JP2872480B2 - Magnetic dispersion carrier, two-component developer for electrostatic image development, method for producing magnetic dispersion carrier, 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 magnetic material-dispersed carrier and a method for producing the same. The present invention also relates to a two-component developer for developing an electrostatic image having a toner and a carrier. Further, the present invention relates to an image forming method for developing a latent image with a two-component developer having a toner and a carrier by applying a bias voltage in a developing area.

[0002]

2. Description of the Related Art Generally, in an electrostatic recording apparatus using electrophotography, selenium, OPC (organic photoconductor), α-S
Using a photoconductive material such as i as a photoreceptor, the photoreceptor is uniformly charged by various means, and then illuminated with a light image on the photoreceptor surface to form an electric latent image corresponding to the light image. In general, a method is used in which a latent image is formed on the surface of a photoreceptor, toner is adhered to the latent image using a magnetic brush developing method or the like, and the latent image is visualized.

In this developing method, toner for visualizing the latent image and carrier particles having a magnetic material called a carrier are used, and the carrier generates an appropriate amount of positive or negative electricity by triboelectric charging. The toner is applied to the toner, and the toner is carried on the surface by the electrostatic attraction of the triboelectric charging.

[0004] The developer having the toner and the carrier is
A developing layer containing a magnet is coated to a predetermined layer thickness by a developer layer thickness regulating member, and is conveyed to a developing area formed between the photoreceptor and the developing sleeve by using a magnetic force. You.

A predetermined developing bias voltage is applied between the photosensitive member and the developing sleeve, and the toner is developed on the photosensitive member in the developing area.

There are various characteristics required for the above-mentioned carrier, but particularly important characteristics are appropriate charging properties, pressure resistance to an applied electric field, impact resistance, abrasion resistance, abrasion resistance, spent resistance, developability, and productivity. And the like.

For example, when a developer is used for a long time,
Toner filming occurs in which toner, which does not contribute to development, which is called spent toner, is fused to the surface of the carrier, and as a result, the developer deteriorates and the image quality of a developed image deteriorates.

In general, (1) if the true specific gravity of the carrier is too large, when the developer is made to have a predetermined layer thickness on the sleeve by the developer layer thickness regulating member, or when the developer Since the load applied to the developer during stirring becomes large, (a) the above-described toner filming, (b) carrier destruction, and (c) deterioration of the toner are likely to occur in the long-term use of the developer. The deterioration of the agent and the accompanying deterioration of the image quality of the developed image tend to occur. Also, (2)
When the particle size of the carrier increases, the load on the developer increases as in (1) above.
(C) tends to occur, and as a result, the developer tends to deteriorate. It is also well known that (d) poor reproducibility of fine lines on a developed image, that is, poor developability.

Therefore, in a carrier in which the above (a) to (c) are likely to occur, it takes time and effort to replace the developer periodically and is uneconomical, so that the load on the developer is reduced. Alternatively, it is necessary to prevent the above (a) to (c) and extend the life of the developer by improving the impact resistance and spent resistance of the carrier.

In addition, it is necessary to address the problem of the developing property (d) by reducing the particle size of the carrier.

To solve the above-mentioned problems (a) to (d), a carrier having a small particle size in which magnetic particles are dispersed in a binder resin, for example, by a pulverization method disclosed in JP-A-54-66134. It is also possible to cope with this problem by using a magnetic material-dispersed small particle size carrier.

It is also possible to cope with this problem by using a magnetic material-dispersed small particle size carrier by a polymerization method disclosed in JP-A-61-9659.

However, when the magnetic substance-dispersed small particle size carrier does not contain a large amount of magnetic substance in the carrier particles, the saturation magnetization is small with respect to the particle diameter, and (e) the photoreceptor There is a problem that carrier adhesion occurs on the upper surface, and a mechanism for replenishing the developer or collecting the attached carrier must be provided in the image forming apparatus. Has the disadvantage that it cannot be done.

Further, in the above-mentioned magnetic substance-dispersed small particle size carrier, when the magnetic substance is contained in a large amount, the impact resistance becomes weak because the amount of the magnetic substance increases with respect to the binder resin. When the developer is made to have a predetermined layer thickness on the sleeve by the developer layer thickness regulating member, the magnetic substance is easily dropped from the carrier, and as a result, the developer is easily deteriorated. However, this method has a drawback that it cannot be a drastic measure for extending the life of the developer.

Further, in the above-mentioned magnetic substance dispersed small particle size carrier, when the magnetic substance is contained in a large amount, the specific resistance of the carrier decreases because the amount of the magnetic substance having a low specific resistance increases, and as a result, (F) There is also a disadvantage that image defects due to the leakage of the bias voltage applied during development are likely to occur.

Accordingly, even the above-mentioned magnetic substance-increasing magnetic substance-dispersed small particle size carrier has a drawback that it cannot be drastic as a measure for improving the developing property and extending the life of the developer. I have.

To cope with this, it is also possible to cope with the technique disclosed in Japanese Patent Application Laid-Open No. 58-21750, in which the carrier is coated with a resin. According to the carrier coated with the above resin, spent resistance, impact resistance,
The withstand voltage with respect to the applied voltage can be improved. In addition, since the charging characteristics of the toner can be controlled by the charging characteristics of the resin to be coated, a desired charge can be imparted to the toner by selecting the resin to be coated.

However, even in the above resin-coated carrier, when the amount of the coating resin is large and the specific resistance of the carrier is high, the charge amount of the toner in a low humidity environment increases.
So-called toner charge-up phenomenon easily occurs,
Further, when the amount of the coating resin is small, the specific resistance of the carrier becomes too low, so that there is a problem that it is difficult to control the coating amount such that an image defect is likely to occur due to leakage of the developing bias voltage.

Further, depending on the coating resin, even if the specific resistance of the carrier coated with the resin is considered to be an appropriate specific resistance in measurement, an image defect is likely to occur due to a leakage of a developing bias voltage, or in a low humidity environment. In some cases, the charge-up phenomenon easily occurs, and the carrier coated with the above resin also has a problem that it is difficult to control the carrier in consideration of developability.

[0020]

As described above, in consideration of the above-mentioned required characteristics of the carrier, the conventionally used carrier still has a problem to be improved, and further improvement is desired.

In particular, in a magnetic material-dispersed carrier in which magnetic particles are dispersed in a binder resin and the surface of which is coated with a resin, (1) Spent resistance (2) Impact resistance (prevention of carrier destruction) (3) Prevention of toner deterioration (4) Developability (5) Prevention of carrier adhesion on photoreceptor (6) Control of carrier resistance (7) Stabilization of toner chargeability Have been.

Accordingly, the main object of the present invention is to solve the above-mentioned problems of the magnetic material-dispersed carrier whose surface is coated with a resin, and as a result, it is not necessary to replenish the carrier during running. Another object of the present invention is to provide a magnetic material-dispersed carrier excellent in developability and developer life by stabilizing the chargeability of the toner during running and humidity fluctuation.

More specifically, in a magnetic material-dispersed carrier in which the surface of a core material containing magnetic particles and a binder resin as described above is coated with a resin, the carrier has an impact resistance, a resistance value, and a charge application to toner. An object of the present invention is to provide a magnetic material-dispersed carrier which is improved in stability by characteristics of a magnetic material used as a core material and characteristics of a resin to be coated, and is excellent in developability and developer life.

Another object of the present invention is to provide a method for manufacturing a magnetic material-dispersed carrier which can solve the above-mentioned problems.

Another object of the present invention is to provide an image forming method in which when a bias voltage is applied to a developing area to develop a latent image, current leakage or carrier adhesion to a photosensitive member is reduced.

[0026]

The present invention has a core material in which magnetic fine particles are dispersed in a binder resin,
And a magnetic material-dispersed carrier in which the surface of the core material is coated with an insulating resin, wherein the magnetic fine particles dispersed in the binder resin of the core material are treated with a titanium-based coupling agent. Is a magnetic substance dispersed type carrier.

The present invention is also a two-component developer for developing an electrostatic image, comprising the above-mentioned magnetic substance-dispersed carrier and toner.

Further, the present invention provides a method of coating a carrier coating solution containing a resin material on a core material obtained by dispersing magnetic fine particles in a binder resin, and drying and coating the core material surface with the resin. In the method for producing a body-dispersed carrier, the magnetic substance dispersed in the core material is treated with a titanium-based coupling agent.

Further, according to the present invention, a latent image formed on a photoreceptor is developed by applying a bias voltage in a development area by using a two-component developer for developing an electrostatic charge image having the above-mentioned magnetic substance-dispersed carrier and toner. Image forming method.

The present inventors have found that the use of the magnetic material-dispersed carrier having the above-described structure improves the impact resistance, the specific resistance, and the stability of charging the toner to the magnetic material-dispersed carrier. In addition, the inventors have found that the magnetic substance-dispersed carrier has excellent developability and developer life, thereby completing the present invention.

Although the details of the improvement of the characteristics of the carrier are not clear, treatment of the magnetic substance with a titanium-based coupling agent makes the carrier lipophilic and improves the dispersibility of the core material in the binder resin. It becomes a uniform dispersion state, and the impact resistance as a carrier increases. Furthermore, since the magnetic material subjected to this treatment has a higher surface resistivity than the untreated state, it is presumed that leakage hardly occurs even in a developing method in which a bias voltage is applied.

Further, in the magnetic substance-dispersed carrier of the present invention, since the wettability between the lipophilic magnetic substance and the coating resin is good, the surface of the core material can be uniformly coated with the resin, and the anti-magnetic property can be improved. It is presumed that the impact resistance, the resistance value, and the charging stability to the toner were further improved.

That is, if the carrier has poor wettability between the magnetic material forming the core material and the binder resin,
The dispersion state of the magnetic material becomes non-uniform, and pulverization via the aggregated magnetic material portion or pulverization from the interface between the magnetic material and the binder resin tends to occur, which tends to result in poor durability. Similarly, in the carrier, if the wettability between the magnetic material forming the core material and the coating resin is poor,
Uniform coatings tend to be difficult. In addition, if the coating on the core material is uneven, even if the surface resistance looks appropriate from a macro standpoint, if the carrier does not have micro-uniform resistance, charging in a low humidity environment It is considered that there arises a problem that up-developing easily occurs or an image defect easily occurs due to leakage of a developing bias voltage. Therefore, it is considered that these characteristics can be improved by adopting the above configuration in the present invention.

In the present invention, the general formula of a typical titanium-based coupling agent preferably used as a magnetic material treating agent is shown below.

General formula The amount of the titanium-based coupling agent to be applied to the magnetic material varies depending on the particle size, surface structure, and the like of the magnetic material.
0.5 to 10 parts, more preferably 0.5 to 100 parts
Preferably, up to 5 parts are used.

If the treatment amount of the titanium-based coupling agent is less than 0.5 part, there is no effect on the dispersibility of the magnetic substance,
On the other hand, if it exceeds 10 parts, a large amount of free coupling agent not binding to the magnetic substance is generated, which is not preferable.

The above-mentioned coupling agents may be used in combination of two or more as necessary.

In the magnetic material-dispersed carrier of the present invention,
As the coating resin of the carrier core material, a general insulating resin used for carrier coating can be used. For example, as the styrene resin, a resin polymerized from the following styrene monomer can be used.

That is, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-
Butylstyrene, pn-hexylstyrene, pn-
Octylstyrene, pn-nonylstyrene, pn-
Decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-chlorostyrene, 3,4-dichlorostyrene, m-nitrostyrene, o-nitrostyrene,
p-Nitrostyrene and the like.

The acrylic resin includes a resin polymerized from an acrylic monomer such as acrylic acid, acrylic ester, methacrylic acid, and methacrylic ester.

Examples of the acrylic monomer include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, acryl Stearyl acid, 2-chloroethyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-methacrylic acid-2- Examples include ethylhexyl, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate.

Further, a resin polymerized from ethylene, propylene, butylene, isobutylene or the like as a monoolefin monomer, or a vinyl monomer such as vinyl acetate, vinyl propionate, vinyl benzoate or vinyl butyrate as a vinyl monomer. Esters, vinyl ethers such as vinyl ethyl ether, vinyl methyl ether and vinyl butyl ether, or vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl butyl ketone, or maleic acid, fumaric acid, itaconic acid and citraconic acid , Mesaconic acid, glutaconic acid,
And unsaturated aliphatic dicarboxylic acids such as dihydromuconic acid.

As other resins, polyester, polyurethane, polyamide, silicone resin, epoxy resin, fluorine resin, phenol resin, melamine resin and the like can be used.

These resins may be used alone or as a monomer.
Those polymerized in combination of more than one kind or plural resins can be used in combination. Further, various crosslinking agents may be added as necessary.

In the present invention, the molecular weight and molecular weight distribution of the coating resin which can be used as the coating resin for the carrier core material, and the molecular weight of the fluorine-containing resin are determined by GPC (gel permeation chromatography). It refers to the value determined in light of a calibration curve obtained using polystyrene. The measurement conditions are shown below.

Apparatus: GPC-150C (Waters) Column: 7 columns of Shodex KF (Showa Denko) Temperature: 40 ° C. Solvent: THF (tetrahydrofuran) Flow rate: 1.0 ml / min Sample: 0. Injecting 0.4 ml of a 15% sample In the present invention, examples of the resin used as the binder resin constituting the carrier core material include all resins obtained by polymerizing vinyl monomers. Examples of the vinyl monomer here include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, and pn-butylstyrene. , P-tert-
Butylstyrene, pn-hexylstyrene, pn-
Octylstyrene, pn-nonylstyrene, pn-
Decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-chlorostyrene, 3,4-dichlorostyrene, m-nitrostyrene, o-nitrostyrene,
a styrene derivative such as p-nitrostyrene, ethylene,
Ethylene and unsaturated monoolefins such as propylene, butylene and isobutylene; unsaturated diolefins such as butadiene and isoprene; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide and vinyl fluoride; vinyl acetate and propion Vinyl esters such as vinyl acrylate and vinyl benzoate; methacrylic acid and methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, methacrylic acid- Α-methylene aliphatic monocarboxylic esters such as 2-ethylhexyl, stearyl methacrylate and phenyl methacrylate; acrylic acid and methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate Acrylic esters such as propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate and phenyl acrylate; maleic acid, maleic acid half ester; vinyl methyl Vinyl ethers such as ether, vinyl ethyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole,
N-vinyl compounds such as N-vinylpyrrolidone; vinylnaphthalenes; acrylonitrile, methacrylonitrile,
Acrylic acid or methacrylic acid derivatives such as acrylamide; acrolein; and the like, and those obtained by polymerizing one or two or more of these are used.

In addition to resins obtained by polymerization from vinyl monomers, non-vinyl condensation resins such as polyester resins, epoxy resins, phenol resins, urea resins, polyurethane resins, polyimide resins, cellulose resins, and polyether resins, and the like. And a mixture of the above-mentioned vinyl resin.

The magnetic material used for the magnetic fine particles constituting the carrier core material in the present invention includes, for example, ferromagnetic metals such as iron, cobalt and nickel, ferrite, and the like.
Examples include alloys or compounds containing elements exhibiting ferromagnetism such as iron, cobalt, and nickel such as magnetite and hematite. The saturation magnetization of the magnetic fine particles according to the present invention is 60 emu / g under a magnetic field of 10 K Oersted.
It is characterized by the above. If it is less than 60 emu / g, even if the content of the magnetic fine particles is increased,
Carrier adherence to the photoreceptor tended to occur. Therefore, it is essential that the above-mentioned saturation magnetization is 60 emu / g or more. The magnetic force was measured using a V
SM was used.

It is desirable that the magnetic fine particles have a primary average particle diameter of 2.0 μm or less. When it is larger than 2.0 μm, the surface of the core material is not dense, and uniform coating cannot be performed. Furthermore, the content of the magnetic fine particles according to the present invention with respect to the total amount of the carrier must be 30% by weight or more, preferably 50% by weight or more. If the content is less than 30% by weight, adhesion to the photoreceptor occurs, and it becomes difficult to control the resistance of the carrier.

Accordingly, one of the important characteristics of the magnetic material-dispersed carrier of the present invention is that it can be appropriately controlled not only in that it does not adhere to the photoreceptor but also in terms of controlling the charge amount of the toner. One. In particular, it is characterized in that the specific resistance of the carrier can be appropriately controlled so as not to cause the excessive charge application to the toner under low humidity, that is, to cause a so-called charge-up phenomenon. The particle diameter, specific resistance and content of the magnetic fine particles are essential.

The average particle size of the carrier particles of the present invention is 10 to 10.
Preferably, it is used in a range of 60 μm. When the carrier particle size is less than 10 μm, the carrier tends to easily adhere to the photoreceptor. When the carrier particle size is more than 60 μm, the share of the developer in the developing device becomes large, and the deterioration of the developer, particularly the toner particle There is a tendency that exfoliation and shape change of the external additive are easily caused. Furthermore, when the particle size is large, the surface area becomes small in terms of non-surface area, so that the amount of toner that can be held when constituting the developer decreases, resulting in an image lacking in definition. The particle diameter of the carrier used in the present invention is indicated by the maximum chord length in the horizontal direction, and the measuring method is randomly selected from 500 or more carriers by a microscope, and the diameter is measured to obtain the carrier particle diameter of the present invention. .

The true specific gravity of the carrier of the present invention is 1.5-5.
A range of 0 is preferred. More preferably, 1.5 to 4.5.
It is. If the true specific gravity exceeds 5.0, the load on the developer in the developing device increases, which is not preferable from the viewpoint of deterioration of the developer. If the true specific gravity is less than 1.5, it is practically impossible to obtain a magnetic force sufficient to suppress carrier adhesion to the photoconductor. The true specific gravity of the carrier used in the present invention was a Trudencer (manufactured by Seishin Enterprise).

The specific resistance of the carrier used in the present invention is 10 ⁷
A range of from 10 to 10 ¹⁴ Ω · cm is appropriate. 10 ⁷ Ω · cm
If the value is less than the above, current leaks from the sleeve to the surface of the photoreceptor in the developing region in the developing method in which a bias voltage is applied, so that a good image cannot be obtained. Also 10 ¹⁴ Ω
If it exceeds cm, a charge-up phenomenon is caused under conditions such as low humidity, which causes image deterioration such as density loss, transfer failure and fog.

In the present invention, the specific resistance was measured by the measuring method shown in FIG. That is, cell A
Is filled with a carrier, electrodes 1 and 2 are arranged so as to be in contact with the filled carrier, a voltage is applied between the electrodes, and a current flowing at that time is measured to obtain a specific resistance ρ (Ω · c
m) was used. In the above measuring method,
Since the carrier is a powder, a change in the filling rate occurs, and the specific resistance may change with the change. The conditions for measuring the specific resistance in the present invention were as follows: the contact area S between the charged carrier and the electrode was about 2.3 cm ² , the thickness was about 1 mm, the load on the upper electrode 2 was 275 g, and the applied voltage was 100 V.

In order to keep the specific resistance of the carrier of the present invention within the above range, the low specific resistance core material containing the magnetic fine particles is coated with the coating resin of the present invention so that the specific resistance can be easily reduced. Is a feature of the present invention. Further, it is a feature of the present invention that the specific resistance can be controlled by using the coating structure as a uniform coating. That is, the surface exposure state of the magnetic fine particles in the core material and the coating state of the coating resin are closely related to the characteristics of the carrier. If present, the image tends to be disturbed. Therefore, it is necessary to keep the resistance of each part of the carrier surface substantially uniform by uniform resin coating in order to obtain good developability, and this is also a feature of the present invention.

In the present invention, the sphericity of the carrier (long axis /
The short axis is desirably 2 or less. When the sphericity of the carrier in the present invention exceeds 2, the effect of reducing the share of the developer and the effect of improving the fluidity of the developer tend to decrease. Accordingly, the sphericity is desirably 2 or less in order to prevent the deterioration of the developer which can be achieved by the carrier in the present invention and the effect of improving the developing characteristics.

Means for achieving the above-mentioned sphericity of 2 or less in the carrier of the present invention include a method of heating the core material and thermally melting the surface to form a sphere, or a method of mechanically forming a sphere. Alternatively, the method of producing the core material is as follows: magnetic particles, a polymerization initiator, a suspension stabilizer, and the like are added to a monomer solution of a binder resin used in the core material, and then dispersed and granulated and polymerized. If the usual suspension polymerization method for obtaining the material is used, the sphericity of the carrier can be achieved 2 or less without performing the treatment on the core material.

Next, a method of manufacturing a carrier according to the present invention will be described.

The method of manufacturing a carrier according to the present invention comprises two steps of forming a core material and applying a resin coating.

The core material of the carrier of the present invention has a structure in which magnetic fine particles treated with a titanium-based coupling agent are uniformly dispersed in a resin. Use a pre-treated magnetic fine particle with a titanium-based coupling agent, or add a titanium-based coupling agent to the core resin binder resin during core material preparation, and And the like, while dispersing while causing a coupling reaction with the magnetic material.

As a method for producing the core material, the binder resin and the magnetic fine particles are mixed at a desired ratio, and for example, an appropriate heat-melting mixer such as a three-roll or extruder is used. Kneading at a temperature, cooling, and then pulverizing and classifying, or by dissolving the binder resin in a soluble solvent, mixing the magnetic fine particles into a slurry, and manufacturing using a spray drier. Granules, a method of drying, or adding magnetic fine particles, a polymerization initiator, a suspension stabilizer, etc. to a monomer solution of a binder resin for a core material,
There is a suspension polymerization method of granulating and polymerizing after dispersing. In particular, according to the polymerization method, it is not only easy to control the sphericity to 2 or less, but also to uniformly disperse the magnetic fine particles at each site on the surface of the core material, and Since it is possible to control at least a part of the core material to be substantially exposed to the surface of the core material, the method of producing the core material for obtaining the effects of the present invention is a more preferable method.

Next, as a method of coating the core material with a resin,
Considering that the core material is composed of a resin, a treatment method in which the coating resin is rapidly coated so that the core materials do not adhere to each other is desirable, and selection of a solvent that dissolves the coating resin and treatment temperature, time, etc. It is preferable to use a treatment method in which the coating and drying are simultaneously advanced in such a manner that the conditions are sufficiently controlled and the core material is constantly fluidized. In addition,
The amount of the coating resin varies depending on the true specific gravity of the core material. When the true specific gravity of the carrier is set to X, the optimum value of the amount of the coating resin needs to satisfy the following relational expression.

1 / 2X ≦ Coating resin amount ≦ 50 / X (% by weight) More preferably, 1 / X ≦ Coating resin amount ≦ 25 / X (% by weight).

That is, if the amount of the coating resin is less than 1 / 2X wt%, it is difficult to uniformly coat the surface of the core material because the amount of the coating resin is small. Does not hold. On the other hand, if it exceeds 50 / X% by weight, it is difficult to coat uniformly because the amount of the coating resin is too large, and a surplus coating resin tends to be present alone in the carrier. Therefore, not only is it impossible to control the resistance to the optimum value, which is a feature of the present invention, but also there is a tendency that the developing property is deteriorated due to the adhesion of the excess coating resin in the developer to the photoconductor.

The two-component developer for developing an electrostatic image of the present invention comprises 10 to 1000 parts by weight, preferably 30 to 50 parts by weight of the above-mentioned magnetic substance-dispersed carrier with respect to 10 parts by weight of the toner.
0 parts by weight are preferably mixed and used.

The toner according to the present invention has a weight average particle diameter of 1 to 20 μm, preferably 4 to 13 μm, and more preferably 4 to 10 μm.

The weight average particle size of the toner can be measured by various methods. In the present invention, the measurement was performed using a Coulter counter.

As a measuring device, Coulter Counter T
An interface (manufactured by Nikkaki) that outputs the number distribution and volume distribution using A-II type (manufactured by Coulter) and CX
-1 Connect a personal computer (Canon),
As the electrolytic solution, a 1% NaCl aqueous solution is prepared using primary sodium chloride. The measuring method is 100 to 100
To 150 ml, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant, and 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes using an ultrasonic disperser, and the particle size distribution of particles of 2 to 40 μm based on the number was measured using the Coulter Counter TAII, using an aperture of 100 μm. Was measured, and then a value according to the present invention was determined.

As the binder resin used in the toner according to the present invention, when a heating / pressing roller fixing device having an oil application device is used, the following binder resin for toner can be used.

For example, homopolymers of styrene and its substituted substances such as polystyrene, poly-p-chlorostyrene and polyvinyltoluene; styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-
Vinyl naphthalene copolymer, styrene-acrylic ester copolymer, styrene-methacrylic ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-
Styrene such as vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer Copolymers: polyvinyl chloride, phenolic resin, natural modified phenolic resin, natural resin modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane, polyamide resin, furan resin, epoxy resin , Xylene resin, polyvinyl butyral, terpene resin, cumarone indene resin, and petroleum resin.

In the heat and pressure roller fixing method in which almost no oil is applied, the offset phenomenon in which a part of the toner image on the toner image support member is transferred to the roller and the adhesion of the toner to the toner image support member are important. It is a problem.
These problems must be taken into account at the same time because toners that fix with less heat energy tend to block or cake during storage or in a developer. Therefore, in the present invention, when using the heating / pressing roller fixing method in which almost no oil is applied, the selection of the binder resin is more important. Preferred binder resins include crosslinked styrenic copolymers and crosslinked polyesters.

Examples of comonomers for the styrene monomer of the styrene copolymer include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, and the like.
Double bonds such as dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide Or a substituted product thereof; for example, a dicarboxylic acid having a double bond such as maleic acid, butyl maleate, methyl maleate, or dimethyl maleate and a substituted product thereof; for example, vinyl chloride, vinyl acetate, vinyl benzoate Vinyl esters such as ethylene, propylene and butylene; vinyl ketones such as vinyl methyl ketone and vinyl hexyl ketone; vinyl methyl ether and vinyl ethyl ether Ether, such as vinyl ethers vinyl isobutyl ether; such vinyl monomers are used alone or two or more.

As the crosslinking agent, a compound having two or more polymerizable double bonds is mainly used, for example, an aromatic divinyl compound such as divinylbenzene and divinylnaphthalene; for example, ethylene glycol diacrylate and ethylene glycol diacrylate. Methacrylate, 1,3
A double bond such as butanediol dimethacrylate
Carboxylic acid esters having one or more divinylaniline, divinyl ether, divinyl sulfide, divinyl sulfone divinyl compound; and compounds having three or more vinyl groups are used alone or as a mixture. The crosslinking agent is 0.01 to 10% by weight based on the binder resin.
It is preferable to use the binder resin (preferably 0.05 to 5% by weight) at the time of synthesizing the binder resin from the viewpoint of offset resistance and fixability.

When the pressure fixing method is used, a binder resin for a pressure fixing toner can be used. For example, polyethylene, polypropylene, polymethylene, polyurethane elastomer, ethylene-ethyl acrylate copolymer,
There are ethylene-vinyl acetate copolymer, ionomer resin, styrene-butadiene copolymer, styrene-isoprene copolymer, linear saturated polyester, and paraffin.

The toner according to the present invention has charge controllability added to toner particles (internal addition) or mixed with toner particles (external addition).
It is preferable to use them. The charge control agent makes it possible to control the optimal charge amount according to the development system. In particular, in the present invention, it is possible to further stabilize the balance between the particle size distribution and the charge, and by using the charge control agent It is possible to further clarify the function separation and the complementarity for higher image quality for each particle size range described above. As the positive charge control agent, a modified product of nigrosine and a fatty acid metal salt; tributylbenzylammonium-1-hydroxy-4-naphthosulfonate,
Quaternary ammonium salts such as tetrabutylammonium tetrafluoroborate; dibutyltin oxide; diorganotin oxides such as dioctyltin oxide and dicyclohexyltin oxide; dibutyltin borate, dioctyltin borate, and dicyclohexyltin borate alone or in combination of two or more be able to. Of these, charge control agents such as nigrosine and quaternary ammonium salts are particularly preferably used.

General formula

[0077]

Embedded image Or a copolymer with a polymerizable monomer such as styrene, acrylate or methacrylate as described above can be used as the positive charge control agent. In this case, these charge control agents also act as (all or part of) the binder resin.

As the negative charge controlling agent which can be used in the present invention, for example, an organometallic complex and a chelate compound are effective. Examples thereof include aluminum acetylacetonate, iron (II) acetylacetonate, and 3,5-acetylacetonate. Di-t
There is chromium tert-butylsalicylate. Particularly preferred are acetylacetone metal complexes (including monoalkyl-substituted and dialkyl-substituted products), salicylic acid-based metal complexes (including monoalkyl-substituted and dialkyl-substituted products) and salts, particularly salicylic acid-based metal complexes or salicylic acid-based metal salts. Is preferred.

The above-mentioned charge control agent (having no function as a binder resin) is preferably used in the form of fine particles. In this case, the number average particle size of the charge control agent is
Specifically, it is preferably 4 μm or less (more preferably 3 μm or less).

When internally added to the toner, such a charge control agent is preferably used in an amount of 0.1 to 20 parts by weight (more preferably 0.2 to 10 parts by weight) based on 100 parts by weight of the binder resin.

It is preferable to add fine silica powder to the toner according to the present invention. When the toner and the silica fine powder are combined, abrasion is remarkably reduced because the silica fine powder is interposed between the toner particles and the surface of the carrier or the sleeve. As a result, the life of the toner and the carrier and / or the sleeve can be prolonged, and a stable chargeability can be maintained. Thus, a two-component developer having more excellent toner and carrier can be used for a long time. It is possible.

In particular, in the case of a toner having a weight average particle size of 10 μm or less, the specific surface area is larger than that of a toner having a volume average particle size of more than 10 μm, and the toner particles and the carrier are brought into contact due to triboelectric charging. In this case, the number of times of contact between the toner particle surface and the carrier is increased as compared with a toner having a weight average particle diameter of more than 10 μm, so that abrasion of the toner particles and contamination of the carrier are liable to occur. By adding the powder, a good two-component developer can be obtained.

As the silica fine powder, any of fine silica powders manufactured by a dry method and a wet method can be used, but from the viewpoint of filming resistance and durability, it is preferable to use a fine silica powder obtained by a dry method.

The dry method referred to here is, for example, a method for producing fine silica powder produced by vapor phase oxidation of a silicon halide.

On the other hand, as a method for producing the silica fine powder used in the present invention by a wet method, various conventionally known methods can be applied.

The silica fine powder used herein may be a silicate such as anhydrous silicon dioxide (colloidal silica); aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, and zinc silicate.

Among the above-mentioned fine silica powders, those having a specific surface area of 30 m ² / g or more (particularly 50 to 400 m ² / g) measured by the BET method by nitrogen adsorption give good results. It is preferable to use 0.01 to 8 parts by weight, preferably 0.1 to 5 parts by weight of silica fine powder with respect to 100 parts by weight of the toner.

When the toner according to the present invention is used as a positively chargeable toner, the silica fine powder added to prevent wear of the toner and to prevent the carrier and the sleeve from being stained is more negatively charged than negatively charged. It is preferable to use positively-chargeable silica fine powder without impairing the charging stability, and when using as negatively-chargeable toner, it is preferable to use negatively-chargeable silica fine powder for the same reason.

Since the silica fine powder is generally negatively charged, a method for obtaining a positively charged silica fine powder is to use the untreated silica fine powder described above with at least one nitrogen atom in the side chain. There is a method of treating with a silicon oil having an organo group, a method of treating with a nitrogen-containing silane coupling agent, or a method of treating with both.

In the present invention, the positively-charged silica refers to a silica having a positive tribocharge with respect to the iron powder carrier when measured by a blow-off method.

As the silicon oil having a nitrogen atom in the side chain used for treating the silica fine powder, a silicon oil having at least a partial structure represented by the following formula can be used.

[0092]

Embedded image (Wherein, R ₁ represents hydrogen, an alkyl group, an aryl group or an alkoxy group, R ₂ represents an alkylene group or a phenylene group, R ₃ and R ₄ represents hydrogen, an alkyl group or an aryl group,, R ₅ Represents a nitrogen-containing heterocyclic ring.) In the above formula, the alkyl group, the aryl group, the alkylene group, and the phenylene group may have an organo group having a nitrogen atom, as long as the chargeability is not impaired. It may have a halogen substituent. The silicone oil is used in an amount of 1 to 50% by weight, preferably 5 to 30% by weight, based on the silica fine powder.

The nitrogen-containing silane coupling agent used in the present invention generally has a structure represented by the following formula.

Rm-Si-Yn (R represents an alkoxy group or a halogen, Y represents an amino group or an organo group having at least one nitrogen atom, m and n are integers of 1 to 3, and m + n =
4. Examples of the organo group having at least one nitrogen atom include an amino group having an organic group as a substituent, a nitrogen-containing heterocyclic group, or a group having a nitrogen-containing heterocyclic group. As the nitrogen-containing heterocyclic group, there is an unsaturated heterocyclic group or a saturated heterocyclic group, and known ones can be applied. Examples of the unsaturated heterocyclic group include the following.

[0095]

Embedded image

The following are examples of the saturated heterocyclic group.

[0097]

Embedded image

The heterocyclic group used in the present invention is preferably a 5- or 6-membered ring in consideration of stability.

Examples of such treating agents are aminopropyltrimethoxysilane, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane,
Diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane, monobutylaminopropyltrimethoxysilane, dioctylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane,
There are dibutylaminopropylmonomethoxysilane, dimethylaminophenyltriethoxysilane, trimethoxysilyl-γ-propylphenylamine, and trimethoxysilyl-γ-propylbenzylamine. Further, as the nitrogen-containing heterocycle, those having the above-mentioned structures can be used. Examples of such compounds include methoxysilyl-γ-propylpiperidine, trimethoxysilyl-γ-propylmorpholine, and trimethoxysilyl-γ-propylimidazole. There is. The silane coupling agent is used in an amount of 1 to 50% by weight, preferably 5 to 30% by weight, based on the silica fine powder.

The amount of the treated positive or negative silica fine powder is 0.01 to 100 parts by weight of the toner.
The effect is exhibited when the amount is from 8 to 8 parts by weight, and particularly preferably, the amount is from 0.
When added in an amount of 1 to 5 parts by weight, it exhibits positive or negative chargeability having excellent stability. In a preferred embodiment, the addition form is preferably such that 0.1 to 3 parts by weight of the treated silica fine powder is attached to the surface of the toner particles with respect to 100 parts by weight of the toner. The untreated fine silica powder described above can be used in the same application amount.

The silica fine powder used in the present invention may be treated with a silane coupling agent or a treating agent such as an organosilicon compound for the purpose of imparting hydrophobicity, if necessary. It is treated with a treating agent.
Examples of such a treating agent include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane,
Allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilyl acrylate, Vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane,
Hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and 2 to 12 siloxane units per molecule, one for each terminal unit There is a dimethylpolysiloxane containing a hydroxyl group bonded to Si. These are used alone or in a mixture of two or more. The treatment agent is 1 to 1 based on the silica fine powder.
It is preferred to use 40% by weight.

Instead of silica fine powder, BET critical area 5
Fine titanium oxide powder (TiO ₂ ) of 0 to 400 m ² / g may be used. Further, a mixed powder of silica fine powder and titanium oxide fine powder may be used.

It is also possible to add a fine powder of a fluorine-containing polymer (for example, a fine powder of polytetrafluoroethylene, polyvinylidene fluoride or a tetrafluoroethylene-vinylidene fluoride copolymer) to the toner according to the present invention. It is. In particular, polyvinylidene fluoride fine powder is preferred in terms of fluidity and abrasiveness. The amount added to the toner is 0.01 to 2.0 wt%, particularly 0.02%.
To 1.5 wt% (more preferably, 0.02 to 1.0 wt%).
wt%) is preferred.

As the coloring agent, conventionally known dyes and / or pigments can be used. For example, carbon black, phthalocyanine blue, peacock blue,
Permanent red, lake red, rhodamine lake, Hansa yellow, permanent yellow, benzidine yellow and the like can be used. The content is 0.1 to 20 parts by weight, preferably 0.5 to 20 parts by weight, based on 100 parts by weight of the binder resin.
It is preferably at most 2 parts by weight, more preferably from 0.5 to 9 parts by weight.
Good by weight.

The toner according to the present invention contains low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax,
It is also a preferred embodiment of the present invention to add a waxy substance such as carnauba wax, sasol wax and paraffin wax in an amount of 0.5 to 5% by weight.

The toner according to the present invention may further contain other additives as necessary.

To prepare the toner according to the present invention, a vinyl-based or non-vinyl-based thermoplastic resin, a pigment or dye as a colorant, a charge control agent, and other additives, if necessary, are mixed with a mixer such as a ball mill. After sufficiently mixing, the pigment or dye is melted, kneaded and kneaded using a heat kneader such as a heating roll, a kneader, or an extruder to disperse or dissolve the pigment or dye in the resin, and then cooled. After singulation, toner particles can be obtained by crushing and strict classification. The toner particles can be used as a toner as it is, but if necessary, an external additive such as silica fine powder is added to the obtained toner particles, and the toner particles and the external additive are added using a mixer such as a Henschel mixer. By mixing the above, a toner can be obtained.

Next, an image forming method according to the present invention will be described with reference to the developing device shown in FIG.

The latent image carrier 11 is made of an insulating drum for electrostatic recording or α-Se, CdS, ZnO ₂ , OPC, α-Si
And a photosensitive drum or a photosensitive belt having a photoconductive insulating material layer. The latent image carrier 11 is rotated in the direction of arrow a by a driving device (not shown). 22 is the latent image carrier 11
Is a developing sleeve as a developing carrier that is in close proximity to or is in contact with, and is made of, for example, a nonmagnetic material such as aluminum or SUS316. The developing sleeve 22 has a horizontally long opening formed in the longitudinal direction of the container on the lower left wall of the developing container 36, with a substantially right half circumferential surface protruding into the container 36, and a left substantially half circumferential surface being exposed outside the container to be rotatably supported. It is provided horizontally and is driven to rotate in the direction of arrow b.

Reference numeral 23 denotes a fixed permanent magnet (magnet) as a fixed magnetic field generating means inserted into the developing sleeve (developing carrier) 22 and positioned and held at the position and orientation shown in the figure.
Even when the developing sleeve 22 is driven to rotate, the magnet 23 is fixedly held at the position and posture shown in the drawing. This magnet 2
Numeral 3 has four magnetic poles: an N pole 23a, an S pole 23b, an N pole 23c, and an S pole 23d. Magnet 23
May be provided with an electromagnet instead of a permanent magnet.

Reference numeral 24 denotes a base fixed to the side wall of the container on the upper edge side of the developer supply opening on which the developing sleeve 22 is disposed. A non-magnetic blade as a developer regulating member disposed along the longitudinal direction, for example, a SUS 316 formed by bending a SUS 316 into a cross-shaped cross section.

Reference numeral 26 denotes a magnetic carrier limiting member whose upper surface is in contact with the lower surface of the non-magnetic blade 24 and whose front end surface is a developer guide surface 261. The portion constituted by the non-magnetic blade 24 and the magnetic carrier limiting member 26 is a regulating portion.

Reference numeral 27 denotes a carrier according to the present invention in which a resin coating layer is formed on a core material in which magnetic fine particles are dispersed in a binder resin. 37 is a non-magnetic toner. Reference numeral 40 denotes a sealing member that seals the toner accumulated in the lower portion of the developing container 36, has elasticity, is bent in the rotation direction of the sleeve 22, and elastically presses the surface side of the sleeve 22. The seal member 40 has an end on the downstream side in the sleeve rotation direction in a contact area with the sleeve so as to allow the developer to enter the inside of the container.

Reference numeral 30 denotes an anti-scattering electrode plate for applying a voltage having the same polarity as the developing agent to adhere the floating developer generated in the developing step to the photoreceptor side to prevent scattering.

Reference numeral 60 denotes a toner density detection sensor (not shown)
Is a toner supply roller that operates according to the output obtained from the toner supply roller. As the sensor, the developer volume detection method,
A piezoelectric element, an inductance change detection element, an antenna system using an alternating bias, and a system for detecting optical density can be used. The non-magnetic toner 37 is supplied by stopping the rotation of the roller. The fresh developer supplied with the toner 37 is mixed and stirred while being conveyed by the screw 61. Accordingly, a tribo is applied to the replenished toner during this conveyance. 63 is a cut-out plate which is cut out at both ends in the longitudinal direction of the developing device,
In this part, the fresh developer conveyed by the screw 61 is delivered to the screw 62.

The S magnetic pole 23d is a carrier pole. The collected developer after the development is collected in the container, and the developer in the container is further transported to the regulating section.

In the vicinity of 23d, the fresh developer conveyed by the screw 62 provided near the sleeve and the recovered developer after development are exchanged.

Reference numeral 64 denotes a conveying screw for making the amount of developer in the axial direction of the developing sleeve uniform.

The distance d between the end of the non-magnetic blade 24 and the surface of the developing sleeve 22 is 100 to 900 μm, preferably 1 to 900 μm.
It is 50 to 800 μm. If the distance is less than 100 μm, magnetic particles described later are clogged in the meantime, and the developer layer is likely to cause unevenness, and the developer necessary for good development cannot be applied, and the density of the developed image is low and uneven. There is a disadvantage that can only be obtained. d is preferably 400 μm or more in order to prevent non-uniform coating (so-called blade jam) due to unnecessary particles mixed in the developer. 9
If the thickness is larger than 00 μm, the amount of the developer applied on the developing sleeve 22 increases, so that the predetermined developer layer thickness cannot be regulated, the magnetic particles adhere to the latent image carrier increases, and the There is a disadvantage in that the regulation of development by the developer limiting member 26 is weakened, and toner tribo is insufficient and fogging is likely to occur.

[0120] The imaginary line connecting the center and the magnetic pole 23a of the developing sleeve 22 and L _1, the imaginary line connecting the tips of the non-magnetic blade 24 of the center and the developer regulating member of the developing sleeve 22 is taken as L _2, the angle made a virtual line by L ₁ and L ₂ and theta _1.

This angle θ ₁ is -5 ° to 35 °, preferably 0 ° to 25 °. When θ ₁ <−5 °, the developer thin layer formed by the magnetic force, mirror force, cohesion, etc. acting on the developer becomes sparse and uneven, and when θ ₁ > 35 °, non-magnetic With a blade, the amount of developer applied increases, and it is difficult to obtain a predetermined amount of developer.

In the magnetic particle layer, the sleeve 22 has an arrow b
Even when the sleeve 22 is driven to rotate in the direction, the movement becomes slower as the distance from the sleeve surface increases due to the balance between the magnetic force and the binding force based on gravity and the conveying force in the moving direction of the sleeve 22. Of course, some fall under the influence of gravity.

Therefore, by appropriately selecting the arrangement positions of the magnetic poles 23a and 23d and the fluidity and magnetic characteristics of the magnetic carrier 27, the magnetic particle layer is conveyed toward the magnetic pole 23a closer to the sleeve to form a moving layer. Due to the movement of the magnetic carrier, the magnetic carrier is conveyed to the developing area with the rotation of the sleeve and used for development.

At this time, it is preferable to make the thickness of the developer layer on the developing sleeve 22 equal to or slightly larger than the gap distance e between the developing sleeve 22 and the latent image carrier 11, and to apply an alternating electric field to this gap. . This distance e is 50 to 8
00 μm (more preferably, 100 to 700 μm) is good.

By applying a developing bias in which an alternating electric field or a DC electric field is superimposed on the alternating electric field between the developer sleeve 22 and the latent image carrier 11 by a bias power supply, the toner from the developer sleeve 22 to the latent image holding member 11 is applied. Can be easily moved, and a high-quality image can be formed.

The AC electric field as the alternating electric field to be applied is preferably 2000 Vpp or less, and when a DC electric field is superimposed, it is preferable to apply the DC electric field in a range of 1000 V or less.

[0127]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. This does not limit the invention in any way. Incidentally, all percentages and parts in the following formulations indicate% by weight and parts by weight,
Mw indicates a weight average molecular weight, and Mn indicates a number average molecular weight. Table 1 shows the physical properties of the carriers used in the following examples and comparative examples of the present invention, and Table 2 shows the evaluation results.

Example 1 5 parts of a titanium coupling agent (isopropyltricumylphenyl titanate) was added to 500 parts of toluene, and the mixture was thoroughly stirred. Next, 500 parts of magnetite (average particle size 0.24 μm) is added, mixed with a mixer, and then vacuum dried to remove the solvent. Using the treated magnetite thus obtained, a core material was produced as follows.

Styrene 19.4% Methyl methacrylate 15.2% Treated magnetite (particle size 0.24 μm) 65.4% The above materials were heated to a temperature of 70 ° C. in a container and dissolved to form a monomer mixture. . Further, while maintaining the temperature at 70 ° C., the initiators 2,2′-azobis- (2,4-dimethylvaleronitrile) and 2,2′-azobisisobutyronitrile were added and dissolved, and the monomer composition was dissolved. Prepared. This is 1% PVA
The solution was charged into a 2 liter flask containing 1.2 liter of the aqueous solution, and heated at 70 ° C. with a homogenizer at 4800 rpm for 1 hour.
After stirring for 0 minutes, the composition was granulated. Thereafter, polymerization was performed at 70 ° C. for 10 hours while stirring with a paddle stirrer. After the completion of the polymerization reaction, the reaction product was cooled, and the obtained magnetic material-dispersed styrene acrylic slurry was washed and filtered. This was dried to obtain magnetic material-dispersed resin particles. The true specific gravity of the obtained magnetic material-dispersed resin particles, that is, the core material, was 2.1.

A styrene-2-ethylhexyl acrylate copolymer resin (Mn / Mw = 2) was formed on the surface of the obtained core material.
0.2, Mw = 110,000) was dissolved in toluene so that the amount of the coating resin was 1.5% from the above formula, to prepare a carrier coating solution. The carrier coating solution was applied by a coating machine (Spira Coater, manufactured by Okada Seiko Co., Ltd.)
It was applied to the core material while drying while applying. The obtained magnetic material-dispersed resin carrier after coating is heated at 70 ° C. for 1 hour.
After drying for a time to remove the solvent, the mixture was heated at a temperature of 110 ° C. for 2 hours to obtain a resin-coated magnetic substance-dispersed resin carrier in which the core material surface was coated with a resin coating layer. When the obtained resin-coated magnetic substance dispersed resin carrier was observed by an electron microscope, the core material was uniformly coated with the resin, and the magnetic particles were substantially uniformly exposed on the coated surface. It was confirmed that.

Table 1 summarizes the obtained physical properties of the carrier.

On the other hand, a polyester resin obtained by condensing 100 parts of propoxylated bisphenol and fumaric acid 5 parts of a phthalocyanine pigment 5 parts of a chromium complex of di-tert-butylsalicylic acid 4 parts The mixture was melt-kneaded three times with a three-roll mill, cooled, and coarsely ground to a particle size of about 1 to 2 mm using a hammer mill.
Next, it was pulverized by a pulverizer using an air jet method. Further, the obtained finely pulverized product was classified to have a weight average diameter of 1%.
2.3 μm negatively chargeable cyan powder (toner)
I got

100 parts of the above cyan toner and 0.4 parts of fine silica powder hydrophobized with hexamethyldisilazane were mixed with a Henschel mixer to prepare a cyan toner having fine silica powder on the surface of toner particles.

The cyan toner and the resin carrier were mixed in a temperature / humidity environment of N / N (23 ° C./60% RH) so that the toner concentration became 10% to obtain a developer. 100 g of the obtained developer was put in a 250 cc plastic bottle, and shaken with a Turbula mixer for 1 hour. Thereafter, the developer was taken out, and the developer was observed with an electron microscope. As a result, no detachment of the magnetic material from the carrier, no peeling of the coating material, and no filming by the toner were observed. Also, no detachment or burial of the external additive of the toner was observed.

A developer was obtained by mixing the cyan toner and the above-mentioned resin carrier in a temperature / humidity environment of L / L (15 ° C./10% RH) so that the toner concentration became 8%. Under the same environment, the full color laser copier CLC-
1 and put in an external motor drive (peripheral speed 300
(rpm) for 30 minutes. After this, CLC
Using -1, an image was displayed at a development contrast of 300 V. As a result, the density of the solid image was sufficient, and the reproducibility of the halftone portion was also good.

(Comparative Example 1) A core material was prepared in the same manner as in Example 1 except that an untreated magnetite was used.
The same resin coating as in Example 1 was applied to obtain a carrier. When the surface of the obtained carrier was observed with an electron microscope, unevenness in resin coating was observed. A test similar to that of Example 1 was performed using this carrier.

As a result of the shaking test, the coating resin of the carrier was partially peeled off, and in the image forming test, roughness was observed in the halftone portion.

Comparative Example 2 The same test as in Example 1 was performed, except that the core material used in Example 1 was not coated with a resin but was used as a carrier.

As a result of the shaking test, toner spent was partially observed on the carrier surface. Further, as a result of the image display test, carrier adhesion was observed in the non-image area.

Comparative Example 3 Using 45 μm reduced iron particles instead of the core material used in Example 1, the coating resin amount used in Example 1 was 1.2% in the same manner as in Example 1. And a carrier having a true specific gravity of 7.8 was obtained. The same measurement and test as in Example 1 were performed using this carrier.

As a result of the shaking test, the carrier did not change from that before shaking, but the external additive was buried on the toner surface. In addition, as a result of the image output test, in particular, rattling of the halftone portion was observed.

(Example 2) Styrene-2-ethylhexyl acrylate copolymer 50% (weight ratio of monomer composition = 85: 15) Magnetite treated with a titanium coupling agent 50% (same as used in Example 1) The above materials were sufficiently premixed with a Henschel mixer, melt-kneaded at least twice with a three-roll mill, cooled, and coarsely ground to a particle size of about 2 mm using a hammer mill. Next, it was pulverized with an air jet pulverizer to a particle size of 50 μm. Further, the obtained finely pulverized product was put into a Mechanomill MM-10 (manufactured by Okada Seiko Co., Ltd.) and mechanically sphericalized.

The finely pulverized particles having undergone spheroidization were further classified to obtain a core material. The particle size of the obtained core material was 48 μm.

A covering layer was provided in the same manner as in Example 1 except that a polyester resin was used on the surface of the obtained core material to obtain a resin-coated carrier. The same test as in Example 1 was performed using this carrier.

As a result, a shaking test was performed in the same manner as in Example 1.
It was good in the image output test.

Example 3 7 parts of a titanium coupling agent (isopropyl distearoyl titanate) was added to toluene 1
Add to 00 parts and stir well. Next, 500 parts of magnetite (average particle size: 0.27 μm) is added, mixed with a mixer, and the solvent is removed by vacuum drying. Using the magnetite thus obtained, a core material was produced as follows.

Polyester resin obtained by condensing 40% of ethoxylated bisphenol-fumaric acid-trimellitic acid (weight ratio of monomer composition = 50: 40: 10) Treated magnetite (average particle size 0.27 μm) 60% In the same manner as in Example 2, a spherical core material was obtained. The particle size of the particles was 54 μm.

Using a carrier coating solution in which 10% of a silicone resin (SR-2400 manufactured by Toray Silicone Co., Ltd.) was dissolved in toluene to a coating resin amount of 2.0% on the surface of the obtained core material, an example was used. The resin fine particles were coated in the same manner as in Example 1 to obtain a magnetic material-dispersed resin carrier. When a test similar to that of the first embodiment was performed,
Similar good results were obtained.

(Example 4) Phenol 10.0% Formaldehyde 5.0% (Formaldehyde about 37%, Methanol about 10%, balance water) Treated magnetite (particle diameter 0.27 μm) 85.0% (Example 3) Using ammonia as a basic catalyst and calcium fluoride as a polymerization stabilizer, the above materials were gradually heated to a temperature of 80 ° C. while stirring in an aqueous phase, and polymerized for 2 hours. Was done. The particle size of the obtained core material was 42 μm. The resin particles were coated with the coating resin used in Example 3 with a coating resin amount of 1.7.
%, And coating was performed in the same manner as in Example 3 using a toluene solution in which 10% was dissolved. When a test similar to that in Example 1 was performed using this carrier, good results similar to those in Example 1 were obtained.

(Embodiment 5) The carrier used in Embodiment 4
The same carrier was used.

Further, as the toner, styrene-2-ethylhexyl acrylate-100 parts dimethylaminoethyl methacrylate copolymer (monomer composition weight ratio = 80: 15: 5) copper phthalocyanine 4 parts low molecular weight polypropylene 5 parts The weight average diameter was 12.4 μ in the same manner as in Example 1.
m cyan particles were obtained. 0.8 parts of positively chargeable colloidal silica treated with an amino-modified silicone oil was mixed with 100 parts of the cyan particles using a Henschel mixer to obtain a positively chargeable cyan toner.

A developer was prepared by mixing the above-mentioned cyan toner and carrier so that the toner concentration became 8%, and a test was performed in the same manner as in Example 1 using a Canon copier NP4835. In the above, a uniform image was obtained with excellent positive chargeability.

[0153]

[Table 1]

[0154]

[Table 2]

[0155]

As described above, when the magnetic carrier coated with the coating resin used in the present invention is used, (1) Spent resistance (2) Impact resistance (prevention of carrier destruction) (3) Deterioration of toner Prevention (4) Developability (5) Prevention of Carrier Adhesion on Photoconductor (6) Control of Carrier Resistance (7) Stable Charging of Toner Can Be Satisfactorily Satisfied and Produce High Quality Images for And can be provided stably.

[Brief description of the drawings]

FIG. 1 is a schematic diagram schematically showing an electric resistance measuring device.

FIG. 2 is an explanatory diagram illustrating an example of a developing device used in the image forming method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lower electrode 2 Upper electrode 3 Insulator 4 Ammeter 5 Voltmeter 6 Constant voltage device 7 Carrier 8 Guide ring 11 Latent image carrier 22 Development carrier (development sleeve) 23 Permanent magnet 24 Developer regulating member (non-magnetic blade) 26 magnetic carrier limiting member 27 magnetic carrier 30 scattering prevention electrode plate 36 developing container 37 toner 40 seal member 60 toner supply roller 61 screw 62 screw 63 stripping plate 64 transport screw

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-62-70864 (JP, A) JP-A-63-50868 (JP, A) JP-A-64-29857 (JP, A) JP-A-2- 158751 (JP, A) JP-A-3-146965 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 9/107 G03G 9/113

Claims (9)

(57) [Claims] 1. A magnetic material-dispersed carrier having a core material in which magnetic fine particles are dispersed in a binder resin, and the surface of the core material is coated with an insulating resin. A magnetic material-dispersed carrier, wherein the magnetic fine particles dispersed in the resin are treated with a titanium-based coupling agent. 2. The magnetic material-dispersed carrier according to claim 1, wherein the true specific gravity of the carrier is 1.5 to 5.0. 3. The magnetic material-dispersed carrier according to claim 1, wherein the magnetic force of the magnetic material dispersed in the core material is 60 emu / g or more under a magnetic field of 10 K Oersted. . 4. The magnetic material-dispersed carrier according to claim 1, wherein the carrier has a particle size of 10 μm to 60 μm. 5. A carrier having a specific resistance of 10 ⁷ Ω · cm to 1
The magnetic material-dispersed carrier according to any one of claims 1 to 4, wherein the carrier is 0 ¹⁴ Ω · cm. 6. The magnetic material-dispersed carrier according to claim 1, wherein a core material obtained by dispersing magnetic fine particles in a binder resin is produced by a polymerization method. 7. An electrostatic charge comprising: a magnetic material-dispersed carrier having a core material obtained by dispersing magnetic fine particles in a binder resin, and a surface of the core material coated with an insulating resin; and a toner. A two-component developer for electrostatic image development, wherein a magnetic substance dispersed in the core material is treated with a titanium-based coupling agent. 8. A magnetic material dispersion in which a carrier coating solution containing an insulating resin material is applied to a core material obtained by dispersing magnetic fine particles in a binder resin and dried, and the core material surface is coated with the insulating resin. A method of manufacturing a magnetic carrier, wherein the magnetic material dispersed in the core material is treated with a titanium-based coupling agent. 9. A two-component for electrostatic charge image development comprising a magnetic material-dispersed carrier having a core material obtained by dispersing magnetic fine particles in a binder resin and having the surface of the core material coated with a resin, and a toner. In an image forming method for developing a latent image formed on a photoreceptor by applying a bias voltage in a development area with a system developer, a magnetic material dispersed in the core material is treated with a titanium coupling agent. An image forming method comprising: