JP3218403B2 - Electrophotographic developer - Google Patents

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 electrophotography, electrostatic recording and electrostatic printing.

[0002]

2. Description of the Related Art Generally, in an electrostatic recording apparatus using electrophotography, selenium, OPC (organic photoconductor), α-S
Using a photoconductive substance such as i as a photoreceptor, the photoreceptor is uniformly charged by various means, and then the surface of the photoreceptor is irradiated with a light image 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 developed.

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 charged with an appropriate amount of positive or negative electric charge by triboelectric charging. Is imparted 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.

In recent years, in order to obtain high-quality images, the toner particle size has been reduced. However, on the other hand, if the load due to the carrier is large when the developer is used for a long period of time, the durability of the developer tends to deteriorate when the small particle size toner is used, and the image quality tends to deteriorate accordingly. Therefore, when a developer using a small particle size toner is used for a long period of time, the characteristics required for the carrier to maintain a high quality image include appropriate charging properties, pressure resistance to an applied electric field, and shock resistance. Properties, spent resistance, abrasion resistance, developability, productivity, etc., and it is particularly important to reduce the load on the developer.

In general, (1) If the true specific gravity of the carrier is too large, the developer is developed to a predetermined layer thickness on the sleeve by the developer layer thickness regulating member or by stirring in a developing machine. Due to the increased load on the developer, (a) the toner filming described above, (b) carrier destruction, and (c) deterioration of the toner are likely to occur during long-term use of the developer. As a result, the image quality of the developed image tends to deteriorate. (2) When the particle size of the carrier increases, the load on the developer increases as in (1) above.
To (c) tend to occur, and as a result, the developer tends to deteriorate. It is also well known that (d) poor reproducibility of a developed image on fine lines, that is, poor developability.

Accordingly, in a carrier in which the above (a) to (c) are likely to occur, it is necessary to periodically exchange the developer, and it 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.

It is necessary to deal with the problem of the developing property (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 pulverization method disclosed in Japanese Patent Application Laid-Open No. 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 Japanese Patent Application Laid-Open No. 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 carrier has a small saturation magnetization 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 adhered carrier must be provided in the image forming apparatus. Has the disadvantage that it cannot be done.

In addition, when the magnetic substance is dispersed in the magnetic substance-dispersed small particle size carrier in a large amount, the amount of the magnetic substance increases with respect to the binder resin, so that the impact resistance becomes weak. When the developer is adjusted to a predetermined layer thickness on the sleeve by the developer layer thickness regulating member, or due to agitation in a developing device, the magnetic substance is easily missing from the carrier. In this case, there is a disadvantage that it cannot be drastic as a measure for extending the life of the developer, since the deterioration of the developer tends to occur.

Further, in the above-mentioned magnetic substance dispersed small particle size carrier, when the magnetic substance is contained in a large amount, the resistance of the carrier decreases due to an increase in the amount of the magnetic substance having a low resistance. f) There is also a drawback that image defects tend to occur due to leakage of bias voltage applied during development.

Therefore, even with the magnetic substance-dispersed small-particle-size carrier having the above-mentioned increased magnetic substance, a drastic measure is required to improve the developability and extend the life of the developer when the small-particle toner is used. It has the disadvantage that it cannot be done.

On the other hand, it is also possible to cope with the technique of coating the carrier with a resin, which is disclosed in Japanese Patent Application Laid-Open No. 58-21750. According to the carrier coated with the above resin, spent resistance, impact resistance, and pressure resistance against 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-mentioned 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. When the charge-up phenomenon occurs easily, and when the amount of the coating resin is small, the resistance of the carrier becomes too low, so that an image defect easily occurs due to a leak of the developing bias voltage.

Further, depending on the coating resin, even if the resistance of the carrier coated with the resin is considered to be an appropriate resistance in the measurement, image defects are likely to occur due to leakage of the developing bias voltage, or charge in a low humidity environment. There is also a thing that the up phenomenon is easy to occur, the carrier coated with the above resin,
When the developability is considered, there is a problem that the control is difficult. In particular, when the particle size of the toner is reduced, the variation in 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 of the developer, the conventionally used carriers still have a problem to be improved, and are sufficiently satisfactory. What can be done is not known so far.

In particular, in a magnetic material-dispersed carrier in which magnetic particles are dispersed in a binder resin and the surface of which 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 photoreceptor (6) Control of carrier resistance (7) Stability of toner chargeability can be sufficiently satisfied. What can reduce the deterioration of the developer when a small particle size toner having a large specific surface area is used is not known at present.

Accordingly, a main object of the present invention is to solve the above-described 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. In addition, it stabilizes the chargeability of the toner at the time of running and fluctuations in humidity, and furthermore uses a small particle size toner having excellent image gradation and resolution, so that the developability and the life of the developer are more excellent. To provide a developing agent. 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 impact resistance of the carrier, the resistance value, and the charge application stability to the toner, It is an object of the present invention to provide a novel developer having improved developability and developer life even in a system using a small particle size toner, which is improved by the characteristics of the resin to be coated and which is liable to deteriorate the developer.

[0022]

Means and Action for Solving the Problems The present inventors have
As a result of intensive studies and studies to improve various drawbacks of the magnetic material-dispersed carrier whose surface is coated with a resin and to obtain a developer having excellent developability and durability, (1) particle size distribution of toner Is 15 to 60 for a particle size of 4 μm or less.
10 to 60% by number for a particle size of 4 to 8 μm, 2.0% by volume or less for a particle size of 16.0 μm or more, and a volume average particle size of the toner of 4 to 8 μm.
N / V = -0.32N + k N: the number% of toner particles having a particle size of 4 μm or less, where a positive number of 15 to 60 V: a particle size of 4 μm or less The carrier has a core material obtained by dispersing a magnetic material in a binder resin, and the surface of the core material is covered with a resin. And a resin that coats the surface of the core material is a vinyl copolymer having a hydroxyl value of 1 to 100 and a fluorine-containing resin (hereinafter referred to as “developer”). A.) or (2) the particle size distribution of the toner is 13 to 60% by number for a particle size of 4 μm or less, and 10 to 70% by number for a particle size of 4 to 8 μm; 2.0 volume for particle size of 0 μm or more % Or less, and the toner has a volume average particle diameter of 4 to 10 μm, and a group of toner particles of 4 μm or less has the following formula: N / V = −0.32N + k N: %: A positive number of 13 to 60 V: a volume% of toner particles having a particle size of 4 μm or less k: a positive number of 13 to 20 and the carrier disperses a magnetic substance in a binder resin. A magnetic material-dispersed carrier comprising a core material having a core material surface coated with a resin, wherein the resin coating the core material surface comprises 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, 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 (weight of the fluororesin: weight of the copolymer). : 95 to 95: 5 (hereinafter referred to as “developer B”), the spent resistance, impact resistance, resistance, toner, The present inventors have found that the stability of imparting charge to the toner is improved, and that the developer using the magnetic material-dispersed carrier and the small particle size toner has excellent developability and developer life, and the present invention has been completed.

Although the details of the improvement of the characteristics of the carrier are not clear, according to the observation of the surface of the carrier by a scanning electron microscope, the vinyl copolymer and the fluororesin used in the present invention show that the carrier is A state in which the surface of the core material was uniformly coated was observed.

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

On the other hand, when the coating is uneven,
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. It is considered that there is a problem that a charge-up phenomenon easily occurs in an environment or an image defect easily occurs due to a leak of a developing bias voltage.

It is also considered that by limiting the amount of fine powder of 4 μm or less when the particle size of the toner is reduced, it is possible to suppress the variation of each toner and satisfy the developer deterioration prevention and developability of the present invention. 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 a strong adhesive force take a larger share by the carrier, the developing device, and the like, and are considered to cause toner filming.

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

The hydroxyl group-containing vinyl resin used as the coating resin of 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. 2-hydroxyethyl acrylate as a vinyl monomer having a hydroxyl group,
2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 2-hydroxy-3-phenyloxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 2 methacrylic acid -Hydroxy-3-phenyloxypropyl and the like. These monomers have a copolymer having a hydroxyl value of 1 to 100 (K
OH mg / g), more preferably 5 to 70, even more preferably 10 to 50 (KOH mg / g).

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

Other vinyl monomers copolymerized with these hydroxyl group-containing vinyl monomers include styrene, α-methylstyrene, p-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 include pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, and vinyl monomers.

Among these other vinyl monomers, vinyl monomers having one vinyl group in one molecule are preferably styrene, styrene derivatives, methacrylates, acrylates, etc.
Alkyl esters of methacrylic acid or acrylic acid having two carbon atoms are preferred.

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

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

That is, styrene derivatives include styrene, o-methylstyrene, m-methylstyrene, p-
Methyl styrene, p-phenyl styrene, p-ethyl styrene, 2,4-dimethyl styrene, pn-butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, p- n-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-chlorostyrene, 3,4-dichlorostyrene, m-nitrostyrene, o-nitrostyrene, p-nitro Styrene, and the like.

The acrylates include, for example, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate,
Examples thereof include 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, and phenyl acrylate.

Examples of the methacrylates include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, and the like.
Isobutyl methacrylate, n-octyl methacrylate,
Examples include dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate.

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

Further, the weight average molecular weight of the copolymer used for the coating resin of the carrier core material of the developer B of the present invention is essential to be about 30,000 to 70000, 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 the impact resistance of the carrier cannot be obtained, and
If it is more than 000, the coatability of the carrier core becomes poor, and the strength of the carrier and the charge stability are lacking. More importantly, at this time, even if the weight average molecular weight falls within this range, the weight average molecular weight /
Unless the number average molecular weight is in the range of 2 to 10, the effect of the present invention cannot be obtained. If the weight average molecular weight / number average molecular weight is smaller 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 more than 10, the uniformity of the coating on the carrier core is deteriorated, and the carrier strength and the desired charge stability cannot be obtained.

The fluorine-containing resin used in combination with the coating resin of the carrier core material of the present invention includes halofluoropolymers such as polyvinyl fluoride, polyvinylidene fluoride, polytrifluoroethylene, and polytrifluorochloroethylene; 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 5:95 to 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 amount of exposure of the fluorine-containing resin in the uniform resin coating layer tends to be insufficient. On the other hand, when the content of the fluorine-containing resin exceeds 95% by weight, Since the amount of the vinyl-based resin having a hydroxyl group is reduced, the adhesion of the resin coating layer to the core material tends to decrease.

The mixing ratio of the fluorine-containing resin and the styrene-acrylic copolymer is also 5:95 by weight.
~ 95: 5 is preferred. When the content is within the above range, the desired charge stability can be obtained in both positive and negative polarity developers. However, when the content of the fluorine-containing resin is less than 5% by weight, a developer exhibiting positive charge characteristics is obtained. When the content of the fluororesin exceeds 95% by weight, the charge stability of the developer exhibiting the negative charging property is reduced, and the charge stability of the developer is reduced. , The uniform application to the core material becomes difficult.

The weight average molecular weight of the fluororesin 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.
When 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 which can be used as the coating resin of 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 the 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: 0.15% sample 0.4 ml injection As the binder resin used for the core material in the structure of the carrier of the present invention, all resins obtained by polymerizing a vinyl-based monomer can be mentioned. Examples of the vinyl monomer referred to herein include styrene, o-methylstyrene, m-
Methyl styrene, p-methyl styrene, p-phenyl styrene, p-ethyl styrene, 2,4-dimethyl styrene, pn-butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn- Octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, p-methoxy styrene, p-chlorostyrene, 3,4-dichlorostyrene, m-nitrostyrene, o-nitro Styrene, styrene derivatives such as p-nitrostyrene, etc., 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, and 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-acrylate
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 ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone; N-vinyl compounds such as N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone; Vinyl naphthalenes;
Acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide; acrolein; and the like;
Those polymerized using more than one kind 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, 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; ferrites, magnetite and hematite; and iron, cobalt and nickel. An alloy or a compound containing an element exhibiting magnetism may be used. The magnetic force of the magnetic fine particles according to the present invention at a magnetic field of 10 K Oersted is 60 emu / g.
That is all. If it is less than 60 emu / g, the carrier is likely to adhere to the photoreceptor even if the content of the magnetic fine particles is increased. The magnetic force of the magnetic material of the present invention was measured by VSM manufactured by Toei Kogyo.

The magnetic fine particles preferably 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 specific resistance of the magnetic fine particles according to the present invention must be 10 ⁹ Ω · cm or less, and the content relative 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.

Therefore, the magnetic material-dispersed carrier of the present invention has one important characteristic 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 from 10 to
It can be preferably used in the range of 60 μm. 10μ
If it is smaller than m, the carrier tends to adhere to the photoreceptor, and if it exceeds 60 μm, the share of the developer in the developing device becomes large, and the deterioration of the developer, especially the peeling of external additives of toner particles, the shape This causes a change and causes image deterioration. Furthermore, when the particle size is large, the specific surface area is small, so that the amount of toner that can be retained when constituting the developer is small, and an image lacking in definition is obtained. In addition, the particle diameter of the carrier core of the present invention is randomly determined by an optical microscope or a scanning electron microscope.
One or more pieces were extracted, and the maximum chord length in the horizontal direction was measured as the carrier particle size.

The true specific gravity of the carrier of the present invention is 1.5.
A range of -5.0 is preferred. More preferably 1.5 to
4.5. If the true specific gravity exceeds 5.0, it is not preferable from the viewpoint of deterioration of the developer due to a large share of the developer in the developing device. 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 true denser (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 appropriate. 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 photoreceptor in the developing area, and a good image cannot be obtained. On the other hand, if 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 loss, 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. The} thickness d is about 1 mm, the load on the upper electrode is 275 g, and the applied voltage is 100 V. Here, since the carrier is a powder, the specific resistance may change depending on the filling rate, and thus care must be taken.

In order to keep the specific resistance of the carrier of the present invention within the above range, the specific resistance can be easily adjusted by coating a low-resistance core material containing magnetic fine particles with the resin of the present invention. Controllability is a feature of the present invention. 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 almost the same by uniform resin coating in order to obtain good developability, and this is a feature of the present invention.

In order for the resistance of each part of the core material surface to be uniform, it is preferable that the magnetic fine particles are uniformly dispersed in each part of the core material surface. 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 was such that the magnetic fine particles were uniformly dispersed at each site on the surface of the core material, and the surface of the magnetic fine particles was The present inventors have found that at least a part thereof is substantially exposed on the surface of the core material.

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.

As means for achieving the above-mentioned sphericity of 2 or less in the carrier of the present invention, there are a method of heating the core material and thermally melting the surface to make the surface spherical, or a method of mechanically making the surface spherical. 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 preparing a core material and applying a resin coating.

First, as a method for manufacturing a core material, the binder resin and the magnetic fine particles are mixed at a desired ratio, and for example,
Kneading at an appropriate temperature using a hot-melt mixing device such as a three-roll or extruder, cooling, and then pulverizing and classifying, or dissolving the binder resin in a soluble solvent, After mixing the fine particles to form a slurry, granulating and drying using a spray drier, or magnetic fine particles, a polymerization initiator, a suspension stabilizer, etc. in a monomer solution of the binder resin for the core material. There is a suspension polymerization method of adding, dispersing, and then granulating and polymerizing. 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 to form at least one surface of the magnetic fine particles. Since the portion can be controlled 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 effects of the present invention.

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 coating and drying are simultaneously advanced in such a manner that the conditions are sufficiently controlled and the core material constantly flows. Note that 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 (% by weight) (X: true specific gravity) More preferably, 1 / X ≦ resin coating amount ≦ 25 / X (% by weight).

When the amount of the coating resin is less than ＸX% by weight, it is difficult to uniformly coat the surface of the core material, and even if the coating can be performed, 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 could not be coated is generated by being liberated alone and adhered to the photoreceptor, which may cause image deterioration.

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

For example, styrene such as polystyrene, poly-p-chlorostyrene and polyvinyltoluene and a homopolymer of a substituted product thereof; 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, aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; for example, ethylene glycol diacrylate and ethylene glycol diacrylate. Methacrylate, 1,3
A double bond such as phthalane 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.

In the toner according to the present invention, charge controllability is 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,
A quaternary ammonium salt such as tetrabutylammonium tetrafluoroborate; dibutyltin oxide; a diorganotin oxide such as dioctyltin oxide or dicyclohexyltin oxide; be able to.

As the negative charge controlling agent which can be used in the present invention, for example, organometallic complexes and chelate compounds are effective. Examples thereof are aluminum acetylacetonate, iron (II) acetylacetonate, 3,5- 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 action 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. 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, Hanza 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.
In order to improve the permeability of the HP film, the content is preferably 12 parts by weight or less, more preferably 0.5 to 9 parts by weight.

The toner according to the present invention has a low molecular weight polyethylene, a low molecular weight polypropylene, a 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.

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

Although fine particles of alumina and titanium oxide can be obtained relatively easily by a gas phase method, there are no particular restrictions on the production method. However, particles having a plate-like or needle-like shape are not preferred.

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

When the hydrophobic silica has a degree of hydrophobicity of at least a certain level, the fluidity-imparting effect is large and good, but there is no particular limitation when used in the present invention.

The application amount of the fluidity improver 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 the amount is less than 0.01 part by weight, there is no effect in improving the fluidity. If the amount exceeds 10 parts by weight, fogging and bleeding of characters and scattering inside the machine are promoted. In particular, in the case of a 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, if necessary, a pigment or dye as a colorant, a charge control agent, and other additives are mixed with a mixer such as a ball mill. After thoroughly mixing, using a hot kneader such as a heating roll, kneader, or extruder, disperse or disperse the pigment or dye in the resin mixed with each other by melting, kneading, and kneading, and cooling. 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 mixed using a mixer such as a Henschel mixer. By mixing the above, a toner can be obtained.

Next, regarding the particle size distribution of the toner used in the present invention, in the case of the developer A, the non-magnetic toner particles having a particle size of 4 μm or less are preferably 15 to 60% by number of the total number of particles. Is preferably 20 to 60% by number. When the number of non-magnetic toner particles having a particle size of 4 μm or less is less than 15% by number,
The non-magnetic toner particles that are effective for high image quality are small, and in particular, as the toner is used by continuing copy or printout, the effective non-magnetic toner particle component is reduced, and the non-magnetic toner of the present invention is reduced. The balance of the particle size distribution deteriorates, and the image quality gradually decreases. 60
If the number is more than a few percent, the non-magnetic toner particles tend to aggregate with each other, resulting in a toner mass larger than the original particle size, resulting in rough image quality, reduced resolution, and an edge portion of the latent image. The density difference between the image and the inside becomes large, and the image tends to be slightly hollow.

In the case of the developer B, the nonmagnetic 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 more preferably 20% by number. ~ 60 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 having a size of 4 to 8 μm are preferably 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% by number, in particular, 60% by number
When the ratio exceeds, the image quality is deteriorated, and unnecessary development (that is, excessive amount of toner) occurs, which leads to 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 particles having a particle size of 4 μm or less, and 13 ≦
Indicates a positive number in the range of k ≦ 20. Preferably 13.5 ≦ k
<19.5. As indicated above, 15 ≦ N ≦ 6
0, preferably 20 ≦ N ≦ 60.

When k <13, the number of non-magnetic toner particles having a particle diameter of 4.0 μm or less is small, and the image density, resolution, and sharpness are poor. Conventionally, the moderate presence of fine non-magnetic toner particles, which was often considered unnecessary,
It achieves the closest packing of toner and contributes to forming a uniform image without roughness. In particular, by uniformly filling the fine lines and the outline of the image, the sharpness is further enhanced visually. When k <13, these characteristics 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 to satisfy the condition of k <13, which is disadvantageous in terms of yield and toner cost. Becomes When k> 20, the image density tends to be reduced during repeated copying due to the presence of unnecessarily fine powder. Such a phenomenon occurs because excess fine non-magnetic toner particles having an excessive charge are charged and adhered to the developing sleeve or / and the carrier, and the normal non-magnetic toner is carried on the developing sleeve or the carrier and charged. It is thought to be caused by inhibiting the application.

In the developer B, particles having a size of 4 to 8 μm are contained in an amount of 10 to 70% by number, preferably 10 to 50% by number, and 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, indicating a positive number in the range of 13 ≦ k ≦ 20. Preferably, 13.5 ≦ k ≦ 19.5. As indicated above, 13 ≦ N ≦ 60, preferably 15 ≦ N ≦
60, more preferably 20 ≦ N ≦ 60.

The significance and reason of these numerical limitations are as follows.
Is the same as

The amount of the non-magnetic toner particles having a particle diameter of 16.0 μm or more of 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 larger than the volume%, not only hindrance in thin line reproduction is hindered, but also coarse toner particles of 16.0 μm or more protrude from the thin layer surface of the toner particles developed on the photoreceptor during transfer. The delicate state of contact between the photoreceptor and the transfer paper via the toner layer is made irregular, causing fluctuations in the transfer conditions and causing poor transfer images.

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

As a measuring device, Coulter Counter T
A-II type (manufactured by Coulter) was used. As the electrolyte, a 1% aqueous NaCl solution was prepared using primary sodium chloride. As the measuring method, 100 to 150 ml of the electrolytic aqueous solution is used.
0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant therein, and 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample was suspended was subjected to dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and the above-mentioned Coulter counter TAII type was used as an aperture for 10 minutes.
Using a 0μ aperture, 2 to 40μ based on the number
The particle size distribution of the particles was measured, and then the values according to the present invention were determined.

[0089]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments 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 composition
All parts and parts are by weight and parts by weight.

Example 1 Styrene 22.2% 2-ethylhexyl acrylate 11.1% Reduced iron (particle size 0.32 μm) 66.7% The above materials were heated to 70 ° C. in a container and dissolved. This was a monomer mixture. While maintaining the temperature at 70 ° C., the initiator azobisisonitrile was added and dissolved to prepare a monomer composition. This was put into a 2 liter flask containing 1.2 liter of a 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 ℃,
Polymerization was performed for 10 hours. 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 surface of the obtained magnetic material-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 value (KOH mg / g) = 30 weight average molecular weight = 52,000) Vinylidene-tetrafluoroethylene copolymer 45% (weight ratio of monomer composition = 75: 25 weight average molecular weight = 210,000) The resin coating amount of the above copolymer is 0.8% from the above formula.
Was dissolved in a mixed solvent of acetone and methyl ethyl ketone (mixing weight ratio = 1: 1) to prepare a carrier coating solution. The carrier coating solution was applied to the above-mentioned core material while performing application and drying simultaneously using a coating machine (a Spira coater manufactured by Okada Industry Co., Ltd.). The obtained magnetic material-dispersed resin carrier after application was dried at a temperature of 90 ° C. for 2 hours to remove the solvent, thereby obtaining a resin-coated magnetic material-dispersed resin carrier in which the surfaces of the magnetic material-dispersed fine particles were covered with a resin coating layer. Observation of the obtained resin-coated magnetic material dispersed resin carrier by an electron microscope revealed that the core material was uniformly coated with the resin, and that the magnetic material particles were substantially uniformly exposed on the coated surface. It was confirmed that.

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

On the other hand, 100 parts of a polyester resin obtained by condensing propoxylated bisphenol and fumaric acid 100 parts Phthalocyanine pigment 5 parts Chromium complex salt of di-tert-butylsalicylic acid 4 parts After the above materials were sufficiently premixed with a Henschel mixer, The resulting mixture was melt-kneaded once 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 material is classified to obtain a negatively-chargeable cyan powder (toner) having a weight average diameter of 8.9 μm.
I got The particle size distribution of the cyan toner was N = 27.2% by number and V = 5.8% by volume for a particle size of 4 μm or less, and 0% by volume for a particle size of 16.0 μm or more. The N and N / V of the toner fall within the specified range of the present invention as shown in FIG.

100 parts of the above 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 surface of toner particles.

This cyan toner and the above resin carrier were mixed in a temperature / humidity environment of N / N (23 ° C./60% RH) so as to have a toner concentration of 4% to obtain a developer. 100 g of the obtained developer was placed 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 agent, 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 under a temperature / humidity environment of L / L (15 ° C./10% RH) so that the toner concentration was 4%. Under the same environment, the full color laser copier CLC-
500 developing device and driven by an external motor (peripheral speed 3
(00 rpm) for 30 minutes. After this, C
Using LC-500, 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 and the line image was good.

Further, a durability test was conducted on 10,000 sheets. As a result, 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,
In the same manner as in Example 1, the coating resin used in Example 1 was coated to a coating amount of 0.8%. This carrier and a weight average diameter of 5.0 μm, and N = 4 μm or less
Example 1 where 62.2% by number and V = 28.7% by volume
A cyan toner having the same composition as that of
Under a (15 ° C./10% RH) environment, the mixture was adjusted to a toner concentration of 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, a durability test was performed on 10,000 sheets. As a result, roughness was observed in the halftone portion, and the line image was hollowed out and the image density was lowered.

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

(Comparative Example 2) The coating resin used in Example 1 was used in the same manner as in Example 1 except that the core material used in Example 1 was replaced with 46 μm reduced iron particles. Coating was performed. The obtained carrier and the same toner as 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 external additive was buried on the toner surface. In addition, as a result of the image output test, the initial image was good in halftone and line image, but as a result of the 10,000 image endurance image output test, halftone roughness and line image disorder were generated. Was.

(Comparative Example 3) Instead of the carrier coating solution used in Example 1, the core material used in Example 1 was replaced with a vinylidene fluoride-tetrafluoroethylene copolymer (monomer composition weight ratio = 75:25 weight average) Using only (molecular weight = 210,000), a carrier coating solution was prepared by dissolving 10% in a mixed solvent of acetone and methyl ethyl ketone so that the resin coating amount was 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 was coated with a resin coating layer. Tables 1 and 2 show the physical properties of this carrier.

Microscopic observation revealed that the core material was not uniformly coated. A test similar to that of Example 1 was performed using this carrier.

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

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

The toner and the carrier are mixed at a toner concentration of 3.
A developer was prepared by mixing so as to have a concentration of 5%, and a test was carried out in the same manner as in Example 1 using a Canon copier NP4835. A uniform image was obtained.

(Example 3) Styrene-2-ethylhexyl acrylate 50% (55/45) copolymer Reduced iron 50% After sufficiently premixing the above materials with a Henschel mixer, at least twice using a three-roll mill After melt-kneading and cooling, the mixture was coarsely pulverized using a hammer mill to a particle size of about 2 mm. Next, it was pulverized with an air jet pulverizer to a particle size of about 50 μm. Further, the obtained finely pulverized product was put into a Mechanomill MM-10 (manufactured by Okada Seiko) and mechanically sphericalized.

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

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

Tables 1 and 2 show the physical properties of this carrier. Further, the same test as in Example 1 was performed on this carrier.

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

Example 4 Polyester resin obtained by condensing 40% (50/40/10) of ethoxylated bisphenol-fumaric acid-trimellitic acid 60% magnetite (particle diameter 0.26 μm) 60% In the same manner as in Example 2, spherical magnetic material-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 so that the resin coating amount was 1.2%. The resin fine particles were coated in the same manner as in Example 1 by using the carrier coating solution in which the carrier was dissolved in a% to obtain a magnetic substance-dispersed resin carrier. Tables 1 and 2 show the physical properties of the obtained carrier. In addition, when a test similar to that in Example 1 was performed, good results were obtained as in Example 1.

(Example 5) Phenol 10.0% Formaldehyde (Formaldehyde about 37% 5.0% Methanol about 10% The balance is water) Magnetite (Particle diameter 0.25 μm) 85.0% The above material was used as a basic catalyst. Using ammonia and calcium fluoride as a polymerization stabilizer, the mixture was gradually heated to a temperature of 80 ° C. while stirring in an aqueous phase, and polymerization was performed for 2 hours. The particle diameter of the obtained magnetic material-dispersed resin particles was 42 μm. The resin particles were coated in the same manner as in Example 3 using a methyl ethyl ketone solution in which the coating resin used in Example 3 was dissolved 10% so that the resin coating amount was 1.0%. Tables 1 and 2 show the physical properties of the obtained resin-coated carrier. In addition, a test similar to that of Example 1 was performed using this carrier, and good results similar to those of Example 1 were 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 were heated to a temperature of 70 ° C in a container, dissolved and monomers were dissolved. A mixture was obtained. While maintaining the temperature at 70 ° C., the initiator azobisisonitrile was added and dissolved to prepare a monomer composition. This was put into a 2 liter flask containing 1.2 liter of a 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 material-dispersed styrene acrylic slurry was washed and filtered. This was dried to obtain magnetic material-dispersed resin particles.

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

Styrene-isobutyl methacrylate copolymer 50% (weight ratio of monomer composition = 45: 65 Mw 39000 Mw / Mn = 2.7) Vinylidene fluoride-tetrafluoroethylene copolymer 50% (weight ratio of monomer composition = (75:25 weight average molecular weight = 210,000) The resin coating amount of the above copolymer is 0.8% from the above formula.
Was dissolved in a mixed solvent of acetone and methyl ethyl ketone (mixing weight ratio = 1: 1) to prepare a carrier coating solution. The carrier coating solution was applied to the core material while performing application and drying simultaneously with a coating machine (a Spira coater manufactured by Okada Kogyo Co., Ltd.). The coated magnetic substance-dispersed resin carrier thus obtained 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 substance-dispersed fine particles with a resin coating layer. A body-dispersed resin carrier was obtained. Observation of the obtained resin-coated magnetic material-dispersed resin carrier by an electron microscope revealed that the core material was uniformly coated with the resin and that the magnetic particles were substantially uniformly exposed on the coated surface. It was confirmed that.

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

On the other hand, 100 parts of a polyester resin obtained by condensing propoxylated bisphenol and fumaric acid 100 parts Phthalocyanine pigment 5 parts Chromium complex of di-tert-butylsalicylic acid 4 parts After the above materials were sufficiently premixed with a Henschel mixer, The resulting mixture was melt-kneaded once 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 is classified to obtain a negatively chargeable cyan powder (toner) having a weight average diameter of 7.6 μm.
I got The particle size distribution of the cyan toner was N = 20.5% by number, V = 2.6% by volume for a particle size of 4 μm or less, and 0% by volume for a particle size of 16.0 μm or more. The N and N / V of the toner fall within the specified range of the present invention as shown in FIG.

100 parts of the above 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 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 4% to obtain a developer. 100 g of the obtained developer was placed 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 agent, and no filming by the toner were observed. Also, no detachment or burial of the external additive of the toner was observed.

The 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) to a toner concentration of 4%. Under the same environment, the full color laser copier CLC-
500 developing device and driven by an external motor (peripheral speed 3
(00 rpm) for 30 minutes. After this, C
Using LC-500, 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 and the line image was good.

Further, when a durability test was performed on 10,000 sheets, the solid image density, the halftone portion, and the reproducibility of the line image were good.

(Comparative Example 4) A carrier similar to that of Example 6 was used. 5. This carrier and a weight average diameter of 6.
3 μm, N = 75.0 for particle size of 4 μm or less
A cyan toner having the same composition as that of Example 6 in which the number% and V = 22.3% by volume was L / L (15 ° C./1
Under a 0% RH environment, the mixture was adjusted to a toner concentration of 4% to obtain a developer. Using this, the same measurement and test as in Example 6 were performed. As a result of the shaking test, aggregation of the toner was observed. Further, as a result of the image output test, in the initial image and the durability test of 10,000 sheets, roughness of the halftone portion was observed, and the line image was hollowed out and the image density was lowered.

Note that N and N / V of the toner deviate from the specified regions in the present invention shown in FIG.

(Comparative Example 5) The coating resin used in Example 6 was used in the same manner as in Example 6 except that the core material used in Example 6 was replaced with 45 μm reduced iron particles. Coating was performed. 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 measurement and test as in Example 6 were performed.

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, the initial image was good in halftone and line image, but as a result of the 10,000 image endurance image output test, halftone roughness and line image disorder were generated. Was.

(Comparative Example 6) A vinylidene fluoride-tetrafluoroethylene copolymer (monomer composition weight ratio = 60:40 weight average) was used in place of the carrier coating solution used in Example 6 for the core material used in Example 6. (Molecular weight = 220,000) alone, and 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 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 was covered with a resin coating layer. Tables 4 and 5 show the physical properties of this carrier.

According to the microscope, it was found that the core material was not uniformly coated. A test similar to that of Example 6 was performed using this carrier.

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

(Embodiment 7) As a carrier, Embodiment 6
The same one as described above was used. Further, as the toner, 100 parts of styrene-2-ethylhexyl acrylate-dimethylaminoethyl methacrylate copolymer (monomer composition weight ratio = 80/15/5) Copper phthalocyanine 4 parts Low molecular weight polypropylene 5 parts Weight average diameter 5.2μ
m, particle size of 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 defined range 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 an amino-modified silicone oil were mixed with a Henschel mixer to obtain a positively chargeable blue toner.

The toner and the carrier are mixed at 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 copier NP4835. A uniform image was obtained.

(Example 8) Copolymer of styrene-2-ethylhexyl acrylate 50% (85/15) Reduced iron 50% The above materials were sufficiently premixed with a Henschel mixer, and then at least twice with a three-roll mill. After melt-kneading and cooling, the mixture was coarsely pulverized using a hammer mill to a particle size of about 2 mm. Next, it was pulverized with an air jet pulverizer to a particle size of about 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 spheroidized finely pulverized particles were further classified to obtain magnetically 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 material-dispersed resin particles in the same manner as in Example 6 to obtain a resin-coated carrier.

Tables 4 and 5 show the physical properties of this carrier. Further, this carrier was subjected to the same test 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 endurance image output tests.

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

The surface of the obtained magnetic material-dispersed resin particles was coated with the following coating resin 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 in which 10% was dissolved in a methyl ethyl ketone solution so that the resin coating amount was 1.2%. A magnetic material-dispersed resin carrier was obtained. Tables 4 and 5 show the physical properties of the obtained carrier. When a test similar to that of 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 balance is water) Magnetite (particle diameter: 0.25 μm) 85.0% Using the above material as a basic catalyst Using ammonia and calcium fluoride as a polymerization stabilizer, the mixture was gradually heated to a temperature of 80 ° C. while stirring in an aqueous phase, and polymerization was performed for 2 hours. The particle diameter 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 coating resin used in Example 3 was dissolved 10% so that the resin coating amount was 0.9%. Table 6 shows the physical properties of the obtained resin-coated carrier. When a test similar to that of Example 6 was performed using this carrier, good results similar to those of Example 6 were obtained.

[0150]

[Table 4]

[0151]

[Table 5]

[0152]

[Table 6]

[0153]

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 photoreceptor (6) Control of carrier resistance (7) Stability of toner chargeability can be sufficiently satisfied, especially development using small particle size toner In the developer, 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 the 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]

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

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 9/08-9/113

Claims (12)

(57) [Claims] 1. Having at least a toner and a carrier
Electrophotographic developer,  When the particle size distribution of the toner is 4 μm or less,
5 to 60% by number, and 10 to 10% for a particle size of 4 to 8 μm.
About 60% by number and a particle size of 16.0 μm or more
2.0% by volume or less and a weight average particle size of the toner.
The toner particles having a diameter of 4 to 10 μm and a particle size of 4 μm or less
N / V = -0.32N + k N: the number% of toner particles having a particle size of 4 μm or less, where
V: a volume% of toner particles having a particle diameter of 4 μm or less, and k: a positive number of 13 to 20, and The carrier is bound tree
A core material obtained by dispersing a magnetic substance in fat, and the core material
A magnetic material-dispersed carrier whose surface is coated with resin
The resin coating the surface of the core material has a hydroxyl value
Vinyl copolymer having 1 to 100 and fluorine-containing resin
Mixture ofA developer for electrophotography, which is: 2. The true specific gravity of the carrier is 1.5 to 5.0.
The electrophotographic developer according to claim 1, wherein: 3. The electrophotographic development according to claim 1, wherein the magnetic force of the magnetic substance dispersed in the core material is 60 emu / g or more under a magnetic field of 10 K Oersted. Agent. 4. The carrier has a particle size of 10 μm to 60 μm.
The electrophotographic developer according to any one of claims 1 to 3 , wherein 5. A carrier having a specific resistance of 10 ⁷ Ω · cm or more.
5. The resistance is 10 ¹⁴ Ω · cm.
The electrophotographic developer according to any one of the above. 6. A toner having a particle size distribution of 4 μm or less.
The lower toner particle group 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
Positive number between 17 and 60 V:% by volume of toner particles having a particle size of 4 μm or less k: a positive number from 13.5 to 19.5 The method according to any one of claims 1 to 5, wherein
The developer for electrophotography according to the above. 7. Having at least a toner and a carrier
Electrophotographic developer,  When the particle size distribution of the toner is 4 μm or less,
3 to 60% by number, and 10% for a particle size of 4 to 8 μm.
About 70% by number and a particle size of 16.0 μm or more
2.0% by volume or less and a weight average particle size of the toner.
The toner particles having a diameter of 4 to 10 μm and a particle size of 4 μm or less
N / V = -0.32N + k N: the number% of toner particles having a particle size of 4 μm or less, where
V: a volume% of toner particles having a particle diameter of 4 μm or less, and k: a positive number of 13 to 20, and The carrier is bound tree
A core material obtained by dispersing a magnetic substance in fat, and the core material
A magnetic material-dispersed carrier whose surface is coated with resin
And the resin coating the core material surface is styrene-acrylic.
Copolymer and fluorine-containing resinIs a mixture ofAnd
A in the styrene-acrylic copolymer
A monomer ratio of the krill component is 30 to 90% by weight,
And a weight average molecular weight of about 30,000 to 70000
Having a cloth, and weight average molecular weight / number average molecular weight
2.0 to 10, and the styrene-acrylic copolymer
The mixing ratio of the fluororesin to the polymer is the weight ratio
(Weight of the fluorine-containing resin: weight of the copolymer) and 5:95
~ 95: 5, an electrophotographic developer. 8. The carrier has a true specific gravity of 1.5 to 5.0.
The electrophotographic developer according to claim 7 , wherein 9. The magnetic force of the magnetic material dispersed in the core material, the electrophotographic developing as recited in claim 7 or 8, characterized in that under 60 emu / g or more magnetic field 10K oersted Agent. 10. The carrier has a particle size of 10 μm to 60 μm.
The developer for electrophotography according to any one of claims 7 to 9, characterized in that the m. 11. The carrier has a specific resistance of 10 ⁷ Ω · cm.
Claim characterized in that it is a ~10 ¹⁴ Ω · cm 7 to
10. The developer for electrophotography according to any one of 10 . 12. A toner having a particle size distribution of 4 μm
The following toner particle group 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
Positive number between 17 and 60 V:% by volume of toner particles having a particle size of 4 μm or less k: a positive number from 13.5 to 19.5 12. The method according to claim 7, wherein
3. The developer for electrophotography according to item 1.