image portion of the photoreceptor. In addition, since the core is exposed, contamination of the carrier surface by the toner component, so-called spent, is likely to occur, leading to a decrease in the charge amount of the developer,
Occurrence of fogging and contamination of the inside of the apparatus due to scattering of toner occur. Further, there is also a problem that a coating resin portion serving as a charging site decreases due to an increase in an exposed portion of the core, and a sufficient charge amount cannot be obtained.

By the way, in recent electrophotographic copying machines, it has become desirable to employ a so-called recycling system for toner reuse from the viewpoints of environmental protection, no pollution, and resource reuse. The recycling system collects toner remaining on the photoreceptor without being transferred by a cleaning device, and returns the collected toner to a developing device or a toner replenishing device for reuse. In this case, since a large amount of stress is applied to the toner, the embedding of the external additive is severe, so that the charging property becomes unstable, the developing property is reduced, toner scattering or fogging occurs, and the transfer rate is reduced. Further, the embedding of the external additive reduces the effect of polishing and refreshing the carrier surface by the toner, and increases the spent on the carrier surface.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and (1) to provide a developer capable of preventing carrier adhesion and obtaining a stable high-density and high-quality image. (2) to provide a developer having good durability without fogging and toner scattering. (3) Even when a toner recycling system is employed, high-density and high-quality images can be obtained for a long period of time. To provide a developer which can be obtained.

[0006]

The object of the present invention is attained by adopting any one of the following constitutions.

(1) A magnetic material is used as a core material, and the core material is used as a core material.
An electrostatic charge composed of a toner coated with a resin-coated carrier leaving a core material surface of 1 to 10.0% and an inorganic fine particle having a primary average particle diameter of 5 to 20 nm and an aggregated particle having a number average particle diameter of 30 to 500 nm. Two-component developer for image development.

(2) Using a two-component developer consisting of a carrier and a toner, the toner remaining on the photoreceptor without being transferred is collected by a cleaning device, and the collected toner is returned to a developing device or a toner replenishing device to be re-used. In an image forming method employing a toner recycling system to be used, a carrier coated with a magnetic material as a core material and resin coated with the core material leaving 0.1 to 10.0% of a core material surface has a primary average particle size of 5 to 20%.
An image forming method, comprising using a two-component developer for developing an electrostatic charge image, comprising a toner to which inorganic fine particles having a number average particle diameter of 30 to 500 nm in agglomerated particles of 30 to 500 nm are added.

By exposing the core material as in the present invention, the resistance of the carrier can be reduced and the developability can be improved.
On the other hand, it promotes carrier adhesion and generation of spent, and remarkably lowers image quality. As a result of intensive studies, we were able to obtain a carrier capable of solving the above problem by exposing an appropriate amount of core material to the entire surface of the carrier. That is, while maintaining the spent resistance by an appropriate amount of exposure of the core material, the electric resistance is reduced, the developability is improved, and no carrier adhesion occurs. In addition, since the coating resin portion serving as a charging site is sufficiently maintained, a stable charge amount can be obtained. With respect to the coating resin in the present invention, it is particularly desirable to use a silicone resin which is a resin having a low surface energy, and further excellent in spent resistance,
A carrier having good abrasion resistance and peeling resistance can be obtained.

The durability of the carrier is further improved by using a toner to which inorganic fine particles having a primary average particle diameter of 5 to 20 nm and a number average particle diameter of the aggregated particles of 30 to 500 nm are added. When the inorganic fine particles are present on the toner surface, the spent material on the carrier surface can be appropriately polished, and the increase in spent material can be suppressed. The inorganic fine particles have fine primary particles, and the aggregated particles formed by agglomeration of several primary particles are irregularly shaped particles having fine irregularities, and appropriately induce a polishing effect.

When this developer is used in a toner recycling system, a high-density, high-quality image can be obtained for a long period of time because the aggregated inorganic fine particles maintain the carrier surface in a fresh state by an appropriate polishing effect. . In addition, since the aggregated particles of the inorganic fine particles have an average particle size of 30 to 500 nm, they are not embedded even when subjected to recycling stress, and can always be present on the toner surface, and a stable charge amount can be obtained. High quality images can be obtained over a long period of time.

[0012]

[Action]

(1) Carrier The magnetization is preferably 35 to 100 emu / g, particularly 45 to 85 emu / g.
g is preferred.

When the magnetization is less than 35 emu / g, the carrier is strongly influenced by the centrifugal force due to the rotation of the sleeve, and flies to the photosensitive member to adhere to the carrier. On the other hand, when the amount is 85 emu / g or more, the fixing force between the carriers in the brush is increased, and the photoreceptor is strongly rubbed. An image defect such as disappearance of a line perpendicular to the image is generated. Further, the photoreceptor may be damaged.

In this case, the magnetization is defined as an external magnetic field of 1 k0e by a DC magnetization characteristic automatic recording device (type 3257-35, manufactured by Yokogawa Electric Corporation).
It is the magnetization at the time of.

The carrier particle size is preferably from 15 to 200 μm,
Particularly preferred is 30 to 150 μm.

If it is smaller than 15 μm, carrier adhesion is constantly generated, and the image becomes unclear. However, if it is too large, image alignment will occur. The average particle size of the carrier is a volume average particle size measured by a laser diffraction type particle size distribution measurement HELOS (manufactured by Sympatech) equipped with a wet disperser.

In the present invention, the magnetic particles serving as the core material constituting the carrier are made of a material which is strongly magnetized in the direction by a magnetic field, for example, a ferromagnetic material such as iron, ferrite, magnetite, and other iron, nickel, and cobalt. Metals or alloys shown, or compounds containing these elements, alloys which do not contain ferromagnetic elements but which exhibit ferromagnetism by appropriate heat treatment, such as Heusler alloys such as manganese-copper-aluminum or manganese-copper-tin And particles made of chromium dioxide or the like can be used.

The core material exposure of the carrier is preferably from 0.1 to 10.0%, more preferably from 0.3 to 7.0%. In the case of 10.0% or more, a charge having a polarity opposite to that of the surface of the photoreceptor is injected into the carrier, and a so-called carrier adherence to an image portion of the photoreceptor occurs. In addition, toner spent occurs, the charge amount decreases, and fogging and toner scattering occur. On the other hand, 0.
If it is 1% or more, the resistance becomes high and the image density is remarkably reduced.

In the present invention, the amount of exposure of the core is defined as ESCA
By (XPS), the ratio of the number of elements existing in the surface layer of the carrier particles is obtained, then the element ratio of the magnetic material as the core material is obtained, and the abundance of the core material exposed on the carrier surface from both is calculated by the ratio. Say the value obtained.

The composition of the coating resin is not particularly limited, and various resins can be used. Specifically, for example, styrene resin, acrylic resin, styrene-acryl resin, vinyl resin, ethylene resin, rosin modified resin, polyamide resin, polyester resin, silicone resin, fluorine resin, and the like can be used. These may be used in combination.

Of these, silicone resins, which are particularly low surface energy resins and have excellent toughness, are desirable.

The silicone resin is not particularly limited. For example, a condensation reaction type silicone resin which is cured by the following reaction can be particularly preferably used.

[0023]

Embedded image

In the formula, R ₁ , R ₂ , R ₃ and R ₄ each represent a substituent such as an alkyl group, a hydrogen atom, a halogen atom, a methoxy group and a phenyl group, and OX represents an alkoxy group, a ketoxime group and an acetoxy group. And an aminoxy group.

Particularly preferred in such a condensation reaction type silicone resin is one in which the substituent is a methyl group. In a coating layer obtained by a condensation reaction type silicone resin having a methyl group as a substituent, a carrier having a dense structure, good water repellency and good moisture resistance can be obtained.

As the silicone resin used for the coating layer of the carrier, any of a heat-curable silicone resin and a normal-temperature-curable silicone resin can be used. Since heating to a high temperature is not required, the carrier can be easily manufactured.

The room temperature-curable silicone resin is a silicone resin which cures at a temperature of about 20 to 25 ° C. or slightly higher than that in an ordinary atmosphere, and does not require a temperature exceeding 100 ° C. for curing. Things.

When a heat-curable silicone resin is used, it is necessary to heat at 200 to 250 ° C. When a room-temperature-curable silicone resin is used, it is necessary to heat to a particularly high temperature for curing. However, heating may be performed in the range of 150 to 250 ° C. in order to promote curing. In drying, octyl group, lead such as naphthenic acid,
Metal soaps such as iron, cobalt, tin, manganese and zinc may be used as a drying accelerator, and organic amines such as ethanolamine can also be used effectively as a drying accelerator.

Examples of the method for producing the carrier include a wet method, such as an immersion method, a spray drying method, or a dry method in which resin fine particles are fixed on the surface of a magnetic material by applying a mechanical impact force to cover the surface. The amount of exposure of the core is controlled by the amount of resin coating and the coating conditions. The amount of the coating resin is preferably from 0.01 to 10% by weight, particularly preferably from 0.05 to 5% by weight, based on the magnetic material as the core material. Alternatively, after the magnetic material is coated with a resin, a mechanical impact force may be applied to cut off a portion of the coating resin to adjust the amount of exposure of the core. Examples of a device for applying a mechanical impact force include a Henschel mixer, a tabular mixer, and a ball mill.

(2) Toner The composition of the inorganic fine particles to be externally added includes, for example, silicon oxide, cerium oxide, zirconium oxide, titanium oxide, aluminum oxide, iron oxide, strontium titanate, barium titanate, aluminum silicate, and silicic acid. Examples thereof include sodium, magnesium silicate, silicon carbide, silicon nitride, and titanium nitride. These inorganic fine particles preferably have a hydrophobic group on the surface, and silane coupling agents such as octylmethoxysilane, dimethyldichlorosilane, hexamethyldisilazane, and N-β (aminoethyl) γ-aminopropyltrimethoxysilane, Those treated with a titanium coupling agent, silicone oil, stearic acid, lauric acid or the like are preferable.

As a method of treating the above compound, for example, the above compound is dissolved in a solvent, and the inorganic fine particles are dispersed in the solution. A method in which the solvent is removed by filtration or spray drying and then cured and disintegrated by heating, or using a fluidized bed apparatus, the compound is dissolved in the solvent, spray-coated on the inorganic fine particles, and then heated and dried. A method of removing the solvent to harden the film and then crushing the ejector can be used.

The particle diameter (primary particle diameter) of the inorganic fine particles is 5 to 5.
20 nm is preferred, and 7 to 15 nm is particularly preferred. When the particle size is smaller than 5 nm, when the agglomerated particles are formed, the irregularities are small and the polishing effect is insufficient. If it is larger than 20 nm, aggregated particles cannot be formed.

The method for measuring the particle size of the fine particles is as follows: inorganic fine particles are embedded in an ultraviolet curable resin, a thin piece having a thickness of about 200 nm is cut out, observed with a transmission electron microscope, and the number-based average primary particle is measured by an image analyzer. The particle size was determined.

The particle size of the agglomerated particles (agglomerated particle size) is 30 to 50.
0 nm is preferred, and 50 to 300 nm is particularly preferred. If it is smaller than 30 nm, the polishing effect is insufficient, and in the recycling system, the material is buried by mechanical stress, and the charge amount becomes unstable. On the other hand, when it is too large, the inorganic fine particles are detached from the toner surface, and a sufficient polishing effect cannot be obtained. In particular, this tendency is remarkable in a recycling system, and the transfer rate also decreases.

The method for measuring the aggregated particle diameter is as follows.
Zero pieces were extracted and the number-based average particle size was determined.

Two or more kinds of the above inorganic fine particles may be added in combination. The addition amount of the aggregated particles is preferably 0.05 to 5% by weight, and particularly preferably 0.1 to 3% by weight, based on the toner. When the content is 0.05% by weight or less, sufficient abrasiveness cannot be obtained, and when the content is 5% by weight or more, a part of the inorganic fine particles is present in a free state, and sufficient abrasiveness cannot be obtained. In addition, the amount of toner charge is reduced due to adhesion transfer to a carrier or the like,
This leads to fogging and toner scattering.

The inorganic fine particles are added to and mixed with the toner from the outside, and are contained in a state of being attached or driven onto the toner surface. The diameter of the aggregated particles is controlled by adjusting the mechanical impact force at the time of addition and mixing or by adjusting the mechanical impact force received during the crushing step after the hydrophobic treatment of the inorganic fine particles.

As the toner resin, a known styrene resin,
Styrene-acrylic copolymer resins, polyester resins, styrene-butadiene resins, epoxy resins and the like can be used.

The toner used in the present invention includes a colorant,
A release agent, a charge control agent and the like are used.

As the coloring agent, for example, carbon black, chrome yellow, Dupont oil red, quinoline yellow, phthalocyanine blue, malachite green oxalate and the like can be used. The amount of the colorant to be used is generally 0.1 to 20 parts by weight based on 100 parts by weight of the binder resin.

Examples of the release agent include polyolefin,
Fatty ester wax, higher alcohol, paraffin wax, polyamide wax, etc.
JISK2531) A wax at 60 to 150 ° C is used.

As the charge control agent, those conventionally known can be used, and examples thereof include a quaternary ammonium salt compound, a triphenylmethane compound, a nigrosine dye, and a metal-containing dye.

Further, other external additives may be added to the toner as required.

For example, hydrophobic silica as a fluidization improver,
A fixing property improving agent, a charge controlling agent, a cleaning improving agent and the like can be used.

The particle size and the production method of the toner are as follows. The binder resin contains a colorant, various additives are added as necessary, and the mixture is mixed by a Henschel mixer or the like, and the mixture is subjected to kneading, pulverizing, and classification steps. A toner can be obtained. Other production methods can also be obtained by methods such as spray drying, interfacial polycondensation, suspension polycondensation, and solution polycondensation. Usually, the volume average particle diameter of these toners is preferably about 5 to 20 μm.

(3) Developer A toner is prepared by mixing a toner and a carrier. The mixing ratio of the two is preferably 0.3 to 20 parts by weight of the toner with respect to 100 parts by weight of the carrier.

(4) Recycling System Next, the image forming method of the present invention will be described. In the image forming method of the present invention, a two-component developer including the carrier and the toner is used, the toner remaining on the photoreceptor without being transferred is collected by a cleaning device, and the collected toner is developed by a developing device or a toner replenisher. An image is formed by adopting a toner recycling system which is returned to the apparatus and reused. FIG. 1 shows an example of an image forming apparatus applicable to the image forming method of the present invention. Reference numeral 20 denotes a photoconductor.
Has a rotary drum shape. The charger 21, the exposure optical system 22, the developing unit 23, the transfer unit 25, and the separator 2 are arranged around the photoreceptor 20 in order from the upstream side to the downstream side in the rotation direction.
6. A blade-type cleaning device 27 is provided. 28
Denotes a heat roller fixing device, and 29 denotes a cleaning blade.

In this image forming apparatus, the surface of the photoreceptor 20 is charged to a uniform potential by the charger 21, and then image-exposed by the exposure optical system 22, and the surface of the photoreceptor 20 is electrostatically charged on the surface of the photoreceptor 20. A latent image is formed. This electrostatic latent image is developed by the developer contained in the developing device 23 to form a toner image corresponding to the document. This toner image is transferred onto the transfer material P by the transfer device 25, and is heat-fixed by the heat roller fixing device 28 to form a fixed image. The photoreceptor 20 that has passed through the transfer unit 25 has its surface cleaned and rubbed by a blade-type cleaning unit 27 so that the residual toner is scraped off, and is again subjected to a charging step by the charging unit 21. To form the next image. The toner collected by the cleaning is returned to the developing device 23 again by the toner recycling system described later in detail, and is reused.

FIGS. 2 and 3 show specific examples of the toner recycling system. In the example shown in FIG. 2, reference numeral 30 denotes a collecting drum. The collecting drum 30 is coaxial with the photosensitive member via a partition (not shown) at one end of a drum-like photosensitive member (not shown). The recovery drum 30
A plurality of magnets 31 are fixedly provided along the outer periphery of the collection drum 30. A conveyance belt 32 is suspended around the outer periphery of the collection drum 30. Reference numeral 33 denotes a cleaning mechanism. The cleaning mechanism 33 extends so as to face the cleaning area of the photoconductor and also face the collection drum 30. In the cleaning mechanism 33, the toner remaining on the photoreceptor is scraped and collected by, for example, a blade or the like, and the collected toner is supplied to the outlet 35 side by a screw conveyor 34 provided therein. . Reference numeral 36 denotes a developing mechanism.The developing mechanism 36 includes a rotary drum-shaped magnetic brush mechanism 37 that faces the development area of the photoconductor and also faces the collection drum 30, a developer stirring mechanism 38, And a toner receiving and distributing mechanism 39 for receiving and distributing the collected toner into the developing mechanism 36.After the transport belt 32 passes through the gap between the collecting drum 30 and the magnetic brush mechanism 37, Exit of collection drum 30 and cleaning mechanism 33
The collection drum 30 and the rollers 40 and 41 are suspended from the collection drum 30 so as to reach the toner receiving and distributing mechanism 39 of the developing mechanism 36 via the gap between the collecting drum 30 and the roller 35. 37a is a rotary sleeve, 37b is a magnet.

In this example, when the transport belt 32 is moved, when the transport belt 32 passes through the gap between the collection drum 30 and the magnetic brush mechanism 37, the transport belt 32 is placed on the transport belt 32 by the magnetic brush mechanism 37. When a magnetic brush of developer is formed and the magnetic brush is transferred to the cleaning mechanism 33 along with the movement of the conveyor belt 32, the magnetic brush is collected from the photoconductor by the cleaning mechanism 33 and supplied to the outlet 35 side by the screw conveyor 34. The picked-up toner is picked up by the magnetic brush on the conveyor belt 32, and the toner picked up by the magnetic brush by the movement of the conveyor belt 32 is transferred to the toner receiving and distributing mechanism 39, where the toner is developed by the developing mechanism 36.
The collected toner is again used for developing the latent image on the photoconductor.

In the example shown in FIG. 3, reference numeral 51 denotes a developing mechanism, 52 denotes a cleaning mechanism, 53 denotes a toner receiving and distributing mechanism, 54 denotes a magnetic brush mechanism, 55 denotes a photosensitive member, 56 denotes a screw conveyor, and 57 denotes a first screw. Reference numeral 58 denotes a second screw. In this embodiment, the first screw 57 and the second screw 58 supply the toner from the screw conveyor 56 to the toner receiving and distributing mechanism 53. That is, the first screw 57 and the second screw 58
Has a rotating shaft and blades provided spirally along the rotating shaft, respectively. In the first screw 57, the toner sent by the screw conveyor 56 is rotated by the rotation of the rotating shaft. Are sequentially pushed up and sent to the second screw 58. In the second screw 58, toner is sequentially sent in the horizontal direction according to the same principle as the first screw 57, and is supplied to the toner receiving and distributing mechanism 53.
The collected toner is again used for developing the latent image on the photoconductor 55.

[0052]

EXAMPLES The present invention will be described below in detail with reference to examples, but embodiments of the present invention are not limited thereto.

(Manufacture of Carrier) (1) Carrier C1 to C4 A coating resin solution obtained by dissolving 1 part by weight of a condensation-reaction type silicone resin in 50 parts by weight of xylene was used.
Of ferrite particles of 100 parts by weight. The xylene was removed by heating, followed by heat treatment at 200 ° C. for 3 hours for sintering. Then, the aggregates were sieved to obtain a carrier having a silicone resin coating layer. Then, 1000 kg of the carrier was stirred for several hours by a ball mill. By the above operation, carriers C1 to C4 were obtained according to the stirring time. The magnetizations were all 65 (emu / g). For the above carriers, using a Shimadzu X-ray photoelectron analyzer (ESCA-1000 manufactured by Shimadzu Corporation), the X-ray output was 10 kV, 40 mA, silicon = Si 2p, carbon = C 1s, oxygen = O 1s, iron = Fe The element ratio was calculated from the element peak area intensity of 2p3 / 2, copper = Cu 2p3 / 2, and zinc = Zn 2p3 / 2. On the other hand, the same measurement was carried out for the core material (core), and the results were obtained assuming that the core exposure amount (%) = (Fe ratio of coat carrier) / (Fe ratio of core material) × 100.
Shown in

[0054]

[Table 1]

(2) Carrier C5 Spray-coating 8 parts by weight of the above condensation reaction type silicone resin solution to 100 parts by weight of magnetite particles having a volume average particle diameter of 100 μm (manufactured by Kanto Denka Co., Ltd.) using a tumbling fluid coating apparatus. Further, heat treatment was performed at 180 ° C. for 4 hours, and then the aggregates were sieved to obtain a carrier having a coating layer made of a silicone resin. Then, 5,000 kg of the carrier was treated with a high-speed stirring mixer for 5 minutes to obtain a carrier C5 (for the present invention). The core exposure of this carrier was 3.8%, the magnetization was 80 emu / g, and the coating amount was 0.8%.

(Production of Inorganic Fine Particles) (Inorganic Fine Particles A) Silica fine particles 10 having a primary average particle diameter of 12 nm
0 parts by weight is put into a high-speed rotation mixer, and a processing solution obtained by dissolving 10 parts by weight of N-β (aminoethyl) γ-propyltrimethoxysilane and 10 parts by weight of hexamethylsilazane in 100 parts by weight of hexane is put into a high-speed rotation mixer. Surface treatment was performed by dropwise addition, and then hexane was removed by performing a heat treatment at a temperature of 120 ° C. for 5 hours in an inert gas atmosphere. This is designated as inorganic fine particles A.

(Inorganic fine particles B) 100 parts by weight of titanium oxide fine particles having a primary average particle diameter of 15 nm and octylmethoxysilane 8
The same heat treatment was carried out except for using parts by weight. Thereafter, the ejector was crushed. This is designated as inorganic fine particles B.

(Production of Toner) (1) Toners T1 to T4 100 parts by weight of a styrene-acryl copolymer, 8 parts by weight of carbon black, 2 parts by weight of a charge control agent (nigrosine dye), and 3 parts by weight of polypropylene After mixing, the mixture was melt-kneaded, cooled and pulverized and classified to obtain colored particles having a volume average particle size of 8.0 μm. 0.8% by weight of inorganic fine particles A was added to the colored particles, and the mixture was placed in a high-speed stirring type mixer, and mixed and stirred at a rotation speed of 40 m / s for 1 to 20 minutes while cooling the jacket.
Toners T1 to T4 were manufactured according to the mixing time. Table 2 shows the primary average particle diameter of the inorganic fine particles A and the number average diameter of the aggregated particles of each toner.

[0059]

[Table 2]

(2) Toner T5 100 parts by weight of polyester resin, 10 parts by weight of carbon black, charge control agent (triphenylmethane compound) 1
After mixing with 3 parts by weight of polypropylene and 3 parts by weight of polypropylene, the mixture was melt-kneaded, cooled, pulverized and classified to obtain colored particles having a volume average particle size of 9.5 μm. 0.6% by weight of inorganic fine particles B were added to the colored particles, and the same treatment was performed for 1 minute. At this time, the inorganic fine particles B had a primary average particle size of 15 nm and a number average particle size of the aggregated particles.
It was 60 nm. The above toner was used as toner T5 (for the present invention)
And

<Examples 1 to 10 and Comparative Examples> In each of the examples and comparative examples, the developers 1 to 13 were prepared using the carriers and toners in the combinations and the amounts shown in Table 3. The amount is expressed in parts by weight.

The developer obtained in Examples 1 to 5 was used as developer 1
To 5, and the developer obtained in Comparative Examples 1 to 8 was used as the developer 6 to
13

[0063]

[Table 3]

<Practical photo test> Electrophotographic copier U-BIX3035
(Manufactured by Konica Corporation), a cleaning device that collects the toner remaining on the photoreceptor without being transferred, and returns the collected toner to a developing device to be reused. A 100,000-copy actual photography test (environmental conditions: temperature 20 ° C., relative humidity 55%) was performed and the following items were evaluated. The results are shown in Tables 4 and 5.

(Image density) Macbeth densitometer (RD-91)
According to 8), the absolute reflection density of the solid black portion of the copy image is set to 4
The points were measured and the average was shown.

(Fogging) The density of the copy image corresponding to the white portion of the transfer paper was measured with a Sakura Densitometer (manufactured by Konica Corporation), and the relative density when the density of the paper itself was set to 0 was determined. Was. When the concentration is less than 0.01, there is no practical problem.

(Resolution) An original on a white paper having black lines drawn at equal intervals in a width of 1 mm was copied, and the number of lines drawn in a width of 1 mm was indicated by whether each line could be identified.

The number of fine lines actually drawn is 2.0, 2.2, 2.5, 2.8, 3.2, 3.6, 4.0, 4.5, 5.0, 5.
6, 6.3, 7.1 and 8.0.

(Scattering of Toner) A blank paper is placed under the developing area, the scattering toner is adhered, the blank paper is fixed under the same conditions as in the evaluation machine, and the density is measured by a Sakura densitometer using a white paper on a white background. The relative concentration corresponding to is measured, and when the relative concentration is less than 0.01, `` ○ '', 0.01 or more and 0.02
The case where the value was less than “を”, and the case where the value was 0.02 or more was “×”.
(Carrier Attachment) The presence or absence of carrier adherence was visually determined from the copied image.

(Spent) The carrier alone was separated from the developer using a surfactant, 3.0 g of the carrier was placed in 100 ml of methyl ethyl ketone, the spent material was dissolved, and the transmittance of the solution at 500 nm was measured by a spectrophotometer ( The value was used as the amount of spent (carrier contamination degree). 10 if no spent
0%, and the value decreases as the spent increases. 100
"~" For ~ 90%, "％" for 90-70%, 70%
In the following cases, the charge amount of the developer was remarkably reduced, causing toner scattering and fogging.

[0071]

[Table 4]

[0072]

[Table 5]

As is clear from Tables 4 and 5, Examples 1 to
In No. 5, the image density was stable up to 100,000 copies, no fogging, toner scattering and carrier adhesion occurred, and good image quality with high resolution was obtained. In addition, no spent was observed, and sufficient durability was obtained in a copying machine equipped with a recycling system. On the other hand, in Comparative Examples 1 to 3 and 5 to 8, the balance between the carrier core material (core) exposure amount and the presence state (agglomerated particle diameter) of the inorganic fine particles in the toner was poor, so that fog and toner scattering were caused by the occurrence and increase of spent. , The resolution is reduced, and the durability is significantly reduced.
In particular, in Comparative Examples 3, 5, and 8, carrier adhesion also occurred on images due to excessive surface exposure of the carrier core. In Comparative Example 4, the image density was significantly lower than at the beginning of the actual shooting test, and remained low over 100,000 copies.

[0074]

According to the present invention, the following effects can be obtained.

(1) To provide a developer capable of preventing carrier adhesion and obtaining a stable high-density, high-quality image.

(2) It is possible to provide a developer having good durability, which is free from fogging and fogging and toner scattering.

(3) To provide a developer capable of obtaining a high-density, high-quality image for a long period of time even when a toner recycling system is employed.

[Brief description of the drawings]

FIG. 1 is an image forming apparatus applied to the present invention.

FIG. 2 is a schematic diagram illustrating an example of a toner recycling system.

FIG. 3 is a schematic diagram showing another example of a toner recycling system.

[Explanation of symbols]

 20 Photoconductor 21 Charger 22 Exposure optics 23 Developing unit 25 Transfer unit 26 Separator 27 Blade type cleaning unit 28 Heat roller fixing unit 29 Cleaning blade 30 Collection drum 31 Magnet 32 Conveying belt 33 Cleaning mechanism 34 Screw conveyor 35 Exit 36 Development Mechanism 37 Magnetic brush mechanism 37a Rotating sleeve 37b Magnet 38 Developer stirring mechanism 39 Toner receiving and distributing mechanism 40 Roller 41 Roller 51 Developing mechanism 52 Cleaning mechanism 53 Toner receiving and distributing mechanism 54 Magnetic brush mechanism 55 Photoconductor 56 Screw conveyor 57 First screw 58 2nd screw

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 9/08 G03G 9/10

Claims (3)

(57) [Claims] A magnetic material is used as a core material, and the core material is 0.1 to 10.
The carrier coated with resin except for the core material surface of 0%, the primary average particle size is 5 to 20 nm, and the number average particle size of the aggregated particles is 30.
A two-component developer for developing an electrostatic image, comprising a toner to which inorganic fine particles having a thickness of up to 500 nm are added. 2. A two-component developer comprising a carrier and a toner, wherein a toner remaining on the photoreceptor without being transferred is collected by a cleaning device, and the collected toner is returned to a developing device or a toner replenishing device for reuse. An image forming method employing a toner recycling system, wherein a magnetic material is used as a core material, and the core material is resin-coated with a core material surface of 0.1 to 10.0%, and the primary average particle size is 5 to 20 nm. An image forming method using a two-component developer for developing an electrostatic image, comprising a toner to which inorganic fine particles having a number average particle diameter of 30 to 500 nm of aggregated particles are added. 3. The two-component developer for electrostatic images according to claim 1, wherein the coating resin of the carrier is a silicone resin.