JPH05107809A - Electrophotographic developer - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] Impact resistance, resistance value of magnetic substance dispersion type carrier,
Provided is an electrophotographic developer which is excellent in developability and developer life even in a system using a toner having a small particle size, in which stability of imparting charge to toner is improved by characteristics of a resin to be coated, and developer deterioration easily occurs. .. [Structure] The toner has a specified particle size distribution, and in particular,
A toner particle group having a particle size of 4 μm or less has the following formula N / V = −0.32N + k N: number% of toner particles having a particle size of 4 μm or less, provided that a positive number V of 15 to 60 V: a toner particle having a particle size of 4 μm or less Volume% k: A positive number of 13 to 20 is satisfied, and the carrier has a core material in which a magnetic material is dispersed in a binder resin, and the resin coating the surface of the core material has a hydroxyl value of 1 to 100. A magnetic substance-dispersed carrier obtained by coating with a vinyl-based copolymer having: and a fluororesin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic developer used for developing an electrostatic latent image or a magnetic latent image formed in an electrophotographic method, an electrostatic recording method or an electrostatic printing method.

[0002]

2. Description of the Related Art Generally, in an electrostatic recording apparatus using electrophotography, selenium, OPC (organic photoconductor), α-S
A photoconductive substance such as i is used as a photoconductor, the photoconductor is uniformly charged by various means, and then a photoimage is irradiated on the photoconductor surface to form an electrical latent image corresponding to the photoimage. A method in which a latent image is formed on the surface of a photoconductor and toner is attached to the latent image by a magnetic brush development method or the like to visualize the latent image is generally adopted.

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

The developer having the above toner and carrier is
A developing layer containing a magnet is coated with a predetermined layer thickness by a developer layer thickness regulating member, and is conveyed to a developing area formed between the photoconductor and the developing sleeve by utilizing a magnetic force. It

A certain developing bias voltage is applied between the photoconductor and the developing sleeve, and the toner is developed on the photoconductor in the developing area.

In recent years, in order to obtain a high quality image, the toner particle size has been reduced. On the other hand, however, when the developer is used for a long period of time and the load on the carrier is large, when the toner having a small particle size is used, the durability of the developer is likely to deteriorate, and the image quality is likely to deteriorate accordingly. Therefore, when a developer using a toner having a small particle size is used for a long period of time, suitable properties for the carrier in order to maintain a high quality image are appropriate charging property, pressure resistance against an applied electric field, and impact resistance. Properties, spent resistance, abrasion resistance, developability, productivity and the like, but it is particularly important to reduce the load on the developer.

Generally, (1) if the true specific gravity of the carrier is too large, the developer is developed when the developer has a predetermined layer thickness on the sleeve by the developer layer thickness regulating member, and by stirring in the developing machine. Since the load on the developer increases, (a) the toner filming (b) carrier destruction (c) toner deterioration easily occurs during long-term use of the developer, and as a result, the developer deterioration and As a result, the image quality of the developed image tends to deteriorate. (2) As the particle size of the carrier increases, the load on the developer also increases as in the case of (1) above.
To (c) are likely to occur, and as a result, the developer is likely to deteriorate. It is also well known that (d) the fine line reproducibility of a developed image is poor, that is, the developability is poor.

[0008] Therefore, in the carrier in which the above (a) to (c) are likely to occur, it is necessary to periodically replace the developer and it is uneconomical, so that the load on the developer is reduced. Alternatively, it is necessary to improve the impact resistance and the spent resistance of the carrier to prevent the above (a) to (c) and prolong the life of the developer.

Further, it is necessary to deal with the problem of developability (d) by reducing the particle size of the carrier.

To solve the above 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 pulverizing method disclosed in Japanese Patent Laid-Open No. 54-66134. It is also possible to deal with the magnetic substance dispersion type small particle size carrier.

Further, it is also possible to deal with it by a magnetic substance dispersion type small particle size carrier prepared by a polymerization method, which is disclosed in JP-A-61-9659.

However, the magnetic substance-dispersed small particle size carrier has a small saturation magnetization with respect to the particle size when a large amount of the magnetic substance is not contained in the carrier particles, and (e) the photoconductor during development. There is a problem that the carrier adheres to the upper part, and it is necessary to replenish the developer or have a mechanism for collecting the adhered carrier in the image forming apparatus, which is a drastic measure for extending the life of the developer. It has the drawback that it cannot be.

When a large amount of the magnetic material is contained in the magnetic material-dispersed small particle size carrier, the amount of the magnetic material with respect to the binder resin increases, so that the impact resistance becomes weak. When the developer has a predetermined layer thickness on the sleeve with the developer layer thickness regulating member, or due to agitation in the developing device or the like, the magnetic substance is apt to be missing from the carrier, resulting in the developer. However, even in this case, there is a drawback in that it cannot be a drastic measure for extending the life of the developer.

When a large amount of the magnetic material is contained in the magnetic material-dispersed small particle size carrier, the resistance of the carrier is lowered because the amount of the magnetic material having a low resistance is increased. f) It also has a drawback that image defects are likely to occur due to leakage of bias voltage applied during development.

Therefore, even in the above-mentioned magnetic substance-dispersed small particle size carrier with increased amount of magnetic material, it is not fundamental to improve the developing property and to extend the life of the developer when the small particle size toner is used. It has the drawback that it cannot be.

On the other hand, it is possible to deal with this by the technique of coating the carrier with a resin, which is disclosed in Japanese Patent Laid-Open No. 58-21750. According to the carrier coated with the above resin, it is possible to improve the spent resistance, impact resistance, and pressure resistance against an applied voltage.
Further, since it is possible to control the charging characteristic of the toner by the charging characteristic of the resin to be coated, it is possible to impart a desired charging charge to the toner by selecting the resin to be coated.

However, also in the above resin-coated carrier, it is difficult to control the amount of the coating resin, and when the amount of the coating resin is large and the resistance of the carrier is high, the charge amount of the toner increases in a low humidity environment. The charge-up phenomenon is likely to occur, and when the amount of the coating resin is small, the resistance of the carrier becomes too low, so that the image defect due to the leak of the developing bias voltage is likely to occur.

Depending on the coating resin, even if the resistance of the carrier coated with the resin is considered to be an appropriate resistance for measurement, image defects are likely to occur due to leakage of the developing bias voltage, or charging in a low humidity environment may occur. There are some cases where the up phenomenon occurs easily, and the coated carrier with the above resin also
Considering the developability, there is a problem that its control is difficult. In particular, when the toner has a smaller particle size, the variation in the charge of each toner becomes large, and it becomes more difficult to control the developing property.

[0019]

As described above, in consideration of the excellent durability and developability required for the developer, the conventionally used carrier still has a problem to be improved and is sufficiently satisfactory. Nothing is known so far.

In particular, in a magnetic substance dispersion type carrier in which magnetic particles are dispersed in a binder resin and the surface is covered 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 the photoconductor (6) Control of carrier resistance (7) Stabilization of toner chargeability can be sufficiently satisfied, and further, Nothing has been known so far that can reduce the deterioration of the developer when a small particle diameter toner having a large specific surface area is used.

Therefore, the main object of the present invention is to solve the above-mentioned problems of the magnetic substance-dispersed carrier whose surface is coated with a resin, and as a result, it is unnecessary to replenish the carrier during running. In addition, by using a small particle size toner that stabilizes the chargeability of the toner during running and humidity fluctuation, and that also has excellent gradation and resolution of the image, it is possible to improve the developability and the life of the developer. To provide the developer. More specifically, in the magnetic material dispersion type carrier in which the surface of the core material containing the magnetic particles and the binder resin as described above is coated with the resin, the impact resistance of the carrier, the resistance value, the stability of imparting charge to the toner, It is an object of the present invention to provide a novel developer which is improved according to the characteristics of the resin to be coated and is excellent in developability and developer life even in a system using a toner having a small particle size, which easily causes deterioration of the developer.

[0022]

Means and Actions for Solving the Problems The present inventors have
As a result of intensive studies and studies to improve various defects of the magnetic substance-dispersed carrier whose surface is coated with a resin and to obtain a developer excellent in developability and durability, (1) toner particle size distribution However, for a particle size of 4 μm or less, 15 to 60
% By number, 10-60% by number for a particle size of 4-8 μm, 2.0% by volume or less for a particle size of 16.0 μm or more, and the volume average particle size of the toner is 4-
A toner particle group having a size of 10 μm and a particle size of 4 μm or less is represented by the following formula: N / V = −0.32N + k N: number% of toner particles having a particle size of 4 μm or less, provided that a positive number of 15 to 60 V: particle size of 4 μm or less % Of the toner particles having k: 13 to 20 and a carrier having a core material in which a magnetic material is dispersed in a binder resin, and the surface of the core material is coated with a resin. Which is a magnetic substance-dispersed carrier, wherein the resin coating the surface of the core material is a vinyl-based copolymer having a hydroxyl value of 1 to 100 and a fluorine-containing resin (hereinafter, this developer is referred to as "developer A.) or (2) the particle size distribution of the toner is 13 to 60% by number for particle sizes of 4 μm or less, 10 to 70% by number for particle sizes of 4 to 8 μm, and 16. 2.0 volume for particle size of 0 μm % And the volume average particle diameter of the toner is 4 to 10 μm, and the toner particle group of 4 μm or less has the following formula N / V = −0.32N + k N: %, Positive number of 13 to 60 V: volume% of toner particles having a particle size of 4 μm or less k: positive number of 13 to 20 and the carrier disperses a magnetic material in a binder resin. A magnetic material-dispersed carrier having a core material formed by coating the surface of the core material with a resin, wherein the resin coating the surface of the core material is composed of a styrene-acrylic copolymer and a fluorine-containing resin. And, the monomer ratio of the acrylic component in the styrene-acrylic copolymer is 30 to 90% by weight, and the weight average molecular weight has a distribution of about 30,000 to 70,000 and the weight average. Molecular weight / The number average molecular weight is 2.0 to 10, and the mixing ratio of the fluororesin to the styrene-acrylic copolymer is 5 by weight ratio (the weight of the fluororesin: the weight of the copolymer). : 95 to 95: 5 (hereinafter, this developer will be referred to as “developer B”), the spent resistance, impact resistance, resistance value and toner of the magnetic substance-dispersed carrier can be improved. The present invention has been completed by finding that the stability of imparting charge to the toner becomes good, and that the developer using the magnetic substance-dispersed carrier and the toner having a small particle diameter has excellent developability and developer life.

Although details of the improvement of various properties of the carrier are not clear, the surface observation of the carrier by a scanning electron microscope reveals that the vinyl-based copolymer and the fluorine-containing resin used in the present invention are the same as those of the carrier. It was observed that the surface of the core material was uniformly coated.

Therefore, it is considered that the uniform coating property is the reason why the magnetic material-dispersed carrier used in the present invention has good impact resistance, resistance value, and stability of imparting charge to toner. That is, when the surface of the carrier is divided into minute parts, and when the coating is uniform, the impact resistance, the resistance value, and the charge imparting property to the toner show the same characteristics in every part. Conceivable.

On the other hand, when the coating is non-uniform,
It is considered that the impact resistance, the resistance value, and the charge imparting property to the toner are different in each part of the carrier surface. Therefore, for example, the measurement of the resistance value is an evaluation method when the carrier is viewed from a macro standpoint. Therefore, even if the resistance value is considered to be an appropriate resistance in the measurement, if the coating is non-uniform, low humidity is used. It is considered that there is a problem that a charge-up phenomenon is likely to occur in an environment, or an image defect is likely to occur due to leakage of a developing bias voltage.

Further, it is considered that by limiting the amount of fine powder of 4 μm or less when the toner has a small particle size, variations in each toner can be suppressed, and the developer deterioration prevention and the developability according to the present invention can be satisfied. That is, if there is a variation in the charge of each toner, a difference occurs in the adhesive force between the toner and the carrier,
It is considered that the particles having strong adhesive force have a larger share due to the carrier, the developing device, etc., and thus cause the toner filming.

Next, the structure of the present invention will be described in detail.

The vinyl resin containing a hydroxyl group used as the coating resin for the carrier of the developer A of the present invention is a copolymer of a vinyl monomer having a hydroxyl group and another vinyl monomer. As the vinyl monomer having a hydroxyl group, 2-hydroxyethyl acrylate,
2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 2-hydroxy-3-phenyloxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 2 methacrylate -Hydroxy-3-phenyloxypropyl and the like. These monomers have a copolymer hydroxyl value of 1 to 100 (K
OHmg / g), more preferably 5 to 70, still more preferably 10 to 50 (KOHmg / g).

When this value is small, the effect of exposing the fluorine-containing resin to the carrier surface, which is a feature of the coating resin of the present invention, is insufficient, and the charge imparting ability of the carrier is lowered.
On the other hand, when the hydroxyl value is more than 100, the hygroscopicity is increased and the charging stability under high temperature and high humidity is lost.

Other vinyl monomers to be copolymerized with these hydroxyl group-containing vinyl monomers include styrene, α-methylstyrene, p-methylstyrene and p-methylstyrene.
Styrene derivatives such as -t-butylstyrene and p-chlorostyrene; methyl methacrylate, ethyl methacrylate,
Propyl methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, nonyl methacrylate,
Decyl methacrylate, undecyl methacrylate, dodecyl methacrylate, glycidyl methacrylate, methoxyethyl methacrylate, propoxyethyl methacrylate, butoxyethyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate Butyl acrylate,
Examples thereof include pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, and vinyl monomers.

Among these other vinyl monomers, the vinyl monomer having one vinyl group in one molecule is preferably styrene, styrene derivative, methacrylic acid ester, acrylic acid ester, etc., and particularly preferably 1 to 5 for the alkyl group.
Alkyl esters of methacrylic acid or acrylic acid having 4 carbon atoms are preferred.

Of these vinyl monomers, the vinyl monomer having a hydroxyl group is used so that the copolymer has a hydroxyl value of 1 to 100 (KOHmg / g). These vinyl monomers are copolymerized by methods such as suspension polymerization method, emulsion polymerization method and solution polymerization method. These copolymers have a weight average molecular weight of 10,000 to 70,
Those of 000 are preferred. Weight average molecular weight is 10,
If it is less than 000, the impact resistance tends to be insufficient, and 70,
If it exceeds 000, it becomes difficult to coat the carrier core material, and aggregates are formed, which is not preferable. Further, this copolymer may be melamine aldehyde crosslinked or isocyanate crosslinked. In the present invention,
The hydroxyl value refers to a value measured based on JIS-K0070.

On the other hand, as the styrene-acrylic copolymer used for the coating resin for the carrier core material of the developer B of the present invention, a copolymer of a styrene derivative and an acrylic ester and a styrene derivative and a methacrylic ester are used. A copolymer with a class. The following compounds can be mentioned as specific examples of the monomers constituting these styrene-acrylic copolymers.

That is, as the styrene derivative, styrene, o-methylstyrene, m-methylstyrene, p-
Methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, p- n-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-chlorostyrene, 3,4-dichlorostyrene, m-nitrostyrene, o-nitrostyrene, p-nitro Examples include styrene and the like.

Examples of acrylates include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, and the like.
2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate and the like can be mentioned.

Further, as the methacrylic acid esters, for example, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate,
Isobutyl methacrylate, n-octyl methacrylate,
Dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate and the like can be mentioned.

The copolymer used in the coating resin for the carrier core material of the developer B of the present invention preferably has a monomer ratio of the acrylic component in the copolymer of 30 to 90% by weight. If the amount is less than 30% by weight, the coating uniformity sufficient to contribute to the present invention cannot be obtained, and the toner has insufficient charge stability. On the other hand, if it is more than 90% by weight, uniform coverage is obtained, but the strength against impact resistance is insufficient.

Furthermore, the weight average molecular weight of the above-mentioned copolymer used as the coating resin for the carrier core material of the developer B of the present invention is essentially about 30,000 to 70,000, and
It is essential that the weight average molecular weight / number average molecular weight is 2 to 10. If the weight average molecular weight is less than 30,000, the strength with respect to impact resistance of the carrier cannot be obtained, and 70
If it is more than 000, the coverage with respect to the carrier core becomes poor, and the strength of the carrier and the charging stability become poor. More importantly, at this time, even if the weight average molecular weight is within this range, the weight average molecular weight /
The effect of the present invention cannot be obtained unless the number average molecular weight is within the range of 2 to 10. When the weight average molecular weight / number average molecular weight is less than 2, the coating resin is uniformly coated, but the impact resistance is poor. If the weight average molecular weight / number average molecular weight is larger than 10, the uniformity of the coating on the carrier core becomes poor, and the strength of the carrier and desired charge stability cannot be obtained.

Examples of the fluorine-containing resin used in combination with the coating resin for the carrier core material of the present invention include polyvinyl fluoride, polyvinylidene fluoride, halofluoropolymers such as polytrifluoroethylene and polytrifluorochloroethylene, and polytetrafluoroethylene. Fluoroethylene, polyperfluoropropylene, a copolymer of vinylidene fluoride and an acrylic monomer, a copolymer of vinylidene fluoride and trifluorochloroethylene, a copolymer of tetrafluoroethylene and hexafluoropropylene, Copolymer of vinyl fluoride and vinylidene fluoride, copolymer of vinylidene fluoride and tetrafluoroethylene, copolymer of vinylidene fluoride and hexafluoropropylene, tetrafluoroethylene and vinylidene fluoride and non-fluorinated Fluoroterpolymers such as monomeric terpolymers It is below.

The mixing ratio of the fluorine-containing resin to the vinyl resin having a hydroxyl group is, specifically, the ratio (weight ratio) of the fluorine-containing resin to the vinyl resin having a hydroxyl group is from 5:95. 95: 5, more preferably 1
0:90 to 90:10 is good. When the content of the fluorine-containing resin is less than 5% by weight, the exposed amount of the fluorine-containing resin in the uniform resin coating layer tends to be insufficient, while when the content of the fluorine-containing resin exceeds 95% by weight. Since the amount of the vinyl resin having a hydroxyl group is small, the adhesiveness of the resin coating layer to the core material tends to decrease.

The mixing ratio of the fluororesin and the styrene-acrylic copolymer is 5:95 by weight.
It is preferably ˜95: 5. When the content is within the above range, desired charge stability can be obtained with both positive and negative polarity developers, but when the content of the fluorine-containing resin is less than 5% by weight, the development showing positive charging characteristics is achieved. When the content of the fluorine-containing resin exceeds 95% by weight, the charge stability of the developer decreases and the charge stability of the developer exhibits negative charge characteristics. As a result, the uniform coating on the core material becomes difficult.

The weight average molecular weight of the fluorine-containing resin is preferably 50,000 to 400,000, more preferably 100,000 to 250,000. If it is less than 50,000, the impact resistance tends to be insufficient, and 4
If it exceeds 00000, uniform application to the core material becomes unstable.

In the present invention, the molecular weight and molecular weight distribution of the coating resin that can be used as the coating resin for the carrier core material, and the molecular weight of the fluorine-containing resin are those of monodisperse standard by GPC (gel permeation chromatography). The value obtained by observing the calibration curve obtained using polystyrene. The measurement conditions are shown below.

Apparatus: GPC-150C (Waters Co.) Column: Showdex KF 7 series (Showa Denko KK) Temperature: 40 ° C. Solvent: THF (tetrahydrofuran) Flow rate: 1.0 ml / min Sample: 0.15% sample 0.4 ml injection As the binder resin used in the core material in the constitution of the carrier of the present invention, all resins obtained by polymerizing vinyl monomers can be mentioned. Examples of the vinyl-based monomer here include styrene, o-methylstyrene, m-
Methylstyrene, p-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn- Octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, p-methoxy styrene, p-chlorostyrene, 3,4-dichloro styrene, m-nitro styrene, o-nitro Styrene derivatives such as styrene and p-nitrostyrene, and ethylene and unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; unsaturated diolefins such as butadiene and isoprene; vinyl chloride, vinylidene chloride,
Vinyl halides such as vinyl bromide and vinyl fluoride; vinyl esters such as vinyl acetate, vinyl propionate and vinyl benzoate; methacrylic acid and methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate. , Isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate,
Α-Methylene aliphatic monocarboxylic acid esters such as phenyl methacrylate; acrylic acid and methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-acrylic acid
Acrylic esters such as octyl, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate; maleic acid, maleic acid half ester; vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl Vinyl ethers such as ethers; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone; N-vinyl compounds such as N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole and N-vinyl pyrrolidone; Vinylnaphthalene;
Acrylic or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile and acrylamide; acrolein and the like, and one or two of these
The thing polymerized using more than 1 type is used.

In addition to resins obtained by polymerizing 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, or these resins. And a mixture of the above vinyl-based resin can be used.

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, magnetite, hematite and the like, and strong metals such as iron, cobalt and nickel. Examples include alloys or compounds containing an element exhibiting magnetism. The magnetic force of the magnetic fine particles according to the present invention in a magnetic field of 10 K oersted is 60 emu / g.
That is all. If it is less than 60 emu / g, even if the content of the magnetic fine particles is increased, the carrier is likely to adhere to the photoreceptor. The magnetic force of the magnetic material of the present invention was measured by VSM manufactured by Toei Industry Co., Ltd.

The magnetic fine particles preferably have a primary average particle diameter of 2.0 μm or less. If it is larger than 2.0 μm, the surface of the core material is not dense and uniform coating cannot be achieved. Furthermore, it is necessary that the magnetic fine particles according to the present invention have a specific resistance of 10 ⁹ Ω · cm or less and a content of 30% by weight or more, preferably 50% by weight or more based on the total amount of carriers. If it is less than 30% by weight, adhesion to the photoreceptor occurs, and it becomes difficult to control the resistance of the carrier.

Therefore, in the magnetic substance-dispersed carrier of the present invention, it is important not only that it does not adhere to the photoconductor but also that it can be controlled appropriately in terms of controlling the amount of charge of the toner. Is one. In particular, it is characterized in that the specific resistance of the carrier can be appropriately controlled so as not to cause the so-called charge-up phenomenon, that is, the excessive charging of the toner under a low humidity condition. Therefore, in the carrier of the present invention, as described above, The particle size, 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.
It can be preferably used in the range of 60 μm. 10μ
If it is smaller than m, carrier adhesion to the photoconductor is likely to occur, and if it exceeds 60 μm, the share of the developer in the developing device becomes large, resulting in deterioration of the developer, especially peeling of external additive of toner particles, shape. It causes a change and causes image deterioration. Furthermore, if the particle size is large, the specific surface area becomes small, so that the amount of toner that can be held in constituting the developer becomes small, and the image lacks fineness. The particle size of the carrier core of the present invention is randomly determined by an optical microscope or a scanning electron microscope to be 300.
More than one piece was extracted and the maximum horizontal chord length was measured as the carrier particle size.

The true specific gravity of the carrier of the present invention is 1.5.
The range of to 5.0 is preferable. More preferably 1.5 to
It is 4.5. When the true specific gravity exceeds 5.0, the share of the developer in the developing device becomes large, 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 in the present invention was measured by a Trudencer (manufactured by Seishin Enterprise).

The specific resistance of the carrier of the present invention is 10 ⁷ to 10
A range of ¹⁴ Ω · cm is suitable. If it is less than 10 ⁷ Ω · cm, in the developing method in which a bias voltage is applied, current leaks from the sleeve to the surface of the photoconductor in the developing area, and a good image cannot be obtained. On the other hand, when it exceeds 10 ¹⁴ Ω · cm, a charge-up phenomenon is caused under conditions such as low humidity, which causes image deterioration such as density density, transfer failure, and fog. The specific resistance of the carrier of the present invention was measured using the cell shown in FIG. That is, the cell A was filled with a carrier, the electrodes 1 and 2 were arranged so as to be in contact with the filled carrier, a voltage was applied between the electrodes, and the current flowing at that time was measured to determine the specific resistance. The measurement condition is that the contact area S of the filled carrier with the cell is about 2.3 cm.
² , thickness d = about 1 mm, upper electrode load 275 g, and applied voltage 100 V. Since the carrier is powder, the specific resistance may change depending on the filling rate, so be careful.

In view of keeping the specific resistance of the carrier of the present invention within the above range, the specific resistance can be easily improved by coating a low-resistance core material containing magnetic fine particles with the resin of the present invention. Controllability is a feature of the invention. That is, the surface exposed 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, for example, in the measurement, even if the resistance is the same, there is a part where the resistance is partially low as the carrier. If present, the image tends to be disturbed. Therefore, in order to obtain good developability, it is necessary to keep the resistance of each part of the carrier surface substantially the same by uniform resin coating, and this is a feature of the present invention.

Further, in order that the resistance of each part on the surface of the core material is uniform, it is considered preferable that the magnetic fine particles are uniformly dispersed on each part of the surface of the core material. However, when the dispersion state of the magnetic fine particles in the core material was observed with a scanning electron microscope, the carrier in the present invention, the magnetic fine particles are uniformly dispersed in each site of the core material surface, and The present inventors have found that at least a part of the core material is substantially exposed on the surface of the core material.

The sphericity of the carrier in the present invention (long axis /
The minor axis) is preferably 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 be reduced. Therefore, the sphericity is preferably 2 or less in order to prevent the effects of preventing the deterioration of the developer and improving the developing characteristics that can be achieved by the carrier in the present invention.

As means for achieving the above-mentioned sphericity of 2 or less in the carrier of the present invention, there is a method of heating the core material to heat-melt the surface to make it spherical, or a method of making it mechanically spherical. Alternatively, the core material may be produced by adding magnetic fine particles, a polymerization initiator, a suspension stabilizer, etc. to a monomer solution of a binder resin used for the core material and dispersing them, and then granulating and polymerizing the core material. If a usual suspension polymerization method for obtaining a material is used, it is possible to achieve a sphericity of 2 or less for the carrier without treating the core material.

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

The method of manufacturing the carrier of the present invention comprises two steps of forming a core material and then coating with a resin.

First, as a method for producing the core material, the binder resin and the magnetic fine particles are mixed in a desired amount ratio, and, for example,
A method of producing by kneading at a suitable temperature using a heating and melting mixer such as a three-roll or an extruder, cooling, and then pulverizing and classifying, or dissolving a binder resin in a soluble solvent, and then adding a magnetic material After mixing the fine particles to form a slurry, a method of granulating and drying using a spray dryer, or magnetic fine particles, polymerization initiator, suspension stabilizer, etc. in the monomer solution of the binder resin for the core material There is a suspension polymerization method in which granulation polymerization is carried out after adding and dispersing. In particular,
According to the above-mentioned polymerization method, not only it is easy to control the sphericity to 2 or less, but also the magnetic fine particles are uniformly dispersed in each part of the core material surface, and at least one of the magnetic fine particle surfaces is Since it is possible to control the part to be substantially exposed to the surface of the core material, it is a more preferable method for producing the core material for obtaining the effect of the present invention.

Next, as a method for coating the core material with a resin,
Considering that the core material is composed of 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 the selection of the solvent that dissolves the coating resin and the treatment temperature, time, etc. A treatment method in which the coating and the drying are simultaneously carried out in such a manner that the conditions are sufficiently controlled and the core material is always fluidized is preferably used. The resin coating amount varies depending on the true specific gravity of the core material, and the optimum value needs to satisfy the following relational expression.

1 / 2X ≦ resin coating amount ≦ 50 / X (wt%) (X: true specific gravity) More preferably, 1 / X ≦ resin coating amount ≦ 25 / X (wt%).

If the amount of the coating resin is less than ½ × wt%, it is difficult to uniformly coat the surface of the core material, and even if it can be coated, it cannot be said that the carrier has sufficient strength.
On the other hand, if it exceeds 50 / X% by weight, it becomes difficult to coat uniformly, and it becomes impossible to control the resistance to an optimum value, which is a feature of the present invention. Further, the coating resin that cannot be coated alone is liberated and generated, and adheres to the photoconductor to cause image deterioration.

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

For example, homopolymers of styrene and its substitution products such as polystyrene, poly-p-chlorostyrene and polyvinyltoluene; styrene-p-chlorostyrene copolymers, styrene-vinyltoluene copolymers, styrene-
Vinyl naphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid 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 -Based copolymer: polyvinyl chloride, phenol resin, natural modified phenol 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, coumarone indene resin, petroleum-based resin can be used.

In the heating and pressure roller fixing method in which oil is hardly applied, the offset phenomenon in which a part of the toner image on the toner image supporting member is transferred to the roller and the adhesion of the toner to the toner image supporting member are important. It's a problem.
Toners that fix with less heat energy usually have the property of easily blocking or caking during storage or in a developing device, and therefore these problems must be taken into consideration at the same time. Therefore, the selection of the binder resin is more important when the heating and pressure roller fixing method in which the oil is hardly applied is used in the present invention. A preferable binder resin is a cross-linked styrene copolymer or a cross-linked polyester.

Examples of the comonomer for the styrene monomer of the styrene type copolymer include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate,
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 A dicarboxylic acid having a double bond such as maleic acid, butyl maleate, methyl maleate, and dimethyl maleate; and a substituted product thereof; for example, vinyl chloride, vinyl acetate, vinyl benzoate Vinyl esters such as ethylene; propylene, butylene, etc .; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone; vinyl vinyl ether, vinyl ethyl ether, etc. 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, aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; for example, ethylene glycol diacrylate and ethylene glycol diethylene. Methacrylate, 1,3
A double bond such as futandiol dimethacrylate
Carboxylic acid ester having one; divinylaniline, divinyl ether, divinyl sulfide, divinylsulfone divinyl compound; and a compound having three or more vinyl groups; 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 a binder resin (preferably 0.05 to 5% by weight) at the time of synthesis in terms of offset resistance and fixing property.

When the pressure-fixing system is used, a binder resin for pressure-fixing toner can be used, and examples thereof include polyethylene, polypropylene, polymethylene, polyurethane elastomer, ethylene-ethyl acrylate copolymer,
There are ethylene-vinyl acetate copolymers, ionomer resins, styrene-butadiene copolymers, styrene-isoprene copolymers, linear saturated polyesters, and paraffins.

In the toner according to the present invention, charge controllability is blended with toner particles (internal addition) or mixed with toner particles (external addition).
It is preferable to use. The charge control agent makes it possible to control the optimum charge amount according to the developing system, and in particular, in the present invention, it is possible to further stabilize the balance between the particle size distribution and the charge. As described above, it is possible to further clarify the function separation and the mutual complementarity for improving the image quality depending on the particle size range. As the positive charge control agent, a modified product of nigrosine and a fatty acid metal salt; tributylbenzylammonium-1-hydroxy-4-naphthosulfonate,
Quaternary ammonium salt such as tetrabutylammonium tetrafluoroborate; dibutyltin oxide; diorganotin oxide such as dioctyltin oxide, dicyclohexyltin oxide; dibutyltin borate, dioctyltin borate, dicyclohexyltin borate, used alone or in combination of two or more kinds. be able to.

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

The charge control agent (which does not act as a binder resin) described above is preferably used in the form of fine particles. In this case, the number average particle size of this charge control agent is
Specifically, it is preferably 4 μm or less (further, 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) with respect to 100 parts by weight of the binder resin. As the colorant, conventionally known dyes and / or pigments can be used. For example, carbon black, phthalocyanine nimble and peacock blue, permanent red, lake red, rhodamine lake, Hansa yellow, permanent yellow, benzidine yellow and the like can be used. The content thereof 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, and the toner image is further fixed to O.
In order to improve the transparency of the HP film, it is preferably 12 parts by weight or less, more preferably 0.5 to 9 parts by weight.

The toner according to the present invention contains a low molecular weight polyethylene, a low molecular weight polypropylene, a microcrystalline wax, and a low molecular weight polypropylene for the purpose of improving the releasability at the time of heat roll fixing.
Addition of a wax-like substance such as carnauba wax, sazol wax and paraffin wax in an amount of 0.5 to 5 wt% is also one of the preferred embodiments of the present invention.

As the fluidity improver which can be used in the present invention, two or more kinds can be used. Examples include alumina, titanium oxide, and hydrophobic silica.

Alumina and titanium oxide can be obtained with a fine particle size relatively easily by the vapor phase method, but there is no particular limitation as a manufacturing method. However, particles having a plate shape or a needle shape are not preferable.

The surface hydrophobizing treatment may or may not be performed. Also, there is no particular restriction on the crystal structure.

Hydrophobic silica has a greater effect of imparting fluidity when the degree of hydrophobicity is higher than a certain level, and is good, but there is no particular limitation when used in the present invention.

The amount of the fluidity improver applied is 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the classified toner. If it is less than 0.01 part by weight, there is no effect in improving fluidity. On the other hand, if it exceeds 10 parts by weight, fog, character bleeding, and scattering within the machine are promoted. Particularly, in the case of color toner, when a 0HP image is formed, the sharpness of color is lost.

To prepare the toner according to the present invention, a vinyl-based or non-vinyl-based thermoplastic resin, and if necessary, a pigment or dye as a colorant, a charge control agent, and other additives are mixed in a mixer such as a ball mill. After sufficiently mixing with a heating roll, a kneader, using a heat kneader such as an extruder, knead and knead meat to disperse or dissolve the pigment or dye in the resin to make them compatible with each other, and cool. After singulation, pulverization and strict classification can be performed to obtain toner particles. The toner particles can be used as a toner as they are, 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. A toner can be obtained by mixing and.

Regarding the particle size distribution of the toner used in the present invention, in the case of the developer A, it is preferable that the non-magnetic toner particles having a particle size of 4 μm or less account for 15 to 60% of the total number of particles. Is preferably 20 to 60% by number. If the non-magnetic toner particles having a particle size of 4 μm or less are 15% by number,
There are few non-magnetic toner particles effective for high image quality, and in particular, as the toner is used by continuing copying or printing out, the effective non-magnetic toner particle component decreases, and the non-magnetic toner particles of the present invention are The balance of the particle size distribution deteriorates, and the image quality gradually deteriorates. 60
If it exceeds the number%, the non-magnetic toner particles are likely to aggregate with each other, resulting in toner lumps having a particle size larger than the original particle size, resulting in rough image quality, lower resolution, and edge portion of the latent image. The density difference between the inside and the inside becomes large, and the image tends to be hollow.

In the case of the developer B, the non-magnetic toner particles having a particle diameter of 4 μm or less are preferably 13 to 60% by number of the total number of particles, preferably 15 to 60% by number, and further preferably 20. -60% by number is good. The significance of this numerical limitation is the same as in the case of the developer A.

In the developer A, particles in the range of 4 to 8 μm are 10 to 60% by number, preferably 10 to 50% by number, and more preferably 10 to 40% by number. If it is more than 50%, especially 60%
If it exceeds, the image quality is deteriorated, and more than necessary development (that is, excessive toner deposition) occurs, resulting in an increase in toner consumption. On the other hand, if it is less than 10% by number, it becomes difficult to obtain a high image density. There is a relationship of N / V = −0.32N + k between the number% (N%) and the volume% (V%) of the non-magnetic toner particle group having a particle diameter of 4 μm or less, and 13 ≦
A positive number in the range of k ≦ 20 is shown. Preferably 13.5 ≦ k
≦ 19.5. As shown above, 15 ≦ N ≦ 6
0, preferably 20 ≦ N ≦ 60.

When k <13, the number of non-magnetic toner particles having a particle size smaller than 4.0 μm is small, and the image density, resolution and sharpness are inferior. The proper presence of fine non-magnetic toner particles, which has been conventionally thought to be unnecessary, contributes to close packing of toner in development and formation of a uniform image without roughness. In particular, the fine lines and the contour portion of the image are evenly filled to further enhance the sharpness visually. When k <13, these properties are inferior due to the lack of the particle size distribution component.

From another aspect, in terms of production, it is necessary to cut a large amount of fine powder by means such as classification in order to satisfy the condition of k <13, which is also disadvantageous in terms of yield and toner cost. Becomes When k> 20, the image density tends to decrease during continuous repeated copying due to the presence of fine powder more than necessary. Such a phenomenon is caused by excessive fine powder non-magnetic toner particles, which are charged more than necessary, being charged and attached on the developing sleeve and / or carrier, so that normal non-magnetic toner is carried and charged on the developing sleeve or carrier. It is considered to occur by inhibiting the application.

In the developer B, particles in the range of 4 to 8 μm are 10 to 70% by number, preferably 10 to 50% by number, more preferably 10 to 40% by number. Number% of non-magnetic toner particles having a particle size of 4 μm or less
(N%) and volume% (V%), N / V = -0.32
There is a relationship of N + k, and a positive number in the range of 13 ≦ k ≦ 20 is shown. Preferably, 13.5 ≦ k ≦ 19.5. As indicated above, 13 ≦ N ≦ 60, preferably 15 ≦ N ≦
60, and more preferably 20 ≦ N ≦ 60.

The significance and reason for limiting these numerical values are the developer A.
It is similar to the case of.

The content of the non-magnetic toner particles having a particle size of 16.0 μm or more in the developers A and B is preferably less than 2.0% by volume, more preferably 1.0% by volume or less. 2.0
When the content is more than the volume%, not only does it hinder the reproduction of fine lines, but also in the transfer, coarse toner particles of 16.0 μm or more are prominently present on the thin layer surface of the toner particles developed on the photoreceptor, The delicate contact state between the photoconductor and the transfer paper via the toner layer is made irregular, which causes fluctuations in the transfer conditions and causes a defective transfer image.

The particle size distribution of the toner can be measured by various methods, but in the present invention, it was measured using a Coulter counter.

A Coulter counter T is used as a measuring device.
A-II type (manufactured by Coulter) was used. As the electrolytic solution, a 1% NaCl aqueous solution was prepared using first-grade sodium chloride. As a measuring method, the electrolytic aqueous solution is 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 is suspended is subjected to a dispersion treatment for about 1 to 3 minutes by an ultrasonic disperser, and then 10 times as an aperture with the Coulter Counter TAII
2μ to 40μ based on the number using 0μ aperture
The particle size distribution of the above particles was measured, and then the value related to the present invention was determined.

[0089]

The present invention will be described below with reference to examples and drawings. This does not limit the invention in any way. Examples 1 to 5 relate to the developer A of the present invention, and Examples 6 to 10 relate to the developer B of the present invention. In addition,% in the following formulation
All parts and parts are by weight and parts by weight.

(Example 1) Styrene 22.2% 2-Ethylhexyl acrylate 11.1% Reduced iron (particle diameter 0.32 μm) 66.7% The above materials were heated in a container at a temperature of 70 ° C. to be dissolved. It was a monomer mixture. While maintaining the temperature at 70 ° C., an initiator azobisisonitrile was added and dissolved to prepare a monomer composition. This was put into a 2 liter flask containing 1.2 liter of 1% PVA aqueous solution, and stirred at 70 ° C. with a homogenizer at 4500 rpm for 10 minutes to granulate the composition. Then, while stirring with a paddle stirrer,
Polymerization was performed for 10 hours. After the completion of the polymerization reaction, the reaction product was cooled, and the obtained magnetic substance-dispersed styrene acrylic slurry was washed and filtered. This was dried to obtain magnetic substance-dispersed resin particles.

The surface of the obtained magnetic substance-dispersed resin particles was coated with the following resin coating layer.

Styrene-2-hydroxyethyl methacrylate-methyl methacrylate copolymer 55% (monomer composition weight ratio = 35: 8: 57 hydroxyl number (KOHmg / g) = 30 weight average molecular weight = 52,000) Fluorine Vinylidene-tetrafluoroethylene copolymer 45% (monomer composition weight ratio = 75: 25 weight average molecular weight = 210,000) The above resin has a resin coating amount of 0.8% from the above calculation formula.
10% in a mixed solvent of acetone and methyl ethyl ketone (mixing weight ratio = 1: 1) to prepare a carrier coating solution. This carrier coating solution was applied to the above core material by a coating machine (Okada Kogyo Co., Ltd .: Spiracoater) while simultaneously performing coating and drying. The obtained magnetic substance-dispersed resin carrier after coating was dried at a temperature of 90 ° C. for 2 hours to remove the solvent, to obtain a resin-coated magnetic substance-dispersed resin carrier in which magnetic substance-dispersed fine particle surfaces were coated with a resin coating layer. When the obtained resin-coated magnetic material-dispersed resin carrier was observed with an electron microscope, the core material was uniformly coated with the resin, and the magnetic material particles were substantially uniformly exposed on the coated surface. Was confirmed.

The physical properties of the obtained carrier are summarized in Tables 1 and 2.

On the other hand, polyester resin obtained by condensation of propoxylated bisphenol and fumaric acid 100 parts Phthalocyanine pigment 5 parts Di-tert-butylsalicylic acid chromium complex salt 4 parts After sufficiently premixing the above materials with a Henschel mixer The mixture was melt-kneaded three times with a three-roll mill, cooled, and coarsely pulverized with a hammer mill to a particle size of about 1 to 2 mm.
Then, it was pulverized by an air jet pulverizer. Further, the obtained finely pulverized product is classified to have a negatively chargeable cyan powder (toner) having a weight average diameter of 8.9 μm.
Got The particle size distribution of the cyan toner was N = 27.2 number% and V = 5.8% by volume for particle sizes of 4 μm or less, and 0% by volume for particle sizes of 16.0 μm or more. The N and N / V of the toner are within the specified range of the present invention as shown in FIG.

100 parts of the cyan toner and 1.0 part of silica fine powder hydrophobized with hexamethyldisilazane were mixed by a Henschel mixer to prepare a cyan toner having silica fine powder on the toner particle surface.

This cyan toner and the above resin carrier were mixed in an environment of temperature / humidity of N / N (23 ° C./60% RH) so that the toner concentration would be 4% to obtain a developer. 100 g of the obtained developer was put in a 250 cc plastic bottle, and shaken by a turbula mixer for 1 hour. After that, the developer was taken out and observed with an electron microscope. As a result,
Desorption of the magnetic material from the carrier, peeling of the coating material, and filming by the toner were not observed. Further, neither detachment of the external additive of the toner nor burial was observed.

Further, a cyan toner and the above resin carrier were mixed in an environment of temperature / humidity of L / L (15 ° C./10% RH) so as to have a toner concentration of 4% to obtain a developer. This is a Canon full-color laser copier CLC-
Put it in the developing device for 500 and drive it with an external motor (peripheral speed 3
Idle rotation was performed for 30 minutes at (00 rpm). After this, C
Using LC-500, an image was output with a development contrast of 300V. As a result, the density of the solid image was sufficient, and the reproducibility of the halftone portion and the line image was good.

Further, when a 10,000-sheet durability image producing test was conducted, the solid image density, the halftone portion and the reproducibility of the line image were good.

Comparative Example 1 Using the core material of Example 1,
As in Example 1, the coating resin used in Example 1 was coated so that the coating amount was 0.8%. With this carrier, a weight average diameter of 5.0 μm and a particle size of 4 μm or less is N =
62.2% by number, V = 28,7% by volume, Example 1
Cyan toner with the same composition as
Under a (15 ° C./10% RH) environment, the toner concentration was mixed to 4% to obtain a developer. Using this, the same measurement and test as in Example 1 were performed. As a result of the shaking test, toner filming on the carrier surface was observed. Also, as a result of the image output test, the initial image was good,
Further, when a durability test was conducted on 10,000 sheets, the halftone portion was found to be rough, the line image was lost, and the image density was lowered.

The N and N / V of the above-mentioned toner are out of the specified range of the present invention as shown in FIG.

COMPARATIVE EXAMPLE 2 Instead of the core material used in Example 1, 46 μm reduced iron particles were used and the coating resin used in Example 1 was changed to a coating amount of 0.8% as in Example 1. Coated. The obtained carrier and the same toner as that used in Example 1 were mixed in the same manner as in Example 1 to obtain a developer. Using this, the same measurement and test as in Example 1 were performed.

As a result of the shaking test, the carrier did not change from that before shaking, but the burial of the external additive on the toner surface was observed. Further, as a result of the image output test, the initial image was good in halftone and the line image was good, but as a result of the durability image output test of 10,000 sheets, the halftone was rough and the line image was disturbed. It was

Comparative Example 3 A vinylidene fluoride-tetrafluoroethylene copolymer was used in place of the carrier coating solution used in Example 1 in the core material used in Example 1 (monomer composition weight ratio = 75: 25 weight average). (Molecular weight = 210,000) was used to prepare a carrier coating solution by dissolving 10% in a mixed solvent of acetone and methyl ethyl ketone so that the resin coating amount would be 1.0%.

The carrier coating solution was applied in the same manner as in Example 1 to obtain a carrier in which the surface of the carrier core material was coated with a resin coating layer. Physical properties of this carrier are shown in Tables 1 and 2.

Microscopic observation revealed that the core material was not uniformly coated. Further, the same test as in Example 1 was conducted using this carrier.

As a result of the shaking test, peeling of the coating material was observed, and some detachment of the magnetic material was also observed. Further, as a result of the image output test, image unevenness occurred.

Example 2 As a carrier, Example 1 is used.
The same one was used. Also, as a toner, styrene-2-ethylhexyl acrylate-dimethylaminoethyl methacrylate copolymer 100 parts (monomer composition weight ratio = 80/15/5) copper phthalocyanine 4 parts low molecular weight polypropylene 5 parts The above materials were used in Example 1 Weight average diameter of 5.0μ
m, 4 μm or less, N = 50.8 number%, V
= 21.4% by volume of blue particles were obtained. As shown in FIG. 2, N and N / V of this particle are within the specified region in the present invention. To 100 parts of the particles, 1.2 parts of positively chargeable colloidal silica treated with amino-modified silicone oil was mixed with a Henschel mixer to obtain a positively chargeable blue toner.

The above toner and carrier were mixed with each other in a toner concentration of 3.
A developer was prepared by mixing so as to be 5%, and a test was conducted in the same manner as in Example 1 using a Canon copying machine NP4835. As a result, excellent positive charging property was obtained in the initial and durable image forming tests. A uniform image was obtained.

Example 3 Styrene-2-ethylhexyl acrylate 50% (55/45) copolymer Reduced iron 50% The above materials were thoroughly premixed with a Henschel mixer and then at least twice with a three roll mill. The mixture was melt-kneaded, cooled, and then roughly pulverized to a particle size of about 2 mm using a hammer mill. Next, it was pulverized to a particle size of about 50 μm with an air jet pulverizer. Further, the obtained finely pulverized product was put into MechanoMill MM-10 (manufactured by Okada Seiko) and mechanically spheroidized.

The pulverized finely pulverized particles were further classified to obtain magnetic substance-dispersed resin particles. The particle size of the obtained magnetic substance-dispersed resin particles was 49 μm.

A coating layer was provided on the surface of the obtained magnetic substance-dispersed resin particles in the same manner as in Example 1 to obtain a resin-coated carrier.

Physical properties of this carrier are shown in Tables 1 and 2. Further, this carrier was tested in the same manner as in Example 1.

As a result, a shaking test was conducted in the same manner as in Example 1,
It was good in the initial and durable image forming tests.

Example 4 Polyester resin obtained by condensing 40% (50/40/10) of ethoxylated bisphenol-fumaric acid-trimellitic acid Magnetite (particle diameter 0.26 μm) 60% The above materials were carried out. In the same manner as in Example 2, spherical magnetic substance-dispersed resin particles were obtained. The particle size of the particles was 52 μm.

The surface of the obtained magnetic substance-dispersed resin particles was coated with the following coating resin in the same manner as in Example 1.

Styrene-2-hydroxyethyl methacrylate-methyl methacrylate-ethyl methacrylate 38% (monomer composition weight ratio = 57: 20: 13: 10 hydroxyl value = 40 weight average molecular weight = 54,000) methyl etherified melamine Formaldehyde resin 12% Vinylidene fluoride-tetrafluoroethylene copolymer 50% (monomer composition weight ratio = 75: 25 weight average molecular weight = 210,000) was added to a methyl ethyl ketone solution at 10% so that the resin coating amount would be 1.2%. % Of the carrier coating solution was used to coat the resin fine particles in the same manner as in Example 1 to obtain a magnetic substance-dispersed resin carrier. The physical properties of the obtained carrier are shown in Tables 1 and 2. Further, when the same test as in Example 1 was conducted, good results were obtained as in Example 1.

Example 5 Phenol 10.0% Formaldehyde (Formaldehyde approx. 37% 5.0% Methanol approx. 10% Remainder water) Magnetite (particle size 0.25 μm) 85.0% Using the above materials as a basic catalyst Using ammonia and calcium fluoride as a polymerization stabilizer, the mixture was stirred in an aqueous phase, gradually heated to a temperature of 80 ° C., and polymerized for 2 hours. The particle size of the obtained magnetic material-dispersed resin particles was 42 μm. The resin particles were coated in the same manner as in Example 3 with a methyl ethyl ketone solution in which 10% of the coating resin used in Example 3 was dissolved to a resin coating amount of 1.0%. Physical properties of the obtained resin-coated carrier are shown in Tables 1 and 2. Further, when the same test as in Example 1 was conducted using this carrier, the same good result as in Example 1 was obtained.

Table 3 shows the evaluation results in the following examples and comparative examples.

[0119]

[Table 1]

[0120]

[Table 2]

[0121]

[Table 3] (Example 6) Styrene 22.2% 2-Ethylhexyl acrylate 11.1% Reduced iron (particle size 0.32 μm) 66.7% The above materials are heated in a container at a temperature of 70 ° C. to be dissolved, and monomers are added. It was a mixture. While maintaining the temperature at 70 ° C., an initiator azobisisonitrile was added and dissolved to prepare a monomer composition. This was put into a 2 liter flask containing 1.2 liter of 1% PVA aqueous solution, and stirred at 70 ° C. with a homogenizer at 4500 rpm for 10 minutes to granulate the composition. Then, while stirring with a paddle stirrer, 70 ° C, 1
Polymerization was performed for 0 hours. After the completion of the polymerization reaction, the reaction product was cooled, and the obtained magnetic substance-dispersed styrene acrylic slurry was washed and filtered. This was dried to obtain magnetic substance-dispersed resin particles.

The surface of the obtained magnetic substance-dispersed resin particles was coated with the following resin coating layer.

Styrene-isobutyl methacrylate copolymer 50% (monomer composition weight ratio = 45: 65 Mw 39000 Mw / Mn = 2.7) Vinylidene fluoride-tetrafluoroethylene copolymer 50% (monomer composition weight ratio = 75:25 weight average molecular weight = 210,000) The above-mentioned copolymer has a resin coating amount of 0.8% from the above calculation formula.
10% in a mixed solvent of acetone and methyl ethyl ketone (mixing weight ratio = 1: 1) to prepare a carrier coating solution. This carrier coating solution was applied to the above core material by a coating machine (Okada Kogyo Co., Ltd .: Spiracoater) while simultaneously performing coating and drying. The resulting coated magnetic material-dispersed resin carrier is dried at a temperature of 40 ° C. for 1 hour to remove the solvent, and then heated at a temperature of 110 ° C. for 2 hours to coat the surface of the magnetic material-dispersed fine particles with a resin coating layer. A body-dispersed resin carrier was obtained. When the obtained resin-coated magnetic material-dispersed resin carrier was observed with an electron microscope, the core material was uniformly coated with the resin, and the magnetic material particles were substantially exposed uniformly on the coated surface. Was confirmed.

The physical properties of the carrier thus obtained are summarized in Tables 4 and 5.

On the other hand, polyester resin obtained by condensing propoxylated bisphenol and fumaric acid 100 parts Phthalocyanine pigment 5 parts Di-tert-butylsalicylic acid chromium complex salt 4 parts After sufficiently premixing the above materials with a Henschel mixer The mixture was melt-kneaded three times with a three-roll mill, cooled, and coarsely pulverized with a hammer mill to a particle size of about 1 to 2 mm.
Then, it was pulverized by an air jet pulverizer. Further, the obtained finely pulverized product is classified to have a negatively chargeable cyan powder (toner) having a weight average diameter of 7.6 μm.
Got The particle size distribution of the cyan toner was N = 20.5 number% and V = 2.6% by volume for particle sizes of 4 μm or less, and 0% by volume for particle sizes of 16.0 μm or more. The N and N / V of the toner are within the specified range of the present invention as shown in FIG.

100 parts of the cyan toner and 1.0 part of silica fine powder hydrophobized with hexamethyldisilazane were mixed by a Henschel mixer to prepare a cyan toner having silica fine powder on the toner particle surface.

This cyan toner and the above resin carrier were mixed in an environment of temperature / humidity of N / N (23 ° C./60% RH) so that the toner concentration would be 4% to obtain a developer. 100 g of the obtained developer was put in a 250 cc plastic bottle, and shaken by a turbula mixer for 1 hour. After that, the developer was taken out and observed with an electron microscope. As a result,
Desorption of the magnetic material from the carrier, peeling of the coating material, and filming by the toner were not observed. Further, neither detachment of the external additive of the toner nor burial was observed.

Further, a cyan toner and the above resin carrier were mixed in an environment of temperature / humidity of L / L (15 ° C./10% RH) so that the toner concentration was 4% to obtain a developer. This is a Canon full-color laser copier CLC-
Put it in the developing device for 500 and drive it with an external motor (peripheral speed 3
Idle rotation was performed for 30 minutes at (00 rpm). After this, C
Using LC-500, an image was output with a development contrast of 300V. As a result, the density of the solid image was sufficient, and the reproducibility of the halftone portion and the line image was good.

Further, a 10,000 image durability test was carried out. As a result, the solid image density, the halftone portion and the reproducibility of the line image were good.

(Comparative Example 4) The same carrier as in Example 6 was used. This carrier and a weight average diameter of 6.
3 μm and N = 75.0 for particle sizes of 4 μm or less
A cyan toner having the same composition as in Example 6 in which the number% and V = 22.3% by volume was used, the temperature / humidity was L / L (15 ° C./1.
Under an environment of 0% RH), a developer was obtained by mixing so as to have a toner concentration of 4%. Using this, the same measurements and tests as in Example 6 were performed. As a result of the shaking test, aggregation of toner was observed. Further, as a result of the image output test, in the initial image and in the durability test of 10,000 sheets, the halftone portion was found to be rough, the line image was hollowed, and the image density was decreased.

The N and N / V of the above-mentioned toner are out of the specified region of the present invention shown in FIG.

(Comparative Example 5) In the same manner as in Example 6, except that the core material used in Example 6 was replaced by 45 μm reduced iron particles, the coating resin used in Example 6 was changed to a coating amount of 0.9%. Coated. The obtained carrier and the same toner as that used in Example 6 were mixed in the same manner as in Example 6 to obtain a developer. Using this, the same measurements and tests as in Example 6 were performed.

As a result of the shaking test, the carrier was not changed from that before shaking, but it was observed that the external additive was buried on the toner surface. Further, as a result of the image output test, the initial image was good in halftone and the line image was good, but as a result of the durability image output test of 10,000 sheets, the halftone was rough and the line image was disturbed. It was

Comparative Example 6 Instead of the carrier coating solution used in Example 6 for the core material used in Example 6, vinylidene fluoride-tetrafluoroethylene copolymer (monomer composition weight ratio = 60: 40 weight average) (Molecular weight = 220,000), 10% is dissolved in a mixed solvent of acetone and methyl ethyl ketone so that the coating resin amount becomes 1.0%,
A carrier coating solution was prepared.

The above carrier coating solution was applied in the same manner as in Example 6 to obtain a carrier in which the surface of the carrier core material was coated with the resin coating layer. Physical properties of this carrier are shown in Tables 4 and 5.

Microscopic observation revealed that the core material was not uniformly coated. Further, the same test as in Example 6 was conducted using this carrier.

As a result of the shaking test, peeling of the coating material was observed, and some detachment of the magnetic material was also observed. Further, as a result of the image output test, image unevenness occurred.

Example 7 As a carrier, Example 6 was used.
The same one was used. Further, as a toner, styrene-2-ethylhexyl acrylate-dimethylaminoethyl methacrylate copolymer 100 parts (monomer composition weight ratio = 80/15/5) copper phthalocyanine 4 parts low molecular weight polypropylene 5 parts The above materials were used in Example 6 Weight average diameter of 5.2μ
m, 4 μm or less, N = 50.2% by number, V
= 20.9% by volume of blue particles were obtained. N, N of this particle
/ V is within the specified region of the present invention, as shown in FIG.

To 100 parts of the above particles, 1.2 parts of positively chargeable colloidal silica treated with amino-modified silicone oil was mixed with a Henschel mixer to obtain a positively chargeable blue toner.

The toner and carrier were mixed with each other in a toner concentration of 3.
A developer was prepared by mixing so as to be 5%, and a test was performed in the same manner as in Example 6 using a Canon copying machine NP4835. As a result, excellent positive charging property was obtained in the initial and durable image forming tests. A uniform image was obtained.

(Example 8) Styrene-2-ethylhexyl acrylate 50% (55/45) copolymer Reduced iron 50% The above materials were sufficiently premixed by a Henschel mixer, and then at least twice with a three-roll mill. The mixture was melt-kneaded, cooled, and then roughly pulverized to a particle size of about 2 mm using a hammer mill. Next, it was pulverized to a particle size of about 52 μm by an air jet type pulverizer. Further, the obtained finely pulverized product was put into MechanoMill MM-10 (manufactured by Okada Seiko) and mechanically spheroidized.

The pulverized finely pulverized particles were further classified to obtain magnetic substance-dispersed resin particles. The particle size of the obtained magnetic material-dispersed resin particles was 50 μm.

A coating layer was provided on the surface of the obtained magnetic substance-dispersed resin particles in the same manner as in Example 6 to obtain a resin-coated carrier.

Physical properties of this carrier are shown in Tables 4 and 5. Further, this carrier was tested in the same manner as in Example 6.

As a result, a shaking test was conducted in the same manner as in Example 6,
It was good in the initial and durable image forming tests.

Example 9 Polyester resin obtained by condensing ethoxylated bisphenol-fumaric acid-trimellitic acid 40% (50/40/10) magnetite (particle diameter 0.26 μm) 60% The above materials were carried out. In the same manner as in Example 7, spherical magnetic substance-dispersed resin particles were obtained. The particle size of the particles was 51 μm.

The following coating resin was coated on the surface of the obtained magnetic substance-dispersed resin particles in the same manner as in Example 6.

Styrene-propyl acrylate-copolymer 50% (monomer composition weight ratio = 50: 50 Mw = 55,000) Vinylidene fluoride-tetrafluoroethylene copolymer 50% (monomer composition weight ratio = 75: 25) (Weight average molecular weight = 210,000) was coated on the resin fine particles in the same manner as in Example 6 using a carrier coating solution prepared by dissolving 10% in a methyl ethyl ketone solution so that the resin coating amount was 1.2%, A magnetic substance-dispersed resin carrier was obtained. The physical properties of the obtained carrier are shown in Tables 4 and 5. Further, when the same test as in Example 6 was performed, good results were obtained as in Example 6.

(Example 10) Phenol 10.0% Formaldehyde (Formaldehyde about 37% 5.0% Methanol about 10% The rest is water) Magnetite (particle size 0.25 μm) 85.0% The above material as a basic catalyst. Using ammonia and calcium fluoride as a polymerization stabilizer, the mixture was stirred in an aqueous phase, gradually heated to a temperature of 80 ° C., and polymerized for 2 hours. The particle size of the obtained magnetic substance-dispersed resin particles was 40 μm. The resin particles were coated in the same manner as in Example 8 using a methyl ethyl ketone solution in which the resin coating amount used in Example 3 was dissolved in 10% so that the resin coating amount was 0.9%. Table 6 shows the physical properties of the obtained resin-coated carrier. Further, when the same test as in Example 6 was performed using this carrier, the same good result as in Example 6 was obtained.

[0150]

[Table 4]

[0151]

[Table 5]

[0152]

[Table 6]

[0153]

As described above, by using the magnetic carrier coated with the coating resin used in the present invention, (1) spent resistance (2) impact resistance (prevention of carrier destruction) (3) toner deterioration Prevention (4) Developability (5) Prevention of carrier adhesion on the photoconductor (6) Control of carrier resistance (7) Stabilization of toner chargeability can be sufficiently satisfied, especially development using small particle size toner In the agent, deterioration of the developer can be reduced, and a high-quality image can be stably provided for a long period of time.

[Brief description of drawings]

FIG. 1 is a schematic diagram schematically showing an apparatus for measuring the specific resistance of a carrier.

FIG. 2 is a region diagram that satisfies a conditional expression for a toner particle group in the present invention (developer A).

FIG. 3 is a region diagram that satisfies a conditional expression for a toner particle group in the present invention (developer B).

[Explanation of symbols]

 1 Lower electrode 2 Upper electrode 3 Insulator 4 Ammeter 5 Voltmeter 6 Constant voltage device 7 Sample 8 Guide ring A Measuring cell

[Procedure amendment]

[Submission date] July 28, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0141

[Correction method] Change

[Correction content]

(Example 8) Styrene-2-ethylhexyl acrylate 50% (85/15) copolymer Reduced iron 50% The above materials were sufficiently premixed with a Henschel mixer, and then at least twice with a three-roll mill. The mixture was melt-kneaded, cooled, and then roughly pulverized to a particle size of about 2 mm using a hammer mill. Next, it was pulverized to a particle size of about 50 μm with an air jet pulverizer. Further, the obtained finely pulverized product was put into MechanoMill MM-10 (manufactured by Okada Seiko Co., Ltd.) and mechanically spheroidized.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location 7144-2H G03G 9/10 351 7144-2H 354

Claims (10)

[Claims] 1. An electrophotographic developer comprising at least a toner and a carrier, wherein the toner has a particle size distribution of 15 μm for a particle size of 4 μm or less.
-60% by number, and 10 for particle diameters of 4-8 μm
60% by number, 2.0% by volume or less for a particle size of 16.0 μm or more, and a weight average particle size of the toner of 4 to 10 μm, and a toner particle group of 4 μm or less is represented by the following formula N / V = −0.32N + k N: Number% of toner particles having a particle size of 4 μm or less, provided that the positive number is 15 to 60 V: Volume% of toner particles having a particle size of 4 μm or less k: A positive number of 13 to 20 And a magnetic material-dispersed carrier in which the carrier has a core material in which a magnetic material is dispersed in a binder resin, and the surface of the core material is coated with a resin. The resin that coats the surface of the core material has a hydroxyl value of 1
A developer for electrophotography, which is a vinyl-based copolymer having 100 to 100 and a fluororesin. 2. The true specific gravity of the carrier is 1.5 to 5.0.
The developer for electrophotography according to claim 1, wherein 3. The electrophotographic development 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. Agent. 4. The particle size of the carrier is 10 μm to 60 μm.
The electrophotographic developer according to any one of claims 1 to 3, wherein 5. The specific resistance of the carrier is from 10 ⁷ Ω · cm to
5. The resistance is 10 ¹⁴ Ω · cm.
The electrophotographic developer according to item 1. 6. An electrophotographic developer comprising at least a toner and a carrier, wherein the toner has a particle size distribution of 4 μm or less for a particle size of 13 or less.
-60% by number, and 10 for particle diameters of 4-8 μm
70% by number, 2.0% by volume or less for a particle size of 16.0 μm or more, and the weight average particle size of the toner is 4 to 10 μm, and a toner particle group of 4 μm or less has the following formula N / V = −0.32N + k N: number% of toner particles having a particle size of 4 μm or less, but a positive number of 13 to 60 V: volume% of toner particles having a particle size of 4 μm or less k: a positive number of 13 to 20 And a magnetic material-dispersed carrier in which the carrier has a core material in which a magnetic material is dispersed in a binder resin, and the surface of the core material is coated with a resin. The resin coating the surface of the core material is a styrene-acrylic copolymer and a fluorine-containing resin, and the monomer ratio of the acrylic component in the copolymer of the styrene-acrylic copolymer is 30 to 90% by weight. And weight flat A molecular weight distribution of about from 30,000 to 70,000, and a weight average molecular weight / number average molecular weight of 2.0
10 and the mixing ratio of the fluorinated resin to the styrene-acrylic copolymer is 5:95 to 95: 5 by weight ratio (weight of the fluorinated resin: weight of the copolymer).
A developer for electrophotography, characterized in that 7. The true specific gravity of the carrier is 1.5 to 5.0.
The developer for electrophotography according to claim 6, wherein 8. The electrophotographic development according to claim 6, 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. Agent. 9. The particle size of the carrier is 10 μm to 60 μm.
The electrophotographic developer according to any one of claims 6 to 8, wherein 10. The specific resistance of the carrier is 10 ⁷ Ω · cm.
10. The electrophotographic developer according to claim 6, wherein the electrophotographic developer has a resistance of about 10 ¹⁴ Ω · cm.