JPH10186732A - Electrostatic image developing carrier, its manufacture, and electrostatic image developer and developing method using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably exhibit satisfactory charging starting characteristic over a long period, and prevent the occurrence of toner scattering or image fogging. SOLUTION: In a method of manufacturing an electrostatic image developing carrier for forming a resin coat layer in which a magnesium atom-contained material is dispersed and contained in the surface of a magnetic body particle by means of dry coating of adhering and fixing the resin particle and the magnesium atom-contained material to the surface of the magnetic body particle by imparting a mechanical impact, not the three kinds of the materials are simultaneously stirred and mixed, but after the magnetic body particle and the resin particle are stirred and mixed together, the magnesium atom-contained material is added to the resulting mixture. Thus, the magnesium atom-contained material is unevenly distributed on the surface part of the carrier, and the negative charge imparting property to toner is thus improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier for developing an electrostatic image used in a copying machine, a printer, and the like, a method of manufacturing the same, and a developer and a developing method of an electrostatic image using the same.

[0002]

2. Description of the Related Art In general, as a two-component developer used in an image forming method such as a copying machine or a printer using an electrophotographic system, a toner having a negative charge and a toner having a positive charge are generally used. And a mixture of these carriers. The carrier is used for imparting an appropriate amount of negative triboelectric charge to the toner.

However, recently, there has been a tendency to reduce the size of an image forming apparatus to which the electrophotographic method such as a laser printer is applied, and accordingly, the size of the image forming apparatus itself and especially the developing apparatus including a developing unit have been reduced. Have been. Therefore, in a small-sized developing device, the amount of the developer used for developing the electrostatic latent image is inevitably reduced.

In the above-described two-component type negatively chargeable developer, an appropriate amount of negatively triboelectric charge is generated in a short time until the replenished toner is transported to the development area of the electrostatic latent image. It is necessary to impart the toner to the toner, that is, to improve the charge rising characteristics.

[0005] Under such circumstances, as a means for improving the charge rising characteristics of a negatively chargeable developer, a technique of adding a positively chargeable charge control agent to a resin coating layer of a resin-coated carrier has been introduced. (See, for example, JP-A-2-8860).

Here, as a positively chargeable charge control agent,
JP-A-49-51951 and JP-A-52-1014
No. 1 quaternary ammonium compound,
JP-A-56-11461 and JP-A-54-1589
No. 32, an alkylpyridinium compound, an alkylpicolium compound (for example, Nigrosine S)
O, nigrosine EX, etc.) are known.

However, the conventionally known positively chargeable charge control agents are organic compounds having a large cohesive force and are inferior in dispersibility and mixing with the coating resin. For this reason, the above-mentioned positively-chargeable charge control agent cannot be uniformly dispersed and contained in the resin coating layer of the carrier, and an appropriate amount of negative triboelectric charge cannot be given to the toner, There is a problem that toner scattering and image fogging due to poor charging occur.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a carrier for developing an electrostatic charge image which can exhibit good charge rising characteristics stably over a long period of time and does not cause toner scattering or image fogging, and its production. An object of the present invention is to provide a method, an electrostatic image developer using the same, and a developing method.

[0009]

The object of the present invention is achieved by adopting the following constitution.

[0010] (1) By dry coating in which resin particles and a magnesium atom-containing material are applied and fixed by applying a mechanical impact to the surface of the magnetic particles, the magnesium atom-containing material is applied to the surface of the magnetic particles. A method for producing a carrier for developing an electrostatic image, in which a dispersed / contained resin coating layer is formed, wherein a magnesium atom-containing material is added to the mixture after stirring and mixing the magnetic particles and the resin particles. A method for producing a carrier for developing electrostatic images.

(2) The carrier for developing an electrostatic image according to (1), wherein the magnesium atom-containing material is magnesium oxide produced by a wet method for producing magnesium hydroxide by thermal decomposition. Production method.

(3) The dry coating in which the resin particles and the magnesium atom-containing material are applied and fixed by applying a mechanical impact to the surface of the magnetic particles, so that the surface of the magnetic particles is coated with the magnesium atom-containing material. In a carrier for developing an electrostatic image, in which a dispersed / contained resin coating layer is formed, after stirring and mixing magnetic particles and resin particles, a magnesium atom-containing material is added to the mixture to produce the mixture. Carrier for developing an electrostatic image.

(4) An electrostatic image developer characterized by being manufactured by mixing a toner comprising at least a colorant and a binder resin with the carrier for developing an electrostatic image according to (3).

(5) A development method characterized in that development is performed by a non-contact two-component system using the electrostatic image developer according to (4).

Hereinafter, the present invention will be described in detail.

<Carrier Production Method of the Present Invention> The carrier production method of the present invention comprises the steps of:
A method for producing a carrier for developing an electrostatic image, characterized by forming a resin coating layer on the surface of magnetic particles by dry coating in which a magnesium atom-containing material is applied and fixed by applying a mechanical impact, It has a great feature in that after mixing and mixing magnetic particles and resin particles to prepare a mixture, a magnesium atom-containing material is added to the mixture.

Conventionally, a magnesium atom-containing material is added simultaneously with magnetic particles and resin particles, followed by stirring and mixing to form a resin coating layer in which the magnesium-containing material is dispersed and contained on the surface of the magnetic particles. The formed electrostatic charge image developing carrier was able to be manufactured. However, the carrier produced by this method has not yet had a sufficient negative charge imparting property to the toner, and was unable to maintain good charge rising characteristics over a long period of time.

As a result of intensive studies, the magnesium-containing material according to the present invention is added after stirring and mixing the magnetic particles and the resin particles, so that the carrier can be compared with a carrier manufactured by a conventional method. It has been found that a magnesium atom-containing material can be unevenly distributed on the surface portion of the toner, and as a result, it is possible to sufficiently impart a negative charge to the toner, leading to the present invention. That is, according to the present invention, it is possible to maintain good charge rising characteristics of the developer for a long period of time.

<Constituent Material of Carrier for the Present Invention> As the magnetic particles constituting the carrier, substances which are strongly magnetized in the direction by a magnetic field, for example, iron, ferrite, magnetite and other iron, nickel, cobalt, etc. Metals or alloys exhibiting magnetism or compounds containing these elements, alloys which do not contain ferromagnetic elements but exhibit ferromagnetism by appropriate heat treatment, such as manganese-copper-
An alloy of a type called a whistler alloy such as aluminum or manganese-copper-tin, or magnetic particles such as particles made of chromium dioxide can be used.

The shape of the magnetic particles is not particularly limited.
It is preferably spherical. The specific gravity of the magnetic particles is preferably in the range of 3 to 7 from the viewpoint of preventing the destruction of the resin coating layer and the fusion of toner constituents to the carrier surface when the mixture is stirred in the developing device.

The carrier of the present invention takes into consideration the stability of charge application to the toner, the ability to supply the toner to the electrostatic latent image portion, the transfer of the carrier to the electrostatic latent image portion (carrier adhesion), and the like. Those having a volume average particle size of 15 to 80 μm can be preferably used.

The measurement of the volume average particle size of the carrier is as follows.
It was measured using a laser diffraction particle size distribution analyzer “HELOS” (manufactured by JEOL Ltd.). In the measurement, the carrier particles were dispersed in a 50 cc beaker with a measurement sample, a surfactant, and water as a dispersion medium, and then the ultrasonic homogenizer with an output of 150 W for 120 seconds.

Examples of the magnesium atom-containing material constituting the carrier of the present invention include magnesium oxide, magnesium hydroxide, magnesium carbonate and a mixture thereof, or a composite oxide of magnesium and a metal such as calcium, aluminum, silicon and the like. However, among these, magnesium oxide produced by a wet method for producing magnesium hydroxide by thermal decomposition can be preferably used.

It is preferable that the magnesium atom content in the surface portion of the magnesium atom-containing material is 20 to 40 [atomic number%]. Within this range, when used as a carrier constituent material, the ability of the carrier to impart negative charge to the toner can be significantly improved. Here, the measurement of the content of magnesium atoms in the surface portion of the magnesium atom-containing material can be performed in the same manner as the measurement of the content of magnesium atoms in the surface portion of the carrier.

The content of magnesium atoms in the surface portion of the carrier and the surface portion of the magnesium atom-containing material can be measured using an X-ray photoelectron spectrometer (XPS). Specifically, using an X-ray photoelectron spectrometer “ESCA-1000” (manufactured by Shimadzu Corporation), quantitative analysis of each element was performed under the following analysis conditions.
The content of magnesium atoms is calculated from the respective atomic peak areas by the following formula.

[0026]

(Equation 1)

[Analytical conditions] X-ray: Mg anode type (1253.6 eV) Acceleration: 10 kV, 30 mA Resolution: 31.5 eV Measurement elements: carbon, oxygen, iron, silicon, magnesium Usually, it is produced in a range of 0.05 to 6.0% by weight based on magnetic particles (core material particles) such as ferrite particles.

Further, an intermediate layer made of a resin or other material may be provided between the coating resin and the core material particles for controlling a carrier resistance value or for various other purposes.

Further, the magnesium atom-containing material B
The ET specific surface area is preferably in the range of 20 to 300 m ² / g, and the number average particle diameter is preferably in the range of 10 nm to 3 μm. When the BET specific surface area and the number average particle diameter are in these ranges, the magnesium atom-containing material can be uniformly dispersed and contained in the resin coating layer, and as a result, the negative charge imparting property to the toner is remarkably improved. This is because it can be done.

Here, the BET specific surface area of the magnesium atom-containing material was measured by using Micromeritics Flow Soap II 2300 manufactured by Micromeritics.
It was measured by type.

The term "number average particle diameter" as used herein refers to the number average particle diameter of primary particles (particles in a state of being separated into individual unit particles) of a magnesium atom-containing material existing in fine particles. Transmission Electron Microscope (TEM) "J
It refers to a number average particle diameter measured by taking a photographic image observed and photographed with "EM-2000FX" (manufactured by JEOL Ltd.) into an image analyzer "SPICCA" (manufactured by Nippon Avionics).

As the coating resin constituting the carrier,
The material is not particularly limited as long as it can impart a negative triboelectric charge to the toner by friction with the toner. Examples thereof include a styrene resin, an acrylic resin, a styrene-acrylic copolymer resin, and a blend thereof. Resins and the like are preferable from the viewpoints of charge-imparting property and ability to form a coating layer (film-forming property).

The glass transition point (Tg) of the coating resin is 50 to 200 ° C. and the softening point (Tsp) is 8
Those having a temperature of 0 to 300 ° C. are preferred because they have high fixability to the surface of the core material particles and can improve durability.
Glass transition point (Tg) and softening point (Ts) of coating resin
p) can be controlled by selecting the composition and molecular weight of the resin. Here, the glass transition point (Tg) is D
A value measured by SC “506S” (manufactured by Seiko Denshi Co., Ltd.) (the same applies to the following), and the softening point (Tsp) is measured by the Koka type flow tester “CFT-50”.
"0" (manufactured by Shimadzu Corporation) (hereinafter the same).

The resin for coating is preferably in the form of spherical fine particles.
It is preferably from 1 to 10 μm. Such a particulate resin can be prepared by suspension polymerization, emulsion polymerization, soap-free emulsion polymerization, or the like. Here, the number-average primary particle size of the coating resin is measured by a particle size distribution analyzer “LPA-3”.
000/3100 "(manufactured by Otsuka Electronics Co., Ltd.) (the same applies hereinafter).

<Developer of the Present Invention> The developer of the present invention uses a carrier in which the content of magnesium atoms in the surface portion of the carrier is in a specific range, and colored particles containing at least a binder resin and a colorant. It is characterized in that the toner is composed of

Examples of the binder resin constituting the toner include a styrene resin, an acrylic resin, a styrene-acrylic copolymer resin, a styrene-butadiene copolymer resin, an epoxy resin, a polyester resin, and other conventionally known binder resins. An adhesive resin can be used.

<Developing Method of the Present Invention> As the developing device used in the present invention, the developing device is disposed so as to face the electrostatic image carrier.
A layer of the developer is formed on a developer carrier made of a non-magnetic material such as aluminum or SUS, which contains a large number of N and S magnet rolls therein, and the developer carrier is rotated. The developer layer is brought into contact with or close to the electrostatic latent image portion on the electrostatic image carrier while the latent image portion is being visualized using colored particles (toner).

As a method for regulating the developer layer formed on the developer carrier for developing the electrostatic latent image on the electrostatic charge image carrier, a metal having rigidity on the developer carrier is used. This can be achieved by placing a rod or a metal plate in parallel with the developer carrying member, or by pressing the rod or metal plate onto the developer carrying member. In addition, SUS, aluminum, and other conventionally known metals can be used for the metal bar or metal plate.
The metal rod or metal plate may be either magnetic or non-magnetic.

Furthermore, it is desirable to use a developing method in which the developer layer formed on the developer carrying member is brought into close contact with the latent image portion in a non-contact state to visualize the latent image with toner. In this case, the thickness of the developer layer cannot be determined unconditionally depending on the distance between the developer carrier and the electrostatic charge image carrier (distance Dsd between the photosensitive member and the sleeve), but is １ ／ to ４ of Dsd.
Is preferably set in the range. For example, if Dsd is 50
When the thickness is set to 0 μm, the thickness of the developer layer is set to 100
It can be said that it is preferable to set the range to 400 μm.

When the thickness of the developer layer is less than 1/5 of the set Dsd (the thickness of the developer layer is less than 100 μm for Dsd = 500 μm), the electrostatic latent image on the electrostatic image carrier is The electrostatic latent image cannot be sufficiently developed because the ability to supply the developer to the portion is too small. Further, the thickness of the developer layer is set to less than 4/5 of the set Dsd (Dsd =
When the developer layer thickness is less than 400 μm with respect to 500 μm), the carrier in the developer closest to the electrostatic image carrier is transferred to the electrostatic image carrier, and the electrostatic image is removed. It is not preferable because the carrier is damaged.

For other components, a conventionally known device can be used.

[0042]

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

<Production Example 1 of Carrier> The volume average particle size is 4
Magnetic particles having a magnetite composition of 5 μm (specific gravity 5.
2 g / cm ³ ) and a number average particle size of 2.
5 μm cyclohexyl methacrylate-methyl methacrylate copolymer resin (Tg = 111 ° C., Tsp =
270 ° C.) and 2.8 parts by weight were stirred and mixed in a high-speed stirring type mixer at a material temperature of 30 ° C. and a peripheral speed of the stirring blade of 10 m / sec for 20 minutes to obtain the surface of the magnetic particles. After preparing a mixture to which the coating resin was adhered, the number average particle diameter was 0.8 μm, and the BET specific surface area was 76 m ^2.
/ G and 1.2 parts by weight of a wet-processed magnesium oxide having a magnesium atom content of 40 [atomic%] in the surface portion and adding 20 parts by weight under the same conditions.
After mixing for minutes, a mixture in which the coating resin and the magnesium atom-containing material were adhered to the surfaces of the magnetic particles was prepared.

Next, while heating the mixture to a material temperature of 120 ° C., the mixture was similarly stirred and mixed for 20 minutes in a high-speed stirring type mixer at a peripheral speed of a stirring blade of 10 m / sec. By applying force, a carrier 1 of the present invention was formed in which a resin coating layer containing magnesium oxide dispersed and contained on the surface of magnetite magnetic particles was formed.

<Carrier Production Example 2> Carrier 2 of the present invention was prepared in the same manner as in Carrier Production Example 1, except that the stirring time of the magnetic particles and cyclohexyl methacrylate-methyl methacrylate copolymer resin was set to 60 minutes. Produced.

<Production Example 1 of Comparative Carrier> 100 parts by weight of magnetic particles (specific gravity: 5.2 g / cm ³ ) having a magnetite composition having a volume average particle diameter of 45 μm and a number average particle diameter of 2.5 μm. Cyclohexyl methacrylate-methyl methacrylate copolymer resin (Tg = 111 ° C., Ts
(p = 270 ° C.) was 2.8 parts by weight and the number average particle size was 0.8 μm.
m, a BET specific surface area of 76 m ² / g, and a magnesium atom content of 40 [atomic%] in the surface portion of magnesium oxide produced by a wet method.
And 2 parts by weight are all added simultaneously into a high-speed stirring type mixer, and are stirred and mixed for 20 minutes at a material temperature of 30 ° C. and a peripheral speed of a stirring blade of 10 m / sec. A mixture was prepared by adhering the coating resin and the magnesium atom-containing material.

Thereafter, the mixture is heated to a material temperature of 120 ° C.
In a high-speed stirrer-type mixer, the mixture was stirred and mixed for 20 minutes at a peripheral speed of the stirring blade of 10 m / sec.
By repeatedly applying a mechanical impact force, Comparative Carrier 1 in which a resin coating layer containing magnesium oxide dispersed and contained on the surfaces of magnetite magnetic particles was formed was produced.

<Production Example of Toner> Polyester resin having 120P composition 100 parts by weight Carbon black 10 parts by weight Polypropylene 4 parts by weight The above compounds are mixed, kneaded, pulverized, and classified to give colored particles having a volume average particle size of 8.5 μm. Was prepared. Here, the volume average particle diameter of the colored particles is expressed by a Coulter counter TA-
It is a value measured with a type II (manufactured by Coulter).

To 100 parts by weight of the colored particles, 0.6 parts by weight of hydrophobic silica fine particles (particle diameter: 12 nm) and hydrophobic titania fine particles (particle diameter: 20 nm) were added, and then mixed using a Henschel mixer. And a toner.

<Examples 1 and 2 and Comparative Example 1> 93 parts by weight of each of Carriers 1 and 2 and Comparative Carrier 1 and 3 parts by weight of the toner were mixed by using a V-type mixer. A developer of the present invention (developers 1 and 2) and a developer for comparison (developer 1) were produced.

<Actual Photographic Test> For each of the developers 1 and 2 of the present invention and the comparative developer 1 manufactured as described above, an electrophotographic copying machine “Konica 7050” was used.
Using a remodeled machine (manufactured by Konica Corporation), 100,000 actual shooting tests were performed under the following conditions, and the presence or absence of in-machine contamination and image fogging due to toner scattering was evaluated.

The evaluation method of the above two items is as follows.

In-machine contamination due to toner scattering After the actual copying test was performed every 10,000 times, the inside of the copying machine was visually inspected. (○) when contamination inside the machine (near the sleeve) is observed, “△” when contamination inside the machine is observed on the entire top cover of the developing unit, almost all of the inside of the copier is contaminated by toner scattering, which is a practical problem. The case was marked "x".

Image Fogging Occurrence The relative density of a white background portion of each output image after the actual shooting test was performed every 10,000 times was measured using an image density measuring device “RD-
918 "(manufactured by Macbeth). If the measured value exceeds 0.1, there is a practical problem.

The remodeling points and image forming conditions used for image formation are as follows.

Remodeling point and image forming conditions Vh = −750 V Vl = −50 V DC component of developing bias: −650 V AC component of developing bias: Frequency 8 kHz, 2.6 kV Distance between photoconductor and sleeve: 550 μm Developer layer thickness: The developer layer regulating portion inside the developing device was modified so that the thickness of the developer layer became a set value.

Material of developer carrier (sleeve): aluminum Metal bar regulated by developer layer: nonmagnetic SUS, 6 mm diameter round bar.

Combination of image output environment and original blackening ratio: See Table 1 below.

[0059]

[Table 1]

Table 2 shows the results of contamination inside the apparatus due to toner scattering, and Tables 3 and 4 show the results of measurement of the relative image density in the white background.

In Comparative Example 1, the actual shooting test was stopped at 30,000 times because toner scattering and image fogging occurred remarkably.

[0062]

[Table 2]

[0063]

[Table 3]

[0064]

[Table 4]

As is clear from Tables 2 to 4, when the developer 12 of the present invention is used, good charging start-up characteristics can be stably exhibited over a long period of time, and its performance depends on the environment. Is not affected. A good image can be output without causing toner scattering or image fogging even after a total of 100,000 actual shooting tests.

[0066]

According to the present invention, a carrier for developing an electrostatic image capable of stably exhibiting a good charge rising characteristic over a long period of time without causing toner scattering and image fogging, and a method for producing the same, and a method for producing the same are provided. An electrostatic image developer and a developing method can be provided.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Ryuji Kitani 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation

Claims (5)

[Claims] 1. A method in which a resin particle and a magnesium atom-containing material are applied and fixed on a surface of a magnetic particle by applying a mechanical impact to the surface of the magnetic particle to disperse the magnesium atom-containing material on the surface of the magnetic particle. In the method for producing a carrier for developing an electrostatic image for forming a contained resin coating layer, after stirring and mixing the magnetic particles and the resin particles,
A method for producing a carrier for developing an electrostatic image, comprising adding a magnesium atom-containing material to the mixture. 2. The magnesium atom-containing material is magnesium oxide produced by a wet method for producing magnesium hydroxide by thermal decomposition.
3. The method for producing a carrier for developing an electrostatic image according to item 1. 3. The magnesium atom-containing material is dispersed on the surface of the magnetic particles by dry coating in which resin particles and a magnesium atom-containing material are applied and fixed by applying a mechanical impact to the surface of the magnetic particles. In the carrier for developing an electrostatic image in which the contained resin coating layer is formed, after stirring and mixing the magnetic particles and the resin particles, a magnesium atom-containing material is added to the mixture to produce the mixture. Carrier for developing electrostatic images. 4. An electrostatic image developer, wherein the electrostatic image developer according to claim 3 is mixed with a toner comprising at least a colorant and a binder resin. 5. A developing method using the electrostatic charge image developer according to claim 4 and developing by a non-contact two-component system.